A full-biodegradable sheath-core composite fiber and a preparation method thereof

Abstract

The present application relates to a kind of full biodegradable sheath-core composite fiber and its preparation method, preparation method: biodegradable polyester mixed with thermoplastic starch is used as sheath layer raw material, polylactic acid is used as core layer raw material, according to sheath-core composite spinning process, full biodegradable sheath-core composite fiber is prepared;Product: sheath layer is biodegradable polyester, thermoplastic starch is mixed in biodegradable polyester, core layer is polylactic acid;The content of thermoplastic starch in biodegradable polyester is not more than 2wt%.The present application uses biodegradable polyester with excellent softness as sheath layer, polylactic acid as core layer, gives full play to the low melting point adhesion of sheath layer component and the skeleton support effect of core layer, and introduce thermoplastic starch in sheath layer to promote the crystallization performance of biodegradable polyester in sheath layer, improve processability;Full biodegradable sheath-core composite fiber spun by the present application has skin-friendly softness, good hot air bonding, realizes the unity of application performance and biodegradability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biodegradable fibers, and relates to a full-biodegradable skin-core composite fiber and a preparation method thereof. BACKGROUND

[0002] With the improvement of living standards and the rapid expansion of the non-woven industry, the filling cushion material has entered an updating stage. The traditional polyurethane foam material is obviously limited in the field with high safety and comfort requirements due to poor air permeability and heat dissipation, easy aging, and the generation of hydrogen cyanide toxic gas during combustion. In recent years, the emergence of polyester three-dimensional non-woven material (also known as upright cotton) provides people with a better choice. Generally, polyester fiber and low-melting-point fiber are used as raw materials, and after mixed carding and vertical laying, a multi-void three-dimensional structure is formed by hot air melting and bonding. The fiber aggregate can present a sponge-like resilience and pressure resistance, and effectively improve the poor water permeability and air permeability caused by the poor interconnection of the polyurethane foam sponge. At the same time, the bulkiness, unit weight, anti-aging, product safety and environmental protection performance, and production cleanliness are also comprehensively improved. At present, polyester upright cotton has been widely used in the fields of home textiles, automotive interiors, underwear, sports goods and medical health, and has replaced polyurethane foam material, with a broad market prospect.

[0003] Low-melting-point fiber is the core raw material for preparing polyester upright cotton, and plays a decisive role in the resilience and air permeability of the product. It is also a hot spot in the development of new chemical fiber products. From the analysis of skin-core composite low-melting-point fiber, the skin layer mainly plays a bonding role in application, and the core layer plays a mechanical support role to ensure that the composite fiber has certain mechanical strength. The skin-core composite low-melting-point fiber is applied by hot air processing, and the three-dimensional structure of the product is realized by the contact bonding between the fibers and the skin layer. Therefore, the bonding performance between the fibers, especially the bonding strength, has a great influence on the three-dimensional non-woven product.

[0004] Chinese invention patent CN112981610A discloses an environmentally friendly hydrophilic low-melting PET composite fiber, which has a skin-core structure. The skin layer is a modified environmentally friendly hydrophilic low-melting PET, and the core layer is an environmentally friendly polyester chip, which has good water absorption performance and bonding performance. The bonding properties between the fibers mainly depend on the fact that the composite fibers are based on polyester, which has good thermodynamic compatibility.

[0005] Chinese invention patent CN114262954A relates to a low-melting polyester fiber and its application in natural fiber bonding. In order to achieve good bonding strength between low-melting polyester fiber and natural fiber, aluminum oxide is added as a thermal conductive filler in low-melting polyester, which helps to improve the thermal conductivity of low-melting fiber. When the mass addition amount of aluminum oxide is 2-3%, the thermal conductivity of low-melting fiber can be increased by 8-10%. Due to the improvement of thermal conductivity, the heating speed of low-melting fiber during hot baking can be increased to some extent, thereby increasing the melting amount and improving the bonding effect of low-melting fiber.

[0006] Chinese invention patent CN114775105A discloses a preparation method of isomeric polyester sheath-core composite fiber. The composite fiber is prepared by low-melting polyester and block copolymer sheath-core composite spinning. The sheath layer of the composite fiber includes low-melting polyester and pre-activated polymer, and the core layer is block copolymer. The composite fiber is activated to prepare isomeric polyester sheath-core composite fiber. The isomeric polyester sheath-core composite fiber is formed by hot air. The main components of the sheath layer and the core layer are both polyester, which has good interface compatibility. The composite fiber is activated by a certain alkaline aqueous solution. The surface of the activated composite fiber forms a microporous structure with a diameter of 0.1-1.0 microns and a large number of reactive groups. In the hot air bonding of isomeric polyester sheath-core composite fiber, the contact area between fibers is increased, and the reactive groups further react with the fiber surface, which comprehensively improves the bonding strength and enables the application in non-woven high-resilience textiles.

[0007] With the development of the times, people pay more attention to environmental problems and are interested in green and environmentally friendly fibers. Developing composite fibers with biodegradable properties is an important direction.

[0008] Chinese invention patent CN115094541A discloses a low-bonding biodegradable sheath-core composite copolyester fiber and its preparation method. The low-bonding biodegradable sheath-core composite copolyester fiber has a sheath-core composite structure. The sheath layer is PLA, PBS, PVA, PCL, PGA or PHA. The core layer is PBAT, PBST, PBSF or PBAF. The melt index MI of the sheath layer and the core layer at the same temperature differs by no more than 15 g / min. The low-bonding biodegradable sheath-core composite copolyester fiber is prepared, but the bonding property of the sheath layer is sacrificed, which limits its application range.

[0009] Chinese invention patent CN111979605B discloses a method for processing composite fibers using multi-component biodegradable polymers. The sheath component comprises 50% low-melting-point amorphous polylactic acid (COPLA), 30% polycaprolactone (PCL), and 20% polybutylene succinate (PBS); the core component comprises 70% high-melting-point polylactic acid (PLA) in any crystalline form, 20% polyhydroxyalkanoates (PHA / B), and 10% polybutylene terephthalate (PBAT). This invention processes core-sheath type composite fibers by mixing and melting multi-component biodegradable polymers as core-sheath raw materials. The compatibility of each polymer component is utilized to compensate for the deficiencies of single components, resulting in biodegradable composite fibers with better performance. However, while blending multiple components improves interfacial compatibility, the complex composition makes it prone to thermal degradation under high shear stress in twin-screw extrusion. During spinning and stretching, the different crystallization rates and stretching orientations of each component can easily lead to broken fibers and reduced fiber strength, affecting the mechanical properties of the final product.

[0010] Therefore, it is of great significance to study a fully biodegradable core-sheath composite fiber and its preparation method, so as to simultaneously possess excellent mechanical properties, biodegradability, excellent adhesive properties and good compatibility. Summary of the Invention

[0011] The purpose of this invention is to solve the problems existing in the prior art and to provide a fully biodegradable core-sheath composite fiber and its preparation method.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A fully biodegradable core-sheath composite fiber comprises a biodegradable polyester sheath containing thermoplastic starch (TPS) and a polylactic acid (PLA) core. PLA combines biodegradability with excellent mechanical strength, serving as a support for the core. The polyhydroxy structure of the TPS in the sheath forms hydrogen bonds with the carbonyl groups in the PLA core, resulting in physical cross-linking and intermolecular forces at the sheath-core interface, thus enhancing the interfacial bonding between the sheath and core. Furthermore, the polyhydroxy structure of the thermoplastic starch added to the sheath forms hydrogen bonds with the carbonyl structure of the bonded polyester, improving physical adsorption and thus enhancing the adhesive properties of the sheath through these intermolecular interactions.

[0014] The content of the thermoplastic starch in the biodegradable polyester is not more than 2 wt%; when the content of the TPS increases to more than 2 wt%, the TPS is more likely to form intermolecular hydrogen bonds, and agglomeration and microphase separation occur, and it is not easy to form hydrogen bond with the polyester to produce physical crosslinking structure; when a small amount of TPS is added, the TPS is uniformly dispersed in the biodegradable polyester and no obvious agglomeration phenomenon occurs, and the TPS can play the role of a nucleating agent in the cooling and crystallization process to improve the crystallization performance of the biodegradable polyester; as the content of the TPS increases to more than 2 wt%, the agglomeration of the TPS is obvious, and the TPS and the biodegradable polyester undergo microphase separation, and the TPS cannot effectively play the role of a nucleating agent;

[0015] The full biodegradable sheath-core composite fiber has a fineness of 0.5-5.5 dtex, a compost biodegradation rate of ≥60%, a disintegration degree of ≥90%, a breaking strength of ≥2.0 cN / dtex, a fiber modulus of 40-80 cN / dtex, and excellent fiber compression resilience with an elastic recovery rate of ≥80%; the sheath bonding strength of the full biodegradable sheath-core composite fiber is increased by 20-50% compared with a comparative sample, and the full biodegradable sheath-core composite fiber is basically the same as the comparative sample, except that the biodegradable polyester does not contain thermoplastic starch.

[0016] As a preferred technical solution:

[0017] The full biodegradable sheath-core composite fiber as described above has a content of the thermoplastic starch in the biodegradable polyester of 0.2-2 wt%.

[0018] The full biodegradable sheath-core composite fiber as described above has a melting point of the thermoplastic starch of 120-130℃, and a melt index of 10-20 g / 10 min under the condition of 190℃ / 2.16 kg.

[0019] The full biodegradable sheath-core composite fiber as described above has an intrinsic viscosity of the biodegradable polyester of 0.80-1.20 dL / g, and a melt index of 15-30 g / 10 min under the condition of 190℃ / 2.16 kg.

[0020] The full biodegradable sheath-core composite fiber as described above has a biodegradable polyester of polybutylene succinate (PBS), polybutylene adipate / terephthalate (PBAT), or polybutylene succinate terephthalate (PBST).

[0021] The full biodegradable sheath-core composite fiber as described above has a melting point of the polylactic acid of 125-180℃, and a melt index of 15-25 g / 10 min under the condition of 190℃ / 2.16 kg.

[0022] A full biodegradable sheath-core composite fiber as described above, the mass ratio of the sheath layer to the core layer is 4:6-6:4.

[0023] The application also provides a preparation method of the full biodegradable sheath-core composite fiber as described above, wherein biodegradable polyester mixed with thermoplastic starch is used as the sheath layer raw material, polylactic acid is used as the core layer raw material, and the full biodegradable sheath-core composite fiber is prepared according to a sheath-core composite spinning process.

[0024] As a preferred technical solution,

[0025] The preparation method of the full biodegradable sheath-core composite fiber as described above, wherein the spinning process parameters are as follows: the spinning temperature is 190-210 DEG C, the spinning speed is 500-2000 m / min, and the total draft ratio is 3.5-6.0 times.

[0026] Invention principle

[0027] The application adopts biodegradable polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT) or polybutylene terephthalate (PBST) as the sheath layer, polylactic acid as the core layer, is dried respectively, is extruded into a melt in a respective screw extruder, and is spun, is cooled by circular blowing, is wound and is formed into a double-component sheath-core structure fiber. The sheath layer is a polyester with biodegradable performance, is more flexible compared to conventional PET polyester or polylactic acid, and the corresponding fiber material is more comfortable to the human body. Using PBS, PBAT or PBST as the sheath layer can significantly improve the skin friendliness of the spun fiber during contact with the human body; the core layer polylactic acid plays a role of skeleton support, and ensures that the composite fiber has good mechanical strength.

[0028] PBS, PBAT or PBST Although the sheath has many advantages, the problems in the spinning of the sheath-core composite fiber mainly focus on the weak crystallization performance of the biodegradable polyester, and the poor compatibility of the composite interface when the biodegradable polyester is compounded with polylactic acid due to the large difference in thermodynamic properties. The sheath-core composite fiber cannot realize coaxial stretching in the processing, the fiber spinnability is reduced, and the fiber mechanical strength is low. A small amount of thermoplastic starch is introduced into the biodegradable polyester in the sheath. Thermoplastic starch has been proved to have very excellent degradation, including hydrolysis and biodegradation, and will not adversely affect the degradation of biodegradable polyester. Thermoplastic starch is introduced into the sheath as a heterogeneous component, which plays a role as a nucleating agent in the cooling crystallization process, and improves the crystallization performance of the biodegradable polyester. At the same time, the branched structure of thermoplastic starch has a strong molecular chain hydrogen bond, which improves the interface bonding force of the sheath and the core, and further improves the performance of the sheath-core composite fiber. The spun sheath-core composite fiber has low melting point characteristics in the post-processing hot air forming process, and the thermoplastic starch contained in the sheath further strengthens the bonding strength, so that the fiber is not easy to separate during the preparation process, and the performance is more excellent.

[0029] In the prior art, thermoplastic starch is usually used as a filler for thin films or plastic products, and is added to polyester in an amount of more than 10wt% (usually 30-50%). The purpose is to maintain the biodegradation rate while reducing the application cost of biodegradable polyester. However, due to the incompatibility of TPS and polyester, most of the prior art focuses on the modification of TPS to improve the interfacial compatibility of the two, prevent the occurrence of microphase separation, and achieve the reduction of production cost while improving the mechanical properties of biodegradable polyester. In addition, the improvement of the mechanical properties of biodegradable polyester requires modification of TPS, which cannot be achieved simply by adding a high content of TPS.

[0030] In the present application, a small amount (≤2wt%) of thermoplastic starch is introduced into the biodegradable polyester. First, the multi-hydroxyl structure of TPS can form a physical cross-linking structure with the carbonyl group of polyester, increase the intermolecular force, inhibit the thermal degradation of polyester during high-temperature processing, increase the molecular weight of the blend, narrow the molecular weight distribution, and improve the processing thermal stability of polyester, and improve the spinnability of PBAT. Secondly, TPS can act as a nucleating agent for PBAT, improving the crystallization temperature and rate of PBAT, and improving the mechanical properties of PBAT. Unlike the prior art, due to the hydrophobicity of polyester and the hydrophilicity of TPS, the two are not compatible by themselves. The present application adds a small amount of TPS, and the microphase separation phenomenon is not obvious when a small amount of TPS is added. If a high content of TPS is added, the microphase separation phenomenon will occur, which will reduce the mechanical properties and spinnability of the mixture.

[0031] Advantages:

[0032] (1) The full biodegradable sheath-core composite fiber of the present application uses a biodegradable polyester with excellent softness as the sheath layer, and polylactic acid as the core layer, so that the low-melting-point adhesion of the sheath layer component and the skeleton support of the core layer are fully utilized;

[0033] (2) The full biodegradable sheath-core composite fiber of the present application introduces thermoplastic starch into the sheath layer to promote the crystallization performance of the biodegradable polyester in the sheath layer, improve the processability, and not adversely affect the degradation performance of the biodegradable polyester; the thermoplastic starch has a branched structure with multiple hydroxyl functional groups, has a strong molecular chain hydrogen bond effect, and at the same time improves the bonding force of the composite interface between the sheath layer and the core layer, realizes synchronous stretching of the sheath and core components under the same process, and makes the full biodegradable sheath-core composite fiber have good mechanical properties;

[0034] (3) The full biodegradable sheath-core composite fiber of the present application has skin-friendly softness, good hot air adhesion, and realizes the unity of application performance and biodegradability;

[0035] (4) The preparation method of the full biodegradable sheath-core composite fiber of the present application does not harm the spinnability, and the thermoplastic starch contained in the sheath layer strengthens the adhesion strength, improves the related application performance of the fiber in the one-time sanitary textile after hot air forming. DETAILED DESCRIPTION

[0036] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. In addition, it should be understood that those skilled in the art can make various modifications or changes to the present application after reading the content taught by the present application, and these equivalent forms also fall within the scope defined by the claims attached hereto.

[0037] The test standards / test methods related to the present application are as follows:

[0038] Compost biodegradation rate: tested according to GB / T 19277.1-2011;

[0039] Degree of disintegration: tested according to GB / T 19811-2005;

[0040] Breaking strength: tested according to GB / T 14344-2022;

[0041] Fiber modulus: tested according to GB / T 14344-2022;

[0042] Elastic recovery rate: tested according to FZT50007-2012;

[0043] Adhesion strength: the adhesion strength of the full biodegradable sheath-core composite fiber was evaluated with reference to GB7124-1986, the polyester fabric sample was cut, the size of the polyester fabric sample was 10mm*2.5mm, 20mg of the fiber sample was weighed; one of the two cut polyester fabric samples was placed on the hot table and heated to the melting point of the polylactic acid in the fiber sample, the fiber sample was placed at one end of the polyester fabric sample, when the fiber sample began to deform, the other polyester fabric sample was placed on the sample, a circular column was used to apply a pressure of 13N to make the polyester fabric sample and the fiber sample adhere together, and then the temperature was quickly lowered to room temperature to achieve the effect of hot melt adhesion; in order to facilitate subsequent calculation of the adhesion area, the contact surface of the fiber sample and the polyester fabric sample was as circular as possible, a universal testing machine was used to test the adhesion strength of the full biodegradable fiber, each fiber sample was tested five times, and the average value was taken, the tensile speed of the universal testing machine Instron5566 was 10mm / min.

[0044] Example 1

[0045] A preparation method of a full biodegradable sheath-core composite fiber, the specific steps are as follows:

[0046] (1) Preparation of raw materials:

[0047] Thermoplastic starch: manufacturer: Dongguan Jingke High Polymer Material Co., Ltd., brand: THJS-7801, melting point: 120℃, melt index under the condition of 190℃ / 2.16kg: 20g / 10min;

[0048] Biodegradable polyester: polybutylene succinate, manufacturer: Xinjiang Lanshan Tunhe Chemical Co., Ltd., brand: TH803S, intrinsic viscosity: 1.20dL / g, melt index under the condition of 190℃ / 2.16kg: 20-30g / 10min;

[0049] Polylactic acid: manufacturer: Anhui Fengyuan Futai Lai Polylactic Acid Co., Ltd., brand: 6202D, melting point: 180℃, melt index under the condition of 190℃ / 2.16kg: 15-18g / 10min;

[0050] (2) The biodegradable polyester mixed with the thermoplastic starch was used as the sheath layer raw material, and the polylactic acid was used as the core layer raw material, and a full biodegradable sheath-core composite fiber was prepared according to the sheath-core composite spinning process;

[0051] Among them, the content of the thermoplastic starch in the biodegradable polyester is 0.2wt%; the mass ratio of the sheath layer to the core layer is 4:6;

[0052] The spinning process parameters are: spinning temperature 190℃, spinning speed 500m / min, total draw ratio 3.5 times.

[0053] The prepared full biodegradable sheath-core composite fiber has a fineness of 0.5 dtex, a compost biodegradation rate of 60%, a disintegration degree of 94%, a breaking strength of 2 cN / dtex, a fiber modulus of 40 cN / dtex, and an elastic recovery rate of 84%. The sheath bonding strength of the full biodegradable sheath-core composite fiber is increased by 20% compared with the comparative sample. The comparative sample is basically the same as the full biodegradable sheath-core composite fiber, except that the biodegradable polyester does not contain thermoplastic starch.

[0054] Example 2

[0055] A preparation method of a full biodegradable sheath-core composite fiber, the specific steps are as follows:

[0056] (1) Preparation of raw materials:

[0057] Thermoplastic starch: manufacturer: Dongguan Jingke High Polymer Material Co., Ltd., brand: THJS-7801, melting point: 120℃, melt index under the condition of 190℃ / 2.16kg: 20g / 10min;

[0058] Biodegradable polyester: polybutylene adipate-co-terephthalate, manufacturer: Xinjiang Lanshan Tunhe Chemical Co., Ltd., brand: TH801T, intrinsic viscosity: 1.10dL / g, melt index under the condition of 190℃ / 2.16kg: 15-25g / 10min;

[0059] Polylactic acid: manufacturer: Anhui Fengyuan Futai Lai Polylactic Acid Co., Ltd., brand: 6202D, melting point: 180℃, melt index under the condition of 190℃ / 2.16kg: 15-18g / 10min;

[0060] (2) The biodegradable polyester mixed with thermoplastic starch is used as the sheath layer raw material, and the polylactic acid is used as the core layer raw material, and a full biodegradable sheath-core composite fiber is prepared according to the sheath-core composite spinning process;

[0061] The content of thermoplastic starch in the biodegradable polyester is 0.5wt%; the mass ratio of the sheath layer to the core layer is 5:5;

[0062] The spinning process parameters are: spinning temperature 195℃, spinning speed 800m / min, total draw ratio 4 times.

[0063] The prepared full biodegradable sheath-core composite fiber has a fineness of 1.7 dtex, a compost biodegradation rate of 67%, a disintegration degree of 92%, a breaking strength of 2.3 cN / dtex, a fiber modulus of 47 cN / dtex, and an elastic recovery rate of 87%. The sheath bonding strength of the full biodegradable sheath-core composite fiber is increased by 22% compared with the comparative sample. The comparative sample is basically the same as the full biodegradable sheath-core composite fiber, except that the biodegradable polyester does not contain thermoplastic starch.

[0064] Example 3

[0065] A preparation method of a full biodegradable sheath-core composite fiber, the specific steps are as follows:

[0066] (1) Preparation of raw materials:

[0067] Thermoplastic starch: manufacturer: Dongguan Jingke High Polymer Material Co., Ltd., brand: TPS-7012, melting point: 125℃, melt index under the condition of 190℃ / 2.16kg: 12g / 10min;

[0068] Biodegradable polyester: manufacturer: Xinjiang Lanshan Tunhe Chemical Co., Ltd.,

[0069] Polybutylene succinate, brand: TH901T, intrinsic viscosity: 0.80dL / g, melt index under the condition of 190℃ / 2.16kg: 15-25g / 10min;

[0070] Polylactic acid: manufacturer: Zhejiang Haizheng Biological Material Co., Ltd., brand: REVODE110, melting point: 160℃, melt index under the condition of 190℃ / 2.16kg: 20-23g / 10min;

[0071] (2) The biodegradable polyester mixed with thermoplastic starch is used as the sheath layer raw material, and the polylactic acid is used as the core layer raw material. According to the sheath-core composite spinning process, a full biodegradable sheath-core composite fiber is prepared.

[0072] Among them, the content of thermoplastic starch in the biodegradable polyester is 1wt%; the mass ratio of the sheath layer to the core layer is 6:4;

[0073] The spinning process parameters are: spinning temperature 200℃, spinning speed 1000m / min, total draw ratio 4.5 times.

[0074] The prepared full biodegradable sheath-core composite fiber has a fineness of 2.6 dtex, a compost biodegradation rate of 74%, a disintegration degree of 93%, a breaking strength of 2.5 cN / dtex, a fiber modulus of 62 cN / dtex, and an elastic recovery rate of 83%. The sheath bonding strength of the full biodegradable sheath-core composite fiber is increased by 34% compared with the comparative sample. The comparative sample is basically the same as the full biodegradable sheath-core composite fiber, except that the biodegradable polyester does not contain thermoplastic starch.

[0075] Example 4

[0076] A preparation method of a full biodegradable sheath-core composite fiber, the specific steps are as follows:

[0077] (1) Preparation of raw materials:

[0078] Thermoplastic starch: manufacturer: Dongguan Jingke High Polymer Material Co., Ltd., brand: TPS-7012, melting point: 125℃, melt index at 190℃ / 2.16kg: 12g / 10min;

[0079] Biodegradable polyester: polybutylene succinate, manufacturer: Xinjiang Lanshan Tunhe Chemical Co., Ltd., brand: TH803S, intrinsic viscosity: 1.20dL / g, melt index at 190℃ / 2.16kg: 20-30g / 10min;

[0080] Polylactic acid: manufacturer: Zhejiang Haizheng Biomaterial Co., Ltd., brand: REVODE110, melting point: 160℃, melt index at 190℃ / 2.16kg: 20-23g / 10min;

[0081] (2) The biodegradable polyester mixed with thermoplastic starch is used as the sheath layer raw material, and the polylactic acid is used as the core layer raw material, and a full biodegradable sheath-core composite fiber is prepared according to a sheath-core composite spinning process;

[0082] Among them, the content of thermoplastic starch in the biodegradable polyester is 1.5wt%; the mass ratio of the sheath layer to the core layer is 6:4;

[0083] The spinning process parameters are: spinning temperature 200℃, spinning speed 1500m / min, total draw ratio 5 times.

[0084] The prepared full biodegradable sheath-core composite fiber has a fineness of 3.8 dtex, a compost biodegradation rate of 77%, a disintegration degree of 95%, a breaking strength of 2.5 cN / dtex, a fiber modulus of 65 cN / dtex, and an elastic recovery rate of 80%. The sheath bonding strength of the full biodegradable sheath-core composite fiber is increased by 38% compared with the comparative sample. The comparative sample is basically the same as the full biodegradable sheath-core composite fiber, except that the biodegradable polyester does not contain thermoplastic starch.

[0085] Example 5

[0086] A preparation method of a full biodegradable sheath-core composite fiber, the specific steps are as follows:

[0087] (1) Preparation of raw materials:

[0088] Thermoplastic starch: manufacturer: Dongguan Jingke High Polymer Material Co., Ltd., brand: TPS-7012, melting point: 125℃, melt index under the condition of 190℃ / 2.16kg: 12g / 10min;

[0089] Biodegradable polyester: polybutylene adipate-co-terephthalate, manufacturer: Xinjiang Lanshan Tunhe Chemical Co., Ltd., brand: TH801T, intrinsic viscosity: 1.10dL / g, melt index under the condition of 190℃ / 2.16kg: 15-25g / 10min;

[0090] Polylactic acid: Zhejiang Haizheng Biomaterial Co., Ltd., brand: REVODE190, melting point: 125℃, melt index under the condition of 190℃ / 2.16kg: 21-25g / 10min;

[0091] (2) The biodegradable polyester mixed with thermoplastic starch is used as the sheath layer raw material, and the polylactic acid is used as the core layer raw material. According to the sheath-core composite spinning process, a full biodegradable sheath-core composite fiber is prepared.

[0092] Among them, the content of thermoplastic starch in the biodegradable polyester is 1.8wt%; the mass ratio of the sheath layer to the core layer is 4:6;

[0093] The spinning process parameters are: spinning temperature 205℃, spinning speed 1800m / min, total draw ratio 5.5 times.

[0094] The prepared full biodegradable sheath-core composite fiber has a fineness of 4.6 dtex, a compost biodegradation rate of 85%, a disintegration degree of 93%, a breaking strength of 2.6 cN / dtex, a fiber modulus of 77 cN / dtex, and an elastic recovery rate of 86%. The sheath bonding strength of the full biodegradable sheath-core composite fiber is increased by 45% compared with the comparative sample. The comparative sample is basically the same as the full biodegradable sheath-core composite fiber, except that the biodegradable polyester does not contain thermoplastic starch.

[0095] Example 6

[0096] A preparation method of a full biodegradable sheath-core composite fiber, the specific steps are as follows:

[0097] (1) Preparation of raw materials:

[0098] Thermoplastic starch: manufacturer: Suzhou and Plastic Technology Co., Ltd., brand: TPS-7801, melting point: 130℃, melt index at 190℃ / 2.16kg: 10g / 10min;

[0099] Biodegradable polyester: polybutylene succinate, manufacturer: Xinjiang Lanshan Tunhe Chemical Co., Ltd., brand: TH901T, intrinsic viscosity: 0.80dL / g, melt index at 190℃ / 2.16kg: 15-25g / 10min;

[0100] Polylactic acid: manufacturer: Zhejiang Haizheng Biomaterials Co., Ltd., brand: REVODE190, melting point: 125℃, melt index at 190℃ / 2.16kg: 21-25g / 10min;

[0101] (2) The biodegradable polyester mixed with thermoplastic starch is used as the sheath layer raw material, and the polylactic acid is used as the core layer raw material, and a full biodegradable sheath-core composite fiber is prepared according to a sheath-core composite spinning process;

[0102] The content of thermoplastic starch in the biodegradable polyester is 2wt%; the mass ratio of the sheath layer to the core layer is 5:5;

[0103] The spinning process parameters are: spinning temperature 210℃, spinning speed 2000m / min, total draw ratio 6 times.

[0104] The prepared full-biodegradable sheath-core composite fiber has a fineness of 5.5 dtex, a compost biodegradation rate of 90%, a disintegration degree of 90%, a breaking strength of 2.7 cN / dtex, a fiber modulus of 80 cN / dtex, and an elastic recovery rate of 84%. The sheath bonding strength of the full-biodegradable sheath-core composite fiber is 50% higher than that of the comparative sample. The comparative sample is basically the same as the full-biodegradable sheath-core composite fiber, except that the biodegradable polyester does not contain thermoplastic starch.

Claims

1. A fully biodegradable core-sheath composite fiber, characterized in that: The outer layer is made of biodegradable polyester, which contains thermoplastic starch, and the core layer is made of polylactic acid. The content of thermoplastic starch in biodegradable polyester is 0.2–2 wt%. The fineness of the fully biodegradable core-sheath composite fiber is 0.5–5.5 dtex, the composting biodegradation rate is ≥60%, the degree of disintegration is ≥90%, the breaking strength is ≥2.0 cN / dtex, the fiber modulus is 40–80 cN / dtex, and the elastic recovery rate is ≥80%. The sheath bonding strength of the fully biodegradable core-sheath composite fiber is 20–50% higher than that of the control sample. The control sample is basically the same as the fully biodegradable core-sheath composite fiber, except that the biodegradable polyester does not contain thermoplastic starch.

2. The fully biodegradable core-sheath composite fiber according to claim 1, characterized in that, The melting point of thermoplastic starch is 120-130℃, and the melt index at 190℃ / 2.16kg is 10-20g / 10min.

3. The fully biodegradable core-sheath composite fiber according to claim 1, characterized in that, The intrinsic viscosity of biodegradable polyester is 0.80–1.20 dL / g, and the melt index at 190℃ / 2.16 kg is 15–30 g / 10 min.

4. The fully biodegradable core-sheath composite fiber according to claim 3, characterized in that, Biodegradable polyesters are polybutylene succinate, polybutylene adipate / terephthalate, or polybutylene terephthalate succinate.

5. The fully biodegradable core-sheath composite fiber according to claim 1, characterized in that, Polylactic acid has a melting point of 125–180℃ and a melt index of 15–25 g / 10 min at 190℃ / 2.16 kg.

6. The fully biodegradable core-sheath composite fiber according to claim 1, characterized in that, The mass ratio of the cortex to the core is 4:6 to 6:

4.

7. A method for preparing a fully biodegradable core-sheath composite fiber as described in any one of claims 1 to 6, characterized in that: Biodegradable polyester mixed with thermoplastic starch was used as the sheath material, and polylactic acid was used as the core material. Following the sheath-core composite spinning process, a fully biodegradable sheath-core composite fiber was obtained.

8. The method for preparing a fully biodegradable core-sheath composite fiber according to claim 7, characterized in that, The spinning process parameters are: spinning temperature 190~210℃, spinning speed 500~2000m / min, and total draw ratio 3.5~6.0 times.