Sea-island composite superfine fiber and preparation method thereof

Abstract

The invention discloses a sea-island composite superfine fiber and a preparation method thereof, and belongs to the technical field of sea-island fibers. The preparation method comprises the following steps: blending and melting polyvinyl butyral, an antioxidant, polyamide and modified nano titanium dioxide to prepare an island-phase master batch, taking alkali-soluble polyester as a marine-phase master batch, and carrying out melt spinning, stretching treatment, sodium hydroxide alkali liquor splitting and acetone treatment to obtain the sea-island composite superfine fiber with a pore structure. The preparation method comprises the following steps: promoting dispersion by utilizing the hydrogen-bond interaction of modified nano titanium dioxide and polyvinyl butyral, creating pores for the interior of the island fiber by utilizing the interface difference of the dispersed modified nano titanium dioxide in the stretching process, removing a'sea 'component by utilizing alkali liquor, and then, preparing the modified nano titanium dioxide / polyamide composite fiber by utilizing the dissolution difference of polyamide and polyvinyl butyral in acetone. The polyvinyl butyral in the superfine fiber is removed, a pore structure is formed, the superfine fiber which is superfine, high in specific surface area and of a porous structure is prepared, the heat conductivity of the fiber is reduced, and the heat preservation performance is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sea-island fibers, and particularly relates to a sea-island type composite superfine fiber and a preparation method thereof. BACKGROUND

[0002] Thermal materials are of great significance to reduce the heat loss of human body and ensure normal life activities. With the gradual improvement of life quality, thermal materials need to consider lightness and warmth. The current light thermal materials mainly include hollow fibers, down and superfine fibers.

[0003] Superfine fibers have small diameters and high specific surface areas, can divide the air in the material into numerous small pores to store more static air and can efficiently reflect human body radiation. Compared with ordinary fibers, superfine fibers have higher thermal performance under the same mass and have become an important trend in the development of light and efficient thermal materials.

[0004] However, the traditional spinning process is difficult to realize superfine control of fiber diameters <0.5 dtex, and the fiber diameters in the existing superfine thermal materials are still above 10 microns, affecting the lightness and thermal efficiency of the materials. Moreover, further reducing the fiber diameter will reduce the fiber stiffness, making it difficult to maintain a high loft structure and unable to realize long-term thermal application.

[0005] Sea-island type composite superfine fibers use two polymers with different properties as the "island" and "sea" components, respectively. After melt spinning and opening treatment to remove the "sea" component, the remaining "island" component forms a superfine fiber bundle. Sea-island type composite superfine fibers have extremely fine diameters and small inter-fiber gaps, which can effectively prevent air convection and significantly improve thermal performance.

[0006] The "island" component in conventional sea-island type composite superfine fibers is polyester or polyamide, and polyester and polyamide themselves have certain thermal conductivity. In this case, the "island" component fiber material will limit the thermal effect of sea-island type composite superfine fibers, therefore, designing and optimizing the island component to reduce the thermal conductivity of the fiber can break through the bottleneck of thermal effect. SUMMARY

[0007] The application provides a sea-island type composite superfine fiber and a preparation method thereof, which can solve the problem of high thermal conductivity of sea-island type composite superfine fibers in the prior art.

[0008] The purpose of the application can be achieved by the following technical solutions:

[0009] A preparation method of a sea-island type composite superfine fiber, comprising the following steps:

[0010] Step one, stirring and mixing polyvinyl butyral, antioxidant, polyamide and modified nano titanium dioxide to obtain a mixed material, and melt blending to obtain an island phase master batch;

[0011] Step two, melt spinning of island phase master batch and sea phase master batch, and stretching treatment to obtain sea island type composite fiber;

[0012] Step three, sea island type composite fiber is added into sodium hydroxide solution, alkali reduction fibrillation, and then put into acetone, polyvinyl butyral is dissolved to remove and form pores, to obtain sea island type composite ultrafine fiber containing pore structure;

[0013] The sea phase master batch is alkali-soluble polyester.

[0014] Traditional sea island fiber is mostly composed of polyester or polyamide as island component and alkali-soluble material as sea component. After dissolving the sea component by alkali solution, the island component fiber left has low fineness and large specific surface area. However, the prepared ultrafine fiber is still a solid fiber composed of island component. Under the limitation of the lower limit of sea island ultrafine fiber fineness in the current technology, the thermal conductivity of the same material is difficult to further reduce. The lower the thermal conductivity, the better the warmth retention performance of the material, so there is a bottleneck in improving the warmth retention effect.

[0015] In the preparation of sea island fiber, polyvinyl butyral and modified nano titanium dioxide are added to the island component. After the island phase is formed into a fiber by melt spinning, the nano titanium dioxide exists in the fiber. After stretching, pores will be formed around the nano titanium dioxide due to the interfacial stress, and the fiber will have a porous structure, increasing the air ratio and reducing the thermal conductivity. In addition, polyvinyl butyral has excellent alkali resistance. In the process of removing the sea component by sodium hydroxide solution, the island fiber structure is maintained. Then, acetone treatment is performed. By utilizing the property of polyvinyl butyral to dissolve in acetone, the polyvinyl butyral inserted in the island fiber is removed, forming a porous structure on the fiber and further reducing the thermal conductivity.

[0016] Further, the average molecular weight of the polyvinyl butyral is 40000-70000 g / mol.

[0017] Further, the polyamide is at least one of PA6 and PA66.

[0018] Further, the antioxidant is at least one of antioxidant 168, antioxidant 1098 and antioxidant 1010. The thermal oxidation resistance of polyvinyl butyral is poor. In the melting process, it may be thermally oxidized and degraded due to the action of oxygen. At this time, the fiber has not been stretched. The early degradation of polyvinyl butyral will reduce the toughness of the fiber and prevent continuous stretching. The addition of antioxidant can inhibit the thermal oxidation degradation of polyvinyl butyral and ensure that the fiber does not break during stretching.

[0019] Further, the modified nano titanium dioxide is prepared as follows:

[0020] The nano-titanium dioxide is dispersed in water to form a dispersion liquid with a concentration of 20-50 g / L, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane and tetraethyl silicate are added, and stirring is continued for 6-10 h, and then the modified nano-titanium dioxide is obtained by ethanol washing, filtration and drying.

[0021] The N-(2-aminoethyl)-3-aminopropyl trimethoxysilane is hydrolyzed in water to generate silanol groups, which are dehydrated and condensed with the hydroxyl groups on the surface of the nano-titanium dioxide to form covalent bonds, and the silane is anchored on the surface of the nano-titanium dioxide, and the amino groups at the other end can form hydrogen bonds with the hydroxyl groups contained in the polyvinyl butyral and the amide groups in the polyamide, thereby promoting dispersion. The tetraethyl silicate is hydrolyzed to generate active monomer silicic acid, which is condensed with the silanol groups to form a close combination, thereby reducing the tendency of the nano-titanium dioxide to agglomerate.

[0022] Further, the particle size of the nano-titanium dioxide is 10-50 nm.

[0023] Further, the N-(2-aminoethyl)-3-aminopropyl trimethoxysilane is 3-4% of the mass of the nano-titanium dioxide.

[0024] The tetraethyl silicate is 12-16% of the mass of the nano-titanium dioxide.

[0025] Further, the mass fraction of the polyvinyl butyral in the mixture is 5-10%, the mass fraction of the modified nano-titanium dioxide is 2-8%, and the mass fraction of the antioxidant is 0.1-0.5%.

[0026] Further, the temperature of the melt blending is 230-265℃.

[0027] Further, the mass ratio of the island phase master batch to the sea phase master batch is (1:9)-(3:7).

[0028] Further, the stretching treatment is 2-3 times.

[0029] Further, the concentration of the sodium hydroxide solution is 1-2 wt%, and the temperature is 60-80℃.

[0030] The application also provides an island-sea type composite ultrafine fiber prepared by the preparation method, and the fineness of the island-sea type composite ultrafine fiber is 1-3 μm.

[0031] The application has the following beneficial effects:

[0032] (1) The polyvinyl butyral and modified nano titanium dioxide are added in the island component of the island-in-the-sea fiber, the long chain and amino group exist on the surface of the modified nano titanium dioxide, the hydrogen bond of the amino group and the hydroxyl group on the polyvinyl butyral is utilized to promote the dispersion of the modified nano titanium dioxide, in the stretching process, the interface difference of the dispersed modified nano titanium dioxide is utilized to create pores in the island fiber, the porosity of the ultra-fine fiber is improved, and the thermal conductivity is reduced.

[0033] (2) In the preparation process, a two-step dissolution method is adopted, first, the alkali solution is used to remove the sea component (alkali-soluble polyester), the island component left behind forms an ultra-fine fiber bundle, then the difference in solubility of polyamide and polyvinyl butyral in acetone is utilized to remove the polyvinyl butyral in the ultra-fine fiber, forming a porous structure, and preparing a fiber material with ultra-fine, high specific surface area, porous structure and excellent mechanical properties. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0035] Embodiment 1

[0036] Preparation of modified nano titanium dioxide:

[0037] The nano titanium dioxide with a particle size of 10-50 nm is dispersed in water to form a dispersion liquid with a concentration of 30 g / L, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane and tetraethyl silicate are added and continuously stirred for 8 h, then filtered after ethanol washing and dried to obtain the modified nano titanium dioxide. Among them, the mass fraction of N-(2-aminoethyl)-3-aminopropyl trimethoxysilane is 3.5% of the mass of nano titanium dioxide, and the mass fraction of tetraethyl silicate is 15% of the mass of nano titanium dioxide.

[0038] A preparation method of an island-in-the-sea type composite ultra-fine fiber, comprising the following steps:

[0039] Step one, polyvinyl butyral (average molecular weight 40000-70000 g / mol), antioxidant 1010, PA6 and modified nano titanium dioxide are stirred and mixed to obtain a mixture, wherein the mass fraction of polyvinyl butyral is 8%, the mass fraction of modified nano titanium dioxide is 5%, and the mass fraction of antioxidant 1010 is 0.3%, and island phase master batch is obtained by melt blending at 260℃.

[0040] Step two, melt spinning the island phase master batch and the alkali-soluble polyester master batch (sea phase master batch) according to a mass ratio of 2:8, setting the draw ratio to 2 times, and performing draw treatment to obtain the sea-island composite fiber.

[0041] Step three, adding the sea-island composite fiber into a 1wt% sodium hydroxide solution, performing alkali content opening treatment at a temperature of 65°C, and then putting it into acetone, dissolving and removing the polyvinyl butyral to form pores, to obtain the sea-island composite ultrafine fiber containing pore structures, with a fineness of 1-3μm.

[0042] Example 2

[0043] The difference from Example 1 is that the mass fraction of polyvinyl butyral in the mixture is 5%, and the mass fraction of antioxidant 1010 is 0.1%.

[0044] A preparation method of a sea-island composite ultrafine fiber, comprising the following steps:

[0045] Step one, stirring and mixing polyvinyl butyral (average molecular weight of 40000-70000g / mol), antioxidant 1010, PA6 and modified nano titanium dioxide (preparation method same as Example 1) to obtain a mixture, wherein the mass fraction of polyvinyl butyral is 5%, the mass fraction of modified nano titanium dioxide is 5%, and the mass fraction of antioxidant 1010 is 0.1%, and melt blending at 260°C to obtain an island phase master batch.

[0046] Step two, melt spinning the island phase master batch and the alkali-soluble polyester master batch (sea phase master batch) according to a mass ratio of 2:8, setting the draw ratio to 2 times, and performing draw treatment to obtain the sea-island composite fiber.

[0047] Step three, adding the sea-island composite fiber into a 1wt% sodium hydroxide solution, performing alkali content opening treatment at a temperature of 65°C, and then putting it into acetone, dissolving and removing the polyvinyl butyral to form pores, to obtain the sea-island composite ultrafine fiber containing pore structures, with a fineness of 1-3μm.

[0048] Example 3

[0049] The difference from Example 1 is that the mass fraction of polyvinyl butyral in the mixture is 10%, and the mass fraction of antioxidant 1010 is 0.5%.

[0050] A preparation method of a sea-island composite ultrafine fiber, comprising the following steps:

[0051] Step one, polyvinyl butyral (average molecular weight of 40000-70000 g / mol), antioxidant 1010, PA6 and modified nano titanium dioxide (preparation method same as example 1) are stirred and mixed to obtain a mixture, wherein the mass fraction of polyvinyl butyral is 10%, the mass fraction of modified nano titanium dioxide is 5%, and the mass fraction of antioxidant 1010 is 0.5%. Island phase master batch is obtained by melt blending at 260℃.

[0052] Step two, melt spinning island phase master batch and alkali soluble polyester master batch (sea phase master batch) according to the mass ratio of 2:8, set the draw ratio to 2 times, and stretch to obtain sea island composite fiber.

[0053] Step three, sea island composite fiber is added into 1wt% sodium hydroxide solution, the temperature is 65℃, alkali reduction fibrillation treatment, then put into acetone, polyvinyl butyral is dissolved and removed to form pores, and sea island composite ultrafine fiber containing pore structure is obtained, the fineness is 1-3μm.

[0054] Example 4

[0055] The difference from example 1 is only that the mass fraction of modified nano titanium dioxide in the mixture is 2%.

[0056] A method for preparing sea island composite ultrafine fiber, comprising the following steps:

[0057] Step one, polyvinyl butyral (average molecular weight of 40000-70000 g / mol), antioxidant 1010, PA6 and modified nano titanium dioxide (preparation method same as example 1) are stirred and mixed to obtain a mixture, wherein the mass fraction of polyvinyl butyral is 8%, the mass fraction of modified nano titanium dioxide is 2%, and the mass fraction of antioxidant 1010 is 0.3%. Island phase master batch is obtained by melt blending at 260℃.

[0058] Step two, melt spinning island phase master batch and alkali soluble polyester master batch (sea phase master batch) according to the mass ratio of 2:8, set the draw ratio to 2 times, and stretch to obtain sea island composite fiber.

[0059] Step three, sea island composite fiber is added into 1wt% sodium hydroxide solution, the temperature is 65℃, alkali reduction fibrillation treatment, then put into acetone, polyvinyl butyral is dissolved and removed to form pores, and sea island composite ultrafine fiber containing pore structure is obtained, the fineness is 1-3μm.

[0060] Example 5

[0061] The difference from example 1 is only that the mass fraction of modified nano titanium dioxide in the mixture is 8%.

[0062] A preparation method of sea-island type composite ultrafine fiber, comprising the following steps:

[0063] Step one, polyvinyl butyral (average molecular weight of 40000-70000 g / mol), antioxidant 1010, PA6 and modified nano titanium dioxide (preparation method same as example 1) are stirred and mixed to obtain a mixture, wherein the mass fraction of polyvinyl butyral is 8%, the mass fraction of modified nano titanium dioxide is 8%, and the mass fraction of antioxidant 1010 is 0.3%, and island phase master batch is obtained by melt blending at 260°C.

[0064] Step two, melt spinning the island phase master batch and alkali soluble polyester master batch (sea phase master batch) according to a mass ratio of 2:8, and setting the stretching multiple to 2 times to obtain sea-island type composite fiber by stretching treatment.

[0065] Step three, the sea-island type composite fiber is added into 1wt% sodium hydroxide solution at a temperature of 65°C for alkali reduction and fiber opening treatment, and then is put into acetone, polyvinyl butyral is dissolved and removed to form pores, and sea-island type composite ultrafine fiber containing pore structure is obtained, with a fineness of 1-3μm.

[0066] Comparative example 1

[0067] The difference from example 1 is that the island phase master batch of the present comparative example does not add modified titanium dioxide.

[0068] A preparation method of sea-island type composite ultrafine fiber, comprising the following steps:

[0069] Step one, polyvinyl butyral (average molecular weight of 40000-70000 g / mol), antioxidant 1010 and PA6 are stirred and mixed to obtain a mixture, wherein the mass fraction of polyvinyl butyral is 8%, and the mass fraction of antioxidant 1010 is 0.3%, and island phase master batch is obtained by melt blending at 260°C.

[0070] Step two, melt spinning the island phase master batch and alkali soluble polyester master batch (sea phase master batch) according to a mass ratio of 2:8, and setting the stretching multiple to 2 times to obtain sea-island type composite fiber by stretching treatment.

[0071] Step three, the sea-island type composite fiber is added into 1wt% sodium hydroxide solution at a temperature of 65°C for alkali reduction and fiber opening treatment, and then is put into acetone, polyvinyl butyral is dissolved and removed to form pores, and sea-island type composite ultrafine fiber containing pore structure is obtained, with a fineness of 1-3μm.

[0072] Comparative example 2

[0073] The difference from Example 1 is that the island phase master batch of the present comparative example is not added with polyvinyl acetal and antioxidant 1010.

[0074] Preparation of modified nano-titania:

[0075] Nano-titania with a particle size of 10-50 nm is dispersed in water to form a dispersion liquid with a concentration of 30 g / L, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane and tetraethyl silicate are added and stirred for 8 h, then filtered after ethanol washing and dried to obtain modified nano-titania. Among them, the mass fraction of N-(2-aminoethyl)-3-aminopropyl trimethoxysilane is 3.5% of the mass of nano-titania, and the mass fraction of tetraethyl silicate is 15% of the mass of nano-titania.

[0076] A preparation method of sea-island type composite ultrafine fiber, comprising the following steps:

[0077] Step one, PA6 and modified nano-titania are stirred and mixed to obtain a mixture, wherein the mass fraction of modified nano-titania is 5%, and island phase master batch is obtained by melt blending at 260°C.

[0078] Step two, the island phase master batch and the alkali-soluble polyester master batch (sea phase master batch) are melt spun according to a mass ratio of 2:8, the draw ratio is set to 2 times, and the sea-island type composite fiber is obtained after stretching treatment.

[0079] Step three, the sea-island type composite fiber is added into 1wt% sodium hydroxide solution, and alkali reduction and fiber opening treatment are carried out at a temperature of 65°C, and the sea-island type composite ultrafine fiber with internal pore structure is obtained after treatment, and the fineness is 1-3μm.

[0080] Comparative example 3

[0081] The difference from Example 1 is that the island phase master batch of the present comparative example is not added with modified titania, polyvinyl acetal and antioxidant 1010, and PA6 master batch is directly used as island phase master batch.

[0082] A preparation method of sea-island type composite ultrafine fiber, comprising the following steps:

[0083] Step one, PA6 master batch (island phase master batch) and alkali-soluble polyester master batch (sea phase master batch) are melt spun according to a mass ratio of 2:8, the draw ratio is set to 2 times, and the sea-island type composite fiber is obtained after stretching treatment.

[0084] Step two, the sea-island type composite fiber is added into 1wt% sodium hydroxide solution, and alkali reduction and fiber opening treatment are carried out at a temperature of 65°C, and the sea-island type composite ultrafine fiber is obtained after treatment, and the fineness is 1-3μm.

[0085] The sea-island composite ultrafine fibers prepared according to Example 1-Example 5 and Comparative Example 1-Comparative Example 3 were tested for performance at room temperature, and the results are shown in Table 1.

[0086] Table 1

[0087] Item Thermal conductivity W / (m K) Breaking strength cN / dtex Example 1 0.032 5.62 Example 2 0.035 5.67 Example 3 0.030 5.39 Example 4 0.036 5.54 Example 5 0.028 5.46 Comparative Example 1 0.047 5.50 Comparative Example 2 0.043 5.65 Comparative Example 3 0.055 5.60

[0088] As can be seen from Table 1, in Example 1-Example 5, as the polyvinyl butyral increases, the porosity of the fiber after treatment with acetone increases, and the thermal conductivity decreases, but the increase in the porosity of the fiber greatly destroys the continuous phase structure of the fiber, and the breaking strength decreases. The decrease in the modified nano-titanium dioxide in Example 4 and Example 5 weakens the pore-forming ability during stretching, and the thermal conductivity of the fiber increases, and the warmth-keeping effect of the fiber decreases. In Comparative Example 1 and Comparative Example 2, in the absence of one of the pore-forming components, the thermal conductivity of the fiber is higher, and the warmth-keeping effect decreases. The thermal conductivity of the fiber in Comparative Example 3 is significantly higher than that of the fiber in Example 1, and the warmth-keeping performance is poorer.

[0089] It should be noted that the relational terms herein such as first and second, and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprising", "including", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0090] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing sea-island type composite ultrafine fibers, characterized in that: The following steps are involved: Step 1: mixing polyvinyl butyral, antioxidant, polyamide and modified nano-titanium dioxide to obtain a mixture, and melt-blending at 230-265° C. to obtain an island phase masterbatch; Step 2: melt-spinning the island-phase masterbatch and the sea-phase masterbatch, and stretching them to obtain sea-island composite fibers; Step 3: adding the sea-island type composite fiber to a sodium hydroxide solution, alkali-reducing and fiber-opening, and then adding it to acetone to dissolve and remove the polyvinyl butyral to form pores, thereby obtaining a sea-island type composite ultrafine fiber with a porous structure; The sea phase masterbatch is alkali-soluble polyester.

2. The method for preparing a sea-island type composite ultrafine fiber according to claim 1, characterized in that: The average molecular weight of the polyvinyl butyral is 40000-70000 g / mol; The polyamide is at least one of PA6 and PA66.

3. The method for preparing a sea-island type composite ultrafine fiber according to claim 1, characterized in that: The antioxidant is at least one of antioxidant 168, antioxidant 1098 and antioxidant 1010.

4. The method for preparing a sea-island type composite ultrafine fiber according to claim 1, characterized in that: The preparation of the modified nano titanium dioxide is as follows: Nano-titanium dioxide with a particle size of 10-50 nm is dispersed in water to form a dispersion with a concentration of 20-50 g / L, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and tetraethyl silicate are added and stirred for 6-10 hours, washed with ethanol, filtered, and dried to obtain modified nano-titanium dioxide.

5. The method for preparing the island-in-sea composite ultrafine fiber according to claim 4, characterized in that: The N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is 3-4% of the mass of the nano-titanium dioxide; The tetraethyl silicate accounts for 12-16% of the mass of the nano titanium dioxide.

6. The method for preparing the island-in-sea composite ultrafine fiber according to claim 1, wherein: The mass fraction of polyvinyl butyral in the mixture is 5-10%, the mass fraction of modified nano titanium dioxide is 2-8%, and the mass fraction of antioxidant is 0.1-0.5%.

7. The method for preparing a sea-island type composite ultrafine fiber according to claim 1, characterized in that: The mass ratio of the island phase masterbatch to the sea phase masterbatch is (1:9)-(3:7).

8. The method for preparing the island-in-sea composite ultrafine fiber according to claim 1, wherein: The stretching treatment is performed at a multiple of 2-3 times.

9. The method for preparing the island-in-sea composite ultrafine fiber according to claim 1, wherein: The concentration of the sodium hydroxide solution is 1-2 wt %, and the temperature is 60-80° C.

10. A sea-island type composite microfiber, characterized in that: The island-in-sea composite ultrafine fiber is prepared by the method for preparing the island-in-sea composite ultrafine fiber according to any one of claims 1 to 9; The fineness of the island-in-sea composite ultrafine fiber is 1-3 μm.