Highly water repellent conjugate fiber and high bulk nonwoven fabric using the same

Abstract

A fiber that can exhibit both excellent antistatic properties and high water repellency, and a high bulk nonwoven fabric with a good texture that exhibits high water repellency. More specifically, a highly water repellent fiber that is a conjugate fiber having a plurality of thermoplastic resins as the primary component thereof and having a fiber treatment agent comprising at least Component (A) and Component (B) below deposited thereon at 0.1 to 1.0 wt % in relation to the weight of the fiber, with Component (A) accounting for 75 to 97 wt % and Component (B) accounting for 25 to 3 wt % of the fiber treatment agent: Component (A): polysiloxane Component (B): alkane sulfonate metal salt.

Claims

1. A highly water repellent and highly antistatic fiber that is a treated conjugate fiber comprising: a conjugate fiber having a plurality of thermoplastic resins as the primary component thereof; and a fiber treatment agent that is provided on an external surface of the conjugate fiber, the fiber treatment agent comprising at least Component (A) and Component (B) below and is present in an amount of 0.1 to 1.0 wt % in relation to the weight of the conjugate fiber, with Component (A) accounting for 75 wt % and Component (B) accounting for 25 wt % of the components of the fiber treatment agent remaining when water is removed from the fiber treatment as a whole: Component (A): polydimethylsiloxane Component (B): alkane sulfonate metal salt, wherein the treated conjugate fiber is obtained by depositing the fiber treatment agent on the external surface of the conjugate fiber, and wherein the treated conjugated fiber has a voltage value of static electricity that is less than 100V when measured after being subjected to carding at 20 C. and 45% relative humidity.

2. The highly water repellent and highly antistatic fiber according to claim 1, wherein at least one of said plurality of thermoplastic resins is a polyolefin polymer or polyester polymer.

3. A high bulk nonwoven fabric fabricated by a process including a carding step using the highly water repellent and highly antistatic fiber according to claim 1.

Description

EXAMPLES

(1) Next the present invention will be explained in detail using examples and comparative examples, but the present invention is not limited the examples described below. The definitions of terms and the measurement methods used in the present description, and particularly in the examples and comparative examples, are as follows.

(2) (1) Deposited Amount of Treatment Agent

(3) This value shows the ratio of treatment agent deposited on the fibers in relation to the weight of the fibers, and is calculated by the extraction method. (Units: wt %).

(4) A fiber web was fabricated by passing 50 g of sample short fibers through a miniature roller carding machine, 2 g were removed from the fiber web, and the measurement was performed using a high speed resin residue extractor. For the extraction medium, 25 mL of 2-propanol was used. The amount of deposition was calculated using the following formula.
Amount of deposition (wt %)=(extracted amount (g)/2)100
(2) Antistatic Properties

(5) This shows the voltage value of static electricity produced in the carding process. (Units: V (volts))

(6) At 20 C. in an atmosphere with 45% RH, a fiber web was fabricated by passing 50 g of sample short fibers through a 500 mm wide miniature roller carding machine at an exit roller speed of 7 m/min, and the voltage of static electricity generated by the fiber web during passage between the carding machine exit and the collection drum was measured. It was concluded that if the voltage is less than 100 V, the static electricity could be sufficiently controlled when the fiber is processed, and the processing could be carried out smoothly.

(7) (3) Mass Per Unit Area

(8) This shows the weight per unit area in a nonwoven fabric and fiber web, and it is calculated from the weight of a nonwoven fabric or fiber web cut to a specified area. (Units: g/m.sup.2)

(9) A sample of nonwoven fabric cut to 250 mm250 mm was weighed on an electronic pan balance, and the numerical value was multiplied 16 times to arrive at the mass per unit area.

(10) (4) Bulk (Specific Volume and Porosity)

(11) (i) Specific volume shows the weight per unit volume of a nonwoven fabric, and it is calculated from the measured mass per unit area and measured thickness. (Units: cm.sup.3/g)

(12) The thickness of the nonwoven fabric was measured using a thickness measurement device under conditions of a load of 3.5 g/cm.sup.2 and a rate of 2 mm/sec, and the specific volume was calculated using the numerical value for thickness (mm) and mass per unit area (g/m.sup.2) according to the following formula.
Specific volume=t/w1000
t: thickness of the sample of nonwoven fabric (mm)
w: mass per unit area (g/m.sup.2)
(ii) Porosity: This measures the ratio occupied by voids per unit volume of nonwoven fabric, and it is calculated from the mass per unit area and thickness of the nonwoven fabric, and the specific gravity of the constituent fibers. (Units: %)

(13) The thickness of the nonwoven fabric was measured using a thickness measurement device under conditions of a load of 3.5 g/cm.sup.2 and a rate of 2 mm/sec, and the porosity was calculated using the numerical value for thickness (m), mass per unit area (g/m.sup.2) and the specific gravity of the constituent fibers (g/cm.sup.3) according to the following formula.
Porosity={(tw/)/t}100
t: thickness of the sample of nonwoven fabric (m)
w: mass per unit area of the sample of nonwoven fabric (g/m.sup.2)
: specific gravity of constituent fibers (g/cm.sup.3)
(5) Water Repellency

(14) This shows the water resistance of the nonwoven fabric. (Units: mm)

(15) A 150 mm150 mm sample of nonwoven fabric was cut out and measured at rate of increase of 10 cm/min in accordance with JIS L1092-A (low water pressure method). The higher the water resistance value is, the better the water repellency. It was concluded that if the water resistance value is 40 mm or more, the water repellency of the conjugate fiber serving as the material is sufficient, and a highly water repellent nonwoven fabric that is satisfactory as a commercial product has been provided.

(16) (6) Softness

(17) The visual uniformity, softness to the touch, stiffness, puffiness, etc., of the nonwoven fabric were evaluated.

(18) A 150 mm150 mm sample of nonwoven fabric was cut out, and evaluated in an organoleptic test by a five-member panel.

(19) The test was scored on a three-step scale:

(20) : Judged good by all five members

(21) : Judged poor by 1 to 2 members

(22) x: Judged poor by four or more members

Example 1

(23) A 50%/50% by weight sheath-core conjugate fiber was spun using a 350-nozzle sheath-core conjugate spinneret at a temperature of 220 to 280 C. with a pull-up rate of 800 m/min by using crystalline polypropylene with a melt mass flow rate (conditions: 230 C., load of 21.18 N) of 15 g/10 min, and a melting point of 162 C. as the core component, and a high density polyethylene with a density of 0.96 g/cm.sup.3, melt index (conditions: 190 C., load of 21.18 N) of 16 g/10 min, and a melting point of 131 C. as the sheath component. After spinning, the fibers were drawn to 4 times in a drawing ratio using a hot roll at 90 C., and fiber treatment agent 1 shown in Table 1 was deposited during the drawing process in the form of an aqueous emulsion containing 10 wt % active components using an oiling roll. The fiber whereon the fiber treatment agent had been deposited was mechanically crimped, and after drying and cutting, sample short fibers 51 mm long with a fineness of 2.2 dtex were obtained.

(24) The amount of deposition and antistatic properties of the resulting sample short fibers were measured using measurement methods (1) and (2) above. The results are shown in Table 2.

(25) Additionally, 50 g of the resulting sample short fibers were made into fiber webs by carding using a miniature roller carding machine. The fiber webs were passed through a hot air circulation heat treatment processing machine under conditions of a setting temperature of 130 C., an average hot air flow rate of 0.8 m/sec and a processing time of 12 sec to make a sample nonwoven fabric by the hot-air bonding method.

Example 2

(26) Sample short fibers were obtained in the same manner as in Example 1 except that fiber treatment agent 2 shown in Table 1 was used in the drawing step. The amount of deposition and antistatic properties of the resulting sample short fibers were measured using measurement methods (1) and (2) above. The results are shown in Table 2.

(27) A sample nonwoven fabric was also obtained in the same manner as in Example 1.

Example 3

(28) Sample short fibers were obtained in the same manner as in Example 1 except that fiber treatment agent 3 shown in Table 1 was used in the drawing step. The amount of deposition and antistatic properties of the resulting sample short fibers were measured using measurement methods (1) and (2) above. The results are shown in Table 2.

(29) A sample nonwoven fabric was also obtained in the same manner as in Example 1.

Comparative Example 1

(30) Sample short fibers were obtained in the same manner as in Example 1 except that fiber treatment agent 4 shown in Table 1 was used in the drawing step. The amount of deposition and antistatic properties of the resulting sample short fibers were measured using measurement methods (1) and (2) above. The results are shown in Table 2.

(31) A sample nonwoven fabric was also obtained in the same manner as in Example 1.

Comparative Example 2

(32) Crystalline polypropylene with a melt mass flow rate of 15 g/10 min (conditions: 230 C., load of 21.18 N), and a melting point of 162 C. was spun using a 350-nozzle spinneret at a temperature of 260 to 280 C. with a pull-up rate of 800 m/min. In the spinning process, treatment agent 5 shown in Table 1 was deposited at a target amount of deposition of 0.6 wt % in the form of an aqueous emulsion containing 5 wt % active components using an oiling roll. After spinning, the fibers were drawn to 4 times in a drawing ratio using a hot roll at 90 C., and fiber treatment agent 6 shown in Table 1 was additionally deposited during the drawing process at a target amount of deposition of 0.1 wt % in the form of an aqueous emulsion containing 10 wt % active components using an oiling roll. The fiber whereon the fiber treatment agent had been deposited was mechanically crimped, and after drying and cutting, sample short fibers 51 mm long with a fineness of 2.2 dtex were obtained.

(33) The amount of deposition and antistatic properties of the resulting sample short fibers were measured using measurement methods (1) and (2) above. The results are shown in Table 2.

(34) Additionally, 50 g of the resulting sample short fibers were made into fiber webs by carding using a miniature roller carding machine. The fiber webs were passed between two heated rolls, one roll having a convex member engraved thereon, and partial thermo-compression bonding was performed thereby to obtain sample nonwoven fabric. The conditions in this hot roll bonding method were a surface temperature of 154 C., rotation rate of 0.6 m/min, linear load of 196 N/cm, and compression bonding area ratio of 25%.

Comparative Example 3

(35) Sample short fibers were obtained in the same manner as in Example 1 except that fiber treatment agent 7 shown in Table 1 was used in the drawing step.

Comparative Example 4

(36) A nonwoven fabric with a compression bonding area ratio of 14% and a filament fineness of 2.3 dtex that was obtained by the spunbond method from crystalline polypropylene having a melting point of 160 C. was used as the sample nonwoven fabric.

(37) Using methods (3) to (6) above, the mass per unit area, bulk, water repellency, and softness were evaluated in each of the sample nonwoven fabrics obtained as described above. The results are shown in Table 2.

(38) TABLE-US-00001 TABLE 1 (Units: wt % in active component) Treatment agent No. Treatment agent component 1 2 3 4 5 6 7 Polydimethylsiloxane*.sup.1 75 90 97 65 95 35 Sodium alkane sulfonate*.sup.2 25 10 3 35 Phosphate alcohol ester 100 5 Ethylene oxide-added (20) 35 stearyl amine Cetyl phosphate ester K salt 30 *.sup.1DOW CORNING TORAY SH 200 C FLUID from Dow Corning Toray Silicone Co., Ltd. *.sup.2HOSTAPUR SAS from Clariant (Japan) K.K.

(39) TABLE-US-00002 TABLE 2 Comparative Example Example 1 2 3 1 2 3 4 Treatment agent No. 1 2 3 4 5, 6 7 Amount of deposition (%) 0.15 0.35 1.0 0.35 0.7 0.4 0 Antistatic properties (V) 30 30 80 30 800 50 Mass per unit area of 25 25 25 25 25 25 25 nonwoven fabric (g/m.sup.2) Bulk Specific volume 50 50 50 50 10 50 10 (cm.sup.3/g) Porosity (%) 98 98 98 98 89 98 89 Water repellency (mm) 60 70 80 15 70 25 80 Softness x x

INDUSTRIAL APPLICABILITY

(40) The highly water repellent fiber of the present invention has excellent antistatic properties, so no trouble caused by static electricity occurs in the step of processing the same into a nonwoven fabric. A nonwoven fabric fabricated using the highly water repellent fiber of the present invention has high bulk and excellent water repellency. Therefore, the nonwoven fabric can be most suitably used for a material that prevents getting wet or water impermeable sheets in disposable diapers, sanitary napkins, absorbent pads, etc.