US3238553A - Filamentary articles - Google Patents

Description

March 8, 1966 E. c. BAILEY ETAL 3,238,553

FILAMENTARY ARTICLES Filed April 9, 1964 3 Sheets-Sheet 1 V: mEM S TL-I H MM N v B a WMG O R. T A K m wm March 8, 1966 E. c. BAILEY ETAL 3,238,553

FILAMENTARY ARTICLES Filed April 9, 1964 3 Sheets-Sheet 2 March 8, 1966 c. BAlLEY ETAL 3,238,553

United States Patent 3,238,553 FILAMENTARY ARTICLES Everett C. Bailey and Frank R. Cramton, both of Burlington, Vt., assignors to E. B. & A. C. Whiting Company, Burlington, Vt.

Filed Apr. 9, 1964, Ser. No. 358,468 11 Claims. (Cl. -159) This invention relates to filaments of a thermoplastic polymeric material having novel cross sectional configurations. More particularly, this invention relates to brush bristles having novel cross sectional configurations.

It is well known that heretofore the most widely used brush bristles have been made of animal hair. Due to the difiiculty and expense required to obtain and manufacture such bristles, the industry has turned to the use of bristles made from a variety of synthetic thermoplastic polymeric compositions. Because of the expense of such materials, as well as for other reasons, it is desirable that such bristles resist nesting when they are bunched or gathered into tuftsi.e., that they be high bulking. High bulking filaments presently available, however, sometimes do not possess adequate mechanical strength, resiliency and other physical properties which are required of brush bristles.

Furthermore, it is frequently desirable to flag a round bristle by shredding it on high speed knives to develop a soft and somewhat fluffy end portion on the bristle. However, it is very difiicult to flag bristles of many polymeric materials. Moreover, when flagging can be accomplished, it frequently results in a loss of mechanical stiffness of the resultant bristle.

It is an object of this invention to provide 'a filament of a thermoplastic polymeric material having a novel cross sectional configuration. It is another object of this invention to provide high bulking bristles which possess excellent flagability, mechanical strength, resiliency, liquid retention, and other physical properties required of bristles. It is a further object of this invention to provide a brush containing such bristles.

These, and other objects, are attained by the practice of this invention which, briefly, comprises providing a filament of a thermoplastic polymeric material having a cross sectional configuration comprising at least three fins radiating at approximately equal angles from a center portion. Each of the fins terminates in an expanded tip portion which has a radius at least as large as three quarters of the minimum width of the fin which connects it to the center portion. The expanded tip portion is preferably circular although it may also be other shapes such as elliptical, oval, polygonal, etc. The radius of the expanded tip portion is the distance between the center of the tip portion and a circle which would circumscribe the tip portion. To prevent nesting, it is preferred that the distance between any two adjacent tip portions be less than twice the radius of any of the tip portions.

The filaments of this invention may be formed by melt extruding the thermoplastic polymeric material through appropriately shaped extrusion orifices in a die as will be described more fully hereinafter. As examples of thermoplastic polymeric materials from which the filaments of this invention may be formed there may be mentioned polyolefins, such as polyethylene and polypropylene; polyamides such as polyhexamethylene adipamide (nylon); polyesters such as polyethylene terephthalate (Dacron); polyacrylics such as polyacrylonitrile, polyacrylamide, copolymers of acrylonitrile with methyl methacrylate, etc.; polyvinyl chloride and copolymers of vinyl chloride with other vinyl monomers; polymers of fluori- Patented Mar. 8, 1966 n-tated olefins such as polytetrafluorethylene; polystyrene; e c.

The preferred thermoplastic matri-al which may be used in the practice of this invention is isotactic polypropylene which is a high molecular weight (i.e., above about 45,000) solid polymer exhibiting a crystalline X-ray diffraction pattern. Such a polymer has a density between 0.90 and 0.94 and a melting point above about 320 F. These polymers may be prepared by methods now well known in the art such as the procedures described by G. Natta in the Journal of Polymer Science, Vol. XVI, pp. 143 to 154 (1955) and in US. Patents 2,882,263; 2,874,153; 2,913,442; 3,112,300; and 3,112,301, the disclosures of which are incorporated herein by references.

The aspects of this invention which are capable of illustration are shown in the accompany drawings.

FIGURE 1 is a schematic view of a suitable overall arrangement of apparatus for forming the filaments of this invention.

FIGURE 2 is a cross sectional view of a filament of this invention taken along line 22 of FIGURE 1.

FIGURES 3 to 6 are views of a portion of dies containing orifices which may be used in the formation of filaments of this invention.

FIGURES 7 to 9 are cross sectional views of other filaments of this invention.

FIGURE 10 is a view of a brush in which the bristles of this invention are adapted for use.

In FIGURE 1, a hopper 10 contains pellets 11 of the thermoplastic polymeric starting material such as crystalline isotactic polypropylene. The pellets 11 may be preheated in the hopper 10 if desired. From the hopper 10 the pellets are conveyed by means of a heated screw mechanism 12 to a heated extrusion head 13 which contains an extrusion die 1311. In the extrusion barrel, the temperature of the material is raised to just above its melting point. It is then extruded through a shaped orifice 14 (FIGURE 3) in the extrusion die 13a into one or more filaments 15.

The conditions of extrusion must be carefully adjusted in order to obtain filaments having the desired cross sections. Thus, the temperature of the thermoplastic material in the extrusion barrel and head 13 should be raised just high enough to result in the material having a high melt viscosity capable of extrusion. If the temperature of the material is raised substantially in excess of its melting point so that the material has a low melt viscosity when it is extruded, the extruded filament will lose the desired cross sectional shape due to the tendency of the extruded material to run together and assume a rounded configuration before it solidifies. This would result in a loss of the identity of the fins radiating from the center portion and would cause the expanded tip portions to merely be clustered about the center portion. A preferred extrusion temperature for isotactic polypropylene is about 400 F. when the filaments 15 are extruded at a linear rate of from about 18 to about 30 feet per minute from the orifices. The orifice itself may range in size from about 8 mils to about 500 mils in diameter (i.e., the diameter of a circle circumventing the orifice).

In order to solidify the filaments 15 as quickly as possible after extrusion, they are immediately quenched in a bath 16 containing a liquid non-solvent for the thermoplastic material, e.g., water. The bath 16 is maintained in a suitable tank 17 at a temperature sufiiciently low to quickly solidify the fibers 15, e.g., room temperature. An immersion time of from about 8 seconds to about 20 seconds (depending on the size of filament) of the filament 15 in the bath 16 is generally sufiicient.

By thus controlling the temperature to which the thermoplastic material is raised in the extrusion barrel so that the material has a high melt viscosity where it is extruded, and by immediately quenching the filaments l5 after extrusion so that the thermoplastic material hardens quickly, the cross section of the filament 15 approximateslthe shape of the die orifice as shown in FIG- URE 2.

Referring more specifically to FIGURE 2, it will be seen that the filament 15 has a cross sectional configuration comprising four fins 15a which radiate at approximately equal angles from a center portion 15b. Each of the fins 15a terminates in an expanded tip portion 150 which has a radius r at least as large as three quarters of the minimum width w of the fin 15a which it terminates. To prevent nesting it is preferred, that the distance D between two straight parallel lines 1 and 1 one of which is tangential to two adjacent tip portions and the other of which is tangential to the other two tip portions is such that It will be understood that filaments having cross sectional shapes other than as shown in FIGURE 2 may be produced by replacing the extrusion die 13a with one containing different shaped orifices. Thus, if the extrusion die 13a is replaced with an extrusion die 1130 containing shaped orifices 114 having a center portion 114a approximately the same shape as the expanded tips 114!) as shown in FIGURE 4, the extruded filaments 115 will have cross sections of approximately the same shape as the die orifice as shown in FIGURE 7. The dimensions of the orifice are such that the distance between the center of a circle which would circumscribe any one of the tips 114b and the periphery of a circle which would circumscribe the center portion 114a is at least as great as the width of any one of the fins 1140 plus r (r being the radius of the tip portion).

If the extrusion die 13a is replaced with an extrusion die 213a containing shaped orifices 214 having three fins 214a radiating from a center portion 214b as shown in FIGURE 5, the extruded filaments 215 will have cross sections of approximately the same shape as the die orifice as shown in FIGURE 8. When the filament has three fins radiating from a center portion, it is preferred, to prevent nesting, that the distance D between two straight parallel lines 1 and 1 one of which is tangential to two adjacent tip portions and the other of which is tangential to the third expanded tip portion is such that If the extrusion die 13a is replaced with an extrusion die 313a containing shaped orifices 314 having three fins 314a radiating from a center portion 3514b which is of approximately the same shape as the expanded tips 3140 as shown in FIGURE 6, the extruded filaments 315 will have cross sections of approximately the same shape as "the die orifice as shown in FIGURE 9.

It is known that filaments of the thermoplastic materials may have their properties enhanced by drawing or stretching the filaments to increase the molecular orientation along the fiber axis. Therefore, it is preferred to stretch orient the filaments of this invention. Referring again to FIGURE 1, this may be accomplished by transporting the filaments 15 around a stationary pin 18 in the quench bath 16 and then over the roll 19 and into the hot air conditioning oven 20. In the oven, the extruded filaments are transported over a number of rolls 21 which may be heated, in a sinuous or zigzag path, as heated air is circulated from over-head. As the filaments pass through the heating zone, each succeeding driven roll 21 over which the filaments 15 pass is driven at a slightly increased peripheral speed from that of the preceding roll so as to prevent the filaments from sagging appreciably. The primary purpose of the series of driven rolls 21 is to provide a heat exchange relationship between the filaments 15 and the heated air in the oven whereby the filaments are uniformly softened by heat. Since isotactic polypropylene has a softening temperature in the range of from about 260 F. to about 305 F., it is preferred to maintain the temperature in the oven at about 300 F. After leaving the last and uppermost driven roll 21, the filaments are snubbed with a three roll assembly 22 each roll of which is driven at about the same as or a higher peripheral speed than that of the last driven roll 21. A fast snub roll assembly 23 is provided just outside the oven 20 which is driven at a peripheral speed of about 6 to 11 times that of the assembly rolls 22. Thereby, the filaments 15 are stretched from about 6 to 11 times their length. This increases the molecular orientation along the fiber axis. The drawn, oriented filaments 15 are thereafter collected on a reel 24 which is supported on a frame 25.

Filaments having novel cross sectional shapes in accordance with this invention are high bulking. The preferred bristles of this invention will resist nesting when they are bunched or gathered in a tuft for use in a brush. Moreover, the bristles of this invention possess improved flagability since each of the relatively thin fins radiating from the center portion may be split or fractured to provide three or more separate tip portions on the end of each bristle. The resultant flagged bristle retains good mechanical stiffness for the balance of its length.

Compared to high. bulking filaments heretofore available, the filaments of this invention possess superior me chanical strength and resiliency since the expanded tip portions are on the periphery of the filament where maximum bending stress is encountered. The tip portions can operate substantially independently when bent thereby achieving better elastic recovery.

Because of their high surface to volume ratio and their novel cross sectional shape, the bristles of this invention possess good liquid retention characteristics.

The properties of the filaments of this invention, such as stiffness, flexibility, resiliency, bulking and liquid retention, may be controlled and varied widely by appropriate modifications of the design and/or dimensions of the center portion, the fins and/or the tip portions. Further property variations may be imparted by crimping or twisting the fibers.

The bristles 15 may be grouped together into tufts 30 and inserted into retaining means (i.e., holes, clamps, etc.) 31 on a rotary street brush base 32 as shown in FIG- URE 10. This brush will possess all of the advantageous properties previously ascribed to the filaments and bristles of this invention.

The following examples illustrate the best mode contemplated for carrying out this invention.

Example 1 Isotactic polypropylene having an average molecular weight of about 100,000, a density of 0.90 and a crystalline melting point of 333 F. is fed into a screw extruder of the type shown in FIGURE 1 having a 2.5-inch screw diameter. The die plate contains 9 extrusion orifices of the shape shown in FIGURE 3. The jacket is heated to a temperature of about 440 F. and the filaments are extruded at a linear rate of about 25 feet per minute from the orifices. The cross section of each of the extruded filaments has a shape as shown in FIGURE 2. The filaments are immediately passed through a quench bath maintained at a temperature of about 40 C. to solidify them. They are then fed into a heating chamber and are transported over a series of rolls. Hot air is circulated through the heating chamber, thereby heating the filaments to a temperature of about 300 F. before they leave the heating chamber. As they leave the heating chamber, the filaments are stretched to about ten times their original length. The cross sections of the drawn filaments are of approximately the same shape as the cross sections of the filaments after they are extruded. The filaments are cut into bristles and these bristles are grouped together into tufts and inserted into a brush as shown in FIGURE 10. The bristles are high bulking, resist nesting and possess good mechanical strength and resiliency.

Example 2 The process of Example 1 is repeated except that a copolymer of acrylonitrile and styrene is substituted for the polypropylene, the material is heated to a temperature of about 450 F. prior to extrusion and the material is extruded through an orifice in the die plate having a shape as shown in FIGURE 4. The cross sections of the extruded filaments have shapes as shown in FIGURE 7. The resultant filaments are high bulking.

Example 3 The process of Example 1 is repeated except that polyvinyl chloride is substituted for the polypropylene, this polymer is heated to a temperature of about 370 F. prior to extrusion and the material is extruded through an orifice in the die plate having a shape as shown in FIGURE 5. The cross sections of the extruded filaments have shapes as shown in FIGURE 8. The resultant bristles resist nesting.

Example 4 The process of Example 1 is repeated except that the polypropylene is extruded through an orifice in the die plate having a shape as shown in FIGURE 6. The cross sections of the extruded filaments have shapes as shown in FIGURE 9.

[We claim:

1. A filament of a thermoplastic polymeric material, said filament having a cross sectional configuration comprising at least three fins radiating at approximately equal angles from a center portion, each of said fins terminating in an expanded tip portion, each of said expanded tip portions having a radius at least as large as three quarters of the minimum width of said fin which it terminates, the distance between said center portion and the center of each of said expanded tip portions being greater than the radius of said tip portion, the distance between any two of said adjacent expanded tip portions being less than twice the radius of any of said tip portions.

2. A filament as defined in claim 1 wherein said thermoplastic, polymeric material is isotactic polypropylene.

3. A brush containing bristles of a thermoplastic polymeric materials, each of said bristles having a cross sectional configuration comprising at least three fins radiating at approximately equal angles from a center portion, each of said fins terminating in an expanded tip portion, each of said expanded tip portions having a radius at least as large as three quarters of the minimum width of said fin which it terminates, the distance between said center portion and the center of each of said expanded tip portions being greater than the radius of said tip portion, the distance between any two of said adjacent expanded tip portions being less than twice the radius of any of said tip portions.

4. A bristle of a thermoplastic polymeric material, said bristle having a cross sectional configuration comprising four fins radiating at approximately equal angles from a center portion, each of said fins terminating in an expanded tip portion, each of said expanded tip portions having a radius r at least as large as three quarters of the minimum width w of said fin which it terminates,

the distance between said center portion and the center of each of said expanded tip portions being greater than the radius of said tip portion, the distance between any two of said adjacent expanded tip portions being less than twice the radius of any of said tip portions.

5. A bristle as defined in claim 4 wherein said thermoplastic polymeric material is isotactic polypropylene.

6. A brush containing bristles as defined in claim 4.

7. A bristle of a thermoplastic polymeric material, said bristle having a cross sectional configuration comprising three fins radiating at approximately equal angles from'a center portion, each of said fins terminating in an expanded tip portion, each of said expanded tip portions having a radius r at least as large as three quarters of the minimum width w of said fin which it terminates, the distance between said center portion and the center of each of said expanded tip portions being greater than the radius of said tip portion, the distance between any two of said adjacent expanded tip portions being less than twice the radius of any of said tip portions.

8. A bristle as defined in claim 7 wherein said thermoplastic polymeric material is isotactic polypropylene.

9. A brush containing bristles as defined in claim 7.

10. A bristle of a thermoplastic polymeric material, said bristle having a cross sectional configuration comprising four fins radiating at approximately equal angles from a center portion, each of said fins terminating in an expanded tip portion, each of said expanded tip portions having a radius r at least as large as three quarters of the minimum width w of said fin which it terminates, the distance D between two straight parallel lines one of which is tangential to two adjacent tip portions and the other of which is tangential to the other two tip portions being such that 11. A bristle of a thermoplastic polymeric material, said bristle having a cross sectional configuration comprising three fins radiating at approximately equal angles from a center portion, each of said fins terminating in an expanded tip portion, each of said expanded tip portions having a radius r at least as large as three quarters of the minimum width w of said fin which it terminates, the distance D between two straight, parallel lines one of which is tangential to two adjacent tip portions and the other of which is tangential to the third portion being such that D D a5 5 .2s

References Cited by the Examiner UNITED STATES PATENTS 1,773,969 8/1930 Dreyfus et al. 2,149,425 3/1939 Draemann 161-177 2,508,799 5/1950 Reis 161-177 X 2,746,839 5/1956 Terry et al 57140 2,945,739 7/1960 Lehmicke 57-140 2,968,857 1/1961 Swerdloff et al. 57l40 3,059,991 10/1962 Munt 15l59.1 3,109,220 11/1963 McKinney et al. 16l177 X FOREIGN PATENTS 838,141 6/ 1960 Great Britain.

CHARLES A. WILLMUT H, Primary Examiner.

Claims (1)

1. A FILAMENT OF A THERMOPLASTIC POLYMERIC MATERIAL, SAID FILAMENT HAVING A CROSS SECTIONAL CONFIGURATION COMPRISING AT LEAST THREE FINS RADIATING AT APPROXIMATELY EQUAL ANGLES FROM A CENTER PORTION, EACH OF SAID FINS TERMINATING IN AN EXPANDED TIP PORTION, EACH OF SAID FINS TERMINATING IN AN EXPANDED TIP PORTION, EACH OF SAID EXPANDED TIP PORTIONS HAVING A RADIUS AT LEAST AS LARGE AS THREE QUARTERS OF THE MINIMUM WIDTH OF SAID FIN WHICH IT TERMINATES,

Images