AU660564B2 - Thermoplastic compositions and nonwoven webs prepared therefrom - Google Patents

Description

THERMOPLASTIC COMPOSITIONS AND NONWOVEN WEBS PREPARED THEREFROM Background of the Invention The present invention relates to a melt-extrudable thermoplastic composition which contains an additive system. The composition, when melt-extruded to form a nonwoven web, results in a web having significantly improved tensile strength characteristics or in a wettable web which does not become significantly less wettable over time.

Thermoplastic compositions are described in US Patent No 4 923 914 to Ronald S Nohr and J Gavin MacDonald, incorporated herein by reference. The patent describes a surfacesegregatable, melt-extrudable thermoplastic composition which comprises at least one thermoplastic polymer and at least one additive having at least two moieties, A and B, in which: the additive is compatible with the polymer at melt extrusion temperatures but is incompatible at temperatures below melt extrusion temperatures, but each of moiety A and moiety B, if present as separate compounds, would be incompatible with the polymer at melt extrusion temperatures and at temperatures below melt extrusion temperatures; moiety B has at least one functional group which imparts to the additive at least one desired characteristic; the molecular weight of the additive is in the range of from about 400 to about 20 15,000; and the weight ratio of the polymer to the additive is in the range of from about 1 to S about 1,000; with the proviso that the additive cannot be a compound having the general formula, R R R R I I I I R R Ri R in which each R independently is a monovalent organic group selected from the group consisting of alkyl groups; R 1 is a monovalent organic group containing at least one ethyleneoxy grou; vicinal epoxy group, or amino group; and a and b, which can be the same or different, each have a value of at least 1. In preferred embodiments, the additive is a siloxane-containing compound, and one of the desired characteristics is wettability by water 30 when the polymer is inherently hydrophobic.

The compositions described in US Patent No 4 923 914 are especially useful for the formation of nonwoven webs by such melt-extrusion processes as meltblowing, coforming, and spunbonding. Upon being melt-extruded, such compositions result in a fibre having a differential, increasing concentration of the additive from the centre to the surface thereof, such that the concentration of additive toward the surface of the fibre is greater than the average concentration of additive in the more central region of the fibre and imparts to the IN:\LIBAA100023:LMM surface of the fibre at least one desired characteristic which otherwise would not be present.

The additive is miscible with the polymer at melt extrusion temperatures, under which conditions the additive and the polymer form a metastable solution. As the temperature of the newly formed fibre drops below melt extrusion temperatures, the additive becomes significantly less compatible with the polymer. Concurrent with this marked change in compatibility, the polymer beings to solidify. Both factors contribute to the rapid migration or segregation of the additive toward the surface which takes place in a controllable manner.

When the additive was a siloxane-containing compound and the desired characteristic was water-wettability, the resulting nonwoven webs, depending upon the additive and/or additive level, could become less wettable over time. This loss of wettability, or aging, was accelerated when the polymer composition contained titanium dioxide. Although the teaching of US Patent No 4 923 914 represents a significant improvement over prior methods of imparting water-wettability to shaped articles, nonwoven webs, made from inherently hydrophobic polymers, the aging problem was a limitation on the usefulness of surfacesegregatable compositions, particularly for disposable absorbent products.

A subclass of the additives encompassed by US Patent No 4 923 914 subsequently was discovered which permitted the preparation of wettable nonwoven webs which remained wettable for at least about two years at ambient temperature.

Such a subclass is a surface-segregatable, melt-extrudable thermoplastic composition which comprises at least one thermoplastic polyolefin and at least one additive having the general formula R2 R4 Rs R7 I I I R- Si- 8 I I I I

R

3

CH

2

R

6 R9

I

(CH2)p-O-(C2H40)x(C3H60)yRlo

S

*5

S

S

0S *5 S 55

S

in which: (a) (b) (c) (d) (e) 30 (g) (h) (i) (j)

R

1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups;

R

10 is hydrogen or a mo calent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about x represents an integer of from 1 to about y represents an integer of from 0 to about the ratio of x to y is equal to or greater than 2; said additive has a molecular weight of from about 350 to about 1,400; and said additive is present in an amount of from about 0.5 to about 5 percent by weight, based on the amount of thermoplastic polyolefin.

Such application also provides a method for preparing a wettable nonwoven web which remains wettable after its formation for at least two years at ambient temperature, which method comprises: melting a mixture which comprises a thermoplastic polyolefin and an additive; forming fibres by extruding the resulting melt through a die at a shear rate of from about 50 to about 30,000 sec- 1 and a throughput of no more than about 5.4kg/cm/hour; drawing said fibres; and collecting said fibres on a moving foraminous surface as a web of entangled fibres; in which the additive meets all of the requirements just described relative to the composition.

It subsequently was discovered that the use of an additive system comprising certain polysiloxane polyether additives of US Patent No 4 923 914 and a modified fumed silica having a hydrophobic surface unexpectedly gave either of two results: the amount of additive required in application Serial No 07/566 589 can be reduced by up to roughly percent without adversely affecting the wettability of the resulting nonwoven web, or when the additive is a polysiloxane polyether or an alkyl-substituted polysiloxane having a molecular weight of at least about 3,000, the resulting nonwoven web is not wettable, it remains hydrophobic, but exhibits improved tensile strength characteristics as compared with a 20 nonwoven web prepared from a thermoplastic composition lacking the hydrophobic fumed silica.

Silica and other materials have been incorporated into thermoplastic polymers, including polypropylene. For example, the inclusion of an organic peroxide and a nucleating agent in polypropylene is described in Japanese Patent Publication No 60-217207. The nucleating agent can be an organic salt, an organic compound, or an inorganic material such as silica, alum, titanium dioxide, carbon black, and various clay minerals.

SReferences which describe the inclusion of polypropylene or other thermoplastic polymer of an organic material include US Patent Nos 3 207 735 to Wijga (benzoic acid, substituted benzoic acids, hexahydro analogs thereof, and related compounds), 3 207 737 to Wales (aluminium salts of benzoic acid and related compounds), 3 207 739 to Wales (Group I and II S metal salts of certain mono- and polycarboxylic acids), 3 299 029 to Binsbergen et al.

(aluminium salts of benzoic acid and related compounds), 4 611 024 to Wolfe (an acetal of an S alditol and a hydrotalcite), and 4 808 650 to Titus et al. (fluorinated dibenzylidene sorbitol additives); and Japanese Patent Publication No 51-22740 (benzylidene sorbitol).

Finally, studies relating to the heterogeneous nucleation of polymers have been reported.

Examples of such studies include Chatterjee and Price, "Heterogeneous Nucleation of Crystallization of High Polymers from the Melt. I. Substrate-Induced Morphologies", L.

Polym. Sci., 13, 2369 (1975); Collington. "The Nucleation of Crystalline Olefins", Polypropylene: The Way Ahead, a conference of the Plastics and Rubber Institute, Madrid, IN:\LIBAA)00023:LMM r I Spain, November 1989; and Garg and Stein, "Crystallization and Morphology of Nucleated Polymers", Antec '88, 1021.

Notwithstanding the foregoing, it should be noted that neither the siloxane copolymers (whether polysiloxane polyethers or alkyl-substituted polysiloxanes) nor a modified fumed silica, when used alone, gave any improvement in tensile strength characteristics. For reasons not yet fully understood, there appears to be a synergy which results from the use of the modified fumed silica with either a polysiloxane polyether or an alkyl-substituted polysiloxane as taught herein.

Without wishing to be bound by theory, it is believed that the alkyl-substituted polysiloxane serves three functions: it acts as a dispersing agent for the modified fumed silica, thereby reducing or preventing agglomeration of the silica into larger particles, especially after destructuring; it helps reduce the surface free energy of the modified fumed silica which results in silica surfaces which are more readily "wet" by molten polyolefin; and it acts as a processing aid for the entire system during the melt-extrusion process.

Summary of the Invention It therefore is an object of the present invention to provide a melt-extrudable thermoplastic composition which includes a thermoplastic polyolefin and an improved additive system which in turn includes a first component and a second component.

It is another object of the present invention to provide an improved additive system for 20 thermoplastic polyolefins, which improved additive system includes a first component and a second component.

It also is an object of the present invention to provide a method for preparing a nonwoven web having improved tensile strength characteristics as compared to nonwoven webs prepared from the thermoplastic polyolefin alone.

A further object of the present invention is to provide a method for preparing a wettable nonwoven web which is wettable immediately after its formation without any postformation treatment, (ii) remains wettable after its formation for at least two years at ambient temperature, and (iii) employs a reduced amount of a surface-segregatable first component compared with the amount of such surface-segregatable first component required in the 30 absence of a second component.

Yet another object of the present invention is to provide a melt-extruded fibre, a nonwoven web, an article of manufacture, a disposable absorbent article, and a disposable article.

These and other objects will be apparent to one having ordinary skill in the art from a consideration of the specification and claims which follow.

Accordingly, the present invention provides a melt-extrudable thermoplastic composition which includes a thermoplastic polyolefm and an additive system having a first component and a second component, in which: IN:UBAA100023:LMM said first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula, R2 R4 R5

R

7

R

1 -Si-O-(Si-O)mf(Si-O)-- i-Rs R3 Rio Re R,

R

3 RlO K6 i9 wherein: R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; R 1 o is a monovalent C 6

-C

30 alkyl group or Rll-O-(C 2

H

4 0)x(C 3

H

6 )RyRI 2

R

11 is a monovalent C 1

-C

6 alkyl group; R 12 is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 200; x represents an integer of from 1 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from about 350 to about 36 000; said second component is a hydrophobic fumed silica, in which the weight ratio of said first component to said second component is in the range of about 10 to about 300; said additive system is present in an amount of from about 0.01 to about 3% by weight based on the amount of thermoplastic polyolefin.

When the composition is to be used to prepare a nonwoven web having improved tensile strength characteristics, the sum of m and n is in the range of from about 4 to about 100; x represents an integer of from about 4 to about 25; said first component has a molecular weight of from about 3,000 to about 18,000; and the weight ratio of said first component to said second component is in the range of from about 20 to about 20 When the composition needs to be surface-segregatable in order to prepare a wettable nonwoven web having reduced amounts of first component, m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; said first component has a molecular weight of from about 350 to about 25 1,200; and said first component is present in an amount of from about 0.35 to about 3 percent by weight, based on the amount of thermoplastic polyolefin.

.The present invention also provides methods for preparing a nonwoven web having improved tensile strength characteristics and a wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, (ii) remains 30 wettable after its formation for at least two years at ambient temperature, and (iii) employs a reduced amount of a surface-segregatable first component compared with the amount of such surface-segregatable first component required in the absence of a second component.

In a second embodiment of this invention there is therefore provided a method for preparing a nonwoven web having improved tensile strength characteristics, which method comprises: melting a thermoplastic composition which includes a thermoplastic polyolefin and an additive system having a first component and a second component; forming fibres by IN:LBAA]00023:LMM srr extruding the resulting melt through a die; drawing the fibres, and, collecting the fibres on a moving foraminous surface as a web of entangled fibres in which: said first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula: R2 R4 R5 R7 Rl-Si-O--(Si-O)m(Si-0)f--Si-R 3 Rio R 6

R

9 wherein R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; R 1 i is a monovalent C 6

-C

3 0 alkyl group or Ri-O-(C 2 H40)x(C 3

H

6 0)yR1 2

R

1 1 is a monovalent C 1

-C

6 alkyl group; R 12 is hydrogen or a monovalent Ci-C 3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 100; x represents an integer of from 4 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from about 3000 to about 36 000; said second component is a hydrophobic fumed silica in which the weight ratio of the first component to the second component is in the range of from about 10 to about said additive system is present in an amount of from about 0.01 to about 3% by weight, based on the amount of thermoplastic polyolefin.

In a third embodiment of this invention there is provided a method for preparing a nonwoven web having improved tensile strength characteristics, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an 20 additive system comprising a first component and a second component; forming continuous S fibres by extruding the resulting melt through a die; drawing said continuous fibres; collecting said continuous fibres into a tow; cutting said tow into staple fibres; laying said staple fibres onto a moving foraminous surface as a web of entangled fibres; and pattern bonding the resulting web of entangled fibres by the application of heat and pressure in which: 25 said first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula: R2 R4 R5 R7 R-Si-0-(Si-O) f (Si-O)n--Si-R 8

R

3 Ro R R wherein R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; R 10 is a monovalent C 6

-C

30 alkyl group or Ri-O0-(C 2

H

4 0)x(C 3

H

6 0)yR 12

R

11 is a monovalent C 1

-C

6 alkyl group; R 12 is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 100; x represents an integer of from 4 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from about 3000 to about 36 000; IN:\LIBAAlO0023:LMM said second component is a hydrophobic fumed silica in which the weight ratio of the first component to the second component is in the range of from about 10 to about said additive system is present in an amount of from about 0.01 to about 3% by weight, based on the amount of thermoplastic polyolefin.

In a fourth embodiment of this invention there is provided a method for preparing a wettable nonwoven web which is wettable immediately after its formation without any postformation treatment, remains wettable after its formation for at least two years at ambient temperature, and employs a reduced amount of a surfacesegregatable first component, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system which comprises a surface-segregatable first component and a second component; forming fibres by extruding the resulting melt through a die at a shear rate of from about 50 to about 30 000 sec- 1 and a throughput of no more than about 5.4kg/cm/hour; drawing said fibres; and collecting said fibres on a moving foraminous surface as a web of entangled fibres; in which: said surface-segregatable first component is a polysiloxane polyether having the general formula: R2 R4 Rs R7

R

1 -Si-0-(Si-O)i (S i-O)-S i-R 8 R3 CH 2

R

6 Rg

.(CH

2 )p-O-(C 2

H

4 0)i-(C 3 wherein: R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; R 10 is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 4; n represents 20 an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about 5; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; the ratio of x to y is equal to or greater than 2; said surface-segregatable first component has a molecular weight of from about 350 to about 1200; and said surface-segregatable first component is present in an amount of from about 0.35 to about 3% by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said surfacesegregatable first component to said second component is in the range of from about 20 to about 300.

In a fifth embodiment of this invention there is provided a method for preparing a 30 wettable nonwoven web which is wettable immediately after its formation without any postformation treatment, remains wettable after its formation for at least two years at ambient temperature, and employs a reduced amount of a surfacesegregatable first component, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system comprising a surface-segregatable first component and a second component; forming continuous fibres by extruding the resulting melt through a die at IN:LIBAAI00023:LMM I 8 a shear rate of from about 50 to about 30 000sec- 1 and a throughput of no more than about 5.4kg/cm/hour; drawing said continuous fibres; collecting said continuous fibres into a tow; cutting said tow into staple fibres; laying said staple fibres onto a moving foraminous surface as a web of entangled fibres; and pattern bonding the resulting web of entangled fibres by the application of heat and pressure; herein: said surface-segregatable first component is a polysiloxane polyether having the general formula: R1--Si-O-(Si-O)f(Si-O)i-S i-Ra R3 CH 2

R

6 R9

(CH

2 )p-0-(C 2 H40)-(C 3

H

6 0)y-R 1 i in which: RI-R 9 are independently selected monovalent C 1

-C

3 alkyl groups; Rlo is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about 5; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; the ratio of x to y is equal to or greater than 2; said surface-segregatable first component has a molecular weight of from about 350 to about 1200; and said surface-segregatable first component is present in an amount of from about 0.35 to about 3% by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said surface-segregatable first component to said second component is in the range of from about 20 to about 300.

20 In a sixth embodiment of this invention there is provided a composition which comprises a first component and a second component, in which: said first component is an alkyl-substituted polysiloxane having the general formula: R2 R4 Rs R7 Ri-Si-O--(Si-O) (Si-O)n--Si-R8

R

3

FR

10 Re R9 S. 25 wherein: R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; Ro 1 is a monovalent C 6

-C

30 alkyl group; m represents an integer of from about 5 to about 50; n S represents an integer of from 0 to about 200; said first component has a number-average S molecular weight of from about 3000 to about 36 000; and said first component has a polydispersity of from about 1.1 to about 2.5; and said second component is a hydrophobic fumed silica, in which the weight ratio of the said first component to said second component is in the range of from about 10 to about IN:ULBAAI00023:LMM 9 In certain preferred embodiments, the polyolefin is polypropylene. In other preferred embodiments, the nonwoven web produced in accordance with a method of the present invention is pattern bonded by the application of heat and pressure.

In certain desired embodiments, R 1 -Rq are methyl groups. In other desired embodiments, RIo is a monovalent C 15

-C

22 alkyl group. In still other desired embodiments, m represents an integer of from about 15 to about 25. In yet other desired embodiments, the first component has a number-average molecular weight of from about 8,000 to about 15,000.

The melt-extrudable thermoplastic composition of various embodiments of the present invention is particularly suited for the preparation of nonwoven webs useful in the production of such disposable abscyrbent articles as diapers, incontinent products, sanitary napkins, tampons, wipes, and the like, and such disposable products as surgical gowns, shoe covers, workwear, and the like.

Brief Description of the Drawings FIGS. 1-16, inclusive, are bar graphs comparing the tensile strength characteristics of nonwoven webs prepared in accordance with the present invention with such characteristics of control webs.

FIGS. 17-19, inclusive, are bar graphs comparing the tenacity characteristics of fibres prepared in accordance with the present invention with such characteristics of control fibres.

FIG. 20 shows typical stress-strain curves for fibres prepared in accordance with the present invention and for control fibres.

FIGS. 21 and 22 are scanning electron photomicrographs of spunbonded nonwoven webs which have been pattern bonded by the application of heat and pressure. The web of FIG. 21 is a control web while the web of FIG. 22 is a web prepared in accordance with the present invention.

Detailed Description of the Invention As already stated, the compositions of the present invention can be used to prepare nonwoven webs having either improved tensile strength characteristics or long-term hydrophilicity or wettability. A number of variables or conditions are generally applicable, regardless of the characteristics of the nonwoven web produced. Such variables or conditions 30 are discussed first under the heading, "Common Variables or Conditions"; definitions are included under this first heading. For convenience and clarity of presentation, however, the remainder of the discussion has been separated into two parts, one which deals with tensilestrength-improving aspects and the other which deals with hydrophilicity. These two parts have been given the headings, "Nonwoven Webs Having Improved Tensile Strength 35 Characteristics" and "Hydrophilic or Wettable Nonwoven Webs", respectively. The use of such headings, however, should not be construed as in any way limiting either the spirit or scope of the present invention.

IN:\LIBAA100023:LMM -s Common Variables or Conditions As used herein, the term "fibres" includes substantially continuous fibres which are of a length such that they can be regarded as continuous in comparison with their diameters, such as may be produced by a meltblowing process. The term also includes continuous fibres, such as those produced by a spunbonding process or by a typical melt-spinning process. Thus, the term "continuous fibres" is intended to exclude substantially continuous fibres.

The term "tensile strength characteristics", as used herein, has reference primarily to peak energy, peak load, peak elongation, and peak strain values as determined by Federal Test Method 5100 (Standard No 191A). Other procedures, such as the trap tear test, can be used, however.

Such terms as "melt-extrudable", "melt-extruded", and the like are meant to refer or relate to any melt-extrusion process for forming a nonwoven web in which melt-extrusion to form fibres is followed by web formation, typically concurrently, on a foraminous support.

The terms include, among others, such well-known processes as meltblowing, coforming, spunbonding, and the like. The terms also refer or relate to processes in which web formation is a separate, independent step after fibre formation; nonwoven webs prepared by such processes include bonded carded webs and the like.

As used herein, the term "weight ratio" means the approximate relationship by weight of the amount of first component in the improved additive system to the amount of second component. More specifically, the weight ratio is the quotient of the amount of first component divided by the amount of second component. Thus, the weight ratio is expressed as a whole number which represents the approximate weight of first component per unit weight of second component. Consequently, the weight ratio has no units.

The term "destructured" and variations thereof means a reduction in second component 25 particle size. The term "additive system" refers generally to the combination of first and second components.

In general, the term "thermoplastic polyolefin" is used herein to mean any thermoplastic polyolefin which can be used for the preparation of nonwoven webs including by melt extrusion. Examples of thermoplastic polyolefins include polyethylene, polypropylene, 30 poly(l-butene), poly(2-butene), poly(1-pentene), poly(2-pentene), poly(3-methyl-l-pentene), poly(4-methyl-l-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene, polychloroprene, polyacrylonitrile, poly(vinyl acetate), poly(vinylidene chloride), polystyrene, and the like.

The preferred polyolefins are those which contain only hydrogen and carbon atoms and 35 which are prepared by the addition polymerization of one or more unsaturated monomers.

Examples of such polyolefins include, among others, polyethylene, polypropylene, poly(1butene), poly(2-butene), poly(1-pentene), poly(2-pentene), poly(3-methyl-l-pentene), poly(4methyl-l-pentene), 1,2-poly-l,3-butadiene, 1,4-poly-l,3-butadiene, polyisoprene, polystyrene, and the like. In addition, such term is meant to include blends of two or more polyolefins and IN:%IBAA100023:LMM I- 11 random and block copolymers prepared from two or more different unsaturated monomers.

Because of their commercial importance, the most preferred polyolefins are polyethylene and polypropylene.

In addition, the term "thermoplastic polyolefin" is meant to include blends of two or more polyolefins and random and block copolymers prepared from two or more different unsaturated monomers. Blends of two or more polyolefins in some cases can provide remarkable and unexpected improvements in tensile strength characteristics, an example of which is a blend of two propylene polymers having different melt flow rates. More particularly, such a blend consists of from about 60 to about 40 percent by weight of a polypropylene having a melt flow rate of from about 30 to about 45 and from about 40 to about 60 percelat by weight of a polypropylene having a melt flow rate of from about 2 to about 10. Such a blend typically will have a melt flow rate of from about 18 to about The composition and the additive system of the present invention must contain both a first component and a second component. The first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula R2 R4 R5 R7 Ri-Si-0-(Si-O)i (Si-O)f-Si-R8 I I I I

R

3 Rio Re R 9 wherein: R 1

-R

9 are independently selected monovalent CI-C 3 alkyl groups; RIo is a monovalent C 6

-C

3 0 alkyl group cy Rl1-O-(C 2 I40)x(C3H 6 0)yRI 2

R

11 is a monovalent C 1

-C

6 alkyl group; R 12 is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of 20 from 1 to about 100; n represents an integer of from 0 to about 230; x represents an integer of from 1 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from S about 350 to about 36 000; As noted, R1-R 9 are independently selected monovalent C 1

-C

3 alkyl groups. In particular, R 1

-R

9 are independently selected methyl or ethyl groups. More particularly, R 1

-R

9 are methyl groups. While Ro 1 may be a monovalent C 6

-C

30 alkyl group, Ro 1 particularly may be a monovalent C 1 5

-C

22 alkyl group. In another preferred embodiment R 12 is either hydrogen or a methyl group.

In general, m represents an integer of from about 1 to about 100 and n represents an integer of from 0 to about 200. In particular, m represents an integer of from about 15 to about 25 and n represents an integer of from about 40 to The number-average molecular weight of the first component can be in the range of from about 350 to about 36,000. In particular, the first component will have a number-average molecular weight of from about 8,000 to about 15,000. While the polydispersity of the first component in general will be in the range of from about 1.1 to about 2.5, in particular the polydispersity will be in the range of from about 1.1 to about IN:\LIBAA00023:LMM 12 The term "first component" generally is used throughout this specification and in the claims to refer to any polysiloxane polyether, or alkyl-substituted polysiloxane, as defined herein, regardless of the properties desired in the nonwoven web prepared from a composition containing the additive system. On the other hand, the term may be used in a specific context to refer to a particular type of first component, a first component selected to provide either a nonwoven web having improved tensile strength characteristics or a hydrophilic nonwoven web. For convenience, a first component or polysiloxane polyether employed in a composition to be used for the preparation of hydrophilic webs often is referred to throughout this specification as a "surface-segregatable" first component or polysiloxane polyether. A first component or polysiloxane polyether employed for the purpose of providing nonwoven webs having improved tensile strength characteristics often is referred to herein as a "tensile strength-improving" first component or polysiloxane polyether, or "TSI" first component or polysiloxane polyether.

There is, however, an important distinction between the two types of additive systems which needs to be understood. In an additive system designed to provide a hydrophilic nonwoven web, the first component does, in fact, migrate or segregate to the surfaces of the fibres. In so doing, the first additive apparently becomes disassociated from the second component. Nevertheless, for reasons not fully understood, the presence of the second component permits the use of lower levels of first component in order to impart hydrophilicity to the fibres. Consequently, it is technically correct in this instance to refer to the first component as a surface-segregatable first component.

When the additive system is designed to provide a nonwoven web having improved tensile strength characteristics, however, the first component does not migrate or segregate to the surfaces of the fibres. Moreover, the first component is not known to become 25 disassociated from the second component. In other words, the tensile strength improvement S results from the combination of the two components. In the case of an additive system intended to provide a hydrophilic nonwoven web, the required alteration of the surface characteristics of the fibres results solely from the first component. It is important to understand, therefore, that the term "TSI first component" neither means nor implies that the 30 first component alone causes the improvements in nonwoven web tensile strength characteristics. The term is used for convenience and simply is a shorter way of designating a first component used in a tensile-strength-improving additive system.

Turning again to the general formula for the first component as set forth above, the preferred values of such other variables as m, n, p, x, y, first component molecular weight, 35 and amount of first component depend primarily on whether the first component is a TSI polysiloxane polyether or a surface-segregatable polysiloxane polyether, as described later. In general, however, the amount of first component will be in the range of from about 0.1 to about 3 percent by weight, based on the amount of thermoplastic polyolefin.

IN:ULIBAAI00023:LMM 13 The first component in general can be either a liquid or a solid. Regardless of its type, a liquid first component is desired. The use of a liquid first corrn -ent simplifies the preparation of the claimed additive system and composition, ab ill be described later.

The term "first component" is used broadly herein to encompass the use of more than one first component in a given composition or improved additive system, a mixture of two or more first components or alkyl-substituted polysiloxanes. Moreover, it should be appreciated by those having ordinary skill in the art that the first component as defined herein typically is not available as a pure compound. Thus, the presence of impurities or related materials which may not come within the general formula given above for the first component does not remove any given material from the spirit and scope of the present invention. For example, the preparation of a first component useful in the present invention typically results in the presence of free polyether. The presence of such free polyether is not known to have deleterious effects, although it may be necessary to increase the amount of first component to compensate for the presence of free polyether. As a practical matter, it is preferred that the amount of free polyether present in any first component be no more than about 30 percent by weight. More preferably, the amount of free polyether present in a first component will be no more than about 20 percent by weight.

The second component of the composition of the present invention is a hydrophobic fumed silica. The nature of the hydrophobic silica surface is not known to be critical. As with the first component, more than one second component or hydrophobic fumed silica can be employed, if desired.

In general, fumed silicas typically have surface areas in the range of from about 80 to about 410m 2 Fumed silicas are readily prepared by known methods; see, for example, by way of illustration only, US Patent Nos 2 863 738 to Antwerp, 3 423 184 to Biegler et al., 3 642 453 to Chilton et al., 4 048 290 to Lee, and 4 292 290 to Tunison, III.

The surface of fumed silica has three chemical groups: isolated hydroxy groups, (2) hydrogen-bonded hydroxy groups, and siloxane groups. Thus, the surface generally is hydrophilic, although the siloxane groups are hydrophobic. The hydrophilic silica surface of a S fumed silica, however, can be rendered hydrophobic by reacting surface hydroxy groups with 30 a hydrophobic reagent. Suitable reagents include polydimethylsiloxane, dimethyldichlorosilane, hexamethyldisilazane, and the like. Indeed, these three reagents have been used commercially to produce hydrophobic fumed silicas which are available from the Cab-O-Sil Division of Cabot Corporation, Tuscola, Illinois, as CAB-O-SIL* TS-720, TS-610, and TS-530, respectively. However, the nature of the reagent employed is not known to be 35 critical. It is expected that any reagent could be used which renders the fumed silica surface hydrophobic. See, by way of illustration, US Patent No 4 849 022 to Kobayashi and Ohnishi.

Fumed silica is characterized by its extremely small particle size and large surface area.

Molten spheres or primary particles of silica are produced by the hydrolysis of silicon tetrachloride vapor in a flame of hydrogen and oxygen. Such primary particles of silica IN:\LIBAA100023:LMM typically have diameters in the range of from about 0.007 to about 0.027 micrometers. Upon their formation, however, such primary particles collide and fuse with one another to form branched, three-dimensional, chain-like aggregates. Some reversible mechanical agglomeration or entanglement also takes place as the aggregates cool below the fusion temperature of silica. Thus, commercially available fumed silicas have particle sizes of from about 1 to roughly 80 micrometers, with the majority of the particles being in the 40-60 micrometer range. While it was previously conjectured that mechanical size reduction occurred as a result of a combination of melt extrusion temperatures with shearing forces which take place in the extruder and upon extrusion through the die. Such size reduction was believed to result in a particle size distribution ranging from about 1 to about 20 micrometers or so. The majority of the particles were believed to have sizes in the upper portion of the range, roughly 10-20 micrometers.

In view of continued work with commercial modified fumed silicas, it now is believed from microscopy analysis that the majority of agglomerated particles are in the range of from about 70 to about 80 micrometers. In addition, the size reductions resulting from melt extrusion now are deemed to be less than originally believed. Consequently, a particularly desirable embodiment of the present invention is grounded in the discovery that destructuring the second component particles results in even greater improvements in tensile strength characteristics. For convenience, the term "improved additive system" refers to an additive system in which the second component has been destructured, as already noted, In general, the method employed for destructuring is not known to be critical. However, S because agglomeration is a reversible phenomenon, destructuring must take place under conditions which will not permit agglomeration to reoccur. The best means known at the present time for preventing agglomeration after destructuring is to carry out the destructuring process in the presence of first component. In addition to preventing the agglomeration of S destructured second component, the first component also acts as a dispersing aid for the second component and as a processing aid for the melt extrusion of the composition containing the improved additive system. For these reasons, the improved additive system has a significance of its own.

30 Destructuring of the second component typically is accomplished by subjecting the additive system to processing in a ball mill. Although processing conditions will vary, depending upon the design and operation of the ball mill employed, suitable conditions will be readily determined by those having ordinary skill in the art. In generaL, the particles of second component need to be reduced to be within the range of from about 0.001 to about 1 35 micrometer, The preferred destructured particle size range is from about 0.2 to about 0.8 micrometer, with dithe most preferred range being from about 0.4 to about 0.6 micrometer.

The weight ratio of first component to second component in the additive system may be in the range of from about 10 to about 300, may also be in the range of from about 10 to about and in particular may be in the range of from about 10 to about IN:\LIBAAI00023:LMM The additive system typically is added to the thermoplastic polyolefin in an amount which is in the range of from about 0.01 to about 3 percent by weight, based on the amount of thermoplastic polyolefin. In particular, the improved additive system will be present at a level of from about 0.1 to about 1 percent by weight, and more particularly at a level of from about 0.1 to about 0.5 percent by weight.

The additive system of the present invention can be prepared by any number of methods known to those having ordinary skill in the art. The additive system most often will be prepared by simply dispersing the second component in the first component.

The thermoplastic composition of the present invention can also be prepared by any number of methods known to those having ordinary skill in the art. For example, the polymer in chip or pellet form and the additive system can be mixed mechanically to coat the polymer particles with improved additive system. If desired, the additive system can be dispersed, or dissolved and dispersed in the case where the first component is soluble, in a suitable solvent to aid the coating process, although the use of a solvent is not preferred. The coated polymer then can be added to the feed hopper of the extruder from which the fibres will emerge.

However, care must be taken to ensure complete dispersion of the additive system throughout the bulk of the polymer during extrusion.

Alternatively, the coated polymer can be charged to a heated compounder, such as a heated twin-screw compounder, in order to disperse the improved additive system throughout the bulk of the polymer. The resulting thermoplastic composition typically is extruded as rods which are fed to a chipper. The resulting chips (or pellets) then serve as the feed stock for a melt-processing extruder. In a variation of this procedure, the level of additive system present in the polymer is higher than that required in the polymer to be extruded into fibres. Tle improved additive system-containing polymer chips (often referred to as concentrate pellets) then are admixed with or metered into the polymer feed stock.

In another method, the additive system can be metered into the throat of the hopper which contains the polymer in particulate form and which feeds the extruder. In yet another method, the additive system can be metered directly into the barrel of the extruder where it is blended with the molten polymer as the resulting mixture moves toward the die.

.oo IN:\LIBAA100OO23:LMM Nonwoven Webs Having Improved Tensile Strength Characteristics When the melt-extrudable thermoplastic composition of the present invention includes as part of the additive system a polysiloxane polyether first component having a molecular weight of from about 3,000 to about 18,000 and meets certain other criteria, a nonwoven web prepared from such composition typically is not wettable (hydrophilic), even though a polysiloxane polyether has been incorporated into the fibers.

Therefore, it appears that such first component has not substantially migrated or segregated toward the surfaces of the fibers and that tensile strength improvements, unlike a surface phenomenon such as wettability, are not dependent upon the presence of sEuch first component at or near the fiber surfaces.

TSI First Component In preferred embodiments representing the use of a TSI first component or polysiloxane polyether, the sum of m and n is in the range of from about 4 to about 100, and x .20 represents an integer of from 4 to about 25. In other preferred embodiments, the sum of m and n is from about 13 to about 23. In still other preferred embodiments, p is either 1 or 2, but most preferably is 2. In yet other preferred embodiments, x is from about 8 to about 16.

As already noted, the TSI first component will have a molecular weight of from about 3,000 to about 18,000.

Preferably, the TSI first component molecular weight will be in the range of from about 3,000 to 10,000, and most preferably from about 3,000 to about 6,000.

In general, the TSI first component will be present in an amount of from about 0.1 to about 3 percent by weight, based on the amount of thermoplastic polyolefin. As a practical matter, TSI first component levels of from about S 0.1 to about 1.D percent by weight are preferred, with levels of from about 0.1 to about 0.5 percent by weight being most preferred.

With a TSI first component, the weight ratio of TSI first component to second component preferably will be in the range of from about 20 to about 60. The weight ratio of TSI first component to second component most preferably will be in the range of from about 25 to about Methods for Preparing a Nonwoven Web Having Improved Tensile Strength Characteristics Turning now to the method of the present invention, a nonwoven web having improved tensile strength characteristics is prepared by the method which includes: melting a thermoplastic composition which includes a thermoplastic polyolefin and an additive system having a first component and a second component; forming fibres by extruding the resulting melt through a die; drawing the fibres, and, collecting the fibres on a moving foraminous surface as a web of entangled fibres in which: said first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula: R2 R4 R 5

R

7 RI-Si-O-(Si-O)nT( i-O)n-Si-R8 R3 Rio Re R9 wherein R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; R 1 o is a monovalent C 6

-C

30 alkyl group or R1l-O-(C 2

H

4 0)x(C3H60)yRI 2

R

11 is a monovalent C 1

-C

6 i alkyl group; R 12 is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 100; x represents an integer of from 4 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from about 3000 to about 36 000; said second component is a hydrophobic fumed silica in which the weight ratio of the first component to the second component is in the range of from about 10 to about said additive system is present in an amount of from about 0.01 to about 3% by S weight, based on the amount of thermoplastic polyolefin.

*e IN:\LIBAA]00023:LMM 18 In the first step of the method of the present invention, a thermoplastic composition which includes a thermoplastic polyolefin and an additive system having a first component and a second component as already defined is melted. This typically is done in an extruder which is an integral part of the apparatus used to form fibers. The temperature and residence time in the extruder are dependent primarily on the thermoplastic polyolefin employed.

Thus. such parameters can be determined readily by one having ordinary skill in the art without undue experimentation.

Fibers then are formed by extruding the molten mixture through a die.

Although the nature of the die is not known to be critical, it most often will have a plurality of orifices arranged in one or more rows extending the full machine width. Such orifices may be circular or noncircular in cross-section.

The fibers then are drawn, typically by entraining them in a fluid stream having a sufficiently high velocity. When continuous fibers are produced, the fibers first are cooled in a quenching fluid which usually is low pressure air. The fluid stream which draws the fibers, usually air, can be a stream of high velocity air separate from the quenching fluid, or it can be a portion of the quenching fluid which is accelerated by passage into a narrow nozzle. In the production of substantially continuous fibers, on the other hand, the fluid stream usually is a heated, high velocity stream of air which draws the fibers while they are in an at least partially molten or softened state.

The drawn fibers then are collected on a moving foraminous surface as a web of entangled fibers. The foraminous surface can be, by way of example only, a revolving drum or a continuous belt or wire screen; the latter is most commonly used on commercial-scale equipment.

In general, the steps of melting, forming, drawing, and collecting are -arried out as described in such processes as meltblowing, spunbonding, and the .oo.oi like. By way of illustration only, such processes are exemplified by the following references which are incorporated herein by reference: 19 meltblov ing references include, by way of example, U.S. Patent Nos.

3,016,599 to R. W. Perry, Jr., 3,704,198 to J. S. Prentice, 3,755,527 to J. P.

Keller et al., 3,849,241 to R. R. Butin et al., 3,978,185 to R. R. Butin et al., and 4,663,220 to T. J. Wisneski et al. See, also, V. A. Wente, "Superfine Thermoplastic F.bers", Industrial and Engineering Chemistry, Vol. 48, No. 8, pp. 1342-1346 (1956); V. A. Wente et al., "Manufacture of Superfine Organic Fibers", Navy Research Laboratory, Washington, 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, No.4, pp. 74- 77 (1973); and spunbonding references include, among others, U.S. Patent Nos.

3,341,394 to Kinney, 3,655,862 to Dorschner et al., 3,692,618 to Dorschner et al., 3,705,068 to Dobo et al., 3,802,817 to Matsuki et al., 3,853,651 to Porte, 4,064,605 to Akiyama et al., 4,091,140 to Harmon, 4,100,319 to Schwartz, 4,340,563 to Appel and Morman, 4,405,297 to Appel and Morman, 4,434,204 to Hartman et al., 4,627,811 to Greiser and Wagner, and 4,644,045 to Fowells.

If continuous ibers are formed, such as by a spunbonding process, the resulting web must be pattern bonded by the application of heat and pressure in order for the nonwoven web to exhibit improved tensile strength characteristics.

Preferably, such application of heat and pressure will be in the ranges of from about 80 0 C to about 180 0 C and from about 150 to about 1,000 pounds per linear inch (59-178 kg/cm), respectively. More preferably, a pattern having from about 10 to about 250 bonds/inch 2 (1-40 bonds/cm 2 covering from about 5 to about percent of the surface area of the nonwoven web will be employed.

Such pattern bonding is accomplished in accordance with known procedures. See, for example, U. S. Design Patent No. 239,566 to Vogt, U.S.

Design Patent No. 264,512 to Rogers, U.S. Patent No. 3,855,046 to Hansen et al., and US Patent No 4 493 868, supra, for illustrations of bonding patterns and a discussion of bonding procedures.

A nonwoven web having improved tensile strength characteristics also is prepared by the method which comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefm and an additive system comprising a first component and a second component; forming continuous fibres by extruding the resulting melt through a die; drawing said continuous fibres; collecting said continuous fibres into a tow; cutting said tow into staple fibres; laying said staple fibres onto a moving foraminous surface as a web of entangled fibres; and pattern bonding the resulting web of entangled fibres by the application of heat and pressure; in which the first component and second component are as already defined.

Each of the foregoing steps is carried out as already described or by any of several means which are well known to those having ordinary skill in the art. If desired, individual continuous fibres can be false twisted before collecting them as a tow. Moreover, the tow can be crimped before cutting into staple-length fibres. Although the staple fibres can be laid onto the moving foraminous support by any known means, the fibres preferably will be either airlaid or wet-laid. Finally, the pattern bonding of the resulting nonwoven web can be by known means as already described hereinabove.

Hydrophilic or Wettable Nonwoven Webs Wettable webs result from the inclusion in the composition to be melt-extruded of an additive system which comprises a first component which is a defined polysiloxane polyether having a molecular weight of from about 350 to about 1,200 and a second component which is a hydrophobic fumed silica. Moreover, such webs do not become significantly less wettable over time. Such webs, however, do not demonstrate significant tensile strength 2 improvements. Because the webs are wettable, though, it is clear that a substantial proportion 25 of the first component or polysiloxane polyether has migrated to or near the surfaces of the fibres of which the web is composed.

The use herein of the term "surface-segregatable" is consistent with its use in US Patent No 4 923 914. Upon forming fibres by melt-extruding composition of the present invention which contains an additive system comprising a surface-segregatable first component and a second component as defined herein, there is in such a fibre a differential, increasing concentration of the first component from the centre to the surface thereof. The concentration of first component at or near the surface of the fibre is sufficient to render the normally hydrophobic polyolefmin wettable by water; that is, the fibre has been rendered hydrophilic.

Unless stated otherwise, the term "hydrophilic" will be used herein to mean water-wettable.

35 Thus, there is a controlled migration or segregation of first component toward the surface of the fibre which results in a controllable, differential concentration of first component in the fibre. Because the concentration of first component in the centre portion of the fibre typically will vary nonlinearly from the concentration of such component at or near the surface, this concentration difference is referred to herein as a differential concentration.

IN:LIBAA100023:LMM Surface-Segregatable First Component In preferred embodiments representing the use of a surface-segregatable first component or polysiloxane polyether, m represents an integer of from 1 to about 4, n represents an integer of from 0 to about 3, the sum of m and n is in the range of from about 1 to about 4, x represents an integer of from 1 to about 10, and y represents an integer of from 0 to about In other preferred embodiments, m is either 1 or 2. In still other preferred embodiments, p is either 1 or 2, but most preferably is 2. In yet other preferred embodiments, y is 0 and x is 7 or 8.

Preferably, n will be 0, in which case the surface-segregatable first component or polysiloxane polyether will have the general formula R2 R R Rj-Si-O-(-Si-O-)m-Si-R8 I I I R3 CH 2

R

9

(CH

2 )p-O-(C 2 H(O)x-(C3H60)y-Ro1 in which each of R 1

-R

4

R

7

-R

9 m, p, x and y are as already defined.

While the surface-segregatable first component molecular weight can vary from about 350 to about 1,200, it preferably will not exceed about 1,000. Most preferably, the molecular weight will be in the range of from about 350 to about 700.

e *ee S e e ***ee et *ao IN:\UBAA00023:LMM In general, the surface-segregatable first component will be present in an amount of from about 0.35 to about 3 percent by weight, based on the amount of thermoplastic polyolefin.

As explained earlier, however, the presence of the second component in the additive system permits the reduction of the amount of surface-segregatable first component employed without sacrificing wettability. Since amounts of surfacesegregatable first component greater than about 1 percent by weight yield wettable webs in the absence of the second component, levels of surface-segregatable first component of no more than about 1 percent are preferred. Thus, the preferred range for the surface-segregatable first component is from about 0.35 to about 1 percent by weight, based on the amount of polyolefin. Surface-segregatable first component levels of from about 0.35 to about 0.7 percent by weight are more preferred, with levels of from about 0.35 to about percent by weight being most preferred.

With a surface-segregatable first component or polysiloxane polyether, the weight ratio of surface-segregatable first :20 component to second component preferably will be in the range of from about 30 to about 100.

While the mechanism by which the second component interacts with a surface-segregatable first component or polysiloxane polyether is not known, there clearly is a synergistic effect which results from the inclusion in the composition of the present invention of both a surfacesegregatable first component and a second component as defined herein. The ability of the second component to permit up to an approximately fifty percent reduction in the amount of 30 surface-segregatable first component required to render the resulting nonwoven web wettable is even more remarkable and unexpected when one considers both the nature of the second component and the very small amounts of second component employed.

It is important to note that the wettable nonwoven webs prepared in accordance with the present invention are immediately wettable, notwithstanding the low levels of surface-segregatable first component which are employed. Moreover, such webs are wettable without the need for a post-formation treatment of any kind, such as gently heating the web as described in US Patent No 4 857 251 to Nohr and MacDonald or a blooming procedure such as that described in US Patent Nos 3 973 068 and 4 070 218 to Weber. Finally, such webs remain wettable for at least two years at ambient temperature.

Methods for Preparing a Wettable Nonwoven Web A wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, remains wettable after its formation for at least two years at ambient temperature, and employs a reduced amount of surface-segregatable first component, is prepared by the method which comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system which comprises a surfacesegregatable first component and a second component; forming fibres by extruding the resulting melt through a die at a shear rate of from about 50 to about 30 000 sec 1 and a throughput of no more than about 5.4kg/cm/hour; drawing said fibres; and collecting said fibres on a moving foraminous surface as a web of entangled fibres; in which: said surface-segregatable first component is a polysiloxane polyether having the general formula: R2 R4 R 5

R

7 R-Si-O-(Si-O)f (Si-O)n-Si-R 8 R3 CH 2

R

6

R

9

(CH

2

(C

2

H

4 (C3H 6

R

10 20 wherein: R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; R 1 0 is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about 5; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; the ratio of x to y is equal to or greater than 2; said 25 surface-segregatable first component has a molecular weight of from about 350 to about 1200 and preferably from about 350 to about 700; and said surface-segregatable first component is present in an amount of from about 0.35 to about 3% by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said surface-segregatable first component to said second component is in 30 the range of from about 20 to about 300.

A wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, remains wettable after its formation for at least two years at ambient S temperature, and employs a reduced amount of surface-segregatable first component, also is prepared by the method which comprises: melting a thermoplastic composition which ajI 4 comprises a thermoplastic polyolefin and an additive system comprising a surface-segregatable

Q\

1°CS .N:\LIBAA]00023:EAR C. r 6.

first component and a second component; forming continuous fibres by extruding the resulting melt through a die at a shear rate of from about 50 to about 30 Osec- 1 and a throughput of no more than about 5.4kg/cm/hour; drawing said continuous fibres; collecting said continuous fibres into a tow; cutting said tow into staple fibres; laying said staple fibres onto a moving foraminous surface as a web of entangled fibres; and pattern bonding the resulting web of entangled fibres by the application of heat and pressure; herein: said surface-segregatable first component is a polysiloxane polyether having the general formula- R2 R4 R 5 R7 R-Si-O-(Si-O)-7 (Si-O)--Si-R8 II I I R3 CH 2

R

6 R9

(CH

2

(C

2

H

4 0)x-(C 3

H

6 0)y-R10 in which: R 1

-R

9 are independently selected monovalent C 1

-C

3 alkyl groups; Ro is hydrogen or a monovalent C 1

-C

3 alkyl group; m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about 5; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; the ratio of x to y is equal to or greater than 2; said surface-segregatable first component has a molecular weight of from about 350 to about 1200 and preferably from about 350 to about 700; and said surface-segregatable first component is present in an amount of from about 0.35 to about 3% by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed sili,, i. which the weight ratio of said surface-segregatable first component to said second component is in the range of from about 20 to about 300.

Each of the steps in the foregoing two methods is carried out as already described or by any of several means which are well known to those having ordinary skill in the art. In general, the shear rate will be in the range of from about 50 to about 30,000 sec- 1 25 Preferably, the shear rate will be in the range of from about 150 to about 5,000 sec- 1 and most preferably from about 300 to about 2,000 sec- 1 Throughput typically will be in the range of from about 0.01 to about 5.4kg/cm/hour.

0 Preferably, throughput will be in the range from about 0.1 to about 4.0kg/cm/hour. The throughput most preferably will be in the range of from about 0.5 to about 30 The present invention is further described by the examples which follow. Such examples, however, are not to be construed as limiting in any way either the spirit or scope of the present invention. In the examples, all parts are by weight unless stated otherwise. For convenience, the examples are separated into three groups, with the first group employing TSI first components or polysiloxane polyethers, the second group employing surface-segregatable first components or polysiloxane polyethers and the third group employing alkyl-substituted )fR -/Xpolysiloxanes.

Si L- I[NLIBAA100023:EAR 7 I GROUP I EXAMPLES TSI FIRST COMPONENTS Example 1 Preparation of Spunbonded webs Spunbonded nonwoven webs were prepared on a pilot-scale apparatus essentially as described in U.S. Patent No.

4,340,563, which is incorporated herein by reference.

The thermoplastic polyolefin employed was Escorene 3445 polypropylene (Exxon Chemical Americas, Houston, Texas 77079).

According to the manufacturer, the polymer has a density of 0.90 g/rc and a melt fl'w rate of 35 g/10 minutes.

The TSI first component was a polysiloxane polyether having the formula,

CH

3

CH

3

CH

3

CH

3 I I I I

CH

3 13 -Si-CH 3 I I

CH

3

CH

2

CH

3

CH

3

I

S(CH

2 )2-0-(C 2

H

4 0) 12

CH

3 25 The second component was CAB-O-SIL® TS-720, a hydrophobic fumed silica supplied by Cab-O-Sil Division, Cabot Corporation, Tuscola, Illinois.

The second component was dispersed in the TSI first component at a weight ratio of 1:30 (first component second 30 component) by means of a Henschel Fluidizing Mixer (250-liter capacity, Thyssen Henschel, 3500 Kassel 2 Postfach 102969, Germany). The mixer was run at 1,500 rpm for less than seconds. Some care was required in order to minimize the entrapment of air. The resulting additive system preferably S 35 is allowed to stand for a minimum of about 12 hours before use to permit the additive system viscosity to stabilize.

The additive system was metered (pumped) into a twinscrew extruder downstream from the extruder feed hopper at a rate equivalent to 3 percent by weight, based on the amount of polypropylene. The pumping rate of the additive system, the weight of the additive system container, and the polymer feed rate were monitored in order to control the level of additive system in the polymer. The resulting molten blend of polymer, Lirst component, and second component was extruded as a plurality of rods 2-3 mm in diameter. The rods were passed through a water bath, air dried, and pelletized. The additive system level in the resulting pellets was confirmed by elemental analysis for silicon. The pellets, referred to hereinafter as 3 percent concentrate pellets, were stored in plastic-lined boxes.

Five different spunbonded webs having basis weights of rbout 47 grams per square meter (gsm) were prepared: a control web prepared from virgin polypropylene; a web prepared from a mixture of 1.36 kg of 3 percent concentrate pellets and 18.6 kg of virgin polypropylene; a web prepared from a mixture of 1.81 kg of 3 percent concentrate pellets and 18.1 kg of virgin polypropylene; a control web prepared from polypropylene containing 1 percent by weight, based on the amount of polymer, of a phthalocyanine dye (Pigment SCC4402, Standridge Color Corp., Social Circle, Georgia); and a web prepared from a mixture of 1.36 kg of 3 percent concentrate pellets and 18.6 kg of polypropylene containing 1 percent by weight, based on the amount of polymer, of a phthalocyanine dye (Pigment SCC4402).

30 The compositions from which the webs were prepared .re summarized in Table 1-1. In the table, the amount of poliymer includes polymer present in the concentrate pellets without correcting for the amounts of first component and second component present. All other values are calculated values since each web was prepared from concentrate pellets rather 27 than by the direct addition of additive system to virgin polymer.

Table 1-1 Summary of the Compositions of the Spunbonded Webs of Example 1 Grams Kg. Additive Grams Grams Web Polymer System 1st Comp. 1st Comp. 2d Comp.

1 20.0 None None None None 2 20.0 40.8 39.5 0.20 1.3 3 20.0 54.4 52.6 0.26 1.8 4 20.0 a None None None None 5 20.0 a 40.8 39.5 0.20 1.3 aThe polypropylene contained 1 percent by weight, based on the amount of polymer, of a phthalocyanine dye (Pigment SCC4402, Standridge Color Corp., Social Circle, Georgia).

20 The more significant process variables for the spunbonding process generally were as follows: extruder temperature, 210 0 -222°C; melt inlet temperature, 233'-236°C; throughput, 29 kg per hour (0.8 grams per hole per minute); spin head temperature, 228 0 -233°C; Spump block temperature, 231°-23G°C; oo* pack temperature, 246 0

C;

pack pressure, 350 psig; and 30 melt temperature, 223°-224C°.

Each web was thermally pattern bonded at about 138°-140 0

C

and about 12 psi. The pattern employed had 123 bonds/inch 2 (19 bonds/cm 2 covering about 16.9 percent of the web surface area. It appeared, however, that bonding conditions were not consistent for all five webs.

28 Mean peak energy and peak load values for each web were determined in accordance with Federal Test Method 5100 (Standard No. 191A). The apparatus employed was an Instron Model 1122 Universal Testing Instrument with an Instron Micron II Desk Top Console-Integrator (Instron Corporation, Canton, Massachusetts). The jaw span gap was 3 inches (7.6 cm) and web sample dimensions were 3" x 6" (7.62 cm x 15.2 cm). In general, at least ten samples from each web were run. Each web was tested in both the machine direction (MD) and the cross direction The data are summarized in Table 1-2.

In order to aid in the visualization of the extent of improvement or increase in mean peak energy and peak load values which resulted from the presence of the first component and second component, Table 1-2 includes "Percent Increase" columns after the "Peak Energy" and "Peak Load" columns. In each case, the percent increase (PI) was calculated by subtracting the control value from the value obtained from the inclusion of the additive system in the polymer from which the web was prepared, dividing the difference by the control OS 20 value, and multiplying the quotient by 100; PI 100 x (improved value control value)/control value.

Table 1-2 Tensile Strength Characteristics for the Webs of Example 1 Peak Peak Energy Percent Load Percent Web Direction (m-kcF) Increase (kqF) Increase 30 1 MD 0.109 11.0 S' CD 0.070 7.7 2 MD 0.391 259 17.4 58 CD 0.235 236 10.4 3 MD 0.208. 91 13.3 21 CD 0.239 241 10.5 36 4 MD 0.092 9.6 CD 0,082 6.6 MD 0.324 252 15.8 CD 0.366 346 12.5 89 In spite of the difficulties in maintaining the same bonding conditions for all of the webs, it is clear from Table 1-2 that the use of the additive system in accordance with the present invention results in significant increases in the tensile strength characteristics of the nonwoven webs. In general, the improvements are more pronounced in the machine direction, although the improvements in the cross direction are substantial.

To aid in the visualization of the improvements demonstrated by the data in Table 1-2, the peak energy data and peak load data have been plotted as bar graphs in FIGS. 1 and 2, respectively. Both the machine direction value and the cross direction value for each web are included in each figure. It is clear from FIGS. 1 and 2 that peak energy is more sensitive to the inclusion in the polymer of the additive system. That is, for any given web of the present invention, peak energy values are increased significantly more than are peak load values. Finally, the presence of the dye in web not only did not have a deleterious effect on the improvement 25 of tensile strength characteristics, but also may have S contributed to a significant improvement in both peak energy and peak load values in the cross direction.

Example 2 Preparation of Spunbonded webs The procedure of Example 1 was repeated, except that the concentrate pellets were prepared with Type PF-301 polypropylene (Himont Incorporated, Wilmington, Delaware). According to the manufacturer, the polymer has a melt flow rate of minutes. The number-average molecular weight is 50,000 and the weight-average molecular weight is 150,000. Thus, the polydispersity of the polymer is 3.0. In addition, the concentrate pellets contained 3.3 percent by weight of the additive system, rather than 3 percent by weight. In each case, the weight ratio of TSI first component to second component was 31.

Again, five different spunbonded webs having basis weights of about 47 grams per square meter (gsm) were prepared: a control web prepared from virgin Escorene 3445 polypropylene; a control web prepared from a mixture of 1.36 kg of Type PF-301 polypropylene and 18.6 kg of Escorene 3445 polypropylene; a web prepared from a mixture of 1.36 kg of 3.3 percent concentrate pellets and 18.6 kg of Escorene 3445 polypropylene; a web prepared from a mixture of 1.36 kg of 3.3 percent concentrate pellets and 18.6 kg of Escorene 3445 20 polypropylene containing 3 percent by weight, based on the amount of polymer, of titanium dioxide; and a web prepared from a mixture of 1.36 kg of 3 percent concentrate pellets and 18.6 kg of Escorene 3445 polypropylene containing 1 percent by weight, based on the amount of polymer, of a phthalocyanine dye (Pigment SC 4402).

The compositions from which the webs were prepared are summarized in Table 2-1.

Table 2-1 30 Summary of the Compositions of the Spunbonded Webs of Example 2 Grams Kg. Additive Grams Grams Web Polymer System 1' st Comp. 1st Comp. 2d Comp.

1 20.0 a None None None None 2 20.0 b None None None None 3 20.0 b 44.9 43.5 0.22 1.4 4 20.0 c 44.9 43.5 0.22 1.4 20.0 d 44.9 43.5 0.22 1.4 aThe polypropylene consisted entirely of Escorene 3445.

bThe polypropylene consisted of 1.36 kg of Type PF-301 polypropylene and 18,6 kg of Escorene 3445.

CThe polypropylene consisted of 1.36 kg of Type PF-301 polypropylene and 18.6 kg of Escorene 3445 containing 3 percent by weight of titanium dioxide.

dThe polypropylene consisted of 1.36 kg of Type PF-301 polypropylene and 18.6 kg of Escorene 3445 containinc 1 percent by weight of a phthalocyanine dye (Pigment SC 4402).

Mean peak energy and peak load values were determined as before. The data are summarized in Table 2-2. In the table, all percent increase values were calculated in relation to web 2 since web 1 did not contain any Type PF-301 20 polypropylene.

Table 2-2 Tensile Strength Characteristics for the Webs of Example 2 Peak Peak Energy Percent Load Percent Web Direction (m-kgF) Increase (kqF) Increase 1 MD 0.111 11.2 30 CD 0.071 7.9 2 MD 0.113 11.5 CD 0.084 9.2 3 MD 0.364 222 17.3 CD 0.340 305 12.4 4 MD 0.291' 158 15 7 71 CD 0.300 257 13.1 42 MD 0.166 47 12.9 12 CD 0.187 123 10.4 13 Results similar to those of Example 1 were obtained. As with Example 1, the peak energy data and peak load data of Table 2-2 have been plotted as bar graphs in FIGS. 3 and 4, respectively. It is not understood, however, why the improvements in tensile strength characteristics observed for web 5 were reduced in comparison with the improvements for web 3.

Example 3 Preparation of Spunbonded Webs The procedure of Example 1 was repeated in order to examine the effect of increasing concentrations of additive system. This time four different spunbonded webs having basis weights of about 47 grams per square meter (gsm) were ee° prepared: a web prepared from a mixture of 1.13 kg of 3 percent concentrate pellets and 18.8 kg of virgin polypropylene; a web prepared from a mixture of 1.36 kg of 3 percent concentrate pellets and 18.6 kg of virgin polypropylene; a web prepared from a mixture of 1.59 kg of 3 percent concentrate pellets and 18.4 kg of virgin polypropylene; and a web prepared from a mixture of 1.81 kg of 3 percent concentrate pellets and 18.1 kg of virgin polypropylene; ooeo• The compositions from which the webs were prepared are summarized in Table 3-1.

Table 3-1 Summary of the Compositions of the Spunbonded Webs of Example 3 Web 1 2 3 4 Kg.

Polymer 20.0 20.0 20.0 20.0 Grams Additive System 34.0 40.8 47.6 54.4 Grams 1st Comp.

32.9 39.5 46.1 52.6 Wt.-% 1st Ccmp.

0.16 0.20 0.23 0.26 Grams 2d Comp.

1.1 1..

1.8 Mean peak energy and peak load values were determined as before. The data are summarized in Table 3-2 which includes the control of Example 1 (web 1) as web C since it was found that control values were essentially constant.

I**

20 20 *ee eo oo .1 1 oeoo Table 3-2 Tensile Strength Characteristics for the Webs of Example 3 Web 25- C 2 *30 3

*A

e*eoo3o 3 Peak Energy Direction (m-kqF) MD 0.109 CD 0.070 MD 0.386 CD 0.276 MD 0.455 CD 0.524 MD 0.442 CD 0.566 MD 0.331 CD 0.483.

Percent Increase 254 294 317 649 306 709 204 590 Peak Load (kqF) 11.0 7.7 14.5 9.9 15.5 12.9 15.2 12.7 14.3 11.8 Percent Increase 32 29 41 68 38 53 Results similar to those of Example 1 were obtained. It may be noted that the webs of Example 3 resulted in very high percent increases in peak energy values. As with Example i, the peak energy data and peak load data of Table 3-2 have been plotted as bar graphs in FIGS. 5 and 6, respectively. From FIG. 5, it appears that machine direction peak energy is at a maximum in -,eb 2, whereas cross direction peak energy is at a maximum in web 3. Thus, for the combination of first component, second component, and polyolefin employed, the most preferred range for the first component is from about 0.20 to about 0.23 percent by weight, based on the amount of polyolefin. Peak load, on the other hand, appears to maximize for both the machine direction and the cross direction in web 2 which has a first component concentration of 0.20 weight percent.

Example 4 Preparation of Meltblown Webs o Meltblown webs were prepared on a commercial meltblowing line essentially as described in U.S. Patent Nos. 3,849,241 to to Buntin et al. and 4,663,220 to Wisneski et al. The process employed the polymer, first component, and second component described in Example 1. In this case, however, the concentrate pellets contained 13 percent by weight of the additive system of Example 1. The feed rates for the concentrate pellets were selected to introduce the concentrate pellets into the extruder at levels of 2 and 4 percent by weight, respectively, based on the amount of polypropylene being meltblown. The levels were calculated to yield first component level- of about 0.24 and 0.48 percent by weight, respectively, based on the amount of polypropylene. A control S web containing neither first component nor second component also was prepared. Each web had a basis weight of about 31 gsm. Because the mill at which the webs were prepared was not set up to run peak energy and peak load measurements, trap tear tests were conducted instead. Such tests were carried out according to ASTM Test Method D-1117-14. The results are summarized in Table 4-1.

Table 4-1 Summary of Trap Tear Results for the Meltblown Webs of Example 4 Trap Percent Tear Percent Web Direction 1st Comp. (kg) Increase 1 MD 0 0.49 CD 0 0.44 2 MD 0.24 0.51 4 CD 0.24 0.46 3 MD 0.48 0.78 59 CD 0.48 0.82 86 While there is not a known, direct correlation between 20 trap tear results and either peak energy or peak load values, it is known that when trap tear increases, peak energy and peak load values also increase. Thus, even in the absence of peak energy and peak load measurements, it is clear that the inclusion of the first component and second component in the 25 meltblown webs resulted in improved tensile strength characteristics. Consistent with the practice in the preceding examples, the data of Table 4-1 were plotted as a bar graph in FIG. 7. Although the percent increase in trap tear at a first component level of 0.24 percent by weight was not substantial, a significant increase at a first component level of 0.48 percent by weight was observed, especially in the cross direction.

cross direction.

36 Example Preparation of Spunbonded Webs Spunbonded webs were prepared on a commercial spunbonding line essentially as described in U.S. Patent Nos. 3,341,394 to Kinney and 3,655,862 to Dorschner et al. The process employed the additive system described in Example 1.

In this case, the polymer was the Himont Type PF-301 described in Example 2. The polymer contained 0.5 weight percent, based on the amount of polymer, of Pigment SCC4402, Standridge Color Corp., Social circle, Georgia. The polymer also contained 0.7 percent by weight, based on the amount of polymer, of. an isooctylphenylpolyethoxyethanol surfactant (TRITON® X-102, Rohm and Haas Company, Philadelphia, Pennsylvania).

Concentrate pellets containing 3 percent by weight of additive system were prepared as described in Example 1. The feed rates for the concentrate pellets were selected .to Sintroduce the concentrate pellets into the extruder at levels 20 of 7 and 9 percent by weight, respectively, based on the amount of polypropylene being meltblown. The levels were calculated to yield first component levels of about 0.21 and about 0.27 percent by weight, respectively, based on the amount of polypropylene. A control web containing neither S 25 first component nor second component also was prepared (web Each web had a basis weight of about 19 gsm. Problems with web formation were encountered at the 9 percent feed rate, although fiber formation appeared to be satisfactory.

SConsequently, a web at the 9 percent feed rate was not obtained.

Because the mill at which the webs were prepared was not set up to run peak energy measurements, peak load and trap tear measurements were conducted instead as already described.

The results are summarized in Tables 5-1 and 5-2.

Table 5-1 Summary of Peak Load Results for the Spunbonded Webs of Example Web 1 Direction

MD

CD

MD

CD

Percent 1st Comp.

0 0 0.21 0.21 Peak Load (kqF) 4.22 5.21 4.67 5.91 Percent Increase 11 13 Table 5-2 Summary of Trap Tear Results for the Spunbonded Webs of Example a. a 0**a Web 1 Direction

MD

CD

MD

CD

Percent 1st Comp.

0 0 0.21 0.21 Trap Tear (kq) 1.89 2.38 2.08 3.04 Percent Increase 28 a.

25 The data of Tables 5-1 and 5-2 were plotted as bar graphs in FIGS. 8 and 9, respectively.

Since most applications of nonwoven fabrics requiring improved tensile strength characteristics also typically have been thermally pattern bonded as described herein, the behavior under stress of many of the control webs and webs of the present invention was examined. Scanning electron photomicrographs of the webs also were studied. The photomicrographs (FIGS. 10 and 11) were obtained at Surface Science Laboratories, Inc., Mountain View, California with a Camscan Series 4 Scanning Electron Microscope (Camscan, Cambridge, 38 England). The parameters used were as follows: a 30 degree tilt, a magnification of 20X, and a 10 keY beam voltage.

FIG. 10 is a photomicrograph of a spunbonded control web and FIG. 11 is that of a spunbonded web of the present invention. Each web was thermally pattern bonded as described herein under essentially identical conditions. In web 100 of FIG. 10, the web is composed of a plurality of randomly laid fibers 101 which have been thermally bonded at a plurality of sites 102. The extent of melting at bonding sites 102 generally is incomplete; note that in all of the sites voids 103 still are present. Similarly, FIG. 11 shows web 110 which is composed of fibers 111 bonded at sites 112 which, in turn, show only a few randomly located voids 113.

The scales of FIGS. 10 and 11 are not identical, which makes direct visual comparisons difficult. In FIG. 10, 1000 microns is equal to about 20.0 mm, whereas in FIG. 11 the same distance is equal to about 21.5 mm. It was estimated that the sides of the bond points in FIG. 10 were in the range of 1000- .1100 microns, whereas the sides of the bond points in FIG. 11 20 were in the range of 930-1160 microns.

.o ::In addition to the foregoing differences in appearance, the two webs behaved very differently under stress. When stress was applied to each web until the web tore, it was observed with the control web web 100 of FIG. 10) that 25 failure tended to occur at and within the bond points, rather than with the fibers. On the other hand, with the web of the present invention web 110 of FIG. 11), the bond points stayed intact, with the fibers elongating and then breaking.

oooo• oo Iogs GROUP II EXAMPLES SURFACE-SEGREGATABLE FIRST COMPONENTS Example 6 Preparation of Spunbonded Webs Spunbonded nonwoven webs were prepared on a pilot-scale apparatus essentially as described in U.S. Patent No.

4,340,563, which is incorporated herein by reference.

The thermoplastic polyolefin employed was the Escorene 3445 polypropylene employed in Example 1.

The first component was a trisiloxane polyether supplied by Union Carbido Corporation, Danbury, Connecticut. The material has the formula,

CH

3

CH

3

CH

3 I I I

CH

3 -Si-O-Si-O-Si-CH 3 I I I 20

CH

3

CH

2

CH

3

(CH

2 2

-O-(C

2

H

4 0) 7

CH

3 The material has a theoretical molecular weight of 602.

25 Based on gel permeation chromatography studies (American Polymer Standards Corporation, Mentor, Ohio) relative to PDMS standards, the following average molecular weights were calculated: Weight-average molecular weight: 557 Number-average molecular weight: 480 Z-average molecular weight: 614

S

Polydispersity: 1.16 The material contained an estimated 7.8 percent low molecular weight material, based on total peak area and main peak area 35 comparisons, and an estimated 20-25 percent free polyether.

Three g (1.5 x 10' 2 weight percent, based on the amount of polypropylene) of second component, CAB-O-SIL® TS-720, was dispersed in 90 g (0.45 weight percent, based on the amount of polypropylene) of the first component by means of a laboratory Waring Blender. The resulting additive system dispersion was mixed mechanically with 44 lbs. (20 kg) of polymer before introducing the mixture to the feed hopper of the extruder. Typically, a standard portable cement mixer was charged with the polymer in pellet form. The mixer then was started and cnarged with the additive system. Mixing was allowed to continue for 20 minutes, after which time the mixture was removed from the mixer and stored in plastic-lined boxes.

The more significant process variables generally were as follows: extruder temperature, 200-233'C; mel- inlet temperature, 233-236'C; throughput, 39 kg per hour; spin head temperature, 228-233°C; pump block temperature, 231-236°C; pack temperature, 237-243'C; pack pressure, 200 psig; melt temperature, 223-224°C.

Webs were obtained which had basis weights of about 27, 41, and 68 g/m 2 respectively. Each web was wettable by water immediately after its formation without the need for any postformation treatment. Thus, wettability was independent of basis weight. By comparison, when second component was omitted, it was necessary to increase the amount of first component to 200 g (1.0 weight percent, based on the amount of polypropylene) before webs were obtained which were immediately wettable without a post-formation treatment of any kind. These results are summarized in Table 6-1. Web C in the table is representative of a web lacking the second component, containing only the first component, whereas web 1 is representative of a web containing both the first component and second component.

Table 6-1 Spunbonded Webs Prepared with a Surface-Seqreqatable Additive Wt. Wt. Wt. Immediately Web 1st Comp. 2d Comp. Ratio Wettable C 1.0 None Yes 1 0.45 1.5 x 10 2 30 Yes The data in Table 6-1 demonstrate that inclusion of second component at a level of 1.5 x 10 2 permitted the reduction of first component by roughly 50 percent without affecting the wettability of the nonwoven web. It may be noted that the weight ratio of surface-segregatable first component to second component was Example 7 Preparation of Spunbonded Webs 20 Although Example 6 clearly demonstrates that the Scombination of surface-segregatable first component and second component employed permitted an approximately 50 percent reduction in the amount of first component without affecting the wettability of the nonwoven web, the data do not delineate ranges of either first component or second component which can be used. Consequently, the procedure of Example 6 was repeated a number of times, except that a different first component was used and varying amounts of first component and second component were employed.

The first component was another trisiloxane polyether which was similar to that employed in Example 6, except that the polyether moiety consisted of six ethyleneoxy units and was not end-capped.

The results are summarized in Table 7-1.

42 Table 7-1 Spunbonded Webs Prepared with Another Surface-Segreqatable Additive Wt. Wt. Wt. Immediately Web 1st Comp. 2d Comp. Ratio Wettable 1 0.75 None Yes 2 0.70 None No 3 0.45 3.0 x 10 2 15 No 4 0.40 5.0 x 10 3 80 Yes 0.35 5.0 x 10' 3 70 Yes 6 0.30 5.0 x 10 3 60 No Two of the webs made from thermoplastic compositions containing both first component and second component were not immediately wettable, i.e, webs 3 and 6. With web 3, the level of first component was within the scope of the present invention, but the weight ratio of surface-segregatable first component to second component was 15 and outside of the 20 permitted range. With web 6, the opposite was true. That is, the level of first component was outside of the permitted range, while the weight ratio was not. Webs 1 and 2 represent control webs which, under the conditions employed, demonstrate that the minimum amount of first component required to give a immediately wettable web is 0.75 percent by weight.

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. For example, the present invention 30 can be applied to a single nonwoven web or to a laminate of two or more nonwoven webs. In the latter case, only one web can contain the additive system, the first component S and second component, as described herein, or more than one web can contain such materials. By way of illustration, a three-layer nonwoven laminate finds extensive use in the manufacture of nonwoven workwear and such medical fabrics as 43 surgical gowns and drapes and the like. Such laminates generally consist of a central meltblown layer with two outer spunbonded layers. In the application of the present invention to such a laminate, the additive system can be included in only the meltblown layer, in either or both of the outer spunbonded layers, or in all three layers. Other possible permutations for webs containing the additive system involve the choice of first component which can be a TSI first component or a surface-segregatable component, depending upon the characteristics or properties desired for each web. Other modifications and changes will be apparent to those having ordinary skill in the art.

o*o• o o *o*

~C_

44 GROUP III EXAMPLES ALKYL-SUBSTITUTED POLYSILOXANE FIRST COMPONENTS Example 8 Preparation of Spunbonded Webs Spunbonded nonwoven webs were prepared on a pilot-scale apparatus essentially as described in U.S. Patent No. 4,340,563, which is incorporated herein by reference.

The thermoplastic polyolefin employed was Escorene 3445 polypropylene (Exxon Chemical Americas, Houston, Texas 77079). According to the manufacturer, the polymer has a density of 0.90 g/cc and a melt flow rate of g/10 minutes.

The first component of the improved additive system was an alkylsubstituted polysiloxane which can be represented by the following formula:

CH

3 CH, CH 3

CH

3 i

H

3 C-Si-O-(-Si-O-) 20 6 2 -Si-CH 3

CH

3

CH

2 CH 3 CH 3 20 CH 2

-(CH

2 The polysiloxane first component had a number-average molecular weight of about 11,000 and a polydispersity of about 1.3.

The second component of the improved additive system was CAB-O-SIL® 25 TS-720, a hydrophobic fumed silica supplied by Cab-O-Sil Division, Cabot Corporation, Tuscola, Illinois.

The second component was dispersed in the first component at a weight S"ratio of 20 20 parts first component and 1 part second component). The mixture of first component and second component (for a total of 2,500 g) was run through a five-liter Eiger Mark II Motormill (Eiger Corporation, Mundelein, Illinois) three times. Total milling time was approximately two hours.

A 1 2 5-g portion of the resulting additive system was milled in a ball mill to destructure the second component. The ball mill utilized 4 to 6 liter capacity ceramic jars (Paul O. Abbe, Inc., Little Falls, New Jersey) and 2-cm alumina grinding media (Coors Ceramics Company, Golden, Colorado). Destructuring was allowed to proceed for about 30 minutes.

Selected physical properties of the additive system were determined before and after destructuring, namely, viscosity and fineness of silica dispersion.

Viscosity was measured in centipoisf by means of a Brookfield LVT Viscometer using a No. 4 spindle at 25 0 C; the spindle speed was set at 6 rpm. Fineness of dispersion was measured in accordance with ASTM Test Method D 1210-79 (Reapproved 1983), Standard Test Method for Fineness of Dispersion of Pigment- Vehicle Systems; the results are reported as a Hegman Scale value. The results of these determinations are summarized in Table 8-1.

Table 8-1 Physical Properties of Additive System Before and After Destructuring *o 0 Hegman Additive System Viscosity Value Before Destructuring 4,000 After Destructuring 10,500 8+ To prepare the spunbonding feed pellets, additive system was metered (pumped) into a twin-screw extruder downstream from the extruder feed hopper at a rate equivalent to 0.3 percent by weight, based on the amount of polypropylene. The pumping rate of the additive system, the weight of the additive system container, and the polymer feed rate were monitored in order to control the level of additive system in the polymer. The resulting molten blend of polymer and additive system was extruded as a plurality of rods 2-3 mm in diameter. The rods were passed through a water bath, air dried, and pelletized. The additive system level in the resulting pellets was confirmed by elemental analysis for silicon. The pellets were stored ia plastic-lined boxes.

The more significant process variables for the spunbonding process generally were as follows: extruder temperature, 182°-238 C; melt inlet temperature, 182°-238°C; throughput, 25 kg per hour (9.7 grams per hole per minute); spin head temperature, 238°C; pack temperature, 231 0

C;

pack pressure, 490 psig; and melt temperature, 238°C Two webs were formed, each of which had a basis weight of about 38 grams per square meter (gsm): a control web prepared from virgin polypropylene, and a web prepared from polypropylene feed pellets containing 0.3 percent by weight of improved additive system, additive system in which the second component had been destructured. Each web was thermally pattern bonded at about 138°-140°C and about 12 psi. The pattern employed had 123 bonds/inch 2 (19 bonds/cm 2 covering about 16.9 percent of the web surface area.

Mean peak energy, peak load, and percent elongation values for each web were determined in accordance with Federal Test Method 5100 (Standard No.

191A). The apparatus employed was an Instron Model 1122 Universal Testing Instrument with an Instron Micron II Desk Top Console Integrator (Instron Corporation, Canton, Massachusetts). The jaw span gap was 3 inches (7.6 cm) and web sample dimensions were 3" x 6" (7.62 cm x 15.2 cm). In general, at least ten samples from each web were run. Each web was tested in both the machine direction (MD) and the cross direction The data are summarized in Tables 8-2 and 8-3.

In order to aid in an appreciation of the extent of improvement or increase in each test parameter value which resulted from the presence of improved additive system, Tables 8-2 and 8-3 include "Percent Increase" columns after each test parameter value. In each case, the percent increase (PI) was calculated by subtracting the control value from the value obtained from the inclusion of the additive system in the polymer from which the web was prepared, dividing the difference by the first control value, and multiplying the quotient by 100; PI 100 x (improved value control value)/control value.

Table 8-2 Tensile Strength Characteristics for the Webs of Example 8 Peak Peak Energy Percent Load Percent Web Direction (m-kgF) Increase (kgF Increase 1 MD 0.365 11.7 CD 0.351 7.8 2 MD 0.507 39 16.3 39 CD 0.518 48 12.9 Table 8-3 S* Tensile Strength Characteristics for the Webs of Example 8 Percent Elong. Percent 25 Web Direction Increase 1 MD 61 CD 81 2 MD 92 51 CD 102 26 Tables 8-2 and 8-3 indicate that the use of the improved additive system in accordance with the present invention results in significant increases in the tensile strength characteristics of the nonwoven webs. In general, peak energy improvements were essentially the same in both the machine and cross directions. Peak load improvements were more pronounced in the machine direction than the cross direction, while the opposite was the case with respect to 35 improvements in percent elongation.

To aid in the visualisation of the improvements demonstrated by the data in Tables 8-2 and 8-3, the data have been plotted as bar graphs as shown in FIGS. 10-12, inclusive. Both the machine direction value and the cross direction value for each web are included in each figure.

IN:LIBAAI00023:LMM Example 9 Preparation of Spunbonded Webs The procedure of Example 8 was repeated, except that the thermoplastic polymer consisted of a blend consisting of 50 weight-percent of the Escorene 3445 polypropylene employed in Example 1 and 50 weight-percent Escorene 1052 (Exxon Chemical Americas, Houston, Texas 77079). According to the manufacturer, Escorene 1052 has a melt flow rate of 5g/10 minutes. The melt flow rate of the blend was 22g/10 minutes.

Three different spunbonded webs having basis weights of about 38gsm were prepared: a first control web prepared from the polypropylene blend alone; a second control web prepared from the polypropylene blend which contained 0.3 percent by weight of additive mixture in which the second component had not been structured; and a web prepared from the polypropylene blend which contained 0.3 percent by weight of additive mixture in which the second component had been destructured.

Each web was thermally pattern bonded as described in Example 8. As in Example 8 various tensile strength characteristics were determined in accordance with Federal Test Method 5100 (Standard No 191A). In this case, the tensile strength characteristics determined were mean peak energy, peak load, peak elongation, and peak strain. The results are presented in Tables 9-1 and 9-2. As with Example 8, the tables include percent increase columns for each characteristic.

e 0 IN:LIBAAI00023:LMM Table 9r-1 Tensile Strength Characteristics for the Webs of ExamplIe 9 Web 1 Direction

MD

CD

MD

CD

MD

CD

Peak Energy (m-kgF) 0.365 0.35 1 0.418 0.408 1.304 1.182 Percent Increase 12 16 257 237 Peak Load (kzF) 11.7 7.8 9.3 7.0 18.2 12.5 Percent Increase -21 56 0 0 00** 00 Table 9-2 Tensile Strength Characteristics for the Webs of Example 9 0~ 0* Web

I

Direction

MD

CD

MD

CD

MD

CD

Peak Elong.

(cm) 5.1 7.6 7.1 10.0 11.2 15.2 Percent Increase 39 32 120 100 Peak Strain 67.1 99.7 94.6 125 146 201 Percent Increase 41 118 102 000000 It is clear from Tables 9-1 and 9-2 that the use of the improved additive system in accordance with the present invention results in significant increases in the tensile strength characteristics of the nonwoven webs. In general, the improvements are more pronounced in the machine direction, although the improvements in the cross direction are substantial. Since Tables 9-1 and 9-2 indicate percent improvements relative to the first control or web 1, Table 9-3 lists the percent improvement of each tensile strength characteristic for web 3 relative to web 2, the second control. In the table, "PI" represents "Percent Increase". Table 9-3 emphasises the importance of the particle size limitations embodiment for the second component of the improved additive system of the present invention.

Table 9-3 Percent Improvement for Web 3 Compared to Second Control Web 2 PI PI PI PI Peak Peak Peak Peak Web Direction Energy Load Elonz, Strain 3 MD 212 97 57 54 CD 190 79 58 To aid in the visualisation of the improvements demonstrated by the data in Tables 9-1 and 9-2, the tensile characteristics data have been plotted as bar graphs as shown in FIGS.

13-16, inclusive. Both the machine direction value and the cross direction value for each web are included in each figure. It is clear from FIGS. 13-16 that peak energy is more sensitive to the inclusion in the polymer of the additive system. That is, the peak energy values were increased significantly more than were the values for the other three tensile strength characteristics.

25 In order to evaluate the effects of the improved additive system on individual fibres, tenacity measurements were made on fibres isolated during the spunbonding process before being laid on the moving foraminous support. Such fibres were compared with fibres from the first control, fibres prepared from the polypropylene blend alone. The two types of fibres are referred to as "web 3 fibres" and "web 1 fibres", respectively. The results of these 30 measurements are summarised in Table 9-4 which lists the average of 25 determinations. The *o9 •table also includes percent improvement (PI) data as the third line in the table, rather than as separate columns. In each case, however, percent improvement was calculated as already described.

9 *lo o IN:-IBAA00023:LMM 51 Table 9-14 Tenacity Measurements of Single Fibres Modulus Stress Strain Sampl (GP9) QPaj a on Web 6 Fibres 2.2 183.7 174.8 Web 8 Fibres 5.2 293.7 527.4 PI 136 60 202 Consistent with past practice as an aid in the visualisation of the improvements demonstrated by the data in Table 9-4, the tenacity data have been plotted as bar graphs as shown in FIGS. 17-19. Typical stress-strain curves are shown in FIG. 20 in which curve A represents web 1 fibres and curve B represents web 3 fibres.

Having thus described the invention, numerous changes and modifications hereof will be readily apparent to those having ordinary s1dR in the art without departing from the scope or spirit of the invention.

INXLIBAA100023:LMM

Claims (49)

1. A melt-extrudable thermoplastic composition which comprises a thermoplastic polyolefin and an additive system comprising a first component and a second component, in which: said first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula, R2 R4 R5 R 7 I I I I Rl-Si--O-(Si-O)g (Si-O)--Si-R8 I I I I 1 1 R3 Rio R6 R9 wherein: R 1 -R 9 arc independently selected monovalent C 1 -C 3 alkyl groups; Ro 1 is a monovalent C 6 -C 30 alkyl group or R1l-O-(C 2 H 4 0)x(C 3 H 6 0)yR1 2 R 11 is a C 1 -C 6 alkyl o1 group; R 12 is hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 200; x represents an integer of from 1 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from about 350 to about 36 000; said second component is a hydrophobic fumed silica, in which the weight ratio of said first component to said second component is in the range of about 10 to about 300; said additive system is present in an amount of from about 0.01 to about 3 by weight based on the amount of thermoplastic polyolefm.

2. The composition of claim 1, wherein m is from about 5 to about

3. The composition of claim 1 or claim 2, wherein n is from 0 to about 100.

4. The composition of any one of the preceding claims, wherein the sum of m ard n is in the range of from 1 to about 100.

5. The composition of any one of the preceding claims, wherein said first component has a number-average molecular weight of from about 350 to about 18 000.

6. The composition of any one of claims 1 to 4, wherein said first component has a number-average molecular weight of from about 3000 to about 36 000.

7. The composition of any one of the preceding claims, wherein said first component has a polydispersity of from about 1.1 to about

8. The composition of any one of the preceding claims, wherein the weight ratio o of said first component to said second component is in the range of from about 10 to about

9. The composition of any one of claims 1 to 7, wherein the weight ratio of said first component to said second component is in the range of from about 20 to about 300.

10. The composition of any one of the preceding claims, wherein said additive system is present in an amount of from about 0.1 to about 3% by weight based on the c-A i, amount of thermoplastic polyolefin. I 53

11. The composition of any one of the preceding claims, in which the sum of m and n is in the range of from about 4 to about 100; x represents an integer of from 4 to about 25; and said first component has a molecular weight of from about 3000 to about 18 000 and is present in an amount of from about 0.1 to about 3 "by weight based on the amount of thermoplastic polyolefin.

12. The composition of any one of claims 1 to 10, which composition also is surface-segregatable, in which m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about and said first component has a molecular weigh& of from about 350 to about 1200.

13. The composition of claim 12, in which m either 1 or 2, y is 0, x is either 7 or 8, and R 11 is a monovalent C 2 -C 3 alkylene group.

14. The composition of claim 12 or claim 13, in which said first component has a molecular weight of from about 350 to about 700 and is present in an amount of fiom about 0.35 to about 1% by weight, based on the amount of thermoplastic polyolefin, and the weight ratio of said first component to said second component is in the range of from about 30 to about 100. The composition of any one of claims 1 to 10, in which substantially all of said second component is present as particles having a longest dimension in the range of from 2 about 0.001im to about lm.

16. The composition of claim 15, in which each of R 1 -R 9 is a methyl group, R 10 is a monovalent C 15 -C 22 alkyl group, m represents an integer of from about 15 to about 25, n represents an integer of from about 40 to about 80, and said first component has a number- average molecular weight of from about 8000 to about 15 000. 25 17. The composition of any one of the preceding claims, wherein said polyolefin is polypropylene.

18. The composition of claim 17, wherein each of R 1 -R 9 is a methyl group and R 1 2 is either hydrogen or a methyl group.

19. The composition of claim 17 or claim 18, in which said polypropylene is a blend of two propylene polymers having different melt flow rates.

20. The composition of claim 18, in which said blend consists of from ab:ut to about 40% by weight of a polypropylene having a melt flow rate of from about 30 to about 45 and from about 40 to about 60% by weight of a propylene having a melt flow S rate of from about 2 to about 35 21. The composition of any one of the preceding claims, in which the weight ratio of said first component to second second component is in the range of from about 10 to about

22. The composition of any one of claims 1 to 20, in which the weight ratio of said first component to said second component is in the range of from about 20 to about IN:LIBAA]00023:LMM

23. The composition of any one of the preceding claims, in which said first component is present in an amount of from about 0.1 to about 0.7% by weight based on the amount of thermoplastic polyolefin.

24. The composition of claim 23, in which said amount is from about 0.1 to about A method for preparing a nonwoven web having improved tensile strength characteristics, which method comprises: melting a thermoplastic composition which includes a thermoplastic polyolefin and an additive system having a first component and a second component; forming fibres by extruding the resulting melt through a die; drawing the fibres, and, collecting the fibres on a moving foraminous surface as a web of entangled fibres in aich: said first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula: R2 R R5 R7 Ri-Si-0-(S i-O) (Si-O),--Si-R8 I I I I R 3 Rlo R6 R 9 wherein R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is a monovalent C 6 -C 30 alkyl group or Ri1-O-(C 2 H 4 0)x(C 3 H6O)yR12; R 11 is a monovalent C 1 -C 6 alkyl group; R 12 is hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 100; x represents an integer of from 4 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from about 3000 to about 36 000; said second component is a hydrophobic fumed silica in which the weight ratio of the first component to the second component is in the range of from about 10 to about said additive system is present in an amount of from about 0.01 to about 3% by weight, based on the amount of thermoplastic polyolefin.

26. The method of claim 25, which includes the additional step of pattern bonding by the application of heat and pressure to said web of entangled fibres resulting from collection.

27. A method for preparing a nonwoven web having improved tensile strength characteristics, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system comprising a first component and a second component; forming continuous fibres by extruding the resulting me. .hrough a die; drawing said continuous fibres; collecting said continuous fibres into a tow; cutting 35 said tow into staple fibres; laying said staple fibres onto a moving foraminous surface as a IN:LIBAA100023:LMM web of entangled fibres; and pattern bonding the resulting web of entangled fibres by the application of heat and pressure in which: said first component is an alkyl-substituted polysiloxane or a polysiloxane polyether having the general formula: R2 R4 R 5 R 7 R 1 -Si-O-(S i-O)g(S i-O)fn-Si-R 8 I I I I R3 Rio R 6 R 9 wherein R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is a monovalent C 6 -C 30 alkyl group or Rll-O-(C 2 H 4 0)x(C 3 H 6 0)yRi2; R 11 is a monovalent C 1 -C 6 alkyl group; R 12 is hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 100; x represents an integer of from 4 to about 25; y represents an integer of from 0 to about 25; the ratio of x to y is equal to or greater than 2; said first component has a number-average molecular weight of from about 3000 to about 36 000; said second component is a hydrophobic fumed silica in which the weight ratio of the first component to the second component is in the range of from about 10 to about said additive system is present in an amount of from about 0.01 to about 3% by weight, based on the amount of thermoplastic polyolefin.

28. The method of any one of claims 25 to 27, in which said melt is extruded through said die at a shear rate of from about 50 to about 30 000sec- 1 and a throughput of no more than about 5.4kg/cm/hour.

29. The method of any one of claims 25 to 28, wherein m is from about 5 to about

30. The method of any one of claims 25 to 29, wherein n is from 0 to about 100.

31. The method of any one of claims 25 to 30, wherein the sum of m and n is in the range of from about 4 to about 100.

32. The method of any one of claims 25 to 31, wherein said first component has a number-average molecular weight of from about 3000 to about 18 000.

33. The method of any one of claims 25 to 32, wherein said first component has a polydispersity of from about 1.1 to about

34. The method of any one of claims 25 to 33, wherein the weight ratio of said first component to said second component is in the range of from about 20 to about

35. The method of any one of claims 25 to 34, wherein said additive system is present in an amount of from about 0.1 to about 3 by weight based on the amount of thermoplastic polyolefin. IN:\LIBAA)00023:LMM 56

36. The method of any one of claims 25 to 35, in which substantially all of the second component is present as particles having a longest Jimension in the range of from about 0.001pim to about ltm.

37. The method of any one of claims 25 to 36, wherein said polyolefin is polypropylene.

38. The method of claim 37, wherein said polypropylene is a blend of two propylene polymers having different melt flow rates.

39. The method of claim 38, in which said blend consists of from about 60 to about 40% by weight of a polypropylene having a melt flow rate of from about 30 to about 45 and from about 40 to about 60% by weight of a polypropylene having a melt flow rate of from about 2 to about A method for preparing a wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, remains wettable after its formation for at least two years at ambient temperature, and employs a reduced amount of a surface-segregatable first component, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system which comprises a surface-segregatable first component and a second component; forming fibres by extruding the resulting melt through a die at a shear rate of from about to about 30 000 sec 1 and a throughput of no more than about 5.4kg/cm/hour; drawing said fibres; and collecting said fibres on a moving foraminous surface as a web of entangled fibres; in which: said surface-segregatable first component is a polysiloxane polyether having the general formula: R2 R4 R5 R 7 R-Sii-0-Si i-O)f(Si-O)M-Si-R 8 I I I I R 3 CH 2 R 6 R 9 I S. (CH2)p-O-(C 2 H 4 0) -(C 3 H 6 )0)-Rio wherein: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; Rio is hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about 5; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; the ratio of x to y is equal to or 30 greater than 2; said surface-segregatable first component has a molecular weight of from about 350 to about 1200; and said surface-segregatable first component is present in an amount of from about 0.35 to about 3% by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said surface-segregtable first component to said second component is in the range of from about 20 to about 300. IN:LIBAA]00023:LMM 57

41. The method of claim 40, which includes the additional step of pattern bonding by the application of heat and pressure to said web of entangled fibres resulting from collection.

42. A method for preparing a wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, remains wettable after its formation for at least two years at ambient temperature, and employs a reduced amount of a surfacesegregatable first component, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefm and an additive system comprising a surface-segregatable first component and a second component; forming continuous fibres by extruding the resulting melt through a die at a shear rate of from about 50 to about 30 000sec- 1 and a throughput of no more than about 5.4kg/cm/hour; drawing said continuous fibres; collecting said continuous fibres into a tow; cutting said tow into staple fibres; laying said staple fibres onto a moving foraminous surface as a web of entangled fibres; and pattern bonding the resulting web of entangled fibres by the application of heat and pressure; wherein: said surface-segregatable first component is a polysiloxane polyether having the general formula: R2 R4 R5 R7 Rl-Si-O-(Si-O)~(Si-O)f--Si-R 8 I I I I R3 CH 2 R 6 R 9 (CH 2 )p-O-(C 2 H 4 0)-(C 3 H 6 0) -Rio in which: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is 20 hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about S 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about 5; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; the ratio of x to y is equal to or greater than 2; said surface-segregatable first component has a molecular weight of from 25 about 350 to about 1200; and said surface-segregatable first component is present in an amount of from about 0.35 to about 3% by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said surface-segregatable first component to said second component is in the range of from about 20 to about 300.

43. The method of any one of claims 40 to 42, in which said polyolefin is polypropylene.

44. The method of any one of claims 40 to 43, in which said surface-segregatable Sfirst component has a molecular weight of from about 350 to about 700. S58 A composition which comprises a first component and a second component, in which: said first component is an alkyl-substituted polysiloxane having the general formula: R2 4 Rs R R-Si-O--(Si-O)m(S i-O)--Si-R 8 R 3 Rio R 6 R 9 wherein: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is a monovalent C 6 -C 30 alkyl group; m represents an integer of from about 5 to about 50; n represents an integer of from 0 to about 200; said first component has a number-average molecular weight of from about 3000 to about 36 000; and said first component has a polydispersity of from about 1.1 to about 2.5; and said second component is a hydrophobic fumed silica, in which the weight ratio of the said first component to said second component is in the range of from about 10 to about

46. The composition of claim 45, in which substantially all of said second component is present as particles having a longest dimension in the range of from about 0.001 to about lm.

47. The composition of claim 45 or claim 46, in which each of R 1 -R 9 is a methyl group, Rio is a monovalent C 15 -C 22 alkyl group, m represents an integer of from about to about 25, n represents an integer of from about 40 to about 80, and said first component has a number-average molecular weight of from about 8 000 to about 15 000. '48. A melt-extrudable thermoplastic composition substantially as hereinbefore described with reference to any one of the examples.

49. A melt-extruded fibre prepared from the composition of any one of claims 1 to 24 or 45 to 48. S 25 50. A method of preparing a nonwoven web having improved tensile strength characteristics, said method being substantially as hereinbefore described with reference to any one of the examples.

51. A nonwoven web when prepared according to the method of claim

52. A nonwoven web comprised of fibres prepared from the composition of any one of claims 1 to 24 or 45 to 48.

53. A nonwoven web of claim 51 or 52 in which said web has been pattern bonded by the application of heat and pressure.

54. A wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, remains wettable after its formation for at least two 35 years at ambient temperature and employs a reduced amount of a surface-segregatable first IN:\LIBAA100023:LMM 59 component, which web comprises fibres prepared from the composition of any one of claims 1 to 24 or 45 to 48. An article of manufacture which comprises a nonwoven web of any one of claims 51 to 54.

56. A disposable absorbent article, at least one component of which is the nonwoven web of any one of claims 51 to 54.

57. A melt-extrudable thermoplastic composition which comprises a thermoplastic polyolefin and an additive system comprising a first component and a second component, in which: said first component is a polysiloxane polyether having the general formula, R2 R4 R5 R 7 I I I I R 3 CH 2 R 6 R 9 (CH 2 )p-O-(C 2 H 4 0)x(C 3 H 6 0)yR 10 in which: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is hydrogen or a monovalent C 1 -C 3 alkyl group; 0* *0 0 0 0***0 (3) (4) (5) to about (6) (7) (8) (9) than 2; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 100; the sum of m and n is in the range of from 1 100; p represents an integer of from 0 to about x represents an integer of from 1 to about y represents an integer of from 0 to about the ratio of x to y is equal to or greater said first component has a molecular weight of from about 350 to about 18,000; and (11) said first component is present in an amount of from about 0.1 to about 3 percent by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said first component to said second component is in the range of from about 20 to about

300. 58. The composition of claim 57,in which the sum of m and n is in the range of from about 4 to about 100; x represents an integer of from 4 to about 25; and said first component has a molecular weight of from about 3,000 to about 18,000 and is present in an amount of from about 0.1 to about 3 percent by weight, based on the amount of thermoplastic polyolefin. 59. The composition of claim 58in which said polyolefin is polyproDylene, each of R 1 -R 9 is a methyl group, and R 10 is either hydrogen or a methyl group. 60. The composition of claim 58, in which said first component is present in an amount of from about 0.1 to about 0.7 percent by weight, based on the amount of thermoplastic polyolefin. 61. The composition of claim 58, in which the weight ratio of said first component to said second component is in the range of from about 20 to about 62. The composition of claim57,which composition also is surface-segregatable, in which m represents an integer of from1l to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; x represents an integer of from 1 to about 10; y represents an integer of from 0 to about 5; and said first component has a molecular weight of from about 350 to about 1,200. 63. The composition of claim 62 in which said polyolefin is polypropylene, each of R 1 -R 9 is a methyl group, and R 10 is either hydrogen or a methyl group. 61 64. The composition of claim 62 in which m is either 1 or 2, p is either 1 or 2, y is 0, and x is either 7 or 8. The composition of claim 62 in which said first component has a molecular weight of from about 350 to about 700 and is present in an amount of from about 0.35 to about 1 percent by weight, based on the amount of thermoplastic polyolefin, and the weight ratio of said first component to said second component is in the range of from about 30 to about 100. 66. A method for preparing a nonwoven web having improved tensile strength characteristics, which method comprises: melting a thermoplastic composition which comprises S 5 a thermoplastic polyolefin and an additive system comprising a first component and a second component; forming fibers by extruding the resulting melt through a die at a shear rate of from about 50 to about 30,000 sec 1 and a throughput of no more than about 5.4 kg/cm/hour; drawing said fibers; and collecting said fibers on a moving foraminous Ssurface as a web of entangled fibers; in which: said first component is a polysiloxane polyether having the general formula, R 2 R 4 R 5 R 7 RI-Si-0-(-Si-O-)m-(-Si-O-)n-Si-R8 R 3 CH 2 R 6 R 9 (CH 2 )p-0-(C 2 H 4 0)x(C 3 H 6 0) yRI in which: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about 100; n represents an integer of from 0 to about 100; the sum of m and n is in the range of from about 4 to about 100; p represents an integer of from 0 to about x represents an integer of from 4 to about y represents an integer of from 0 to about the ratio of x to y is equal to or greater than 2; said first component has a molecular weight of from about 3,000 to about 18,000; and said first component is present in an amount of from about 0.1 to about 3 percent by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said first component to said second component is in the range of from about 20 to about 67. The method of claim 66 in which said polyolefin is polypropylene. 68. The method of claim 66 which includes the addition- al step of pattern bonding by the application of heat and pressure the web of entangled fibers resulting from step 69. A method for preparing a nonwoven web having improved tensile strength characteristics, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system comprising a first component and a second component; forming continuous fibers by extruding the resulting melt through a die at a shear rate of from about 50 to about LI 63 30,000 sec-i and a throughput of no more than about 5.4 kg/cm/hour; drawing said continuous fibers; collecting said continuous fibers into a tow; cutting said tow into staple fibers; laying said staple fibers onto a moving foraminous surface as a web of entangled fibers; and pattern bonding the resulting web of entangled fibers by the application of heat and pressure; in which: said first component is a polysiloxane polyether having the general formula, R2 R4 R5 R7 R 1 -Si-O- n-Si-R 8 S "I I I I R 3 CH 2 R 6 R 9 (CH 2 )p-O-(C 2 H 4 0) x (C 3 H 6 0) yR in which: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is hydrogen or a monovalent CI-C 3 alkyl group; m represents an integer of from 1 to about 100; 20 n represents an integer of from 0 to about 100; the sum of m and n is in the range of from about 4 to about 100; p represents an integer of from 0 to about x represents an integer of from 4 to about y represents an integer of from 0 to about the ratio of x to y is equal to or greater than 2; said first component has a molecular weight of from about 3,000 to about 18,000; and 64 said first component is present in an amount of from about 0.1 to about 3 percent by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said first component to said second component is in the range of from about 20 to about The method of claim 69 in which said polyolefin is polypropylene. 71. A method for preparing a wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, (ii) remains wettable after its formation for at least two years at ambient temperature, and (iii) employs a reduced amount of a surface-segregatable first component, which method comprises: 15 melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system which comprises a surface-segregatable first component and a second component; forming fibers by extruding the resulting melt 20 through a die at a shear rate of from about 50 to about 30,000 sec 1 and a throughput of no more than about 5.4 kg/cm/hour; drawing said fibers; and collecting said fibers on a moving foraminous surface as a web of entangled fibers; in which: said surface-segregatable first component is a polysiloxane polyether having the general formula, R2 R4 R5 R7 I I I I R 1 8 I I I I R 3 CH 2 R 6 R 9 (CH 2 )p-O-(C 2 H 4 0)x(C3H 6 )yRio in which: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; the sum of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about x represents an integer of from 1 to about y represents an integer of from 0 to about the ratio of x to y is equal to or greater than 2; 15 said surface-segregatable first component has a molecular weight of from about 350 to about 1,200; and said surface-segregatable first component is present in an amount of frcm about 0.35 to about 3 percent by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, in which the weight ratio of said surface-segregatable first component to said second component is in the range of from about 20 to about 300. 72. The method of claim 71 in which said polyolefin is I polypropylene. 73. The method of claim 71 in which said surface- segregatable first component has a molecular weight of from about 350 to about 700. 74. The method of claim 71 which includes the addition- al step of pattern bonding by the application of heat and pressure the web of entangled fibers resulting from step A method for preparing a wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, (ii) remains wettable after its formation for at least two years at ambient temperature, and (iii) employs a reduced amount of a surface-segregatable first component, which method comprises: melting a thermoplastic composition which comprises a thermoplastic polyolefin and an additive system comprising a surface-segregatable first component and a second component; forming continuous fibers by extruding the resulting melt through a die at a shear rate of from about 50 to about 30,000 sec-1 and a throughput of no more than about 5.4 kg/cm/hour; drawing said continuous fibers; S 15, collecting said continuous fibers into a tow; cutting said tow into staple fibers; laying said staple fibers onto a moving foraminous surface as a web of entangled fibers; and pattern bonding the resulting web of entangled fibers by the application of heat and pressure; *in which: said surface-segregatable first component is a polysiloxane polyether having the general formula, .25 R2 R R R7 2 4 5 R 1 8 I I I R 3 CH 2 R 6 R 9 30 (CH 2 p--(C 2 H 4 0) x(C 3 H 6 0)yRl in which: R 1 -R 9 are independently selected monovalent C 1 -C 3 alkyl groups; R 10 is hydrogen or a monovalent C 1 -C 3 alkyl group; m represents an integer of from 1 to about 4; n represents an integer of from 0 to about 3; 67 the sumi of m and n is in the range of from 1 to about 4; p represents an integer of from 0 to about x represents an integer of from 1 to about y represents an integer of from 0 to about the ratio of x to y is equal to or greater than 2; said surface-segregatable first component has a molecular weight of from about 350 to about 1,200; and said surface-segregatable first component is present in an amount of from about 0.35 to about 3 percent by weight, based on the amount of thermoplastic polyolefin; and said second component is a hydrophobic fumed silica, 15 in which the weight ratio of said surface-segregatable first component to said second component is in the range of from about 20 to about 300. 76, The method of claim 75 in which said polyolefin is po:Lypropylene. 20 77. The method of claim 75 in which said surface- segregatable first component has a molecular weight of from about 350 to about 700. *o 0* S *su S S *555* 78. of claim 79. of claim of claim A melt-extruded fiber prepared from the composition 57. A melt-extruded fiber prepared from the composition 58. A melt-extruded fiber prepared from the composition 59. A melt-extruded fiber prepared from the composition 62. 81. of claim 68 82. A nonwoven web comprised of fibers prepared from the composition of claim 57. 83. The nonwoven web of claim 82 in which said web has been pattern bonded.by the application of heat and pressure. 84. A nonwoven web comprised of fibers prepared from the composition of claim 58. The nonwoven web of claim 84 in which said web has been pattern bonded by the application of heat and pressure. 86. A nonwoven web comprised of fibers prepared from the composition of claim 59. 87. The nonwoven web of claim 86 in which said web has been pattern bonded by the application of heat and pressure. 88. A nonwoven web comprised of fibers prepared from the composition of claim 62. 89. The nonwoven web of claim 88 in which said web has been pattern bonded by the application of heat and pressure. A wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, (ii) .amains wettable after its formation for at least two years at ambient temperature, and (iii) employs a reduced amount of a surface-segregatable first component, which web comprises fibers prepared from the composition of claim 62. 91. A wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, (ii) remains wettable after its formation for at least two years at ambient temperature, and (iii) employs a 69 reduced amount of a surface-segregatable first component, which web comprises fibers prepared from the composition of claim 63. 92. A wettable nonwoven web which is wettable immediately after its formration without any post-formation treatment, iii) remains wettable after its formation for at least two years at ambient temperature, and (iii) employs a reduced amount of a surface-segregatable first component, which web comprises fibers prepared from the composition of claim 64. o r 93. An article of manufacture nonwoven web of claim 82. 94. An article of manufacture nonwoven web of claim 83. 95. An article of manufacture nonwoven web of claim 84. 96. An article of manufacture nonwoven web of claim 97. An article of manufacture nonwoven web of claim 86. 98. An article of manufacture nonwoven web of claim 87. 99. An article of manufacture nonwoven web of claim 88. 100, An article of manufacture nonwoven web of claim 89. which comprises which comprises which comprises which comprises which comprises which comprises which comprises which comprises the the the the the the the the ii L 101. A disposable absorbent article, at least one component of which is the nonwoven web of claim 102. A disposable absorbent article, at least one component of which is the nonwoven web of claim 91. 103. A disposable absorbent article, at least one component of which is the nonwoven web of claim 92. 104. -A melt-extrudable thermoplastic composition substantially as hereinbefore described with reference to any one of the Examples. 105. A method for preparing a nonwoven web having improved tensile S: 10 strength characteristics substantially as hereinbefore described with Sreference to any one of the Examples. S106. A method for preparing a wettable nonwoven web which is wettable immediately after its formation without any post-formation treatment, (ii) remains wettable after its formation for at least two 15 years at ambient temperature, and (iii),employs.a reduced amount of a 5 .\YYV e> 71 surface-segregatable first component substantially as hereinbefore described with reference to any one of the Examples. *oo 71 107. A melt-extrudable thermoplastic composition which comprises a ther- moplastic polyolefin and an improved additive system comprising a first component and a second component, in which: said first component is an alkyl-substituted polysiloxane having the general formula, R 2 R 4 R 5 R 7 II I I II I I i I R, Rio R 6 R 9 in which: Ri-Rg are independently selected monovalent C 1 alkyl groups; 15 Ri 0 is a monovalent C 6 -Co alkyl group; m represents an integer of from about 5 to about n represents an integer of from 0 to about 200; said first component has a number-average molecular weight of from about 3,000 to about 36,000; and 20 said first component has a polydispersity of from about 1.1 to about said second component is a hydrophobic fumed silica, in which the weight ratio of the said first component to said second component is in the range of from about 10 to about 70; and said improved additive system is present in an amount of from about 0.01 to about 3 percent by weight, based on the amount of thermoplastic polyole- fin. I 72 108. The composition of claim 101 in which substantially all of said second component is present as particles having a longest dimension in the range of from about 0.001 to about 1 micrometer. 109. The composition of claim 108 in which each of is a methyl group, Rio is a monovalent C, 5 -C, 2 alkyl group, m represents an integer of from about 15 to about 25, n represents an integer of from about 40 to about 80, and said firs" component has a number-average molecular weight of from about 8,000 to about 15,000. 110. The composition of claim 109 in which said polyolefin is polypropyl- ene. e** 111. The composition of claim IID in which said polypropylene is a blend of two propylene polymers having different melt flow rates. 112. The composition of claim III in which said blend cL isists of from about 60 to about 40 percent by weight of a polypropylene having a melt flow S 15 rate of from about 30 to about 45 and from about 40 to about 60 percent by weight of a polypropylene having a melt flow rate of from about 2 to about SSS*S 113. The composition of claim 10c in which said first component is present in an amount of from about 0.1 to about 0.5 percent by weight, based on the S amount of thermoplastic polyolefin. 114. The composition of claim l0 in which the weight ratio of said first component to said second component is ir the range of from about 10 to about 73 115. A method for preparing a nonwoven web having significantly improved tensile strength characteristics which comprises melting a thermoplastic composition which includes a thermoplastic polyolefin and an improved additive system having a first component and a second component; forming fibers by extruding the resulting melt through a die; drawing the fibers; and collecting the fibers on a moving foraminous surface as a web of entangled fibers; in which: the first component is a polysiloxane polyether having the general formula, R 2 R 4 R 5 R 7 15 I i I R 3 Rio R6 R9 20 in which: R,-R 9 are independently selected monovalent C 1 -C 3 alkyl groups; Rio is a monovalent C 6 -Co alkyl group; m represents an integer of from about 5 to about n represents an integer of from 0 to about 200; 25 the first component has a number-average molecular weight of from about 3,000 to about 36,000; and the first component has a polydispersity of from about 1.1 to about 74 the second component is a hydrophobic fumed silica, in which the weight ratio of the first component to the second component is in the range of from about 10 to about 70; and the improved additive system is present in an amount of from about 0.01 to about 3 percent by weight, based on the amount of thermoplastic polyole- fin. 116. The method of claim 115 in which substantially all of the second component is present as particles having a longest dimension in the range of from about 0.001 to about 1 micrometer. 117. The method of claim 116 in which said polyolefin is polypropylene. 118. The method of claim 1\7 in which said polypropylene is a blend of two propylene polymers having different melt flow rates. 119.. The method of claim tl8 in which said blend consists of from about 60 to about 40 percent by weight of a polypropylene having a melt flow rate of from about 30 to about 45 and from about 40 to Cabout 60 percent by weight of a polypropylene having a melt flow rate of from about 2 to about 120. The method of claim 115 which includes the additional step of pattern bonding by the application of heat and pressure the web of entangled fibers resulting from step 121. A method for preparing a nonwoven web having improved tensile strength characteristics, which method comprises: melting a thermoplastic composition which comprises a thermoplas- tic polyolefin and an improved additive system comprising a first component and a second component; forming continuous fibers by extruding the resulting melt through a die; drawing said continuous fibers; collecting said continuous fibers into a tow; cutting said tow into staple fibers; laying said staple fibers onto a moving foraminous surface as a web of entangled fibers; and pattern bonding the resulting web of entangled fibers by the application of heat and pressure; in which: said first component is an alkyl-substituted polysiloxane having the general formula, R R 4 R, R 20 I I i I I R, Rio R6 R9 in which: R,-R 9 are independently selected monovalent C.-C 3 alkyl groups; Rio is a monovalent C 6 -C 30 alkyl group; m represents an integer of from about 5 to about n represents an integer of from 0 to about 200; said first component has a number-average molecular weight of from about 3,000 to about 36,000; and said first component has a polydispeisity of from about 1.1 to about said second component is a hydrophobic fumed silica, in which the weight ratio of the said first component to said second component is in the range of from about 10 to about 70; and said improved additive system is present in an amount of from about 0.01 to about 3 percent by weight, based on the amount of thermoplastic polyole- fin. 122. The method of claim 121 in which substantially all of said second component is present as particles having a longest dimension in the range of from about 0.001 to about 1 micrometer. 123. The method of claim 122 in which said polyolefin is polypropylene. 124. The method of claim 12- in which said polypropylene is a blend of two propylene polymers having different melt flow rates. l 125, The method of claim Z4, in which said blend consists of from about 60 to about 40 percent by weight of a polypropylene having a melt flow rate of from about 30 to about 45 and from about 40 to about 60 percent by weight of a polypropylene having a melt flow rate of from about 2 to about C C C 126.. A melt-extruded fiber prepared from the composition of claim 107. 20 1'27. A melt-extruded fiber prepared from the composition of claim 108. C 128,. A melt-extruded fiber prepared from the composition of claim 110. 129. A melt-extruded fiber prepared from the composition of claim 111. 130. A nonwoven web comprised- of fibers prepared from the composition of claim 111. 131. The nonwoven web of claim (30, in which said web has been pattern bonded by the application of heat and pressure. 132. A nonwoven web comprised of fibers prepared from the composition of claim 108. 133. The nonwoven web of claim 132. in which said web has been pattern bonded by the application of heat and pressure. 134. A nonwoven web comprised of fibers prepared from the composition of claim 110. *4 135. The nonwoven web of claim 134 in which said web has been pattern bonded by the application of heat and pressure. 4* 0. 136. A nonwoven web comprised of fibers prepared from the composition of claim 1It. 44* 137. The nonwoven web of claim 136 in which said web has been pattern bonded by the application of heat and pressure. 138. A disposable absorbent article, at least one component of which is the nonwoven web of claim 130. o 78 139. A disposable absorbent article, at least one component of which is the nonwoven web of claim 131. 140. A disposable absorbent article, at least one component of which is the nonwoven web of claim 132. 141. A disposable absorbent article, at least one component of which is the nonwoven web of claim 133. 142. A disposable article, at least one component of which is the nonwoven web of claim 130. 143. A disposable article, at least one component of which is the 10 nonwoven web of claim 131. 9* (I 144. A disposable article, at least one component of which is the nonwoven web of claim 132. 145. A disposable article, at least one component of which is the nonwoven web of claim 133. 15 146. A composition which comprises a first component and a second component, in which: said first component is an alkyl-substituted polysiloxane having the general formula, R, R 4 RS R7 II I I Ri-Si-O-(-Si-O-)m-(-Si-O-)n-Si-R II II R 3 RIO R, in which: R 1 -Rg are independently selected monovalent C,-C 3 alkyl groups; Rio is a monovalent C 6 -C 3 0 alkyl group; m represents an integer of from about 5 to about n represents an integer of from 0 to about 200; said first component has a number-average molecular weight of from about 3,000 to about 36,000; and said first component has a polydispersity of from about 1.1 to about 2.5; and said second component is a hydrophobic fumed silica, in which the S weight ratio of the said first component to said second component is in the range of from about 10 to about 147. The composition of claim I.6 in which substantially all of said second compoient is present as particles having a longest dimension in the range of from about 0.001 to about 1 micrometer. 148. The composition of claim (47, in which each of R,-R 9 is a methyl group, R 1 is a monovalent Cs-C, alkyl group, m represents an integer of from Sabout 15 to about 25, n represents an integer of from about 40 to about 80, and said first component has a number-average molecular weight of from about 8,000 to about 15,000. Dated 11 October, 1993 Kimberly-Clark Corporation Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON 00 *:Goo 0 00 SVOM IN:.WBAAI00023:LMM THERMOPLASTIC COMPOSITIONS AND NONWOVEN WEBS PREPARED THEREFROM Abstract A melt-extrudable thermoplastic composition is provided which includes a thermoplastic polyolefin and an additive system made up of a first component and a second component, in which the first component is a defined alkyl-substituted polysiloxane or a polysiloxane polyether having a number-average molecular weight of from about 350 to about 36,000 and which is present in an amount of from about 0.01 to about 3 percent by weight, based on the amount of thermoplastic polyolefin; and the second component is a hydrophobic fumed silica, in which the weight ratio of the first component to the second component is in the range of from about 10 to about 300. In a desired en.bodiment, the particles of second component are in the range of from about 0.001 to about 1 micrometer. The composition yields, upon melt extrusion, nonwoven webs having significantly increased tensile strengths when compared to nonwoven webs prepared from the thermoplastic polyolefin alone. e ee eeo IN:ULBAAI00023:LMM