ULTRA-BULKY FIBER AGGREGATE AND PRODUCTION METHOD THEREOF

Abstract: This ultra-bulky fiber aggregate is obtained by blending (A) a polyester fiber and (B) a core-sheath type composite fiber wherein a low melting point component lower in melting point than the core is used for the sheath. The interlacing portions of three-dimensionally continuous fibers are fused by melting of the sheath portions of the core-sheath type composite fiber. The fiber aggregate has a thickness of at least 200 mm and a density of 0.02 to 0.1 g/cm³, and varies in density within ± 5 % in all of the longitudinal and transverse directions and the direction of height. The fiber aggregate can be used as a shoulder pat and a cushion material when it is cut. The production method of this fiber aggregate comprises blending (A) a polyester fiber and (B) a core-sheath type composite fiber using a low melting point component lower in melting point than the core for the sheath to obtain a card web, temporarily fusing card webs by far infrared rays or a hot air heater to laminate webs as required by a predetermined density and a predetermined thickness, and heat-treating the resulting laminate so as to mutually fuse the layers forming the laminate, wherein the heat-treatment is carried out by placing the laminate into a steam oven while it is compressed and clamped between two upper and lower plates and introducing the steam, the laminate being subjected to the heat-treatment while kept erect.

Description: Technical Field The present invention relates to a method for preparing an ultra-bulky fibre aggregate consisting of polyester fibre aggregate which contains a binder fibre having a low melting point. Background of the Invention Various cushion materials made of polyester fibre have been developed. However no product showing no strain by compression load and having voluminous feel has been prepared. We have investigated and developed a method for the preparation of a cushion material, which can be used as a bed mat and the like and has a voluminous feel and a high quality, by using a conjugate fibre consisting of polyester (Japanese Laid-Open Patent Publication No. 154050 of 1990). The method consists of a procedure in which polyester fibres (A) are mixed with core-sheath type composite or conjugate fibres (B) in which a sheath component of a lower melting point than that of the core component is used in a specified ratio and the resultant card web is temporarily melt-adhered with far-infrared radiation or with a hot air circulating heater and the temporarily adhered webs are laminated according to the desired density and thickness and then the laminated webs are heated to melt-adhere together the webs. By this method a cushion material of approximately 10 cm thick can be prepared. However, when the webs are horizontally laminated and continuously heated in dry air, an increased thickness restricts the uniformity of the density and heat transmission. Also, in the case of a batch steaming system, an excessive thickness gives a vertical density gradient by the weight of the fibres themselves and results in an uneven product. Therefore, even the method described in Japanese Laid-Open Patent Publication No. 154050 of 1990 could not prepare stably a cushion material of as high a thickness as 20 cm or 50 cam in a uniform density. Thus, an object of the present invention is to eliminate the disadvantages of the conventional technologies as mentioned above and to provide a product by using polyester fibres, which is an ultra-bulky block fibre aggregate having a high thickness of at least 20 cm, preferably 100 cm, and a uniform density in all of three directions like a urethane foam and can be used as a cushion material and a shoulder pad when sliced, and also to provide a method for the stable preparation thereof. EP-A-0 371 807 discloses a block fibre aggregate prepared by mixing polyester fibres and core-sheath type composite fibres. JP-A-2-154050 discloses a similar block fibre aggregate wherein the density is of 0.02 to 0.1 g/cm 3 and the scattering of the density is within ±5% in all the three directions. Disclosure of the Invention The present invention can provide an ultra-bulky block fibre aggregate, which can be sliced in the same manner as urethane foam, by devising the material for the fibre aggregate and the heating method. In accordance with a first aspect of the present invention there is provided an ultra-bulky block fibre aggregate capable of being sliced in the same manner as urethane foam, which is prepared by blending polyester fibres (A) and core-sheath type composite fibres (B) in which a material having a lower melting point than that of the core is used as the sheath, characterized in that cubically continued intertwined parts of the fibres are melt-adhered by the fusion of the sheath part of said core-sheath type composite fibres and the fibre aggregate has a thickness of at least 200 mm and a density of 0.02 to 0.1 g/cm 3 and a scattering of the density within ±5% in all of the three directions. Such an ultra-bulky block fibre aggregate may be prepared by a method in accordance with a second aspect of the invention. In accordance with the second aspect of the invention there is provided a method for the preparation of an ultra-bulky fibre aggregate capable of being sliced in the same manner as urethane foam, comprising preparing a card web by blending polyester fibres (A) and core-sheath type composite fibres (B) in which a material having a lower melting point than that of the core is used as the sheath, temporarily melt-adhering the card web by heating with far-infrared radiation or with a hot air circulating heater, laminating the temporarily adhered webs according to the desired density and thickness and then heating the laminate to heat-adhere together the webs constituting the laminate, characterized in that said heat treatment is carried out in a manner as said laminate is compressed between two upper and lower plates and fed in a steam vessel and steam is introduced to the vessel and said laminate is heated under a condition of standing or rotating the laminate to change its own weight to a different direction from that during lamination of the web to produce the fibre aggregate having a thickness of at least 200 mm and a density of 0.02 to 0.1 g/cm 3 and a scattering of the density within ±5% in all of the three directions. Thus, the present invention provides a fibre aggregate by a procedure in which webs open by a card are piled to a specified basis weight, for example, by cross layer method to prepare a non-woven fabric in which the fibres are arranged transversely and the non-woven fabric is layered and united to give a fibre aggregate. The laminate is compressed between two upper and lower plates to the desired density and thickness and then turned to press the fibre aggregate by its own weight to a different direction from that during lamination of the webs, such as turned by 90° so that the width direction (direction of fibre orientation) becomes vertical or turned by 90° transversely so that the standing direction becomes parallel to the fibre orientation, and then heat-set. The downward movement of the fibres by its own weight is prevented by the horizontal repulsive power of the fibre to give an ultra-bulky fibre aggregate having a uniform density to both directions of X and Y axis regardless of the thickness. Such a method can prepare a fibre aggregate of an optional density regardless of the thickness of the fibre aggregate by always applying the horizontal repulsive power. For example, a low density product can be prepared by increasing the web thickness (by lowering the density), while a high density product can be prepared by decreasing the thickness (by increasing the density) even in a same basis weight. In the present invention, the fibre aggregate can be heated while being rotated so that its own weight does not deviate to a direction. As the polyester fibre (A) in the present invention, usual polyethylene terephthalate, polyhexamethylene terephthalate, polytetramethylene terephthalate, poly-1,4-dimethylcyclohexane, terephthalate, polyhydrolactone or a copolymerized ester thereof or a composite fibre prepared by conjugate spinning can be used. A side-by-side type composite fibre consisting of two polymers of different heat shrinkage rate is preferred as it expresses a spiral crimp to form a cubic structure. Particularly, a hollow yarn of a percentage of hollowness of 5 to 30% is preferred. It is preferred to use a fibre of a fineness of 4 to 30 denier and a cut length of 25 to 150 mm. Further, as the core-sheath type composite fibre (B), there can be used a composite fibre prepared by using a conventional polyester fibre as the core and a low melting polyester, polyolefin or polyamide as the sheath so that the difference between the melting points of the core component and the sheath component is at least 30°C. It is preferred to use a fibre having a fineness of 2 to 20 denier and a cut length of 25 to 76 mm. As the core-sheath type composite fibre (B), particularly it is preferred to use a low melting polyester. Such polyesters are copolymerized esters which contain aliphatic dicarboxylic acids such as adipic acid and sebacic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and naphthalenedicarboxylic acid and/or alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid and aliphatic or aromatic diols such as diethylene glycol, polyethylene glycol, propylene glycol and paraxylene glycol in specified numbers and also contain if required oxy acid such as parahydroxybenzoic acid. For example, it can be exemplified by a polyester prepared by adding isophthalic acid and 1,6-hexanediol to terephthalic acid and ethylene glycol and copolymerizing them. According to the present invention, the surface of card webs of a low basis weight prepared by mixing the fibres of (A) and (B) in such as a weight ratio 95-40 : 5-60 is temporarily melt-adhered by heating with far-infrared radiation or with a hot air circulating heater, and the temporarily adhered webs are laminated according to the desired density and thickness, and then the laminate is compressed between two plates such as metal plates of high heat conductivity and the sandwiched laminate is stood up so that the thickness direction of the layers of the laminated webs is vertical and heated in a steam vessel. The temporary adhesion and heating are preferably carried out at a temperature which can melt the sheath component of the fibre (B) but cannot melt each of the fibre (A) and the core component of the fibre (B). The heating is preferably carried out by evacuating the steam vessel to a pressure of 750 mm Hg or less and then introducing steam of at least 1 kg/cm 2 to said steam vessel. The plates compressing the laminate comprises preferably perforated plates. As the laminate is heated under compressed vertical condition so that the load does not affect to the thickness direction of the laminate, even a fibre aggregate of as high a thickness as 50 cm or 100 cm can be melt-adhered uniformly to the inner layer to prepare efficiently a product excellent in feel and appearance. A product can be easily prepared with a desired density, the scattering range of which is within ±5%. Also, a fiber aggregate having a hardness of not lower than 10 g/cm 2 can be prepared stably. In the present invention, other fibers may be blended as the third component. Further, at least part of the fibers used in the present invention may be replaced by latent-crimping polyester composite fibers, antibacterial polyester fibers containing an antibacterial agent such as antibacterial zeolite or flame-retarding polyester fibers. It is preferred that a hollow composite fiber is used as the main fiber (a) constituting the fiber aggregate according to the present invention. It is because the fiber directions of the webs intertwine irregularly and melt-adhered at the interlocked sites with the low melting component of the core-sheath type composite fiber to form a cubic structure and hence a product of very low strain caused by repeated compression load can be prepared. Brief Description of the Drawings Fig. 1 shows the conditions of a fiber laminate before and after a heat treatment in an example of the present invention. Fig. 2 shows an outlined drawing of a rotary setter used in an example of the present invention. Best Mode of Embodying the Invention Examples 1 to 6 (A) 80 weight % of hollow conjugated polyester fibers having a hollowness of 16.1 % ( fineness: 13 denier, cut length: 51 mm ) prepared by conjugating side-by-side a polyethylene terephthalate having a relative viscosity of 1.37 with a polyethylene terephthalate having a relative viscosity of 1.22 in a ratio of 1:1 and (B) 20 weight % of core-sheath type composite fibers ( fineness: 4 denier, cut length: 51 mm ) containing a polyethylene terephthalate having a melting point of 257°C as the core and a copolymerized polyester (terephthalic acid/isophthalic acid = 60/40) having a melting point of 110°C as the sheath were mixed together in a hopper feeder and carded and then made into a web having a weight of 350 g/cm 2 with a cross layer method. The web was passed through a far-infrared heater at 130°C continuously to give a melt-adhered web. A number of the resultant webs of 1.5 m wide and 2 m long was piled between two plates 1 and 2 and compressed sandwich-like to a thickness of the laminate of 50 cm or 1 m and the piled webs (fiber aggregate 3 ) (Refer to Fig. 1-A) was turned by 90° longitudinally so that the width direction becomes to be vertical (Refer to Fig. 1-B) and then fed in a steam oven at the position. Air in the steam oven (and in the web laminate in it) was evacuated with a vacuum pump to a pressure of 750 mmHg and then steam of 3 kg/cm 2 was fed to the steam oven the the laminate was heated at 132 ° C for 10 minutes. Steam in the oven was evacuated again with a vacuum pump to give a block fiber aggregate 150 cm wide, 200 cm long and 50 cm thick having a density of respectively 0.025, 0.035 and 0.05 g/cm 3 in which the webs were melt-adhered into a whole mass in the oven (Refer to Table 1). The resultant block fiber aggregate was restored to the original condition as shown in Fig. 1-C and sliced into 10 equal parts respectively to the horizontal direction (X axis) and the vertical direction (Y axis). Distributions of density and hardness, repeated compression and compression set of each portion were measured in accordance with JIS K6767 and K6401. The results are shown in Table 1. Example 7 Webs piled between two plates 1 and 2 (fiber aggregate 3 ) were turned by 90 ° transversely so that the standing direction was parallel to the fiber orientation in the same manner as in Example 4 and then heated in the same manner as in Example 4. The results of physical properties of the resultant block fiber aggregates are shown in Table 1. Comparative Examples 1 to 3 Webs were piled to 30 cm to 50 cm thick so that the piled web density was respectively 0.025, 0.035 and 0.055 g/cm 3 in the same manner as in Example 1 and the piled webs were heated under a condition the width direction was horizontal as shown in Fig. 1 A under the same condition as in Example 1. The resultant block fiber aggregates were sliced into 10 equal parts to the X and Y axis directions and the distributions of density and hardness were measured. The results are shown in Tables 1 and 2. Sample Block thickness (cm) Slice direction Measured average density (g/cm 3 ) Density gradient (g/cm 3 ) Density scattering (%) Hardness of the fiber oriented surface Upper limit Lower limit Upper limit Lower limit Average Upper limit Lower limit Example 1 50 X axis 0.0273 0.0280 0.0268 +2.6 -1.8 33 34 31 Y axis 0.0270 0.0280 0.0263 +4.5 -1.9 - - - 2 100 X axis 0.0275 0.0281 0.0269 +2.2 -2.2 34 35 34 Y axis 0.0275 0.0281 0.0265 +2.2 -3.6 - - - 3 50 X axis 0.0369 0.0373 0.0363 +1.1 -1.6 48 48 47 Y axis 0.0370 0.0375 0.0363 +4.1 -1.9 - - - 4 100 X axis 0.0370 0.0378 0.0364 +2.2 -1.6 50 51 49 Y axis 0.0371 0.0376 0.0360 +1.3 -3.0 - - - 5 50 X axis 0.0495 0.0508 0.0491 +2.6 -0.8 64 65 63 Y axis 0.0505 0.0515 0.0480 +2.2 -4.9 - - - 6 100 X axis 0.0501 0.0510 0.0493 +1.8 -1.6 65 66 63 Y axis 0.0508 0.0515 0.0496 +1.4 -2.4 - - - 7 100 X axis 0.0367 0.0379 0.0361 +3.3 -1.6 - - - Y axis 0.0360 0.0374 0.0353 +3.7 -1.9 - - - Comparative Example 1 30 X axis 0.0263 0.0289 0.0240 +9.9 -8.7 30 36 25 2 40 X axis 0.0359 0.0393 0.0331 +9.4 -7.8 46 57 38 3 50 X axis 0.0510 0.0580 0.0424 +13.7 -16.9 62 79 43 Note) The "density scattering" shows the range of density scattering based on the average density. Sample Block thickness (cm) Slice direction Density (g/cm 3 ) Compression hardness (kgf/cm 2 ) Compression set (%) Repeated compression set (%) Example 2 100 X axis 0.0281 4.3 × 10 -2 6.7 6.3 0.0269 4.2 × 10 -2 6.6 5.8 4 100 X axis 0.0378 9.5 × 10 -2 8.3 7.5 0.0364 9.3 × 10 -2 8.1 6.8 6 100 X axis 0.0510 21.2 × 10 -2 10.2 8.8 0.0493 20.4 × 10 -2 9.7 8.5 Comparative Example 3 50 X axis 0.0580 27.6 × 10 -2 12.9 13.4 0.0424 15.7 × 10 -2 9.8 10.2 Test method 1. Surface hardness ( hardness of fiber-oriented surface ) Nine positions of each surfaces sliced to the X axis direction were measured by using an Asker F type hardness meter. Their average is shown. 2. Average density The volume and the weight of each sample sliced to X axis and Y axis direction were measured and their average values were calculated. 3. Density difference From the average density of each sample sliced into 10 layers to X axis and Y axis direction, the quality was judged by a criterion that the fluctuation of the densities between the upper and lower limits was within ±5%. 4. Compression hardness (in accordance with JIS K6401) A sample of 150 × 150 mm size was placed between two parallel upper and lower compression plates and compressed at a rate of 10 mm/sec or less to 0.36 kgf and then the thickness was measured at that time to as the initial thickness. Then it was compressed to 25 % of the initial thickness and stood for 20 seconds and the load was read to give the hardness value. 5. Compression set A sample of 150 × 150 mm size was placed between two parallel upper and lower compression plates and compressed to 50 % of the initial thickness and stood at room temperature for 40 hours and then the compression plates were removed and the sample was stood for 30 minutes and the thickness was measured. Compression set (%) = (t 0 - t 1 ) × 100/t 0 t 0 : Initial sample thickness (mm) t 1 : Sample thickness after tested (mmZ). 6. Repeated compression set A sample of 150 × 150 mm size was placed between two parallel upper and lower compression plates and compressed repeatedly for continuous 80,000 times to 50 % of the sample thickness at a rate of 60 times a minute at room temperature and then the sample was removed and stood for 30 minutes and the thickness was measured and the compression set was calculated by the same equation as above. From the measurements of Tables 1 and 2, it can be found that the ultra-bulky fiber aggregates of each densities prepared according to the present invention were focused in a very narrow range of density gradient at any part of X or Y direction and had a definite hardness depending on their densities and thus they were uniform fiber aggregates of excellent quality regardless of their thicknesses and densities. Therefore, it can be found that they are fiber aggregates of low strain and of excellent elasticity in the compression characteristics. Example 8 The method of Example 7 was carried out by using a rotary setter shown in Fig. 2. This equipment has a structure in which a fiber aggregate 3 placed between the plates 1 and 2 is held by a plate support 4 in a can 8 and equipped to a rotary shaft 7 rotated by a drive motor 6 through a joint 5 . It can heat the aggregate 3 while rotated in the can 8 . This method can heat the fiber aggregate under a condition in which the direction of its weight scatters and hence a product of very low fluctuation in density can be prepared. Industrial Applicability of the Invention As a thick block fiber aggregate can be obtained in the present invention, it can be sliced to make a shoulder pad, a cushion material, an automobile seat and the like. Further, as the fiber aggregate can be molded by heat and other means, it can be also used as a molding material. Such molding methods improve productivity and reduce manufacturing cost. Furthermore, the inventive method has an advantage of reducing the treating period as it is higher in heat efficiency than the conventional multiple plate process.

Claims: An ultra-bulky block fibre aggregate capable of being sliced in the same manner as urethane foam, which is prepared by blending polyester fibres (A) and core-sheath type composite fibres (B) in which a material having a lower melting point than that of the core is used as the sheath, characterized in that cubically continued intertwined parts of the fibres are melt-adhered by the fusion of the sheath part of said core-sheath type composite fibres and the fibre aggregate has a thickness of at least 200 mm and a density of 0.02 to 0.1 g/cm 3 and a scattering of the density within ±5% in all of the three directions. An ultra-bulky block fibre aggregate according to claim 1, in which said polyester fibre (A) is a side-by-side type composite fibre consisting of two polymers having a different heat shrinkage rate. An ultra-bulky block fibre aggregate according to Claim 1 or 2, in which said polyester fibre (A) is a hollow yarn having a percentage of hollowness of 5 to 30 %. An ultra-bulky block fibre aggregate according to any of Claims 1 to 3, in which said polyester fibre (A) has a fineness of 4 to 30 denier and a cut length of 25 to 150 mm. An ultra-bulky block fibre aggregate according to any of Claims 1 to 4, in which the difference between the melting points of the core and the sheath of said core-sheath type composite fibre (B) is at least 30°C and the core consists of a polyester fibre component and the sheath consists of a low-melting polyester, polyolefin or polyamide. An ultra-bulky block fibre aggregate according to any of Claims 1 to 5, in which said core-sheath type composite fibre (B) has a fineness of 2 to 20 denier and a cut length of 25 to 76 mm. An ultra-bulky block fibre aggregate according to any of Claims 1 to 6, in which the mixing ratio of said fibres (A) and (B) is 95-40 : 5-60 by weight. A method for the preparation of an ultra-bulky fibre aggregate capable of being sliced in the same manner as urethane foam, comprising preparing a card web by blending polyester fibres (A) and core-sheath type composite fibres (B) in which a material having a lower melting point than that of the core is used as the sheath, temporarily melt-adhering the card web by heating with far-infrared radiation or with a hot air circulating heater, laminating the temporarily adhered webs according to the desired density and thickness and then heating the laminate to heat-adhere together the webs constituting the laminate, characterized in that said heat treatment is carried out in a manner as said laminate is compressed between two upper and lower plates and fed in a steam vessel and steam is introduced to the vessel and said laminate is heated under a condition of standing or rotating the laminate to change its own weight to a different direction from that during lamination of the web to produce the fibre aggregate having a thickness of at least 200 mm and a density of 0.02 to 0.1 g/cm 3 and a scattering of the density within ±5% in all of the three directions. A method according to claim 8, in which said temporary melt-adhesion and said heat-treatment are carried out at a temperature at which the sheath component of the above fibre (B) is molten but each of the fibre (A) and the core component of the fibre (B) is not molten. A method according to Claim 8 or 9, in which said polyester fibre (A) is a side-by-side type composite fibre consisting of two polymers having a different heat shrinkage rate. A method according to any of Claims 8 to 10, in which said polyester fibre (A) is a hollow yarn having a percentage of hollowness of 5 to 30%. A method according to any of Claims 8 to 11, in which said polyester fibre (A) has a fineness of 4 to 30 denier and a cut length of 25 to 150 mm. A method according to any of Claims 8 to 12, in which the difference between the melting points of the core and the sheath of said core-sheath type composite fibre (B) is at least 30°C and the core consists of a polyester fibre component and the sheath consists of a low-melting polyester, polyolefin or polyamide. A method according to any of Claims 8 to 13, in which said core-sheath type composite fibre (B) has a fineness of 2 to 20 denier and a cut length of 25 to 76 mm. A method according to any of Claims 8 to 14, in which the mixing ratio of said fibres (A) and (B) is 95-40 : 5-60 by weight.

Inventors: MASUDA YUGORO, NAGATA MAKIO, MASUDA, YUGORO, NAGATA, MAKIO
Applicants: KANEBO LTD, KANEBO, LTD.
Application year: 1993
Main classification: D04H1
IPC codes: D04H1, B68G5, D01D5