MXPA01009616A - Method of producing improved crimped polyester fibers - Google Patents

Abstract

A method is disclosed for producing polyester fibers having uniform primary and secondary crimps. The method includes the steps of advancing fibers into a stuffer box having an upper doctor blade and a lower doctor blade, positioning the upper doctor blade and the lower doctor blade such that the doctor blade gap is broad enough to permit the formation of secondary crimps and yet is narrow enough to maintain primary and secondary crimp uniformity, and then applying a longitudinal force against the advancing fibers to impart uniform primary and secondary crimps.

Description

METHOD TO PRODUCE IMPROVED CURED PE FIBERS FIBERS FIELD OF THE INVENTION The present invention relates to crimper compressing box methods for crimping polyester fibers. More particularly, the invention utilizes novel geometry of the crimper compressing box to produce crimped polyester fibers having substantially uniform primary and secondary curls. In a preferred embodiment, the method results in polyester fibers, wadding, synthetic down, yarn, carpet, and other improved products that are difficult, or even impossible to produce, using conventional polyester rip methods.

BACKGROUND OF THE INVENTION Conventional methods for producing crimped fibers using a crimper compressor box apparatus are well known, and generally include directing fibers between two driven rollers to force the fibers into a confined space (ie, the chamber of the crimper compressor box). The crimper compressing box typically includes opposing scraper blades located near a grip, which is formed by the two rollers. Side plates, and also occasionally base plates, complete the ripple chamber. As the fibers are fed through the grip in the chamber of the crimper compressor box, the fibers accumulate, decelerate and fold. The resulting folds of the fibers are referred to as "primary" curls. To facilitate the formation of primary crimps, a crimper compressing box is typically equipped with a fin, which is located towards the rear of the crimping chamber. An applied force moves the fin deeper into the curling chamber, further restricting the movement of the fibers through the crimper compressing box. This increases the forces exerted on the fibers in advance by the upper and lower scraper blades. Examples of descriptions of the crimper compressing box are given in the U.S. Patents. Nos. 5,025,538; 3,353,222; 4,854,021; 5,020,198; 5,485,662; 4,503,593; 4,395,804; and 4,115.908. It will be understood, in effect, that these patents provide a descriptive basis for the invention, rather than any limitation to it. The basic design of the crimper compressor box can be modified to include or exclude parts. Although this list of patents is by no means exhaustive, the described patents nevertheless illustrate the basic structural elements of the crimper compressing box. Frequently, conventional curling methods do not allow manipulating the accessories of the crimper compressing box to produce fibers having substantially uniform primary and secondary curls. This can result in fibers that demonstrate relatively poor curl uniformity, and consequently variable and inconsistent fiber properties. As those who have a background in quality control will understand, the use of such inferior fibers in the manufacture of certain products is undesirable. For example, as a general matter, more curly per unit length increases cohesion and, conversely, less curled per unit length decreases cohesion. Depending on the use of the fiber, the cohesion may be advantageous (eg, carding) or disadvantageous (eg, synthetic down). Regardless of the end use, the uniformity of the fibers is beneficial, since they can be kept curled per unit length at a frequency that results in optimal cohesion, either high or low. In summary, the consistent curling of the fibers means less deviation from the desired cohesion level. This promotes better quality control. To the extent that prior art describes techniques for improving the uniformity of fiber curling, the focus is exclusively on ways to improve primary crimps. However, fibers having regular primary crimps can be folded into larger deformations as the fibers advance through the chamber of the crimper compressing box. These larger deformations of the fibers are referred to as "secondary curly". Each secondary ripple fold includes a plurality of primary ripple folds. The formation of secondary curls depends, in part, on the height of space between the scraper blades.

Conventional methods that recognize that secondary crimps can be formed within a common crimper compressor box apparatus, however are not descriptive, or suggest to regulate the fold dimensions of the secondary crimps to provide desirable properties in the fibers. This is apparent when examining the fibers that have emerged from the chamber of a conventional crimper compression box - the passage of the folds is usually non-uniform. However, the present invention recognizes that the uniformity of primary and secondary crimps reduces the variability of the properties of polyester fibers. Said quality control with respect to the uniformity of the crimps improves the manufacturing operations that allow the processing of polyester fibers. As the experts in quality control will understand, reducing manufacturing variability leads to better quality products. Therefore, there is a need to produce crimped fibers having substantially uniform primary and secondary curls.

OBJECTIVES AND BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to produce polyester fibers having uniform primary and secondary curls. Another object of the invention is to produce said crimped polyester fibers using novel geometry within the chamber of a longitudinal crimper compressing box.

In a first aspect, the invention is an improved method for processing polyester fibers through a curling compressor box curling apparatus. As used herein, "polyester" is any long chain synthetic polymer formed by at least 85 weight percent of an ester of a substituted aromatic carboxylic acid. The invention overcomes the conventional crimper compressing box methods, by reducing the space between the scraper blades and by increasing the tip spacing (i.e., the distance between the tip of the scraper blade and the roller surface). This promotes the formation of substantially uniform primary and secondary curls. Surprisingly, it also improves the yield of production and the uniformity of the fibers. As a general matter, a space between the scraper blades that is too narrow prevents the formation of secondary curls. Conversely, a space between the scraper blades that is too wide results in non-uniform primary and secondary crimps. The present method establishes the height of the crimper compressor box as a function of the properties of the fibers - particularly the total deniers per width of the skein band. According to the Dictionary of Fiber & Textile Technology (Hoechst Celanese 1990), "denier total" is the denier of the skein before it is curled, and is the product of deniers by fiber and the number of fibers in the skein. The adhesion to the ratio as described herein, maintains primary and secondary curls in the advancing fibers that are substantially uniform, rather than irregular. In practice, the resulting ripple uniformity is demonstrated by the reduced movement of the fin, which maintains a constant pressure on the aggregation of fibers. The secondary ripple has amplitude and predictable non-random percentage. In general, the "curl percentage" refers to the length of a fiber segment after curling divided by the length of the same fiber segment before curling. It is thought that because the same longitudinal force produces the primary and secondary crimps, the uniformity of the secondary crimp is a good indicator of the uniformity of the primary crimp, and vice versa. In a second aspect, the invention is a polyester fiber product having uniform primary and secondary curls. This crimping uniformity significantly reduces the deviation with respect to the properties of the fibers, such as cohesion, handling and fabric strength (ie, these properties become more predictable). It is thought that, all things being equal, the uniformity of curling also increases the tenacity of breaking. Moreover, said uniformity increases the capacity of an aggregation of packed fibers to separate easily, sometimes referred to as "opening capacity". Improved curling in the crimped fiber also improves the compressive strength on a weight basis, a more desirable feature for synthetic down. As will be understood by those skilled in the art, compressive strength means the ability of a volume of material to withstand a force applied without reduction.

In many cases, the wearer of crimped polyester fibers must sacrifice a desirable property of the fibers to achieve another. The present invention facilitates this by allowing the user of crimped polyester fibers to specify the properties of the crimped fibers within narrow limits, and to satisfy said demands. In accordance with well-understood quality control principles, minimizing the lack of uniformity of polyester fiber curl facilitates the improved manufacture of products such as wadding and synthetic down. The foregoing, as well as other objects and advantages of the invention, and the manner in which they are achieved, is further specified within the following detailed description and the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal schematic view of a crimper compressing box that can be used in the present invention; Figure 2 is an enlarged detailed view of a portion of the fiber that is being crimped in the apparatus illustrated in Figure 1; Figure 3 is a top view of the skein of fibers, illustrating the formation of the secondary crimped fibers; Figure 4 is a schematic top view, taken along lines 4-4 of Figure 1, of the uniform transverse peaks defined by the secondary crimps of the fibers; Figure 5 is a side view of a fiber having primary and secondary crimps; Figure 6 is a side view of a straightened fiber having only primary crimps; and Figure 7 is a side view of a straightened fiber that lacks primary curly or secondary curls.

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for producing polyester fibers having uniform primary and secondary curls. The method utilizes a crimping compressor box curling apparatus which, although conventional in its elements, operates in a novel and non-obvious way to produce uniformly crimped fibers. Figure 1 illustrates the basic characteristics of a crimper compressor box designated extensively with the number 10. In its basic aspects, the crimper compressor box 10 includes respective rollers 11 and 12 defining a grip through which the fibers 13 advance. In most cases, the fibers 13 have not previously been crimped.

Although the description of the invention mainly highlights fibers that initially lack texture, it will be understood by those skilled in the art that the invention is not necessarily limited to said supply material. As Figure 1 further illustrates, the crimper compressor box chamber 20 comprises an upper scraper blade 14 and a lower rasp blade 15. Sidewalls, which are not illustrated in the longitudinal sectional view of Figure 1, can be Also included in the design of the curling compressor box. As will be understood by those skilled in the art, the bottom of the crimper compressing box may include a base plate, in addition to the lower scraper blade 15. The upper scraper blade 14 terminates in a fin 16, which applies a certain constant pressure to control the movement of the curly fiber layer. The pressure is applied by an appropriate air cylinder mechanism 17, or by other suitable means. The fin 16 applies sufficient force, in part by physical obstruction, to ensure that the fibers are folded into the crimper compressor box chamber 20. The basic operation of a crimper compressor box is well known in this art, and will not be repeated in detail. However, it will generally be understood that the output of the crimper compressor box is somewhat restricted compared to the input of the crimper compressor box. In this way, as the rollers 11 and 12 cause additional fibers 13 to continue advancing in the crimping compressor box 10, the fibers 13 are forced to fold to fit within the crimper compressing box chamber 20. The initial folding, which is illustrated in the detailed view of Figure 2, forms an initial crimping that is generally referred to as a primary crimper. 21. However, as more fibers 13 are advanced in the crimper compressor box 10, further folding may occur, which creates secondary crimps. These secondary curls 22 are illustrated by the largest zigzag pattern in Figure 1. Secondary crimps will not form, however, if the space between the scraper blades is less than about the thickness of the primary crimped skein (i.e. too narrow). Alternatively, if the scraper blades are too far apart, the secondary crimps will tend to form irregularly and randomly. The present method comprises applying sufficient longitudinal compressive force against the advancing fibers 13, to impart primary curls, and then continuing to apply longitudinal force against the primary crimped fibers 21 in advance, to impart a secondary curl 22 to said fibers. This is achieved by maintaining a fixed geometry between the upper and lower scraper blades 14 and 15 at a height of entry space that is sufficient to allow the secondary ripple to be formed, but which is quite narrow to ensure substantially regular secondary ripples. For example, in the curling of a skein of polyester fibers having a total denier of approximately 1, 200,000, a space setting between approximately 12 mm to 18 mm - almost half the conventional space (30 mm or more) - it forms and maintains uniform primary and secondary curls. In a preferred embodiment, the tip spacing is increased from conventional 0.05 mm, to between about 0.1 mm and 0.2 mm. As used herein, "tip separation" refers to the shortest distance between a scraper blade and its adjacent roller. With reference to Figure 1, the tips of the scraper blades 14 and 15 are located beyond the rollers 11 and 12, compared to a conventional system. In another preferred embodiment, the scraper blades 14 and 15 are located so that the space is extended approximately 2 ° to 3 ° towards the outlet. Because natural fibers tend to have significant texture properties - and of course because the typical purpose of curling is to impart more natural characteristics to synthetic fibers - the present method comprises advancing polyester fibers through the rollers. 11 and 12 and in the confined space formed by the scraper blades 14 and 15 and the rollers 11 and 12. The force required to bend particular fibers 13 into primary and secondary crimps depends mainly on the total denier of the fibers 13. Since the fibers are usually advanced as a skein, the step of maintaining the space between the upper and lower scraper blades preferably comprises adjusting the space of the scraper blade as a function of the total denier by 2.54 cm wide of the belt. of skein.

Tests of polyester skein rind indicate that if the ratio of total denier ripples by 2.54 cm width of the skein band: crimp compressor box entry height is within a particular scale, the resultant primary and secondary crimps they will be substantially uniform. The KDI unit (kilodeniers by 2.54 cm wide of the skein band that enters the crimper compressing box) characterizes a skein band. In terms of metric units, the KDMM unit (kilodeniers per millimeter of width of the skein band entering the crimper compressor box) characterizes similarly to a skein band (ie, 1 KDI = 0.0394 KDMM; 25.4 KDI = 1 KDMM). The kilodenier units are the total of denier units divided by 1000. It will be understood by those skilled in the art that the ripple ratio, as well as other relationships described herein, could be expressed by any convenient unit of measurement. A particularly good value for the ripple ratio is 16. 3 KDI (0.64 KDMM) per millimeter of height of the curling compressor box. The acceptable tolerance around this value appears to be roughly 10%. More specifically, it has been determined that the space of the scraper blade at the inlet of the crimper compressor box is preferably adjusted to a height determined by the following equation: height of space (mm) = (KDI -HX), where the variable X has a value between approximately 14.5 KDI / mm and approximately 18 KDI / mm.

Alternatively, the above equation can be expressed using only metric units: space height (mm) = (KDMM + X), where variable X has a value between about 0.57 KDMM / mm and about 0.71 KDMM / mm. In preferred embodiments, the value of variable X is approximately 16.3 KDI / mm (0.64 KDMM / mm). As will be understood by those skilled in the art, the equation mentioned above is necessarily adjusted for its application to hollow polyester fibers. In particular, a hollow fiber having a certain cross-sectional area will have a proportionally smaller weight per unit length with respect to a solid fiber having the same composition and having the same cross-sectional area. This linear relationship can be expressed as a function of the solid fraction of the hollow fiber: denier (hollow fiber) = denier (solid fiber) • s, where the hollow fiber and the solid fiber have the same composition and have the same area in cross section, and where s is the ratio of the mass of the hollow fiber: the mass of the solid fiber (ie, the solid fraction of the hollow fiber). Therefore, the modified ripple equation for hollow fibers is the following: height of space (mm) = (KDI - s) H- (X), where the variable s is the solid fraction of the hollow fibers, and the variable X has a value between approximately 14.5 KDI / mm and approximately 18 KDI / mm. Alternatively, the above equation can be expressed using only metric units: space height (mm) = (KDMM + s) H- (X), where the variable s is the solid fraction of the hollow fibers, and the variable X has a value between about 0.57 KDMM / mm and about 0.71 KDMM / mm. Note that this is the most general form of the ripple equation (ie, solid fibers have a solid fraction s of 1). In preferred embodiments, the solid fraction s of the hollow polyester fibers is between about 0.72 and about 0.91. As an exemplary and typical system for the invention, if a skein formed of a plurality of polyester fibers having a total denier of about 1,790,000 is advanced in a crimper compressing box approximately 180 mm wide, the KDI is approximately 252 (ie, 1, 790 kilodeniers - 180 mm), and the KDMM is approximately 9.94 (ie, 1, 790 kilodeniers - - 180 mm). In this way, the space height should be maintained between approximately 14 mm and approximately 17 mm. The processing of the fibers in this manner produces improved fibers having uniform primary and secondary curls. Thus, in another aspect, the invention is a polyester fiber having a weight: length ratio less than about 500 deniers per filament (DPF), substantially uniform primary crimps between about 1.5 and 15 crimps per 2.54 cm (CPLI) - that is, between about 0.6 and 6 crimps per linear centimeter (CPLCM) - and substantially uniform secondary crimps. In a preferred embodiment, the invention is a polyester fiber having a weight ratio: length of about 15 DPF, substantially uniform primary crimps of about 3.9 crimps per 2.54 cm (1.5 CPLCM), and substantially uniform secondary crimps. In another preferred embodiment, the invention is a polyester fiber having a weight ratio: length of about 6 DPF, substantially uniform primary crimps of about 6 or 7 crimps per 2.54 cm (about 2.4 or 2.8 CPLCM), and secondary crimps substantially uniforms Following this novel ripple technique, the secondary ripple 22, which is random in fibers processed through typical crimper compressor arrangements, tends to be maintained in an extremely regular pattern. This is illustrated by the detailed view of Figure 3. Further, the crimped fibers emerging from the crimper compressing box possess secondary crimps that are exceptionally uniform in the transverse direction. More specifically, the secondary crimps 22 are formed in periodic rows that are parallel to the grip (i.e., extending across the width of the chamber of the crimper compressor box). This is illustrated by the detailed view of Figure 4, which shows the orientation of the peaks of the secondary crimps. Those skilled in the art will recognize the uniformity of primary and secondary crimps, by observing the skein as it leaves the crimper compressing box. In accordance with the test method of Dr. Vladimir Raskin, the lack of uniformity of the ripple can be defined by the deviation of the ripple from the average ripple frequency (ie, crimps per inch or crimps per centimeter). This is represented by Kn, a coefficient of non-uniformity of the primary crimps, and which is calculated by extending a section of crimped skein sample, preferably between about 50 centimeters and about 100 centimeters, so that the secondary crimps disappear. To achieve a value of Kn >; A tape measure having small graduations is first placed along the length of a skein section, preferably along the midline of the skein, since the ringleability is usually more stable at that level. Then, this section of curly skein is divided into equal subsections. For simplicity, the subsections are typically one centimeter or 2.54 centimeters in length. However, it should be understood that since Kn is an averaged value, any convenient unit of length could be used to calculate Kn. The primary curls are then calculated per unit length for the successive subsections along the skein (for example, crimped per centimeter for each skein subsection). Then, an average value of crimps per unit length (Xm) is determined, summing the total of crimps along the section of the skein of sample, and dividing by the length of the skein section. The percentage of absolute deviation is then calculated from Xm for each subsection of the skein. Kn is defined as the sum of the percentage of absolute deviations from Xm, divided by the number of sections of the skein analyzed. In this way, Kn reflects the average deviation from Xm, the average value of crimps per unit of length, to a relative position through the skein (for example, along the right edge or, preferably, as long of the middle line). As an illustration of how Kn is calculated, reference should be made to Table 1, which characterizes a skein section of 10 centimeters that has 10 subsections: TABLE 1 According to this illustrative example, Xm, the average value of crimps per unit length is 2.4 crimps per centimeter. The percentage of absolute deviation from Xm is 259 percent for the 10 subsections. In this way, the Kn for this hank section of 10 centimeters is approximately 26% (ie, 259% + 10). In addition, the values of Kn for various positions across the skein width can be averaged to result in a pound Kn value. For example, Kn is often calculated in the five positions through the skein, which divide the width of the skein into quadrants along (ie, Kn in the middle line of the skein, Kn in each of the two edges of the skein, and Kn in each of the two midpoints defined by the middle line of the skein and the two edges of the latter). The grouped Kns is simply the average of the five Kn values. Table 2 shows said grouped Kns values for crimped polyester fibers in a conventional crimper compressing box, which has an inlet height of 31 millimeters, and pooled Kn5 values for crimped polyester fibers in the improved crimper compressor box, the which has an entrance height of 13 millimeters. Referring to table 2, note that examples 1 to 7 used conventional crimper compressor box geometry, while examples 8 and 9 used the geometry of the novel crimper compressor box of the present invention. In summary, the Kn5 for the improved polyester fibers of the present invention (8.3% and 10.8%) is considerably lower than the Kns for conventional polyester fibers (13.8% to 17.4%).

TABLE 2 * 1 CPU is converted to approximately 0.4 crimps per linear centimeter (CPLCM).

As will be understood by those skilled in the art, reducing the variability of the process improves manufacturing processes. In this way, the regular characteristics of the primary and secondary crimped fibers, particularly a plurality of said fibers, are advantageous for end-use applications. In addition, fibers having uniform primary and secondary curls demonstrate improved fabric strength and handling. In another aspect, the invention is wadding formed from a plurality of polyester fibers having uniform primary and secondary ripples. As will be understood by those skilled in the art, wadding is a soft, bulky assembly of fibers. It is usually carded, and is often marketed in sheets or rolls. The wadding is used for outer lining, padding, thermal insulation, elastic articles (eg, pillows, cushions and furniture), and other applications. The uniformly crimped fibers are manufactured in a more predictable way in batting, in part because a mass of said fibers has a regular opening capacity. In yet another aspect, the invention is synthetic down formed from a plurality of polyester fibers having uniform primary and secondary curls. As will be understood by those skilled in the art, synthetic down is an aggregation of manufactured fibers that has been designed to be used as a filler material in pillows, mattresses, blankets, sleeping bags, quilted clothing, and the like. The improved synthetic down of the present invention has less non-crimped fibers, compared to conventional synthetic down. The non-crimped fibers contribute little to the compressive strength, but nevertheless increase the weight of the synthetic down. In this way, the use of the fibers of the present invention means that less synthetic down is needed to achieve a desired level of resistance to compression. In other words, the synthetic down formed in accordance with the present invention tends to have greater compressive strength on a basis in weight, than conventional synthetic down. The use of less synthetic down, maintaining an acceptable resistance to compression, reduces the costs of synthetic down. In another aspect, the fibers and skein uniformly crimped according to the present invention, can be formed into yarns by any suitable spinning method, which does not adversely affect the desired properties. In turn, the yarns can be formed into fabrics or, given their advantageous properties, carpets or other textile products. As noted, control of the performance of primary and secondary curls is important, because deviations from the values of the primary primary and secondary curls can cause manufacturing problems. For example, the control of primary curls is an especially important consideration in operations for the use of synthetic down. Users of synthetic polyester down have typically demand specifications. In general, as the ripple frequency becomes excessive, masses of unopened fibers clog the fans, forcing them to turn off and clear. By way of illustration, in some fans, polyester fibers of 15 DPF, 3.9 CPLI (1.5 CPLCM) have a very good opening capacity and very uniform damping quality, while polyester fibers of 15 DPF, 4.0 CPLI (1.6 CPLCM) cause obstructions and entanglements in the fan, as well as cushions filled with lumps and poorly filled. In addition, when the ripple frequency of the polyester fibers increases to 4.8 CPLI (1.9 CPLCM), clogging and entanglement occurs in these fans, typically causing the machine to idle. The resulting cushions are poorly filled, especially at the corners, and tend to be full of lumps. In other fans, polyester fibers of 15 DPF, 4.0 CPLI (1.6 CPLCM) have good opening capacity and can fill the cushions evenly, while polyester fibers of 15 DPF, 4.5 CPLI (1.8 CPLCM), although they have good opening capacity, are distributed sparingly, causing lumps and gaps in the cushions. In summary, users of polyester fibers typically have few specifications with which polyester fibers are better processed. The present crimper shrink-wrap method, by promoting excellent quality control, better satisfies the client's limitations when compared to conventional crimper compressing box methods. The second curling control is also important when blowing fibers into cushions. The tests indicate that in some synthetic down equipment, a secondary curl of 25 percent causes a scarce opening capacity, since the fibers tend to become entangled, while a secondary curling of 16.5 percent obtains a good performance. Figure 5 illustrates a fiber having primary and secondary crimps. Figure 6 illustrates the fiber of Figure 5 which has been extended to release the secondary crimps, but not the primary crimps. In addition, Figure 7 illustrates the fiber of Figure 6 that has been further extended to release the primary crimps. Schematically, the percentage of total ripple is the ratio of the length of the fiber shown in Figure 5, with the length of the fiber shown in Figure 7. Schematically, the percentage of secondary ripple is the ratio of the difference between the length of the fiber shown in Figure 6 and the length of the fiber shown in Figure 5, with the length of the fiber shown in Figure 7. More specifically, the percentage of secondary ripple can be calculated from the following equation: percentage secondary curly = ((SU - SL¡)? SLf) - 100% where SLi is the not extended length of a skein having primary and secondary curls (see figure 5); where SU is the hypothetical extended length of the same curled skein stretched to release the secondary crimps while maintaining the primary crimps (see Figure 6); and wherein SLf is the actual extended length of the same crimped skein stretched to release the primary and secondary crimps, i.e., the length of the fiber cut (see Figure 7). Thus, in a particular embodiment, the invention is a polyester fiber having a weight ratio: length of about 15 DPF, substantially uniform primary crimps of about 4 CPLI (1.6 CPLCM), and substantially uniform secondary crimps of about 16.5 percent. As will be understood by those skilled in the art, other process variables affect curl control. For example, the force exerted by the fin can be increased to better contain the skein in the crimper compressor box, and thus increase the crimps per unit length. Contrary to this, the force of the fin can be decreased to decrease the curls per unit length. As an illustration, tests using 6 DPF polyester fibers show that a fin strength of approximately 796 N produces 7.2 CPLI (2.8 CPLCM). In contrast, a reduced fin force of approximately 694 N produces 6.0 CPLI (2.4 CPLCM). Similarly, tests using 15 DPF polyester fibers demonstrate that a fin force of approximately 60.5 N produces 5.0 CPLI (2.0 CPLCM), while a fin force of 48.5 N produces approximately 4.0 CPLI (1.6 CPLCM) . In these tests, the force exerted by the fin was varied by changing the air pressure in the cylinder. As will be known to those skilled in the art, curling characteristics affect the properties of the fibers. The experimental results using samples of 3 grams of carded polyester fiber, illustrate the relationship between the frequency of curling and the resistance to compression. For example, a 15 DFP polyester fiber having 3.5 CPLI (1.4 CPLCM), has a compressive strength of 7.78 N. In comparison, the same polyester fiber having 6.0 CPLI (2.4 CPLCM), has a resistance to compression of approximately 9.56 N. Other experiments using 3 gram samples of carded polyester fibers illustrate the relationship between the percentage of secondary crimp and the compressive strength. For example, a 15 DPF polyester fiber having a secondary crimp of 8 percent has a compressive strength of about 7.87 N. In contrast, the same polyester fiber having a secondary crimp of 22 percent has a compressive strength of about 8.10 N. Finally, the tests indicate that the method described herein substantially improves the curling uniformity, and increases the yield of production. For example, processing 8 sub-shafts of a 6 DPF polyester fiber by a standard crimper compressing box results in a Kn value of about 17 percent. Contrary to this, the same crimper compressor box modified by the method described herein, handles 10 subverts and provides crimped fibers having a Kn value of about 13 percent. Similarly, processing 12 sub-shafts of a 15 DPF polyester fiber by a standard crimper compressing box results in a Kn value of about 17.3 percent. By processing the same polyester product by the modified crimper compressor box of the present invention, the yield increases to 14 subverts, and the Kn value is reduced to about 8.3 percent. The modified ripple compressor box of the present invention handles increased performance when modified for optimum ripple uniformity. As noted, the Kn value is a way to quantify the ripple uniformity. As reflected in the production of increased sub-molds, the crimping by the crimper compressing box according to the present invention not only improves the crimping uniformity, but also increases the production rates. In the drawings and specification, typical embodiments of the invention have been described. Specific terms have been used only in the generic and descriptive sense, and not for limiting purposes. The scope of the invention is set forth in the following claims.

Claims (28)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for producing polyester fibers having uniform primary and secondary curls, characterized in that it comprises: advancing polyester fibers in a crimper compressing box having at least one scraper blade, the crimper compressing box defining a compressor box chamber crimper, an inlet of the crimper compressor box, and an output of the crimper compressor box, wherein the ratio between the inlet of the crimper compressor box and the total denier of the polyester fibers, is characterized by a shape of the equation : height of space (mm) * (K ts) t (X), where KDI is, the total of kilodeniers by 2.54 cm of bandwidth of the skein (where K is KDMM, the total of kilodeniers per millimeter of skein bandwidth), where s is the solid fraction of the fibers, and where the ripple variable X has a value between approximately 14.5 KDI / mm (0.57 KDMM / mm) and approximately 18 KDI / mm (0.71) KDMM / mm).

2. The method for producing polyester fibers according to claim 1, further characterized in that the step of advancing polyester fibers in a crimper compressing box comprises advancing polyester fibers in a crimper compressing box having a scraper blade. upper and a lower scraper blade, which together form the entrance of the crimper compressing box.

3. The method for producing polyester fibers according to claim 2, further characterized in that it comprises: applying a longitudinal force against the fibers in advance, to impart uniform primary curls; and continuing to apply the longitudinal force against the primary crimped fibers in advance, to impart substantially uniform secondary crimps.

4. The method for producing polyester fibers according to claim 3, further characterized in that the step of applying a longitudinal force against the advancing fibers comprises restricting the entrance of the crimper compressing box by placing the upper and lower scraper blades, so that the fibers accumulate inside the crimper compressing box, and thus retard the advance of the fibers.

5. The method for producing polyester fibers according to claim 4, further characterized in that the step of placing the upper and lower scraper blades comprises adjusting the upper and lower scraper blades, so that the space formed between the scraper blades top and bottom, open approximately 2 ° to 3 ° towards the outlet of the curling compressor box.

6. The method for producing polyester fibers according to claim 4, further characterized in that the step of applying a longitudinal force against the fibers in advance, further comprises restricting the output of the crimper compressing box with a fin.

7. The method for producing polyester fibers according to claim 6, further characterized in that the step of restricting the output of the crimper compressing box with a fin, comprises restricting the output of the crimper compressing box with a fin that is deflected in the chamber of the curling compressor box less than about 5 degrees from a horizontal plane.

8. The method for producing polyester fibers according to claim 1, further characterized in that the step of advancing the polyester fibers in a crimper compressing box comprises advancing polyester fibers through a grip formed by two rollers. , the entrance of the curling compressor box being defined by a scraper blade and one of the rollers.

9. The method for producing polyester fibers according to claim 1, further characterized in that the step of advancing polyester fibers, comprises advancing a skein of polyester fibers.

10. The method for producing polyester fibers according to claim 1, further characterized in that it comprises the step of forming the fibers into batt.

11. - The method for producing polyester fibers according to claim 1, further characterized in that it comprises the step of forming the fibers in synthetic down.

12. The method for producing polyester fibers according to claim 1, further characterized in that it comprises the step of forming the fibers into yarn.

13. The method for producing polyester fibers according to claim 1, further characterized in that it comprises the step of forming the fibers in carpet.

14. The method for producing polyester fibers according to any of claims 1 to 13, further characterized in that the variable s has a value of 1.

15. The method for producing polyester fibers according to any of the claims 1 to 13, further characterized in that the variable s has a value less than 1.

16. The method for producing polyester fibers according to any of claims 1 to 13, further characterized in that the variable s has a value between about 0.72. and approximately 0.91.

17. The method for producing polyester fibers according to any of claims 1 to 13, further characterized in that the ripple variable X has a value of approximately 16.3 KDI / m (0.64 KDMM).

18. - A polyester fiber, characterized in that it comprises: substantially uniform primary curls; and substantially uniform secondary curls.

19. The polyester fiber according to claim 18, further characterized in that the weight: length ratio of said polyester fiber is less than about 500 deniers.

20. The polyester fiber according to claim 19, further characterized in that the weight: length ratio of said polyester fiber is less than about 50 deniers.

21. The polyester fiber according to claim 20, further characterized in that the weight: length ratio of said polyester fiber is less than about 15 deniers.

22. The polyester fiber according to claim 18, further characterized in that substantially uniform primary ripples have a ripple frequency between about 0.6 crimps per linear centimeter, and about 6 crimps per linear centimeter.

23. The polyester fiber according to claim 22, further characterized in that the substantially uniform primary ripples have a ripple frequency between about 0.6 ripples per linear centimeter, and about 1.6 ripples per linear centimeter.

24. The polyester fiber according to claim 22, further characterized in that the substantially uniform primary ripples have a ripple frequency between about 1.6 crimps per linear centimeter, and about 4.7 crimps per linear centimeter.

25. The polyester fiber according to claim 22, further characterized in that the substantially uniform primary ripples have a ripple frequency between about 4.7 ripples per linear centimeter, and about 6 ripples per linear centimeter. 26.- A skein of polyester fibers, characterized in that it comprises: a plurality of polyester fibers, wherein said polyester fibers have primary substantially uniform curls and secondary curls substantially uniform; and a total of deniers of at least approximately 500,000. 27. The polyester skein according to claim 26, further characterized in that said polyester fibers have a total denier of less than about 4,000,000. 28.- The skein of polyester in accordance with the claim 26, further characterized in that said polyester fibers have a weight: length ratio, less than about 15 denier per fiber.