JP7234467B2 - Composite crimped fiber used for knitted fabric and method for producing the same - Google Patents

Description

FIELD OF THE INVENTION The present invention generally relates to polyester fiber manufacturing technology, and more particularly to a bicomponent crimped fiber for use in a type of knit fabric and a method for manufacturing the same.

For chemical fibers, the performance of fibers obtained from different polymer raw materials is completely different, and each has advantages and disadvantages. For this reason, more and more textile products are being developed in which the performance of different fibers is combined to exhibit their superiority. In the meantime, the side-by-side bicomponent conjugate fiber is bent away from the fiber axis due to the different heat shrinkability of the two components, and a permanent helical three-dimensional crimp appears like wool. It has excellent durability and high elasticity, and is widely used in the apparel industry because it gives the fabric excellent elasticity, bulkiness and coverability. However, there are high requirements for the production method of the polyester bicomponent conjugate fiber, that is, the flow behavior of the polymer melt in the discharge hole must be appropriately controlled. The improvement of the sweat function has not yet been devised.

Therefore, the development of a polyester composite fiber that is three-dimensionally crimped and has excellent moisture-absorbing and sweat-absorbing properties is a significant issue.

The present invention provides a conjugate crimped fiber for use in a kind of knitted fabric and a method for producing the same, which overcomes the problem of insufficient moisture absorption and perspiration drainage of conventional polyester conjugate fibers.

Therefore, the present invention uses the following technical solutions. Namely
A method for producing composite crimped fibers used for knitting, in the process of producing circular parallel composite fibers from polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) based on a fully drawn yarn (FDY) process , Change the discharge hole on the spinneret from circular to Y-shaped, cool by annular blowing, control the arrangement of the Y-shaped discharge hole on the spinneret to meet certain conditions, produce FDY, On the other hand, relaxation heat treatment is performed to obtain a conjugate crimped fiber used for knitting (the spinning assembly used for the Y-shaped side-by-side conjugate fiber produced by the present invention is the spinning assembly used for the circular core-sheath type conjugate fiber produced by the conventional technology. based on the assembly, but with a different shape of the discharge hole).
The length ratio of the three slits of the same Y-shaped discharge hole is 1.0:1.1-1.4:2.0-2.5, the width ratio is 1.5:1.5:1, and the length-width ratio of the shortest slit is 2.5-3.5. : 1, the angle formed by the center lines of two adjacent slits is 120°, the shape and size of each Y-shaped discharge hole are the same,
According to the above-mentioned constant conditions, the center line of the longest slit of any Y-shaped discharge hole is used as a reference line, and the other Y-shaped discharge holes are classified into two types, one type being the center line of the longest slit. is parallel to the reference line, another type has the center line of the longest slit perpendicular to the reference line, and the two types of Y-shaped discharge holes have the same number,
When PET and PBT flow through the guide holes of each Y-shaped discharge hole, the contact surfaces are parallel to each other (because the apparent viscosities of PET and PBT are similar in the guide holes of the Y-shaped discharge The contact surface between the two is substantially flat).

Preferred embodiments of the present invention are shown below.

In the method for producing the composite crimped fibers used for the knitted fabric, the mass ratio of PET and PBT is 30:70 to 70:30.

In the method for producing the composite crimped fiber used for the knitted fabric, the intrinsic viscosity of PET is 0.50 to 0.58 dL / g, the temperature of the spinning beam corresponding to PET is 275 to 280 ° C., and the intrinsic viscosity of PBT is 1.10 to 1.10. 1.21 dL/g, and the temperature of the spinning beam corresponding to PBT is 260-265°C.

In the manufacturing method of the composite crimped fiber used for the knitted fabric, the parameters of the FDY process are: spinning temperature 274 ~ 277 ° C, cooling temperature 20 ~ 25 ° C, interlace nozzle pressure 0.20 ~ 0.30 MPa, first roller speed 2000 ~2200m/min, the first roller temperature is 75~85℃, the second roller speed is 3300~3600m/min, the second roller temperature is 135~145℃, and the winding speed is 3230~3510m/min.

In the method for producing the composite crimped fibers used for the knitted fabric, the relaxation heat treatment temperature is 90 to 120° C., and the treatment time is 20 to 30 minutes.

The present invention also provides bicomponent crimped fibers for use in knitted fabrics produced by the method according to any one of the above preferred embodiments. It has a three-dimensional crimped form and is composed of PET/PBT parallel composite monofilaments with a plurality of Y-shaped cross-sections, and an imaginary line perpendicular to the Y-shape dividing the Y-shape into two juxtaposed portions. When made, one part corresponds to PET and the other part corresponds to PBT.

Preferably, for the conjugate crimped fibers used in the knitted fabric,
Based on the Chinese national standard GB6506-2001, its crimp shrinkage rate is 50-54%, crimp stability is 82-85%, crimp elongation rate is 94-98%, and crimp elastic recovery rate is 94-97%. % and
It has a breaking strength of 2.8 cN/dtex or more, a breaking elongation of 43.0±3.0%, and a total fineness of 700-200 dtex.

The principle of the invention is as follows.

The composite crimped fiber used for the knitted fabric in the present invention is FDY obtained by extruding PET and PBT through Y-shaped discharge holes located on the same spinneret plate. In the parallel composite spinning process of the present invention, a substantially planar interface is formed between the PET and PBT flowing into the discharge holes with approximately the same apparent viscosity, and for all discharge holes, their The interface planes are parallel to each other. However, the three-slit orifices in the present invention are arranged in two ways, namely, the centerline of the longest slit of one orifice is parallel to the reference line and the other is orthogonal. Furthermore, since the spinning pressure and melt mass ratio in the spinning process of the present invention are constant, the melt mass ratio in each discharge hole is also equal. Therefore, the angle formed by the boundary surface of the two melts and the orientation of the longest slit of the ejection hole varies depending on the arrangement of the ejection holes. Therefore, the composite single yarns extruded from the discharge holes with different arrangement methods have different Y-shaped cross-sections with different PET/PBT partition types, that is, different composite ratios. When such a composite fiber is heat-treated, a three-dimensional crimp appears due to the difference in heat shrinkage between PET and PBT.

The sharp grooves on the Y-shaped cross section cause capillary action to rapidly absorb and diffuse moisture, so the fabric with the Y-shaped cross section has good moisture absorption and desorption properties. Furthermore, if the Y-shaped cross-section fibers are spontaneously crimped, the absorbed moisture may be led out from the inside of the fabric through the twisted grooves. Therefore, the composite crimped fibers used in the knitted fabric of the present invention can be expected to have better moisture absorption and desorption effects.

Advantages of the present invention include:
(1) In the manufacturing method of the composite crimped fiber used for the knitted fabric of the present invention, the positional relationship between the Y-shaped discharge hole and the Y-shaped discharge hole and the contact surface of the melt of PET and PBT in the guide hole is limited. , the size of the contact surface between the two components in the different monofilaments in the resulting bicomponent crimped fibers is different.
(2) In the composite crimped fiber used for the knitted fabric of the present invention, the contact surface of each melt is different in the cross section of each monofilament, so the composite crimped fiber forms a three-dimensional crimp.
(3) The composite crimped fiber used in the knitted fabric of the present invention is a modified cross-section fiber and is three-dimensionally spontaneously crimped, so that the grooves are twisted and have excellent moisture absorption and desorption performance.

FIG. 4 is a schematic diagram of a Y-shaped discharge hole in the present invention; FIG. 2 is a conceptual diagram of the arrangement of ejection holes of the spinneret in the present invention.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited by the following examples as long as the gist thereof is not exceeded. It should be noted that even if a person skilled in the art who has read the content of the present invention is allowed to make various modifications to the present invention, it is also limited within the scope of the claims of the present invention as an equivalent form of the present invention. . Methods for measuring various physical properties and characteristics in Examples are as follows.
A sketch of the Y-shaped discharge holes in the present invention is shown in FIG. 1, and a conceptual diagram of the arrangement of the discharge holes of the spinneret is shown in FIG. For the Y-shaped discharge hole, the length ratio is 1.0:1.1-1.4:2.0-2.5, the width ratio is 1.5:1.5:1, and the length-to-width ratio of the shortest slit is 2.5-3.5:1. The angle formed by the center lines of the slits is 120°, and the composite crimped fibers used in the knitted fabric have discharge holes in which the center line of the longest slit is parallel to the center line of the longest slit of any of the discharge holes, The number of ejection holes that are perpendicular to the center line of the longest slit should be the same.
Figures 1 and 2 are for illustration only and do not limit the invention.

Example 1
Composite crimped fibers used for knitted fabrics are manufactured by combining PET (with an intrinsic viscosity of 0.54 dL/g) and PBT (with an intrinsic viscosity of 1.16 dL/g) at a mass ratio of 55:45 through the FDY process. , It is extruded from a nozzle with a Y-shaped discharge hole, cooled by annular blowing to form FDY, and then subjected to relaxation heat treatment. someday,
The Y-shaped discharge hole has a length ratio of 1.0:1.1:2.0 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 275°C, the spinpack temperature for PET is 279°C, the spinpack temperature for PBT is 262°C, the cooling temperature is 21°C, the interlace nozzle pressure is 0.3 MPa, and the first roller speed is 2190 m/min. , the first roller temperature is 77°C, the second roller speed is 3340m/min, the second roller temperature is 135°C, and the winding speed is 3270m/min;
The relaxation heat treatment temperature is 104°C, and the treatment time is 27 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used for the knitted fabric has a crimp shrinkage rate of 52%, crimp stability of 83%, crimp elongation rate of 96%, crimp elastic recovery rate of 96%, and breaking strength of 2.8 cN/dtex. , the elongation at break is 46%, and the single yarn fineness is 1.13dtex.

Example 2
The method of manufacturing composite crimped fibers used for knitted fabrics is to combine PET (with an intrinsic viscosity of 0.5 dL/g) and PBT (with an intrinsic viscosity of 1.19 dL/g) at a mass ratio of 40:60 through the FDY process. , It is extruded from a nozzle with a Y-shaped discharge hole, cooled by annular blowing to form FDY, and then subjected to relaxation heat treatment. Among them
The Y-shaped discharge hole has a length ratio of 1.0:1.2:2.2 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 274°C, the spinning pack temperature for PET is 275°C, the spinning pack temperature for PBT is 265°C, the cooling temperature is 20°C, the interlace nozzle pressure is 0.2 MPa, and the first roller speed is 2150 m/min. , the first roller temperature is 76°C, the second roller speed is 3360m/min, the second roller temperature is 141°C, and the winding speed is 3290m/min;
The relaxation heat treatment temperature is 120°C, and the treatment time is 26 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used for the knitted fabric has a crimp shrinkage rate of 54%, crimp stability of 85%, crimp elongation rate of 94%, crimp elastic recovery rate of 94%, and breaking strength of 2.8 cN/dtex. , the breaking elongation rate is 43%, and the single yarn fineness is 1 dtex.

Example 3
The method of manufacturing composite crimped fibers used for knitted fabrics is to mix PET (with an intrinsic viscosity of 0.5 dL/g) and PBT (with an intrinsic viscosity of 1.1 dL/g) at a mass ratio of 30:70 through the FDY process. , It is extruded from a nozzle with a Y-shaped discharge hole, cooled by annular blowing to form FDY, and then subjected to relaxation heat treatment. Among them
The Y-shaped discharge hole has a length ratio of 1.0:1.4:2.5 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 274°C, the spinning pack temperature for PET is 275°C, the spinning pack temperature for PBT is 260°C, the cooling temperature is 20°C, the interlacing nozzle pressure is 0.2 MPa, and the first roller speed is 2000 m/min. , the first roller temperature is 75°C, the second roller speed is 3300m/min, the second roller temperature is 135°C, and the winding speed is 3230m/min;
The relaxation heat treatment temperature is 104°C, and the treatment time is 27 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used for the knitted fabric has a crimp shrinkage rate of 54%, crimp stability of 82%, crimp elongation rate of 94%, crimp elastic recovery rate of 94%, and breaking strength of 2.91 cN/dtex. , the elongation at break is 42%, and the single yarn fineness is 1.96dtex.

Example 4
Composite crimped fibers used for knitted fabrics are manufactured by combining PET (with an intrinsic viscosity of 0.53 dL/g) and PBT (with an intrinsic viscosity of 1.16 dL/g) at a mass ratio of 70:30 through the FDY process. , It is extruded from a nozzle with a Y-shaped discharge hole, cooled by annular blowing to form FDY, and then subjected to relaxation heat treatment. Among them
The Y-shaped discharge hole has a length ratio of 1.0:1.3:2.5 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 274°C, the spinpack temperature for PET is 278°C, the spinpack temperature for PBT is 261°C, the cooling temperature is 21°C, the interlacing nozzle pressure is 0.2MPa, and the first roller speed is 2200m/min. , the first roller temperature is 83°C, the second roller speed is 3550m/min, the second roller temperature is 145°C, and the winding speed is 3480m/min;
The relaxation heat treatment temperature is 113°C, and the treatment time is 27 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used for the knitted fabric has a crimp shrinkage rate of 50%, a crimp stability of 83%, a crimp elongation rate of 95%, a crimp elastic recovery rate of 95%, and a breaking strength of 2.98 cN/. dtex, breaking elongation rate is 42%, single yarn fineness is 1.33dtex.

Example 5
Composite crimped fibers used for knitted fabrics are manufactured by combining PET (with an intrinsic viscosity of 0.56 dL/g) and PBT (with an intrinsic viscosity of 1.15 dL/g) at a mass ratio of 60:40 through the FDY process. , extruding from a nozzle with a Y-shaped discharge hole, cooling by annular blowing to form FDY, and then subjecting it to relaxation heat treatment. Among them
The Y-shaped discharge hole has a length ratio of 1.0:1.1:2.5 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 276°C, the spinning pack temperature for PET is 279°C, the spinning pack temperature for PBT is 261°C, the cooling temperature is 23°C, the interlacing nozzle pressure is 0.3 MPa, and the first roller speed is 2050 m/min. , the first roller temperature is 78°C, the second roller speed is 3430m/min, the second roller temperature is 140°C, and the winding speed is 3360m/min;
The relaxation heat treatment temperature is 114°C, and the treatment time is 27 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used for the knitted fabric has a crimp shrinkage rate of 50%, a crimp stability of 85%, a crimp elongation rate of 97%, a crimp elastic recovery rate of 97%, and a breaking strength of 2.99 cN/. dtex, breaking elongation rate is 41%, single yarn fineness is 1.35dtex.

Example 6
Composite crimped fibers used for knitted fabrics are manufactured by combining PET (with an intrinsic viscosity of 0.52 dL/g) and PBT (with an intrinsic viscosity of 1.11 dL/g) at a mass ratio of 40:60 through the FDY process. , extruding from a nozzle with a Y-shaped discharge hole, cooling by annular blowing to form FDY, and then subjecting it to relaxation heat treatment. Among them
The Y-shaped discharge hole has a length ratio of 1.0:1.4:2.0 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 274°C, the spinning pack temperature for PET is 277°C, the spinning pack temperature for PBT is 260°C, the cooling temperature is 22°C, the interlacing nozzle pressure is 0.3 MPa, and the first roller speed is 2060 m/min. , the first roller temperature is 83°C, the second roller speed is 3460m/min, the second roller temperature is 136°C, and the winding speed is 3390m/min;
The relaxation heat treatment temperature is 104°C, and the treatment time is 27 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used for the knitted fabric has a crimp shrinkage rate of 53%, a crimp stability of 82%, a crimp elongation rate of 94%, a crimp elastic recovery rate of 94%, and a breaking strength of 2.99 cN/. dtex, breaking elongation rate is 40%, single yarn fineness is 2dtex.

Example 7
Composite crimped fibers used for knitted fabrics are manufactured by combining PET (with an intrinsic viscosity of 0.58 dL/g) and PBT (with an intrinsic viscosity of 1.21 dL/g) at a mass ratio of 70:30 through the FDY process. , extruding from a nozzle with a Y-shaped discharge hole, cooling by annular blowing to form FDY, and then subjecting it to relaxation heat treatment. Among them
The Y-shaped discharge hole has a length ratio of 1.0:1.2:2.4 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 277°C, the spinning pack temperature for PET is 280°C, the spinning pack temperature for PBT is 265°C, the cooling temperature is 25°C, the interlacing nozzle pressure is 0.3 MPa, and the first roller speed is 2200 m/min. , the first roller temperature is 85°C, the second roller speed is 3600m/min, the second roller temperature is 145°C, and the winding speed is 3510m/min;
The relaxation heat treatment temperature is 120°C, and the treatment time is 20 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used for the knitted fabric has a crimp shrinkage rate of 50%, a crimp stability of 85%, a crimp elongation rate of 98%, a crimp elastic recovery rate of 98%, and a breaking strength of 3 cN/dtex. , the elongation at break is 40% and the single yarn fineness is 1 dtex.

Example 8
Composite crimped fibers used for knitted fabrics are manufactured by combining PET (with an intrinsic viscosity of 0.56 dL/g) and PBT (with an intrinsic viscosity of 1.18 dL/g) at a mass ratio of 35:65 through the FDY process. , extruding from a nozzle with a Y-shaped discharge hole, cooling by annular blowing to form FDY, and then subjecting it to relaxation heat treatment. Among them
The Y-shaped discharge hole has a length ratio of 1.0:1.3:2.5 and a width ratio of 1.5:1.5:1, and has three slits. The angle formed by the center lines of the slits shall be 120°, and for all discharge holes, the center line of the longest slit shall be parallel to the center line of the longest slit of any discharge hole. Make the same number of discharge holes that the center line is orthogonal to;
The boundary surface formed by PET and PBT, which flow into each discharge hole and have approximately the same apparent viscosity, is approximately flat;
The spinning temperature for the FDY process is 277°C, the spinning pack temperature for PET is 280°C, the spinning pack temperature for PBT is 265°C, the cooling temperature is 21°C, the interlacing nozzle pressure is 0.2 MPa, and the first roller speed is 2060 m/min. , the first roller temperature is 80°C, the second roller speed is 3510m/min, the second roller temperature is 142°C, and the winding speed is 3440m/min;
The relaxation heat treatment temperature is 100°C, and the treatment time is 29 minutes.
The composite crimped fiber used for the obtained knitted fabric has a three-dimensional crimp and is composed of PET/PBT parallel composite monofilaments having a plurality of Y-shaped cross sections. If an imaginary line is made perpendicular to the dividing Y, one part corresponds to PET and the other part corresponds to PBT. The composite crimped fiber used in the knitted fabric has a crimp shrinkage rate of 54%, a crimp stability of 82%, a crimp elongation rate of 97%, a crimp elastic recovery rate of 97%, and a breaking strength of 3.08 cN/. dtex, breaking elongation rate is 40%, single yarn fineness is 2dtex.

Claims (5)

A method for producing a Y-shaped composite crimped fiber used for knitting, based on a fully drawn yarn (FDY) process, using polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) as raw materials, and forming a circular parallel composite. The circular discharge hole on the spinneret for producing fibers is changed to a Y-shape, cooled by annular blowing, and controlled so that the arrangement of the Y-shaped discharge hole on the spinneret meets certain conditions, FDY is produced, and the FDY is subjected to relaxation heat treatment to obtain a Y-shaped composite crimped fiber used for knitting,
The three slits of the same Y-shaped discharge hole have a length ratio of 1.0:1.1-1.4:2.0-2.5 and a width ratio of 1.5:1.5:1. , the length-to-width ratio of the shortest slit is 2.5 to 3.5:1, the angle formed by the center lines of two adjacent slits is 120°, and the shape and size of each Y-shaped discharge hole is are identical and
According to the above-mentioned constant conditions, the center line of the longest slit of any Y-shaped discharge hole is used as a reference line, and the other Y-shaped discharge holes are classified into two types, one type being the center line of the longest slit. is parallel to the reference line, another type has the center line of the longest slit perpendicular to the reference line, and the two types of Y-shaped discharge holes have the same number,
A method for producing a Y-shaped composite crimped fiber used for a knitted fabric, wherein the contact surfaces of PET and PBT when flowing through the guide holes of each Y- shaped discharge hole are parallel to each other. The mass ratio of the PET and the PBT is 30:70 to 70:30,
A method for producing a Y-shaped composite crimped fiber used for a knitted fabric according to claim 1, characterized in that: The intrinsic viscosity of PET is 0.50-0.58 dL/g, the temperature of the spinning beam corresponding to PET is 275-280° C., the intrinsic viscosity of PBT is 1.10-1.21 dL/g, the temperature of the spinning beam corresponding to PBT is 260-265°C;
A method for producing a Y-shaped composite crimped fiber used for a knitted fabric according to claim 2, characterized in that: The parameters of the FDY process are: spinning temperature 274-277° C., cooling temperature 20-25° C., interlace nozzle pressure 0.20-0.30 MPa, first roller speed 2000-2200 m/min, first roller temperature 75 to 85 ° C., the second roller speed is 3300 to 3600 m / min, the second roller temperature is 135 to 145 ° C., the winding speed is 3230 to 3510 m / min,
A method for producing a Y-shaped composite crimped fiber used for a knitted fabric according to claim 3, characterized in that: The method for producing a Y-shaped composite crimped fiber used for knitted fabric according to claim 1, wherein the relaxation heat treatment temperature is 90 to 120°C and the treatment time is 20 to 30 minutes.

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