1. Side-by-side composite fiber
Side-by-side composite fiber The spinning of 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 composite 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 parallel composite fibers is carried out, various necessary and Prepare accordingly. Doing so will also help analyze possible problems.
2. Multi-layer parallel composite fiber
Multi-layer parallel composite fiber is the result of parallel fiber composite and re-composite. It is composed of two polymer materials with certain compatibility arranged alternately into multiple layers. structure, and compounded 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 composite fiber can be peeled off chemically or physically during fabric post-processing. The microfiber has a rectangular shape with 4 corners and is very suitable for use as a wiping cloth material. Fibers with rectangular cross-sections 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 effect of light reflection.
3. Orange petal type composite fiber
Orange-petal composite fiber is a split-type composite fiber composed of two polymers with different chemical structures and/or properties. Its cross-section is shaped like an “orange petal” composed of lobes. 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 post-processing, 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, “wedge” type ultrafine fibers can be obtained after stripping. A single fiber has three sharp corners, which is very useful as a wiping cloth. This kind of orange-petal composite 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 is easy to cause poor dyeing of the microfiber fabric. In order to solve this problem, EHDPET/PA6 (20/80) orange-petal composite fibers can also be made, and then the composite fiber fabric is hydrolyzed to dissolve the EHDPET to obtain single-component ultrafine fibers of PA6. Using the orange-petal composite 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 composite fibers
The hollow orange-flap type composite fiber is an improvement on the above-mentioned orange-flap type composite fiber, with the purpose of improving the peeling effect. Since the petals of the orange-petal type composite fiber are interconnected, peeling may not be good in some cases. 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.
Mi-shaped composite fiber is a split-type composite fiber composed of two polymers with different chemical structures and/or properties. Its cross-section consists of a “m”-shaped skeleton and a fan-shaped segment between the “m”-shaped skeleton. Composition. One of the polymers (such as PA6 or PET) is made of ” “rice”-shaped skeleton, and another polymer (such as PET or PA6) is a fan shape between the “meter”-shaped skeleton. PA6 is usually used as the “meter”-shaped skeleton. As the proportion of the “meter”-shaped skeleton increases, The skeleton of the “meter” character gradually becomes thicker. If the proportion of the skeleton of the “meter” character is lower than 15%, the skeleton is too thin and uneven, which will increase the difficulty of peeling and affect the effect of peeling. When the proportion of “rice”-shaped skeleton is too high (such as reaching 50%), the skeleton will become very thick, and a layer will be formed after peeling. Thick fibers affect the softness of microfiber fabrics and also increase the production cost. Therefore, it is more appropriate to choose 20% of the “meter”-shaped skeleton. The characteristics of the fabric made of this rice-shaped composite fiber are that it has the softness of the fan-shaped microfiber and the “meter”-shaped skeleton. Rigidity and stiffness of materials
There is also a composite fiber that uses EHDPET as the “rice”-shaped skeleton material. After weaving the fiber into a fabric, the EHDPET is hydrolyzed and dissolved with a dilute alkali solution, and finally a fan-shaped ultrafine fiber fabric is obtained. The rice-shaped composite fiber Fiber is often commonly known as the “8+1” type, which consists of 8 sectors plus 1 rice. In order to make the single fiber linear density thinner, it can also be made into “16+1” and other varieties to ensure good spinnability during the spinning process and easy peelability of the single fiber during the post-processing process. Balance, the two selected polymer components should have appropriate compatibility.
5. Gear-type composite fiber
Actual gear-type composite fiber The above is a variant of the rice-shaped composite 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-shaped composite fiber is peeled off, the material in the gap between the teeth forms ultra-fine fibers, which provides the fabric with a soft style, while the material constituting the gear-shaped main body provides the fabric with rigidity and crispness. In fact, the gear-shaped composite fiber can be considered as an improvement of the M-shaped composite fiber. The two polymer components of the gear-shaped composite fiber have the same selection principles. Should have appropriate compatibility.
6. Sheath-core composite fiber
Sheath-core fiber is composed of two components that are coated with each other layer by layer and compounded along the fiber axis. 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 is uniformly blended with other fibers 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 composite fiber manufacturing method 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 also 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 composite fiber; PA6 as the skin layer can also improve the dyeability, wear resistance and moisture absorption properties of the fiber. In recent years, some manufacturers have used 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 is made of polymer materials with better hygroscopic properties or materials 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 composite fibers.
When spinning sheath-core composite fiber, although it canThe spinning performance requirements are slightly lower than those of side-by-side composite fibers, but the melting points of the two polymer components should not be too different, and the melt viscosity of the two components under spinning process conditions should be as similar as possible, and have good The compatibility is good, that is, they can be well bonded together after fiber formation, and there will be no obvious boundary between the skin layer and the core layer. When spinning eccentric composite 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 “elbows” when the melt is extruded from the spinneret. “Phenomenon. If designed as a biased composite fiber composed of two polymers with different chemical structures and/or properties (Figure 3-12), the fiber can also be given the property of three-dimensional helical permanent curling at the same time.
Seven. Sea-island type composite fiber
Sea-island composite fiber is actually a multi-core sheath-core composite fiber. The core component (also known as the “island” phase or dispersed phase) composed of a polymer material is in a longitudinally continuous form. Dispersed in the sea component (also called “sea” phase or continuous phase) composed of another polymer material, some people call it polymer alignment fiber, while others vividly call it a sea-island composite fiber. Generally, the two polymers used to make sea-island composite fibers must have selective solubility properties in 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 composite fiber, toluene or xylene can be used to dissolve the PS or PE in it 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 composite 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 PET, PA6 or PA66 as the sea component, and use EHDPET is used as the island component. After alkaline hydrolysis of the sea-island type composite fiber produced, porous hollow fibers are obtained.
Superfine fiber filaments can be used as raw materials for peach skin or suede, and superfine Short 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 processing various shoes and bags.
The above-mentioned technology of using PS or PE as the sea component and using the sea-island composite spinning-dissolution peeling method to produce ultra-fine fibers requires the use of Organic solvents are now on the verge of elimination. Instead, the sea-island 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 to spin the sea-island composite spinning. Island type composite 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 composite fibers
In addition to the composite fibers mentioned above, there are many composite fibers with special shapes and special properties. For example, small triangles that are easily hydrolyzable 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 optical 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 composite fiber with special core shape and performance. No matter whether the light hits the fiber from any angle, it can only be reflected without passing through the fiber. Swimwear made of knitted fabrics made of this fiber is very popular because it is white and not see-through. If it is used to make summer clothing, it will be drapey, elegant, free and easy, showing an elegant style, and is very suitable for women’s clothing.
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