CA1308892C

CA1308892C - Fibrillated fibers and articles made therefrom

Info

Publication number: CA1308892C
Application number: CA 549203
Authority: CA
Inventors: Robert Domenico Giglia
Original assignee: American Cyanamid Co
Current assignee: Wyeth Holdings LLC
Priority date: 1986-10-14
Filing date: 1987-10-14
Publication date: 1992-10-20
Anticipated expiration: 2009-10-20
Also published as: DE3788776T2; DE3788776D1; JPH09242000A; JP2927349B2; JP2941806B2; EP0265762A1; US4929502A; EP0265762B1; JPS63190100A; ATE100158T1

Abstract

FIBRILLATED FIBERS AND ARTICLES MADE THEREFROM
ABSTRACT

This invention relates to fibrillated fibers having particular physical characteristics, articles made therefrom as well as methods of producing the same. In particular the fibrillated fibers are defined by their Canadian Standard Freeness in combination with their Tensile Strength when formed into a sheet.

Description

-` 1 3088q2 FIBRILLATED FIBERS AND ARTICLES MADE THEREFROM

BACKGIIOUND OF THE INVENTION

The fibrillation of fiber , fibrillated fibers and their uses are well-known to those skilled in the art. For example, U.S. 2,810,646 to Wooding et al discloses a water laid web comprising filtered, heat~bonded, water-fibrillat~d, wet-spun filaments. The filaments are of a polymer selected from the group consisting of polymerized acrylonitrile and ~a copolymerized mixture of acryloni~rile and up to 15%, by weight, o~ at least one other monomer copolymerizable~
therewith.~ U.S.~4,495,030 to Giglia discloses~ the use~
of a fibrillated fiber to provide cohesi~ene s and :
support to:a wet-laid sheet containing active carbon and~
submicron glass~fibers. U.S. 4~565,727, also to Giglia, discloses the: use o~ a fibrillated ~iber to provide cohes~veness: and support to a wet~laid sheet containiny active carbon:in the fo~m of carbon fibers and carbon particles. ::

~ 25 Various nonwoven structures using a : ~ fibrillated acrylic ~iber were disclosed in ~Giglia et : al; :Novel Nonwoven Activated Carbon Fiber Papers ` ~:: : :

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~ 30~iq2 presented to a maeting of the American Chemical Society in April of 1984.

Recently, there has been much interest in the possible use of nonwoven fabric technology to produce paper and felt like structures co~taining activated carbon for use in chemical protective clothing and filtering applications inc:Luding both gas and liquid ~iltering. The a~orementioned Giglia paper described several nonwoven adsorptive felt like structures having loadings of activated carbon fibers or powders. In that paper it was disclosed that a fibrillated acrylic fiber, produced according to the process set forth therein, was useful in permitting high loadings o~ filler materials, such as activated carbon fibers and powders in the nonwoven ~abric while maintaining good wet strength and chemical resistance.

While many binding agents have been available in the past, fibrillated fibers are becoming of interest as they provide fine diameter fibrils as opposed to those of heavier spun ~iber~. Generally, spun fibPrs are produ~ed in sizes o~ ten microns or qreater while it ~ ha been the experiance that sizes of less than a micron -~ 25 (cross section) are required to entrap and bind fine particles in nonwoven and other composite structures.
Need exists now, however, for binders which provide such entrapment properties which aIso pro~ide reinforcement and strength to composite constructions. While the fibrillated fibers o~ the prior axt have provided adequate and improved characteristics, recognized needs for further improvement in this field are apparent and a welcome contribution to the art would be a fibrillated fiber having highly desired physical characteristics of low Canadian Standard Freeness in combination with relatively high ~ensile Strength. Hereto~ore, the .
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limits of these properties in the area of a~rylic fibers ha~ been such that fibrillated acrylic fibers have not been available with a Canadian Skandard Freeness below about 200 and certainly not available in ~ombination with a useful Tensile Strength such that the material could be processed on conventional nonwoven fabric lines. ~hese and other shortcomings of the prior art have been remedied by the discovery of the instant invention which will be described herein as follows.
SUMMARY OF THE INVENTION
The instant invention provides for a monoethylenically unsaturated monomer based fibrillated fiher wherein said fiber has a Canadian Standard Freeness tCFS~ of less than 200 in combination with a ~ensile Strength (TS), as will be defined herein, of at least 5 pounds per inch and preferably a CSF of less than 100. A
preferred base fiber is of an acrylic nature with especially desirable fibers having acrylonitrile contents of at least 85%
(based on weight of acrylonitrile monomer content to total monomer content of the prepolymerization mixturel. Particularly use~ul, fibers have polyacrylonitrile content in excess of about 89~ and more preferably, between ~9 to 90% on the same basis a~ set forth above. The preferred comonomers comprise methyl methacrylate which is preferably present at levels of at least about 10% by weight as discussed above. Other comonomers may be used wlthout limitation provided that their inclusion does not materially detract from the ability of the ~iber to be fibrillated nor w~th the properties of the fibrlllated fiber produced. Compatibility of such other monomers can easily be determined by one skilled in the art by simple experimentation.

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Extremely useful, fibrillated ~ib~rs and preferred for certain uses include ~ibers having a CSF
of less than about 50 and/or a TS of at least about 7 pounds per inch. Fibrillated fibers having CSF of less than about 25 are very desirable providing fabrications of extreme utility.

Included within the scope of the invention are nonwoven fabrics made with the fibers summarized above and in particular, nonwoven fabrics further comprising a toxic vapor absorpti~e agent: including, but not limited to, activated carbon. In several uses said activated carbon can comprise activated carbon fiber alone or in combination with a powder form present in said fabric at levels of up to about hal~ the weight of the ~abric, i.e. ths total fabric including all components including the activated carbon. Such fabrics can furthar comprise other fibers including, but ~ot limited to, up to about two fifths, by weight, of glass fibers. In cases where CSF values for the fiber are less than lO0, amounts o~
activated carbon as described above may conveniently exceed hal~ the weight o~ the fabric and in fact, can preferably exceed more than three quarters the weight of the fabric and more desirably in excess of about six sevenths and se~en eighths, by weight, of the fabric.

Preferable ~abrics independent of their composition are permeable to air and water vapor and provide improved components for such things including, but not limited to, breathing masks, garments and filtration syetems.

Generally, sheets comprising about 5% to about 65%, by weight, of the fibrillated fiber can be used to bind powdexs, flakes and fibexs of varlous sources and descriptio;ns. These materials include, but are in no : : ' : , . , , 1 ~08~392 way limited to, the activated carbon materials discusses above as well as other synthetic (organic and inorganic, i.e. glass, silicon, boron or the like) and natural fibers, powders, metallics, minerals and the like.
These materials may be in sheets or may also be in the form of pellets or, for example, pressed powders or any other form wher~by the inclusion o~ the fiber provides improved integrity of structure.

Figure 1 Graphic Representation o~ Data of Example 1 CSF
Figure 2 Photomicrograph Example 1 Representative 15Fibers 15 min.
Figure 3 Photomicrograph Example 1 Representative Fibers 25 min.
Figure 4 Photomicrograph Example 1 Representative Fibers 35 min.
20Figure 5 Photomicrograph Example 1 Representative Fibers 45 minO
Figllre ~ Graphic Representations of Data of Example 2 CSF
Figure 7 Graphic Representations of Data of Example 2 TS
Figure 8 Photomicrograph Example 2 Representative Fibers 20 min.
Figure 9 Photomicrograph Example 2 Representative Fibers 35 min.
Figure 10 Photomicrograph ~xample 2 Represent~tive Fibers 60 min.
Figure 11 Photomicrograph Example 2 Representative Fibers 75 min.
Figure 12 Photomicrograph Example 2 Representative 35Flbers 90 min.

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1 30~q2 (Description of Fiqures Continued) Figure 13 Graphic Representation of Data of Example 3 CSF
Figure 14 Graphic Representation of Data of Example 3 TS
Figure 15 Photomicrograph Example 3 Representative Fiber 50 min.
Figure 16 Photomicrograph Example 2 Representative Fiber 70 min.
Figure 17 Photomicrograph Example 2 Representative Fiber 90 min.
: Figure 18 Photomicrograph Example 2 Representative Fiber 110 min.
Figure 19 Photomicrograph Example 2 Representative Fiber 15130 min.
Figure 20 Photomicrograph Example 2 Representative Fiber 150 min.
Figure 21 Graphic Representation o~ Data of Example 4.

DETAILED DESCRIPTION OF THE_INVENTION
' `~ The fibrillated fibers o~ the instant ~: : invention: comprise in combination a Canadian S~andard 25Freeness of less than 200 in combination with a Tensile Strength of at least 5 pounds per inch as will be hareinafter defined~

: Canadian Standard FreenesR is measured as i5 30described in a test set forth in an article entitled : "The DetermiDotion of Freeness" Standard C.1, Approved ~: Method, October 1940, Revised May 1952, October 1962, September 1967, June 1969 and April 1972, prepared by the Physical and Chemical Standards Co~mittee, Technical Seotion, Canadian Pulp & Paper Associates.

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1 30~92 Tensile Strength is mea~ured according to Federal Standard l91A TM 5100 as follows:
0.63g (Dry Weight) of the fibrillated fiber is slurried in 200 ml of water. This slurry is then added to a 12.5 cm ID Buchner ~unnel containing a liner of No. 1 Whatman filter paper. Vacuum is used to form a test sheet on the filter paper layer. The test sheet is then separated from the ~ilter paper support and is dried to constant weight in an air oven at about 110C. The resulting sheet is then cut into 1.0 inch strips which are e~aluated for tensile strength to break according to Federal Standard l91A TM 5100.

Preferably, ~ibrillated fibers having a CSF o~
below 100 and/or a Tensile Strength o~ a~ least 7 pounds inch are particularly useful, and ~ibers having CSF
values below about 50 and 25 are found to have desirable and very desirable characteristics, respectively.
With regard to the ~iber from which these fibrillated fibers are made, acrylic based fiber~ are pre~erable. In particular, those in which the acrylonitrile monomer ~on~ribution is at least ~5%, by weight, of the fiber. By monomer contribution is meant the weight of the monomer employed in the reaction mixture ~ased on the total weight of all monomer contained therein just prior to initiation of the polymerization. Fibers with higher acrylonitrile monomar contribution ara particularly preferred.
Acrylic contents in excess o~ 89% are desirable and particularly preferred are composition~ where the ~ content is about 89 to 90 percent. While any compatible `~ comonomer may be used, methyl methacrylate has been found to be particularly suitable especially when i s monomer contribution is at least 10%, by weight.

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Inclusion of other comonomers can be made with simple experimentation based on the ancillary properties that they can provide provided that their inclusion does not materially detract from the ability to achieve the aforestated CSF and TS values critical to the instant invention. Without wishing to be bound by the theory, it is believed that fibers useful in producing the ~ibrillated fibers of the instant invention are those wherein the comonomer mix provides a fiber having lateral weakness and longitudinal strength. When using ~crylic fibers, the preferred form of the invention the ~ibrillated fiber pr~cursor can be made by conventional wet-spinning methods. In the best mode contemplated at the time of the filing of this application: wet~6pun, gel, hot-stretched and uncollapsed acrylic fiber~
comprising about 90%, by weight, and 10~, by weight, acrylonitrile and methyl methacrylate monomer contributions are employed. Specifically, contemplated comonomers that al50 may be use~ul include okher similar acrylates, surh as, fox example, ethyl acrylate.
Similarly, homopolymers and copolymers of other fiber forming monoethylenically unsaturated monomers, ~uch as vinylacetate, vinyl chloride, styrene, vinyl pyridine, acrylic esters, acrylamide and the like are within the scope of materials contemplated herein. Examples o~
still other copolymerizable monomers which are contemplated include those as described in U.S.
3,047~455.

The fibrillated fibers of th~ instant invention can be made using a modified commarcial blender. In general, it has been found advantageous to use a modified Waring brand commercial blender wherein the as suppli2d blade has been modified to provide a break edge o~ about 0.25mm on the working edge. In operation a relatively dilute slurry or precursor fiber . . .
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g in water is introduced into the blender device which is then run for about at least one-half hour to about at least one hour depending upon the molecular weight o~
the fiber being used. With acrylic fiber having what is considered a high molecular weight, i.e. ca. 58,000, a process time as short as one-half hour was found to be adequate while with a material of what is considered a low molecular weight, i.e. ca. 49,000, a minimum of about an hour was required. For the invention the exact time of processing is not critical and will vary with the character and make-up of the precursor, i.e.
molecular weight and monomer content and will be ea~ily determined in view of this disclosure by simple experimentation. What has been found to be critical was control o~ the tempPrature of the slurry while ~t was being processed. In prior art techniques, and as will be demonstrated in the Examples to follow, no attention was paid to the heak of the slurry mixture.
Irrespective of the normal starting temperatures, i.e.
room temperature, the mechanical action of the processing resulted in imparting heat energy to the slurry and sluxry temperatures in excess of about 50C
were experienced. Fibers produced thusly had CSF levels of about ~ive-hundred to seven-hundred, and values of less than that were unable to be achieved prior to loss o~ u~e~ul Tensile Strength as defined by these improved fibers. Importantly, it was discovered that by providing means to maintain the temperature o~ the slurry in a lower range that khe fibrillated fibers of the instant invention were obtainable for the ~irst time. In general, slurry temperatures, when using thi~
technigue maintained below about 30C, produced fibers within the scope of the instant invention. It is contemplated within the scope of the invention that variation of the slurry temperature in and around 20-30C using th2 aforedescribed technique alone or in .:

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~ 0~8 92 61109-7579 combination with variations of slurry solids content will enable in~inite variation of the critical parameters of CSF in combination with TS as may be required for the end use of the fibrillated fiber.
It is recognized that use of the commercial blender as described above is somewhat limited with regard to the amount of the fiber of the invention which can be produced in any one batch. It has been found that larger amounts of the. material can be produced using larger equipment. It is cautioned that many conventional cutting and beating devices have been attempted to date that do not produce Piber within the scope of that of the instant invention. It has been found that wh~n a Daymax* brand l0 gallon mixer was modified as per the mod~ication on the smaller Waring device Ii.e. -0.25mm break edge modification) 0.7%
slurries of precursor maintained below 30C and processed for about four hours produced ~ibrillated fiber within the scope of the invention.
Optionally, it has been found that use of a dispersant during processing, such as, for example, Aerosol~ OT 75, as available from American Cyanamid Company, wayne, New Jersey, or any similar such material facilitates the processing. The exact blending parameters or the equipment employed are not limiting ~ with regard to the scope of the invention and it is ; contemplated that such may be varied and modified with simple experimentation by one skilled in the art in view of this disclosure.

In accordance with the present invention, ~` there is also provided an improved fabric comprising said fibrillated fiber alone or in combination with preferably a toxic absor~ing agent or filtration material. In uses where said fabric will act as an * Trade-mark ` iP~

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, -1 30~892 element in a filtration system, it is preferable that said ~abric be permeable to air and water vapor.
Included within the scope of the filtration and toxic absorbing agents are activated carbons either in fiber or powder form or in mixtures thereof either alone or in combination with other agents. In one preferred mode the improved products of the present invention are prepared by wet-laying the activated carbon fibers, activatèd carbon particlee~ and fibrillated acrylic fibers from a water suspension thereof. The suspension should contain from about 1-15%, by weight, based on the total weight of fibers and particles, pre~erably from about 1-5%, by weight, of the fibrillated acrylic fibers, from about 6-75~, by weight, same basis, preferably from about 10-65%, by weight, of the activated carbon fiber and from about 15-8S%, by weight, same basis, preferably from about 20-70~, by weight, of the activated carbon particles, the total weight of the three components being 100%.
The activated carbon particles, activated carbon fiber and fibrillated acrylic fiber are wet-laid using th~ con~entiona~ paper-making process well known in the art. Flocculating agents and surface active agents can be incorporated into the water suspension in order to facilitate the paper-making procedure a is also known in ths art. The bulk of the acrylic fibrillated fib rs should range from about lmm to about lOmm in len~th.
The activated carbon fibers are also well known in the art as are methods for their production.
They can be used in lengths o~ ~rom about 0.3 to about 15.0mm, preferably ~rom about 0.5 to about lO.Omm, and can be pr~epared from such carb~n ~iber precursors as coal tar pitch, petroleum pitch, coal tar, petroleum .. ~ '' ~

: -- - 1 3n~892 derived thermal tar, ethylane tars, high-boiling coal tar distillates, ethylene tar distillates, gas oils or polynuclear aromatics. Also useful as precursors are polymers, such as acrylonitrile ho~opolymers and copolymers, polyvinylalcohol, phenolic-aldehyde and natural and regenerated cellulose. Methods for preparing activated carbon fibers useful herein are disclosed in U.S. 4,069,297 and 4,285,831.

The activated carbon powder or particles have a particle size ranging from about 0.1 to about 500 , preferably from about 1.0 to about 80 and are also prepared from any of the carbon precursors described above.
The wet-lay sheet making process tpaper making) used herein for the production of the novel fabric material of the present invention results in a product having uniquP sorptive characteristics, a thickness of at least about 0.005 inch, preferably at least 0.01 inch, a high sorptive capacity to weight ratio and high porosity to fluid flow. The equilibrium loading of absorptive carbon fiber is higher than conventional activated carbon powder products. The products of the present invention are more porous than sheets containing only carbon particles. The carbon fiber, which tends to lay parallel to the plane of the sheet, produces a longer fluid flow path through the sheet which increases the time available to adsorb impurities. The novel products hereof accept an unexpectedly high additional loading of active carbon powder. The combination of active carbon fiber and ;~; active carbon particles results in a higher performance versus cost ratio than sheets which contain only one of these active ingredients.

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1 308~2 The surface o~ the novel fabric matçrial of the present invenkion may ~e embossed during or a~ter its production to improve sheat flexibility and/or porosity. The novel nonwoven fabric material may be laminated to a woven, nonwoven, knitted etc. backing, such as matts, felts, papers, etc. produced from cotton, hemp, flax, ramie, jute, silk, wool, leather, flannel, flannellette, swansdown, poplin, cellulose ethers or esters, nylon, rayon, acetate~, polythene, glass, rock wool, asbestos, in order to strengthen the material.

Lamination of the novel products hereof to the above-mentioned backing materials may be achieved by the use of water ~apor and air permeable adhesives, preferably those available in the form o~ ~oams, such as rubber or acrylic latexes, polyurethanes and the like.
These adhesives are self-adhering and upon curing foam and set into strong bonds.

20~he sur~acs o~ the novel fabric material claimed herein may be rendered hydrophobic by coating with a porous silicone film or a polymar, such as ; polytetrafluoroethylene. Additionally, a reactiYe coating capable of decomposing toxic agents, e.g. a 25coating of a sulfonated polymer to hydrolyze nerve gas, may be applied therato so that the activated carbon particles and fiber~ form a second line o~ dsfense.

The fabric mat~rial of the pr~sent invention 30has a wide variety of uses. It is useful for protective purposes and for ~iltration and separation of gases and li~uids. The uses include the manufactura of the fabric material into wearing apparel, e.g. military uni~orms, blan~ets, sleeping bags, bedding, suxgical dressings, wrappers and containers, covers, tarpaulins, tents, curtains, gas masks~ paint spraying masks, ' ~ . ' . ' ' .:
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air conditioning duct filers, flue gas deodorizers and the like.

In general when fibers of the instant invention are employed having in combination CSF and TS
values of less than two-hlmdred and five pounds per inch, it has been found that up to abou~ one half o~ the resulting fibers weight can conveniently comprise : activated carbon either in fiber or powder form. When the CSF value is reduced to below about 100, sven higher : loadings can be obtained. In increasing desirability the activated carbon component of the fabric system can comprise more than one half to three fourths of the fabric, by weight, and most desirably to in excess o~
sixth seventh and even seven eighths o~ the total fabric weightO Additionally, major proportions of other fibers (i.e. glass up to about two ~ifth6, by weight) and materials may be incorporated to provide ~ther desirable qualities to the fabric.
In addition to the critical parameters of the ~ibrillated fiber of ~he instant invention, the fibers are further characterized by the following examples and related graphs and photomicrographs derived therefrom which are provided for illustration only and are not to be construed as l~mitations on the present invention except as set forth in the appended claims. All parts and percentages are as defined above unless otherwise specified.
EXAMPL~ 1 COMPARATIVE BASISl , .
: A commercial Waring bl~nder having a capacity of one ga:Llon in the ~landing chamber was modified by providing about a Q.25mm break edge on the workiny edges :

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1 308~92 of the blade. Next a slurry of an acrylic fiber, about 0.56%, by weight, was made up in two liters of water to which was also added 2ml of a solution of O.lmg/lOOml of Aerosol~ OT-75. The pa:rticular fiber, having a molecular weight of about 58,000, used was that sold by American Cyanamid Company under the designation o~ T-98 and had an acrylonitrile content of 89.2% and a methyl methylacrylate contsnt of 10.8~. The staple before processing had a lPngth on average of about three~eighths inch and a denier of about 5.4. The suspension was then charged to the blender and waa then processed for a period of forty-five minutes. Aliquotes were removed from the process slurry at 15, 2~, 35, and 45 minutes and the temperature of the slurry wa3 noted.
The resulting fibrillated fiber from each aliquote was ev~luated for CSF and TS as indicated in the body of the specific~ ion abo~e. In particular, TS wa~ made on a 100% shaet of 50.9g/m2 basis weight ~ormed by adding about 0.63 grams (Dry) of the fibrillated fiber in~200ml water to a 12.5cm lD Buchner funnel containing a liner of No. 1 Whatman filter paper under vacuum. Once the : tes~ sheet was separated ~rom the liner ~nd dried, it was cut into one inch strips a~d evaluated.

The resulting data is set forth in Table 1 and is graphically depicted in Figure lo As will be seen CSF values of the normalized plot were within the range of about five to seven hundred. The single point at thirty-five minutes is believed to be an anomaly a~d in any event had a value in excess of ~25. Additionally provided as Figures 2, 3, 4 and 5 are photomicrographs of the resulting fibrillated fibers corresponding ; respectively to the 15, 25, 35 and 45 minute aliquotes each magnified to the same scale tnote raference for scale comparison) showing the results of the fiber processing.

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,. 1 3088q2 EX~MPLE 2 The procedure of :Example 1 was repeated with the following modifications:
a) The Waring blender was fitted with a water cooling device such that the temperature of the slurry could be maintained between 24C and 30C during processing.
b) The blender was charged with a slurry containing 21 grams o~ fibar in three liters of water (i.e. consi~tency 0.7%) to which was added - lml of the dispersant solution.
c) The blender was op.erated in the low ~peed mode for ninety minutes and ali~uotes and temperature readings were taken after the 20th, 35th, 60th, 75th and 9Oth minute of processing, which samples were evaluated as before.
Raw data is shown in Table 1 and is graphically represented in Figures 6 (CSF) and 7 (TS) with Figures 8 through 9 being the photomicrographs of representative fibrillated fibers ~rom the 20th through 90th minute ~: aliquotss, respectively. As will be sPen from the graphic representations of the data, the critical combinations of low Canadian Standard Freeness and high Tensile Strength were achieved with processing times : ~ graater than about one-half hour.

EXAMP~E 3 : 30 The procedure of Example 2 was repeated with the single excsption (aside from processing times as shown) that a lower molecular variant (mw-49 9 0~0) of the fiber was employed. Samples and temperatures were taken after the 50th, 70th, 9Qth, 110th, 130th and 150th .~ 35 minutes of proce~sing~ Raw data is presented in Table 1 and i~ graphically represented in Figures 13 ~CSF) and :
' 14 (TS) with Figures 15 through 20 being the photomicrographs of representative fibrillated fibers from the 50th through 150th minute allquotes, respectively. As will be seen ~rom the graphic representations of the data, the critical combination o~
low Canadian Standard Freene.~s and high Tensile Strength were achieved with processing times greater than about one hour.

The mixer blade of a Daymax 10 gallon mixer was modified as per the modification o~ the Waring blender in Example 1. The mixer tank was then charged with about seven gallons of a slurry o~ the same fiber and concentrations of Example 3. As will be seen from Figure 21, a graphical representation o~ the raw data shown in Table 1 (running times of 2, 21/2, 3, 31/2 and 4 hours) at the end o~ four hours CST dropped to 70 and Tensile Strength was 11 lbs/inch, well within the critical limits defined herein. During the run, temperaturs was maintained vis-a-vis the application of about 501bs of ice per running hour.

EX~MPLES 1 - 4 Example RunningTemp CSF Tensile No Time oC ml. lbs/inch - _ 1 15 min 40 730 ---230 6.0 -:, 1 308~92 (Examples 1 - 4 Continued) Example RunningTemp CSF Tensile No. Time oC ml. lbs/inch 2 20 min -- 290 2.1 9.4 -~ 60 26 29 9.7 ~7 8 16.3 go -- 38 12.9 3 50 min <30 768 ---<30 142 1.8 ~30 28 9.7 110 ~30 2~ 6.9 130 <30 14 12.1 150 <30 8 7.4 4 2 hrs 26 750 ---4 - 70 11~4 : A mixture of 14% fibrillated acrylic ~ibers, 18% activated carbon ~iber and 68~ acti~ated carbon powder in 18 1. of water is formed into a sheet using a : 30 standard hand paper making ~achine. Th~ sheet is dried under pressure at 70C to 120C. The re~ultant fabric material is affective for the removal of toxic materials ~ rom vapor passed through it.

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: , 1 30~q2 The procedure of Example 5 i~ again followed, except that 12% fibrillated acrylic fiber, 59~ activated carbon ~iber and 29% active carbon powder are employed and the paper material is embossed after forming but before drying. The resulting fabric material is effectiv~ for the removal oi~^ toxic materials from vapor passing through it.

The procedure of Example 6 i8 again followed, except that the fabric material is not embossed. After drying the material is laminated to a 65/35 polycotton fabric utilizing a commercially available acrylic foam adhesive. The resulting product is effective for the removal of toxic mat~rials from vapor passing through it.

The procedure of Example 5 i~ again followed, except that 45% ~ibrillated acrylic fiber a~d 55%
~5 activated carbon powder are employed. No activated carbon fibers are pres~nt. The resulting fi~er is ef~ective at removing toxic materials ~rom vapor pa~sing through it.
~ EXAMPLE 9 The procedure of Exam~le 6 is again followed, except that 6.3% fibrillated acrylic fiber and 93.7%
activated carbon ~iber are employed. No activated carbon particles are present. The re~ulting ~abric material is effective at removing toxic material from vapor passing ~hrough i~.

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EX~MPLE 10 The procedure of Example 5 is again ~ollowed, except that 19.4% fibrillated acrylic ~iber, 80%
activated carbon fiber and 0.6% polytetrafluoroethylene are employed. No activatecl carbon powder is present.
The resulting material is ef~ective against removal of toxic vaporous material.

The procedure of Example 6 is employed, except that 6.3% of fibrillated acrylic fibers and 93.7% of activated carbon fibers are employed. No activated carbon powder is present. Two layers of the resultant fabric material are laminated as in Example 7~ The resulting product is useful for remo~ing toxic elements from air.

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Claims

1. A monoethylenically unsaturated monomer based fibrillated fiber wherein said fiber has a Canadian Standard Freeness of less than 200 in combination with a Tensile Strength of at least 5 pounds per inch.

2. The fiber of Claim 1 wherein said fiber has a Canadian Standard Freeness of less than 100.

3. The fiber of Claim 2 wherein said fiber is an acrylic based fiber.

4. The fiber of Claim 3 wherein the acrylonitrile monomer contribution to said fiber is at least 85% by weight.

5. The fiber of Claim 4 wherein a comonomer of said acrylonitrile comprises methyl methacrylate.

6. The fiber of Claim 4 wherein the acrylonitrile monomer contribution to said fiber is at least about 89%, by weight.

7. The fiber of Claim 6 wherein a comonomer of said acrylonitrile comprises methyl methacrylate.

8. The fiber of Claim 4 wherein the acrylonitrile monomer contribution to said fiber is about 89% to about 90%, by weight.

21a 61109-7579

9. The fiber of Claim 3 wherein a comonomer of said acrylonitrile comprises methyl methacrylate.

10. The fiber of Claim 3 comprising at least about 10%, by weight, of methyl methacrylate.

11. The fiber of Claim 1 wherein said fiber has a Canadian Standard Freeness less than about 50.

12. The fiber of Claim 1 wherein said fiber has a Tensile Strength of at least about 7 pounds per inch.

13. A fibrillated fiber wherein said fiber has a Canadian Freeness of less than about 200 in combination with a Tensile Strength of at least 5 pounds per inch and said fiber is a copolymer of a mixture of monomers comprising acrylonitrile and methyl methacrylate wherein said acrylonitrile contribution comprises at least 85%, by weight, of the monomer mix and said methyl methacrylate contribution comprises at least 10%, by weight, of the monomer mix.

14. The fiber of Claim 13 with a Canadian Freeness of less than about 100.

15. The fiber of Claim 14 with a Tensile Strength greater than 7 pounds per inch.

16. The fiber of Claim 15 with a Canadian Freeness of less than about 50.

17. The fiber of Claim 16 with a Canadian Freeness of less than about 25.

18, A nonwoven fabric material comprising a web-laid sheet containing the fiber of Claim 1.

19. The nonwoven fabric of Claim 18 wherein said fabric is air and water vapor permeable.

20. The nonwoven fabric of Claim 19 further comprising a toxic vapor absorptive agent.

21. The nonwoven fabric of Claim 20 wherein said toxic vapor absorptive agent is activated carbon.

22. The nonwoven fabric of Claim 21 wherein said activated carbon comprises activated carbon fiber and is present at a level of up to about one half, by weight, of said fabric.

23. The nonwoven fabric of Claim 22 further comprising up to about two fifths, by weight, of said fabric of glass fibers.

24. A nonwoven fabric material comprising a web-laid sheet containing the fiber of Claim 2.

25. The nonwoven fabric of Claim 24 wherein said fabric is air and water permeable.

26. The nonwoven fabric of Claim 25 further comprising a toxic vapor absorptive agent.

27. The nonwoven fabric of Claim 26 wherein said toxic vapor agent is activated carbon.
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28. The nonwoven fabric of Claim 27 wherein said activated carbon comprises activated carbon fiber and is present at a level greater than about one half, by weight, of said fabric.

29. The nonwoven fabric of Claim 28 wherein the level of said activated carbon exceeds about three fourths, by weight, of said fabric.

30. The nonwoven fabric of Claim 29 wherein the level of said activated carbon exceeds about six sevenths, by weight, of said fiber.

31. The nonwoven fabric of Claim 30 wherein the level of said activated carbon exceeds about seven eighths, by weight, of said fiber.

32. An improved air, liquid and water vapor permeable, toxic vapor absorptive nonwoven fabric material comprising a web-laid sheet containing fibrillated acrylic fiber and activated carbon, the improvement comprising said fibrillated acrylic fiber having a Canadian Standard Freeness of less than 200 in combination with a Tensile Strength of greater than 5 pounds per inch and wherein said activated carbon comprises activated carbon fiber present in said fabric at a level of about one half, by weight, of said fabric.

33. The fabric material of Claim 32 further comprising about two fifths, by weight, of said fabric of glass fiber.

34. An improved air, liquid and water vapor permeable, toxic vapor absorptive nonwoven fabric material comprising a web-laid sheet containing fibrillated acrylic fiber and activated carbon, the improvement comprising said fibrillated acrylic fiber having a Canadian Standard Freeness of less than 100 in combination with a Tensile Strength of greater than 5 pounds per inch and wherein said activated carbon comprises activated carbon fiber present in said fabric at a level greater than about one half by weight, of said fabric.

35. The nonwoven fabric of Claim 34 wherein the level of said activated carbon exceeds about three fourths, by weight, of said fabric.

36. The nonwoven fabric of Claim 35 wherein the level of said activated carbon exceeds about six sevenths, by weight, of said fabric.

37. A personal protection device incorporating the fabric of Claim 1.

38. The personal protection device of Claim 37 wherein said device is a breathing mask.

39. The personal protection device of Claim 37 wherein said device is a garment.

40. The personal protection device of Claim 37 wherein said device is a gas or liquid filtration system.