BACKGROUND OF THE INVENTION

Field of the invention The present invention relates, in general, to fiber prepared from ethylene/chlorotrifluoroethylene polymer alone or in combination with different types of polymers a n d , m o r e p a r t i c u l a r l y , t o ethylene/chlorotri luoroethylene fiber applicable for automotive upholstery fabric, medical drapes and gowns, and outwear garments for leisure and sports. Also, the present invention is concerned with a method for preparing the ethylene/chlorotrifluoroethylene fiber.

Description of the Prior Art Excellent in chemical resistance, flame resistance, anti-contamination, water repellence and electrical insulat ion , fluoropo lymers , such as ethylene/chlorotrifluoroethylene polymers , are widely used as materials for wire and cable insulation, linings and coatings for tanks, pumps, valves and pipes.

In the previous arts, manufacturing methods of nonwoven fabrics or membranes were only disclosed. For example, U.S. Pat. No. 5,401,418 discloses a melt-blown method to prepare nonwoven fabrics. Fluoropolymers are also used to prepare hollow fiber membrane as introduced in U,S. Pat. No. 4,968,733. Due to their very low melt strength or high crystallization rate, these fluoropolymers have not been able to be prepared into the multifilament fibers whose properties meet the requirements for the weaving process, which requires the

adequate strength, elongation and flexibility of the fibers, thus far. It has restricted the applications for automotive upholstery fabric, medical drapes and gowns, and outwear garments for leisure and sports.

SUMMARY OF THE INVENTION

Therefore, it is an objective of the present invention to overcome the above problems encountered in prior arts and to provide fiber prepared mainly from a copolymer of ethylene and chlorotrifluoroethylene, which have no t on l y the pr o pert i e s o f ethylene/chlorotrifluoroethylene including chemical resistance, flame resistance, water repellence and anti- contamination but also weaveabilit .

In accordance with the present invention, the above objective could be accomplished by a provision of ethylene/chlorotrifluoroethylene fibers prepared from ethylene/chlorotrifluoroethylene copolymer alone or in combination with other polymers, which have a melt flow index (MI) of 50-1,000 g/10 min. In the present invention, the term, ethylene/chlorotrifluoroethylene fiber means all fiber prepared by spinning ethylene/chlorotrifluoroethylene polymer alone, sheath-core type fiber prepared by spinning a composite in which ethylene/chlorotrifluoroethylene polymer is the sheath component with another polymer of core component, and sea and island type fiber prepared by spinning a composite which comprises ethylene/chlorotrifluoroethylene polymer as the island component and an elutable polymer as the sea component.

DETAILED DESCRIPTION OF THE INVENTION

The ethylene/chlorotrifluoroethylene polymer used in the present invention has preferably a melt flow index of 50-1,000 g/10 min and more preferably 50-500 g/10 min when measuring the amount which flows through a 0.0825 inch orifice for 10 min at 275°C under a load of 2,160 g according to ASTM D-1238. For example, if the ethylene/chlorotrifluoroethylene polymer has an MI less than 50 g/10 min, yarn breakage occurs under the spinneret and thus, it is impossible to take up the yarn. On the other hand, if the MI exceeds 1,000 g/10 min, the physical properties proper to fiber cannot be obtained.

When the ethylene/chlorotrifluoroethylene fiber of the present invention is of the sheath-core type in which the ethylene/chlorotrifluoroethylene polymer is used as the sheath component while using a different type of polymer as the core component, preferred examples of the different type of polymer include polyesters, polyamides and polyolefins. This composite fiber is advantageous in that the production cost is low while maintaining the e x c e l l e n t p r o p e r t i e s o f t h e ethylene/chlorotrifluoroethylene. Sheath-core type fiber consists of a core component positioned at the center and a sheath component surrounding the core part. In the ethylene/chlorotrifluoroethylene fiber of the present invention, the core component has an area of 30-70 % with the sheath component correspondingly ranging from 30 to 70 % in area. Within this range, good processability and characteristics of ethylene/chlorotrifluoroethylene can be accomplished. For example, if the sheath component is below 30 %, that is, the core component exceeds 70 %, the core component is biased toward one side, being laid bare,

or microscopic cracks are generated on the surface of composite fiber, deleteriously affecting chemical resistance. On the other hand, the sheath component is above 70 %, that is, the core component is below 30 %, the effect of reducing production cost is not so large.

A s a f o r e m e n t i o n e d , t h e ethylene/chlorotrifluoroethylene fiber of the present invention may be of the sea and island type in which the ethylene/chlorotrifluoroethylene polymer is used as the island component with an elutable polymer as the sea component. In this case, the preferred examples of the elutable polymer include polyesters, polyamides and polyolefins. It is preferred that the island component is used at an amount of 60-80 % by weight with the amount of the sea component ranging correspondingly from 20-40 % by weight. The less the amount of the sea component is, the better. However, if the sea component is below 20 % by weight, the islands adhere to each other. On the other hand, if the island component is above 40 % by weight, it is economically unfavorable.

The sea and island type fiber according to the present invention may be treated with a suitable solvent in an ordinary elution process to give ultrafine ethylene/chlorotrifluoroethylene fiber with a size of about 0.01-0.1 denier. This ultrafine fiber may be prepared into filaments for textile and knitwear or into staple fibers for suede. These products show good performance in water repellence, oil repellence and chemical resistance. As mentioned above, the fiber of the present i nven tion i s prepared by spi nning ethylene/chlorotrifluoroethylene polymer with an MI of 50- 1,000 g/10 min, alone or in combination with a different

type of polymer. The spinning is carried out preferably at a speed of 400-1,300 m/min and at a temperature of 280- 320°C and more preferably 290-310°C. For example, if the spinning temperature is lower than 280°C, the resulting fiber is poor in the take-up process and drawability. On the other hand, if the spinning is performed at a temperature higher than 320°C, it is highly likely to deteriorate the fiber. Spinning speed higher than 1,300 m/min leads to a decrease in drawability. As-spun fiber is preferably drawn at the draw ratio ranging from 1.8 to 3.5. For example, if the draw ratio is less than 1.8, the resulting fiber is poor in strength. On the other hand, if the draw ratio exceeds 3.5, fibrils are generated, making it difficult to carrying out the drawing process. Although not being specifically restricted, the drawing temperature and the thermal treatment temperature are preferably controlled at 40-

100°C and 40-200°C respectively in the drawing process.

The ethylene/chlorotrifluoroethylene fiber prepared as above-illustrated processes can be weaved and therefore, applied for automotive upholstery fabric, medical drapes and gowns, and out wear garments for leisure and sports requiring chemical resistance, flame resistance, anti-contamination, and water repellence. A better understanding of the present invention may be obtained in light of following examples which are set forth to illustrate, but are not to be construed to limit, the present invention.

EXAMPLES AND COMPARATIVE EXAMPLES

P R E P A R A T I O N 0 F F I B E R F R O M

ETHYLENE/CHLOROTRIFLUOROETHYLENE POLYMER ALONE

EXAMPLE I-l

Undrawn fiber of 190 denier was prepared by spinning ethylene/chlorotrifluoroethylene polymer having an MI of 75 through a 24-hole spinneret with a diameter of 0.1 mm at 300°C at a spinning speed of 700 m/min in an output rate of 15 g/min in a screw extruder. As-spun fiber was drawn at a draw ration of 2.5 at a drawing temperature of 80°C and at a thermal treatment temperature of 130°C to give 75D/24F fiber. This ethylene/chlorotrifluoroethylene fiber was tested for strength and elongation and the results are given as shown in Table 1 below.

EXAMPLE 1-2

The same procedure as Example I-l, except for using ethylene/chlorotrifluoroethylene polymer with an MI of 52 at a spinning temperature of 310°C, was repeated.

EXAMPLE 1-3

The same procedure as Example I-l was repeated, except that ethylene/chlorotrifluoroethylene polymer with an MI of 130 was used at a spinning temperature of 310°C at a spinning speed of 1,200 m/min and the draw ratio was

2.3.

COMPARATIVE EXAMPLE I-l

The same procedure as Example I-l was repeated, except that the spinning temperature was 270°C. Yarn

breakage was occurred, and it was impossible to take-up.

COMPARATIVE EXAMPLE 1-2

Spinning was carried out in a similar manner to that of Example 1-2, except that the winding speed was 1,500 m/min. Just below the spinneret, yarn breakage was occurred, and it was impossible to take-up.

TABLE 1

Spinning Spinning

Exmp. Temp. Speed Draw Strength Elonga¬

No. MI (°C) (m/min) Ratio (9/ ) tion^) Note

1-1 75 300 700 2.5 2.9 21

1-2 52 310 700 2.5 2.7 20

1-3 130 310 1 ,200 2.3 2.6 21

C.1-1 75 270 700 - - - Wl'

C.I-2 52 310 1 ,500 - - - WI*

winding impossible

II PREPARATION OF SHEATH-CORE TYPE ETHYLENE/ CHLOROTRIFLUOROETHYLENE FIBER

Spinning and Drawing

While being wound at a speed of 800 m/min, ethylene/chlorotrifluoroethylene polymer was spun at a head temperature of 300°C through an ordinary sheath-core spinneret. Then, it was drawn at a draw ratio of 2.0 at a speed of 400 m/min using an ordinary drawing machine in which the heat roller and the heat plate were heated at

a temperature of 90°C and 190°C, respectively.

Test for Chemical Resistance

After being treated in 50% sulfuric acid and 10% sodium hydroxide for 24 hr, fiber was tested for strength retention. The fiber used showed a strength of 2-4 g/De ' and an elongation of 10-30% before the chemical resistance test. Strength retention was calculated according to the following formula:

Fiber Strength after treatment Strength Retention = x 100

Fiber Strength before treatment

Test for Thermal Resistance

Oxygen index was measured according to ASTM D-2863.

EXAMPLE II-l

Using ethylene/chlorotrifluoroethylene with an MI of 75 (measured at 275°C under a load of 2,160 g according to ASTM D-1238) as a sheath component and polyethyleneterephthalate with an intrinsic viscosity of 0.63 as a core component, sheath-core fiber of 150 denier/36 filament in which the cross sectional area ratio of the sheath component to the core component was 50:50 was prepared. The sheath-core fiber was tested for chemical resistance and flame resistance and the results are given as shown in Table 2 below.

EXAMPLE II-2

Using ethylene/chlorotrifluoroethylene with an MI of

75 as a sheath component and nylon with a relative viscosity of 45 in formic acid as a core component, sheath-core fiber of 150 denier/36 filament in which the cross sectional area ratio of the sheath component to the core component was 50:50 was prepared. The sheath-core fiber was tested for chemical resistance and flame resistance and the results are given as shown in Table 2 below.

COMPARATIVE EXAMPLE II-l

Using ethylene/chlorotrifluoroethylene with an MI of 75 as a sheath component and polyethyleneterephthalate with an intrinsic viscosity of 0.63 as a core component under the same spinning spinneret as that of Example II-l, sheath-core fiber of 150 denier/36 filament in which the cross sectional area ratio of the sheath component to the core component was 20:80 was prepared. The sheath-core fiber was tested for chemical resistance and flame resistance and the results are given as shown in Table 2 below.

COMPARATIVE EXAMPLE I1-2

Using ethylene/chlorotrifluoroethylene with an MI of 75 as a sheath component and nylon with a relative viscosity of 45 as a core component under the same spinning spinneret as that of Example II-l, sheath-core fiber of 150 denier/36 filament in which the cross sectional area ratio of the sheath component to the core component was 20:80 was prepared. The sheath-core fiber was tested for chemical resistance and flame resistance and the results are given as shown in Table 2 below.

COMPARATIVE EXAMPLE II1-3

Using an ordinary spinning-spinneret, fiber of 150 denier/36 filament was prepared from polyester with an intrinsic viscosity of 0.63. The fiber was tested for

5 chemical resistance and flame resistance and the results are given as shown in Table 2 below.

COMPARATIVE EXAMPLE III-4

Using an ordinary spinning spinneret, fiber of 150 denier/36 filament was prepared from nylon showing a

10 relative viscosity of 45 in formic acid. The fiber was tested for chemical resistance and flame resistance and the results are given as shown in Table 2 below.

TABLE 2

15 Strength Maintenance

No. 10% NaOH (%) 50% H ₂ S0 ₄ (%) Index

II-l 95 93 42

20 II-2 97 93 43

C.II-1 53 42 26

C.II-2 65 38 28

C.II-3 dissolved 30 22

C.I1-4 52 dissolved 24

?5

Taken together, the data suggested in Table 2 showed that the sheath-core fiber in which the sheath component

of ethylene/chlorotrifluoroethylene polymer amounted to 30-70% still maintained excellent chemical resistance and flame resistance, on the basis of the strength retention of the ethylene/chlorotrifluoroethylene polymer alone.

III PREPARATION OF SEA AND ISLAND TYPE ETHYLENE/ CHLOROTRIFLUOROETHYLENE FIBER

Spinning and Drawing

While being wound at a speed of 900 m/min, undrown fiber which consists of 24 island monofilaments and sea component was obtained by spinning at a temperature of 305"C through an ordinary sea and island type spinning spinneret in a screw extruder. As-spun fiber was drawn at a draw ratio of 2.8 at a draw temperature of 92°C and a thermal treatment temperature of 185°C in an ordinary drawing machine to give fiber of 75D/36F having a strength of 3.28 g/d and an elongation of 26%. This drawn fiber was knitted by circular knitting machine and then, treated in 2% NaOH solution at 100°C for 30 min to elute the sea component, which led to a fine yarn only consisted of the island component.

EXAMPLE III-l

U s i ng a s a n is l a nd co mp on en t ethylene/chlorotrifluoroethylene with an MI of 75 (measured at 275°C under a load of 2,160 g according to ASTM _. D-1238) and as a core component polyester with an intrinsic viscosity of 0.63 and an MI of 95, sea and island fiber in which the ratio of the island component to the sea component was 30/70 was prepared. The processability of spinning and drawing was good. After

elution of the sea component, the island component had a maximal fineness of 0.036 denier.

EXAMPLE II1-2

Using as an island component ethylene/ chlorotrifluoroethylene with an MI of 75 and as a core component polyester with an MI of 129, sea and island fiber in which the ratio of the island component to the sea component was 80/20 was prepared. The fiber obtained was good in spinnability and drawability. After elution of the sea component, the island component had a maximal fineness of 0.07 denier.

COMPARATIVE EXAMPLE III-l

The same procedure as that of Example III-l was repeated, except for the ratio of the island component to the sea component was 90/10. The formation of cross section was poor because the island components adhered to each other. Spinnability and drawability was also poor.

COMPARATIVE EXAMPLE III-2

The same procedure as that of Example III-l was repeated, except for the ratio of the island component to the sea component was 10/90. Performance in fiber forma _. tion was good. However, it was economically unfavorable because the sea component to be removed at an eluting process was too much. The fiber of Examples III-l and III-2 and Comparative Examples III-l and III-2 was compared from a point of view

of performance in fiber formation and cross section and the results are given as shown in Table 3 below.

TABLE 3

Composition (wt%) Performance

Exmp In fiber Cross Overal1

No. Island Sea Formation Section Evaluation

III-l 70 30 good good good

III-2 80 20 good good good

C.III-l 90 10 poor poor poor

C.III-2 10 90 good good poor

The present invention has been described in an illustrative manner, and it is to be understood the terminology used is intended to be in the nature of description rather than of limitation.

Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.