Polyester Pillow Batt

Abstract

A batt having high filling power and bulk under load comprising crimped hollow polyester filaments. Critical ranges for the percent void, denier, crimp frequency, and crimp index are defined for the fibers which interact to provide batts having higher bulk under load than would be expected by virtue of the voids alone when compared with the bulk of solid fibers. Also disclosed is a process for making the batts.

Parent Case Text

REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of my copending application Ser. No. 763,841, filed Sept. 30, 1968, and now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates to filling structures and more particularly to novel filling structures containing hollow fibers.

2. Description of the Prior Art:

Synthetic hollow fibers are known to the art and the advantage of using such fibers as a filling material, i.e., essentially the same volume of fibers of the same diameter at substantially less weight, also is known. In U.S. Pat. No. 2,171,805, fibers containing bubbles are suggested for use in filling materials. U.S. Pat. No. 2,399,259 teaches that crimped hollow fibers may be converted to staple and used to prepare carded mats for filling cushions. The teachings of U.S. Pat. No. 2,999,296 include the preparation of hollow fibers that can be modified and used as a substitute for kapok fiber. The hollow-fiber filling structures of the prior art are, however, unsuitable for the production of desired, high-bulk filling structures.

In the manufacture of pillows, cushions, comforters, insulated underwear, sleeping bags and the like, a low-density, high bulk filling material is required. Further, it is desirable that the high bulk of the filling material possess, to the greatest extent possible, certain special characteristics. That is, the bulk of the material should be both an effective bulk and a resistive bulk. Effective bulk of a filling material is the property that permits the material to fully and effectively fill the space in which it is placed. Materials having a high level of effective bulk are said to have good filling power because of their ability to provide a high crown or plump appearance to the filled article. It is also desirable that the filling materials should resist deformation under an applied stress with the resistance increasing with increasing stress. Structures such as these will not have a pad-like feeling under load and will provide some measure of resilience support even under high stresses. Materials with resistive bulk show a high bulk level under load and thus provide filled articles having good support bulk or high insulative protection.

The low-density filling structures of the prior art prepared from hollow fibers are not suitable for providing the desired properties in filled articles.

In accordance with the present invention there is provided novel filling structures of hollow fibers that are eminently suited for providing filled articles having a high level of initial height while providing good support bulk under load. In addition, these novel filling structures show good bulk durability and do not readily mat in use.

SUMMARY OF THE INVENTION

This invention provides a polyethylene terephthalate pillow batt which has high filling power and bulk under load. The batt consists of intermingled hollow round filaments having a denier per filament within the range of 4 to 6, a crimp frequency within the range of five to 12 crimps per inch, and a crimp index within the range of 25 to 35. The filaments are characterized by a central continuous longitudinal void throughout the length which comprises 13 to 25 per cent of the volume of the filament and is free from collapse at crimp points.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a three-slot spinneret orifice as viewed from either top or bottom which is suitable for producing a round filament having a triangular void as shown in FIG. 2.

FIG. 3 shows a four-slot spinneret orifice as viewed from either top or bottom which is suitable for producing a round filament with a square void as shown in FIG. 4.

FIG. 5 shows a preferred form of four-slot spinneret orifice.

DESCRIPTION OF PREFERRED EMBODIMENTS

The hollow filaments used in the practice of the present invention are characterized as having a round cross-section with a hole centrally located in the filament and forming a hollow core extending throughout the length of the filament. A hollow core having a nonround cross section which approximates the shape of a triangle or square is illustrated as making possible the best filling power and support bulk values, but the present invention also provides unusually high values when the hollow cores are approximately circular in cross section. The percent "void content" of the hollow filament is the percent of the filament cross section that is hollow or, alternatively, it is 100 times the ratio of the cross-sectional area of the hollow core to the cross-sectional area of the entire filament. The fibers of this invention have a void content of about 13 percent to about 25 percent.

In order to provide suitable filling structures, the hollow fibers of this invention must be crimped. The hollow fibers can be crimped using gear crimping means or a stuffer-box crimper so as to provide fibers having at least five crimps per inch (two crimps per centimeter), e.g., from about seven to about 12 crimps per inch (2.8 to about 4.8 crimps per centimeter) and preferably from about six to about nine crimps per inch (2.4 to about 3.6 crimps per centimeter). By crimps per inch is meant the number of crimps imparted to each inch of uncrimped filament wherein a "crimp" is one cycle of deformation of the fiber, similar to the cycle of a sine wave, and will usually have peaks in a saw-toothed type of configuration. In determining crimps per inch, the total number of crimps in a staple fiber is found and the fiber length measured when the fiber is extended to just straighten out the crimps. The crimps per inch of extended fiber is then calculated. Filling structures prepared from hollow filaments having less than five crimps per inch (two crimps per centimeter) are deficient in support bulk.

The crimp index of the hollow fibers used in the practice of this invention markedly affects the bulk properties of the filling structures. Crimp index relates the length of the crimped fiber to the length of the extended fiber and thus it is influenced by crimp amplitude, crimp frequency, and the ability of the crimps to resist deformation. Crimp index is calculated from the formula

Crimp Index = [100(L.sub.1 - L.sub.2)]/L.sub.1 wherein L.sub.1 represents the extended length (fibers hanging under an added load of 0.13 .+-. .02 g.p.d. for a period of 30 seconds) and L.sub.2 represents the crimped length (length of the same fibers hanging under no added weight after relaxing for 60 seconds from the first extension). Fibers suitable for this invention have a crimp index of at least about 23 and preferably from about 25 to about 35. When the crimp index of the fibers is low, both the effective bulk and the support bulk of the filling material drop to undesirable levels.

In addition to the crimp characteristics of the hollow fibers, the denier of the fibers also is important. Fibers having a denier per filament greater than 10 have much less filling power than do fibers having values in the range of 4 to 6 denier.

While the applicant does not wish to be held thereto, it is believed that the improved results provided by the hollow fibers of this invention are associated with the stiffness properties of crimped hollow fibers. It is postulated that at relatively low void content hollow fibers and solid round fibers of the same diameter have essentially the same properties, but that as the void content increases and the fibers become more tube-like, the fibers tend to collapse at the crimp points. Such a weakened fiber would then be less capable of resisting deformation under stress. Also, as the void content increases much beyond 30 percent, it becomes increasingly difficult to produce high-quality fibers. Conceivably, variations in the fiber, such as in the shape of the hollow core, could also give rise to crimped fibers having a reduced tendency to resist an applied stress.

A preferred method for melt spinning the hollow filaments utilizes spinneret orifices of the type illustrated in FIGS. 1, 3 and 5. The molten filament segments exhibit bulging as they leave the face of the spinneret and coalesce to form the desired hollow filament. Air which enters the filament around the filament segments prior to coalescing prevents the filament from collapsing and thus maintains a hollow core. In practicing the invention, care should be taken to provide appropriate spinnerets since their dimensions are critical. Changes in the void content can be made by changing dimensions of the spinning orifice. Changes in void content can also be made by changing other process variables, e.g., void content increases with increased quenching and increased relative viscosity and decreases with increasing spinning temperature.

In crimping the hollow fibers, it is desirable to use an elevated temperature since the temperature of the yarn in the crimper influences the crimp index. The yarn temperature should be about 35.degree.-100.degree. C. and, if desired, this temperature may be obtained by running the crimper with hot (e.g., 90.degree. C.) finish or steam. When the crimped filaments are dried, and relaxed, relaxation at 130.degree.-200.degree. C. yields a crimp index within the range needed for the product of this invention.

The filling material of the present invention may be formed in ways known to the art for producing low-density structures. Preferably the low-density structure will be a batt produced by forming a web, e.g., as by garnetting, and cross-lapping the web onto a moving apron to form the batt. The batt may, for example, then be cut into sections of such a length that it will provide a sufficient mass for filling a pillow ticking in the desired manner. When such a batt section is rolled and inserted in a ticking, a pillow of outstanding aesthetics is obtained. The ticking may be of the down-proof type and can be treated with a fire retardant.

For some purposes, a more desirable pillow will be obtained if the rolled batt is first encased in a net-type ticking before the batt is inserted in the regular ticking. The net-type ticking may be of a woven, knit, or non-woven fabric. Preferably the net-type ticking will be of a marquisette fabric.

Ordinarily, an oriented web is produced continuously on a garnetting machine and is folded or cross-lapped on an apron moving across the direction of web delivery, to build up a layered batt containing usually from about two to sixteen layers. Because of the relative motions of web and apron, the successive layers of web cross each other at angles. In general practice, the size of the angle depends somewhat on the width of the batt to be made and the number of web layers desired. The angle formed will generally be in the range of from about 30.degree. to 50.degree., the angle being measured with reference to a line perpendicular to the side (edge) of the apron.

If desired, the layers may be of different widths so as to provide a greater quantity of fiber at the center section than at the edge. Such batts will, of course, result in pillows having tapered ends and are a preferred structure. Such tapered batts can be formed by any conventional means. For example, in the cross-lapping, constant long strokes and constant short strokes in a periodic sequence can be utilized. Alternatively, the means used can be to progressively reduce the size of the strokes in a repeat fashion.

The batts for pillows will normally be prepared in a width of about 2 feet so as to correspond to the length of a standard-size pillow ticking of 20 .times. 26 inches. Since machine settings of the garnett have a pronounced effect on the thickness of the web and relatively little effect on the amount of web, batting weights are commonly expressed on a weight per unit of area basis rather than density. For example, a batt weighing 0.8 ounces per square foot (0.024 grams per square centimeter) may be about 1.5 to 3.0 inches (3.8 to 7.6 centimeters) in thickness. Suitable batts for pillows have a weight of about 0.3 to 1.5 ounces per square foot (0.0092 to 0.046 grams per square centimeter) and a density of about 3.2 to 6.4 ounces per cubic foot (3.2 to 6.4 kilograms per cubic meter). Preferably, the batt will have a weight of about 0.4 ounces per square foot (0.012 grams per square centimeter) and will be about 0.9 to about 1.1 inches (2.29 to about 2.79 centimeters) in thickness.

In some instances, it may be desirable to augment the favorable properties of batts of this invention, for instance as by spraying or otherwise treating them, so as to provide the batts with a small quantity of a flexible, non-tacky resinous substance. For example, it may be desirable to spray the batt with an emulsion of an acrylic resin, such as those formed by the addition polymerization of acrylic esters, to minimize fiber movement and thus reduce the migration of fibers from the batt through the ticking. If desired, the acrylic resin binder may be used in conjunction with a lubricant such as a polysiloxane, for example, a dimethyl polysiloxane, a methylhydrogen polysiloxane and/or a polysiloxane/polyoxyethylene copolymer.

In the examples that follow, pillows are prepared from low density filling structures and subjected to tests for determination of their bulk properties. The pillows are prepared by producing a batt of a cross-lapped web. The batt is cut to suitable lengths for providing the desired weight and rolled and inserted into a cotton ticking measuring 20 .times. 26 inches (50.8 .times. 66.0 centimeters) when flat. The values for measurements on the filling structures reported in the examples are averaged values.

Pillows fabricated from filling material having the most effective bulk or filling power will have the greatest center height. The center height of the pillow under no load, H.sub.o, is determined by mashing in the opposite corners of the pillow several times and placing the pillow on the load-sensitive table of an Instron tester and measuring its height at zero load. The Instron tester is equipped with a metal-disc presser foot that is 4 inches (10.2 centimeters) in diameter. The presser foot is then caused to apply a load of 10 pounds (4.54 kilograms) to the center section of the pillow and the height of the pillow at this point is recorded as the load height, H.sub.L. Before the actual H.sub.o and H.sub.L measurements, the pillow is subjected to one cycle of 20 pounds (9.08 kilograms) compression and load release for conditioning. A load of 10 pounds (4.5 kilograms) is used for the H.sub.L measurement because it approximates the load applied to a pillow under conditions of actual use. Pillows having the highest H.sub.L values are the most resistive to deformation and thus provide the greatest support bulk.

Bulk durability is determined by submitting the filling structure to repeated cycles of compression and load release. Such repeated cycles, or workings, of the pillows are carried out by placing the pillow on a turntable associated with two pairs of 4 .times. 12 inch (10.2 .times. 30.5 centimeter) air powered worker feet which are mounted above the turntable in such a fashion that during one revolution essentially the entire contents are subjected to compression and release. Compression is accomplished by powering the worker feet with 80 pounds per square inch (5.62 kilograms per square centimeter) gauge air pressure such that they exert a static load of approximately 125 pounds (56.6 kilograms) when in contact with the turntable. The turntable rotates at a speed of 1 revolution per 110 seconds and each of the worker feet compresses and releases the filling material 17 times per minute. After being repeatedly compressed for a specified period of time, the pillow is refluffed by mashing in the opposite corners several times. As before, the pillow is subjected to a conditioning cycle and the H.sub.o and H.sub.L values determined.

The bulk properties of batts of this invention are determined by compressing the filling structure on an Instron tester and determining the height under load. The test hereinafter referred to as the total bulk range measurement (TBRM) test, is carried out by cutting 6-inch (15.25-centimeters) squares from a carded web and adding them to a stack in a cross-lapped manner until their total weight is 20 grams. The entire area is then compressed under a load of 50 pounds (22.7 kilograms). The stack height is recorded (after one conditioning cycle under a load of 2 pounds) for heights at loads of 0.01 (H.sub.i) and 0.2 (H.sub.s) pounds per square inch (0.0007 and 0.014 kilograms per square centimeter) gage. H.sub.i is the initial height and is a measure of filling power and H.sub.s is the height under load and is a measure of support bulk.

In the Examples, the percent void is measured by an apparent density method in carbon tetrachloride-N-heptane solutions.

EXAMPLE I

This example illustrates how a filling structure of this invention may be used to provide pillows with improved bulk properties at less weight or greatly improved bulk properties at equivalent weight as compared to a filling structure of solid fibers.

Hollow round filaments of polyethylene terephthalate that have a 15 percent void content are spun from a spinneret containing 199 spinning orifices of the type illustrated in FIG. 1, in which dimensions A, B and C are 0.025 inches (0.064 centimeters), 0.019 inches (0.048 centimeters), and 0.003 inches (.0076 centimeters), respectively. The filaments are spun at 285.degree. C. into quench air at room temperature and are wound up at 700 yards per minute (639 meters per minute). The filaments have a relative viscosity of 28 and contain 0.3% TiO.sub.2 (as a delustrant). The relative viscosity refers to the ratio of the viscosity of a solution of 2.15 grams of the polyester polymer in question dissolved in 20 ml. of a mixture of 10 parts of phenol and seven parts of 2,4,6-trichlorophenol to the viscosity of the phenol trichlorophenol mixture per se, measured in the same units at 25.degree. C. The hollow spun filaments are hot-wet drawn 3.7 times undrawn length at 95.degree. C., mechanically crimped in a stuffer box crimper in the presence of steam, relaxed at 150.degree. C., and cut to 2.0 inch (5.1 centimeters) staple.

Corresponding solid round filaments are spun in a conventional manner and processed to 2.0 inch (5.1 centimeter) staple under conditions similar to that described above for the hollow filaments. The solid fibers are prepared at a slightly higher denier per filament so that the two kinds of fibers have approximately the same diameter. Some typical tow properties for these two fibers are shown in Table 1.

These fibers are then used to prepare batts for pillows. Four similar kinds of pillows are prepared and tested as described hereinabove. One kind of pillow contains 17.8 ounces (504 grams) of the hollow fibers, one kind contains 17.8 ounces (504 grams) of the solid fibers, one kind contains 19.8 ounces (561 grams) of the solid fibers, and the remaining kind contains 19.8 ounces (561 grams) of the hollow fibers. Properties and results obtained are shown in Table 1A. ##SPC1##

From the above it can be seen that filling structures of this invention have bulk properties superior to filling structures of round fibers at 10 percent less weight and highly superior bulk properties at equivalent weight.

The 17.8-ounce (504-gram) pillows are then subjected to the bulk durability test previously described for 1 hour and again the H.sub.o and H.sub.L values are determined. The H.sub.o values are 7.0 inches (17.8 centimeters) and 7.1 inches (18.0 centimeters) and the H.sub.L values are 2.1 inches (5.3 centimeters) and 2.7 inches (6.9 centimeters) for the solid and the hollow fibers, respectively. It is thus seen that the filling structures of this invention have good bulk durability.

EXAMPLE II

This example illustrates the improved bulk properties that the fibers of this invention yield when in the form of carded batts.

The fibers of Example I (refer to Table 1) are formed into carded batts and subjected to the total bulk range measurement test (TBRM) as described previously.

The height at 0.01 p.s.i. is regarded as a measure of initial bulk and the height under 0.2 p.s.i. load as a measure of support bulk.

The results are given in Table 2.

TABLE 2

Filament Description TBRM heights (inches) at load of (p.s.i.): 0.01 (H.sub.i) 0.04 0.2 (H.sub.s) Solid 3.16 1.82 0.69 Hollow 3.68 2.26 1.00 Calculated Increase in 0.55 0.12 Support Bulk Actual Increase 0.52 0.31

From an inspection of the above results, it is readily apparent that the hollow filaments of this invention produce unexpected results with regard to bulk properties. Although the initial bulk (TBRM at 0.01 p.s.i.) is about the same as the calculated theoretical increase due to the 15 percent void content, the increase in the support bulk (TBRM at 0.2 p.s.i.) is a rather dramatic 2.5-fold increase over the expected calculated increase (0.31 inch actual vs. 0.12 inch expected) which is quite significant in the fiberfill art.

EXAMPLE III

This example illustrates the effect of filament void content on pillow bulk properties.

In four separate runs, hollow round fibers are prepared using procedures similar to those described in Example I, but using spinneret orifices of the type illustrated in FIG. 3 to give void contents of 9 percent, 13 percent, 23 percent and 27 percent. In all other significant aspects, the fiber characteristics are essentially equivalent.

The fibers are used to prepare webs that are cross-lapped to produce batts. Pillows are prepared from each batt and tested as described above. Results obtained are shown in Table 3.

TABLE 3

% Void Denier/ Batt Weight H.sub.o, in. H.sub.L, in. Filament Ounces 9 4.36 17.9 7.2 2.8 13 4.36 17.5 7.6 3.0 23 4.02 17.4 7.8 3.2 27 4.07 18.1 7.8 2.9

As can be seen from reference to Table 3, bulk properties increase with increasing void content at about the same batt weight. It also can be seen that the support bulk begins to deteriorate as the void content approaches 30 percent.

EXAMPLE IV

This example illustrates the bulk properties of batts of this invention and also provides a comparison with batts having unsatisfactory bulk properties.

In eight separate runs, hollow round fibers are prepared as in Example III, using spinneret orifices of the type illustrated in FIG. 3. The conditions are altered somewhat in each run so as to provide fibers having various levels of void content, crimps per inch and crimp index.

The above-produced fibers are then used to prepare carded webs which are used for providing 6-inch (15.3 centimeters) squares for testing as described above. Filament properties and the results obtained are given in Table 4. ##SPC2##

The height at 0.01 p.s.i. is a measure of the initial bulk, while the height at 0.2 is a measure of support bulk.

As can be seen from comparing Runs 1-5 with Runs 6-8, high denier fibers, and fibers with low crimp index and crimps per inch values produce a loss in one or more of the measured bulk properties. More specifically, comparing Runs 2 and 6 shows that a low crimp index (12 in Run 6 vs. 23 in Run 2) gives low initial and support bulk. Applicant's desired range of crimp index is from about 25 to 35. Likewise, comparing Runs 7 and 4 shows that whenever the crimp frequency is below applicant's range of 5-12 crimps per inch, the bulk properties drop. A comparison of Runs 8 and 1 shows the undesirable effect of high denier per filament on initial bulk properties.

EXAMPLE V

This example illustrates the desirable bulk properties of fibers of this invention spun from spinneret orifices of the type illustrated in FIG. 5.

Hollow round filaments of polyethylene terephthalate are spun from a spinneret containing 450 spinning orifices of the type illustrated in FIG. 5 in which dimensions A, B, C, D and R are 0.003 (0.0076 centimeter), 0.0067 (0.017 centimeter), 0.033 (0.084 centimeter), 0.004 (0.0102 centimeter) and 0.008 (0.020 centimeter) inches, respectively. The filaments are spun at 275.degree. C. into quench air at room temperature and are wound up at 930 yards (850 meters) per minute. The relative viscosity of the filaments is about 27. The hollow, spun filaments are hot, wet drawn 3.67X at 95.degree. C., mechanically crimped in a stuffer box crimper in the presence of steam, relaxed at 180.degree. C. and cut to 2.0-inch (5.1-centimeter) staple. Samples of the fibers so produced are characterized and found to have a denier per filament of about 4.8 and a void content of 13-15 percent. Crimping conditions are varied to provide different crimp indices. Fibers produced to have 7.1 crimps per inch and a crimp index of 35 are found to have TBRM heights of 3.95 inches H.sub.i and 0.90 inches H.sub.s. Fibers produced to have 7.1 crimps per inch and a crimp index of 26 are found to have TBRM heights of 3.85 inches H.sub.i and 0.90 inches H.sub.s.

Claims

I claim:

1. A polyethylene terephthalate pillow batt which has high filling power and bulk under load, consisting of intermingled hollow round filaments having a denier per filament within the range of 4 to 6, a saw-toothed type of crimped configuration, a crimp frequency within the range of five to 12 crimps per inch, and a crimp index within the range of 25 to 35; the filaments being characterized by a central continuous longitudinal void of nonround cross section throughout the length which comprises 13 to 25 percent of the volume of the filament and is free from collapse.

2. A polyethylene terephthalate pillow batt which has high filling power and bulk under load, consisting of intermingled, hollow, 4 to 6 denier filaments crimped in a saw-toothed type of configuration to impart a crimp frequency of six to nine crimps per inch of uncrimped filament and a crimp index within the range of 25 to 35; the filaments being characterized by a round cross section with a single hole of square shape centrally located in the filament and forming a hollow core extending throughout the length of the filament, the hollow core being 13 to 25 percent of the volume of the filament and free from collapse.