MXPA97002490A - Composition of dereptida-extruible thermoplastic propylene and a non-tramed tissue prepared by lami - Google Patents

Abstract

The present invention relates to a composition comprising a molten extrudable thermoplastic propylene composition having: a melt flow rate in a range of from about 18 to about 30 grams per ten minutes at a temperature of 190 ° C already a load of 2.16 kilograms, a polydispersity of less than 4, a Z-average molecular weight greater than 300,000 as determined by differential refractometry

Description

COMPOSITION OF DEREPTIDA-EXTRUIBLE THERMOPLASTIC PROPYLENE AND A NON-TRAMED TISSUE PREPARED FROM THE SAME Background of the Invention The present invention relates to a melt-extrudable thermoplastic composition and to the preparation of non-woven fabrics therewith.

Non-woven fabrics are porous textile type materials which are composed primarily or completely of fibers assembled in a flat sheet form. The tensile properties of such fabrics may depend on frictional forces or on a film-forming polymeric additive functioning as a binder. All or some of the fibers may be welded to the adjacent fibers by a solvent or by the application of heat and pressure. A non-woven fabric can be reinforced by a canvas, gauze, net, thread or other conventional sheet material. A non-woven fabric can be incorporated as a component in a composite structure or laminate.

Untreated fabrics are currently used in a wide variety of absorbent products or disposable protectors such as diapers, incontinent products; feminine care products, such as tampons and sanitary napkins; cleaners, towels, sterilization wraps; surgical drapes, such as surgical sheets and related items; medical garments such as hospital gowns, shoe covers and the like; and industrial clothes, to name just a few. The non-woven fabrics can be used as a single layer or as a component of a laminate or multi-layer composite. When a laminate or multilayer composite is present, frequently each layer is a non-woven fabric. Such multi-layer structures are particularly useful for cloths, towels, industrial workwear, medical garments, medical drapes and the like.

In order to improve the performance of a non-woven product, it is sometimes necessary to modify certain characteristics of the fibers of which the fabric is composed. A classic example is the modification of the hydrophobicity of the polyolefin fibers by a topical treatment of the tissue with a surfactant or through the use of a melted additive.

Efforts have been made to improve or increase the tensile strength characteristics of non-woven fabrics, particularly for such applications as sterilization wraps and industrial workwear. For example, U.S. Patent No. 5,344,862 to Ronald S. Nohr and John G. MacDonald discloses a melt additive system for thermoplastic polyolefins. The system includes two components. The first component is a polysiloxane polyether and the second component is a hydrophobic fumed silica. The two components are mixed together before being added to the polymer. The melted extrusion of the resulting composition gives either non-woven fabrics having significantly increased tensile strengths when compared to non-woven fabrics prepared from the polymer only or wettable fabrics by requiring a quantity of the first component which is significantly less than that required in the absence of the second component.

Another two component system is described in the application of the United States of America Series No. 07 / 958,630 which was filed on October 9, 1992 in the name of Ronald S. Nohr and John G. MacDonald (see also the application for PCT Patent No. US93 / 09748 having the international application No. WO 94/09066). The first component is the alkyl substituted polysiloxane used in the present invention and the second component is the hydrophobic fumed silica. The second component is desirably destructured in order to reduce the longest dimension of the silica particles to within a range of from about 0.01 to about 1 micrometer. When the additive system is mixed with the thermoplastic polyolefin, the resulting composition gives untreated fabrics having significantly increased tensile strengths when compared to non-woven fabrics prepared from the polymer alone. The thermoplastic polyolefin can be a mixture of two propylene polymers having different melt flow rates. For example, such a mixture may consist of from about 60 to about 40 weight percent, of a polypropylene having a melt flow rate of from about 30 to about 45 g / 10 minutes and from about 40 to about 60 weight percent of a polypropylene having a melt flow rate of from about 2 to about 20 g / 10 minutes.

Although any of the additive systems described above is effective in increasing the tensile strength characteristics of non-woven fabrics prepared with melt extrusion compositions consisting of a thermoplastic polyolefin and an additive system, the additive systems of two Components involve an additional processing step which requires considerable care in execution if desirable results are to be achieved.

Synthesis of the Invention The present invention addresses some of the difficulties and problems discussed above by providing the melt-extrudable thermoplastic composition described herein. The invention is based on the discovery that increased tensile strength characteristics can be achieved (a) in the absence of hydrophobic smoked silica which is required in both additive systems described above and (b) even in the absence of both the polysiloxane substituted with alkyl and the hydrophobic smoked silica required by the additive system of the serial application No. 07 / 958,630. It will be evident from the description and clauses that follow that these results are unexpected and surprising.

The melt-extrudable thermoplastic polypropylene composition provided by the present invention has a melt flow rate in a range of from about 18 to about 30 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kilograms, a polydispersity of less than 4, and a Z-average molecular weight of greater than 300,000 as determined by the differential refractometer. The melt flow rate of the composition can be in the range of from about 19 to about 22 g / 10 minutes.

The composition may include a first thermoplastic polypropylene and a second thermoplastic polypropylene. The first thermoplastic polypropylene can have a melt flow rate lower than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg. For example, the melt flow rate of the first thermoplastic polypropylene can be lower than about 15 g / 10 minutes. As another example, the melt flow rate of the first thermoplastic polypropylene can be lower than about 11 g / 10 minutes. As yet another example, the melt flow rate of the first thermoplastic polypropylene can be in the range of from about 1 to about 10 g / minutes.

The second thermoplastic polypropylene can have a melt flow rate greater than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kilograms. For example, the melt flow rate of the second thermoplastic polypropylene may be greater than about 20 g / 10 minutes. As another example, the melt flow rate of the second thermoplastic polypropylene can be in the range of from about 20 to about 50 g / 10 minutes. As yet another example, the melt flow rate of the second thermoplastic polypropylene can be in the range of from about 30 to about 40 g / 10 minutes. The ratio by weight of the first polypropylene to the second polypropylene will generally be in the range of from about 90:10 to about 10:90. By way of example, the weight ratio of the first polypropylene to the second polypropylene can be in the range of from about 80:20 to about 40:60.

The composition can include from about 0. 1 to about 1% by weight based on the weight of the polypropylene, or of the first and second thermoplastic polypropylenes, if present, of a substituted alkyl polysiloxane having the general formula: I I I R1-YES-0 (YES-0-) m - (- YES-0-) n-YES-R »l i l i in which: R1-R9 are independently selected monovalent C, - ^ alkyl groups; R10 is a group of C6-C alkyl, () monovalent; m represents an integer from about 5 to about 50; n represents an integer from about 0 to about 200; the substituted alkyl polysiloxane has a number average molecular weight of from about 3,000 to about 36,000; Y the substituted alkyl polysiloxane has a polydispersity of from about 1.1 to about 2.5.

The substituted alkyl polysiloxane provides two benefits. First, the material aids in the extrusion of the melted composition. Second, the material unexpectedly results in improved tensile strength properties when compared to the melt extrusion of a composition lacking the polysiloxane. In certain embodiments, each of R, -R is a methyl group, R10 is a monovalent C ,, -C22 alkyl group, m represents an integer from about 15 to about 25, n represents an integer from about 40 to about 80, and the substituted alkyl polysiloxane has a number average molecular weight of from about 8,000 to about 15,000.

The present invention also provides a method for forming a non-woven fabric which involves combining the melt-extrudable thermoplastic polypropylene composition composed of the first and second thermoplastic polypropylenes as described above. The composite thermoplastic composition is melted and extruded through a matrix to form continuous fibers. The continuous fibers are cooled to a solid state, pulled or attenuated, and are randomly deposited on a mobile foraminous surface as a tangled fiber fabric. The composition may include the substituted alkyl polysiloxane described above.

The present invention also provides a melted-extruded fiber and a non-woven fabric prepared from the composition described above. The non-woven fabric can be patterned by the application of heat and pressure. Also provided are a disposable absorbent article, a disposable article, a multilayer laminate, a garment, a sterilization wrap, an awning fabric, a car or boat cover, each of which includes as a component of the same a non-woven fabric of the present invention.

Brief Description of the Drawings Figure 1 is a generalized flow diagram illustrating the process of the present invention.

Figures 2-7 inclusive are bar graphs comparing the tensile strength characteristics of non-woven fabrics prepared in accordance with the present invention with such characteristics of control fabrics.

Detailed description of the invention The term "tensile strength characteristics" as used herein, has reference primary values at peak energy, peak load, percent elongation and peak voltage as determined by Federal Test Method 5100 (Standard No. 191A).

Such terms as "melted-extrudable", "melted-extruded", and the like are meant to refer to or relate to any melt extrusion process to form a non-woven fabric in which the melt extrusion to form continuous fibers is followed by the formation of the fabric, typically concurrently, on a foraminous support, for example, a bonding process with spinning. The terms also refer to or relate to processes in which the formation of tissue is an independent and separate step after the formation of the fiber; the non-woven fabrics prepared by such processes include carded and bonded fabrics and the like.

As used herein, the term "weight ratio" means the approximate weight ratio of the amount of a first thermoplastic polypropylene to the amount of a second thermoplastic polypropylene in the composition of the present invention. More specifically, the proportion by weight is expressed as the parts per 100 parts of composition of the first and second thermoplastic polypropylenes, separated by two points. Consequently, the proportion by weight has no units.

The term "melt flow rate" refers to a melt flow rate determined in accordance with ASTM Method 1238-82 Standard Test Method for flow rates of thermoplastics by extrusion of plastomer, using an extrusion plastomer model VE 4-78 (from Tinius Olsen Testing Machine Company, of Willow Grove, Pennsylvania) having an orifice diameter of 2.0955 + 0.0051 mm; Unless otherwise specified, the test conditions are at a temperature of 190 ° C and a load of 2.16 kilograms.

The term "machine direction" was used here to mean a direction which is the same as the direction of movement of the non-woven fabric during its preparation. The term "transverse direction" is used herein to mean an address which is the direction transverse to the machine, for example, an address which is perpendicular to the machine direction.

As used herein, the term "combine" or variations thereof means working the composition melted under the influence of heat and cut.

The melt-extrudable thermoplastic polypropylene composition of the present invention has a melt flow rate in a range of from about 18 to about 30 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kilograms. By way of example, the melt flow rate of the composition may be in the range of from about 19 to about 22 g / 10 minutes. The composition also has a polydispersity of less than 4, and an average molecular weight Z greater than 300,000 as determined by differential refractometry.

The composition may include a first thermoplastic polypropylene having a melt flow rate lower than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kilograms and a second thermoplastic polypropylene having a melt flow rate above. of 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kilograms. For example, the melt flow rate of the first thermoplastic polypropylene may be below about 15 g / 10 minutes. As another example, the melt flow rate of the first thermoplastic polypropylene may be below about 11 g / 10 minutes. As yet another example, the melt flow rate of the first thermoplastic polypropylene can be in the range of from about 1 to about 10 g / 10 minutes. As a practical matter, the selection of the melt flow rate of the first thermoplastic polypropylene is fundamentally a matter of commercial availability. By way of illustration, the first thermoplastic polypropylenes having melt flow rates of 5 and 10 g / 10 minutes were used in the examples.

Again by way of example, the melt flow rate of the second thermoplastic polypropylene may be greater than about 20 g / 10 minutes. As another example, the melt flow rate of the second thermoplastic polypropylene can be in the range of from about 20 to about 50 g / 10 minutes. As yet another example, the melt flow rate of the second thermoplastic polypropylene can be in the range of from about 30 to about 40 g / 10 minutes. As with the first thermoplastic polypropylene, the selection of the melt flow rate of the second thermoplastic polypropylene greatly depends on commercial availability. Again, by way of illustration, the second thermoplastic polypropylene employed in the examples has a melt flow rate of 35 g / 10 minutes.

The weight ratio of the first polypropylene to the second polypropylene is in the range of from about 90:10 to about 10:90. By way of example, the weight ratio of the first polypropylene to the second polypropylene can be in the range of from about 80:20 to about 40:60.

As indicated herein, the composition will have a melt flow rate in the range of from about 18 to about 30 g / 10 minutes. When a first and a second polypropylenes are present, such a melt flow rate is typically a function of (a) the melt flow rate of the first thermoplastic polypropylene, (b) the melt flow rate of the second thermoplastic polypropylene, (c) the weight ratio of the first polypropylene thermoplastic to the second thermoplastic polypropylene; and (d) the amounts of thermal and cutting energy applied to the composition during the combination. Consequently, a person with ordinary skill in the art can easily obtain a composition having a desired melt flow rate in the required range. Even if commercially available thermoplastic polypropylenes have limited choices of melt flow rates, the melt flow rate of the desired composition can be obtained without unnecessary experimentation by adjusting either or both of the weight ratio of the two thermoplastic polypropylenes and the amounts of thermal and cutting energy applied during mixing. Even when the cutting energy generates heat, there is still some flexibility in the mixing process since the amount of thermal energy in excess of that required to reduce the melted composition sufficiently can be controlled. Because the thermal and cutting energy preferably breaks down the higher molecular weight polymer components, increasing the amounts of thermal energy and cutting results in an increase in the melt flow rate of the composition and decreases in both average molecular weights Z and average weight.

The composition can include from about 0. 1 to about 1% by weight, based on the weight of the polypropylene, of the first or second thermoplastic polypropylenes, if present, of a substituted alkyl polysiloxane having the general formula.

R, -Si-0 (-Si-0-) m- (-YÍ-0-) n-Si-Rx R 10 R, R, in which: R, -R < , are independently selected C, -C, monovalent alkyl groups; R, 0 is a C6-C alkyl group, "monovalent; m represents an integer from about 5 to about 50; n represents an integer from about 0 to about 200; the substituted alkyl polysiloxane has a number average molecular weight of from about 3,000 to about 36,000; Y the substituted alkyl polysiloxane has a polydispersity of from about 1.1 to about 2.5.

The substituted alkyl polysiloxane provides two benefits. First, the material helps in the extrusion of the melted composition. Secondly, the material unexpectedly results in improved tensile strength properties when compared to the melt extrusion of a composition consisting only of polypropylene, for example, the first and second thermoplastic polypropylenes.

In certain modalities, each of R ^ R? it's a methyl group, R10 is a monovalent C5-C22 alkyl group, m represents an integer from about 15 to about 25, n represents an integer from about 40 to about 80, and the substituted alkyl polysiloxane has a weight average molecular number from about 8,000 to about 15,000.

The present invention also provides a method for forming a non-woven fabric. Broadly stated, the method involves combining the extruded-melted thermoplastic composition composed of a first and a second thermoplastic polypropylene as described above. The composition may also contain an alkyl polysiloxane substituted as described above. The mixing is typically carried out on a twin screw extruder according to procedures well known to those skilled in the art having ordinary skill in the art of mixing. The mixing can be carried out independently of the melt extrusion step. For example, the composition can be mixed and stored for future use. Alternatively, the composition can be mixed immediately before extrusion of the melt and then fed directly to the melt extrusion apparatus or mixed within the extrusion apparatus itself.

In the melt extrusion step, the continuous fibers are formed by extruding the thermoplastic composition mixed through a matrix. Although the array can have any desired configuration, it will most often have a plurality of holes arranged in one or more rows extending to the width of the entire machine. Such holes may be circular or noncircular in cross section.

The resulting continuous fibers are then pulled, typically by carrying them in a fluid stream having a sufficiently high velocity. The continuous fibers are cooled in a cooling fluid before being pulled; The coolant fluid is usually low pressure air. The fluid stream which pulls the fibers, usually air, may be a high velocity air stream separated from the cooling fluid or this may be a part of the cooling fluid that is accelerated by the passage into a narrow nozzle.

The pulled fibers are collected on a mobile foraminous surface as a tangled fiber tissue. The foraminous surface can be, by way of example only, a revolving drum or a continuous band or a wire grid. The latter is most commonly used on a commercial scale equipment.

Some aspects of the method of the present invention are described in greater detail in U.S. Pat. Nos. 3,016,599; 3,704,198; 3,755,527; 3,849,241; 3,341,394; 3,655,862; 3,692,618; 3,705,068; 3,802,817; 3,853,651; 4,064,605; 4,340,563; 4,434,204; 4,100,324; 4,118,531 and 4,663,220, all of which are incorporated herein by reference.

The method of the present invention is further described with reference to Figure 1 which is a generalized flow diagram illustrating a preferred embodiment of the process of the present invention.

Turning now to Figure 1, the composite thermoplastic composition is mixed from a supply 10 to a hopper 12, and then through an extruder 14, a filter 16 and a metering pump 17 to a matrix head 18 having a face of matrix 22 with a plurality of holes arranged in one or more rows generally in the direction transverse to the machine. As the continuous fibers emerge from the matrix face 22, they form a curtain of fibers 20 directed into a cooling chamber 24. In the cooling chamber 24, the fibers 20 are brought into contact with the air or other fluid cooling through an inlet 26. The cooling fluid is maintained at a temperature which is lower than the temperature of the filaments 20, typically at a temperature, for example, in the range of from about 4 ° C to about 55 ° C. The cooling fluid is supplied under pressure, for example, of less than about 12 psi, and preferably less than about 2 psi, and a portion is directed through the filament curtain 20 and removed as exhaust through of a port 28. The proportion of the supplied cooling fluid that is discharged as exhaust will depend on the composition being used and the rapidity of cooling necessary to give the desired fiber characteristics, such as denier, toughness, and the like. . In general, the greater the amount of fluid expelled, the greater the resulting filament denier and inversely the lower the proportion of fluid expelled, the filament denier will be lower.

Upon completion of the cooling, the filament curtain 20 is directed through a smooth, tapering lower end 30 of the cooling chamber to a nozzle 32 where the cooled fluid achieves a velocity of from about 45 to about 245 meters per second. The nozzle 32 extends to the full width of the machine, equivalent to the width of the die 22. The nozzle 32 is typically formed with a stationary pareid 34 and a movable wall 36, both of which extend the width of the machine. The function of the mobile wall 36 is described in United States Patent No. 4,340,563 noted above.

After exiting the nozzle 32, the filaments 20 are collected on a mobile foraminous surface such as an endless web 38 to form an unshowed web 40. Before being removed from the grid or web 38, the web 40 it passes under a compaction roller 42, optionally in conjunction with a guide roller 46. The compaction roller 42 is conveniently opposed by the support and / or forward drive roller 44 for the continuous foraminous web or the wire grid 38 Upon exiting the compaction roller 42, the fabric 40 is typically joined at the roll clamping point 48. The fabric 40 is then passed around the tension rolls 50 and 52, after which the fabric 40 is wound on the take-up roller 54.

The present invention is further described by the following examples. Such examples, however, should not be considered as limiting in any way the spirit or scope of the present invention.

Example 1 This example describes the preparation of non-woven fabrics on a pilot scale apparatus of about 14 inches (about 36 cm) as described in U.S. Patent No. 4,340,563.

Two first thermoplastic polypropylenes were studied and are mentioned here as Polymer I-A and Polymer I-B respectively. Polymer I-A was Escorene 1052 polypropylene (exxon chemical americans, Houston, Texas 77079). According to the manufacturer, the polymer has a melt flow rate of 5 g / 10 minutes. Polymer I-B was Escorene 1024 polypropylene (exxon chemical Americas, Houston, Texas 77079). According to the manufacturer, the polymer has a melt flow rate of 10 g / 10 minutes.

The second thermoplastic polypropylene, which also served as the control, was Escorene 3445 polypropylene (exxon chemical Americas, Houston, Texas 77079). The polymer reportedly had a melt flow rate of 35 g / 10 minutes. The polymer is mentioned herein as Polymer II / C.

Two compositions were prepared as summarized in Table 1. The values given in the columns under the heading "Designated Polymer Parts" are parts by weight per 100 parts of the composition.

Table 1 Summary of Melted / Extruded Compositions Designated Polymer Parts Weight Composition IA IB II / C Proportion Control 100 N / AA 60 40 60:40 B 20 80 20:80 Appropriate quantities of pellets from each of the first and second thermoplastic polypropylenes, typically made a total of about of 200 pounds (about 91 kg) and loaded into a Henschel mixer (Type FM-250B from Purnell International, Houston, Texas). The lid of the mixer was closed and the machine was switched off for three minutes. The resulting mixing was placed in fiber-lined plastic drums. The mixture was then combined in a twin screw extruder. The mixture as removed from the Henschel mixer was placed in a gravimetric feeder (Acrison Model No. 402-1200-250-BDF-1 .5-H, from Acrison, Inc., Moonachie, New Jersey). The mixture was fed by a screw feeder to a twin screw extruder Verner Pfleiderer having 57 mm screws (Verner Pfleiderer, Stuttgart, Germany). The extruder had eight independently heated zones which were set at temperatures of 204 ° C or 227 ° C, with the second to fifth zones being set at a higher temperature. The composition exited the extruder through a 15-hole plate having holes of about 3.2 mm; the temperature of the melted leaving the plate was 256 ° C. The resulting rods of the polymer composition were cooled in a water bath and then sequentially passed over two vacuum grooves and one hot air groove. The rods were then passed through a rubber roll holding point which maintained a low tension on the rods and the dry rods were fed to a Conair pelletizer (from Conair, Bay City, Michigan). The resulting pellets were screened to remove the smaller pellets of about 0.0625 inches (about 1.6 mm) and the larger ones about 0.1875 inches (about 4.8 mm). The screened pellets were mixed in a ribbon blender, passed over magnets to remove the metal particles, and put into boxes.

In order to better understand the present invention and the effects of the combination, Polymers IA and IB and Composition A were subjected to a molecular weight distribution analysis by means of gel permeation chromatography (GPC) with a refractive detector. etro differential. The results are summarized in Table 2.

Table 2 Summary of GPC Analysis Polymer No.-] Average MW Weight-Average MW P.D. Z - Average MW Polymer I-A 45,200 212,200 4.7 562,000 Polymer II / C 50,000 144,600 2.9 300,000 Composition A 42,800 166,000 3.9 421,000 Because Polymer IA was present in Composition A at a level of 60 percent by weight, the mere mixture of the two unworked polymers is expected to have a weight average molecular weight of about 185,000 and an average molecular weight of Z of around 457,000. The combination preferably resulted in decreases in the molecular weights of the higher molecular species in both components of Composition A. Consequently, the Z-average molecular weights and the weight average are closer to the corresponding values for Polymer II / C rather than to the values for Polymer IA even when the amount of a Polymer IA exceeded that of Polymer II / C. The number average molecular weight of Composition A was reduced by the combination to a value below the values for the two components of the composition.

Each composition was melted by extrudate to form a non-woven fabric joined by spinning. The most significant process variables for the spinning process were generally as follows: Extruder temperature, 175 ° C-248 ° C; melt inlet temperature, 248 ° C; production, 25 kg per hour (0.7 grams per hole per minute); spinning head temperature, 248 ° C; pump block temperature, 248 ° C; package pressure, 440 psig; Y melting temperature, 238 ° C.

Each non-woven weave had a basis weight of 1.6 ounces per square yard or osy (about 54 grams per square meter or gsm).

Peak peak energy, peak load, and percent elongation values for each tissue were determined in accordance with Federal Test Method 5100 (Standard No. 191A). The apparatus employed was an Instron Model 1122 Universal Test Instrument with an Instron Micron II Desktop Top Console Integrator (from Instron Corporation, of Canton, Massachusetts). The jaw extension separation was 3 inches (7.6 cm) and the dimensions of the tissue sample were 3 inches x 6 inches (7.62 cm x 15.2 cm). In general, at least ten samples of each tissue were run. Each fabric was tested in both machine direction (MD) and cross direction (CD). The data was summarized in Tables 3 and 4. Each tissue was identified by the name of the composition or letter from which it was prepared.

In order to assist in the appreciation of the extent of the improvement or increase in each test parameter value which resulted from the use of the composition of the present invention, Tables 3 and 4 include the "Percent Increase" columns. after each test parameter value. In each case, the percent increase (Pl) was calculated by subtracting the control value from the value obtained from the use of a composition of the present invention, dividing the difference by the first control value, and multiplying the quotient by 100.; for example, Pl = 100 x (improved value - control value) / control value Table 3 Characteristics of Tension Resistance Energy Load Peak Percent Peak Percent You went Direction (m-kgF) of Increase (kqF) of Increment lontrol MD 4.63 14.4 CD 3.40 9.9 A MD 7.58 64 19.6 36 CD 6.03 77 14.2 44 B MD 7.94 71 19.3 34 CD 6.33 86 14.7 48 Table 4 Characteristics of Tension Resistance Percent of percent You went Direction Elongation Increase Control MD 47.9 CD 60.8 A MD 62.7 31 CD 77.9 28 B MD 69.1 44 CD 82.2 36 Tables 3 and 4 demonstrate that the use of a composition of the present invention resulted in significant increases in the tensile strength characteristics of non-woven fabrics. In general, both improvements in peak energy and improvements in peak load were more pronounced in the transverse direction than in the machine direction, while the opposite was the case with respect to improvements in percent elongation . That is, the percent increase in peak energy and peak load were higher in the transverse direction than in the machine direction, while the percent increases in the percent elongation were higher in the direction of the machine that in the transverse direction. The differences in the percent of increases, however, were not great.

To assist in the visualization of the improvements demonstrated by the data in Tables 3 and 4, the data was established, as bar graphs as shown in Figures 2-4 inclusive. Both the value in the direction of the machine and the value in the transverse direction for each fabric were included in each figure.

Example 2 The procedure of Example 1 was repeated, except that different compositions were employed and a dual bank commercial spinning bonding apparatus was used. The two banks of the spinning machine were separated by about 12 feet (about 3.7 meters). The width of the machine was around 60 inches (about 1.5 meters).

The unique composition, in addition to the control, was studied. The composition (Composition C) consisted of 60 parts of a Polymer IA and 40 parts of the Polymer II / C per 100 parts of the polymer, plus 0.3 percent by weight, based on the weight of the two polymers, of a substituted alkyl polysiloxane. . The substituted alkyl polysiloxane can be represented by the formula: CHj CH-) CH3 CH ^ I I I H3C-YES-O - (- YES-O-) 20 - (- Si-O-) 62-Si-CH, I I I I CH3 CH2 CH3 CH3 CH2_ (CH2) | «; CHj The material had a number average molecular weight of about 11,000 and a polydispersity of about 1.3. Polymer II / C also served as control.

The composition was prepared and combined as described in Example 1. The polysiloxane was poured onto the polymer pellets in the Henschel mixer before mixing. The melting temperature leaving the plate was 252 ° C.

The composition and the control polymer were extruded by melting at a melting temperature of 249 ° C to form non-woven fabrics bonded by spinning. Fabrics were prepared having two different base weights, such as 1.6 ounces per square yard (about 54 grams per square meter) and about 2.5 ounces per square yard (about 85 grams per square meter). The tensile strength data is summarized in Tables 5 and 6. Each fabric was identified by the name of the composition or letter from which it was prepared. The "GSM" column indicates the basis weight of each fabric in grams per square meter.

Table 5 Characteristics of Tension Resistance Energy Load Peak Percent Peak Percent GSM Dye Direction (m-kaF) Increase (kqF) Increase Control 54 MD 4.20 16.2 ___ 12.1 85 MD 7.81 24.8 - CD 6.39 19.2 - 54 MD 9.97 137 20.8 28 CD 9.24 144 16.4 36 85 MD 14.4 84 31.8 28 CD 14.9 133 26.6 38 Table 6 Characteristics of Tension Resistance Percentage of Percentage of G GSSMM D Diirreection To Allaarrggaammiieennttoo of Increase Control 54 MD 50.0 CD 70.0 85 MD 51.9 CD 59.1 54 MD 86.8 74 CD 106 52 85 MD 80.7 55 CD 103 74 Again, the use of the composition of the present invention resulted in significant increases in the tensile strength characteristics of non-woven fabrics. This time, however, all feature improvements in tensile strength were more pronounced in the transverse direction than in the machine direction. The inclusion of the substituted alkyl polysiloxane in the composition from which the non-woven fabrics were prepared resulted in significant increases in both peak energy and percent elongation for the non-woven fabric of basis weight of 54 grams per square meter. The peak load values however did not change significantly.

For help in visualizing the improvements shown by the data in Tables 5 and 6, the data has been drawn as bar graphs as shown in Figures 5-7 inclusive. As before, both the value in the direction of the machine and the value in the transverse direction for each fabric were included in each figure.

Although the description has been made in detail with respect to the specific modalities of the same, it will be appreciated by those skilled in the art upon achieving an understanding of the foregoing, that alterations, variations and equivalents of these modalities can easily be conceived. Therefore, the scope of the present invention should be established as that of the appended claims and any equivalents thereto.

Claims (38)

R E I V I N D I C A C I O N S

1. A composition comprising a melt-extrudable thermoplastic polypropylene composition having: a melt flow rate in the range of from about 18 to about 30 g / 10 minutes at a temperature of 190 ° C and at a load of 2.16 kg; a polydispersity less than 4; Y a Z-average molecular weight greater than 300,000 as determined by differential refractometry.

2. The composition as claimed in clause 1, characterized in that it further comprises from about 0.1 to about 1 weight percent, based on the weight of the thermoplastic polypropylene, of a substituted alkyl polysiloxane having the general formula, R, -YES-0 (-YES-0-) m - (- YES-0-) n-Si-Rx R3 Rio Rft R "in which: R, -Rg are monovalent alkyl groups independently selected; R, 0 is a monovalent C C., () Alkyl group; m represents an integer from about 5 to about 50; n represents an integer from about 0 to about 200; the substituted alkyl polysiloxane has a number average molecular weight of from about 3,000 to about 36,000; Y the substituted alkyl polysiloxane has a polydispersity of from about 1.1 to about 2.5.

3. The composition as claimed in clause 1, characterized in that it further comprises: a first thermoplastic polymer having a melt flow rate lower than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg; Y a second thermoplastic polypropylene having a melt flow rate greater than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg, wherein the weight ratio of the first polypropylene to the second polypropylene is in the range of around 90:10 to around 10:90.

4. The composition as claimed in clause 2, characterized in that it also comprises: a first thermoplastic polypropylene having a melt flow rate lower than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg; Y a second thermoplastic polypropylene having a melt flow rate greater than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg, wherein the ratio by weight of the first polypropylene to the second polypropylene is in a range of around 90:10 to around 10:90.

5. The composition as claimed in clause 3, characterized in that the first polypropylene has a melt flow rate in a range of from about 1 to about 10 g / 10 minutes at a temperature of 190 ° C and at a load of 2.16 kg.

6. The composition as claimed in clause 4, characterized in that the first polypropylene has a melt flow rate in a range of from about 10 g / 10 minutes to a temperature of 190 ° C and to a charge of 2.16 kg.

7. The composition as claimed in clause 3, characterized in that the second polypropylene has a melt flow rate in a range of from about 20 to about 50 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg.

8. The composition as claimed in clause 4, characterized in that the second polypropylene has a melt flow rate in a range of from about 20 to about 50 g / 10 minutes at a temperature of 190 ° C and at a load of 2.16 kg.

9. The composition as claimed in clause 2, characterized in that each of R, -R < , is a methyl group, R10 is an alkyl C group, < -C monovalent C22, m represents an integer from about 15 to about 25, n represents an integer from about 40 to about 80, and the substituted alkyl polysiloxane has a number average molecular weight from about 8,000 to around 15,000.

10. A method for forming a non-woven fabric comprising the steps of: combina melt-extrudable thermoplastic polypropylene composition hava melt flow rate in the range of from about 18 to about 30 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg and comprising a first thermoplastic polypropylene hava melt flow rate lower than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg; Y a second thermoplastic polypropylene hava melt flow rate greater than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg where the pro weight ratio of the first polypropylene to the second polypropylene is in a range of from about from 90:10 to around 10:90; formcontinuous fibers by extrudthe combined composition through a matrix; coolthe continuous fibers to a solid state; pull the fibers; Y casually depositthe fibers on a mobile foraminous surface such as a tangled fiber fabric.

11. The method as claimed in clause 10, characterized in that the extrudable-melted thermoplastic polypropylene composition further comprises from about 0.1 to about 1 weight percent, based on the weight of the first and second thermoplastic polypropylenes, of a substituted alkyl polysiloxane havthe general formula, R2 R4 Rs R7 I I I R, -YES-0 (-YES-0-) m - (- YES-0-) n-YES-R1 < Ra ^? O R R- in which: independently selected monovalent; R, 0 is a monovalent C?-C () alkyl group; m represents an integer from about 5 to about 50; n represents an integer from about 0 to about 200; the substituted alkyl polysiloxane has a number average molecular weight of from about 3,000 to about 36,000; Y the substituted alkyl polysiloxane has a polydispersity of from about 1.1 to about 2.5.

12. The method as claimed in clause 10, characterized in that the first polypropylene has a melt flow rate in a range of from about 1 to about 10 g / 10 minutes at a temperature of 190 ° C and at a load of 2.16 kg.

13. The method as claimed in clause 11, characterized in that the first polypropylene has a melt flow rate in a range of from about 1 to about 10 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg.

14. The method as claimed in clause 10, characterized in that the second polypropylene has a melt flow rate in a range of from about 20 to about 50 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg.

15. The method as claimed in clause 11, characterized in that the second polypropylene has a melt flow rate in a range of from about 20 to about 50 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg.

16. The method as claimed in clause 11, characterized in that each of R | -R < , is a methyl group, R10 is a monovalent C-5-C22 alkyl group, m represents an integer from about 15 to about 25, n represents an integer from about 40 to about 80, and the substituted alkyl polysiloxane has a number average molecular weight of from about 8,000 to about 15,000.

17. A melted-extruded fiber prepared from the composition as claimed in clause 1.

18. A melted-extruded fiber prepared from the composition as claimed in clause 2.

19. A non-woven fabric comprisfibers prepared from the composition as claimed in clause 1.

20. The non-woven fabric as claimed in clause 19, characterized in that the fabric has a pattern joined by the application of heat and pressure.

21. A non-woven fabric comprisfibers prepared from the composition as claimed in clause 2.

22. The non-woven fabric as claimed in clause 21, characterized in that the fabric has been patterned by the application of heat and pressure.

23. A disposable absorbent article, at least one component of which is the non-woven fabric as claimed in clause 19.

24. A disposable absorbent article, at least one component of which is the non-woven fabric as claimed in clause 20.

25. A disposable absorbent article, at least one component of which is the nonwoven fabric as claimed in clause 21.

26. A disposable absorbent article, at least one component of which is the non-woven fabric as claimed in clause 22.

27. A disposable article, at least one component of which is the non-woven fabric as claimed in clause 19.

28. A disposable article, at least one component of which is the non-woven fabric as claimed in clause 20.

29. A laminate of multiple layers, at least one component of which is the non-woven fabric as claimed in clause 21.

30. A laminate of multiple layers, at least one component of which is the non-woven fabric as claimed in clause 22.

31. A garment, at least one component of which is the non-woven fabric as claimed in clause 19.

32. A garment, at least one component of which is the non-woven fabric as claimed in clause 21.

33. A sterilization envelope, at least one component of which is the non-woven fabric as claimed in clause 19.

34. A sterilization envelope, at least one component of which is the nonwoven fabric as claimed in clause 21.

35. An awning fabric, at least one component of which is the non-woven fabric as claimed in clause 19.

36. An awning fabric, at least one component of which is the nonwoven fabric as claimed in clause 20.

37. A car or boat cover, at least one component of which is the non-woven fabric as claimed in clause 19.

38. A car or boat cover, at least one component of which is the non-woven fabric as claimed in clause 20. SUMMARY A melt-extrudable thermoplastic polypropylene composition having a melt flow rate in a range of from about 18 to about 30 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg, a polydispersity of less than of 4, and a Z-average molecular weight greater than 300,000 as determined by differential refractometry. The composition may include a first thermoplastic polypropylene having a melt flow rate lower than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg and a second thermoplastic polypropylene having a melt flow rate higher than 18 g / 10 minutes at a temperature of 190 ° C and a load of 2.16 kg. The weight ratio of the first polypropylene to the second polypropylene is in a range of from about 90:10 to about 10:90. The composition may include from about 0.1 to about 1 weight percent, based on the weight of the first and second thermoplastic polypropylenes, of a defined substituted alkyl polysiloxane. A method for forming a non-woven fabric is also provided whose method involves combining the melt-extrudable thermoplastic polypropylene composition composed of the first and second thermoplastic polypropylene as described above. The composite thermoplastic composition is melted-extruded through a matrix to form continuous fibers. The continuous fibers are cooled to a solid state, pulled or attenuated, and are randomly deposited on a mobile foraminous surface as a tangled fiber fabric. The composition may include the substituted alkyl polysiloxane.