ANTIMICROBIAL FIBERS

Abstract

The invention provides an antimicrobial fiber which exhibits excellent antimicrobial properties even without the addition of antimicrobial agents and can remain antimicrobial even after repeated washing. The antimicrobial fiber comprises a fiber having on a surface thereof a polyacetal copolymer (X) containing oxyalkylene groups, the molar amount of oxyalkylene groups in the polyacetal copolymer (X) being 0.2 to 5 mol % relative to the total of the molar amount of oxymethylene groups and the molar amount of oxyalkylene groups.

Claims

1. An antimicrobial fiber comprising a fiber having a polyacetal copolymer (X) on a surface thereof, the polyacetal copolymer (X) having oxymethylene groups and oxyalkylene groups of the following general formula (1), the molar amount of the oxyalkylene groups in the polyacetal copolymer (X) being 0.2 to 5 mol % relative to the total of the molar amount of the oxymethylene groups and the molar amount of the oxyalkylene groups, ##STR00003## wherein R.sub.0 and R.sub.0, which may be the same as or different from each other, are each selected from a hydrogen atom, a C.sub.1-8 alkyl group, an organic group having a C.sub.1-8 alkyl group, a phenyl group and an organic group having a phenyl group, and m is an integer of 2 to 6.

2. The antimicrobial fiber according to claim 1, wherein the orientation factor of the polyacetal copolymer (X) is not less than 60%.

3. The antimicrobial fiber according to claim 1, wherein the fiber having the polyacetal copolymer (X) on a surface thereof is a monolayer fiber of the polyacetal copolymer (X).

4. The antimicrobial fiber according to claim 1, wherein the fiber having the polyacetal copolymer (X) on a surface thereof is a multilayer fiber having a coating of the polyacetal copolymer (X) on a fiber including a thermoplastic resin.

5. The antimicrobial fiber according to claim 1, wherein the fiber having the polyacetal copolymer (X) on a surface thereof is a conjugate fiber having the polyacetal copolymer (X) on a surface of a fiber including a thermoplastic resin.

6. The antimicrobial fiber according to claim 4, wherein the thermoplastic resin is one or more selected from polyacetal homopolymers, polyacetal copolymers other than the polyacetal copolymer (X), polyolefin resins, polylactic acid resins, nylon resins, polyester resins, polyvinyl resins and elastomers of these resins.

7. A nonwoven fabric comprising the antimicrobial fiber according to claim 1.

8. A filter comprising the nonwoven fabric according to claim 7.

9. A knitted fabric comprising the antimicrobial fiber according to claim 1.

10. A woven fabric comprising the antimicrobial fiber according to claim 1.

11. A felt comprising the antimicrobial fiber according to claim 1.

12. A web comprising the antimicrobial fiber according to claim 1.

13. A clothing article comprising one or more selected from the group consisting of the knitted fabrics, the woven fabrics, the felts and the webs according to claim 9.

14. A bedding article comprising one or more selected from the group consisting of the knitted fabrics, the woven fabrics, the felts and the webs according to claim 9.

15. An interior article comprising one or more selected from the group consisting of the knitted fabrics, the woven fabrics, the felts and the webs according to claim 9.

Description

EXAMPLES

[0077] Hereinbelow, embodiments and advantageous effects of the present invention will be described in detail by presenting Examples and Comparative Examples. The scope of the invention is not limited to such Examples.

[0078] <Polyacetal Copolymers>

[0079] The polyacetal copolymers used in Examples and Comparative Examples are described below. The content of oxyethylene groups (the molar amount of oxyethylene groups) in the polyacetal copolymer (X) is a value relative to the total of the molar amount of oxymethylene groups and the molar amount of oxyethylene groups.

POM-1: polyacetal copolymer having a content of oxyethylene groups of 0.4 mol % and an MVR of 8
POM-2: polyacetal copolymer having a content of oxyethylene groups of 1.6 mol % and an MVR of 8
POM-3: polyacetal copolymer having a content of oxyethylene groups of 3.0 mol % and an MVR of 8
POM-4: polyacetal copolymer having a content of oxyethylene groups of 4.7 mol % and an MVR of 8
POM-5: polyacetal copolymer having a content of oxyethylene groups of 5.7 mol % and an MVR of 8

[0080] <Other Thermoplastic Resins>

PLA (polylactic acid resin): TERRAMAC (registered trademark) TE2000 manufactured by UNITIKA LTD. was used as such.
PET (polyethylene terephthalate resin): multifilaments having a monofilament fineness of 2 decitex were used as such.

[0081] <Measurement of MVR>

[0082] The MVR (cm.sup.3/10 min) of the polyacetal copolymers was measured in accordance with ISO 1133.

[0083] <Measurement of Content of Oxyethylene Groups in Polyacetal Copolymers>

[0084] The polyacetal copolymers used in Examples and Comparative Examples were each dissolved into hexafluoroisopropanol (d2) to give NMR measurement samples. The measurement samples were analyzed to record NMR spectra, from which the contents of oxyethylene groups in the polyacetal copolymers were measured.

[0085] <Measurement of Fiber Fineness>

[0086] To determine the fiber fineness [dtex (decitex)], the fiber diameter of a monofilament was measured using an optical microscope, and the fineness was calculated assuming that the density was 1.40 g/cm.sup.3. The average of fifty fibers was obtained as the fiber fineness.

[0087] <Measurement of Orientation Factor Fc (%) of Fibers>

[0088] The measurement was performed with a wide angle X-ray diffractometer (DP-D1 manufactured by Shimadzu Corporation), using CuK (a Ni filter was used) as the radiation source (output 45 KV, 40 mA). The orientation factor (fc) was determined with respect to (100) plane observed at near 2=22.2 using the equation (1) below wherein FWHM was the full-width at half-maximum () of a diffraction intensity distribution curve (an azimuthal distribution curve) obtained by scanning in the circumferential direction.

fc (%)=((180FWHM)/180)100Equation (1)

[0089] <Fabrication of Fiber Samples>

[0090] The temperature of a cylinder and a nozzle portion was increased to 200 C. A molten resin was ejected through a nozzle having 48 holes 0.6 mm in diameter, at a rate of 1.2 kg/h. In the case of sheath-core conjugate fibers, the rate of ejection from the nozzle was 0.6 kg/h for each of the resin for the core and the resin for the sheath. During the process, the as-ejected fibers were continuously collected at a constant take-off speed of 100 m/min, and the as-ejected fibers were subsequently guided to a thermal drawing step in which the fibers were drawn at a roll temperature of 120 to 140 C. A fiber sample was thus fabricated.

[0091] <Fabrication of Nonwoven Fabrics and Filters>

[0092] The drawn fibers obtained above were crimped and were cut to a length of 51 mm. The fibers were then formed into a web with a carding machine (manufactured by Kyowa Kizai Seisakusho) and were entangled with a needle punching machine (manufactured by Daiwa Kikou) into a needle punched nonwoven fabric.

[0093] <Antimicrobial test (bacteriostatic activity, bactericidal activity, retention of bacteriostatic activity after 10 times of washing, and retention of bactericidal activity after 10 times of washing)>

[0094] In accordance with JIS L 1902 (Testing for antibacterial activity and efficacy on textile products), the antimicrobial properties were evaluated by a quantitative test (a bacterial liquid absorption method). A fiber sample of standard cotton cloth, and a fiber sample of any of Examples and Comparative Examples (hereinafter, written as the measurement sample), each weighing 0.4 g, were placed into respective vial containers and were inoculated with 0.2 ml of a test bacterial liquid. The bacteria were cultured at 372 C. for 181 hours. The bacteria were then washed out from the samples by the addition of 20 ml of physiological saline containing 0.2% nonionic surfactant. The bacterial count in the spent washing liquid was measured by a pour plate culture method (a colony method), and the bacteriostatic activity was calculated using the equation (2) below. The larger the value of bacteriostatic activity, the more excellent the antimicrobial properties. Incidentally, 2.2 or higher bacteriostatic activity on Staphylococcus aureus corresponds to the SEK mark (blue: antimicrobial and deodorant finished) certified by Japan Textile Evaluation Technology Council. Further, the bactericidal activity was calculated using the equation (3) below. The larger the value of bactericidal activity, the more excellent the antimicrobial properties. More than 0 activity means that bacteria are reduced in number between before and after the antimicrobial test.

Bacteriostatic activity={log(viable bacterial count after culture in standard cotton cloth)log(viable bacterial count immediately after inoculation on standard cotton cloth)}{log(viable bacterial count after culture in measurement sample)log(viable bacterial count immediately after inoculation on measurement sample)}Equation (2)

Bactericidal activity=log(viable bacterial count immediately after inoculation on standard cotton cloth)log(viable bacterial count after culture in measurement sample) Equation (3)

[0095] The retentions of bacteriostatic activity and bactericidal activity after 10 times of washing were determined in the following manner. The washing method was in conformity with JIS L 0217, No. 103, and the detergent was JAFET standard detergent. After being washed repeatedly 10 times, the samples were subjected to the above antimicrobial testing, and the retention [unit: %] of bacteriostatic activity after 10 times of washing was calculated using the equation (4) below. Further, the retention [unit: %] of bactericidal activity after 10 times of washing was calculated using the equation (5) below. In each case, the closer the value to 100%, the higher the antimicrobial properties.

Retention of bacteriostatic activity (%)=(bacteriostatic activity after 10 times of washing/bacteriostatic activity before washing treatment)100Equation (4)

Retention of bactericidal activity (%)=(bactericidal activity after 10 times of washing/bactericidal activity before washing treatment)100Equation (5)

[0096] The bacteriostatic activity, the bactericidal activity, and the retentions of bacteriostatic activity and bactericidal activity after 10 times of washing were measured on Staphylococcus aureus and Moraxella osloensis.

EXAMPLES AND COMPARATIVE EXAMPLES

[0097] Table 1 shows Examples of monolayer fibers of a polyacetal copolymer having an oxyethylene content in the prescribed range, multilayer fibers of polyacetal copolymers having an oxyethylene content in the prescribed range, and multilayer fibers of PLA and a polyacetal copolymer having an oxyethylene content in the prescribed range, and Comparative Examples of polyester fibers and monolayer fibers of a polyacetal copolymer having an oxyethylene content exceeding the prescribed range.

[0098] The table describes the oxyethylene content in the polyacetal copolymer, the monofilament fineness, the orientation factor, the viable bacterial count (unit: colonies) after culture in the aforementioned antimicrobial test, the increase ratio before and after the antimicrobial test, the bacteriostatic activity, the retention of bacteriostatic activity after 10 times of washing, the bactericidal activity, and the retention of bactericidal activity after 10 times of washing obtained in each of Examples and Comparative Examples.

[0099] From Examples 1 to 6 and Comparative Examples 1 and 2, it has been shown that excellent bacteriostatic activity, bactericidal activity and retention of bactericidal activity after washing are attained when the oxyethylene content in the polyacetal copolymer is 0.2 to 5 mol %. Examples 4 to 6 show that the bacteriostatic activity, the bactericidal activity and the retention of bactericidal activity after washing are further enhanced when the polyacetal copolymer in the fibers has a high orientation factor.

TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Raw materials of fibers POM-1 POM-2 POM-3 POM-4 POM-4 Oxyethylene content in polyacetal copolymer [mol %] 0.4 1.6 3.0 4.7 4.7 Melting point of polyacetal copolymer [ C.] 170 166 160 155 155 Draw temperature [ C.] 140 135 130 125 125 Draw ratio 5.2 5.2 5.2 5.2 8.3 Monofilament fineness [dtex] 8 8 8 8 5 Orientation factor of fibers [%] 87 84 84 82 93 Addition of antimicrobial agent No No No No No Antimicrobial test Staphylococcus Viable bacterial count after culture [colonies] 1.00.E+04 1.58.E+04 3.16.E+04 3.98.E+04 2.51.E+04 aureus Increase ratio(*3) before and after antimicrobial test 0.5 0.8 1.6 2.0 1.3 Bacteriostatic activity(*1) 2.9 (2.9) 2.7 2.4 2.3 2.5 Retention of bacteriostatic activity after 10 times 100 (100) 100 100 99 100 of washing [%](*1) Antimicrobial and deodorant finished certification(*2) Bactericidal activity(*1) 0.3 (0.3) 0.1 0.2 0.3 0.1 Retention of bactericidal activity after 10 times 100 (100) 100 100 97 100 of washing(*1) Moraxella Viable bacterial count after culture [colonies] 1.00.E+05 1.26.E+05 1.58.E+05 2.00.E+05 2.00.E+05 osloensis Increase ratio(*3) before and after antimicrobial test 5.0 6.3 7.9 10.0 10.0 Bacteriostatic activity(*1) 2.3 (2.3) 2.2 2.1 2.0 2.0 Retention of bacteriostatic activity after 10 times 100 (100) 100 100 99 100 of washing [%](*1) Bactericidal activity(*1) 0.7 (0.7) 0.8 0.9 1.0 1.0 Retention of bactericidal activity after 10 times 100 (100) 100 100 91 97 of washing(*1) Comp. Comp. Ex. 6 Ex. 7 Ex. 8 Ex. 1 Ex. 2 Raw materials of fibers POM-4 POM-1 PLA PET POM-5 (core)/ (core)/ POM-4 POM-4 (sheath) (sheath) Oxyethylene content in polyacetal copolymer [mol %] 4.7 0.4/4.7 /4.7 5.7 Melting point of polyacetal copolymer [ C.] 155 170/155 /155 147 Draw temperature [ C.] 125 130 130 125 Draw ratio 5.2 5.2 Monofilament fineness [dtex] 42 8 8 2 42 Orientation factor of fibers [%] 63 85 84 72 Addition of antimicrobial agent No No No No No Antimicrobial test Staphylococcus Viable bacterial count after culture [colonies] 5.01.E+04 3.16.E+04 3.16.E+04 7.94.E+04 aureus Increase ratio(*3) before and after antimicrobial test 2.5 1.6 1.6 4.0 Bacteriostatic activity(*1) 2.2 2.4 2.4 0.6 2.0 Retention of bacteriostatic activity after 10 times 92 99 98 93 82 of washing [%](*1) Antimicrobial and deodorant finished certification(*2) X X Bactericidal activity(*1) 0.4 0.2 0.2 0.6 Retention of bactericidal activity after 10 times 91 100 100 89 of washing(*1) Moraxella Viable bacterial count after culture [colonies] 3.16.E+05 2.00.E+05 2.00.E+05 6.31.E+05 osloensis Increase ratio(*3) before and after antimicrobial test 15.8 10.0 10.0 31.6 Bacteriostatic activity(*1) 1.8 2.0 2.0 0.7 1.5 Retention of bacteriostatic activity after 10 times 89 99 98 91 83 of washing [%](*1) Bactericidal activity(*1) 1.2 1.0 1.0 1.5 Retention of bactericidal activity after 10 times 88 98 97 81 of washing(*1) *(1)The numbers in parenthesis indicate results of evaluation as nonwoven fabrics. The numbers without parenthesis indicate results of fiber samples simply bundled. *(2) and X indicate that the product corresponded and did not correspond, respectively, to the SEK mark (blue: antimicrobial and deodorant finished) certified by Japan Textile Evaluation Technology Council. *(3)Increase ratio before and after antimicrobial test = viable bacterial count after culture/viable bacterial count immediately after inoculation Bacteriostatic activity = {log(viable bacterial count after culture in standard cotton cloth) log(viable bacterial count immediately after inoculation on standard cotton cloth)} {log(viable bacterial count after culture in measurement sample) log(viable bacterial count immediately after inoculation on measurement sample)} Bactericidal activity = log(viable bacterial count immediately after inoculation on standard cotton cloth) log(viable bacterial count after culture in measurement sample)