Briefly understand the main types of composite fibers
1. Side-by-side laminating fiber
Side-by-side type The spinning of conformal fibers is more difficult than the spinning of sheath-core fibers and therefore requires higher polymer requirements.
(1) The two polymer materials used to spin side-by-side laminated fibers should have better compatibility, otherwise peeling will easily occur during the spinning process, making the spinning process difficult.
(2) The two polymer materials used should have similar properties under the corresponding spinning process conditions. The melt viscosity can be adjusted to avoid the “elbow” phenomenon that occurs when the melt is ejected from the spinneret during the spinning process, which affects the normal progress of the spinning process.
The main factors affecting the melt viscosity of the two polymer materials under spinning process conditions include:
(1) The relative molecular masses of the two polymer materials.
(2) Melt temperature control of the two polymers in their respective screw extruders and elbows And the temperature control of the final spinning box.
(3) Dependence of melt viscosity of two polymers on shear rate, including two polymerizations The respective pump supply volume of the material melt, the aperture of the spinneret hole, the aspect ratio, etc.
Therefore, before the spinning of side-by-side laminated fibers is carried out, various necessary preparations must be made. , corresponding planning work. Doing so will also help analyze problems that may occur.
2. Multi-layer parallel laminated fiber
Multi-layer side-by-side laminated fiber is the result of side-by-side fiber lamination and then lamination. It is composed of two polymer materials with certain compatibility alternating with each other. Arranged into a multi-layer structure and laminated along the fiber axis. The selection principle of the two polymer materials should be to ensure that peeling is not easy to occur during the spinning process and to take into account the final peelability of the fiber produced.
Multi-layer side-by-side laminated fibers can use chemical or physical methods during the fabric finishing process After peeling off, the peeled microfiber takes on a rectangular shape with four corners, which is very suitable for use as a wiping cloth material. Fibers with a rectangular cross-section have different sizes in the length and width directions, and the ease of bending and deformation of the fiber is related to the aspect ratio of the fiber cross-section. Therefore, fabrics made from fibers with different aspect ratios will produce different styles. If the width of the rectangle is small enough, colors similar to butterfly wings will appear due to the complete reflection effect.
3. Orange valve type laminated fiber
Orange petal type laminated fiber is a split-type laminated fiber composed of two polymers with different chemical structures and/or properties. Its cross-section is made up of something similar to “orange petal” It is composed of lobes in the shape of “petals”. For example, the polymer raw materials used can be PET and PA6. There is a certain compatibility between the two to ensure the normal progress of spinning and finishing processes, but they are different in certain properties, which can be used in the fabric processing process. to achieve the peeling effect.
Using this form of fiber cross-section, a “wedge” type of ultrafine fiber can be obtained after peeling off. A single fiber has three sharp corners, which is particularly useful as a wiping cloth. This kind of orange-petal type laminating fiber can be divided into 6+6 or 8+8 types, that is, it consists of 6 petals (or 8 petals) PET and 6 petals (or 8 petals) PA6 spaced apart from each other to form an orange petal type. Usually the proportion of PET is increased. If the two components are not properly peeled off, it will easily cause poor coloring of the microfiber fabric. In order to solve this problem, EHDPET/PA6 (20/80) orange-petal type laminated fibers can also be made, and then the laminated fiber fabric is hydrolyzed to dissolve the EHDPET to obtain single-component ultrafine fibers of PA6. Using the orange-petal type bonded fiber spinning method, ultrafine fibers with a linear density of about 0.15 dtex can finally be obtained.
4. Hollow orange-petal type and rice-shaped laminating fibers
The hollow orange-flap type laminating fiber is an improvement on the above-mentioned orange-flap type laminating fiber, with the purpose of improving the peeling effect. Since the flaps of the orange-flap type bonding fiber are connected to each other, peeling may not be done well. If the middle part of the fiber is made hollow, the contact area between the orange petals can be reduced, which is beneficial to peeling off.
The rice-shaped laminated fiber is composed of two polymers with different chemical structures and/or properties. A split-type laminated fiber whose cross-section is composed of a “rice”-shaped skeleton and a fan shape between the “meter-shaped” skeletons. One of the polymers (such as PA6 or PET) is made into a “rice”-shaped skeleton, and the other polymer (such as PET or PA6) is made into a fan shape between the “rice”-shaped skeletons. PA6 is usually used as the “meter” shaped skeleton. As the proportion of the “米”-shaped skeleton increases, the “米”-shaped skeleton gradually becomes thicker. If the proportion of “rice”-shaped skeleton is less than 15%, the skeleton will be too thin and uneven, which will increase the difficulty of peeling and affect the effect of peeling. The proportions of the “meter”-shaped skeleton are tooWhen it is high (such as reaching 50%), the skeleton becomes very thick, and a thicker fiber will be formed after peeling off, which affects the softness of the microfiber fabric and also increases the production cost. Therefore, it is more appropriate to choose 20% as the proportion of the “meter”-shaped skeleton. The characteristics of the fabric made of this rice-shaped laminated fiber are that it has the softness of fan-shaped microfibers and the rigidity and stiffness of the “rice”-shaped skeleton material.
There is also EHDPET used as the laminated fiber of the “meter”-shaped skeleton material, and the fiber is woven into fabrics Finally, the EHDPET is hydrolyzed and dissolved with a dilute alkali solution, and finally a fan-shaped ultrafine fiber fabric is obtained. The rice-shaped laminating fiber is often commonly known as the “8+1” type, which is composed of 8 sectors plus 1 rice-shaped fiber. In order to make the single fiber linear density thinner, it can also be made into “16+1” and other varieties. In order to ensure a balance between good spinnability during spinning and easy peelability of single fibers during finishing, the two selected polymer components should have appropriate compatibility.
5. Gear-type laminating fiber
Gear-type laminating fiber is actually a variant of rice-shaped laminating fiber. It is also composed of two polymers with different chemical structures and/or properties, and its cross-section is gear-shaped: one of the polymers constitutes the main body of the gear, and the other constitutes the gap material between the teeth.
After the gear-type laminated fiber is peeled off, the material in the gap between the teeth forms ultra-fine fibers , provides the fabric with a soft style, while the material that makes up the gear-shaped body provides the fabric with rigidity and stiffness. In fact, the gear-shaped bonding fiber can be considered as an improvement on the rice-shaped bonding fiber. Similar to the selection principle of the two polymer components of the rice-shaped laminated fiber, the two polymer components of the gear-shaped laminated fiber should also have appropriate compatibility.
6. Sheath-core laminated fiber
Sheath-core fiber is composed of two components that are coated with each other in layers and laminated along the axial direction of the fiber. Usually refers to the concentric type, in addition to the eccentric type, special-shaped skin-core type and multi-layer skin-core type. Sheath-core fibers are mostly used for self-adhesive fibers. For example, the ES fiber developed by Nippon Suso Co., Ltd. uses PE (tm = 107°C) with a lower melting point as the skin layer and PP (tm = 167°C) with a higher melting point as the skin layer. Sheath-core fiber in the core layer. The fiber and other fibers are uniformly blended to make a non-woven fabric, and then hot air or hot roller pressing is performed at a temperature between the melting points of PE and PP to melt the skin components, between ES fibers or between ES fibers. Hot melt bonding occurs with other fibers. Because the fiber cortex is very thin, the bonding between fibers is fine, the product feels soft, and the strength of the nonwoven fabric is improved. Such products are mostly used in children’s and women’s hygiene products. Chen Guokang et al. reported a manufacturing method of laminated fibers using PE or its copolymer as the skin layer and PP as the core layer, saying that it can improve the softness of the fiber.
There are also reports on the manufacture of core-skin fiber with PA6 as the skin layer and PET as the core layer. When this fiber is used to make tire cords, it can make full use of the excellent adhesion between PA6 and rubber, and can also take advantage of the rigidity and high modulus of PET to improve the “flat spot effect” of the tire. In addition, there are sheath-core fibers with PA6 as the sheath and PET as the core. When manufacturing this fiber, appropriately increasing the proportion of PET can reduce production costs and at the same time increase the modulus of the laminated fiber; PA6 as the skin layer can also improve the coloring, wear resistance and moisture absorption properties of the fiber. In recent years, some manufacturers have adopted recycled PET as the core layer to produce core-sheath fibers, which not only further reduces product costs, but also has positive significance for the recycling and utilization of waste materials and environmental protection.
If the core layer adopts a polymer material with better hygroscopicity or a material with conductive properties, it can Improve the hygroscopic properties or conductive properties of fibers. The author has used PET, PA6 or PP as the skin layer and self-made copolyetherester as the core layer to prepare a skin-core fiber with excellent antistatic properties. The specific resistance value of the obtained fiber after removing the oil agent is 1×10 7 times Square Ω?cm. There are also reports of using polymers containing conductive components as the core layer to produce conductive sheath-core laminated fibers.
When spinning sheath-core bonded fibers, although the requirements for spinnability are higher than those of side-by-side bonded fibers. Synthetic fiber is slightly lower, but the melting points of the two polymer components should not be too different, and the melt viscosity of the two components under the spinning process conditions should be completely similar and have good compatibility. The fibers are well bonded together and there is no obvious boundary between the skin layer and the core layer. When spinning eccentric laminated fibers, the requirements for spinnability are slightly higher. The main requirement is that the melt viscosity of the two components under spinning conditions is similar to avoid “bending” when the melt is extruded from the spinneret. head” phenomenon. If the fiber is designed to be eccentrically adhered to the fiber composed of two polymers with different chemical structures and/or properties (Figure 3-12), the fiber can also be given the property of permanent helical curling of the three-dimensional stationary body at the same time.
7. Sea-island type layer��Fiber
Sea-island type laminating fiber is actually a multi-core type sheath-core laminating fiber Fiber, a core component composed of one polymer material (also known as the “island” phase or dispersed phase) is dispersed in a longitudinally continuous form in a sea component composed of another polymer material (also known as the “sea” phase or Continuous phase), some people call it polymer alignment fiber, and some people vividly call it sea-island type composite fiber. Typically, the two polymers used to make sea-island-type bonded fibers must have selective dissolving properties for a certain solvent.
For example, when the material of the island component is PET, PA6 or PA66, PS or PE can be used As the sea component, after spinning into a sea-island type laminated fiber, the PS or PE in it can be dissolved with toluene or xylene to obtain PET, PA6 or PA66 ultrafine fibers. If the sea component is replaced with easily hydrolyzable polyester EHDPET, the sea component can be removed with dilute alkali solution and ultrafine fibers can also be obtained. Sea-island type laminated fiber can not only be used to prepare ultrafine fibers, but also porous hollow fibers: swap the positions of the above-mentioned sea and island components, such as using PET, PA6 or PA66 as the sea component, and Using EHDPET as the island component, the sea-island type composite fiber produced is porous hollow fiber after alkali hydrolysis.
Superfine fiber filaments can be used as raw materials for peach skin brushing or suede, and Microshort fibers can be used to make artificial suede. Porous hollow fiber is usually used to make artificial leather. It is soft, warm and elastic. It is a good material for organizing various shoes and trolley bags.
The above uses PS or PE as the sea component, using sea-island type lamination spinning and melting and peeling The technology of manufacturing microfibers by law is now on the verge of becoming obsolete due to the need to use organic solvents in the stripping process. Instead, the sea-island type composite spinning-hydrolysis stripping method technology is used, which uses PET, PA6 or PA66 as the island phase component and the easily hydrolyzable polyester EHDPET as the marine phase component. One island type laminated fiber technology. In fact, the key to this technology is the design and manufacturing of sea-island type composite spinning components, as well as the synthesis and performance control of easily hydrolyzable polyester EHDPET.
8. Other types of laminated fibers
In addition to the laminated fibers mentioned above, there are also many laminated fibers with various shapes and properties. For example, small triangles that are easily hydrolyzed are inlaid at the three sharp corners of a triangular fiber. After hydrolysis, small grooves will be formed at the three sharp corners, causing the fiber to produce a “silky” effect.
In the middle of the circular cross-section PA6 fiber, a polygonal polymer with high TiO2 content is embedded. The material serves as the core layer, and each sharp corner of the polygon is connected to the outer edge of the fiber, resulting in a skin-core laminated fiber with extraordinary core shape and performance. No matter whether the completed line hits the fiber from any angle, it can only be reflected and will not penetrate the fiber. Swimwear made of knitted fabrics made of this fiber is very popular because it is white and not see-through. If you use it to make summer work clothes, it will be drapey, elegant, free and easy, showing an elegant style, and is very suitable for women’s clothing.
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