Steric net-like fiber aggregation

Abstract

There is provided a steric net-like fiber aggregation, comprising fibers having a fineness of 150 to 100000 dtex, the fibers being made of a resin comprising a propylene-based polymer(a), wherein a multitude of the fibers are in a fusion bonding with each other due to a random orientation of melted fibers, and wherein the propylene-based polymer(a) has a structural unit of 51 to 95 percent by mole of a propylene and 5 to 49 percent by mole of an -olefin with respect to 100 percent by mole of the total monomers of the propylene-based polymer(a).

Claims

1. A steric net-like fiber aggregation, comprising fibers having a fineness of 150 to 60000 dtex, the fibers being made of a resin that is a polymer alloy made of a propylene-based polymer(a) and a propylene homopolymer(b), wherein the steric net-like fiber aggregation has a structure formed of a multitude of the fibers fusion bonded in a random orientation with each other, wherein the propylene-based polymer(a) has a structural unit of 51 to 95 percent by mole of a propylene and 5 to 49 percent by mole of an -olefin with respect to 100 percent by mole of the total monomers of the propylene-based polymer(a), wherein the steric net-like fiber aggregation has an apparent density in the range of 0.020 g/cm.sup.3 to 0.300 g/cm.sup.3, wherein the steric net-like fiber aggregation has a thickness in the range of 5 mm to 120 mm, and wherein a ratio of a compression stress under a compressibility of 50% to the compression stress under the compressibility of 25% is in the range of 1.7 to 3.0.

2. The steric net-like fiber aggregation according to claim 1, wherein a number of carbon atoms contained in the -olefin is 2 to 10.

3. The steric net-like fiber aggregation according to claim 2, wherein the -olefin with the number of the carbon atoms contained therein being 2 to 10 is at least one selected from a group consisting of ethylene, 1-butene, 1-pentene, 1-hexene and 1-octene.

4. The steric net-like fiber aggregation according to claim 1, wherein the propylene-based polymer(a) has a molecular weight distribution M.sub.w/M.sub.n of 4.0 or less.

5. The steric net-like fiber aggregation according to claim 1, wherein the polymer alloy comprises 10 to 80 percent by weight of the propylene homopolymer(b) with respect to 100 percent by weight of the whole polymer alloy.

6. The steric net-like fiber aggregation according to claim 1, wherein the propylene homopolymer(b) has a molecular weight distribution M.sub.w/M.sub.n of 2.0 to 6.0.

7. The steric net-like fiber aggregation according to claim 1, wherein a weight change rate of the steric net-like fiber aggregation is 0% after an immersion of the steric net-like fiber aggregation into an alcohol during the whole day.

8. The steric net-like fiber aggregation according to claim 1, wherein the steric net-like fiber aggregation is one used as a medical or nursing-care appliance.

9. The steric net-like fiber aggregation according to claim 1, wherein the structure of the steric net-like fiber aggregation is formed due to the fusion bonding of the multitude of the fibers through a buoyant force of a water bath.

10. The steric net-like fiber aggregation according to claim 1, wherein the ratio of a compression stress under a compressibility of 50% to the compression stress under the compressibility of 25% is in the range of 1.9 to 3.0.

11. The steric net-like fiber aggregation according to claim 1, wherein the ratio of a compression stress under a compressibility of 50% to the compression stress under the compressibility of 25% is in the range of 2.08 to 3.0.

12. The steric net-like fiber aggregation according to claim 1, wherein the propylene-based polymer(a) has a structural unit of 70 to 80 percent by mole of the propylene and 20 to 30 percent by mole of the -olefin with respect to 100 percent by mole of the total monomers of the propylene-based polymer(a).

13. The steric net-like fiber aggregation according to claim 1, wherein the polymer alloy in the steric net-like fiber aggregation comprises the propylene homopolymer(b) in the range of 10 to 50 weight % with respect to 100 weight % of the whole polymer alloy.

Description

EXAMPLES

(1) The present invention will now be described in more detail, referring to Examples and Comparative examples although the present invention is not necessarily limited to them.

(2) The twin screw extruder was used to mix the component(s) according to Table 1. The temperature of the twin screw extruder from upstream to downstream thereof was set stepwise from about 140 C. to about 200 C. The melting and mixing process in the twin screw extruder was performed at 1000 rpm, and subsequently the melted resin was continuously discharged downward from the T-die with its temperature of about 200 C. The fibrous resin discharged from the plurality of pores of the T-die was allowed to enter the water bath (room temperature) located immediately below the T-die, followed by being allowed to pass between the two parallel conveyors disposed in the bath. As a result, the fibers made of the resin were forced to undergo a fusion bonding with each other, whereby there was eventually formed the steric net-like fiber aggregation.

(3) Regarding Examples 1-7 and Comparative examples 1-2 listed in Table 1, the following were used as the components a and b.

(4) Component a: Propylene-Based Polymer

(5) Component a-1: WELNEX STR0729 produced by Japan Polypropylene (Metallocene-catalyzed random copolymer), Weight-average molecular weight M.sub.w 320000, Molecular weight distribution M.sub.w/M.sub.n 2.50, Propylene (75 mol %):Ethylene (25 mol %) Component a-2: WELNEX STR0730 produced by Japan Polypropylene (Metallocene-catalyzed random copolymer), Weight-average molecular weight M.sub.w 320000, Molecular weight distribution M.sub.w/M.sub.n 2.50, Propylene (75 mol %):Ethylene (25 mol %) Component a-3: PRIMALLOY A1700 produced by Mitsubishi Chemical Corporation (Polyester-based thermoplastic elastomer) Component a-4: KERNEL KS571 produced by Japan Polyethylene Corporation (polyethylene-based copolymer: copolymer of polyethylene and -olefin)
Component b: Propylene Homopolymer Component b-1: GC4301 produced by Japan Polypropylene Corporation, Weight-average molecular weight M.sub.w 330000, Molecular weight distribution M.sub.w/M.sub.n 3.86 Component b-2: NOVATEC MA-2 produced by Japan Polypropylene Corporation, Weight-average molecular weight M.sub.w 426000, Molecular weight distribution M.sub.w/M.sub.n 3.41

(6) TABLE-US-00001 TABLE 1 Blending Comparative (parts by Examples examples mass) 1 2 3 4 5 6 7 1 2 Component 100 80 60 70 50 30 (a-1) Component 100 (a-2) Component 100 (a-3) Component 100 (a-4) Component 20 40 (b-1) Component 30 50 70 (b-2)

(7) For each of the steric net-like fiber aggregations as described above, the fineness, the thickness, the apparent density, and the mass per unit area were determined. The results for the determinations are listed below in Table 2. Regarding the determination for the commercially available steric net-like fiber aggregation, Comparative example 3 was also conducted, the commercially available aggregation being made of an polyethylene-based copolymer (AIRWEAVE, AWC-01 with no cover). As for the determined values listed in Table 2, they are ones that were respectively averaged for ten or more samples in each of the aggregations.

(8) TABLE-US-00002 TABLE 2 Comparative Examples examples 1 2 3 4 5 6 7 1 2 3 Fineness 1900 5000 5400 5600 8200 8500 8850 1800 2800 4100 (dtex) Thickness 37.8 28.9 28.8 33.7 35.9 35.5 35.2 23.5 61.3 36.0 (mm) Apparent 0.040 0.063 0.078 0.065 0.063 0.060 0.057 0.072 0.040 0.064 density (g/cm.sup.3) Mass per 1.51 1.82 2.25 2.19 2.26 2.13 2.00 1.69 2.45 2.30 unit area (kg/m.sup.2)

(9) Moreover, the following evaluation tests were conducted for each of the steric net-like fiber aggregations.

(10) 1. Odor Evaluation

(11) Each of the steric net-like fiber aggregations produced as described above according to Table 1 was cut to provide a sample piece with its size of 200 mm by 200 mm. Each sample piece was kept in the shade and airy area for a week, and thereafter was left in the medical room (with its size of about six-tatami) at the hospital (Kansai-region hospital) for the whole 3 days. Each of the resultant sample pieces was subjected to a sensory test on odor. Such sensory test was conducted at a point in time before and after the sample piece was left in the above medical room of the hospital. The evaluations for the sensory test were done for three persons (i.e., two males and one female). The evaluation (GOOD) was given in the case of no odor or no disturbing, the evaluation (MEDIOCRE) was given in the case of slight odor or a little disturbing, and the evaluation (BAD) was given in the case of odor or disturbing. As for the sensory test before the disposing of the sample piece in the medical room of the hospital, it was conducted immediately after an enclosing of the sample piece in the plastic bag for 10 minutes. The results for the sensory test are shown in Table 3.

(12) TABLE-US-00003 TABLE 3 Comparative Examples examples 1 2 3 4 5 6 7 1 2 3 Male Before x 1 left After x left Male Before 2 left After x left Female Before 1 left After x left

(13) As can be seen from Table 3, the steric net-like fiber aggregation according to the present invention exhibited a better result of the sensory test both before and after the sample piece had been left in the medical room of the hospital, which means that the steric net-like fiber aggregation of the present invention has a less odor. While on the other hand, the steric net-like fiber aggregation according to Comparative example 1 wherein the aggregation was made of the polyester-based thermoplastic elastomer had odor before the sample piece had been left in the medical room at the hospital, and also had tendency to get worse in its odor after the sample piece had been left in the medical room.

(14) 2. Chemical Resistance Evaluation

(15) Each of the steric net-like fiber aggregations produced as described above according to Table 1 was cut to provide a sample piece with its size of 20 mm by 50 mm. Each sample piece was immersed in an ethanol (KISHIDA CHEMICAL Co., Ltd., primary alcohol, product code: 010-28555) for 1 day (i.e., during the whole day) under a room temperature. The ethanol was one used for a sterilization treatment at the hospital and the like. The evaluation (GOOD) was given in the case where the weight change rate after the above 1 day was 0%, the evaluation (MEDIOCRE) was given in the case where the weight change rate after the above 1 day was higher than 0% and 1% or lower, and the evaluation (BAD) was given in the case where the weight change rate after the above 1 day was higher than 1%. The weight change rate in this evaluation was based on the weight of each sample piece at a point in time before the immersion of the sample piece into the ethanol. The results for the chemical resistance evaluation are shown in Table 4.

(16) 3. Heat Resistance Evaluation

(17) Each of the steric net-like fiber aggregations produced as described above according to Table 1 was cut to provide a sample piece with its size of 100 mm by 100 mm. In light of the fact that a hot-water treatment (100 C.) or a heat treatment (121-135 C.) is usually conducted at the hospital as a sterilization treatment, each sample piece was placed for 30 minutes in a thermostatic chamber (100 C., 121 C., 135 C.) under an atmospheric pressure. The evaluation (GOOD) was given in the case where all of dimension change rates (i.e., change rates of depth dimension, width dimension and height dimension of sample piece) after the above 30 minutes was 5% or less, the evaluation (MEDIOCRE) was given in the case where the all of dimension change rates of the sample piece after the above 30 minutes was more than 5% and 70% or less, and the evaluation (BAD) was given in the case where the sample piece had been dissolved. The dimension change rate in this evaluation was based on the depth dimension, width dimension and height dimension of each sample piece at a point in time before the placement of the sample piece into the thermostatic chamber. The results for the heat resistance evaluation are shown in Table 4.

(18) 4. Compression Stress Stability Evaluation (Evaluation of Stability in Terms of Compression Stress)

(19) Each of the steric net-like fiber aggregations produced as described above according to Table 1 was cut to provide a sample piece with its size of 200 mm by 200 mm. For each sample piece, a compression stress test was conducted according to JIS K 6400 using Tensilon (RTG-1250A, Orientec Corporation). A pressure plate with 100 was used, 50 mm/minute was employed as a test speed, and also no preliminary compression was conducted. The compression stresses under the compressibility of 25% and 50% were determined, and thereby a ratio of the compression stress under the compressibility of 50% to the compression stress under the compressibility of 25% was calculated. As for such ratio, a lower one indicates that a difference in compression stress is smaller between a higher compressibility condition (such as 50% compressibility and the like) and a lower compressibility condition (such as 25% compressibility and the like). The results for the compression stress test are shown in Table 4.

(20) TABLE-US-00004 TABLE 4 Comparative Examples examples 1 2 3 4 5 6 7 1 2 3 Odor x (Sensory test) Chemical resistance x (weight change ratio after immersion into ethanol) Heat Temperature x resistance condition: (dimension 100 C. stability Temperature x x x x after 30 condition: minutes) 121 C. Temperature x x x x condition: 135 C. Compression stress 1.76 1.90 2.80 2.10 1.90 1.87 2.08 1.80 1.60 1.50 stability (50% compression strength/ 25% compression strength)

(21) As can be seen from the above results, the steric net-like fiber aggregations of the present invention according to Examples 1 and 2 had the improved chemical resistance. The steric net-like fiber aggregations of the present invention also had the favorable results for the compression stress stability, which means that the aggregation according to the present invention does not undergo a large variation in the compression stress even when the different compressibility conditions are given. For example, the user's stress received from the compressed aggregation can be mitigated in the present invention since the variation in the pressure applied onto the user by the compressed aggregation can be suppressed. Further, as can be seen from Examples 3-7, the steric net-like fiber aggregations produced using the polymer alloy according to the present invention had the favorable results for the heat resistance evaluation at the temperature conditions of 121 C. and 135 C. as well as 100 C. This means that the steric net-like fiber aggregation of the present invention has the more improved heat resistance. In this regard, such higher heat resistance makes it possible for the user to repeatedly use the steric net-like fiber aggregation without a deformation of the aggregation even when a high-temperature cleaning/sterilization treatment thereof is conducted. Furthermore, as can be seen from Examples 1-7, the steric net-like fiber aggregations according to the present invention had the favorable results for the odor evaluation. While on the other hand, as can be seen from Comparative example 1, the steric net-like fiber aggregation produced using the polyester-based thermoplastic elastomer had the poor result for the chemical resistance evaluation, which means that such aggregation cannot solve the problem associated with the present invention. The steric net-like fiber aggregation according to Comparative example 1 also had the poor result for the odor evaluation, and the sticky surface of the aggregation according to Comparative example 1 was also observed, which brought about the discomfort feeling of the user in terms of texture and odor of the aggregation. Moreover, as can be seen from Comparative examples 2 and 3, the steric net-like fiber aggregations produced using the polyethylene-based polymer had the poor results for the chemical and heat resistances despite the favorable result for the compression stress stability.

(22) Although some embodiments of the present invention have been hereinbefore described, they are merely provided as typical examples of the present invention. It will be readily appreciated by those skilled in the art that the present invention is not limited to the embodiments as described above, and thus various modifications thereof are possible without departing from the scope of the present invention.

INDUSTRIAL APPLICABILITY

(23) The steric net-like fiber aggregation of the present invention can be used in the medical/nursing-care device or the like. For example, the steric net-like fiber aggregation of the present invention can be used in a medical or nursing-care bed or chair/couch, a cushion material for an operating table or the like, a floor material for a bathroom, a restroom (toilet) or the like, a cushion material in general, a medical or nursing-care supporter/fixing (especially a core material or belt material for a neck or waist corset or the like), or the like.

CROSS REFERENCE TO RELATED PATENT APPLICATION

(24) The present application claims the right of priority of Japanese Patent Application No. 2014-139015 (filed on Jul. 4, 2014, the title of the invention: STERIC NET-LIKE FIBER AGGREGATION), the disclosure of which is incorporated herein by reference in its entirety.