CA2082322A1 - Meltblown fibers prepared from poly(vinyl chloride) compositions - Google Patents

Abstract

Abstract of the Disclosure Meltblown fibers and webs are formed by meltblowing a plasticized poly(vinyl chloride) composition which contains from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, such composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load.

Description

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The present invention relates to meltblown fibers prepared from a poly(vinyl chloride) composition. More particularly, the present invention relates to the formation of meltblown fibers from a plasticized poly(vinyl chloride) composition.
It generally is recognized that essentially any thermo-plastic material which has an acceptably low melt viscosity at suitable processing temperatures can be meltblown to form fibers or a nonwoven web. The extruded filaments should solidify sufficiently before landing on the forming or collecting screen or wire. See, by way of example only, "Manufacture of Superfine Organic Fibers," Interim Report, Naval Research Laboratory, Bureau No. S-1636, U. S. Depart-ment of Commerce, Office of Technical Services Report No.
15 PBl11437, NRL-4364, Washington, D. C., April 15, 1954; V.
A. Wente, "Superfine Thermoplastic Fibers," Ind. Enq. Chem., 48, 1342 (19S6); and R. R. Buntin and D. T. Lohkamp, "Melt Blowing - A One-Step Web Process for New Nonwoven Products,"
J. Tech. Assoc. Pulp Paper Ind., 56, 74 tl973). See also 20 U. S. Patent Nos. 3,379,811 to Hartmann et al.; 3,502,763 to Hartmann; 3,755,527 to Keller et al.; 3,849,241 to Butin et al.; 3,978,185 to Buntin et al.; and 4,434,205 Fujii et al.
It also is generally accepted by those experienced in meltblowing processes that poly(vinyl chloride) cannot be meltblown because the polymer degrades at a temperature well below that necessary to achieve a sufficiently low melt viscosity (see the first two references cited above).
However, U.S. Patent No. 3,673,167 to Ledous et al. teaches ' 2~8~22 that fibers can be prepared from poly(vinyl chloride) by a melt spinning process in which the heating, shaping (extrud~
ing), drawing, and cooling of the fibers is limited to a time of the order of a few seconds to tens of seconds.
Although nonwoven poly(vinyl chloride) materials are known, they typically are prepared from fibers which are either dry-spun or wet-spun. In either case, the fibers are formed by extruding a solution of the polymer from a die to form fine streams of fluid. With dry spinning, the amount of solvent is relatively low, so that the solvent evaporates quickly, thereby forming a fiber from each fluid stream.
Wet-spinning is similar to dry spinning, except that the solvent level is higher and the fluid streams are extruded into water which extracts the solvent. See, by way of illustration only, H. F. Mark, S. M. Atlas, and E. Cernia, Editors, "Man-Made Fibers," Vol. 3, Interscience Publishers, New York, 1968, pp. 330-335 and 350-352; R. W. Moncrieff, "Man-Made Fibres," 6th Ed., Newnes-Butterworths, London, 1975, pp. 496-503 and 521-532; and U.S. Patent Nos. 2,988,469 to Watson, and 4,508,778 and 4,707,319 to Achard et al.
It should be noted that plasticized poly(vinyl chloride) compositions and blends of poly(vinyl chloride) with other polymers are known. Some representative references are described in the paragraphs below.
U. S. Patent No. 4,489,193 to Goswami describes a blend of an ethylene/carbon monoxide copolymer with an internally plasticized vinyl chloride copolymer, which blend is used to prepare films having improved low temperature flexibility and color stability. The internally plasticized vinyl chloride copolymer is formed by polymerizing vinyl chloride in the presence of 10 to 50 percent by weight of at least one comonomer which functions as an internal plasticizer. Such comonomers include the alkyl acrylates and methacrylates containing up to about 18 Garbon atoms in the alkyl moieties, the vinyl esters of carboxylic acids, and ethylenically ` unsaturated dicarboxylic acids, the anhydrides thereof, and ";
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mono- and dialkyl esters thereof, in which the ester moieties contain up to about 20 carbon atoms. The blend generally comprises from about 40 to about 60 percent by weight of the internally plasticized vinyl chloride copolymer. The blend was used to form a film by calendering.
U. S. Patent No. 4,556,589 to Neumann et al. discloses compositions consisting of from about 40 to 75 percent by weight of poly(~inyl chloride) and from about 25 to about 60 percent by weight of a plasticizer. The compositions are employed to coat one or both sides of a fabric or other sheet-like textile material such as knitted fabrics and nonwovens, usually in at least two and not more than six layers. The composition is applied to the fabric from a solution or a dispersion.
A thermoplastic, melt-processible, elastomeric compo-sition based on partially crosslinked compatible blends of an ethylene copolymer and a vinyl or vinylidene halide polymer is described in U.S. Patent No. 4,613,533 to Loomis et al.
The latter polymer comprises from 5 to 75 percent by weight of the composition and can be poly(vinyl chloride). The critical aspect of the composition is stated to be the crosslinking of the ethylene copolymer by any suitable means, such as electron beam irradiation, gamma irradiation, and free radical curatives such as peroxides. Crosslinking can be accomplished either before or after blending with the vinyl or vinylidene polymer. The composition is stated to be melt processable in conventional plastic processing equipment.
According to U.S. Patent No. 4,659,766 to Falk et al., compositions comprising high rubber content ABS graft copolymers, poly~vinyl chloride), and plasticizers for poly(vinyl chloride) are useful as thermoplastic elastomers which may be melt-processed in conventional molding and extrusion equipment. Such compositions are stated to comprise from 70 to 30 parts by weight of the graft copolymer, from 30 to 70 parts by weight of the poly(~inyl chloride), and from 45 to 65 parts by weight of a poly(vinyl chloride) plasti-~"' ;:

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cizer. Typical applications of the compositions include shoesoling, extruded hose and tubing, wire and cable insulation, flexible cord, automotive parts, and the like.
U.S. Patent No. 4,668,740 to Okano discloses a vinyl chloride polymer resin composition which is stated to have excellent processability and flowability. The composition is comprised of (a) 100 parts by weight of a vinyl chloride polymer composition comprising 5 to 100 weight percent of a vinyl chloride polymer having an average degree of poly-merization of 300 to 700 and 95 to 0 percent by weight of a vinyl chloride polymer having an average molecular weight higher than 700, and (b) 0.1 to 30 parts by weight of a methyl methacrylate polymer comprised of at least 40 percent by weight of methyl methacrylate and having a reduced viscosity ; 15 of 0.1 to 2 l/g. $he composition is stated to be useful for the production of films, sheets, and plates by the process including vacuum forming, large-size injection molded articles for which a high flowability is required, or low-expanded thick extrudates by calendering.
U.S. Patent No. 4,668,741 to Memering describes a rigid vinyl polymer composition having incorporated therein 1 to 5 parts of an ethylene-vinyl acetate copolymer per 100 parts of vinyl polymer. The vinyl polymer is any homopolymer or copolymer of a vinyl monomer. The most preferred vinyl polymer is poly(vinyl chloride). Other components are included in the composition, such as a heat stabilizer and impact modifier. Optional ingredients include a lubricant and a pigment or colorant. The compositions apparently are useful in molding processes.
U.S. Patent No. 4,681,916 to Wu et al. discloses poly(vinyl chloride) compositions comprising 50 to 98 parts by weight of a vinyl chloride polymer having an inherent viscosity of at least 0.4 and 50 to 2 parts by weight of an : addition terpolymer containing acrylonitrile, indene, and a specified third monomer. The compositions are useful for molding rigid articles such as pipe and bottles.

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Similar poly(vinyl chloride) compositions are disclosed in U.S. Patent No. 4,681,917 to Li et al. These compositions comprise 50 to 98 parts by weight of a vinyl chloride polymer having an inherent viscosity of at least 0.4 and 50 to 2 parts by weight of an addition copolymer containing indene and one comonomer selected from acrylonitrile, methyl methacrylate, and methacrylonitrile. The compositions are useful as molding compositions.
Miscible blends of a polycarbonate with a vinyl chloride derived polymer are described in U.S. Patent No. 4,698,390 to Robeson et al. The polycarbonate concentration in the blend can vary from about 5 to about 95 percent by weight, but most - preferably will vary from about 40 to about 60 percent by weight. The blends apparently are useful as molding composi-tions.
U.S. Patent No. 4,740,545 to Ohachi describes a poly-(vinyl chloride) composition which comprises: (1) 100 parts by weight of poly(vinyl chloride), (2) 0.1 to 50 parts by weight of an unsaturated aliphatic dicarboxylic dialkyl ester, and (3) 0 to 200 parts by weight of a plasticizer which is not the second component. The composition is used to make molded parts for medical instruments. See also U.S. Patent No.
4,698,382 to McClure et al. which discloses a plasticized poly(vinyl fluoride).
The use of a high boiling plasticizer as a melt depres-sant to enable the production of filaments by spray spinning from materials which are normally difficult to melt, such as ; cellulose acetate, has been mentioned. See, e.g., U.S. Patent Nos. 3,543,332 to Wagner et al. and 3,634,573 to Wagner et al.
Finally, several references are included for the sake of completeness as being of interest. These references are described briefly below.
U.S. Patent No. 4,181,762 to Benedyk describes fibers, yarns and fabrics of low modulus polymer. While an ethylene-vinyl acetate copolymer is stated to be best, other suitable materialz allegedly include a plasticized polyvinyl chloride.

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20~322 The fibers are prepared by extruding molten polymer through a spinnerette plate. The resulting molten strands are passed through a water bath, drawn, and wrapped on a spool. All of the examples employed an ethylene-vinyl acetate copolymer.
Laminates comprising filled polyolefins and a thermoplas-tic decorative layer are described in U.S. Patent No.
4,262,051. The two layers are separated by an adhesion-providing layer comprising a fiber-blend web or fabric containing two or more fusible types of fibers, one of which types welds to one of the outer layers to give a good bond, ; and another type welds to the other outer layer. The decorative layer typically is a polyvinyl chloride sheet, preferably a foamed, plasticized polyvinyl chloride sheet.
The adhesion-providing layer preferably is composed of polyolefin fibers and polyvinyl chloride fibers. Such layer in general is prepared from staple fibers.
U.S. Patent No. 4,324,824 to Narens et al. relates to a tufted pile floor covering. The floor covering has a flexible polymeric base, or secondary backing, and a fabric supported piling of flexible polymer coated threads which are mechani-cally bound by the flexible polymeric base. A preferred polymer for coating the threads is poly(vinyl alcohol).
U.S. Patent No. 4,590,112 to Plumridge et al. relates to multi-layer adhesive articles. The article includes a layer of polished, highly plasticized polyvinyl chloride material and a padded layer. Other polyvinyl alcohol layers can be present, if desired.
It is important to keep in mind that the thermal ~instability of poly(vinyl chloride) is well known. Indeed, ; 30 only one report of an attempt to meltblow poly(vinyl chlor-ide) is known, and that one resulted in failure [V. A. Wente, "Superfine Thermoplastic Fibers," Ind. ~aq. Chem., 48, 1342 (1956), su~ra].
Simply stated, the problem is this: poly(vinyl chloride) thermally decomposes at a temperature of about 200-C, with one of the degradation products being hydrogen chloride. At ,~:

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lower temperatures, however, the melt viscosity of the poly(vinyl chloride) is too high to permit meltblowing. The polymer can be employed in molding and extrusion processes, though, because such processes operate with a much lower degree of fluidity; i.e., at temperatures below about 200~C, poly(vinyl chloride) is sufficiently soft to permit its introduction into molds` or extrusion from dies having relatively large openings.
Thus, the discovery that certain poly(vinyl chloride) compositions as defined herein not only can be meltblown, but meltblown safely without the generation of hydrogen chloride or other harmful volatile materials, was surprising and unexpected and contrary to the conventional wisdom of those having ordinary skill in the art.

Summary of the Invention It therefore is an object of the present invention to provide meltblown fibers which are formed from a poly(vinyl chloride) composition.
It is a further object of the present invention to provide a meltblown nonwoven web comprised of fibers prepared from a poly(vinyl chloride) composition.
Still another object of the present invention is to provide meltblown fibers which are prepared from a plasticized poly(vinyl chloride) composition.
Yet another object of the present invention to provide a meltblown nonwoven web comprised of fibers prepared from a plasticized poly(vinyl chloride) composition.
A further object of the present invention is to provide an article of manufacture comprised of at least one meltblown nonwoven web comprised of fibers made from a plasticized poly(vinyl chloride) composition.
Yet a further object of the present invention is to provide poly(vinyl chloride) fibers obtained by extracting the 2~8232~

plasticizer from meltblown fibers prepared from a plasticized poly(vinyl chloride) composition.
A still further object of the present invention is to provide a nonwoven web obtained by extracting the plasticizer from a meltblown nonwoven web comprised of fibers prepared : from a plasticized poly(vinyl chloride) composition.
These and other objects will be readily apparent to those - having ordinary skill in the art from the specification and claims which follow.
10Accordingly, the present invention provides meltblown fibers comprising a plasticized poly(vinyl chloride) composi-tion which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, said composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at l90-C under a 2.16-kg load.
The present invention also provides a meltblown nonwoven web comprising a coherent matrix of meltblown fibers formed from a plasticized poly(vinyl chloride) composition which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, said composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM
;Method D 1238 at l90-C under a 2.16-kg load.
The present invention additionally provides poly(vinyl chloride) fibers prepared by:
i (A) meltblowing a plasticized poly(vinyl chloride) composition which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to ,j about 1.6, said composition having a melt flow rate of from .~
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about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190C under a 2.16 kg load; and (B) extracting with a solvent at least about 80 percent of the nonvolatile plasticizer present in the meltblown fibers.
The present invention also provides a nonwoven web comprising a coherent matrix of meltblown fibers formed from a plasticized poly(vinyl chloride) composition which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, said composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method ; D 1238 at 190C under a 2.16-kg load, which web has been extracted with a solvent after formation to remove at least about 80 percent of the plasticizer originally present in the meltblown fibers comprising the web.
In preferred embodiments, the plasticizer is present at a level of from about 30 to about 60 percent by weight, the plasticizer is monomeric, and the plasticizer is selected from the group consisting of phthalates, isophthalates, trimel-litates, adipates, azelates, sebacates, citrates, epoxidized esters, and benzoates.
In other preferred embodiments, the poly(vinyl chloride) has an inherent viscosity of from about 0.5 to about 1.4.
In yet other preferred embodiments, the composition has a melt flow rate of from about 50 to about 500 grams per lO
minutes when measured in accordance with ASTM Method D 1238 at 190C under a 2.16-kg load.
The meltblown fibers and meltblown nonwoven webs of the present invention have unique properties which make such fibers and webs useful in many applications which ; 35 typically employ such fiber- ~d webs.

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20~2322 Brief Des~ription of the Drawinqs Figure 1 is a plot of melt flow rate versus plasticizer content for a given poly(vinyl chloride) and dioctyl phthalate as the nonvolatile plasticizer.
Figure 2 is a plot of the inherent viscosity of a given poly(vinyl chloride) at a nonvolatile plasticizer concentra-tion which is estimated to give a melt flow rate of 100 g/10 min at 190C and a 2.16-kg load. The nonvolatile plasticizer was dioctyl phthalate.
Figure 3 is a comparative bar chart showing peak load in lbs for meltblown, point bonded, and extracted nonwoven webs, respectively, at different levels of a nonvolatile plasticizer, dioctyl phthalate, both with and without a processing aid. The data were normalized to a basis weight of 100 grams per square meter (gsm).
Figure 4 is similar to Figure 3, except that the percent pea~ elongation is shown instead of peak load.
Figure 5 also is similar to Figure 3, except that peak energy in inch-lbs is shown instead of peak load. The data were normalized to a basis weight of 100 gsm.
Figure 6 is a plot of tensile strength versus percent plasticizer for a given poly(vinyl chloride) and dioctyl phthalate as the nonvolatile plasticizer.
Figure 7 is a plot of elongation to break versus percent plasticizer for a given poly(vinyl chloride) and dioctyl phthalate as the nonvolatile plasticizer.

Detailed Description of the Invention As used herein, the term "meltblown fibers" means fibers formed by extruding a molten thermoplastic material through a plurality of die capillaries or orifices as molten threads or filaments into a high-velocity gas (e.g., air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter and orient the molecules comprising the `` .

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filaments. The resulting meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly distributed fibers, i.e., a meltblown nonwoven web. Such a process is disclosed, for example, in U.S. Patent No. 3,849,241 to Butin, the disclosure of which is incorporated herein by reference.
Depending upon the die capillary diameters and the extent of attenuation, microfibers may result. As used herein, the term "microfibers" means fibers having an average diameter of less than about 100 micrometers. In practice, microfibers obtained by meltblowing processes will have average diameters of from about 0.5 to about 50 micrometers and preferably will have average diameters of from about 4 to about 40 micro-- meters.
The compositions used to form the fibers and webs of the present invention must contain two major components: (1) a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, and t2) a nonvolatile plasticizer.
As used herein, the term "nonvolatile plasticizer" means that the plasticizer has a sufficiently low vapor pressure at the extrusion temperatures employed such that substantially all of the plasticizer remains in the fibers.
The poly(vinyl chloride) in general can be any polytvinyl chloride) which meets the requirements set forth herein.
Thus, the polymer can be prepared by bulk, suspension, or emulsion polymerization.
Additionally, the term "poly(vinyl chloride)" is used herein to include homopolymers and copolymers, although in the latter case the copolymer should contain at least 50 mole percent of units derived from vinyl chloride. Copolymers can be random, block, graft, or alternating polymers of two or more monomers, at least one of which is vinyl chloride.
Examples of the more common copolymers include copolymers of vinyl chloride with one or more of vinyl acetate, acryloni-trile, ethylene, propylene, and the like.

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2Q~2322 The term "poly(vinyl chloride)" also encompasses blendsof a poly(vinyl chloride) with one or more other polymers.
Polymers suitable for the preparation of such blends include, among others, acrylonitrile-butadiene-styrene copolymers, poly(~-caprolactone), ethylene-vinyl acetate copolymers, chlorinated ethylene-vinyl acetate copolymers, chlorinated poly(vinyl chloride), polyurethanes, ethylene-vinyl acetate copolymers with carbon monoxide or sulfur dioxide, styrene-acrylonitrile copolymers, nitrile-butadiene rubbers, vinyl chloride-vinyl acetate copolymers, polyesters, and the like.
The poly(vinyl chloride) should have an inherent viscosity of from about 0.3 to about 1.6. Preferably, the inherent viscosity will be in the range of from about 0.5 to about 1.4. This latter range corresponds approximately to a 15 molecular weight range of from about 50,000 to about 160,000.
The molecular weight distribution of the poly(vinyl chloride) is not known to be critical, in part because the molecular weight distributions of polymers are independent of the method of preparation. Most commercially available polymers appear to have polydispersity indexes (M~M~) in the range of from about 2.5 to about 2.7.
The nonvolatile plasticizer can be any one or more of the well-known plasticizers for poly(vinyl chloride), provided only that they are sufficiently stable at temperatures of the order of 200-C or less and sufficiently nonvolatile at such ;temperatures and the concentrations employed. Examples of suitable classes of nonvolatile plasticizers include, by way of illustration only, phthalates, phosphates, adipates, azelates, sebacates, epoxidized esters, trimellitates, benzoates, citrates, isophthalates, pentaerythritol esters, glycolates, ricinoleates, oleates, stearates, terephthalates, polyesters and other polymeric materials, and the like. The phthalates are preferred because of their availability.
i Examples of specific nonvolatile plasticizers include, ,35 among others, dimethyl phthalate, diethyl phthalate, di(2-'methoxyethyl) phthalate, diisobutyl phthalate, dibutyl ;1;
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phthalate, dihexyl phthalate, dicyclohexyl phthalate, diisohexyl phthalate, buty benzyl phthalate, butyl octyl phthalate, buty decyl phthalate, diisooctyl phthalate, di-2-ethylhexyl phthalate, dicapryl phthalate, diisodecyl phthal-ate, isooctyl isodecyl phthalate, a-hexYl-n-decyl phthalate, n-octyl-a-decyl phthalate, isodecyl tridecyl phthalate, ditridecylphthalate, dibutoxyethylphthalate,di-2-ethylhexyl isophthalate, acetyl tributyl citrate, dimethyl sebacate, dibutyl sebacate, diiosoctyl sebacate, di(2-ethylhexyl) sebacate, diisobutyl adipate, di[2-(2-butoxyethoxy)ethyl]
adipate, diisooctyl adipate, di(2-ethylhexyl) adipate, dinonyl adipate, diisodecyl adipate, dibutoxyethyl adipate, isooctyl isodecyl adipate, n-hexyl-n-decyl adipate, n-octyl-a-decyl adipate, trisooctyl trimellitate, tri-2-ethylhexyl trimel-litate, epoxidized soybean oil, octyl epoxytallate, 2-ethylhexyl epoxytallate, triethylene glycol di(caprylate-caprate), triethylene glycol dicaprate, cresyl diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, glycerol monoricinoleate, isopropyl myristate, butyl oleate, glycerol trioleate, methyl oleate, n-propyl oleate, isopropyl oleate, a-butyl stearate, and the like.
The nonvolatile plasticizer can be a single compound or two or more compounds from the same class or two or more classes. If two or more compounds are used, they independent-ly may be monomeric or polymeric. Monomeric plasticizers arepreferred because the efficiency of a plasticizer in lowering the melt viscosity of poly(vinyl chloride) is in part dependent upon the molecular weight of the plasticizer, with efficiency being inversely proportional to plasticizer i 30 molecular weight.
Plasticizer can be present at a level of from about 20 to about 80 percent by weight, based on the amount of poly(vinyl chloride) present in the composition. The presence of other thermoplastic polymers usually permits a reduction in the amount of plasticizer employed. However, the extent :.
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`of the reduction depends upon the amount and nature of such other polymers and typically is determined empirically.
In keeping with the practice of those having ordinary skill in the art, the amount of nonvolatile plasticizer also can be expressed in parts per 100 parts of resin (phr), where the resin constitutes all thermoplastic polymers present, including both poly(vinyl chloride) and other polymers.
Because most of the experimental data included in this specification utilized only poly(vinyl chloride), however, this practice has not been followed herein.
The poly(vinyl chloride) compositions employed in the present invention also may include one or more primary heat stabilizers which serve to prevent or reduce discoloration during melt processing. In general, a suitable primary heat stabilizer should be a hydrogen chloride scavenger, react with free radicals, react with double bond structures, and serve ;as an antioxidant. If desired, a secondary stabilizer, i.e., a compound which is ineffective when nst used in combination with a primary stabilizer, also may be present in the compositions.
Examples of suitable primary stabilizers include, by way ~, of illustration only, lead compounds, such as dibasic lead ~,phosphate, dibasic lead stearate, lead sulfate, lead chloro-;silicate, dibasic lead phthalate, and the like; organotin ~25 compounds, such as dibutyltin maleate, dibutyltin dilaurate, ;~di(a-octyl) tin maleate polymer, and the like; tin mercap-tides, such as dibutyltin lauryl mercaptide, dibutyltin ,isooctyl thioglycollate, dibutyltin mercatopropionate, di(n-~octyl)tin-S,S'-bis(isooctylmercaptoacetate), and the like;
!~30 barium-cadmium-zinc compounds, such as barium 2-ethylhexoate, barium nonylphenate, cadmium 2-ethylhexoate, barium, cadmium ,;~and zinc laurates and stearates, and the like; calcium-zinc compounds, such as calcium and zinc stearates, and the like;
polyols and nitrogen compounds, such as pentaerythritol, i35 sorbitol, melamine, benzoguanamine, dicyandiamide, and the ;~1like; and the like~

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2~2322 Suitable secondary stabilizers, include, among others, epoxies, such as epoxidized soya oil, epoxidized linseed oil, epoxidized tall oil esters, butyl and octyl epoxy stearate, and the like; phosphites, such as diphenyldecyl phosphite, phenyldidecyl phosphite, tris(nonylphenyl) phosphite, and the like; and the like.
The preferred primary stabilizers are organotin compounds and calcium and zinc compounds. The most preferred compounds are dioctyl tin maleate and calcium and zinc stearates.
Epoxidized soybean oil worked well as a secondary stabilizer with the calcium and zinc stearates.
Other additives can be employed, if desired. Such other additives include, by way of illustration only, fillers, such as aluminum silicate hydrate (clay), aluminum silicate (calcined clay), magnesium silicate (talc), potassium aluminum silicate (mica), calcium carbonate (calcite or whiting), silica (diatomaceous earth), titanium dioxide, barium sulfate (barytes), and the like; colorants, i.e., dyes and pigments, the latter of which may be either inorganic or organic;
processing aids, such as acrylics, certain ABS resins, chlorinated polyethylene, and the like; impact modifiers, such as acrylic copolymers, ABS resins, chlorinated polyethylene, ethylene-vinyl acetate copolymers, fumaric ester copolymers, various graft copolymers, and the like; lubricants, such as stearic acid and metal stearates, petroleum-based waxes, mineral and vegetable oils, low molecular weight polyethylene, amide and ester waxes, silicone oils, and the like; light ; stabilizers, such as benzophenones, benzotriazoles, salicyl-ates, substituted acrylonitriles, monobenzoates, and the like, fungicides; flame retardants, such as phosphate esters, chlorinated hydrocarbons, antimony oxide, barium metaborate, and the like; antistatic agents, such as quaternary ammonium compounds and the like; brighteners; antioxidants; and the like.
The levels of heat stabilizers and other additives which may be used are not known to be critical, particularly since 20~232~
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a number of such materials also act as plasticizers. In general, the use of such materials follows the practice of those having ordinary skill in the poly(vinyl chloride) art.
The plasticized poly(vinyl chloride) compositions of the present invention are formed into fibers by any of the well-known meltblowing techniques. See, by way of example, U.S.
Patent Nos. 3,016,599 to Perry, Jr., 3,704,198 to Prentice, 3,755,527 to Keller et al., 3,849,241 to Butin et al., 3,978,185 to Butin et al., 4,100,324 to Anderson et al., 10 4,118,S31 to Hauser, and 4,663,220 to Wisneski et al. See, also, V. A. Wente, "Superfine Thermoplastic Fibers", In-dustrial and Enaineering Chemistry, Vol. 48, No. 8, pp. 1342-1346 (1956); V. A. Wente et al., "Manufacture of Superfine Organic Fibers", Naval Research Laboratory, Washington, D.C., 15 NRL Report 4364 (111437), dated May 25, 1954, United States ~; Department of Commerce, Office of Technical Services; and Robert R. Butin and Dwight T. Lohkamp, "Melt Blowing - A One-Step Web Process for New Nonwoven Products", Journal of the Technical Association of the Pulp and Paper Industry, Vol. 56, 20 No.4, pp. 74-77 (1973).
The meltblown fibers generally are laid in a random fashion to form a nonwoven web or fabric. The web can be used as is or incorporated into an article of manufacture, such as battery separators, filters, electrical cable components, wipers, vacuum cleaner bags, industrial and surgical face masks, oil-absorbent fabrics, car covers, boat covers, surgical fabrics, insulation, clothing, and the like.
The present invention is further described by the examples which follow which illustrate certain preferred embodiments, Such examples are not to be construed as in any way limiting either the spirit or scope of the present invention.
In the examples, all temperatures are in degrees Celsius and all amounts are in parts by weight, unless otherwise indicated. Additionally, melt flow rates were determined in accordance with ASTM Method D 1238-82, Standard Test Method - 2o~2322 for Flow Rates of Thermoplastics by Extrusion Plastometer, using a Model VE 4-78 Extrusion Plastometer (Tinius Olsen Testing Machine Company, Willow Grove, Pennsylvania) having an orifice diameter of 2.0955 + 0.0051 mm: unless specified otherwise, test conditions were at a temperature of 190DC and a load of 2.16 kg.

Examples 1-6 The first two poly(vinyl chloride) resins evaluated were high-flow compositions developed for injection molding, designated Geon 87239 and Developmental Compound #7 (referred to hereinafter as BFG~7), respectively. Both were manufac-tured by The B. F. Goodrich Co., Cleveland, Ohio. The latter resin was supplied with and without a black pigment (BFG#7 and BFG#7A, respectively). All of the resins contained unspeci-fied stabilizers and processing aids.
i Analysis of the two resins by gel permeation chromatog-raphy (GPC) indicated that they had weight-average molecular ; 20 weights (M~) of 53,267 and 41,535, respectively. Neither Geon 87239 nor BFG#7 would flow under the standard melt flow rate ; test conditions, and BFG#7A had a melt flow rate under the standard test conditions of only 1.79 g/10 min.
Various plasticized compositions were prepared from the three resins. In each case, the resin was ground to particles less than 2 mm diameter in a Wiley mill (Thomas Wiley Laboratory Mill, Model 4, Arthur H. Thomas Co., Philadelphia, PA). Ground resin then was mixed with the desired amount of nonvolatile plasticizer by means of a Kitchen/Aid mixer (Kitchen/Aid Mixer, Model X5-A, KitchenAid Division, Hobart Corporation, Troy, Ohio). The resulting mixture, which resembled wet sand, was placed in an oven at about 100 for four hours. The plasticizer was absorbed by the resin to give what is referred to herein as a "dry blend". Six dry blend compositions were prepared as summarized in Table 1.

-- 2o~2322 Table 1 Summary of Dry Blend Compositions Resin _ Plasticizer Melt Flow Ratea Ex. Type Wt. ~ Compd. Wt. % 175 ~go 1 BFG#7 60 DOpb 40 N/Dc V.H.d - 2 BFG#7 70 DOP 30 136 314 3 BFG#7A 60 DOP 60 V. H . N/D

4 BFG#7A 70 DOP 30 77 227 BFG#7A 60 ATBCe 40 V.H. V.H.
6 Geon 60 ATBC 40 177 N/D
aExpressed as g/10 min.
bDioctyl phthalate.
CNot determined.
dVery high (too high to be measured).
eAcetyl tributyl citrate.

' As a simple screening method, each dry blend composition was meltblown in a bench-scale apparatus having a single , 20 orifice in the die tip. The apparatus consisted of a cylindrical steel reservoir having a capacity of about 15 g.
The reservoir was enclosed by an electrically heated steel jacket. The temperature of the reservoir was thermostatically v- controlled by means of a feedback thermocouple mounted in the body of the reservoir. The extrusion orifice had a diameter of 0.016 inch (0.41 mm) and a length of 0.060 inch (1.5 mm).
A second thermocouple was mounted near the die tip. The exterior surface of the die tip was flush with the reservoir ~ body. Composition extrusion was accomplished by means of a '` 30 piston driven by compressed air in the reservoir. The extruded filament was surrounded and attenuated by a cylindri-cal air stream exiting a circular 0.075-inch (l.9-mm) gap.
Attenuating air pressures typically were of the order of 5-90 psig. The forming distance was approximately 6 inches (15 cm). The attenuated extruded filament was collected on an `' ` 2Q82~2~
aluminum wire screen (standard commercial window screen). The results are summarized in Table 2.

Table 2 Summary of Meltblowinq Experiments Example Extrusion Temp.. Web Characteristics 1 163 Stretchy, leathery ;~ 2 191 Soft 3 172 Stretchy, leathery 4 182 Cottony, large fibers 160 Stretchy, rubbery 6 171 Some degradation, - stretchy ; 15 In general, the webs were composed of fine fibers ~less than about 15 micrometers in average diameter) and were soft, drapable, and free of shot. The webs exhibited low tear ; resistance.
Exam~le 7A

; A larger quantity of the dry blend employed in Example 3 was prepared. The dry blend was subjected to thermo-gravimetric analysis, differential scanning calorimetry, and melt flow rate evaluations. Thermogravimetric analysis employed a DuPont Model 1090 Thermal Analyzer with a Model 1091 Disc Memory and a Model 950 Thermal Gravimetric Analyzer (DuPont Instruments, Wilmington, Delaware). Differential scanning calorimetry was carried out with a DuPont Model 1090 Thermal Analyzer with a Model 1091 Disc Memory and a Model 910 Differential Scanning Calorimeter (DuPont Instruments).
The results were as follows:
(A) Thermogravimetric Analysis.
(1) Weight loss under nitrogen at a heating rate of 10/min . - 19 -.. . .

2~82~2~

(a) 1.0 percent at 205.
(b) 10.0 percent at 258.
(2) Weight loss in air at a heating rate of 10/min.
(a) 1~0 percent at 200.
(b) 10.0 percent at 250.
(3) Weight loss over time at 174 under nitrogen.
(a) After 0 min, 0.5 percent (baseline).
(b) After 5 min, 1.5 percent.
(c) After 10 min, 3.0 percent.
(d) After 30 min, 7.0 percent.
(e) After 60 min, 13.0 percent.
(f) Average weight loss rate, 0.21 percent/min.
(4) Weight loss over time at 188 under nitrogen.
(a) After 0 min~ 1.0 percent (baseline).
(b) After 5 min, 2.5 percent.
(c) After 10 min, 4.5 percent.
(d) After 30 min, 11.5 percent.
(e) After 60 min, 19.5 percent.
(f) Average weight loss rate, 0.31 percent/min.
(B) Differential Scanning Calorimetry (heating rate of 10/min).
(1) No distinct crystalline melting point was detected.
(2) Endothermic decomposition of the sample began at about 250.
(C) Melt Flow Rate Evaluations.
(1) At 160.
~- (a) 128 g/10 min, with a 5 min holding time.
`; (2) At 175.
(a) Too fast to measure, at holding times of 5, lS, and 30 min.
(3) At 190.

(a) Too fast to measure, at holding times of 5, 15, and 30 min.

~, I

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(D) Other Observations.
(1) Hydrogen chloride is known to be a product of the thermal decomposition of poly(vinyl chloride).
To test for its evolution at processing tempera-- 5 tures,, moist blue litmus paper was placed next to the orifice of the extrusion plastometer during the melt flow rate measurements. The litmus did not change color after 20 minutes at 190. Moist blue litmus paper also was placed at the gas exit of the thermogravimetric analyzer after samples had been heated for 60 min at both 174 and 188. Again, no color change was observed. The differential scanning colorimetry result suggests that hydrogen chloride evolution should not take place until the resin temperature reaches about 250.
(2) Vinyl chloride is a possible contaminant in all commercial poly(vinyl chloride) resins. A
Matheson-Kltagawa Toxic Gas Detector (Model 8014KA, with a Model 8014-400A Precision Sampling Pump, Matheson Gas Products, Inc., Secaucus, NJ) was used to detect the presence of vinyl chloride at the orifice of the extrusion plastometer.
After heating the sample at 175 for 15 minutes, no vinyl chloride was detected when th sample was extruded. The detector is sensitive to a vinyl chloride concentration of 0.1 ppm. The threshold limit value (TLV) of vinyl chloride is 1.0 ppm (eight-hour time-weighed average).
i 30 (3) The isothermal thermal gravimetric an~lyses at ;~ 174 and 188 indicated that a slow volatiliza-tion was taking place. Since neither hydrogen chloride nor vinyl chloride apparently was evolved under those conditicns, the analyses probably were detecting the loss of plasticizer, i.e., dioctyl phthalate (DOP). However, `:
.:

2~2322 plasticizer loss during meltblowing was deemed to present either no or an acceptably low health risk. The LC50 of DOP is 30,000 mg/m3, and the material has a high boiling point (384 at 760 mm Hg) .

Example 7B

The dry blend of Example 7A was extruded through a 0.75-inch (l9-mm) diameter Brabender extruder e~uipped with a film die to check on the evolution of either hydrogen chloride or vinyl chloride and to determine the processability of the composition. No gas evolution was detected (the Matheson-Kitagawa Toxic Gas Detector already described was used for both hydrogen chloride and vinyl chloride detection) and no problems were encountered during extrusion. However, the film was opaque, apparently because the dry blend did not produce a homogenous mixture upon melting.
The tensile properties of the film were determined by means of an Instron Model 1122 (Instron Corporation, Canton, Massachusetts), following manufacturer's instructions and ~ approximating ASTM standards. Test samples had a width of 0.5 ; inch (about 1.2~ mm). The tensile properties are summarized in Table 3.
Table 3 Summary of Film Tensile Pro~erties ' Initial Tensile Peak 305ample Modulus, ~si Strenath psi Elonqation. %
Film 244 220 105 The low values for tensile properties reported in Table 3 may be the result of the nonhomogeneity of the molten blend.

.~

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' i`
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Example 7C

The dry blend of Example 7A then was meltblown at four throughput values on a pilot-scale meltblowing apparatus - 5 essentially as described in U.S. Patent No. 4,663,220, which - is incorporated herein by reference. Briefly, such meltblow-ing was accomplished by extruding the dry blend through a 0.75-inch (19-mm) diameter Brabender extruder and then through a meltblowing die having nine extrusion capillaries per linear inch (approximately 3.5 capillaries per linear cm) of die tip.
Each capillary had a diameter of about 0.0145 inch (about 0.37 mm) and a length of about 0.113 inch (about 2.9 mm).
The collecting arrangement consisted of a rotating 15.2-cm wide drum having a diameter of 76.2 cm. The surface of the drum was a screen.
The four meltblowing runs are summarized in Tables 4 and 5.

Table 4 Summary of Extruder Conditions Through- Melt Barrel Die Tip Example _ put Temp... Press.b Press.C
7A 1.9 lS1 2000-2500 73 ,~ 25 7B 2.3 151 2000-2500 28 " 7C 4.1 151 2000-2500 48 ; 7D 6.5 151 2000-2500 78 In g/min-', bExpressed as psi.
, 30 Table S
Summary of Attenuation Conditions ; Example Air Temp... _ r Press... si 7C1 208 1.5 7C2 206 5.0 ~' ~ - 23 -~ .~

2~2322 7C3 204 5.0 ! 7C4 204 5.0 .

In each case, the resulting nonwoven web had a suede-like hand, but was not very strong. The tensile properties of a web (that of Example 7c3) were determined as described for Example 7B. The tensile properties are summarized in Table 6.

Table 6 Summary of Tensile Proerties Initial Tensile Peak Sam~le Modulus ~siStrenath ~si Elonaation %
15 Weba 117 77 55 Webb 5,600 145 7 aOne-inch gauge length.
' bZero gauge length.
:' Although both resins studied in Examples 1-6 produced interesting meltblown fibers in the form of nonwoven webs, an understanding of how composition affects processibility and fiber and web properties requires a knowledge of the constituents of the compositions. Since both Geon 87239 and BFG#7 contained proprietary additives, they were unacceptable for this purpose. Consequently, it was necessary to continue the experimental work with resins free of additives.
Accordingly, a number of such resins were obtained, as summarized in Table 7.
Table 7 Summarv of Additive-Free Resins Resin Source Type Inh. Visc. a Geon llOx377 Goodrichb Suspension 0.53 Geon llOx344 GoodrichSuspension 0.68 ~82~22 :
Geon 125 Goodrich Dispersion 0.81 Geon 110x426 Goodrich Suspension 0.90 Geon 30 Goodrich Mass 1.00-1.04 Geon 102EP-F5 Goodrich Suspension 1.10-1.16 Geon 121 Goodrich Dispersion 1.20 FPC 9339 OccidentalC Suspension 1.33 aInherent viscosity.
bThe B. F. Goodrich Co., Cleveland, Ohio.
COccidental Chemical Corp., Norwalk, Connecticut.

.The dispersion resins had much finer particle sizes than the suspension resins. It was found that particle size had a profound effect on the behavior of the resin upon the ;addition of plasticizer. For example, the addition of dioctyl phthalate to an equal part of a dispersion resin resulted in an opaque, viscous mass or plastisol that developed a cheese-like consistency upon heating to 80-. A suspension resin, on the other hand, resembles wet sand when plasticizer is first added and becomes a dry powder upon heating as described in i;~20 Examples 1-6. Further heating of plasticized compositions of ~;both types of resins above the melting temperature of the resin (about 120-) results in clear, flexible solids.
~;
;Example 8 A plasticized poly(vinyl chloride) composition was prepared by mixing 60 parts of Geon 121 with 40 parts of ridioctyl phthalate. A film was prepared from the blend, and film tensile properties determined, as described in Example 7B. The tensile properties are summarized in Table 8.
', . , .
. ~
'::

, .

, , . .

2~2322 Table 8 Summar~ of Film Tensile Properties Initial Tensile Peak 5Sample Modulus psi Strenqth. psi Elonaation %
Film 632 1,957 556 From the results of Examples 7B and 8, it is apparent that fiber and/or web properties are at least in part dependent upon the poly(vinyl chloride) resin employed.

Examle 9 Recognizing that plasticizing poly(vinyl chloride) lowers the strength of shaped articles prepared from the plasticized composition, the use of plasticizers which can be polymerized after the formation of fibers was investigated. Three ;; unsaturated plasticizers were studied: diallyl phthalate ; (DAP), trimethylolpropane triacrylate (TMPTA), and trimethyl-olpropane trimethacrylate (TMPTMA). Films were prepared from blends containing 40 percent by weight of plasticizer as described in Example 7B. Films then were irradiated with 200-keV electrons in a pilot-scale electron beam apparatus at Energy Sciences, Inc. (Woburn, Massachusetts) at a dose level of 1 MRad. The TMPTA-containing films turned brown upon being irradiated, while the other films showed only slight dis-coloration. Tensile strengths of films before and after irradiation were determined as already described; the results are summarized in Table 9.
' Table 9 Summarv of Film Tensile Properties MRad Initial Tensile Peak 35 Film ResinPlast. Dose Mod. aStrenqtha Elonq. b 9A BFG#7ADAP 0 213 105 60 . .

98BFG#7A DAP 1216 138 80 9CBFG#7A TMPTMA 0215 154 85 9DBFG#7A TMPTMA 140,000 436 10 9EGeon 121 TMPTMA 0 610 2,550 400 9FGeon 121 TMPTMA 1125,000 5,270 66 9GGeon 125 TMPTMA 0 500 1,600 497 9HGeon 125 TMPTMA 160,000 3,550 15 aIn psi-Expressed as percent.
~',,. 10 The data from Table 9 suggest that DAP did not cure to any significant extent at a dose level of 1 MRad. However, films containing TMPTMA showed a dramatic change in tensile properties after irradiation. Although tensile properties were not determined for films containing TMPTA, the irradiated ~; films were similar to those containing TMPTMA.
While the post-formation curing process certainly has not been optimized, the data in Table 9 clearly demonstrate the feasibility of such an approach.
Example 10 .~, .
; The experimental efforts turned at this point to an evaluation of heat stabilizers. Initially, the following four stabilizers were studied, all of which were proprietary materials from Interstab Chemicals, Inc. New Brunswick, New Jersey):
(1) CZL-731, a calcium-zinc stabilizer;
(2) R4137, a barium-cadmium stabilizer;
(3) T-235, a sulfur-containing organotin compound; and (4) LT2000, another calcium-zinc stabilizer.
` Stabilized compositions were prepared by blending 120 parts of Geon 125, 80 parts of DOP, and 3.6 parts of stabilizer.
The stability of such composition was evaluated by (a) heating ; 35 in the plastometer at 190- for 10 minutes and observation any discoloration; (b) placing a sample of the composition on a . ;
, '~, ' . , . , ' ,~

`` 2~g2~22 hot bench at 260 and recording the order in which samples darken; and (c) thermogravimetric analysis. All three methods were in agreement as to the relative effectiveness of the stabilizers. Thermogravimetric analysis, however, suggested that the temperature at which the first weight loss begins , (i.e., the first inflection point) is a convenient measurement of the stability of the composition. Thus, the higher the temperature of the inflection point, the more stable the composition. The inflection points of the four compositions are summarized in Table 10.

Table 10 Summary of Inflection Points of Stabilized Compositions StabilizerInflection Point None 304.6 CZL-731 303.8 R4137 320.1 ~, , .
LT2000 320.4 T-235 327.6 .
Unfortunately, the most effective stabilizer, T-235, imparts an unpleasant odor to the composition. Continuing , 25 evaluations of stabilizers led to the use of dioctyl tin maleate, a stabilizer obtained from M&T Chemicals (M&T
Chemicals, Inc., Rahway, NJ) as Thermolite 813; the compound typically was used at a concentration of 3.0 phr (parts per hundred parts of resin).
A second replacement for T-235 was subsequently identi-fied. This replacement consisted of a mixture of Therm-Chek 765C (Ferro Corporation, Chemical Division, Bedford, Ohio), Therm-Chek 5526 (Ferro Corporation), and epoxidized soybean oil (ChemCentral Corporation, Chicago, IL). The three components generally were employed at concentrations of 3.0 phr, 2.0 phr, and 10.0 phr, respectively. Therm-Chek 765C is . . .
.' ~ '. .
.~ , .
.. ^ , . .

a mixture of calcium and zinc stearates in powder form and Therm-Chek 5526 is tris(nonylphenyl)phosphate.

Example 11 In order to evaluate the relationship between melt flow rate and resin molecular weight and plasticizer content, 16 compositions were prepared as summarized in Table 11, with each composition also containing 3.0 phr T-235 stabilizer.
,' 10 Table 11 Summary of Plasticized Compositions ,.
Geon Resin % DOP
15Tv~e Inh. Visc. 30 40 50 60 70 80 121 1.20 X X X M X M
; 125 0.81 X X M X
110x334 0.68 X X X
110x377 0.53 M X X
In the table, an "X" or an "M" indicates that the composition was prepared and a melt flow rate determined. Compositions marked with an "M" were meltblown as described in Examples 1-6 with similar results.
The melt flow rate of each Geon 125-containing compo-sition was plotted on log-log paper against the percentage of poly(vinyl chloride) in the composition. The resulting plot, shown in Figure 1, is linear. Point A, representing a composition containing 53.9 percent by weight Geon 125, is the interpolated value for a composition having a melt flow rate of 100 g/lO min. Such a melt flow rate is the approximate minimum required for satisfactory meltblowing performance.
The procedure was repeated for each of the other three types of resin (plots not shown).
The weight-percent of poly(vinyl alcohol) in each interpolated resin composition then was plotted on log-log ~, -- 20~232~
. .
paper against the inherent viscosity of the poly(vinyl al-cohol), as shown in Figure 2. Again, a linear plot was obtained. Because the plot represents concentrations of resins having different inherent viscosities which will result in a melt flow ratP of 100 g/10 min at a temperature of 190 and a load of 2.16 kg, combinations of inherent viscosity and resin concentration which clearly fall above the line, or to ~- its right, identified as Region A, probably cannot be meltblown to give satisfactory fibers. On the other hand, combinations of inherent viscosity and resin concentration falling in Region B probably can be meltblown successfully.
Although the plots represented by Figures 1 and 2 apply only to the use of dioctyl phthalate as plasticizer and the inclusion in the composition of 3.0 phr T-235 as stabilizer, the procedure can be employed to estimate the probability that any given composition can be meltblown.
In order to illustrate the dependency of melt flow rate on the type of plasticizer employed, five compositions were prepared which contained 100 parts Geon 125, lOO parts 20 plasticizer, and 3.0 phr T-235 as heat stabilizer. The melt flow rate of each composition then was measured as summarized in Table 12.

Table 12 Effect of Plasticizer on Melt Flow Rate PlasticizerMelt Flow Ratea Dioctyl adipate 410 Dioctyl phthalate 237 30 Tricresyl phosphate 203 Diisodecyl phthalate170 Trioctyl trimellitate lO9 aIn g/10 minutes.

In view of the foregoing, it is clear that the melt flow rate can be increased by either increasing the amount of "., , . . .

plasticizer present in the composition or by replacing the ` plasticizer with one which has a greater effect upon melt flow rate. Other approaches will be apparent to those having ordinary skill in the art, such as by the inclusion of a flow -~ 5 modifier.
.~
~ Example 12 `' Four compositions containing dioctyl phthalate as plasticizer and 3.0 phr T-23S as heat stabilizer were meltblown as described in Examples 1-6. The compositions are . .
;~ summarized in Table 13 and the meltblowing conditions are summarized in Table 14.
A' 15 Table 13 Summary of Meltblown Compositions ~: .
Geon Resin Example Resin Inh. Visc. % DOP
2012A 110x377 0.53 30 12B 125 0.81 50 12C 121 1.20 60 12D 121 1.20 80 Table 14 i~ 25Summary of Meltblowina Conditions ,,:
Barrel Melt Air Example Temp.. Temp.. Press. psi , 3012B 104-127 163-196 4-20 :~ 12C 121-135 164-204 4-20 '~
, ~In each case, the barrel pressure was maintained at 200 psi, ; 35 although a 400-psi barrel pressure was explored in Example , .'' ::`

~. ~ .,; , :' .

" 20~2322 12A, and the attenuating air temperature was maintained at 177-182 .
The effect of meltblowing conditions on fiber diameter was explored in Example 12C. In all samples, there was a wide distribution of fiber diameters. Fiber diameters decreased from 153 + 22 micrometers at a melt temperature of 164-166 to 47 + 15 micrometers at 197--199. Minimum fiber diameters of 4.7 + 2.3 micrometers were obtained with an air pressure of about 15 psi, a melt temperature of 194-197, and a barrel pressure of 200 psi. The optimum barrel pressure in general was about 200 psi, with lower pressures causing shot production and higher pressures resulting in larger diameter fibers.
The webs of Example 12D were particularly interesting because of the high plasticizer content. The webs resembled very soft rubber and were surprisingly strong. Photomicro-graphs of the webs indicated that the fibers fused together extensively, possibly in flight as well as on the forming surface. Some photomicrographs showed a structure inter-mediate between that of a fibrous web and a porous membrane.

Example 13 Following the procedure of Examples 1-6, a composite web was produced by orienting two of the bench-scale meltblowing apparatus at approximately 90- from each other. One apparatus was oriented vertically with the die tip in the downward direction and the other apparatus was oriented horizontally with the die tip facing the vertically oriented apparatus.
The straight-line distance between the two die tips was 5.75 inches (14.5 cm). Thus, the extruded filaments met at a point 4 inches (10.2 cm) from each die tip. The confluent filament stream was directed at a 45 angle from the vertical. The forming distance was either 4 or 12 inches (10.2 or 30.5 cm), measured from the point of confluence to the collecting ' ' :' : ' ' . ~ ' . ~
. . .

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: arrangement. The collecting arrangement was a 400 open-ings/in2 (62 openings/cm2) screen attached to a vacuum hose.
The vertical apparatus was charged with a 400 melt flow rate equivalent grade of polypropylene containing a peroxide additive (Himont PF-Oll, Himont Incorporated, Wilmington, DE).
` The horizontal apparatus was charged with a compositions consisting of 49.23 weight percent Geon 125, 49.30 weight percent DOP, and 1.48 weight percent T-235 as heat stabilizer.
^ A coherent meltblown composite web was obtained.
Examples 14-42 A number of plasticized poly(vinyl chloride) compositions were meltblown as described in Example 7C. The die had 14 extrusion capillaries and the die tip configuration was a positive 0.010 inches (0.25 mm) (see U.S. Patent No.
4,663,220, referred to earlier, for a description of die tip configuration). The air gaps were approximately 0.060 inch (about 1.5 mm). In Examples 14-16, inclusive, however, a negative or recessed die tip configuration was employed and the air gaps were 0.090 inch (about 2.3 mm).
The temperatures of the three extruder barrel zones were approximately 132, 138, and 166, respectively. The die zone temperature was in the range of from about 182 to about 197. The highest air temperature employed was 204.
The results of these meltblowing trial are summarized in Tables 15-18, inclusive. The values given for die tip viscosities are calculated values, based on the formula, two times the die tip pressure divided by the throughput in pounds per inch per hour. Throughput, in turn, was based on the number of holes in the die tip which were open and function-ing. The flow modifier, if present, was Paraloid, a high molecular weight (about 1,000,000) polyacrylate (Rohm ~ Haas Co., Philadelphia, Pennsylvania). For convenience, all percents are percents by weight.

2~2~2~

Table 15 Summary of Meltblown Compositions Geon Resin Example Type Wt. ~ % DOPa~ DOTMb ~ FM
14 125 50 50 1.5 o 125 50 50 1.5 0 16 125 50 50 1.5 0 17 llOx344 50 50 1.47 o io 18 llOx344 50 50 1.47 0 19 llOx377 60 40 1.76 0 llOx344 50 50 1.5 o 21 llOx344 50 50 1.5 o 22 llOx344 50 50 1.5 0 23 llOx377 60 40 1.8 0 24 llOx377 60 40 1.8 o llOx344 55 45 1.6 o 26 llOx344 55 45 1.6 o 27 llOx377 65 35 1.9 0 28 llOx377 65 35 1.9 0 29 llOx344 47.6 47.6 1.4 3.3 llOx344 47.6 47.6 1.4 3.3 31 llOx344 47.6 47.6 1.4 3.3 . 32 llOx344 47.6 47.6 1.4 3.3 33 llOx344 47.6 47.6 1.4 3.3 34 llOx377 57 38 1.7 3.3 llOx377 57 38 1.7 3.3 36 llOx377 57 38 1.7 3.3 37 llOx377 57 38 1.7 3.3 38 llOx344 48.3 48.3 1.4 2.0 ., 39 llOx344 48.3 48.3 1.4 2.0 aWeight percent plasticizer, dioctyl phthalate.
bWeight percent heat stabilizer, dioctyltin maleate.
`~ CWeight percent flow modifier (Paraloid).

:

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Table 16 Summary of Additional Meltblown Compositions Geon Resin Example Type Wt. ~ ~ ATBCa % Stab.b % ESOC % FM~
llOx344 47.2 42.5 2.3 4.7 3.3 41 110x344 47.2 42.5 2.3 4.7 3.3 42 110x344 47.2 42.5 2.3 4.7 3.3 aWeight percent plasticizer, acetyl tributyl citrate.
bWeight percent heat stabilizer, a mixture of calcium and zinc stearates.
CWeight percent secondary heat stabilizer, epoxidized soybean oil.
dWeight percent flow modifier (Paraloid).
Table 17 SummarY of Meltblowinq Conditions - Part I

Barrel Melt Die Ti~ Open 20 Ex. Press.a Tem~.b G/MinC PIHd Press.a Visc.e Holes 14 1000 193 6 0.51 320373 14 lS lO00 196 6 0.79 321241 9 16 1300 196 6 0.51 327385 N/A
17 2200 185 3.2 0.27 260i536 14 18 2000 185N/Af N/A 192j N/A14 19 1600 19610.6 0.90 184122 14 N/A N/A 3.8 0.32 N/AN/A 14 h 21 1800 186 N/A N/A 110 N/A14 22 21009 186 N/A N/A l62k N/A13 23 650 18614.8 1.26 266126 14 24 1250 18511.4 0.97 267164 14 25 1250h 18517.8 1.51 3811138 14 26 1750 18510.0 0.85 241149 14 28 500 184 9.2 0.78 241183 14 29 1300 185 6.2 0.62 168163 12 ' ' 20~2~22 :
301900 184 6.2 0.62 179 170 12 311500 184 3.6 0.39 127 194 11 322000 184 2.4 0.26 102 234 11 331500 184 7.3 0.67 234 208 13 351800 183 2.4 0.20 97 283 14 362400 190 2.8 0.24 91 228 14 371700 190 1.2 0.10 50 292 14 382000 186 3.8 0.32 99 182 14 391800 182 9.4 0.80 48~ 34 14 41300 190 5.2 0.44 136 183 14 421500 190 5.0 0.43 161 225 14 In psi.
bIn degrees.
CExtruder output in grams per minute.
dThoughput in pounds per inch per hour.
eCalculated viscosity, in poise.
fNot available.
9Varied from 300 to 2100.
hVaried from 1000 to 1250.
Varied from 221-260.
jVaried from 73 to 192.
kVaried from 157 to 162.
lVaried from 330 to 381.
Varied from 190 to 241.
"Varied from 42 to 48.
:`
Table 18 Summary of Meltblowing Conditions - Part II
., .
Forming Exam~le Air Temp. a Air Press. b DiStallCeC
14 192 1.5 N/Ad 193 1.75 N/A
16 192 1.75 N/A

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17 181 1.75 38.1 18 181 2.0 38.1 19 205 0.75 N/A
N/A N/A N/A
21 187 3.25 41.9 22 186 3.25 N/A
23 179 4.0 N/A
24 177 5.25 63.5 176 5.25 63.5 26 189 4.75 N/A
27 186 4.5 50.8 28 184 4.5 50.8 29 193 8.25 50.8 198 4.25 50.8 31 197 4.5 45.7 32 198 3.5 45.7 ; 33 195 5.25 45.7 34 189 8.0 45.7 193 8.0 35.6 36 196 4.75 45.7 37 196 4.75 45.7 38 191 4.0 40.6 39 188f 5.5 22.9 188 6 20.3 41 188 6 30.5 42 188 6 40.6 In degrees.
, bIn psi.
CIn cm.
dNot available.
eVaried from 189 to 193.
fVaried from 186 to 188~.

All webs obtained were generally free of shot, had a leathery hand, and were soft and highly drapeable.
, 2o8232~

In order to verify the safety of the meltblowing process when using plasticized poly(vinyl chloride) compositions, air in the vicinity of the die tip was sampled for the following materials during several of the bench-scale and Brabender runs described above and in Examples 1~6, inclusive:
(a) hydrogen chloride t8-hour TLV, 5.0 ppm);
(b) vinyl chloride (8-hour TLV, 1.0 ppm);
(c) dioctyl phthalate (8-hour TLV, 5.0 mg/m3); and (d) organotin compounds (8-hour TLV, 0.1 mg/m3 as Sn).
To detect hydrogen chloride and vinyl chloride, a Matheson-Kitagawa Toxic Gas Detector capable of detecting 0.2 ppm hydrogen chloride and 0.1 ppm vinyl chloride was held manually approximately six inches (15 cm) from the die tip.
Primary air was turned off during sampling in order to create a "worst case" situation. The detection of the other two materials involved pulling air near the die tip through filters at 2.0 and 1.0 liters per minute for organotin compounds and dioctyl phthalate, respectively. The procedure was recommended by the National Institute for Occupational Safety and Health (NIOSH). The filters then were analyzed by ~;~ Environmental Health Laboratory (Macon, Georgia), from whom the filters were purchased.
The NIOSH technique utilized an air pump that draws air i~ through the filter at a rate of 1.0 liter/min. The filter was positioned about 8 inches (20 cm) below and 4 inches (10 cm) to the rear of the die tip of the bench-scale apparatus and about 15 inches (38 cm) from the die tip of the Brabender apparatus. Sampling was conducted under steady-state meltblowing conditions for approximately 50 min. The filter, plus a blank and a background sample, were sent to Environmen-tal Health Laboratory for analysis.
The analysis for organotin compounds presented special problems since the TLV for these compounds is so low.
Initially, analyses were carried out by flame atomic absorp-tion spectrometry. However, the detection limit of thetechnique was too high to definitely establish that the TLV

'~'' 20~2322 for tin had not been exceeded during the runs. Furthermore, prohibitively long running times would be required to sample a sufficient volume of air to bring the detection limit below the TLV. Consequently, an analytical procedure was adopted by the Environmental Health Laboratory which used a graphite furnace instead of a flame for the atomic absorption measure-ments. This latter procedure was more sensitive than flame - atomic absorption and was used for the remainder of analyses for tin. The sampling technique was the NIOSH procedure just described, except that the sampling rate was 2.0 liters/min.
-- The results of the air analyses are sum~arized in Table lg .
;

Table 19 Results of Air Analyses Vinyl Exam~le HCl8ChlorideaDOPb Tinb 12B <0.2<0.1 <0.45 <0.19 14-16 <0.2<0.1 <0.38 <0.11 7_18 <0.2<0.1 <0.34 <0.0056 19 <0.2<0.1 <0.41 <0.0068 20-22 <0.2<0.1 <0.36 <0.0033 23-26 <0.2<0.1 <0.26 <0.0038 27-28 <0.2<0.1 <0.49 <0.0067 29-33 <0.2<0.1 <0.35 <0.0047 34-37 <0.2<0.1 <0.32 <0.0043 38 <0.2<0.1 <0.83 <0.0062 aIn ppm-30 bIn mg/m3.

In no case was any of these substances detected in the air during meltblowing. Furthermore, in all but two cases the . analytical detection limits were well below the OSHA-es-tablished threshold limit values. It therefore was concluded that meltblowing the plasticized poly(vinyl chloride) . . .

'' ' . .
'~ .

~-~ 20~2322 compounds as described herein would not generate unsafe levels of volatile toxic materials.
As already noted, the webs obtained by meltblowing plasticized poly(vinyl chloride) compositions exhibit low strength characteristics. Such characteristics can be improved, however, by extracting part or all of the plas-ticizer after formation of the web. For example, three samples of the web of Example 22 were extracted with methanol, isopropanol, and petroleum ether, respectively. Extractions were carried out by immersing web samples (each approximately 4 cm2) in 100 ml of solvent at ambient temperature. In each case, extraction was 80-90 percent complete after about five minutes, and essentially complete after about 15 minutes. The first two solvents extracted only about 50 percent of the plasticizer contained in the web, while petroleum ether removed greater than 90 percent of the original level of plasticizer in the web. The petroleum ether-extracted web had the feel of coarse wool.
As expected, the tensile properties of extracted webs were altered significantly as a result of the extraction process. Depending upon the composition, peak loads were increased by from about 30 to about 450 percent, while peak elongation was reduced by from about 50 to about 90 percent.
;, Peak energy values were more variable, with both increases and decreases being observed.
Tensile measurements of peak load, peak elongation, and peak energy were made in accordance with standard procedures on a Model 1122 Instron Testing Machine (Instron Corporation, Canton, Massachusetts). Each sample size was 1 x 6 inches (2.5 x 15 cm) and measurements were made with a 4-inch (10.1-cm) gage length. At least three, and usually four, samples were tested for each web. Three different embodiments of each ~,., j nonwoven web were tested: (1) the nonwoven web as obtained from the meltblowing procedure, (2) the nonwoven web after bonding at 86 and 10 psi in accordance with U.S. Patent No.
3,855,046, and (3) the nonwoven web after extracting for 15 .~
~ '~
.

.
' ;.., minutes with petroleum ether to remove most of the plas-ticizer. The average values obtained for peak load, peak elongation, and peak energy, respectively, are shown in Figures 3, 4, and 5, respectively. Each figure consists of three bars for each level of plasticizer, in some instances both with and without a processing aid. In each case, the plasticizer was dioctyl phthalate and the processing aid, when - used, was Paraloid K120N-D at a level of 3.3 percent by weight, based on the amount of poly(vinyl chloride).
10In general, the nonwoven webs before point bonding or extraction have relatively low strength, moderate elongation, and relatively low peak energies. Elongation and peak energy typically are improved by point bonding. Extraction of the plasticizer can greatly improve the tensile strength, but the web becomes stiffer in the process.
It was discovered that the meltblown webs will shrink when subjected to heat. Shrinkage of the web of Example 12B
began at about 75-80~ when heated on a Fisher-Jones Melting Point Apparatus (Fisher Scientific Corp., Pittsburgh, PA).
The extent of shrinkage was directly proportional to tempera-ture, with the web decreasing to about half of its original size at a temperature of about 180. The shrinkage behavior was not altered by extracting plasticizer from the web.
Fiber shrinkage is known to occur with conventionally prepared poly(vinyl chloride) fibers. The ability of the meltblown webs to shrink, however, provides an inexpensive and simple method of preparing stretchable, laminated fabrics.
For example, a web of meltblown plasticized poly(vinyl chloride) can be sandwiched or laminated between two layers of meltblown or spunbonded fabrics. Upon heating the laminate, the center layer will shrink, thereby crimping the laminate. The center layer remains elastic, and the crimped or puckered state of the two outer layers also allows them to stretch. Thus, the enter laminate is stretchable. The advantage offered by this procedure is that it is not ;necessary to maintain the multiple layers under tension during :
'`

2~8~322 the laminating step, which normally is required by traditional stretch-bonded laminate technology.

Example 44 In order to determine whether or not a meltblown web having a tensile strength approximating that of meltblown polypropylene can be prepared from a plasticized poly(vinyl chloride), webs were prepared as described for Examples 1-6 from a blend of 20 percent by weight of poly(vinyl chloride) (FPC 9339 having an inherent viscosity of 1.33, obtained from Occidental Chemical Corp., Norwalk, Connecticut) and 80 percent by weight of dioctyl phthalate. Several web samples were partially extracted with isopropanol, while another web sample was extracted with petroleum ether.
Tensile strength and elongation to break were measured for each of the webs and the resulting values were plotted against percent plasticizer in the web. The plots are shown in Figures 6 and 7, respectively. The data were obtained with ; 20 a gauge length of 10 mm, a draw rate of 200 mm/minute, and a sample width of 2.5 cm.
Polypropylene meltblown webs having a basis weight of 100 g/m2 exhibit tensile strengths in the range of roughly 1 to 2 kg. From Figure 6, it is seen that a 1.33 inherent viscosity poly(vinyl chloride) blended with from about 25 to about 50 percent by weight of dioctyl phthalate should show similar tensile strengths. Figure 7 indicates that such compositions should exhibit elongations to breaks in the range of from about 150 to about 350 percent.
Consequently, a 50:50 resin:dioctyl phthalate blend was prepared. The blend had a melt flow rate at 200- of 11.7 g/10 min. The blend was meltblown as described for Examples 1-6.
Good quality continuous filaments were produced, provided that low air pressures were employed to attenuate the extruded filaments. High air pressures resulted in the formation of large amounts of shot.

' 2~2322 Having thus described the invention, numerous changes and modifications thereof will be readily apparent to those having ordinary skill in the art without departing from the spirit or scope of the invention.

:
, ., .

Claims (20)

1. Meltblown fibers comprising a plasticized poly(vinyl chloride) composition which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly-(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, said composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load.

2. The meltblown fibers of claim 1, in which said nonvolatile plasticizer is present at a level of from about 30 to about 60 percent by weight.

3. The meltblown fibers of claim 1, in which said poly(vinyl chloride) has an inherent viscosity of from about 0.5 to about 1.4.

4. The meltblown fibers of claim 1, in which said composition has a melt flow rate of from about 50 to about 500 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load.

5. The meltblown fibers of claim 1, in which said composition has a melt flow rate of from about 100 to about 300 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load.

6. The meltblown fibers of claim 1, in which said plasticized poly(vinyl chloride) composition contains a heat stabilizer.

7. The meltblown fibers of claim 6, in which said heat stabilizer is present at a level of from about 0.1 to about 10 percent by weight, based on the amount of poly(vinyl chloride) present in said composition.

8. The meltblown fibers of claim 6, in which said heat stabilizer is present at a level of from about 1 to about 3 percent by weight, based on the amount of poly(vinyl chloride) present in said composition.

9. The meltblown fibers of claim 1, in which said fibers have an average diameter of from about 0.1 to about 300 micrometers.

10. A meltblown nonwoven web comprising a coherent matrix of meltblown fibers formed from a plasticized poly-(vinyl chloride) composition which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, said composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load.

11. The meltblown nonwoven web of claim 10, in which said nonvolatile plasticizer is present at a level of from about 30 to about 60 percent by weight.

12. The meltblown nonwoven web of claim 10, in which said poly(vinyl chloride) has an inherent viscosity of from about 0.5 to about 1.4.

13. The meltblown nonwoven web of claim 10, in which said composition has a melt flow rate of from about 50 to about 500 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load.

14. The meltblown nonwoven web of claim 10, in which said composition has a melt flow rate of from about 100 to about 300 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load.

15. The meltblown nonwoven web of claim 10, in which said plasticized poly(vinyl chloride) composition contains a heat stabilizer.

16. The meltblown nonwoven web of claim 15, in which said heat stabilizer is present at a level of from about 0.1 to about 10 percent by weight, based on the amount of poly-(vinyl chloride) present in said composition.

17. The meltblown nonwoven web of claim 15, in which said heat stabilizer is present at a level of from about 1 to about 3 percent by weight, based on the amount of poly-(vinyl chloride) present in said composition.

18. The meltblown nonwoven web of claim 10, in which said fibers have an average diameter of from about 0.1 to about 300 micrometers.

19. Poly(vinyl chloride) fibers prepared by:
(A) meltblowing a plasticized poly(vinyl chloride) composition which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, said composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load; and (B) extracting with a solvent at least about 80 percent of the plasticizer present in the meltblown fibers.

20. A nonwoven web comprising a coherent matrix of meltblown fibers formed from a plasticized poly(vinyl chloride) composition which comprises a mixture of from about 20 to about 80 percent by weight of a nonvolatile plasticizer and from about 80 to about 20 percent by weight of a poly-(vinyl chloride) having an inherent viscosity of from about 0.3 to about 1.6, said composition having a melt flow rate of from about 10 to about 105 grams per 10 minutes when measured in accordance with ASTM Method D 1238 at 190°C under a 2.16-kg load, which web has been extracted with a solvent after formation to remove at least about 80 percent of the plas-ticizer originally present in the meltblown fibers comprising the web.