Carbon-fiber-precursor acrylic fiber bundle with oil composition adhering thereto, process for producing the same, oil composition for carbon-fiber-precursor acrylic fiber, and oil composition dispersion for carbon-fiber-precursor acrylic fiber

Abstract

The present invention relates to a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto, wherein the oil composition comprises an amino-modified silicone, an aromatic ester compound (1) having a structure represented by the following formula (1), and an aromatic ester compound (2) having a structure represented by the following formula (2), the amino-modified silicone, the aromatic ester compound (1), and the aromatic ester compound (2) meet the specific requirements, the process for producing the same, an oil composition carbon-fiber-precursor acrylic fiber, and an oil composition dispersion for carbon-fiber-precursor acrylic fiber. ##STR00001##

Claims

1. A carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto, wherein: the oil composition comprises an amino-modified silicone, an aromatic ester compound (1) having a structure of formula (1): ##STR00013## and an aromatic ester compound (2) having a structure of formula (2): ##STR00014## an adhesion amount of the amino-modified silicone is from 0.01 to 0.2% by mass relative to a mass of the dry fiber, a total adhesion amount of the aromatic ester compound (1) and the aromatic ester compound (2) is from 0.4 to 1.2% by mass relative to the mass of the dry fiber, a ratio of the adhesion amounts of the aromatic ester compound (2) to the aromatic ester compound (1) is from 0.25 to 6.5, R.sup.1 and R.sup.2 are each independently a hydrocarbon group having 7 to 21 carbon atoms, m and n are each independently an integer of from 1 to 5, and R.sup.3, R.sup.4, and R.sup.5 are each independently a hydrocarbon group having 8 to 10 carbon atoms.

2. The fiber bundle according to claim 1, wherein the amino-modified silicone is an amino-modified silicone having a structure of formula (3): ##STR00015## wherein o is an integer of from 5 to 300, and p is an integer of from 1 to 5.

3. The fiber bundle according to claim 1, wherein the amino-modified silicone has a kinematic viscosity of from 50 to 500 mm.sup.2/s at 25 C.

4. The fiber bundle according to claim 1, wherein a block copolymerization polyether comprising a propylene oxide unit and an ethylene oxide unit and having a structure of formula (4):
HOC.sub.2H.sub.4O.sub.xC.sub.3H.sub.6O.sub.yC.sub.2H.sub.4O.sub.zH(4) is further adhered in a quantity of from 5 to 70 parts by mass relative to 100 parts by mass representing a total adhesion amount of the aromatic ester compound (1), the aromatic ester compound (2), and the amino-modified silicone to the dry fiber, wherein x, y, and z are each independently an integer of from 1 to 200.

5. The fiber bundle according to claim 1, wherein the amino-modified silicone has a kinematic viscosity of from 50 to 300 mm.sup.2/s at 25 C.

6. An oil composition comprising an amino-modified silicone, an aromatic ester compound (1) having a structure of formula (1): ##STR00016## and an aromatic ester compound (2) having a structure of formula (2): ##STR00017## wherein: a content of the amino-modified silicone is from 1 to 25 parts by mass relative to 100 parts by mass of a total quantity of the aromatic ester compound (1) and the aromatic ester compound (2), and a mass ratio of the aromatic ester compound (2) to the aromatic ester compound (1) is from 0.25 to 6.5, R.sup.1 and R.sup.2 are each independently a hydrocarbon group having 7 to 21 carbon atoms, m and n are each independently an integer of from 1 to 5, and R.sup.3, R.sup.4, and R.sup.5 are each independently a hydrocarbon group having 8 to 10 carbon atoms.

7. The oil composition according to claim 6, wherein the amino-modified silicone is an amino-modified silicone having a structure of formula (3): ##STR00018## wherein o is an integer of from 5 to 300, and p is an integer of from 1 to 5.

8. The oil composition according to claim 6, wherein the amino-modified silicone has a kinematic viscosity of from 50 to 500 mm.sup.2/s at 25 C.

9. The oil composition according to claim 6, further comprising a block copolymerization polyether comprising a propylene oxide unit and an ethylene oxide unit and having a structure of formula (4):
HOC.sub.2H.sub.4O.sub.xC.sub.3H.sub.6O.sub.yC.sub.2H.sub.4O.sub.zH(4) in a quantity of from 10 to 50 parts by mass relative to 100 parts by mass of a total quantity of the amino-modified silicone, the aromatic ester compound (1), and the aromatic ester compound (2), wherein x, y, and z are each independently an integer of from 1 to 200.

10. An oil composition dispersion, wherein the oil composition according to claim 6 is dispersed in water or a solvent.

11. The oil composition dispersion according to claim 10, wherein the oil composition forms micelles with an average particle size of from 0.01 to 0.50 m.

12. A process for producing a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto, comprising: applying an oil composition dispersion obtained by dispersing the oil composition according to claim 6 in water or a solvent, forming micelles with an average particle size of from 0.01 to 0.50, to a carbon-fiber-precursor acrylic fiber bundle in a water-swelled state, and performing drying densification of the carbon-fiber-precursor acrylic fiber bundle.

13. The oil composition according to claim 6, wherein the amino-modified silicone has a kinematic viscosity of from 50 to 300 mm.sup.2/s at 25 C.

Description

EXAMPLES

(1) The present invention is described concretely with the examples below.

(2) However, the present invention is not limited by these Examples. The components and various measuring methods and assessment methods used in these Examples are as follows:

(3) <Components>

(4) (Aromatic Ester Compounds) A-1: Polyoxyethylene bisphenol A dilaurate (manufactured by Kao Corporation; trade name, Exceparl BP-DL) having a structure represented by the above-mentioned formula (1), wherein both R.sup.1 and R.sup.2 are a lauryl group, and both m and n are about 1. A-2: Tri-isodecyl trimellitate (manufactured by Kao Corporation; trade name, TRIMEX T-10) having a structure represented by the above-mentioned formula (2), wherein all of R.sup.3 to R.sup.5 are an isodecyl group. A-3: Pentaerythritol tetrastearate (manufactured by NOF Corporation; trade name, UNISTER H-476)

(5) (Amino-Modified Silicone) B-1: Amino-modified silicone having a structure represented by the above-mentioned formula (3), wherein o is about 80, p is about 2, the kinematic viscosity is 90 mm.sup.2/s at 25 C., and the amino equivalent is 2500 g/mol (manufactured by Gelest, Inc.; trade name, AMS-132), B-2: Amino-modified silicone having a structure represented by the above-mentioned formula (3), wherein o is about 90, p is about 1, the kinematic viscosity is 110 mm.sup.2/s at 25 C., and the amino equivalent is 5000 g/mol (manufactured by Shin-Etsu Chemical Co., Ltd.; trace mane, KF-868). B-3: Amino-modified silicone having a structure represented by the above-mentioned formula (3), wherein o is about 240, p is about 3, the kinematic viscosity is 450 mm.sup.2/s at 25 C., and the amino equivalent is 5700 g/mol (manufactured by Shin-Etsu Chemical Co., Ltd.; trace mane, KF-8008). B-4: Amino-modified silicone having side chains of primary and secondary amine and having a kinematic viscosity of 10000 mm.sup.2/s at 25 C., and an amino equivalent of 7000 g/mol (manufactured by Momentive Performance Materials Japan LLC; trade name, TSF4707).

(6) (Surfactant) C-1: PO/EO block copolymerization polyether having a structure represented by the above-mentioned formula (4), wherein x is about 75, y is about 30, and z is about 75 (manufactured by BASF Japan Ltd.; trade name, PluronicPE6800). C-2: PO/EO block copolymerization polyether having a structure represented by the above-mentioned formula (4), wherein x is about 10, y is about 20, and z is about 10 (manufactured by ADEKA Corporation; trade name, ADEKA NOL L-44). C-3: Nonaethylene glycol dodecyl ether (manufactured by Nikko Chemicals Co., Ltd.; trade name, NIKKOLBL-9EX).

(7) (Compatibilizing Agent) D-1: Lauryl PEG-9 polydimethylsiloxyethyl dimethicone consisting of units represented by the above-mentioned formulae (5), (6), and (9) (manufactured by Shin-Etsu Chemical Co., Ltd.; trade name, KF-6038). D-2: Lauryl polyglyceryl-3 polydimethylsiloxyethyl dimethicone consisting of units represented by the above-mentioned formulae (5), (7), and (9) (manufactured by Shin-Etsu Chemical Co., Ltd.; trade name, KF-6105). D-3: Modified silicone consisting of units represented by the above-mentioned formulae (5) and (8) and having a random copolymer side chain of ethylene oxide and propylene oxide and an alkyl side chain (manufactured by Momentive Performance Materials Japan LLC; trade name, TSF4450).

(8) <Measurement and Evaluation>

(9) (Measurement of Adhesion Amount of Oil Agent)

(10) After applying the oil agent, drying densification and drawing were performed to obtain a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto. About 2 g of the bundle was collected and dried at 105 C. for 1 hour, and the mass of the dry fiber (w.sub.1) was measured. Subsequently, in accordance with the Soxhlet extraction method using methyl ethyl ketone, the carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto was immersed in methyl ethyl ketone at 90 C. for 8 hours to perform solvent extraction of the adhering oil composition. Then the bundle was dried at 105 C. for 1 hour, and the mass of the dry fiber (w.sub.2) was measured. The adhesion amount of the oil agent was determined by the following formula (1):
Adhesion amount of oil agent [% by mass]=(w.sub.1w.sub.2)/w.sub.1100(i)

(11) (Evaluation of Operability)

(12) The carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto was manufactured continuously for 24 hours. The operability was evaluated by the frequency of entwining of a single yarn around the conveying roller and removal thereof during manufacturing. Operability was evaluated in accordance with the following criteria:

(13) A: Number of times of removal (time/24 hours)1

(14) B: Number of times of removal (time/24 hours) 2 to 5

(15) C: Number of times of removal (time/24 hours)>5

(16) (Evaluation of Bundlability of Flameproofed Yarn)

(17) Immediately after the flameproofing step, the width of the flameproofed fiber bundle on the roll was measured with digital calipers for evaluation.

(18) (Measurement of Number of Fusions Between Single Fibers)

(19) A carbon fiber bundle was cut into 3 mm in length, dispersed in acetone, and stirred for 10 minutes. Then, the total number of single fibers and the number of fusions between single fibers (number of fusions) were counted, and the number of fusions per 100 single fibers was calculated for evaluation. The evaluation criteria are as follows.

(20) A: Number of fusions (piece/100 fibers)1

(21) B: Number of fusions (piece/100 fibers)>1

(22) (Measurement of Strand Strength)

(23) After starting the manufacture of a carbon fiber bundle, samples of the carbon fiber bundle were collected after manufacturing became constant and stable. The strand strength of the carbon fiber bundle was measured in accordance with the epoxy resin-impregnated strand testing method as stipulated in JIS R-7608. The measurement count was 10 times, and the average value was evaluated.

(24) (Measurement of Amount of Scattered Si)

(25) With respect to the measurement of the amount of scattered silicon compounds derived from the silicone compound, the change calculated from the difference between the content (A.sub.1) of silicon (Si) in the carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto and the content (A.sub.2) of Si in the flameproofed fiber bundle was defined as the amount of scattered Si and used as an index of evaluation.

(26) Specifically, each of the carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto and the flameproofed fiber bundle were finely ground with a pair of scissors to prepare samples. In a sealed crucible, 50 mg each of the samples were weighed, followed by addition of 0.25 g each of powdered NaOH and KOH, and the mixture was subjected to thermolysis in a muffle furnace at 210 C. for 150 minutes. Then the mixture was dissolved in distilled water to make 100 mL for use as the test portion. The Si content of each test portion was determined with an ICP emission spectrometer (manufactured by Thermo Electron Co., Ltd.; name of apparatus, IRIS Advantage AP), and the amount of scattered Si was calculated from the following formula (ii):
Amount of scattered Si [mg/kg]=A.sub.1A.sub.2(ii)

Example 1

(27) (Preparation of Oil Agent)

(28) A surfactant was added to an amino-modified silicone and mixed by stirring, and an aromatic ester compound was added to the mixture. To the above mixture was further added ion exchange water so that the concentration of the oil composition was 30% by mass, and the resulting mixture was emulsified by a homomixer. The average particle size of the micelles under such condition was measured using a laser diffraction/scatter type particle size distribution measuring instrument (manufactured by Horiba, Ltd.; name of apparatus, LA-910) and found to be about 3 m.

(29) Subsequently, the micelles were further dispersed with a high-pressure homogenizer until the average particle size of the micelles became 0.3 m or less to obtain an oil composition dispersion (emulsion). Then, ion-exchanged water was further added to prepare an oil agent in such a manner that the concentration of the oil composition dispersion is 1.7% by mass.

(30) Table 1 shows the types and loadings (parts by mass) of the components constituting an oil composition.

(31) (Manufacture of a Carbon-Fiber-Precursor Acrylic Fiber Bundle with an Oil Composition Adhering Thereto)

(32) The precursor fiber bundle to which the oil composition is to be adhered was prepared in the following manner. An acrylonitrile-based copolymer (composition ratio: acrylonitrile/acrylamide/methacrylic acid=96.5/2.7/0.8 (mass ratio)) was dissolved in dimethylacetamide to prepare a spinning dope. The spinning dope was discharged into a coagulation bath filled with an aqueous dimethylacetamide solution at a concentration of 60% by mass and a temperature of 35 C. through a spinning nozzle having a pore size (diameter) of 50 m and the number of holes of 50000 to obtain a coagulated yarn. The coagulated yarn was introduced into a water-washing tank to remove the solvent and drawn 5.5 times the initial length to obtain the precursor fiber bundle in a water-swollen state.

(33) The above-mentioned precursor fiber bundle in a water-swollen state was introduced into an oil agent treatment tank containing the previously prepared oil agent to apply the oil agent thereto.

(34) Then, the precursor fiber bundle which was adhered the oil agent was dried and densified with a roll having a surface temperature of 180 C. and then drawn 1.5 times the initial length with a roll having a surface temperature of 190 C. to obtain a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto.

(35) The adhesion amount of the oil agent in the obtained carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto was measured, and the operability during manufacturing was evaluated. The results are shown in Table 1.

(36) (Manufacture of Carbon Fiber Bundle)

(37) The obtained carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto was passed through a flameproofing furnace having a temperature gradient of 220 C. to 260 C. for flameproofing to form a flameproofed fiber bundle. The bundlability of the obtained flameproofed fiber bundle was evaluated, and the amount of scattered Si in the flameproofing step was measured. The results are shown in Table 1.

(38) Subsequently, the flameproofed fiber bundle was calcined in a carbonization furnace having a temperature gradient of 400 C. to 1400 C. in a nitrogen atmosphere to form a carbon fiber bundle. The number of fusions between single fibers and the strand strength of the obtained carbon fiber bundle were measured. The results are shown in Table 1.

Examples 2 to 18

(39) An oil agent was prepared, a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto and a carbon fiber bundle were manufactured, and measurements and evaluations were performed in the same manner as Example 1 except that the types and loadings of the components constituting the oil composition were changed as shown in Table 1 and 2. The results are shown in Table 1 and 2.

(40) In Examples 2 to 6, 9, and 13, the compatibilizing agent was dispersed in the amino-modified silicone in advance, and then the oil agent was prepared in the same manner as Example 1.

Comparative Examples 1 to 10

(41) An oil agent was prepared, a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto and a carbon fiber bundle were manufactured, and measurements and evaluations were performed in the same manner as Example 1 except that the types and loadings of the components constituting the oil composition were changed as shown in Table 3. The results are shown in Table 3.

(42) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 8 9 Proportion of the Aromatic ester compound A-1 17 15 13 31 31 29 29 27 27 Components of Oil [parts by mass] A-2 66 72 80 62 62 58 57 60 60 Composition Amino-modified silicone B-1 17 0 0 0 0 0 6 5 0 [parts by mass] B-2 0 13 7 7 7 13 4 4 13 B-3 0 0 0 0 0 0 4 4 0 Surfactant C-1 25 14 13 15 15 14 21 20 7 [parts by mass] C-2 25 14 7 15 15 14 21 13 7 C-3 17 14 0 15 8 14 0 0 13 Compatibilizing agent D-1 0 0 0 8 0 0 0 0 7 [parts by mass] D-2 0 1.5 0 0 0 1 0 0 0 D-3 0 0 13 0 15 0 0 0 0 Mass ratio (A-2/A-1) 3.88 4.80 6.15 2.00 2.00 2.00 1.97 2.22 2.22 Content of amino-modified silicone 20 15 8 8 8 15 16 15 15 [parts by mass] Adhesion amount of oil agent [% by mass] 1.2 0.9 1.1 1.1 1.0 1.4 1.2 1.3 1.0 Adhesion amount of amino-modified silicone 0.12 0.08 0.06 0.05 0.05 0.13 0.12 0.13 0.10 [% by mass] Adhesion amount of aromatic ester compound 0.60 0.55 0.77 0.67 0.61 0.85 0.73 0.85 0.65 (A-1 + A-2) [% by mass] Ratio of adhesion amounts (A-2/A-1) 3.88 4.80 6.15 2.00 2.00 2.00 1.97 2.22 2.22 Evaluation Operability A A A A A A A A A Flameproofing bundlability [mm] 22 21 23 19 20 20 21 20 21 Amount of scattered Si [mg/kg] 120 120 210 110 170 120 100 110 180 Number of fusions between single A A A A A A A A A fibers Strand strength [GPa] 5.3 5.3 5.2 5.5 5.4 5.3 5.4 5.5 5.4

(43) TABLE-US-00002 TABLE 2 Example 10 11 12 13 14 15 16 17 18 Proportion of the Aromatic ester compound A-1 32 33 25 40 47 47 47 49 66 Components of Oil [parts by mass] A-2 63 66 56 53 47 47 47 49 17 Composition Amino-modified silicone B-1 0 0 0 0 6 0 0 2 17 [parts by mass] B-2 5 1 19 7 0 6 0 0 0 B-3 0 0 0 0 0 0 6 0 0 Surfactant C-1 6 6 13 13 20 20 20 6 17 [parts by mass] C-2 5 6 13 13 13 13 13 6 17 C-3 11 10 0 0 0 0 0 11 34 Compatibilizing agent D-1 0 0 0 7 0 0 0 0 0 [parts by mass] D-2 0 0 0 0 0 0 0 0 0 D-3 0 0 0 0 0 0 0 0 0 Mass ratio (A-2/A-1) 1.97 2.00 2.24 1.33 1.00 1.00 1.00 1.00 0.26 Content of amino-modified silicone 5 1 23 8 6 6 6 2 20 [parts by mass] Adhesion amount of oil agent [% by mass] 1.3 1.1 0.8 1.1 1.4 1.3 1.4 1.4 1.1 Adhesion amount of amino-modified silicone 0.05 0.01 0.12 0.06 0.06 0.06 0.06 0.02 0.11 [% by mass] Adhesion amount of aromatic ester compound 1.01 0.89 0.51 0.77 0.99 0.92 0.99 1.12 0.54 (A-1 + A-2) [% by mass] Ratio of adhesion amounts (A-2/A-1) 1.97 2.00 2.24 1.33 1.00 1.00 1.00 1.00 0.26 Evaluation Operability A A A A A A A A A Flameproofing bundlability [mm] 21 23 19 19 20 20 20 21 21 Amount of scattered Si [mg/kg] 110 10 190 160 60 80 50 10 120 Number of fusions between single A A A A A A A A A fibers Strand strength [GPa] 5.4 4.9 5.5 5.4 5.2 5.1 5.2 4.9 5.0

(44) TABLE-US-00003 TABLE 3 Comparative Example 1 2 3 4 5 6 7 8 9 10 Proportion of the Aromatic ester A-1 12 33 75 47 86 0 0 0 0 0 Components of Oil compound A-2 87 67 8 0 0 47 86 0 0 0 Composition [parts by mass] A-3 0 0 0 47 0 47 0 93 100 0 Amino-modified silicone B-1 1 0 17 6 0 6 0 7 0 100 [parts by mass] B-4 0 0 0 0 14 0 14 0 0 0 Surfactant C-1 6 6 17 20 21 20 21 20 0 0 [parts by mass] C-2 6 6 17 13 21 13 21 13 0 0 C-3 11 11 33 0 0 0 0 0 11 11 Mass ratio (A-2/A-1) 7.25 2.03 0.11 Content of amino-modified silicone 1 20 [parts by mass] Adhesion amount of oil agent [% by mass] 1.4 1.2 0.9 1.2 1.1 1.5 1.4 1.3 1.3 1.5 Adhesion amount of amino-modified silicone 0.01 0.00 0.09 0.05 0.11 0.07 0.14 0.07 0.00 1.35 [% by mass] Adhesion amount of aromatic ester compounds 1.13 0.98 0.45 0.42 0.67 0.53 0.85 0.00 0.00 0.00 (A-1 + A-2) [% by mass] Ratio of adhesion amounts (A-2/A-1) 7.25 2.03 0.11 Evaluation Operability A C A A C B C B C A Flameproofing bundlability 25 24 21 21 20 25 24 27 28 20 [mm] Amount of scattered Si [mg/kg] 20 0 110 60 90 60 100 60 0 1050 Number of fusions between A B A B B B B B B A single fibers Strand strength [GPa] 4.7 3.8 4.8 4.4 4.5 4.7 4.6 4.0 3.5 5.1

(45) In Tables 1 to 3, the term content of amino-modified silicone refers to the quantity relative to 100 parts by mass representing the total quantities of the aromatic ester compound (A-1) and the aromatic ester compound (A-2).

(46) As is evident in Tables 1 and 2, the adhesion amount of the oil agent in each Example was appropriate. Moreover, the operability of the process for manufacturing a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto was satisfactory.

(47) In addition, the bundlability after the flameproofing step in each Example was satisfactory, i.e., 19 to 23 mm. Furthermore, the amount of scattered Si in the flameproofing step was small, and the operability in the calcination step was satisfactory.

(48) The carbon fiber bundle obtained in each Example was substantially free from fusion between single fibers, showed a high value for strand strength, and was excellent in mechanical properties.

(49) Although the amount of scattered Si in the flameproofing step was relatively large in Examples 3, 5, 9, and 12 compared to the other Examples, the amount was not so large as to cause a problem in industrial continuous operation.

(50) On the other hand, with respect to Comparative Examples 1 and 3, in which polyoxyethylene bisphenol A dilaurate (A-1) and tri-isodecyl trimellitate (A-2) were mixed and used, Comparative Example 1, in which the mass ratio of A-1 and A-2 was 7.25, i.e., the content of A-2 was extremely high, and Comparative Example 3, in which the mass ratio of A-1 and A-2 was 0.11, i.e., the quantity of A-1 contained was larger than that of A-2 contained, showed results that were equal to those of the examples with respect to operability, flameproofing bundlability, amount of scattered Si, and the number of fusions but showed results that were inferior to those of the examples with respect to the value of strand strength.

(51) In Comparative Example 2, in which proper quantities of polyoxyethylene bisphenol A dilaurate (A-1) and tri-isodecyl trimellitate (A-2) were blended, but the oil composition did not contain an amino-modified silicone, the operability was inferior to those in the examples: A single yarn was entwined around the conveying roll several times during a 24-hours continuous operation for a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto. In addition, the number of fusions in the obtained carbon fiber bundle was large, and the value of strand strength was lower than those in the examples.

(52) In Comparative Example 4, in which polyoxyethylene bisphenol A dilaurate (A-1) and pentaerythritol tetrastearate (A-3) were used as the aromatic ester components, the operability, flameproofing bundlability, and the amount of scattered Si were equal to those in the examples, but with respect to the carbon fiber bundle, the number of fusions was large, and the strand strength was not satisfactory.

(53) In Comparative Example 5, in which only polyoxyethylene bisphenol A dilaurate (A-1) was used as the aromatic ester component, and an amino-modified silicone (B-4) having side chains of primary amine and primary, secondary amine and having a viscosity of 10000 mm.sup.2/s and an amino equivalent of 7000 g/mol was used as the amino-modified silicone, the operability was markedly low: a single yarn was entwined around the conveying roll a large number of times during a 24-hours continuous operation for a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto. In addition, the number of fusions in the obtained carbon fiber bundle was large, and the strand strength was not satisfactory.

(54) In Comparative Example 6, in which tri-isodecyl trimellitate (A-2) and pentaerythritol tetrastearate (A-3) were used as the aromatic ester components, the operability was inferior to those in the examples: A single yarn was entwined around the conveying roll several times during a 24-hours continuous operation for a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto. In addition, the number of fusions in the obtained carbon fiber bundle was large, and the value of strand strength was lower than those in the examples.

(55) In Comparative Example 7, in which only tri-isodecyl trimellitate (A-2) was used as the aromatic ester component, and an amino-modified silicone (B-4) having side chains of primary amine and primary, secondary amine and having a viscosity of 10000 mm.sup.2/s and an amino equivalent of 7000 g/mol was used as the amino-modified silicone, the operability was low, there was fusion in the obtained carbon fiber bundle, and the value of strand strength was lower than those in the examples.

(56) In Comparative Example 8, in which only pentaerythritol tetrastearate (A-3) was used as the aromatic ester component, the operability was slightly low despite the fact that the adhesion amount of the oil agent was appropriate, and a single yarn was entwined around the conveying roll several times during a 24-hours continuous operation for a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto. In addition, the flameproofing bundlability was low, and there were a large number of fusions in the obtained carbon fiber bundle, and the strand strength was lower than in the examples.

(57) In Comparative Example 9, in which only pentaerythritol tetrastearate (A-3) was used as the aromatic ester component, and the oil composition did not contain an amino-modified silicone or a PO/EO block copolymerization polyether, the amount of scattered Si in the flameproofing step was substantially absent because the oil composition did not contain an amino-modified silicone. However, the results of evaluation were extremely inferior to those of the examples with respect to all of the other endpoints.

(58) In Comparative Example 10, in which the oil composition did not contain any aromatic ester component and contained an amino-modified silicone, the operability, the flameproofing bundlability, the number of fusions, and the strand strength were equal to those in the examples, but the amount of scattered Si was extremely large and interfered with industrial continuous calcination.

Test Examples 1 to 5

(59) An oil agent was prepared in the same manner as Example 1, except that the types and loadings of the components constituting the oil composition were changed as shown in Table 4, and 3 parts by mass of an antioxidant (a mixture of tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane and ditridecyl thiodipropionate; mass ratio, 2:1) was dispersed in the amino-modified silicone in advance, the aromatic esters and surfactants were added with stirring, water is added to the mixture for emulsification to form an oil composition dispersion, and 4 parts by mass of an antistatic agent (oleyl dimethyl ethyl ammonium ethosulfate) was dispersed.

(60) Using the obtained oil agent, a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto and a carbon fiber bundle were manufactured, and the strand strength of the carbon fiber bundle was measured in the same manner as Example 1, except that changes were made in such a manner that the value of the adhesion amount of the oil agent was as shown in Table 4. The results are shown in Table 4.

(61) Test Examples 2 to 4 belong to the category of the examples, and Test Example 1 and 5 belong to the category of the Comparative Examples.

(62) TABLE-US-00004 TABLE 4 Test Example 1 2 3 4 5 Proportion of the Aromatic ester compound A-1 27 27 27 27 27 Components of Oil [parts by mass] A-2 60 60 60 60 60 Composition Amino-modified silicone B-1 13 13 13 13 13 [parts by mass] Surfactant C-1 13 13 13 13 13 [parts by mass] C-2 13 13 13 13 13 Antistatic agent [parts by mass] 4 4 4 4 4 Antioxidant [parts by mass] 3 3 3 3 3 Mass ratio (A-2/A-1) 2.22 2.22 2.22 2.22 2.22 Content of amino-modified silicone 15 15 15 15 15 [parts by mass] Adhesion amount of oil agent [% by mass] 0.4 0.7 1.0 1.3 2.2 Adhesion amount of amino-modified silicone 0.04 0.07 0.10 0.13 0.22 [% by mass] Adhesion amount of aromatic ester compounds 0.26 0.46 0.65 0.85 1.44 (A-1 + A-2) [% by mass] Ratio of adhesion amounts (A-2/A-1) 2.22 2.22 2.22 2.22 2.22 Strand strength [GPa] 3.9 4.9 5.1 5.1 4.8

(63) In Table 4, the term content of amino-modified silicone refers to the quantity relative to 100 parts by mass representing the total quantities of the aromatic ester compound (A-1) and the aromatic ester compound (A-2).

(64) As is evident in Table 4, the carbon fiber bundles obtained in Test Examples 2 to 4 showed higher strand strength than the carbon fiber bundles obtained in Test Examples 1 and 5 and were more excellent in mechanical properties.

(65) Particularly in Test Example 1, in which the total adhesion amount of polyoxyethylene bisphenol A dilaurate (A-1) and tri-isodecyl trimellitate (A-2) is 0.26% by mass, the value of the strand strength of the carbon fiber bundle was lower than in the other Test Examples.

INDUSTRIAL APPLICABILITY

(66) The oil composition for carbon-fiber-precursor acrylic fiber according to the present invention can effectively suppress fusion between single fibers in the calcination step. Furthermore, by the use of the oil composition of the present invention, the decrease in operability that occurs when an oil composition containing a silicone as the main component is used can be suppressed, and a carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto that has good bundlability can be obtained. From the carbon-fiber-precursor acrylic fiber bundle with an oil composition adhering thereto, a carbon fiber bundle having excellent mechanical properties can be manufactured with good productivity.

(67) The carbon fiber bundle obtained from the carbon-fiber-precursor acrylic fiber bundle to which the oil composition of the present invention is adhered can be formed into a prepreg, which can then be molded into a composite material. The composite materials in which the carbon fiber bundle is used can be suitably used as a useful material in sporting applications, such as a golf shaft and a fishing rod, as a structural material in motor vehicle and aerospace applications, and in various gas storage tank applications.