CN107034529B - Fibers, unidirectional fabrics, laminates including the same, tubes and applications thereof - Google Patents

Abstract

The invention relates to a fiber with a sheath-core structure, unidirectional cloth, a laminated board containing the unidirectional cloth, a pipe and application thereof, wherein the diameter of the fiber is between 0.5 and 150 mu m; the polymers of the core layer and the skin layer are the same or different and are independently selected from the following polymers: polyolefins, polyamides, polyurethanes, polyesters, polyoxymethylenes, and the like. Melting point T of the sheath polymer_m1And melting point T of the core Polymer_m2Satisfies the following relation: t is_m2>T_m1(1). The laminated board has high tensile strength, high transparency, high rigidity and good toughness, is particularly suitable for the fields of trays, boxes, buildings, vehicles and the like, and is used as a stressed part or a decorative part. The pipe of the invention has high transparency, high toughness and excellent pressure resistance, and is suitable for the fields of buildings, vehicles and the like.

Description

Fibers, unidirectional fabrics, laminates including the same, tubes and applications thereof

technical field

The invention relates to a fiber, a unidirectional fabric, a laminate including the unidirectional fabric, a tube and applications thereof, in particular to a laminate and tube with high transparency, high strength and high toughness, belonging to the field of composite materials.

Background technique

Polymer fibers are a common raw material, such as polypropylene fibers, polyester fibers, nylon fibers, and polyurethane fibers. Polymer fibers are generally prepared by melt spinning or solution spinning, and the cross-sectional shape of the fibers can be controlled by controlling the die form of the spinneret. In order to prepare multifunctional fiber materials, fibers with a skin-core structure can be formed by multi-component co-extrusion, that is, the raw materials of the fiber skin layers and the raw materials of the core layers are different. Fabric can be formed by weaving fibers, and the process of fabric preparation can be mechanical weaving, or by coating a certain adhesive on the surface of the fibers, the fibers can be bonded together to form a unidirectional fabric. The unidirectional fabric can be cross-laminated to form a high-strength composite material.

Due to the poor compatibility between adhesives and fibers, the properties of the prepared composites are limited. In order to overcome the shortcomings of the existing technology, we provide a new technology for the preparation of new fibers and their composites.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the present invention provides a fiber and a preparation method thereof.

Another object of the present invention is to provide a unidirectional fabric prepared from the above-mentioned fibers and a preparation method thereof.

Another object of the present invention is to provide a laminate containing the above-mentioned unidirectional fabric and a preparation method thereof. The laminate has properties such as high rigidity, high transparency, high strength, and high toughness.

Another object of the present invention is to provide a tube prepared from the above-mentioned fibers and a preparation method thereof. The tube has properties such as high transparency, high toughness, and high pressure resistance.

A further object of the present invention is to provide the use of the above-mentioned unidirectional fabrics, laminates and pipes.

Yet another object of the present invention is to provide an article comprising the above unidirectional fabric, laminate or tube.

The invention provides a fiber with a skin-core structure, the diameter of which is between 0.5 μm and 150 μm; the core layer and the skin layer have the same or different types of polymers, and are independently selected from the following polymers: polyolefin, polyolefin Amide, polyurethane, polyester, polyoxymethylene, etc.; the melting point T _m1 of the skin layer polymer and the melting point T _m2 of the core layer polymer satisfy the following relationship:

T _m2 >T _m1 (1).

Further, the melting point T _m1 of the skin layer polymer and the melting point T _m2 of the core layer polymer satisfy the following relational formula:

T _m2 ≥ T _m1 +10 (1').

Further, the melting point T _m1 of the skin layer polymer and the melting point T _m2 of the core layer polymer satisfy the following relational formula:

T _m2 ≥ T _m1 +20 (1”).

Further, the melting point T _m1 of the skin layer polymer and the melting point T _m2 of the core layer polymer satisfy the following relational formula:

T _m2 ≥ T _m1 +30 (1"').

Further, the range of T _m1 is between 30-300°C; the range of T _m2 is between 60-300°C.

Still further, the diameter of the fibers is between 1 μm and 100 μm, more preferably between 5 μm and 80 μm, and still more preferably between 10 μm and 60 μm.

Further, the mass of the skin layer accounts for 5-60 wt% of the total mass of the fiber. Preferably, 5-50 wt%.

Still further, the polyolefin is selected from homopolymers or copolymers of C _2-20 α-olefins, in particular from polyethylene; polypropylene; polybutene-1; ethylene copolymers, the comonomers thereof is one or more of propylene, butene, pentene, hexene or octene; propylene copolymer, whose comonomer is one or more of ethylene, butene, pentene, hexene or octene or, a butene copolymer whose comonomer is one or more of ethylene, propylene, pentene, hexene or octene.

Further, the polyester is a condensate of dibasic acid and dihydric alcohol, or a ring-opening polymer of lactone. The polyesters are obtained by homopolymerization or copolymerization. For homopolyesters, only one diacid and one diol, or only one lactone; for copolyesters, at least two diacids or two diols, or two Lactone. Preferably, the polyester is selected from polyethylene terephthalate, polybutylene terephthalate or blends thereof.

Further, the polyamide is a condensate of a dibasic acid and a dibasic amine, or a ring-opening polymer of a lactam. The polyamides are obtained by homopolymerization or copolymerization. For homopolyamides, only one diacid and one diamine, or only one lactam; for copolyamides, at least two diacids or two diamines, or two Lactam. Preferably, the polyamide (PA) is selected from PA6, PA66, PA45, PA56, PA10, PA1010, PA11 or PA12; or the copolymerization condensates of various diamines and diacids, such as adipic acid, dodecyl Copolycondensation polymer of diacid, hexamethylenediamine and dodecyldiamine.

Further, the polyoxymethylene is a homopolyoxymethylene or a copolyoxymethylene, more preferably, a homopolymer of trioxane or a copolymer of trioxane, dioxane and other epoxy compounds.

Further, the polyurethane is selected from the polycondensation products of diols and diisocyanates, such as polyester diols, polyether diols, polycarbonate diols, etc. with diphenylmethane diisocyanate, hexamethylene Polycondensation products of diisocyanates and the like.

Further, the core layer and the skin layer of the fiber have good compatibility, and are most preferably the same type of polymer.

The present invention also provides a unidirectional fabric prepared from the above-mentioned one or more fibers.

Further, the unidirectional cloth is prepared by the following method: the fibers are unidirectionally arranged, and the unidirectional cloth is formed under the action of hot pressing, wherein the hot pressing temperature is controlled to be lower than T _m2 .

In the present invention, since the hot pressing temperature is lower than T _m2 , during hot pressing, the fiber skin layer melts, but the core layer has not yet melted. Under the action of pressure, the fiber skin layers are melted and bonded to each other.

The present invention also provides a laminate, which is obtained by laminating at least two layers of the above-mentioned unidirectional fabrics in sequence and then hot pressing.

Further, the laminate is obtained by laminating 2-2000 layers (for example, 2-100 layers, or 5-50 layers, or 10-20 layers) of unidirectional fabrics in sequence and then hot pressing.

Further, the overlapping angle α of the two adjacent unidirectional cloths satisfies the following formula: 0≤α≤90°, and the angle α refers to the angle between the longitude directions of the two unidirectional cloths .

Further, the hot pressing temperature is lower than T _m2 . In the present invention, since the hot pressing temperature is lower than T _m2 , the fiber skin layers melt during hot pressing, but the core layer has not yet melted. Under the action of pressure, the fiber skin layers between the unidirectional cloths melt and bond to each other. Preferably, the hot pressing temperature is approximately equal to the T _m1 . This temperature is the initial melting temperature of the skin layer polymer, that is, the skin layers can fuse with each other under the condition of hot pressing pressure.

Further, the pressure of the hot pressing is 0.5 MPa to 30 MPa.

Further, the thickness of the laminate is between 100 μm and 200 mm, preferably between 2 mm and 50 mm.

The present invention also provides a tube, which is obtained by hot pressing after the fibers of the above-mentioned skin-core structure are continuously wound on a cylindrical mold.

Further, the hot pressing temperature is lower than T _m2 . In the present invention, since the hot pressing temperature is lower than T _m2 , during hot pressing, the fiber skin layers are melted, but the core layer has not been melted. Under the action of pressure, the fiber skin layers are melted and bonded to each other. Preferably, the hot-pressing temperature is approximately equal to the T _m1 ; this temperature is the initial melting temperature of the skin layer polymer, that is, under the hot-pressing pressure condition, the skin layers can fuse with each other.

Further, the pressure of the hot pressing is 0.5 MPa to 30 MPa.

Further, the thickness of the pipe wall of the pipe material is between 100 μm and 200 mm, preferably between 2 mm and 50 mm.

The present invention also provides a method for preparing the fiber of the above-mentioned skin-core structure, which comprises the following steps:

(1) The skin layer polymer whose melting point is T _m1 and the core layer polymer whose melting point is T _m2 are respectively injected into a single-screw extruder with a heating device for melt plasticization, and the corresponding screw plasticizing section temperature are T _p1 and T _p2 respectively, wherein: T _m1 +30≤T _p1 ≤T _m1 +50, T _m1 +50≤T _p2 ≤T _m1 +90;

(2) the melt formed in the step (1) is spit out into a thread through a bicomponent spinning assembly and a spinneret;

(3) spinning and heat-setting to obtain the fibers of the sheath-core structure.

Preferably, in step (2), the melts formed in step (1) are respectively accurately metered by a gear pump, and the volume ratio of the skin layer polymer and the core layer polymer is controlled to be 1/9 to 9/1. Bicomponent spin packs and spinnerets are spun out into strands.

Preferably, in step (3), the filaments spit out in step (2) are bundled, oiled, and then wound at a speed of 500-2500 m/min to obtain pre-oriented filaments, and then drawn and heat-set to obtain The fibers of the sheath-core structure are sheath-core composite fully oriented fibers with a monofilament linear density of 2-12 dtex. Preferably, the drawing temperature and heat setting temperature are T _d and T _s respectively, wherein: (T _g1 +T _m1 )/2≤T _d ≤(T _g2 +T _m2 )/2, T _d ≤T _s ≤(T _g2 +T _m2 )/2, T _g1 and T _g2 are the glass transition temperatures of the skin layer polymer and the core layer polymer, respectively. Further preferably, the drafting ratio is 1.5-4.5 times, and the heat-setting ratio is 0.9-1.1 times; or,

Spinning, heat-setting and winding at a speed of 2500-4500 m/min are performed on the filaments spun out in step (2) after being bundled and oiled to obtain the fibers of the skin-core structure, where the linear density of the monofilament is 2 ~12dtex skin-core composite fully oriented yarn. Preferably, the heat setting temperature is T _s , (T _g1 +T _m1 )/2≤T _s ≤(T _g2 +T _m2 )/2, and T _g1 and T _g2 are the skin layer polymer and the core layer polymer, respectively the glass transition temperature. Further preferably, the thermal setting magnification is 0.85 to 1.15 times.

The present invention also provides a method for preparing the above-mentioned unidirectional cloth, which comprises the following steps: unidirectionally arranging the fibers, and forming the unidirectional cloth under the action of hot pressing.

Preferably, the temperature of the hot pressing is controlled to be lower than T _m2 .

According to the present invention, the preparation method specifically comprises the following steps:

The fibers of the skin-core structure are unidirectionally arranged, unwind on the creel, pass through the godet roll, tension roll, yarn separator, hot roll, cooling zone, pulling roll and winding device in sequence, and then pass through the hot pressing. The unidirectional cloth is formed under the action, wherein the hot pressing temperature is controlled to be lower than T _m2 .

Preferably, the godet roll, the tension roll and the pulling roll are five rolls or seven rolls, and the heat rolls are one pair or two pairs. Further, the roll surface temperature ( _ie , the hot pressing temperature) of the hot roll is Tr , and T _m1 ≤ _Tr <T _m2 . Further, the cooling zone can adopt natural cooling or blast cooling.

The present invention also provides a method for preparing the above-mentioned laminate, which comprises the following steps: preparing a unidirectional cloth; laminating at least two layers of the unidirectional cloth in sequence and then hot pressing to obtain the laminate.

Further, 2-2000 layers (for example, 2-100 layers, or 5-50 layers, or 10-20 layers) of unidirectional fabrics are stacked in sequence and then hot-pressed to prepare the laminate.

Further, the hot pressing temperature is lower than T _m2 . In the present invention, since the hot pressing temperature is lower than T _m2 , the fiber skin layer melts during hot pressing, but the core layer has not yet melted. Under the action of pressure, the fiber skin layers between the unidirectional fabrics melt and bond to each other. Preferably, the hot pressing temperature is approximately equal to the T _m1 . This temperature is the initial melting temperature of the skin layer polymer, that is, the skin layers can fuse with each other under the condition of hot pressing pressure. The pressure of the hot pressing is 0.5 MPa to 30 MPa.

Further, the unidirectional cloth is prepared according to the method of the above unidirectional cloth.

Further, the overlapping angle α of the two adjacent unidirectional cloths satisfies the following formula: 0≤α≤90°, and the angle α refers to the angle between the longitude directions of the two unidirectional cloths .

The present invention also provides a method for preparing the above-mentioned pipe, which comprises the following steps: the above-mentioned fibers of the skin-core structure are continuously wound on a cylindrical mold and obtained by hot pressing.

Further, the hot pressing temperature is lower than T _m2 . In the present invention, since the hot pressing temperature is lower than T _m2 , during hot pressing, the fiber skin layers are melted, but the core layer has not been melted. Under the action of pressure, the fiber skin layers are melted and bonded to each other. Preferably, the hot pressing temperature is approximately equal to the Tm ₁ . This temperature is the initial melting temperature of the skin layer polymer, that is, the skin layers can fuse with each other under the condition of hot pressing pressure. The pressure of the hot pressing is 0.5 MPa to 30 MPa.

The present invention also provides the use of the above-mentioned unidirectional cloth, laminate or pipe, which is used in the fields of pallets, boxes, buildings, vehicles, etc., and used as stress-bearing parts or decorative parts.

The present invention also provides an article prepared from the laminate of the present invention. Specifically, the laminate of the present invention is further processed, such as a blister process, to prepare a container or other components, such as a refrigerator panel, a container, an automobile bumper or an automobile interior and exterior trim.

The beneficial effects of the present invention are:

1. The fiber of the skin-core structure of the present invention, that is, the skin-core composite fully oriented yarn, has a strength of 300-600 MPa and an elongation at break of 15-30%.

2. The laminate of the present invention has high tensile strength, high transparency, high rigidity and good toughness, and is especially suitable for trays, boxes, buildings, vehicles and other fields, used as stressed parts or decorative parts (such as refrigerator panels). , containers, car bumpers or car interior and exterior trim parts, etc.).

3. The pipe of the present invention has high transparency, high toughness and excellent pressure resistance, and is suitable for construction, transportation and other fields.

Description of drawings:

Fig. 1 is a schematic view of the structure of the cross section of the fiber of the present invention

2 is a schematic structural diagram of α=90° in a laminate of the present invention

3 is a schematic structural diagram of 0<α<90° in another laminate of the present invention

Fig. 4 Photo of the fiber cross section of the sheath-core structure of the present invention: (a) pre-oriented yarn (spinning speed: 500 m/min); (b) fully oriented yarn (drawing ratio: 2.8 times)

1 fiber; 2 skins; 3 cores.

Detailed ways

The temperature in the present invention refers to degrees Celsius (°C) unless otherwise specified.

[polymer]

The polymer of the skin layer or core layer of the present invention is selected from: polyolefin, polyester, polyamide, polyurethane, polyoxymethylene and the like.

The polyolefin is selected from homopolymers or copolymers of C _2-20 α-olefins, especially selected from polyethylene; polypropylene; polybutene-1; ethylene copolymer, the comonomers are propylene, butylene one or more of ene, pentene, hexene, or octene; propylene copolymers whose comonomers are one or more of ethylene, butene, pentene, hexene, or octene; or, Butene copolymer whose comonomer is one or more of ethylene, propylene, pentene, hexene or octene.

Further, the polyester is a condensate of dibasic acid and dihydric alcohol, or a ring-opening polymer of lactone. The polyesters are obtained by homopolymerization or copolymerization. For homopolyesters, only one diacid and one diol, or only one lactone; for copolyesters, at least two diacids or two diols, or two Lactone. Preferably, the polyester is selected from polyethylene terephthalate, polybutylene terephthalate or blends thereof.

Further, the polyamide is a condensate of a dibasic acid and a dibasic amine, or a ring-opening polymer of a lactam. The polyamides are obtained by homopolymerization or copolymerization. For homopolyamides, only one diacid and one diamine, or only one lactam; for copolyamides, at least two diacids or two diamines, or two Lactam. Preferably, the polyamide (PA) is selected from PA6, PA66, PA45, PA56, PA10, PA1010, PA11 or PA12; or the copolymerization condensates of various diamines and diacids, such as adipic acid, dodecyl Copolycondensation polymer of diacid, hexamethylenediamine and dodecyldiamine.

Further, the polyoxymethylene is homopolyoxymethylene or copolyoxymethylene, preferably a homopolymer of trioxane or a copolymer of trioxane, dioxane and other epoxy compounds.

Further, the polyurethane is selected from the polycondensation products of diols and diisocyanates, such as polyester diols, polyether diols, polycarbonate diols, etc. with diphenylmethane diisocyanate, hexamethylene Polycondensation products of diisocyanates and the like.

Further, the core layer and the skin layer of the fiber have good compatibility, preferably the same kind of polymer.

The melt index of the above polymer is 0.5-10 g/10min, preferably 1-8 g/10min.

The present invention will be further described in detail below through specific embodiments, but it should not be understood that the scope of the present invention is limited to the following examples. Without departing from the above-mentioned method idea of the present invention, various substitutions or changes made according to common technical knowledge in the art and conventional means should all be included within the scope of the present invention.

Example 1 (Preparation of fibers with sheath-core structure)

The skin layer polymer is a propylene copolymer containing ethylene and butene, with a melt index of 2.8 g/10min and a melting point T _m1 (measured by DSC) of 134°C.

The polymer of the core layer is a propylene homopolymer with a melt index of 2.8 g/10min and a melting point T _m2 (measured by DSC) of 163°C.

(1) The skin layer polymer and the core layer polymer are respectively injected into a single-screw extruder with a heating device for melt plasticization, and the corresponding screw plasticizing section temperatures are T _p1 and T _p2 respectively, wherein: T _m1 +30≤T _p1 ≤T _m1 +50, T _m1 +50≤T _p2 ≤T _m1 +90;

(2) The melts formed in the step (1) are respectively accurately measured by gear pumps, and the volume ratio of the skin layer polymer and the core layer polymer is controlled to be 1/9 to 9/1, and then passed through the bicomponent spinning assembly. And the spinneret spit out into strands;

(3) After bunching and oiling the filaments spit out in step (2), they are wound at a speed of 500-2500 m/min to obtain pre-oriented filaments, and then drawn and heat-set to obtain the skin-core structure. The fiber is a skin-core composite fully oriented fiber with a monofilament linear density of 2 to 12 dtex; wherein the drawing temperature and the heat setting temperature are T _d and T _s respectively, where: (T _g1 +T _m1 )/2≤T _d ≤(T _g2 +T _m2 )/2, T _d ≤T _s ≤(T _g2 +T _m2 )/2, T _g1 and T _g2 are the glass transition temperatures of the skin layer polymer and the core layer polymer, respectively; followed by , the drafting ratio is 1.5 to 4.5 times, and the thermal setting ratio is 0.9 to 1.1 times.

Example 2 (Preparation of fibers with sheath-core structure)

Step (1) and (2) are with embodiment 1, and step (3) is replaced by:

Spinning, heat-setting and winding at a speed of 2500-4500 m/min are performed on the filaments spun out in step (2) after being bundled and oiled to obtain the fibers of the skin-core structure, where the linear density of the monofilament is 2 A skin-core composite fully oriented yarn of ~12dtex; wherein, the heat setting temperature is T _s , (T _g1 +T _m1 )/2≤T _s ≤(T _g2 +T _m2 )/2, and T _g1 and T _g2 are respectively is the glass transition temperature of the skin layer polymer and the core layer polymer; secondly, the heat setting magnification is 0.85 to 1.15 times.

Example 3 (Preparation of fibers with sheath-core structure)

The steps are the same as in Example 1, except that the skin layer polymer and the core layer polymer are respectively replaced by:

Skin layer polymer: polyamide, melt index is 2.8g/10min, and its melting point T _m1 (measured by DSC) is 130°C;

Core layer polymer: polyamide, with a melt index of 2.8 g/10min and a melting point T _m2 (measured by DSC) of 154°C.

Example 4 (preparation of fibers with sheath-core structure)

The steps are the same as in Example 2, except that the skin layer polymer and the core layer polymer are respectively replaced by:

Skin layer polymer: polyamide, melt index is 2.8g/10min, and its melting point T _m1 (measured by DSC) is 130°C;

Core layer polymer: polyamide, with a melt index of 2.8 g/10min and a melting point T _m2 (measured by DSC) of 154°C.

The strength of the fibers prepared in Examples 1-4 is 300-600 MPa, and the elongation at break is 15-30%.

Example 5 (preparation of unidirectional cloth)

The fibers of the sheath-core structure prepared in Example 1 were unidirectionally arranged, unwound on the creel, and passed through the godet roll, tension roll, yarn splitter, heat roll, cooling zone, pulling roll and winding device in sequence. , forming the unidirectional cloth under the action of hot pressing; wherein, the godet roll, tension roll and traction roll are five rolls or seven rolls, and the heat roll is one pair or two pairs; the rolls of the heat roll The surface temperature ( _ie , the hot pressing temperature) is Tr, and T _m1 ≤ _Tr <T _m2 ; the cooling zone can adopt natural cooling or blast cooling.

Example 6-8 (preparation of unidirectional cloth)

The procedure was the same as that of Example 5, except that the fibers of Examples 2-4 were respectively replaced with the fibers.

Example 9 (Preparation of Laminate)

The unidirectional fabrics in Examples 5-8 were used to process the laminates by hot pressing, and the fibers between each two layers of fabrics intersected at 90° C. The results are listed in Table 1.

Composition and Processing Method of Laminates in Table 1 Example 9

Example 10 (Preparation of Tubes)

The fibers in Example 1 were continuously wound on a cylindrical mold, and a tube was prepared by hot pressing (10 MPa, 130° C.), and the prepared tube could withstand a maximum static pressure of 300 MPa.

Example 11 (Preparation of Tubes)

The fibers in Example 3 were continuously wound on a cylindrical mold, and a tube was prepared by hot pressing (10 MPa, 130° C.), and the prepared tube could withstand a maximum static pressure of 360 MPa.

Claims (48)

1. A unidirectional cloth, characterized in that, the unidirectional cloth is prepared from a fiber of a skin-core structure; wherein, the diameter of the fiber of the skin-core structure is between 0.5 μm-60 μm; The polymer species of the layer and the skin layer are the same or different, and are independently selected from the following polymers: polyolefin, polyamide, polyurethane, polyester, polyoxymethylene; the melting point T _m1 of the skin layer polymer and the melting point T of the core layer polymer _m2 satisfies the following relation: T _m2 >T _m1 (1); Wherein, the fibers of the skin-core structure are skin-core composite fully oriented fibers with a monofilament linear density of 2-12 dtex; Wherein, the fiber of the skin-core structure is prepared by a method comprising the following steps: (1) The skin layer polymer whose melting point is T _m1 and the core layer polymer whose melting point is T _m2 are respectively injected into a single-screw extruder with a heating device for melt plasticization, and the corresponding screw plasticizing section temperature are T _p1 and T _p2 respectively, wherein: T _m1 +30≤T _p1 ≤T _m1 +50, T _m1 +50≤T _p2 ≤T _m1 +90; (2) The melts formed in the step (1) are respectively accurately measured by gear pumps, and the volume ratio of the skin layer polymer and the core layer polymer is controlled to be 1/9 to 9/1, and then passed through the bicomponent spinning assembly. And the spinneret spit out into strands; (3a) After bundled and oiled, the filaments spun out in step (2) are coiled at a speed of 500-2500 m/min to obtain pre-oriented filaments, and then drawn and heat-set to obtain the skin-core structure. Fiber, which is a sheath-core composite fully oriented yarn with a monofilament linear density of 2 to 12 dtex; or, (3b) Spinning, heat-setting, and winding the filaments spun out in step (2) at a speed of 2500-4500 m/min after bundling and oiling, to obtain the fibers of the skin-core structure, which are monofilament threads Skin-core composite fully oriented yarn with a density of 2 to 12dtex; In step (3a), the drawing temperature and the heat setting temperature are T _d and T _s respectively, where: (T _g1 +T _m1 )/2≤T _d ≤(T _g2 +T _m2 )/2, T _d ≤T _s ≤(T _g2 +T _m2 )/2, T _g1 and T _g2 are the glass transition temperatures of the skin layer polymer and the core layer polymer, respectively; In step (3b), the heat setting temperature is T _s , (T _g1 +T _m1 )/2≤T _s ≤(T _g2 +T _m2 )/2, and T _g1 and T _g2 are the skin layer polymer and the core layer polymer, respectively. glass transition temperature of the substance. 2. The unidirectional fabric according to claim 1, wherein the melting point T _m1 of the skin layer polymer and the melting point T _m2 of the core layer polymer satisfy the following relational expression: T _m2 ≥ T _m1 +10(1'). 3. The unidirectional fabric according to claim 2, wherein the melting point T _m1 of the skin layer polymer and the melting point T _m2 of the core layer polymer satisfy the following relational expression: T _m2 ≥ T _m1 +20(1"). 4. The unidirectional fabric according to claim 3, wherein the melting point T _m1 of the skin layer polymer and the melting point T _m2 of the core layer polymer satisfy the following relational expression: T _m2 ≥ T _m1 +30(1"'). 5. The unidirectional fabric according to any one of claims 1-4, wherein the range of T _m1 is between 30-300°C; the range of _Tm2 is between 60-300°C. 6. The unidirectional fabric according to any one of claims 1-4, wherein the diameter of the fibers is between 1 μm and 60 μm. 7. The unidirectional fabric according to claim 6, wherein the diameter of the fibers is between 5 μm and 60 μm. 8. The unidirectional fabric according to claim 7, wherein the diameter of the fibers is between 10 μm and 60 μm. 9. The unidirectional fabric according to any one of claims 1-4, wherein the mass of the skin layer accounts for 5-60 wt% of the total mass of the fiber. 10. The unidirectional fabric according to claim 9, wherein the mass of the skin layer accounts for 5-50 wt% of the total mass of the fiber. 11. The unidirectional fabric according to any one of claims 1-4, wherein the polyolefin is selected from polyethylene; polypropylene; polybutene-1; ethylene copolymer, the comonomers of which are propylene, butylene one or more of ene, pentene, hexene, or octene; propylene copolymers whose comonomers are one or more of ethylene, butene, pentene, hexene, or octene; or, Butene copolymer whose comonomer is one or more of ethylene, propylene, pentene, hexene or octene; Described polyester is the condensation product of dibasic acid and dibasic alcohol, or the ring-opening polymer of lactone; The polyamide is a condensate of a dibasic acid and a dibasic amine, or a ring-opening polymer of a lactam; Described polyoxymethylene is homopolyoxymethylene or copolyoxymethylene; The polyurethane is selected from the polycondensation products of diols and diisocyanates. 12. The unidirectional fabric according to claim 11, wherein the polyester is obtained by homopolymerization or copolymerization; for homopolymerization polyester, only one dibasic acid and one dihydric alcohol, or only one A lactone; for copolyesters, at least two diacids or two diols, or two lactones. 13. The unidirectional fabric of claim 12, wherein the polyester is selected from polyethylene terephthalate, polybutylene terephthalate, or blends thereof. 14. The unidirectional fabric according to claim 11, wherein the polyamide is obtained by homopolymerization or copolymerization; for the homopolymeric polyamide, only one diacid and one diamine, or only one A lactam; for copolyamides, at least two diacids or two diamines, or two lactams. 15. The unidirectional fabric according to claim 14, wherein the polyamide (PA) is selected from PA6, PA66, PA45, PA56, PA10, PA1010, PA11 or PA12; or selected from adipic acid, dodecyl Copolycondensation polymer of diacid, hexamethylenediamine and dodecyldiamine. 16. The unidirectional fabric according to claim 11, wherein the polyoxymethylene is a homopolymer of trioxane or a copolymer of trioxane, dioxane and other epoxy compounds. 17. The unidirectional fabric according to claim 11, wherein the polyurethane is selected from at least one of polyester diol, polyether diol, polycarbonate diol and diphenylmethane diisocyanate, A polycondensation product of at least one of hexamethylene diisocyanate. 18. The unidirectional fabric according to any one of claims 1-4, wherein the core layer and the skin layer of the fibers have the same polymer species. 19. The unidirectional cloth according to claim 1, wherein the unidirectional cloth is prepared by the following method: the fibers are unidirectionally arranged, and the unidirectional cloth is formed under the action of hot pressing, wherein the heat is controlled The pressure temperature is lower than T _m2 . 20. A laminate, characterized in that the laminate is obtained by laminating at least two layers of the unidirectional fabrics according to any one of claims 1-19 in sequence and then hot pressing; The overlapping angle α of the cloths satisfies the following formula: 0≤α≤90°, and the angle α refers to the included angle between the longitude directions of two unidirectional cloths. 21. The laminate according to claim 20, wherein the laminate is obtained by laminating 2-2000 layers of unidirectional fabrics in sequence and then hot pressing. 22. The laminate according to claim 21, wherein the laminate is obtained by laminating 2-100 layers of unidirectional fabrics in sequence and then hot pressing. 23. The laminate according to claim 22, wherein the laminate is obtained by laminating 5-50 layers of unidirectional fabrics in sequence and then hot pressing. 24. The laminate according to claim 23, wherein the laminate is obtained by laminating 10-20 layers of unidirectional fabrics in sequence and then hot pressing. 25. The laminate of claim 20, wherein the hot pressing temperature is below _Tm2 . 26. The laminate of claim 25, wherein the hot pressing temperature is equal to the _Tm1 . 27. The laminate according to claim 20, wherein the pressure of the hot pressing is 0.5 MPa to 30 MPa. 28. The laminate according to any one of claims 20-27, wherein the laminate has a thickness between 100 μm and 200 mm. 29. The laminate of claim 28, wherein the laminate has a thickness between 2 mm and 50 mm. 30. A tube, characterized in that, the tube is obtained by hot pressing after continuously winding the fibers of the sheath-core structure in the unidirectional fabric according to any one of claims 1 to 18 on a cylindrical mold. 31. The tube of claim 30, wherein the hot pressing temperature is below _Tm2 . 32. The tube of claim 31, wherein the autoclaving temperature is equal to the _Tm1 . 33. The tube according to claim 30, wherein the pressure of the hot pressing is 0.5 MPa to 30 MPa. 34. The tube of any one of claims 30-33, wherein the tube has a wall thickness between 100 μm and 200 mm. 35. The tube of claim 34, wherein the tube has a wall thickness of between 2 mm and 50 mm. 36. The method for preparing a unidirectional fabric according to any one of claims 1-19, characterized in that the method comprises the following steps: preparing fibers of a skin-core structure; forming the unidirectional cloth under the action; Wherein, preparing the fiber of the skin-core structure includes the following steps: (1) The skin layer polymer whose melting point is T _m1 and the core layer polymer whose melting point is T _m2 are respectively injected into a single-screw extruder with a heating device for melt plasticization, and the corresponding screw plasticizing section temperature are T _p1 and T _p2 respectively, wherein: T _m1 +30≤T _p1 ≤T _m1 +50, T _m1 +50≤T _p2 ≤T _m1 +90; (2) The melts formed in the step (1) are respectively accurately measured by gear pumps, and the volume ratio of the skin layer polymer and the core layer polymer is controlled to be 1/9 to 9/1, and then passed through the bicomponent spinning assembly. And the spinneret spit out into strands; (3a) After bundled and oiled, the filaments spun out in step (2) are coiled at a speed of 500-2500 m/min to obtain pre-oriented filaments, and then drawn and heat-set to obtain the skin-core structure. Fiber, which is a sheath-core composite fully oriented yarn with a monofilament linear density of 2 to 12 dtex; or, (3b) Spinning, heat-setting, and winding the filaments spun out in step (2) at a speed of 2500-4500 m/min after bundling and oiling, to obtain the fibers of the skin-core structure, which are monofilament threads Skin-core composite fully oriented yarn with a density of 2 to 12dtex; In step (3a), the drawing temperature and the heat setting temperature are T _d and T _s respectively, where: (T _g1 +T _m1 )/2≤T _d ≤(T _g2 +T _m2 )/2, T _d ≤T _s ≤(T _g2 +T _m2 )/2, T _g1 and T _g2 are the glass transition temperatures of the skin layer polymer and the core layer polymer, respectively; In step (3b), the heat setting temperature is T _s , (T _g1 +T _m1 )/2≤T _s ≤(T _g2 +T _m2 )/2, and T _g1 and T _g2 are the skin layer polymer and the core layer polymer, respectively. glass transition temperature of the substance. 37. The preparation method according to claim 36, wherein in step (3a), the drafting ratio is 1.5-4.5 times, and the heat-setting ratio is 0.9-1.1 times. 38. The preparation method according to claim 36, wherein in step (3b), the thermal setting magnification is 0.85-1.15 times. 39. The preparation method according to claim 36, wherein when the unidirectional cloth is formed under the action of hot pressing, the temperature of the hot pressing is controlled to be lower than T _m2 . 40. preparation method according to claim 36, wherein, described preparation method specifically comprises the following steps: The fibers of the sheath-core structure are prepared according to the method of claim 36; The fibers of the skin-core structure are unidirectionally arranged, unwind on the creel, pass through the godet roll, tension roll, yarn separator, hot roll, cooling zone, pulling roll and winding device in sequence, and then pass through the hot pressing. The unidirectional cloth is formed under the action, wherein the hot pressing temperature is controlled to be lower than T _m2 . 41. The preparation method according to claim 40, wherein the godet roll, the tension roll and the pulling roll are five rolls or seven rolls, and the heat rolls are one pair or two pairs. 42 . The production method according to claim 40 , wherein the roll surface temperature of the hot roll, that is, the hot pressing temperature, is Tr , and T _{m1 ≦ Tr} <T _m2 . 43. The preparation method according to claim 40, wherein the cooling zone adopts natural cooling or blast cooling. 44. The method for preparing a laminate according to any one of claims 20-29, wherein the method comprises the steps of: preparing a unidirectional fabric according to the method according to any one of claims 36-43; Two layers of the unidirectional fabrics are stacked in sequence and then hot-pressed to prepare the laminate. 45. The method for preparing a pipe according to any one of claims 30-35, characterized in that the method comprises the steps of: preparing the fibers of the sheath-core structure according to the method according to any one of claims 36-43. The method is to prepare the fiber of the sheath-core structure; the prepared fiber of the sheath-core structure is continuously wound on a cylindrical mold and obtained by hot pressing. 46. The use of the unidirectional cloth according to any one of claims 1-19, which is used in the fields of pallets, boxes, construction, and vehicles, and used as a force-bearing part or a decorative part. 47. Use of the laminate according to any one of claims 20-29, in the fields of pallets, boxes, construction, and vehicles, as a stress-bearing part or a decorative part. 48. Use of the pipe according to any one of claims 30 to 35, in the fields of pallets, boxes, construction, vehicles, as a force-bearing part or a decorative part.

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