IMPROVEMENTS IN POLYESTER FIBERFILL

Abstract: Polyester fiberfill having spiral crimp that is randomly-arranged and entangled in the form of fiberballs with binder fibers, preferably with a minimum of hairs extending from the surface of the fiberballs, so as to be air-transportable on account of the low cohesion between the balls. A process for making such fiberballs by repeatedly air-tumbling small tufts of such fiberfill/binder/blend against the wall of a vessel. Improved bonded batts or molded articles or other bonded articles obtained by bonding such fiberballs.

Description: TECHNICAL FIELD This invention concerns improvements in and relating to polyester fiberfilling material, commonly referred to as polyester fiberfil, and more particularly to providing polyester fiberfill in the form of fiberballs containing binder fibers, that may be bonded to provide useful new through-bonded products, and to processes for preparing these new products. BACKGROUND OF INVENTION Thermally-bonded (polyester) fiberfill batts (or battings) are well known and have gained large scale commercial use, particularly in Europe. Binder fibers can be blended intimately into the fiberfill to achieve true "through-bonding" of fiberfill batts, and thus achieve better durability versus resin-bonding, which was the conventional method, and can also provide reduced flammability versus resin-bonding. Such binder fiber blends are used on a large scale in furnishings, mattresses and similar end-uses where strong support is desired. However, they are seldom used as the only filling material in these end-uses, particularly in furnishing seat cushions, where the common practice is to use the fiberfill batts as a "rapping" for a foam core. It is believed that the main reason is probably that, to obtain the desired resilience and performance in 100% fiberfill cushions, it would be necessary to provide such relatively high density as has hitherto been considered too costly and difficult with the present techniques, and as might not provide desirable performance aesthetically. In a conventional fiberfill batt, the fibers are arranged in parallel layers which are bonded together. In such a layered structure, any pressure applied during use as a cushion is essentially perpendicular to the direction of the fibers and I believe that may be at least partly why such a high density must be reached to achieve the desired resilience and durability using conventional layering and bonding techniques. US-A-4 065 599 discloses spherical objects useful as a filler material of diameter from 5 to 50 mm, and with a surface shell composed of arcuately arranged polyester filaments of at least 0.2 m in length, being concentrated near the surface of the spherical object, and being arranged along different arcuate paths which are angularly related to each other such that different filaments intersect with one another at different points and are adhesively fixed to each other at the points of intersection. The fixing adhesive may have a melting point at least 30°C. below that of the polyester filament, and may be filamentary, e.g. conjugated filaments having a relatively low melting component. SUMMARY OF THE INVENTION According to the invention, there are provided new fiberfill structures that may be bonded to provide products of improved performance, especially with regard to resilience and durability, over what has been available commercially hitherto, as will be explained hereinafter. According to one aspect of the invention, there are provided fiberballs of average dimension about 2 to about 15 mm, consisting essentially of randomly-arranged, entangled, helically-crimped polyester fiberfill having a cut length of about 10 to about 100 mm, intimately blended with binder fibers comprising a fiber material having a melting point which is at least 20°C. lower than that of the polyester, in an amount about 5 to about 50% by weight of the blend. Alternatively, there are provided fiberballs of average dimension about 2 to 15 mm, consisting essentially of randomly-arranged, entangled, helically-crimped bicomponent polyester/binder material fibers, having a cut length of about 10 to about 100 mm. According to another aspect of the invention, there is provided a process for making polyester fiberballs from an intimate blend of helically-crimped polyester fiberfill and of binder fibers, wherein small tufts of the blend are repeatedly tumbled by air against the wall of a vessel to provide the fiberballs. Alternatively, there is provided a process for making polyester fiberballs from helically-crimped bicomponent polyester/binder material fibers, wherein small tufts of the helically-crimped fibers are repeatedly tumbled by air against the wall of a vessel to provide the fiberballs. According to further aspects of the invention, there are provided entirely new resilient shaped articles, or structures consisting essentially of thermally-bonded, helically-crimped polyester fiberfill, and processes for making these bonded products from the fiberballs of the invention. These aspects will be dealt with in greater detail below. As will be seen, the fiberballs of the invention open entirely new possibilities and the use of alternative techniques for preparing bonded articles from polyester fiberfill, which, hitherto, has been limited, effectively, in commercial practice, to the use of carded webs and batts, and bonding and shaping in the form of a batt, with all the constraints that this has imposed in practice. BRIEF DESCRIPTION OF DRAWINGS Figures 1 and 2 are enlarged photographs of fiberballs according to US-A-4 618 531. Figures 3 and 4 are schematic drawings in section of the machine used to make the fiberballs in the Examples herein. The main body is a horizontal stationary cylindrical drum 1 within which is a rotating axial shaft 2 that is driven by a motor 3 and equipped with radial stirrer blades 4 that do not extend to the wall of the drum. The contents of the drum are recirculated by being withdrawn through outlets 16 and 18 at either end, along pipes 10 and being blown back into the drum through inlet 12 by blower 9. Before introducing the fiberfill starting material, the motor is started to drive the shaft and stirrer blades at a relatively low speed. Then blower 9 is started up to withdraw fiberfill from the supply source. When the drum has been charged with sufficient fiberfill, the feed of fiberfill is closed, and the fiberfill continues to recirculate. Progress can be viewed through glass sight windows conveniently located in the wall and end faces 15 and 17 of the drum. DETAILED DESCRIPTION OF THE INVENTION Some idea of the nature of the fiberballs of the invention, and especially of the nature of the configurations taken up by the spirally-crimped fiberfill therein, can be gained from Figures 1 and 2 of the accompanying drawings. For convenience, at this point, reference is made to US-A-4 618 531 (EP-A-203 469), directed to refluffable fiberballs of spirally-crimped polyester fiberfill, and to a process for making such fiberballs, the disclosure being incorporated herein by reference. The objective of this patent was to provide a synthetic product as a real alternative to down, in the sense of having refluffable characteristics (available from down) and also with washability (unlike down) and at a lower cost than down. As indicated, this objective was obtained by providing refluffable fiberballs from spirally-crimped polyester fiberfill. An essential element was the use of such spirally-crimped fiberfill. Such refluffable fiberballs can be obtained by air-tumbling small tufts of fiberfill (having spiral crimp) repeatedly against the wall of a vessel as illustrated in Figures 3 and 4 herein. The objective of the present invention is entirely different from the objective of EP-A-203 469, as indicated above. Moreover, the fiberballs of the present invention are distinguished from the refluffable fiberballs specifically disclosed in EP-A-203 469 by the content of binder fibers, to achieve the bonding and the new bonded products that are the objective of the present invention. Nevertheless, the techniques used for making fiberballs are similar, and essentially the same apparatus may be used in both instances, and Figures 1 and 2 may be helpful in visualizing the fiberballs of the invention, and the spirally-crimped fiberfill therein. As indicated, an essential element of the present invention is the use of fibers having significant curliness, such as is referred to herein as spirally-crimped fiberfill. Such fibers have a "memory" that provides them with a natural tendency to curl, i.e. to take up helical or spiral configurations. The provision of such spiral crimp is itself well-known for other purposes. This can be provided economically by asymmetric-jet-quenching of freshly-extruded polyester filaments, as taught, e.g. in Kilian US-A-3,050,821 or 3,118,012, especially for filaments of drawn denier in the range about 1 to 10. The spiral crimp is believed to result from differences in crystalline structure across the cross-section of the fibers, which provide differential shrinkage, so the fibers curl helically upon appropriate heat-treatment. Such curls need not be regular, and in fact are often quite irregular, but are generally in 3 dimensions and so are referred to as spiral crimp or helical crimp to distinguish from the essentially 2-dimensional saw-tooth crimp induced by mechanical means, such as a stuffer box, which is the preferred method used commercially for crimping polyester tow precursors to staple fiber at this time. Asymmetric-jet quenching is the technique that was used to make the fiberballs in Examples 1-5 herein. An alternative way to provide spiral-crimp is to make bicomponent filaments, sometimes referred to as conjugate filaments, whereby the components have different shrinkages upon being heat-treated, and so become spirally-crimped. Bicomponents are generally more expensive, but may be preferred for some end-uses, especially if it is desired to use fiberfill of relatively high denier, such as is more difficult to spiral-crimp adequately by an asymmetric-jet-quenching technique. Bicomponent polyester filaments are taught, e.g., in Evans et al. US-A-3,671,379. Particularly good results have been achieved by using a bicomponent polyester fiberfill sold by Unitika Ltd. as H38X, referred to in Example IIIB of copending application EP A1 0 203 469. Of course, especially with bicomponent filaments, there is no need to use only polyester components. A suitable polyamide/polyester bicomponent filament can be selected to give a good spiral-crimp. Still further methods of obtaining fiberfill with a "memory" and ability to crimp spirally are disclosed in Nippon Ester Japanese Patent Application Kokai No. 57-56512, published April 5, 1982, and in Toyo Boseki GB-A- 1,137,028, which indicate that hollow fiberfill can be obtained with this property. Apart from the spiral-crimp, which is essential, the fiberfill staple fibers may be solid or hollow, of round cross-section or non-round, and otherwise as disclosed in the prior art, according to the aesthetics desired and according to what materials are available. The spiral-crimp must be developed in the fiberfill so that making the fiberballs becomes possible. Thus a tow of asymmetrically-jet-quenched polyester filaments is prepared by melt spinning and gathering the spun filaments together. The tow is then drawn, optionally coated with a surface modifier, optionally relaxed before cutting conventionally to form staple fibers, and preferably relaxed after cutting to enhance the asymmetric character of the fibers. This character is required so the fibers will curl and form the desired fiberballs with minimal hairiness. Conventional mechanical crimping, such as by a stuffer-box technique, is not generally desired because inappropriate heat-treatment can destroy the desired spiral-crimp, and to such mechanically-crimped fiberfill would not form fiberballs, as desired. Such mechanical crimping is not an alternative to spiral-crimp, because mechanical crimping gives a saw-tooth crimp which will not form the desired fiberballs. However, we have found that fiberballs can be obtained if some suitable degree of mechanical crimp with appropriate heat treatment is provided to the precursor filamentary tow, in which case the eventual fiberfill will have a configuration that is a result of combining this mechanical crimp and spiral crimp. This is the technique used in Examples 6-10 herein. We refer to this crimp as Ω-crimp (omega-crimp) because the configuration of the fibers resembles the shape of this Greek letter Ω, being a combination of a saw-tooth from the mechanical crimping superimposed on the curl of the spiral crimp obtained because of the "memory" referred to above. This Ω-crimp may be obtained in other ways. An essential element of the fiberballs of the present invention is the binder fibers, which are preferably used in amount about 5 to about 50% by weight of the blend, the precise amount depending on the specific constituents and the desired end-use, but about 10 to about 30% generally being preferred. As indicated above, binder fibers are well known and have been used commercially for obtaining thermally-bonded batts of polyester fiberfill. Such conventional binder fibers, e.g. of lower melting polyester, may be used according to the present invention as such, or modified appropriately. Several options are, however, available, as will be clear hereinafter. The general requirements for binder fibers are conveniently set out in Pamm US-A-4,281,042 and Frankosky US-A-4,304,817, the disclosures of which are hereby incorporated by reference. As indicated therein, and discussed hereinafter, depending on the intended end use, it may be preferred to provide blends of binder fiber with surface-modified (slickened) fiberfill (to provide aesthetics that may be desired in the thermally-bonded product), including triple blends also with unslickened fiberfill (if desired to provide bonding sites, when the slickened fiberfill is not so amenable for this purpose) as well as the binder fibers themselves. An important requirement of the binder material is that it have a bonding temperature lower than the softening temperature of the polyester fiberfill. Thus the binder should be of appropriately lower melting point than the polyester fiber, e.g. some 20°C or 30°C, or preferably 50°C lower, depending on the sensitivity of the materials to heat and the efficiency of the bonding equipment and conditions, so that thermal bonding of the blend may take place conveniently without deleteriously affecting the physical properties of the polyester fiberfill itself, or be otherwise capable of being sensitized so as to provide its essential function of bonding the polyester fiberfill. It will be understood that, if the binder fibers are monocomponent fibers in the blend, they may lose their fiber form during the bonding operation, and thereafter the binder may exist merely as globs binding the intersections of the polyester fiberfill. If, however, the binder fibers are bicomponent fibers, e.g. if preferred sheath-core fibers are used, and only the sheath comprising e.g. about 5 to about 50% of the bicomponent is a binder material whereas the core is a higher melting component that can remain in fiber form after the bonding operation, then the final bonded product will comprise these remaining core elements from the original binder fibers in addition to the polyester fiberfill. Indeed, it may be possible and desirable to provide a multicomponent binder fiber that is also spirally crimped and so can by itself perform all the requirements of the present invention. In other words, there would be no need for a blend of separate binder fibers and spirally-crimped fibers, but the fiberballs of the invention would consist essentially of spirally-crimped, multicomponent, binder fibers that are first formed into the fiberballs, and then at a later stage treated so to activate the binder material component, thereby leaving a bonded assembly or shaped article of bonded fiberfill. The binder fibers are preferably of similar dimensions and processing characteristics to the polyester fiberfill, to permit easy intimate blending, although this is not essential, and may not even be desirable depending on the intended final use and the components. For instance, if the binder fiber is a bicomponent, used in relatively large quantities, it may be desirable that the final bonded product comprise bonded fibers of essentially similar dimensions and characteristics. As indicated, it may be advantageous to provide the binder fiber in spirally-crimped form. This will be particularly desirable if the binder fiber comprises a significant or large proportion of any blend, so as to facilitate the formation of the fiberballs, although it is possible for spirally-crimped fiberfill to form satisfactory fiberballs even in the presence of other fibers that are not spirally-crimped, and so dilute the effect of the spirally-crimped components. Bearing the above in mind, the selection of the various characteristics, amounts and dimensions of the fiber constituents will depend generally on the intended end use, and the aesthetics of the bonded article, and such considerations as cost and availability. Generally, the dtex will be between 1 and 30, preferably at least 3 dtex, and preferably less than 20 dtex, and often approximately 5 dtex or up to 10 dtex, and the cut length is generally about 10 to about 100 mm, preferably at least 20 mm and preferably up to 60 mm. As indicated, it may be desirable to slicken (lubricate the surface) at least some of the fibers, and to use a conventional slickening agent for this purpose. This may be desirable for several reasons, e.g. for aesthetics in the final bonded product, and to improve durability, and also to reduce the cohesion of the fiberballs, and to permit them to be transported, e.g. by blowing. If a conventional silicone slickener is used, however, this will reduce the ability of the fiberfill to bond, and increase the flammability, as disclosed already and in EP-A-0 265 221, and so, preferably, the fiberfill will be coated with a hydrophilic slickener consisting essentially of chains of poly(alkylene oxide) as disclosed therein. Several such materials are disclosed in the literature. Preferred materials are "curable" to the polyester fiberfill. For instance, a segmented copolymer of poly(ethylene terephthalate) and poly(ethylene oxide). Some such materials are available commercially, such as the textile finishing agent sold under the trademark "ATLAS" G-7264 ® by ICI Specialty Chemicals, Brussels, but it may be preferred to use materials with less fiber to metal friction, as well as a low fiber to fiber friction. Another material is sold as "ZELCON" 4780 ® , by E. I. du Pont de Nemours and Company. Other materials are disclosed in Raynolds US-A-3,981,807. Several segmented copolyesters consisting essentially of poly(ethylene terephthalate) segments and of poly(alkylene oxide) segments, derived from a poly(oxyalkylene) having a molecular weight of 300 to 6,000 and dispersions thereof are disclosed in McIntyre et al. US-A-3,416,952, 3,557,039 and 3,619,269, and in various other patent specifications disclosing like segmented copolymers containing poly(ethylene terephthalate) segments and poly(alkylene oxide) segments. Generally the poly(alkylene oxide) will be a poly(ethylene oxide), which is a matter of commercial convenience. Other suitable materials include modified poly(ethylene oxide)/poly(propylene oxide) grafted with functional groups to permit crosslinking, e.g. by treatment with citric acid, such as are available commercially from Union Carbide as "UCON" 3207A. ® Other materials that may include particularly useful compositions are disclosed in Teijin EP 159 882 and in ICI Americas EP 66944. Choice of a particular slickener will depend on the desired end-use, and many of the indicated slickeners differ in their ability to lubricate, e.g. to lower fiber-to-fiber and/or fiber-to-metal frictions and amounts of anion groups. If, for example, moisture transport and durability are desired, but softness is not so important, item 12 in EP 66944 may be desirable. Depending on the aesthetics desired, the amount of slickener may be adjusted, between about 0.05 and about 1%, preferably about 0.15 to about 0.5%, on the weight of the fiberfill, being generally desirable, depending on, e.g., the type of slickener and the effect desired. Polyester fiberfill, like other staple fiber, has been generally transported in compressed bales, which are conventionally first treated in an opener, so as to separate the individual fibers to some extent before they are further processed, e.g. on a card if a parallelized web is desired. For making products of the invention, it is not necessary, and is generally undesirable, to completely parallelize the fibers, but it is desirable first to open and separate the fibers into discrete tufts before treatment to form the fiberballs, as will be described. The fiberballs are formed by air-tumbling small tufts of fiberfill (having spiral crimp) repeatedly against the wall of a vessel so as to densify the bodies and make them rounder. The longer the treatment, generally the denser the resulting balls. It is believed that the repeated impacts of the bodies cause the individual fibers to entangle more and lock together because of the curl of the spiral crimp. In order to provide an easily-transportable product, however, it is also preferred to reduce the hairiness of the balls, because the spiral-crimp of any protruding fibers will raise the cohesion between neighboring fiberballs. This cohesion can also be reduced somewhat, however, by thorough distribution of a slickener, as described herein, to increase lubricity between the fiberballs. The slickener also affects the aesthetics. Depending on the aesthetics desired, the amount of tumbling and application of slickener may be adjusted. The fiberballs of the present invention comprise fibers that are randomly-arranged, as shown in Figures 1 and 2, showing desirable light fluffy balls with low cohesion, because of the use of spirally-crimped fiberfill. In contrast, a mass consisting only of regular polyester fiberfill, i.e. mechanically crimped polyester fiberfill without any spirally-crimped material, cannot be formed into balls by the process of the invention. Such regular fiberfill, like other fibers, such as wool, can be forced into dense assemblies, including balls, by using very high shearing forces. These dense assemblies are entirely different from the fluffy blowable fiberballs of the present invention, being harder, denser and hairy and are not desirable for the purposes of the present invention. The air-tumbling has been satisfactorily performed in a modified machine, based on a Lorch machine as described in U.S. Patent US-A-No. 4,618,531 (EP-A-203 469), and as illustrated in Figures 3 and 4 herein. This machine was used in the Example herein. The resulting fiberballs are easily transported, for instance, by blowing, especially if the hairiness is reduced by increasing lubricity, as described herein and in US-A-4,618,531 (EP-A-203 469). These fiberballs may then be compressed and bonded together to form bonded structures that may superficially resemble bonded batts or molded into any desirable shape. For instance, the fiberballs may be blown into a light ticking, or a non-woven, and then heated to produce a cushion-like article in the shape of the ticking. As a result, the final product has improved resilience and performance, as indicated hereinafter, and is very different from prior art bonded batts. It is believed that the improvement results from the fact that the fibers have a significant component in every direction, as contrasted with the primarily parallelized fibers of prior art layered batts. The difference in performance is surprising and significant, as can be shown by examining the different structures when they are supporting a weight. The bonded products of the invention act like many independent springs that support the weight above them, whereas the parallelized fibrous structures of the prior art will pull inwards from the sides, for reasons that can be rationalized in retrospect. Another advantage is the faster moisture transport, which is believed to result from porosity between the fiberballs, which is of particular potential interest for structures such as cushions and matresses wherein the principal or only stuffing material is such fiberballs. The moisture transport characteristics can be further enhanced by the use of a permanent hydrophilic finish, as indicated. Thus, the major expected end users for the final stuctures are for furnishing cushions, car seats, matresses and like products. Such structures may, if desired, be molded initially into the form finally desired by heating to activate the binder fiber in the fiberballs within a ticking within a mold of the desired shape. Or the bonded structure may be formed in long lengths like prior art bonded batts, or in other standard shapes, and then be cut and, if necessary, be reshaped as desired. Greater flexibility in this regard is available than with prior art bonded batts. Moreover, it may prove feasible to use the fiberballs of the invention in a manner completely different from that commercially used heretofore with prior fiberfill products, namely by bonding the fiberballs individually in a fluidized bed, and then blowing the individual balls into a ticking. The resulting new product is refluffable, and so entirely different from prior art bonded fiberfill products, but more like cushions filled with feathers and chopped foam. Such new product has, in addition to good resilience and durability, the novel characteristic that the individual balls can move in the ticking in a similar manner to down and feather blends. In such products, it is again desirable to reduce cohesion by application of appropriate lubricants or slickeners for this purpose (and for promoting moisture transport, as disclosed in US-A-4618531 (EP-A-203469). This reduction of hairiness/cohesion improves the transportability of the fiberballs, e.g. by blowing, and improves the softness of the product in end uses where this is desirable, and also offers an improved degree of moisture transport that is believed unattainable with prior products. In such products, the dimensions of the fiberballs are believed important for aesthetic reasons, as described in US-A-4,618,531, average dimensions of about 2 to about 15 mm being preferred. DESCRIPTION OF TEST METHODS Bulk measurements were made conventionally on an Instron machine to measure the compression forces and the height of each sample cushion, which was compressed with the appropriate foot of diameter 10 cm attached to the Instron. From the Instron plot are noted (in cm) the Second Initial Height (IH2) of the test material, i.e. the height at the beginning of the second compression cycle, the Support Bulk (SB 60N), i.e. the height under a compression of 60N, and the Bulk (height) under a compression of 7.5N, (B 7.5N). The softness is calculated both in absolute terms (AS, i.e. IH2-B 7.5N) and in relative terms (RS - as a percentage of IH2). The firmness of a cushion correlates with strong support, i.e. the Support Bulk, and inversely with softness. Resilience is measured as Work Recovery (WR), i.e. the ratio of the area under the whole recovery curve calculated as a percentage of that under the whole compression curve. The higher the WR, the better the resilience. Durability - Each sample cushion was covered with a fabric having an air permeability of about 100 1/sq.m./sec and its compression curve was measured and recorded as BF (before flexing). The firmer cushions, whose test results are shown in Tables 2-5, were then submitted to 10,000 successive flexings under a pressure of 13 kPa (about 133 g/sq.cm.) at a rate of 1400 cycles/hour and the compression curve measured again and recorded as AF (after flexing) so as to show any changes in bulk and resilience resulting from the flex test, as percentages (Δ). The pillows of Examples 15 et seq. Were flexed differently, as described later, in relation to Table 6. The invention is further described in the following Examples. All parts and percentages herein are by weight, and with respect to the total weight of fiber, unless otherwise stated. Example 1 A tow of asymmetrically-jet-quenched drawn poly(ethylene terephthalate) filaments of 4.7 dtex was prepared conventionally without mechanical crimping, using a draw ratio of 2.8X. The tow was cut to 36 mm cut length and relaxed at a temperature of 175°C to develop the spiral crimp. The staple was blended in the ratio of 80/20 with a sheath/core binder fiber, cut to the same cut length, and having a 4.4 dtex. The blend was opened on a commercial opener and the resulting opened blend was processed for 6 seconds on a Trutzschler cotton beater to separate the fibers into discrete small tufts. A batch of the resulting products was blown into the modified Lorch machine, as described and illustrated, and processed for 1 minute at 250 rpm, then for 3 minutes at 400 rpm to convert the tufts into consolidated fiberballs. The fiberballs were packed to different extents, to provide a series of different densities from 20 Kg/m³ ( A) to 50 Kg/m³ (E), as indicated hereinafter, into a box (mold) made of wire mesh reinforced with 2 mm thick stainless steel bars with a rectangular base of 40 x 33 cm and where the height can be varied between 1 and 25 cm. Each sample of fiberballs was compressed to a similar height of about 9 cm, while varying the resulting density by changing the quantity of fiber balls packed into the box. The mold was then placed in an oven with an air flow across the rectangular base at a temperature of 160°C for 15 minutes. After cooling the mold, the resulting "cushion" was released and the compression characteristics were determined, and are recorded in the top part of Table 1 as Items A-E. This indicates that the support obtainable from products of the invention can be varied over a wide range, by varying the density, and that excellent resilience (WR) is also obtained, especially at higher densities. The durability is also excellent; (this is measured and discussed hereinafter in relation to higher density (firmer) products, with reference to Table 2). For comparison, similar compression measurements were made and are recorded in the lower part of Table 1 for 5 conventional materials bonded under exactly the same procedure as in Example 1. The compositions of these "Comparisons" was as follows: 1. A triple 60/20/20 blend, compressed to about 20 Kg/m³ (for comparison with Item A of the invention), using the same binder fiber (of dtex 4.4) in the same amount 20%, but containing 80% of commercial poly(ethylene terephthalate) fiberfill of three times higher denier (13 dtex), which would normally give much better resilience and more firmness (support bulk) than products from lower denier fibers), one quarter of which was slickened with a commercial silicone slickener (20%), while the remaining three quarters (60%) was "dry", i.e. unslickened. 2. An 85/15 blend, compressed to about 25 Kg/m³ (for comparison with Item B of the invention), of the same binder fiber (15%) of denier 4.4 dtex, but containing 85% of dry hollow commercial fiberfill of 6.1 dtex (significantly higher than the 4.7 dtex fiberfill used in Item B). Despite the lower dtex in the cushions of the invention, Items A and especially B showed equal or better resilience (higher WR) and better support bulk (lower RS) than the comparisons 1 and 2 of similar density. Furthermore, the products of the invention have excellent durability, whereas the comparisons are much inferior especially in this respect. For higher densities, similar comparison blends would fare even worse, so I tested the following representative products used in furnishing seat cushions or mattress cores; (the characteristics of polyurethanes can be varied by changing the ingredients to increase the softness or firmness, so these qualities are not controlled merely by the density):- 3. Commercial polyurethane "soft" foam core at 35 kg/m³. 4. Commercial polyurethane "firm" foam core at 30 kg/m³. 5. Commercial latex core (10 cm height) at 72 Kg/m³. The results in Table 1 indicate that products C and D of the invention are comparable in resilience to the foam cushions 3 and 4, which are firmer, and product E of the invention is somewhat more resilient than the latex. This is a significant achievement and could open the way for fiberfill to be used as the only filling material in certain end uses where previously foam cores have been used. The durability of sample cushion E (at 50 kg/m³) is recorded as Example 1, in Table 2, and is compared with cushions of similar density made as described in Examples 2-10. Example 2 The procedure of Example 1 was followed, except that the fiberballs were mixed with 10% of the same binder fiber before being molded at 50 Kg/m³ to give a product of somewhat higher resilience and lower bulk losses, i.e. somewhat better durability. Example 3 The procedure of Example 1 was followed, except that the fiberballs were treated with 0. 35% of 3207A UCON ® and dried at 50°C before being molded. This product shows lower initial resilience but less loss of bulk or resilience after the durability test. Example 4 The procedure of Example 3 was followed, except that 0.35% of G-7264 was used instead of 3207A UCON. ® This product shows equal bulk and lower resilience than Example 1. Example 5 The fiberballs of Example 4 were mixed with 10% of the same binder fiber in random force (not in balls) as in Example 2 before molding. This product shows the best combination of durability of resilience with good bulk. Summarizing the durability results of Examples 1 to 5, Example 1 shows "dry" fiberballs molded alone, whereas Examples 3 and 4 show fiberballs slickened with non-silicone PEO-type slickeners molded alone, Example 2 shows dry fiberballs mixed with random binder fiber before molding, while Example 5 shows a combination of this feature and of the more effective slickener of Example 4. As shown in Table 2, the slickened items of Examples 3 and 4 performed remarkably well, showing that good bonding occurred, and held up well throughout the flexing treatment, despite the coating with these particular slickeners (whereas silicone-slickened fibers do not bond). Indeed their durability was better at equal support bulk than dry Example 1, but the resilience was lower. The best results were in Example 5, where the resilience was almost the same initially, but better after the durability test, and the support bulk showed better durability. Examples 6-10 These Examples correspond to Examples 1-5, respectively, except that the tow of 4.7 dtex was mechanically crimped (to provide a mild mechanical crimp in addition to the spiral crimp) by passing through a stuffer box, under mild gate and roll pressures. The resulting fiberfill has Ω-crimp. The fiberballs of Examples 6-10 have 10-20% higher bulk than the fiberballs of Examples 1-5, whereas the molded products are not very different, but have lower resilience and lower Support Bulk (SB 60N). Examples 11 and 13 show the preparation of fiberballs with a preferred (non-silicone, hydrophilic) slickener being applied before the polyester filaments are relaxed, so as to "cure" the slickener onto the filaments during the relaxing treatment. The durability data of the resulting cushions are compared in Table 3, with comparable products from the fiberfill of Example 1, while Tables 4 and 5 provide comparable data obtained from foam and latex products (4) and from other molded fiber structures (5) that are not according to the invention. Example 11 A tow of asymmetrically-jet-quenched drawn poly(ethylene terephthalate) filaments of 4.7 dtex was prepared conventionally without mechanical crimping, using a draw ratio of 2.8X. The segmented copolymer sold as "ATLAS" G-7264, ® at a concentration of 0.35%, was applied to the fibers and dried at 130°C. The tow was subsequently cut to 35 mm and relaxed at 175°C. The staple was blended in the ratio of 80/20 with a sheath/core binder fiber, cut to the same cut length, and having 4.4 dtex. The blend was opened on a commercial opener and the resulting opened fiber was processed into fiberballs essentially as described in Example 1. The fiberballs were molded essentially as described in Example 1 into a cushion of 40X33X9 cm with a density of 50 Kg/m³. The cushion was submitted to the durability test described previously and the results show the improvement in durability versus Example 1, mainly with respect to the Work Recovery (resilience). The resilience losses of the product made according to Example 11 are about half of the best Example in Table 2 with comparable bulk losses. Example 12 This cushion was made with the staple of Example 1 for comparison with Example 11. Example 13 This was essentially like Example 11, except that the staple/binder ratio was 90/10. This cushion shows excellent durability, but the resilience is much lower. This product has potential in back cushions or in styles requiring softer cushions. Example 14 This cushion was made with the staple of Example 1 blended with the same binder at a ratio of 90/10, to compare with Example 13. The durability test shows somewhat higher bulk losses than Example 12 (using a ratio of 80/20). Table 3 confirms that the resilience of the molded structures made from the "dry" blends is higher than for the corresponding "slickened" blends (of Examples 11 versus 12, and 13 versus 14). On the other hand, the molded structures made from the fiberballs containing the "dry" blend have higher losses of resilience. Comparison Products Table 4 shows the durability data for the following representative foam and latex samples supplied by mattress and furnishing manufacturers tested under the same conditions as the products of the invention. Small differences between the initial values of these products (as reported in Table 4) and the measurements reported previously (Table 1) are a result of sample to sample differences or from the size of the sample. The results in Table 4 are the measurements made on the piece actually tested cut to the same size as the molded cushions:- Re 1: polyurethane foam of 30 Kg/m³ Re 2: polyurethane foam of 35 Kg/m³ "soft" Re 3: polyurethane foam of 35 Kg/m³ Re 4: polyurethane foam of 40 Kg/m³ Re 5: latex matress core 72 Kg/m³ Table 5 shows the comparable durability data for cushions of the same size from molded fiber structures that were not made from fiberballs, but always used the same binder fiber. Ct 1: 85/15 blend, using 6 dtex hollow dry staple, carded, molded to a density of 50 Kg/m³. Ct 2: Same blend, opened and random-filled into mold, same density. Ct 3: Same blend, random-filled, but density of 40 Kg/m³. Ct 4: Same as Ct 1, but the 6 dtex hollow fiber had been coated with 0.35% of the segmented copolymer of poly(ethylene terephthalate) and poly(ethylene oxide) as in Example 11. Ct 5: Same blend as Ct 4, but opened and random-filled like Ct 2. Ct 6: Same as Ct 5, but density only 40 Kg/m³. The data contained in Tables 3, 4 and 5 can be analyzed as follows: Fiber assemblies made of blends of fiberfill/binder in the appropriate ratios, can produce molded cushions or similar products with a durability which is better than foam and comparable to latex, at a comparable support bulk, by using fiberballs according to the invention. The cushion, or mattress core, made from the fiberballs of the invention has an important advantage over foam and latex in having a higher air permeability than most foam and latex, and a better moisture transport, due to the hydrophilic character of the "slickener" and to the fiberball structure. The fiberball-molded cushions of the invention have 12-22% higher support bulk, but comparable to better durability at the same density, as compared with molded cushions made from condensed batts. Furthermore, a cushion molded from a carded batt does not adapt itself well to the human body. When a pressure is applied to its center, it pulls the sides, causing them to raise up. The cushion made from the fiberballs of the invention adapts itself to the deformation caused by the user, like a system composed of independent springs. These properties make the products of the invention a much better product for furnishing cushions, mattress cores, and similar products. Products made from fiber blends such as the one used in Ct 4 have their own merits, particularly at lower densities and are the subject of EP-A-265 221. Individually-Bonded Fiberballs, e.g. for Pillows In Examples 15-17, the fiberballs were not molded together to form an integral block, but were bonded individually, so that they can be used as a highly-performing filling in refluffable cushions and pillows. Bonding of the individual fiberballs can for instance be done in a fluidized bed. In Examples 15 and 16, the fiberballs of the invention were individually bonded, and then blown into a pillow ticking. In Example 17, for comparison, the fiberballs were not heated, i.e. were blown into the ticking without first effecting bonding of the binder fibers. In Ct. 18, a commercially available bedding product (without binder fiber), the subject of US-A-4,618,631, was blown into the ticking to provide a further comparison. In each case, 1000g of the fiberballs were filled into a ticking of dimensions 80 cm x 80 cm, and the compression measurements were made before and after flexing. Unlike the flexing used hereinbefore, however, the durability was tested using a Fatigue Tester as described in columns 9-10 of US-A-4,618,631, except that the severity of the flexing was increased to the extent that bulk losses after 6,000 cycles (in the present tests) correspond approximately to the bulk losses that had been obtained after the full 10,000 cycles (as reported in US-A-4,618,631) and the flexing was continued (in the present tests) for a total of 10,000 cycles; so, it will be appreciated that the results reported in Table 6 reflect these more severe flexing conditions than were used in US-A-4,618,631. Example 15 The fiberballs of the invention were produced as described in Example 1. The individual fiberballs were then thinly-distributed between two sheets of a very open woven cotton fabric and heated in an oven at 160°C. The fiberballs were thus essentially individually bonded (any balls that were bonded together were separated by hand). 1,000g were then filled into the 80x80 cm pillow ticking by blowing. Example 16 The fiberballs described in Example 15 were sprayed with 0.35% of the segmented copolymer sold as "ATLAS" G-7264, ® dried at room temperature, and heated at 160°C under the same conditions as in Example 15. The results in Table 6 show better retention of initial height than for the product of Example 15. Example 17 The fiberballs were produced from the same blend as in Example 15, but were not heated so the unbonded product was filled into pillow ticking and tested as a control for Example 15, to show the improvement achieved by bonding on the durability of the fiberballs. The data in Table 6 show:- The dry fiberballs (Example 17) have a poorer durability than the slickened commercial product (Ct 18), particularly at the support bulk level (60N). "Dry" bonded fiberballs (Example 15) show improved durability versus the slickened nonbonded commercial product (Ct 18), are much firmer and do not have the characteristics of a bedding product. The fiberballs which were slickened and bonded (Example 16) show the best durability. The two bonded samples (Examples 15 and 16) have much higher bulk than the nonbonded samples after the durability test, which will translate into better-looking, more comfortable and altogether more desirable furnishing cushions.

Claims: Fiberballs of average dimension of about 2 to about 15 mm containing essentially entangled polyester fiberfill, intimately blended with binder fibers comprising a fiber material having a melting point which is at least 20°C lower than that of the polyester, characterized in that the polyester fibers are randomly arranged, helically crimped and have a cut length of about 10 to about 100 mm and the binder fibers are present in an amount of about 5 to about 50% by weight of the blend. Fiberballs according to claim 1, wherein the binder fibers comprise bicomponent fibers of cut length about 10 to about 100 mm, one component of which is binder material, whereas another component is polyester fiber of melting point higher than that of the binder material. Fiberballs according to claim 2, wherein the binder material comprises about 5 to about 50% of the weight of the bicomponent fiber. Fiberballs according to claim 2 or 3, wherein the binder fiber is helically crimped. Fiberballs of average dimension of about 2 to about 15 mm containing essentially entangled polyester fiberfill, characterized in that the polyester fibers are randomly arranged, helically crimped and have a cut length of about 10 to about 100 mm, and that the polyester fibers are bicomponent fibers, one component of which is the polyester and the other component is binder material having a melting point which is at least 20°C lower than that of the polyester. Fiberballs according to any of claims 1 to 5; wherein the fiberfill has a coating cured thereto of a slickener consisting essentially of chains of poly(alkylene oxide). Fiberballs according to claim 6, wherein the fiberfill is coated with a segmented copolymer of poly(ethylene terephthalate) and poly(ethylene oxide) in amount about 0.05 to about 1% of the weight of the fiberfill. Fiberballs according to claim 6, wherein the fiberfill is coated with a modified poly(ethylene oxide)/poly(propylene oxide) grafted with functional groups to permit crosslinking. Process for making polyester fiberballs from a blend of helically crimped fiberfill having a cut fiber length of about 10 to about 100 mm with binder fibers comprising a fiber material having a melting point which is at least 20°C lower than that of the polyester, in an amount of about 5 to about 50% by weight of the blend, wherein small tufts of the blend are repeatedly tumbled by air against the wall of a vessel to provide the fiberballs. Process for making polyester fiberballs from helically crimped bicomponent polyester/binder material fibers, wherein one component is the polyester and the other component is a binder material having a melting point which is at least 20°C lower than that of the polyester, wherein small tufts of the helically crimped fibers are repeatedly tumbled by air against the wall of a vessel to provide the fiberballs. Process according to claim 9 or 10, wherein the polyester fibers have been mechanically crimped by passing through a stuffer box under mild gate and roll pressures. Process according to any of claims 9 to 11, wherein the tufts are tumbled against a cylindrical wall of a vessel by air stirred by blades attached to a shaft rotating axially in the vessel. Process according to Claim 12, wherein the small tufts and the air are recirculated through the vessel. Process acording to any of Claims 9 to 13, wherein the tufts are formed by feeding loose fibers into the vessel, and by rotating the shaft and blades at a speed such that the fiberfill is separated into the small tufts. Process according to any of Claims 9 to 13, wherein small tufts that are not elongated are formed before feeding them into the vessel for rounding and condensing by air-tumbling. Process according to any of Claims 9 to 15, wherein the fibers are treated with a slickener to reduce the hairiness of the resulting fiberballs. Process for making a bonded product, wherein an assembly of fiberballs according to any of Claims 1 to 8 are heat-bonded and cooled. Process according to Claim 17, wherein the fiberballs are first mixed with random binder fiber before forming an assembly and heat-bonding. Process according to Claim 17 or 18, wherein the assembly is heat-bonded in a mold 50 as to produce a molded structure. Process for making bonded fiberballs, wherein individual fiberballs according to any of Claims 1 to 8 are individually heat-bonded and cooled. Process for making bonded fiberballs according to claim 20, wherein the fiberballs are individually heat-bonded in an airstream and cooled. Process for making a loose bonded assembly, wherein bonded fiberballs are made according to Claim 20 or 21, and then assembled in a ticking.

Inventors: MARCUS, ILAN
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1987
Main classification: D04H1
IPC codes: A47G9, D04H1, B68G7, D06M15, B68G1