CA1093449A

CA1093449A - Disposable nonwoven surgical towel and method of making it

Info

Publication number: CA1093449A
Application number: CA277,138A
Authority: CA
Inventors: Benjamin E. Chapman; Danny R. Moore.; Arthur F. Phillips
Original assignee: Buckeye Cellulose Corp
Current assignee: Georgia Pacific Nonwovens LLC
Priority date: 1976-05-27
Filing date: 1977-04-27
Publication date: 1981-01-13
Also published as: SE7706175L; NL7705735A; DE2723141A1; FR2352664A1; NO143299B; US4075382A; BE855071A; DK236077A; IT1084072B; SE437928B; NO143299C; JPS5325091A; GB1574498A; FR2352664B1; NO771854L

Abstract

ABSTRACT OF THE DISCLOSURE
A nonwoven disposable towel, having particular utility as a surgical towel, comprising a five-ply structure and method of making it. The outermost plies of the towel are tissue. To each of these tissue plies there is adhered an intermediate ply constituting a medium density, thermoplastic, long fibered, nonwoven material. These tissue-intermediate ply assemblies comprise primary laminates accounting for four plies of the towel. Between these primary laminates there is located a fifth or center ply constituting a low density, melt blown,long fibered, nonwoven material. The entire structure is heat sealed about its periphery and additional spot heat bonds may be employed to minimize slippage between the center ply and the two primary laminates. The two primary laminates may be embossed prior to assembly of the towel.

Description

10~34~g BACKGROUND OF THE INVENTION
l. Field of the Invention . ~:
~ The invention relates to a disposable towel and its . method of manufacture, and more particularly to such a towel ~' . having particular utility as a surgical towel and comprising .
'- a unique five-ply structure includi~g three thermoplastic, ~ long fibered, nonwoven plies and two outermost tissue plies.
- ~ .

2. Descr1ption of the Prior Art . While the nonw,oven, disposable towels of the present .
~O ''invention may have many uses, they are particularly suited~
for use as surgical towels.and will be described in terms

3 of that application.. .
-In preparation for surgery, the surgeon.(as well as Z the scrub nurse and other members of the operating team? will ' exercise much care in scrubbing his hands and arms prior to ,, . entering the operating theatre. Then, after entering the operating théatre with his hands and arms still wet from the scrub, the . ~urgeon must exercise as much care.in the dry~ng of his hands 'a~ in the scrubbing operation itself to prevent any contamination ~ . . , . 0; of his now clean, but obviously not sterile, hands. While . .
! procedures vary 'from hospital-to-hospital and from doctor-to-doctor,' ~n general a towel is very carefully'manipulated by a surgeon '~ after ~crubbing so as to dry his hands without 'introducing any : contamination. Usually, one side of the towel is reservéd for ' ~S the drying of each han~ and separate portions of the towel are u~ed ~or each wiplng action. This avoids contamination from hand-to-han~. ~n view oE these procedures it is desirable tha~
~ tow~l ~Ci11-J u~c~l ~c1l1o11s~rzl~c~ liJ~illlUIII 0~ 1ooisturc s~rike s through-'' ' ' , ., ', ; , ' ' ' ~ , , ,.. . . . . . .
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',~ 10~'19 ~hile composite nonwoven surgical towels have been '~ substituted for the more common woven surgical towels, ~,- they have not met with universal acceptance. This is true ¦ not so much because they fail to perform adequately from ~' ~ . ............................................. .
7 the standpoint of absorbency, drying ability and the like, '~
'3 but largely becauae they lacked the bulk, softness, drape, surface feel and cloth-likeness of the traditional woven , . . .
', surgical'towel. Additionally,such composite nonwoven surgical towels gen~ally demonstrated',tco much strike through. Where steps were ) taken to prevent such strike through, the remaining characteristics listed above were even more lacking.
~t ' The présent invention is directed to a nonwoven disposable ,:~ , . . . . .
¦ towel having high absorptive capacity and excellent drying ~ - ability with a minimum of strike through. Typically, a surgeon ~'~
s; may have rom about 15 to about 20 grams of watér remaining

4 on hi~ hands and arms after the scrubbing operation. I
he is a large man, he may have as much as 30 grams of water remaining. The towel of the present inventio~ has an ab~orptive capaclty of about 4 to about 7 grams of water per gram o'f towel and weighs about 30 grams. Therefore, the towel .,~, . . . . . .
of the présent invention'has a capacitv of at least about 4 o~ 7 times the maximum amount o water to be absorbed ~rom the surgeon's hands and arms.
''` ' The towel o the present invention is substantially S low in llnt t-ndency, demonstrating excelient abrasion resistance, ' ~trength and sturdiness. At the same time, the towel is characterized by markedly improved appearance and surface feel.
The towel is soft, cloth-like and is further characterized by desirable bulk, good conformability and drape. Drape, for example, ;3 i~ needed to prevent contamination of the towel. I the towel is , too Rtlf it will have a tendency to rub against the surgeon's ' .

, . . . .

10~3449 scrub suit. This is also true if the towel, to provide sufficient absorptive capacity, must be made too long, too wide or both. Finally, the towel of the present invention may be easily and inexpensively manufactured and readily sterilized.
While particularly adapted for use as surgical towels, the nonwoven, disposable towel structures of the ~ ;
present invention may have many applications. For example, they may be used as professional towels or as hand towels or bath towels for hospital patients and the :
like. They may serve as disposable towels for use in hotels and motels or for use in institutions such as nursing homes, mental institutions, prisons and the like.
SUMMARY OF THE INVENTION
The present invention broadly relates to a disposable, sterilizable, surgical towel having a five-ply construction comprising a center ply of wettable microfibrous melt-blown fibers having a basis weight of from about 20 to about 60 grams per square meter and two identical primary laminates to each side of said center ply and each comprising an intermediate ply of wettable thermoplastic fibers having a basis weight of from about 10 to about 30 grams per square meter adhesively secured to a tissue ply having a basis weight of from about 10 to about 30 grams per square meter, said tissue plies comprising the outermost plies of said towel, said center ply and said primary laminates being bonded together about the periphery of said towel.

,, ~`' 10~3449 The nonwoven disposable towel of the present invention is made up of five plies. The outermost or surface plies are tissue plies. Various types of tissue may be used, as will be described hereinafter. Each -tissue ply has adhered to its innee or unexposed surface an intermediate ply of a medium density, thermoplastic, long fibered, nonwoven material. The two tissue-intermediate ply assemblies comprise what will be termed hereinafter: "primary laminates". Between the two primary ~ -laminates there is located a fifth or center ply of low density, melt-blown, long fibered, nonwoven material. The medium density intermediate plies and the low density center ply are preferably formed of melt-blown polypropylene. Since this material is hydrophobic in -nature, the center and intermediate plies of polypropylene are treated with a wetting agent to increase absorbancy.
The primary laminates are preferably subjected to hot or cold embossing andtor mechanical micro-compaction. This improves the surface texture, softness and appearance of the towel structure. When the primary lamln~tes include outer plies o ., .
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of cellulose t'issue, they are sprayed or coated on their tissue side with a material commonly used as wet strength resin to increase the wet abrasion resistance of the end product to withstand the hand and arm drying action of a surgeon, for ?
; example. The wet strength resin also ties down any loose cellulosic fibers.
When the primary laminates are located to~either side of the center ply, the edges of the towel structure are heat sealed, thereby joi~ing the primary laminates to the center 0 ply. To prevent shifting of the center ply with respect to ' the primary laminates during a drying and wiping action, r additional spot heat bonds may be made throughout the length and width of the towel structure, to'tally randomly or in a patterned arrangement which may additionally enhance the appearance of the towel. ' , BRIEF DESCRIPTION OF THE DRA~INGS
, Figure 1 is a plan view of the towel of th'e present invention. ' Figure 2 is a perspective view of the towel of Figure_lL_ _ and illu~trating the individual plies thereof, the thickness '0 of the plies being greatly exaggerated for purposes of'clarity.
.
Figure 3 is a fragmentary view diagramatically illustrating the cross section of the towel struc~ure.
;~ DESCRIPTION OF THE PREFERRED EMBODIMENTS
. .
~urning to the Figures wherein like parts have been given '5 llke indéx numerals, the towel of the present invention is generally lndlcated at 1. ~s is clear from Figure 2, the towel is made up of five plies. In Figure 2 the five plies have been exaggerated in thickness for purposes of clarity.
The outermost plies 2 and 3 are made of tissue. Tissue ~0 plies 2 and 3 are followed by intermediate plies ~ and 5 formed from medium density, thermoplastic, long fibered, nonwoven webs. Finally, the fifth or center ply 6, located between ,, . _ . __, . ...................... .

.. .

'' 1093'1~g ~ ., intermediate plies 4 and 5, is formed from a low density, melt-blown, long fibered, nonwoven web.
Each of the five plies 2 through 6 must have certain characteristics. The outermost tissue plies 2 and 3 must be characterized by fast strike through, abrasion ;~ ;
resistance, low linting tendencies, softness, flexibility, drape and wet strength. In addition, these plies should present a good visual appearance inclusive of surface -characteristics, texture and color, if a color is used. -Finally, the outermost plies should be characterized by an excellent tactile impression, again inclusive of surface characteristics, texture and the like.
The intermediate plies 4 and S should have a ; "
medium density. While other nonwoven materials may be used, -the intermediate plies 4 and S are preferably made up of ther~moplastic fibers heat sealable to the center ply 6.
Plie~ 4 and 5 must also be capable of adhesive bonding to outermo~t tissue plies 2 and 3. The intermediate plies ~hould be soft, flexible and possessed of adequate drape. ~-They should also permit fast strike through and be inherently j wetable or capable of being rendered wetable.
In addition to the characteristics listed for the ti~sue and intermediate plies, the primary laminates made ¦ therefrom should be embossable. Preferably, they should be heat embo5sable and heat setable. As a consequence of the characteristics of the tis~ue and intermediate plies making up each primary laminate, each primary laminate will display an adequate ability to absorb the stretch and I energy of a wiping action. They will have good visual f 30 appearance and tactile impression. Above and beyond the '~f necessary wet stxength, the primary laminates will be low in linting tend0ncies and .' . ,i' ' ' -- 10934~9 high in abrasion resistance. The primary laminates will permit fast strike through of moisture to the center ply.
The center ply serves as the reservoir for the moisture absorbed by the towel structure and should be in-herently wettable or capable of being rendered wettable.
It therefore should have high absorptive capacity and a wicking rate greater than that of the primary laminates.
The center ply should be bulky and of low density, soft, bendable and capable of adequate drape. The combination of absorptive capacity, wicking rate and bulk of the center ply 6 enables the towel structure to demonstrate a minimum of strike through from one outside surface to the other out-side surface. While center ply 6 may be made of any approp-riate nonwoven material it is preferably made up of melt- - -blown, nonwoven, long fibered material, heat bondable to the adjacent primary laminates.
Outermost plies 2 and- 3 may be made of any approp-riate tissue having a basis weight of from 10 to 30 g/m .
The tissue may be made from wet-strength paper, carded webs, air-laid bonded fibrous webs, spun bonded webs, wet laid cellulose webs containing some long cellulose or synthetic fibers, melt-blown polymer webs or the like. While not in-tended to be so limited, the plies 2 and 3 may be made of a wet ~trength cellulose tissue of the type taught in U.S.
Patent 3,301,746, in the name of Sanford, et al, dated January 31, 1967. Preferably a conventional cellulose tis~ue made on conventional tissue machines is used.
As indicated above, intermediate plies 4 and 5 are preferably made of thermoplastic fibers. They may be produced from spun bonded webs, for example. Preferably, they are derived from a medium density, melt-blown, long :, fibered, nonwoven web. Such melt-blown webs are taught, for example, in the article entitled SUPERFINE T~ERMOPLASTIC
FIBERS by Van A. Wente appearing in INDUSTRIAL AND ENGINEERING
CHBMISTRY, August 1956, Volume 48, No. 8 (pp. 1342-1346).
While the melt-blown material may be nylon, polyester, or the like, a melt-blown polypropylene web is preferred.
Where a melt-blown polypropylene web is used for imtermediate plies 4 and 5, the composition should be primarily linear polypropylene and the bonding should be medium. The web preferably has a basis weight of from about 10 to about 30 g/m2 and preferably about 15 g/m2. The web filaments should have a diameter of from about 1 to about 8 microns and preferably less than 4 microns. The web should be character-ized by a tensile strength of from about 5 to about 1.5 lbs./in., a minimum Elmendorf tear strength of at least about 20 g. in the machine and cross machine directions; a minimum elongation at maximum force of at least about 25% in the machine direction and at least about 35% in the cross direction;
and a low load density of from about .06 to about .09 g/cc.
~he low load density is determined in the following manner. The material to be tested is conditioned in a room maintained at 23 + 1C (73.4 + 2F) and 50 + 2% relative humidity for a minimum of twelve hours prior to testing.
The material to be tested must have an area large enough to provide a sufficient number of thickness measurements to accurately represent the material. Normally, five different locations will be sufficient to determine the average thick-ness of a nonwoven fabric material. The thickness is measured with a motorized, dead weight micrometer (having a total load of 300 g.) which lowers the micrometer anvil at a uniform `` 1093449 rate and pressure on the surface of the material. Five determinations are made on each sample. The median value is reported as the thickness in inches of the material.
The low load -7a-, 10~3~4~

density of a material is ~etermined by the following'calculation:
-Low Load Density g/cc = basis wt. in g/m2 ~ 0.0000394 thickness in inches ~, .
The center ply 6 is preferably made from a nonwoven web of any appropriate super fine melt-blown, long fibered material. , '" 5 ' Again, polypropylene is'preferred, the center ply~6 being a low density,lightly bonded ply having a composition ; - comprising primarily linear poIypropylene and having a basis weight of ~' ~ from about 20 to about 60 g/m2 and preferably about 30 g/m2.
Again, the~filàment diameter should be from about 1 to about '10 -8 microns. The ply 6 should be characterized'by a tensile , , . ~
'l ' strength less than 1.5 lbs./in. in both the machLne and cross '~ machine directions; an ~lmendorf tear strength of from about 80 to abou~ 300 g. and preferably 150-300 g. in both the ', 'machine and cross machine directions; a minimum elongation ~5 at maxlmum~force of about 35%'in the machine directlon and l~ about 50% in'the cross direction; and a low load density of ' '~s from about .05 to about .08 g/cc.
, i , . . . . . . .
~l Since polypropylene fibers are inherently hydrophobic, it is necessary that the nonwoven melt-blown polypropylene plies 4, 5 and 6 be treated with a wetting agent, as will be described herelnafter.

~, . .
The melt-blown polypropylene ply 4 is attached to ~, tissue ply 2 by an appropriate adhesive, as will be described ;', hereinafter. Similarly, the melt-blown polypropylene'ply 5 "~25 '' is affixed to tissue ply 3.

~' It has been found that by providing intermediate plies and 5 affixcd to tissue plies 2 and 3 (~cspec~iv~ly) and a loosc ~'~ center ply 6 free of adhesive or binder, thè resultant towel has .
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- a softness, resiliency, bulk, cloth-likeness and absorptive capacity far superior to prior art structures, as, for example, a structure wherein tissue plies are adheared directly to a single, central melt-blown polypropylene web.
The structure thus far described is bonded about its periphery, as at 7 in Figures 1 and 2. This prevents loose ~ fiber migration from plies 4, 5 and 6 and joins center ply 6 - to the primary laminates 2-4 and 3-5. While the structure may be adhesively bonded about its periphery, it is preferably heat sealed.
Where the towel of the present invention is to ' be used primarily as a wiping device (as in its use as a hand and arm drying surgical towel), it is preferable to further join the ~enter ply 6 and primary laminates 2-4 and 3-5 so as to pr~vent them from slipping or shifting with respect to . each other during the application of shear force resulting from a wiping action. Such ply slippage may be prevented by providing a plurality of discrete spot bonds of the center ply 6 and primary laminates 2-4 and 3-5. While adhesive spot bonding may be used, spot heat bonding is preferred. For purposes of an exemplary showing, the towel of Figure 1 is illustrated as having a plurality of individual spot heat bonds 8 arranged in rows 9. The rows 9, in turn, are arranged in a decorative "chevron" pattern . At the position of each ; individual spot heat bond, the towel structure is stiffened and its absorptive capacity is reduced. Nevertheless, when appropriately designed and positioned, the spot heat bonds will cause no appreciable effect on the softness, resiliency and drape of the overall towel structure and no significant effect on its absorptive capacity.
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, The length, width, size and shape of the individual spot heat bonds 8 may be varied, as may be the overall pattern thereof. The spot heat bonds may, for example, be ;. so positioned as to "channel" movement of moisture in the towel. In , :
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` ` 10934~9 addition to their functional purpose, the spot heat bonds 8 may also serve as decorative elements of the towel. Where the tissue layers 2 and 3 are colored, the individual spot heat bonds will have a darker shade. The effect provides a towel having a 2-tone coloring system of enhanced appearance.
It has also been found preferable to hot or cold emboss the primary laminates 2-4 and 3-5. For example, the primary .
laminates may be passed through the nip of a heated embosser having one steel en~raved roll and one soft back-up roll, as is known in the art. As a result of the embossing treatment, the primary laminates are partially densif1ed and rendered resistant to mild wet or dry expansive forces. The primary laminates are improved in tactile impression, softness, flexibility and surface character, the overall stiffness of the primary laminates being reduced.
~ Figure 3 diagramatically illustrates an idealized showing of ; the towel of the present invention with the primary laminates 2-4 and 3-5 having been hot embossed. The primary laminates ____ will have, as a result of the hot embossing, areas lO of high density 'h''20 ' and areas ll of low density. The heat used in the e~bossing step is~such that the areas lO are heat set but maintain their fibrous structure. This heat settin~ results in a structure which ~t retains its embossing under conditions of further processing, sterilization, high humidity and during use of the towel. As is to be expected, the absorptive capacity of the hot ; ~ embossed primary laminates, as compared to unembossed primary laminates, is decreased. Unexpectedly, however, it hns been Lound that the absorptive ca~acity of the total towel ; structure l is substantially increased when the primary laminates ;~ .
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^` " ` 1093449 . . .
' 2-4 and 3-5 have been hot embossed as compared to a total " , .
`' ' towel structure with unembossed primary laminates. The embossing ` of the primary laminates also improves the appearance and ! tactile impression of the towel. Another way to improve the appearance and tactile impression is to subject the primary laminates 2-4 and 3-5 to mechanical micro~-compaction (as for example taught ~ ~ .
' -in U.S. Patent ~,624,245, in the name of S. L. Cluett, and `` ! , . . `
' dated January 6, 1953) in lieu of or in addition to an ~embossing treatment.
Figure 3 also illustrates a sealed edge 7'of the towel ,' structure and a spot heat bond 8. In these areas 'the 'plies 4, 5 and 6 melt together and partially, at least, ~-. impregnate the tissue plies 2 and 3 as 1ndicated by hatch lines 2a and 3a.
, "''lS ' `The exterior surfaces of the towel (i.e. the tissue surfaces) '~' are preferably treated'with a wet strength resin when a cellulose tissue is used. This increases'wet abrasion resistance.
-. and tends to tie down loose'cellulosic fibers on the towel ~-~ surfaces. An application of latex could also be used for I,, . . these purposes, but care must be exercised to assure that such a latex application does not decrease the desired fast strike through of the primary laminates or deleteriously effect the tactile impression.
'~ In the manufacture of the towel of the present invention, the primary laminates 2-4 and 3-5 are assembled. Since the ' primary laminates are identical, it is only necessary to describe ~" the assembly of one. The tissue web or ply and the thermoplastic .
j ' intermediate web or ply are joinèd together by an appropriate '' binder. The binder should be soft, flexible, safe for use in '~30 the operating room and wettable. The binder is applied as a high viscosity solution to the thermoplastic, nonwoven intermediate ~' web by any appropriate means such as a padder, a gravure ~' roll applicator, a metering applicator or the like, minimum `!"
~, ;~ ' ' ' . ~ ' ` ' " -... . .
penetration of the thermoplastic, nonwoven intermediate web by the binder being desired. If the intermediate web is melt-blown, .. . . .
i the non-wire side has more loose fibers and is preferably, from a bond strength stand point, the side laminated to the tissue. The tissue and the thermoplastic nonwoven plies are - , .
brought to~ether under light pressure (of the order of about 60 pounds per linear inch) between laminating rolls. The ~; primary laminate is thereafter dried and cured on conventional steam .. . . . . .
~ heated dryer drums,~ a yankee dryer or the like. R hot air dryer . - . .. . . .
~110 or other conventional means may be used. The curing and drying , .,. . :
~ step should be conducted at a temperature such that the intermediate .. ,, . . ~, ~- plies- maintain their fibrous structure. The dried and cured :~ i . - .
pximary laminate may be-used directly in the further towel making process or rolled for subsequent use.
,, ~ , , . . . -" 15 ~ Approprlate acrylic latex binders are, for example, manufactured by Rohm & Haas Company, of Philadelphia, A Pennsylvania, under the designation E-751 ~ , hydrophillic acrylic polymer designed as a binder) or by B. F. Goodrich, ~,~ Chemlcal Company, of Cleveland, Ohio, under the trademark Hycar ~20 and deslgnation 2600x223 (a soft, hydrophillic, acrylic-,, ~ polymer aesigned as a binder). To control penetration of the latex into the thermoplastic nonwoven intermediate web and the tissue web, the viscosity and the percent binder ~5 solids should be high. The above mentioned binders are furnished with a solids content of about 46~ and about 50%, respectively.
Percentages as low as about 35% have been used successfully. To raise the viscosity of the binder to the desired level to control its penetration and thus improve bond strenath by confining the latex near the interface of the tissue and ~0 intermediate plies, a thickener suitable for use with the latex .~
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: 1093449 binder should be added. Sufficient thickener should be ~' added to obtain at least about a 7000 cps or greater viscosity.
; Viscosities as high as 40,000 to 60,000 have produced primary laminates of acceptable bond strength. Exemplary thickeners ~ 5 are manufactured, for example, by Rohm ~ Haas Company, of '` Philadelphia, Pennsylvania under the trademark ACRYSOL and the ' designations ASE 60 or ASE 75 (alkali-soluble emulsions ~, , , comprising acrylic polymers containing acidic functional groups). To the thickened latex binder ammonium hydroxide ''10 may be added to obtain a binder solution having a pH o 7 or greater. Finally, an antifoam agent may be added to improve , ",;.
the processability of the binder solution. Excellent '' results have been achieved, for example, through the use of ,. . .
~'' a silicone antifoam agent added in the range'of from 2 to 4 '15 grams per pound of binder solution. An exemplary'silicon antifoam agent is manufactured by General Electric, of ' Waterford, New York, under'the designation AF-72 (an aaueous emulsion of a dimethyl polysiloxane containing about 30% silicone solids~
; As mentioned above, most thermoplastic polymers used in nonwovens are generally hydrophobi_ and must be treated 'j~ with a wetting agent if they are to be hydrophillic as is '~ required for plies'2, 3, 4, 5 and 6. The term wetting agent as used herein is intended to encompass any chemical additive ' ' or treatment step rendering the thermoplastic nonwoven webs ~, " .
'25 hydrophillic. In the case of a chemical additive it may be -~ ' ' .:, . .
;' applicd in a numbor of different ways. Firs-t of all, the polymer may be treated as a part of the manufacturing process of the nonwoven webs. For example, a wetting agent may be ~'; added at the time the filaments of the web are formed.''Another '30 approach is to treat the already formed polymer filaments or nonwoven webs. Thus, that web from which center ply 6 is made may be , . ................... .

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:; 10~93~l49 dipped in a wetting agent bath and caused to pass between squeeze rolls, or the wetting agent may be applied by spraying. Thereafter, the treated web is dried over conventional steam heated drying drums or by other conventional drying methods.
The thermoplastic webs from which plies 4 and 5 are - formed (and piies 2 and 3 if hydrophobic in nature) can betreated in precisely the same manner before or after lamination to the tissue layer. Treatment of a thermoplastic web after its lamination to the tissue web is convenient because the laminate may be dipped in a wetting agent bath, caused to ; ,, .
pass through squeeze rolls, sprayed with a wet-strength resin (if required) and dried over conventional steam heated dryer drums. Thus the wetting agent and wet-strength resin treatments ~, can be accomplished in a single line.
,i:, . .
~15 As heretofore pointed out, one preferable thermoplastic nonwoven web suitable for plies 4, 5 and 6 is a melt-blown polypropylene web of filaments of average diameter of from . .~ . .
about 1 to about 8 microns and preferably less than 4 microns.
' With such a melt-blown poIypropylene web, excellent results have been achLeved through the use of a 0.~% to a 1.2%
:~~ application by weight of a wetting agent manufactu~ed by Textilana Corporation of Hawthorne, California, under the A ~r~le tn~QI~ -~ L ~4u~uuu~ Velvetex BCW (a biodegradable, chemically stable, :~' liquid coco fatty betaine). Excellent results have-also ~25 been achieved through the use of a 4% application by weight of .. ., a wetting agent manufactured by Emery Industries of Cincinnati, Ohio, under the designation 9886A (a liquid partial ester of polygIycerol). q'he above noted wetting agents not only 1 increase the absorbency of the melt-blown polypropylene webs and make them softer, but they also lower the surface ~`' , , ' ,, : 14 ~;,;' ,~.,"~ , . . .

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;: ~ 1093449 ` resistivity of the webs to an acceptable level (i.e., as described in NFPA standard 56A) for use in an operating room or the ., `` ! like.
An appropriate resin, such as a resin used as a wet strength resin in papermaking, may be used to increase the wet abrasion ~ resistance of the tissue plies, particularly in the case of cellulose -- tissues or tissues containing some cellulose fibers. Excellent results . . ' , .
~, have been achieved, for example, through the use of a wet strength `~ resin manufactured by Hercules Incorporated of Wilmington, ~, - .
Delaware under the trademark Kymene and designated 557H, as a 0.6% to 1.2% surface addition, based on lamina~e weight, applied to the tissue side of the primary laminates. Kymene 55iH
i8 a resin sold as a wet strength additive for paper making and is a cationic water soluble polyamine-polyamide epichlorohydrin. ~-. ' : i .
After treatment with the wetting agent and the wet strength resin, the primary laminates may be cold or hot embossed (by ~`i methods well known in the art) and/or sub~ected to-mechanical micro-compaction of the type taught in the ab~ve mentioned_ _ _ :~ U.S. Patent 2,624,245.
Final assembly of the towels of the present invention~
, . . . . . .
~' is accomplished by passing a web constituting center ply 6 and . -- .
web8 constituting primary laminate 2-4 and primary laminate , :: , . .
3-5 between deeply~relieved and heated sealing rolls for 8imultaneously forming the edge seals 7 and spot heat bonds 8, whilé not contacting the remainder of the towel structure.
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These rolls will seal individual towel segments whi-ch may thereafter be cut into separate towels. The same rolls may be used to provide a line of perforations between adjacent , i, ' ;) towels of the web so that the towels may be maintained in ii;,~.~ - -. . .
~ web form, but readily removed from the web, one at a time.
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~~~` 10~3a~4~

The towel structures of the present invention may be sterilized by any appropriatc method, either by the manufacturer ` or the user.
EXAMPLE
. . .
In the practice of the present invention a conventional wet strength cellulose tissue, having a basis weight of - ~about 15 g/m2, lS bonded to a medium density melt-blown ~,, polypropylene web having a basis weight of about 15 g/m2 with ~,.. . .
an appropriate late~ binder (~as described above) and dried Lo - ~and cured over conventionaI steam heated dryer drums. The . . .
primary laminate thus formed is dipped in a wetting agent bath, caused :". ~, .
to pass through squeeze rolls, sprayed with a wet strength , resin on its tissue side and thereafter clried over conventional steam heated dryer drums, again as described àbove. The primary laminate is then hot embossed.
~, ~ ~he résulting primary laminate is characterized by a basis weight of 38 gm/m2, excellent absorbency and strike through, a Klemm vertical wicking rate of 26~ in./min.,good _ _ drape and conformability, a lint release upon vigerous agitation ~0 in an air flow for 30 minutes of 10 mg/yd2 and a wet tensile strength (MD/CD) of 1.55/.90 lb./in.
~' Primary laminates of the type just described are iocated to either side of a center ply with the tissue side of the primary laminates outermost. The primary laminates and center ~5 ply are caused to pass between deeply relieved and heated sealing ~ rolls to form edge seals and spot heat bonds therebetween.
~, The center ply is preferably a low density ply of super fine, melt-blown long fibered polypropylene. The center ply is characterized by a basis weight of 30 g/m2, a Klemm vertical wicki~g rate of 28 in./min. and an absorptive capacity tl psi loading) of 6 g ~20/g web.

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1~93~49 The resulting finished products are in the form of towels 16 by 24 in. having an absorptive capacity (1 psi loading) of S.0 g H2O/g towel, a lint level of 20 mg/yd2 and an Elmendorf ~ear '~ strength ~f 200 g.
Towels thus made have all of the desired char~cteristics ~~ .
for use as a surgical towel discussed above, including absorptive capacity, bulk, softness, drape,'tactile impression, low ''; lint releast and the like.
.. ,r odifications may be made-i~ the invention without ~'10 departing from the spirit of it.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A disposable, sterilizable, surgical towel having a five-ply construction comprising a center ply of wettable microfibrous melt-blown fibers having a basis weight of from about 20 to about 60 grams per square meter and two identical primary laminates to each side of said center ply and each comprising an intermediate ply of wettable thermoplastic fibers having a basis weight of from about 10 to about 30 grams per square meter adhesively secured to a tissue ply having a basis weight of from about 10 to about 30 grams per square meter, said tissue plies comprising the outermost plies of said towel, said center ply and said primary laminates being bonded together about the periphery of said towel.

2. The structure claimed in claim 1 wherein each of said tissue plies is a wet strength paper tissue.

3. The structure claimed in claim 1 wherein said intermediate plies each have a basis weight of about 15 grams per square meter.

4. The structure claimed in claim 1 wherein said center ply has a basis weight of about 30 grams per square meter.

5. The structure claimed in claim 1 wherein said center ply and said primary laminates are additionally joined by a plurality of individual spot bonds so arranged as to minimize shifting of said center ply and said primary laminates when said towel is used with a wiping action and without significant effect on the softness and absorptive capacity of the towel.

6. The structure claimed in claim 1 wherein said primary laminates are cold embossed.

7. The structure claimed in claim 1 wherein said primary laminates are hot embossed.

8. The structure claimed in claim 1 wherein said tissue plies are wet strength resin treated plies.

9. The structure claimed in claim 1 wherein said fibers of said intermediate and center plies are wetting agent treated melt-blown polypropylene fibers.

10. The structure claimed in claim 1 wherein said center ply has an absorptive capacity and a wicking rate such as to minimize strike through from one outermost ply to the other outermost ply of said towel.

11. The structure claimed in claim 2 wherein said tissue plies have a basis weight of 15 g/m2.

12.The structure claimed in claim 5 wherein said tissue plies are wet strength resin treated plies and said primary laminates are hot embossed.

13. The structure claimed in claim 5 wherein said bond about the periphery of the towel and said spot bonds are heat bonds.

14. A disposable towel having a five-ply construction comprising a low density, soft, bulky, bendable, wettable, highly absorbent, nonwoven center ply and two identical primary laminates to each side of said center ply, each of said primary laminates comprising an inner ply and an outer ply adhesively adhered together, said inner ply comprising a medium density, soft, bendable, wettable, nonwoven ply, said outer ply comprising an abrasion resistant, low linting, soft, bendable, tissue ply, said primary laminates being characterized by fast strike through, said tissue plies comprising the outermost plies of said towel, said center ply and said primary laminates being bonded together about the periphery of said towel.

15. The structure claimed in claim 14 wherein said center ply has a basis weight of from about 20 to about 60 grams per square meter and said intermediate and said tissue plies have a basis weight of from about 10 to about 30 grams per square meter.

16. The structure claimed in claim 14 wherein each of said tissue plies is a wet strength paper tissue.

17. The structure claimed in claim 14 wherein said intermediate plies have a basis weight of about 15 grams per square meter and said center ply has a basis weight of about 30 grams per square meter.

18. The structure claimed in claim 14 wherein said center ply and said primary laminates are additionally joined by a plurality of individual spot bonds so arranged as to minimize shifting of said center ply and said primary laminates when said towel is used with a wiping action and without significant effect on the softness and absorptive capacity of the towel.

19. The structure claimed in claim 14 wherein said primary laminates are cold embossed.

20. The structure claimed in claim 14 wherein said primary laminates are hot embossed.

21. The structure claimed in claim 14 wherein said tissue plies are wet strength resin treated plies.

22. The structure` claimed in claim 14 wherein said fibers of said intermediate and center plies are wetting agent treated melt-blown polypropylene fibers.

23. The sturcture claimed in claim 14 wherein said center ply has an absorptive capacity and a wicking rate such as to minimize strike through from one outermost ply to the other outermost ply of said towel.

24. The structure claimed in claim 16 wherein said tissue plies have a basis weight of 15 g/m2.

25. The structure claimed in claim 17 wherein said tissue plies are wet strength resin treated plies and said primary laminates are hot embossed.

26. The structure claimed in claim 18 wherein at least one of said center ply and said inner plies is thermoplastic and wherein said bond about the periphery of the towel and said spot bonds are heat bonds.

27. A process of making a disposable, sterilizable, surgical towel having a five-ply construction comprising the steps of making primary laminate webs by adhesively bonding a first thermoplastic nonwoven web having a basis weight of from about 10 to about 30 grams per square meter to a second tissue web having a basis weight of from about 10 to about 30 grams per square meter, providing a third melt-blown microfibrous nonwoven web having a basis weight of from about 20 to about 60 grams per square meter, locating one of said primary laminate webs to either side of said third melt-blown microfibrous web with the thermoplastic side of said primary laminates adjacent said third microfibrous web, said first, second and third webs being wettable, joining said third microfibrous web and said primary laminates by bonding to form a continuous five-ply web of towels with each towel bonded about its periphery and severing said towels from said five-ply web thereof.

28. The process claimed in claim 27 wherein said first web is hydrophobic and is treated with a wetting agent prior to being adhesively bonded to said second tissue web.

29. The process claimed in claim 27 wherein said first web is hydrophobic and is treated with a wetting agent subsequent to being adhesively bonded to said second tissue web.

30. The process claimed in claim 27 wherein said third web is hydrophobic and is treated with a wetting agent prior to assembly of said third web and said primary laminates.

31. The process claimed in claim 27 wherein said bonding step is a heat bonding step.

32. The process claimed in claim 27 including the step of cold embossing said primary laminates prior to their joinder to said third web.

` 33. The process claimed in claim 27 including the step of hot embossing said primary laminates prior to their joinder to said third web.

34. The process claimed in claim 27 wherein said tissue outer ply is a wet strength paper tissue having a basis weight of about 15 g/m2 and including the step of surface treating the tissue side of said primary laminates with a wet-strength resin.

35. The process claimed in claim 27 including the step of additionally joining said primary laminates and said third web with a plurality of spot bonds.

36. The process claimed in claim 27 wherein said first web has a basis weight of about 15 grams per square meter.

37. The process claimed in claim 27 wherein said third web has a basis weight of about 30 grams per square meter.

38. The process claimed in claim 35 including the steps of hot embossing said primary laminates and treating the tissue sides thereof with a wet-strength resin prior to the joinder of said primary laminates to said second web.

39. The process claimed in claim 35 wherein said spot bonds are heat bonds.

40. A process of making a disposable towel having a five-ply construction comprising the steps of making primary laminate webs by adhesively bonding a first medium density, soft, bendable, nonwoven web to a second abrasion resistant, low linting, soft, bendable, tissue web, providing a third low density, soft, bulky, bendable, highly absorbant, nonwoven web, said first and third webs-being wettable, locating one of said primary laminate webs to either side of said third web with the tissue side of said primary Iaminate webs outermost, bonding said third web and said primary Iaminate webs to form a continuous five-ply web of towels with each towel bonded about its periphery and severing said towels from said five-ply web thereof.

41. The process claimed in claim 40 wherein said first web is hydrophobic and is treated with a wetting agent prior to being adhesively bonded to said second tissue web.

42. The process claimed in claim 40 wherein said first web is hydrophobic and is treated with a wetting agent subsequent to being adhesively bonded to said second tissue web.

43. The process claimed in claim 40 wherein said third web is hydrophobic and is treated with a wetting agent prior to assembly of said third web and said primary laminates.

44. The process claimed in claim 40 wherein at least one of said first and third webs is thermoplastic and said bonding step is a heat bonding step.