POLYCARBONATE FIBERS, FIBER STRUCTURE AND RESIN COMPOSITE BODY

Abstract

Provided are a polycarbonate fiber having a specific orientation degree and/or a specific birefringence value, a fiber structure as well as a resin composite body. The polycarbonate fiber may have an orientation degree (ft) of lower than 0.70, the orientation degree (ft) being defined by the following formula: ft=1−(1.0/C).sup.2, C: obtained sonic velocity (km/sec), and may have a birefringence value of 0.04 or lower. The polycarbonate fiber may comprise a polycarbonate resin having a number-average molecular weight (Mn) of from 12000 to 40000 and/or a weight-average molecular weight (Mw) of from 25000 to 80000.

Claims

1. A polycarbonate fiber having an orientation degree (ft) of lower than 0.70, the orientation degree (ft) being defined by the following formula:
ft=1−(1.0/C).sup.2 C: obtained sonic velocity (km/scc).

2. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber has a birefringence value of 0.040 or lower.

3. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber comprises a polycarbonate resin having a number-average molecular weight (Mn) of from 12000 to 40000, a weight-average molecular weight (Mw) of from 25000 to 80000, or both.

4. The polycarbonate fiber according to claim 3, wherein the polycarbonate fiber has a molecular weight distribution (Mw/Mn) of from 2.0 to 4.0.

5. A polycarbonate fiber having a birefringence value of 0.040 or lower, wherein the polycarbonate fiber comprising a polycarbonate resin having a number-average molecular weight (Mn) of from 12000 to 40000 and/or a weight-average molecular weight (Mw) of from 25000 to 80000.

6. The polycarbonate fiber according to claim 5, wherein the polycarbonate fiber has a molecular weight distribution (Mw/Mn) of from 2.0 to 4.0.

7. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber has an elastic modulus of 30 cN/dtex or lower.

8. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber has a coefficient of variation in a fiber diameter of 15% or lower.

9. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber has a single fiber fineness of 10 dtex or smaller.

10. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber has an elongation at break of 20% or higher.

11. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber comprises a polycarbonate resin including bisphenol-A units at a proportion (mol %) of 65% or higher based on a total amount of monomer units in the polycarbonate resin.

12. The polycarbonate fiber according to claim 1, wherein the polycarbonate fiber comprises a phosphorus-based flame retardant.

13. The polycarbonate fiber according to claim 12, wherein the polycarbonate fiber comprises at least one phosphorus-based flame retardant selected from a group consisting of a phosphoric acid ester-based flame retardant, a phosphoric acid salt-based flame retardant, and a phosphazene-based flame retardant.

14. A fiber structure comprising polycarbonate fibers as recited in claim 1.

15. A fiber structure comprising polycarbonate fibers as recited in claim 5.

16. The fiber structure according to claim 14, wherein the fiber structure is commingled fibers, a woven fabric, or a non-woven fabric.

17. A method for producing polycarbonate fibers, the method comprising: melt-kneading a polycarbonate resin at a high temperature of 305° C. or higher to give a molten polymer; discharging the molten polymer through a spinning nozzle at a predetermined rate to give as-spun fibers; and winding the as-spun fibers at a predetermined winding speed.

Description

EXAMPLES

[0100] Hereinafter, the present invention will be described in more detail with reference to Examples which are not to be construed as limiting the scope of the present invention. In the following Examples, various physical properties were determined in the following manners.

[0101] Molecular Weight Distribution (Mw/Mn)

[0102] A molecular weight distribution of each sample was measured by using the gel permeation chromatography (GPC) available from SHODEX with GPC101 (polystyrene conversion). After dissolving each sample in tetrahydrofuran as a solvent to have a concentration of 0.2 mass %, the solution was filtered and measured. The molecular weight distribution (Mw/Mn) was calculated from a ratio of the measured weight-average molecular weight (Mw) to the measured number-average molecular weight (Mn).

[0103] Orientation Degree

[0104] An overall molecular orientation was determined from a sonic velocity. The sonic velocity was measured using Rheovibron DDV-5-B. A bundle of fibers with 50-cm long was fixed to the device, applying a tension with a load of 0.1 g/dtex. A sonic pulse was transmitted from a sound source to a detector to measure a propagation time at each of points 50 cm, 40 cm, 30 cm, 20 cm, and 10 cm away from the sound source. The sonic velocity was calculated from a relation between distance and propagation time (n=5).

[0105] After the sonic velocity which indicates the orientation degree of the whole molecules was calculated, the orientation degree ft was calculated by the following formula:

ft=1−(1.0/C).sup.2

C: obtained sonic velocity (km/sec).

[0106] Birefringence Value

[0107] Using a polarizing microscope “BX53” available from Olympus Corporation, which included a Berek compensator, a retardation was measured under a light source with λ=546.1 nm (e-line), and a birefringence value was calculated from the retardation by the following formula:

Δn=R/d

Δn: birefringence value, R: retardation (nm), d: fiber thickness (nm).

[0108] Tenacity and Elastic Modulus (cN/dtex)

[0109] In accordance with the JIS L1013 test method, a preconditioned yarn was prepared for each sample, and a tenacity of each sample having a sample length of 20 cm was measured at room temperature (25° C.) under a condition of an initial load of 0.18 cN/dtex and a tensioning speed of 10 cm/min. An average of 10 samples was adopted. A fiber fineness (dtex) of each sample was measured by a mass method.

[0110] Dry-Heat Shrinkage Percentage (%) Under No Tension

[0111] A fiber cut to a length of 10 cm or a fabric comprising fibers and cut to a size of 10-cm square was placed in a thermostatic air chamber maintained at 140° C. After retainment for 30 minutes with the ends of the fiber or fabric unfixed, a fiber length or a fabric length (X cm) was measured, and a dry-heat shrinkage percentage was calculated by the following formula:

Dry-heat shrinkage percentage (%)={(10−X)/10}×100

[0112] Glass Transition Temperature Tg (° C.)

[0113] A glass transition temperature of a fiber was determined using a differential scanning calorimeter “TA3000-DSC” produced by Mettler. The glass transition temperature was determined as an inflection point of a DSC chart where the fiber was subjected to heating to a temperature of 350° C. at a heating rate of 10° C./min in a nitrogen atmosphere.

[0114] Limiting oxygen index (LOI) Value of Fiber

[0115] In accordance with the JIS K7201 test method, each sample having a sample length of 18 cm was prepared by braiding fibers. When fire was set at an upper end of each sample, a minimum oxygen concentration was determined in order for the sample to continuously burn for a burning time of 3 minutes or longer or for the sample to continuously burn over a burned length of 5 cm or longer after ignition. An average of 3 measurements was adopted.

[0116] Evaluation of Spinnability

[0117] Spinnability of fibers was evaluated on the basis of the number of fiber breakage in a process of spinning and fiberizing 50 kg of a resin in accordance with the following criteria:

[0118] Good: fiber breakage occurred 0 to 3 times per 50 kg,

[0119] Moderate: fiber breakage occurred 4 to 7 times per 50 kg, and

[0120] Poor: fiber breakage occurred 8 times or more per 50 kg.

Example 1

[0121] A polycarbonate resin with Mw: 52300, Mn: 17300, and Mw/Mn 3.0 was used. The polycarbonate resin contained bisphenol-A-bis(diphenyl phosphate) as a flame retardant at a concentration of 40 ppm in terms of phosphorus and had an LOI value of 34. The resin was melt-extruded using a twin-screw extruder and was discharged through a round-hole nozzle having 100 holes (0.2 mm in diameter) at a spinning temperature of 320° C. With a ratio of a discharge speed to a winding speed (i.e., drafting ratio) adjusted to 143, as-spun fibers were wound at a winding speed of about 1500 m/min. The as-spun fibers had a single fiber fineness of 2.2 dtex and a glass transition temperature Tg of 145° C. The obtained fibers were evaluated, and Table 1 shows the evaluation results.

Example 2

[0122] A polycarbonate resin with Mw: 52300, Mn: 17300, and Mw/Mn=3.0 was used. The polycarbonate resin contained bisphenol-A-bis(diphenyl phosphate) as a flame retardant at a concentration of 40 ppm in terms of phosphorus and had an LOI value of 34. The resin was melt-extruded using a twin-screw extruder and was discharged through a round-hole nozzle having 100 holes (0.2 mm in diameter) at a spinning temperature of 320° C. With a ratio of a discharge speed to a winding speed (i.e., drafting ratio) adjusted to 95, as-spun fibers were wound at a winding speed of about 1000 m/min. The as-spun fibers had a single fiber fineness of 3.3 dtex and a glass transition temperature Tg of 145° C. The obtained fibers were evaluated, and Table 1 shows the evaluation results.

Example 3

[0123] A polycarbonate resin with Mw: 52300, Mn: 17300, and Mw/Mn=3.0 was used. The polycarbonate resin contained bisphenol-A-bis(diphenyl phosphate) as a flame retardant at a concentration of 40 ppm in terms of phosphorus and had an LOI value of 34. The resin was melt-extruded using a twin-screw extruder and was discharged through a round-hole nozzle having 100 holes (0.2 mm in diameter) at a spinning temperature of 320° C. With a ratio of a discharge speed to a winding speed (i.e., drafting ratio) adjusted to 63, as-spun fibers were wound at a winding speed of about 666 m/min. The as-spun fibers had a single fiber fineness of 4.9 dtex and a glass transition temperature Tg of 145° C. The obtained fibers were evaluated, and Table 1 shows the evaluation results.

Example 4

[0124] A polycarbonate resin with Mw: 49800, Mn: 17000, and Mw/Mn=2.9 was used. The polycarbonate resin had an LOI value of 26. The resin was melt-extruded using a twin-screw extruder and was discharged through a round-hole nozzle having 100 holes (0.2 mm in diameter) at a spinning temperature of 320° C. With a ratio of a discharge speed to a winding speed (i.e., drafting ratio) adjusted to 63, as-spun fibers were wound at a winding speed of about 666 m/min. The as-spun fibers had a single fiber fineness of 4.9 dtex and a glass transition temperature Tg of 150° C. The obtained fibers were evaluated, and Table 1 shows the evaluation results.

Comparative Example 1

[0125] A polycarbonate resin with Mw: 135000, Mn: 56000, and Mw/Mn=2.4 was used. The polycarbonate resin had an LOT value of 26. The resin was melt-extruded using a twin-screw extruder and was discharged through a round-hole nozzle having 100 holes (0.2 mm in diameter) at a spinning temperature of 290° C. With a ratio of a discharge speed to a winding speed (i.e., drafting ratio) adjusted to 63, as-spun fibers were wound at a winding speed of about 666 m/min. The as-spun fibers had a single fiber fineness of 4.9 dtex. The obtained fibers were evaluated, and Table 1 shows the evaluation results.

Comparative Example 2

[0126] A polycarbonate resin with Mw: 49800, Mn: 17000, and Mw/Mn=2.9 was used. The polycarbonate resin had an LOT value of 26. The resin was melt-extruded using a twin-screw extruder and was discharged through a round-hole nozzle having 100 holes (0.2 mm in diameter) at a spinning temperature of 290° C. With a ratio of a discharge speed to a winding speed (i.e., drafting ratio) adjusted to 63, as-spun fibers were wound at a winding speed of about 666 in/min. The as-spun fibers had a single fiber fineness of 4.9 dtex and a glass transition temperature Tg of 150° C. The obtained fibers were evaluated, and Table 1 shows the evaluation results.

Comparative Example 3

[0127] A polycarbonate resin with Mw: 90000, Mn: 28000, and Mw/Mn=3.2 was used. The polycarbonate resin contained bisphenol-A-bis(diphenyl phosphate) as a flame retardant at a concentration of 80 ppm in terms of phosphorus and had an LOI value of 37. The resin was melt-extruded using a twin-screw extruder and was discharged through a round-hole nozzle having 100 holes (0.2 mm in diameter) at a spinning temperature of 300° C. With a ratio of a discharge speed to a winding speed (i.e., drafting ratio) adjusted to 63, as-spun fibers were wound at a winding speed of about 666 m/min. The as-spun fibers had a single fiber fineness of 4.9 dtex. The obtained fibers were evaluated, and Table 1 shows the evaluation results.

TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Com. Ex. 1 Com. Ex. 2 Com. Ex. 3 Resin Molecular weight Mw: 52300 Mw: 52300 Mw: 52300 Mw: 49800 Mw: 135000 Mw: 49800 Mw: 90000 Mn: 17300 Mn: 17300 Mn: 17300 Mn: 17000 Mn: 56000 Mn: 17000 Mn: 28000 Molecular weight 3.0 3.0 3.0 2.9 2.4 2.9 3.2 distribution (Mw/Mn) MFR (g/10 min) 13 13 13 15 3 15 5 Melt viscosity (poise) 1528 1528 1528 1922 5800 1922 3720 at 320° C., 1000 s.sup.−1 Flame retardant Bisphenol-A- Bisphenol-A- Bisphenol-A- — — — Bisphenol-A- bis(diphenyl bis(diphenyl bis(diphenyl bis(diphenyl phosphate) phosphate) phosphate) phosphate) Spinning Spinning temperature (° C.) 320 320 320 320 290 290 300 Discharge speed (m/min) 10.5 10.5 10.5 10.5 10.5 10.5 10.5 Winding speed (m/min) 1500 1000 666 666 666 666 666 Drafting ratio 143 95 63 63 63 63 63 Spinnability Good Good Good Good Poor Good Poor Fiber Single fiber fineness (dtex) 2.2 3.3 4.9 4.9 4.9 4.9 4.9 Fiber diameter (μm) 15.0 18.4 22.4 22.4 22.4 22.4 22.4 CV (%) in fiber diameter 3.3 3.6 4.0 4.0 16.5 6.8 7.2 Orientation degree 0.57 0.56 0.52 0.52 0.71 0.75 0.70 Birefringence value 0.008 0.007 0.006 0.006 0.042 0.045 0.043 Tenacity (cN/dtex) 1.8 1.53 1.2 1.1 2.5 2.1 2.2 Elongation (%) 106 147 160 165 39 30 37 Elastic Modulus (cN/dtex) 21.5 20.2 19.5 19.3 32.5 31.0 33.6 LOI 24.0 24.0 24.0 24.6 23.8 24.0 28.0 Dry-heat shrinkage 6.5 4.0 1.3 1.3 21.0 13.0 24.0 percentage (%) under no tension

[0128] As shown in Table 1, in all of Examples 1 to 4, the polycarbonate fibers can have orientation degrees and birefringence values controlled within predetermined ranges and have reduced dry-heat shrinkage percentages, thanks to melt spinning at high temperature. Therefore, it is possible to suppress defects such as resin spots, warps and/or twists in the melt-molded bodies. Even if the fiber diameters are small, these Examples can have reduced coefficients of variation in the fiber diameters and have good handling properties. The obtained fibers have sufficient tenacity for practical applications and have high elongation as well as improved flame retardancy.

[0129] Comparative Example 1, on the other hand, reveals that the polycarbonate resin having a high molecular weight and thus poor melt spinnability is unable to obtain fibers having a controlled orientation degree or a controlled birefringence value, and the obtained fiber has a high dry-heat shrinkage percentage. Therefore, it is difficult to suppress defects such as resin spots, warps and/or twists in a melt-molded body. In Comparative Example 1, fibers are deteriorated in handleability because of high coefficient of variation in the fiber diameter, resulting in fiber unevenness.

[0130] In Comparative Example 2, although the polycarbonate resin has good melt spinnability, the obtained fiber has an orientation degree and a birefringence value outside the ranges as specified in the present invention as well as a high dry-heat shrinkage percentage. Therefore, it is difficult to suppress defects such as resin spots, warps and/or twists in a melt-molded body. As compared with the Examples, the fibers in Comparative Example 2 have a high coefficient of variation in the fiber diameter, thus deteriorated in handleability in comparison with Examples.

[0131] In Comparative Example 3, the polycarbonate resin has poor melt spinnability, and the obtained fiber has an orientation degree and a birefringence value outside the ranges as specified in the present invention as well as has a high dry-heat shrinkage percentage. Therefore, it is difficult to suppress defects such as resin spots, warps and/or twists in a melt-molded body. As compared with the Examples, the fibers in Comparative Example 3 also have a high coefficient of variation in the fiber diameter, thus deteriorated in handleability in comparison with Examples.

INDUSTRIAL APPLICABILITY

[0132] A fiber structure comprising polycarbonate fibers according to the present invention can be suitably used in various applications. Further, polycarbonate fibers in such a fiber structure can be melted to form a matrix of a resin composite body. Such a fiber structure as well as a resin composite body may be highly effectively used in various fields, including general industrial material fields, electrical and electronic fields, civil engineering and construction fields, aircraft, automobile, railroad, and vessel fields, agricultural material fields, optical material fields, medical material fields, etc.

[0133] Although the present invention has been described in terms of the preferred Examples thereof, those skilled in the art would readily arrive at various changes and modifications in view of the present specification without departing from the scope of the invention. Accordingly, such changes and modifications are included within the scope of the present invention defined by the appended claims.