Preparation method of extra-black low-shrinkage polyester staple fiber and extra-black low-shrinkage polyester staple fiber

Abstract

The invention discloses a preparation method of extra-black low-shrinkage polyester staple fibers and the extra-black low-shrinkage polyester staple fibers, and the preparation method comprises the following steps: extruding a black polyester melt, coating a pre-spinning oil agent to form tows, dipping the tows into a first low-refractive-index resin water-based emulsion containing a first low-refractive-index resin, and then drafting twice to obtain the extra-black low-shrinkage polyester staple fibers, wherein hot air is used as a drafting medium in the second drafting process, tension heat setting is carried out, second low-refractive-index resin water-based emulsion containing second low-refractive-index resin is sprayed, heating, baking and setting are carried out, relaxation heat setting is carried out after a post-spinning oil coating process and a curling process are carried out, and finally a finished product is obtained through a cutting process and a packaging process. The refractive indexes of the first low-refractive-index resin and the second low-refractive-index resin are different and are not higher than 1.5. The extra-black low-shrinkage polyester staple fiber has the performance characteristics of high blackness and low dry heat shrinkage rate, and is particularly suitable for being processed into extra-black sewing threads with high dimensional stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthetic fiber production. Specifically, it relates to a preparation method of super black and low shrinkage polyester staple fiber and the super black and low shrinkage polyester staple fiber. Background Art

[0002] The fiber with stock solution coloring can be processed into textiles without the need for a dyeing process, which has a prominent effect of reducing emissions and carbon. It is estimated that, compared with traditional post-spinning dyed polyester fiber, for each ton of fiber with stock solution coloring processed into textiles, 32 tons of wastewater and 1.2 tons of carbon dioxide can be reduced. Benefiting from industrial upgrading and the drive of energy conservation and emission reduction policies, the output of fiber with stock solution coloring has increased rapidly in recent years and has become a major variety of differential polyester fiber, among which black fiber accounts for more than 80%. The main colorant for fiber with stock solution coloring black polyester fiber is carbon black pigment. Compared with organic colorants, the coloring ability of carbon black pigment is relatively weak, resulting in the color of fiber with stock solution coloring black polyester fiber being lighter than that of traditional post-spinning dyed polyester fiber.

[0003] Finishing with low refractive index resin is one of the methods to improve the color depth of textile fabrics. By finishing with low refractive index resin, the reflection of light on the surface of the textile fabric can be reduced, so that more incident light enters the interior of the textile and is absorbed by the colorant in the synthetic fiber, thereby achieving the effect of deepening the color.

[0004] However, most of the existing resin finishing processes are complex, the conditions are harsh, and they are basically directly applied to textile fabrics and are difficult to be applied to polyester fibers that have not been woven into fabrics. In addition to being used for weaving into textiles, polyester fibers can also be used in the production of other products, such as sewing threads, etc. The above-mentioned resin finishing cannot achieve the effect of deepening the color of the sewing thread. In addition, the polyester fibers prepared by the existing polyester production process have the problem of high dry heat shrinkage rate. Even if the low refractive index resin can be finished on the surface of the polyester fiber, the adhesion firmness of the resin may be affected due to the heat shrinkage of the polyester fiber.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a preparation method of super black and low shrinkage polyester staple fiber and the super black and low shrinkage polyester staple fiber, and the super black and low shrinkage polyester staple fiber has the performance characteristics of high blackness and low dry heat shrinkage rate.

[0007] To solve the above technical problem, the basic concept of the technical solution adopted by the present invention is:

[0008] The first object of the present invention is to provide a preparation method of super black and low shrinkage polyester staple fiber, including the following steps:

[0009] (1) The black polyester melt is extruded from the spinneret holes and coated with the pre-spinning oil agent to obtain black undrawn polyester filaments;

[0010] (2) The black undrawn polyester filaments are impregnated with the first low refractive index resin aqueous emulsion, then subjected to the first drawing, and then the second drawing is carried out with hot air as the drawing medium to obtain black drawn polyester filaments coated with the low refractive index resin;

[0011] (3) The black drawn polyester filaments coated with the low refractive index resin are subjected to tension heat setting to obtain black drawn polyester filaments coated with the low refractive index resin after tension heat setting;

[0012] (4) The black drawn polyester filaments coated with the low refractive index resin after tension heat setting are sprayed with the second low refractive index resin aqueous emulsion, then heated for baking and setting, and then after the post-spinning oil agent coating process and the crimping process, relaxation heat setting is carried out to obtain black drawn polyester filaments coated with the low refractive index resin twice after relaxation heat setting;

[0013] (5) The black drawn polyester filaments coated with the low refractive index resin twice after relaxation heat setting are subjected to the cutting process and the packing process to obtain the finished product of super black low-shrinkage polyester staple fibers;

[0014] Among them, the first low refractive index resin aqueous emulsion contains the first low refractive index resin, and the second low refractive index resin aqueous emulsion contains the second low refractive index resin; the refractive indices of the first low refractive index resin and the second low refractive index resin are different and both are not higher than 1.5.

[0015] In the present invention, before the two drawing processes of the spinning process and after the tension heat setting process, two low refractive index resin aqueous emulsions are respectively coated on the black polyester fibers, and the refractive indices of the two low refractive index resins contained therein are both not higher than 1.5 and are different. Combined with the high-temperature heating of the black polyester fibers in the two drawing processes, the tension heat setting process, the baking and setting process, and the relaxation heat setting process of the spinning process, the coated low refractive index resin aqueous emulsion forms a resin film, which can reduce the reflection of light on the fiber surface and enable more incident light to enter the fiber interior and be absorbed by the carbon black pigment, thereby achieving the effect of deepening. Since the refractive indices of the two low refractive index resins are different, two low refractive index resin films with different refractive indices can be formed on the surface of the black polyester fibers, thereby further strengthening the deepening effect.

[0016] In addition, through a total of three high-temperature setting processes including the tension heat setting process, the baking and setting process, and the relaxation heat setting process, the short fibers prepared by post-processing of the black undrawn polyester filaments have a perfect supramolecular structure and the internal stress is fully relaxed, so they have good dimensional stability and can achieve a dry heat shrinkage rate of not higher than 4.2% at 180 °C. At the same time, the better dimensional stability of the short fibers also avoids the problem that the shrinkage amplitude is too large and affects the adhesion firmness of the low refractive index resin film on its surface.

[0017] Further, in step (2), the mass content of the first low refractive index resin in the first low refractive index resin aqueous emulsion is 2% to 6%.

[0018] In a further embodiment, the first low refractive index resin aqueous emulsion is formed by dispersing the first low refractive index resin in demineralized water at a mass content of 2% to 6%.

[0019] In the above embodiment, the first low refractive index resin has a refractive index less than 1.5, and a resin film with a refractive index not higher than 1.5 can be formed on the surface of the black polyester fiber. Compared with the general refractive index of polyester fiber of 1.73, the refractive index on the surface of the short fiber can be reduced by more than 0.23, so as to reduce the reflection of light on the surface of the black polyester fiber, enable more incident light to enter the fiber interior and be absorbed by the carbon black pigment, and thus achieve the effect of deepening the color.

[0020] As a specific embodiment, the first low refractive index resin aqueous emulsion is placed in an impregnation tank. After the black polyester undrawn filaments are bundled by a godet frame, they are drawn into the impregnation tank by a godet machine and fully impregnated with the first low refractive index resin aqueous emulsion. Controlling the mass content of the first low refractive index resin in the first low refractive index resin aqueous emulsion within the range of 2% to 6% can enable the first low refractive index resin aqueous emulsion to have good surface coating performance on the black polyester undrawn filaments, so that the black polyester undrawn filaments can be fully wrapped during the impregnation process and adhere to the surface of the filament bundle.

[0021] In addition, by using the method of drawing the filament bundle through the impregnation tank to coat the first low refractive index resin aqueous emulsion, the spinning oil agent on the fiber surface can also be washed off in the first low refractive index resin aqueous emulsion. The water washing process of the fiber passing through the water bath tank in the conventional spinning process can be directly replaced by the process of impregnating the first low refractive index resin aqueous emulsion without increasing the process steps.

[0022] Further, in step (2), the drawing medium for the first drawing is room temperature air, and the drawing ratio is 2.18 to 2.80; when performing the second drawing, the temperature of the hot air is 140 to 160 °C, and the drawing ratio is 1.18 to 1.33.

[0023] In the present invention, after the black polyester undrawn filaments are impregnated with the first low refractive index resin aqueous emulsion, the first drawing is performed in room temperature air. Under the action of the drawing tension, the excess first low refractive index resin aqueous emulsion can be extruded from the filament bundle, and then through the subsequent heating process, a resin film with a suitable thickness and uniform thickness can be formed on the fiber surface.

[0024] The second drawing uses hot air as the drawing medium. The high-temperature hot air is sprayed on the surface of the tow, which can quickly dry it and promote the transformation of the first low refractive index resin aqueous emulsion coated on the fiber surface into a film and fixation. Compared with the traditional process using steam as the drawing medium, using hot air as the drawing medium in the second drawing can, on the one hand, improve the heating efficiency of the first low refractive index resin aqueous emulsion coated on the fiber surface, and on the other hand, avoid the flushing of the first low refractive index resin aqueous emulsion coated on the fiber surface by steam.

[0025] In addition, by controlling the draw ratio of the first drawing within the range of 2.18 to 2.80 and the draw ratio of the second drawing within the range of 1.18 to 1.33, the macromolecular chains, crystal grains, etc. of the black polyester fiber can be highly oriented along the fiber axis, enabling its preliminary shaping.

[0026] As a specific implementation, the second drawing is carried out in a hot air heating box, and hot air is sprayed onto the surface of the tow as the drawing medium for the second drawing.

[0027] In a further solution, hot air at a temperature of 140 to 160 °C in the hot air heating box is directly sprayed onto the surface of the tow through flow control, quickly drying the first low refractive index resin aqueous emulsion and transforming it into a film and fixation. Among them, the spraying flow rate of the hot air is controlled according to the production output of the fiber production line.

[0028] In a more specific solution, the tow impregnated with the first low refractive index resin aqueous emulsion passes through the first drawing machine and the second drawing machine in sequence, and the first drawing is carried out between the first drawing machine and the second drawing machine. After the tow passes through the second drawing machine, it enters the hot air heating box, and a tension heat setting machine is arranged after the hot air heating box, so that the tow is drawn in the second drawing between the second drawing machine and the tension heat setting machine with hot air as the drawing medium to obtain a low refractive index resin-coated black polyester drawn yarn.

[0029] Further, in step (3), the heating temperature for tension heat setting is 180 to 210 °C, and the residence time of the tow is 12 to 20 s.

[0030] As a specific implementation, the low refractive index resin-coated black polyester drawn yarn is subjected to tension heat setting by a tension heat setting machine, and the temperature of the hot roll in the tension heat setting machine is controlled within the range of 180 to 210 °C, and the residence time of the tow is controlled within the range of 12 to 20 s.

[0031] In the above solution, by controlling the heating temperature and the residence time of the tow in the tension heat setting process, on the one hand, the fixation fastness of the first low refractive index resin on the surface of the black polyester fiber can be further improved, and on the other hand, the perfection degree of the supramolecular structure inside the fiber can be further improved, releasing the internal stress of the fiber and improving the dimensional stability performance of the fiber.

[0032] Further, in step (4), the mass content of the second lowest refractive index resin in the second lowest refractive index resin aqueous emulsion is 1% - 4%.

[0033] In a further embodiment, the second lowest refractive index resin aqueous emulsion is formed by dispersing the second lowest refractive index resin in deionized water at a mass content of 1% - 4%.

[0034] In the present invention, the low refractive index resin-coated black polyester heat-set filament obtained through the heat-setting process has a relatively high temperature. Spraying the second lowest refractive index resin aqueous emulsion thereon can not only achieve the second coating of the low refractive index resin aqueous emulsion with different refractive indices on the black polyester fiber, but also quickly cool the filament bundle and fix the supramolecular structure of the black polyester fiber.

[0035] Controlling the mass content of the second lowest refractive index resin in the second lowest refractive index resin aqueous emulsion within the range of 1% - 4% can enable the second lowest refractive index resin aqueous emulsion to have good surface coating performance on the black polyester fiber when using the spray coating method, so as to uniformly wrap the fiber surface.

[0036] Further, in step (4), the heating temperature for baking and setting is 110 - 140°C, and the residence time of the filament bundle is 4 - 6 s;

[0037] Preferably, the filament bundle is baked and set by a hot roll traction machine, and the temperature of the heating roll of the hot roll traction machine is controlled at 110 - 140°C.

[0038] In the above embodiment, after the filament bundle is sprayed with the second lowest refractive index resin aqueous emulsion, it is first heated for baking and setting, and then the post-spinning oil agent coating process is carried out. On the one hand, it promotes the transformation of the sprayed second lowest refractive index resin aqueous emulsion into a film and fixes it on the fiber surface, avoiding being washed away by the coated post-spinning oil agent in the post-spinning oil agent coating process. When the temperature of the heating roll of the hot roll traction machine is controlled at 110 - 140°C and the residence time of the filament bundle is controlled at 4 - 6 s, the effect of promoting the curing of the resin into a film is the best. On the other hand, the baking and setting process can cooperate with the front and back heat-setting processes and relaxation heat-setting processes, and the dimensional stability of the obtained staple fiber can be improved through a total of three high-temperature setting processes.

[0039] Further, in step (4), the heating temperature for relaxation heat-setting is 100 - 130°C, and the residence time of the filament bundle is 6 - 10 min;

[0040] Preferably, the heating temperature for relaxation heat-setting is 120 - 130°C.

[0041] As a specific embodiment, after the tow passes through the post-spinning oil agent coating process and the crimping process, it enters a relaxation heat setting machine and undergoes relaxation heat setting under heating conditions.

[0042] The heating temperature for relaxation heat setting is controlled within the range of 100 - 130 °C, and the residence time of the tow is controlled within 6 - 10 min. On the one hand, it can further improve the fixing fastness of the second low refractive index resin on the fiber surface, and at the same time, it also improves the fixing fastness of the post-spinning oil agent. Moreover, since the post-spinning oil agent covers the outside of the resin film formed by the second low refractive index resin, it can also prevent the resin film from falling off. On the other hand, the above temperature range and tow residence time can fully release the internal stress of the black polyester fiber during the relaxation heat setting process, further improving the dimensional stability of the obtained staple fiber.

[0043] Furthermore, both the first low refractive index resin and the second low refractive index resin are selected from one or a combination of cationic acrylic resins, polyether-modified silicone resins, quaternized silicone resins, quaternized organofluorosilicone resins, amino-modified silicone resins, and amino-modified organofluorosilicone resins, and the compositions of the first low refractive index resin and the second low refractive index resin are different;

[0044] Preferably, the first low refractive index resin is selected from at least one of cationic acrylic resins, polyether-modified silicone resins, quaternized silicone resins, quaternized organofluorosilicone resins, amino-modified silicone resins, and amino-modified organofluorosilicone resins;

[0045] The second low refractive index resin is selected from at least one of polyether-modified silicone resins, quaternized silicone resins, quaternized organofluorosilicone resins, amino-modified silicone resins, and amino-modified organofluorosilicone resins, and is a different resin from the first low refractive index resin.

[0046] In the present invention, selecting different resins as the first low refractive index resin and the second low refractive index resin can ensure that they have different refractive indices.

[0047] Furthermore, in step (1), the black polyester melt contains carbon black, and the mass content of the carbon black is 1.2% - 3.0%;

[0048] Preferably, the temperature of the black polyester melt is 280 - 290 °C;

[0049] Preferably, the black polyester melt is extruded from the spinneret holes, and after being coated with the pre-spinning oil agent and wound into a bucket, the black polyester undrawn yarn is obtained;

[0050] More preferably, the winding speed for preparing the black polyester undrawn yarn is 1150 - 1550 m / min.

[0051] In the preparation method of the present invention, by coating low-refractive-index resin aqueous emulsions with different refractive indices twice during the melt spinning process, two layers of low-refractive-index resin films with refractive indices not higher than 1.5 and different from each other can be coated on the surface of the prepared ultra-black low-shrinkage polyester staple fibers, thereby achieving a darkening effect on the fibers. The mass content of carbon black in the black polyester melt for spinning is controlled at 1.2% to 3.0%. By adopting the preparation method of the present invention, the black-white index L value of the prepared ultra-black low-shrinkage polyester staple fibers can be controlled within a range of not higher than 17.6.

[0052] As a specific embodiment, the present invention adopts the following preparation method to prepare the ultra-black low-shrinkage polyester staple fiber:

[0053] (1) a black polyester melt having a carbon black content of 1.2% to 3.0% by mass is extruded from a spinneret, coated with a pre-spinning oil agent, and wound into a barrel to obtain a black polyester undrawn yarn, wherein the black polyester melt temperature is 280 to 290° C. and the winding speed is 1150 to 1550 m / min;

[0054] (2) After being bundled by a guide wire rack, the black polyester undrawn yarn is drawn into an impregnation tank by a guide wire machine, and is fully impregnated with a first low refractive index resin aqueous emulsion in the impregnation tank, and then is subjected to a first drawing machine and a second drawing machine for a first drawing under room temperature air, with a drawing ratio of 2.18 to 2.80; then, after the second drawing machine, it enters a hot air heating box, and the yarn bundle is subjected to a second drawing between the second drawing machine and a tension heat setting machine with hot air at 140 to 160° C. as a drawing medium, with a drawing ratio of 1.18 to 1.33, to obtain a low refractive index resin coated black polyester drawn yarn; wherein the first low refractive index resin aqueous emulsion contains a first low refractive index resin having a refractive index not higher than 1.5, and its mass content is 4% to 6%;

[0055] (3) The low refractive index resin coated black polyester drawn yarn is subjected to tension heat setting in a tension heat setting machine to obtain a low refractive index resin coated black polyester tension heat setting yarn, wherein the temperature of the hot roller of the tension heat setting machine is 180 to 210° C., and the yarn residence time is 12 to 20 seconds;

[0056] (4) The black polyester tension heat-setting filaments coated with the low refractive index resin are subjected to spraying with the aqueous emulsion of the second low refractive index resin, then baked and set by a hot roll traction machine, and then enter a relaxation heat-setting machine for relaxation heat setting after passing through the post-spinning oil agent coating process and the crimping process, to obtain the black polyester relaxation heat-setting filaments coated with the low refractive index resin twice; wherein, the aqueous emulsion of the second low refractive index resin used for spraying contains a second low refractive index resin with a refractive index not higher than 1.5 and different from that of the first low refractive index resin, and its mass content is 1% to 4%; the heating roll temperature of the hot roll traction machine is 110 to 140 °C, the residence time of the filament bundle is 4 to 6 s, the heating temperature of the relaxation heat-setting machine is 100 to 130 °C, and the residence time of the filament bundle is 6 to 10 min;

[0057] (5) The black polyester relaxation heat-setting filaments coated with the low refractive index resin twice are subjected to a cutting process and a packing process to obtain the finished product of super black low-shrinkage polyester staple fibers.

[0058] The second object of the present invention is to provide a super black low-shrinkage polyester staple fiber, which comprises a black polyester fiber matrix, and a first low refractive index resin layer and a second low refractive index resin layer sequentially wrapped on the black polyester fiber matrix; the refractive indices of the first low refractive index resin layer and the second low refractive index resin layer are different and both are not higher than 1.5;

[0059] Preferably, the mass content of carbon black in the black polyester fiber matrix is 1.2% to 3.0%, the L value of the black and white index of the super black low-shrinkage polyester staple fiber is not higher than 17.6, the dry heat shrinkage rate at 180 °C is not higher than 4.2%, and the soaping color fastness is not lower than 4-5 grades.

[0060] In the above solution, the super black low-shrinkage polyester staple fiber can be prepared by the preparation method of the super black low-shrinkage polyester staple fiber provided by the first object of the present invention.

[0061] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0062] 1. For the super black low-shrinkage polyester staple fiber provided by the present invention, during the preparation process, by successively coating the aqueous emulsions of low refractive index resins with refractive indices not higher than 1.5 and different, and cooperating with the heating process after coating, a firmly fixed and two-layer low refractive index resin film with different refractive indices is formed on the surface of the black polyester fiber, which can reduce the reflection of light on the fiber surface, enable more incident light to enter the fiber interior and be absorbed by the carbon black pigment, thereby achieving the effect of deepening the color.

[0063] 2. During the preparation process, the tow is drawn twice after being impregnated with the first low refractive index resin aqueous emulsion, and the second drawing uses hot air as the drawing medium, and then is subjected to tensile heat setting. The resin film formed by the first low refractive index resin is firmly attached to the fiber surface through two heatings; after the second low refractive index resin aqueous emulsion is sprayed, it also undergoes heating baking setting and relaxation heat setting processes, which on the one hand make the second low refractive index resin firmly adhere, and on the other hand cooperate with the tensile heat setting process, through a total of three high-temperature setting processes to improve the dimensional stability of the obtained short fibers, and can obtain ultra-black low-shrinkage polyester short fibers with both high blackness and low dry heat shrinkage, which are particularly suitable for processing into ultra-black sewing threads with high dimensional stability.

[0064] 3. In the present invention, when a black polyester raw material containing 1.2% to 3.0% carbon black is used for preparation, a black and white index L value of not higher than 17.6, a 180°C dry heat shrinkage rate of not higher than 4.2%, and a soap-washing color fastness of not lower than grade 4-5 can be obtained.

[0065] The specific embodiments of the present invention are described in further detail below. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0067] Example 1

[0068] In this embodiment, the ultra-black low-shrinkage polyester staple fibers are prepared according to the following steps:

[0069] (1) A black polyester melt having a carbon black content of 1.2% by mass is extruded from a spinneret, coated with a pre-spinning oil agent, and wound into a barrel to obtain a black polyester undrawn yarn, wherein the black polyester melt temperature is 290° C. and the winding speed is 1550 m / min;

[0070] (2) After being bundled by a guide wire rack, the black polyester unstretched yarn is pulled into an impregnation tank by a guide wire machine, and is fully impregnated with a first low-refractive index resin aqueous emulsion in the impregnation tank, and then is subjected to a first stretching process by a first stretching machine and a second stretching machine under room temperature air, with a stretching ratio of 2.18; then, after being subjected to the second stretching machine, the yarn enters a hot air heating box, and the yarn bundle is subjected to a second stretching process by using 160° C. hot air as a stretching medium between the second stretching machine and a tension heat setting machine, with a stretching ratio of 1.33, to obtain a low-refractive index resin-coated black polyester stretched yarn; wherein the first low-refractive index resin aqueous emulsion contains a cationic acrylic resin having a refractive index not higher than 1.5, and the mass content of the cationic acrylic resin is 4%;

[0071] (3) The low refractive index resin coated black polyester drawn yarn is subjected to tension heat setting in a tension heat setting machine to obtain a low refractive index resin coated black polyester tension heat setting yarn, wherein the hot roller temperature of the tension heat setting machine is 210° C. and the yarn residence time is 12 seconds;

[0072] (4) The low refractive index resin coated black polyester tension heat-set yarn is sprayed with a second low refractive index resin aqueous emulsion, then baked and set in a hot roller traction machine, and then enters a relaxation heat-setting machine for relaxation heat-setting after a post-spinning oil coating process and a curling process, to obtain a low refractive index resin twice coated black polyester relaxation heat-set yarn; wherein the second low refractive index resin aqueous emulsion for spraying contains a quaternized organic fluorosilicone resin with a refractive index not higher than 1.5, and its mass content is 2%; the heating roller temperature of the hot roller traction machine is 140°C, the yarn bundle residence time is 4s, the heating temperature of the relaxation heat-setting machine is 130°C, and the yarn bundle residence time is 6min;

[0073] (5) The low refractive index resin is coated twice on the black polyester relaxed heat-set yarn, and the yarn is cut and packaged to obtain a finished product of ultra-black low-shrinkage polyester staple fiber.

[0074] Example 2

[0075] In this embodiment, the ultra-black low-shrinkage polyester staple fibers are prepared according to the following steps:

[0076] (1) A black polyester melt having a carbon black mass content of 1.5% is extruded from a spinneret, coated with a pre-spinning oil agent, and wound into a barrel to obtain a black polyester undrawn yarn, wherein the black polyester melt temperature is 288° C. and the winding speed is 1455 m / min;

[0077] (2) After being bundled by a guide wire rack, the black polyester unstretched yarn is pulled into an impregnation tank by a guide wire machine, and is fully impregnated with a first low-refractive index resin aqueous emulsion in the impregnation tank, and then is subjected to a first stretching process by a first stretching machine and a second stretching machine under room temperature air, with a stretching ratio of 2.37; then, after being subjected to the second stretching machine, it enters a hot air heating box, and the yarn bundle is subjected to a second stretching process by using 160° C. hot air as a stretching medium between the second stretching machine and a tension heat setting machine, with a stretching ratio of 1.30, to obtain a low-refractive index resin-coated black polyester stretched yarn; wherein the first low-refractive index resin aqueous emulsion contains a quaternized organic fluorosilicone resin having a refractive index not higher than 1.5, and its mass content is 4%;

[0078] (3) The low refractive index resin coated black polyester drawn yarn is subjected to tension heat setting in a tension heat setting machine to obtain a low refractive index resin coated black polyester tension heat setting yarn, wherein the hot roller temperature of the tension heat setting machine is 210° C. and the yarn residence time is 20 s;

[0079] (4) The low refractive index resin coated black polyester tension heat-setting yarn is sprayed with a second low refractive index resin aqueous emulsion, then baked and set in a hot roller traction machine, and then enters a relaxation heat-setting machine for relaxation heat-setting after a post-spinning oil coating process and a curling process, to obtain a low refractive index resin twice coated black polyester relaxation heat-setting yarn; wherein the second low refractive index resin aqueous emulsion for spraying contains a polyether modified silicone resin with a refractive index not higher than 1.5, and its mass content is 4%; the heating roller temperature of the hot roller traction machine is 120°C, the yarn bundle residence time is 6s, the heating temperature of the relaxation heat-setting machine is 120°C, and the yarn bundle residence time is 10min;

[0080] (5) The low refractive index resin is coated twice on the black polyester relaxed heat-set yarn, and the yarn is cut and packaged to obtain a finished product of ultra-black low-shrinkage polyester staple fiber.

[0081] Example 3

[0082] In this embodiment, the ultra-black low-shrinkage polyester staple fibers are prepared according to the following steps:

[0083] (1) A black polyester melt having a carbon black content of 2.0% by mass is extruded from a spinneret, coated with a pre-spinning oil agent, and wound into a barrel to obtain a black polyester undrawn yarn, wherein the black polyester melt temperature is 286° C. and the winding speed is 1320 m / min;

[0084] (2) After being bundled by a guide wire rack, the black polyester unstretched yarn is pulled into an impregnation tank by a guide wire machine, and is fully impregnated with a first low-refractive index resin aqueous emulsion in the impregnation tank, and then is subjected to a first stretching process by a first stretching machine and a second stretching machine under room temperature air, with a stretching ratio of 2.58; then, after being subjected to the second stretching machine, it enters a hot air heating box, and the yarn bundle is subjected to a second stretching process by a hot air of 140° C. as a stretching medium between the second stretching machine and a tension heat setting machine, with a stretching ratio of 1.28, to obtain a low-refractive index resin-coated black polyester stretched yarn; wherein the first low-refractive index resin aqueous emulsion contains a quaternized organic fluorosilicone resin having a refractive index not higher than 1.5, and its mass content is 2%;

[0085] (3) The low refractive index resin coated black polyester drawn yarn is subjected to tension heat setting in a tension heat setting machine to obtain a low refractive index resin coated black polyester tension heat setting yarn, wherein the hot roller temperature of the tension heat setting machine is 180° C. and the yarn residence time is 16 seconds;

[0086] (4) The low refractive index resin coated black polyester tension heat-setting yarn is sprayed with a second low refractive index resin aqueous emulsion, then baked and set in a hot roller traction machine, and then enters a relaxation heat-setting machine for relaxation heat-setting after a post-spinning oil coating process and a curling process, thereby obtaining a low refractive index resin twice coated black polyester relaxation heat-setting yarn; wherein the second low refractive index resin aqueous emulsion for spraying contains a polyether-modified silicone resin with a refractive index not higher than 1.5, and its mass content is 1%; the heating roller temperature of the hot roller traction machine is 110° C., the yarn bundle residence time is 5 s, the heating temperature of the relaxation heat-setting machine is 100° C., and the yarn bundle residence time is 8 min;

[0087] (5) The low refractive index resin is coated twice on the black polyester relaxed heat-set yarn, and the yarn is cut and packaged to obtain a finished product of ultra-black low-shrinkage polyester staple fiber.

[0088] Example 4

[0089] In this embodiment, the ultra-black low-shrinkage polyester staple fibers are prepared according to the following steps:

[0090] (1) A black polyester melt having a carbon black content of 2.4% by mass is extruded from a spinneret, coated with a pre-spinning oil agent, and wound into a barrel to obtain a black polyester undrawn yarn, wherein the black polyester melt temperature is 283° C. and the winding speed is 1320 m / min;

[0091] (2) After being bundled by a guide wire rack, the black polyester unstretched yarn is pulled into an impregnation tank by a guide wire machine, and is fully impregnated with a first low-refractive index resin aqueous emulsion in the impregnation tank, and then is subjected to a first stretching process by a first stretching machine and a second stretching machine under room temperature air, with a stretching ratio of 2.58; then, after being subjected to the second stretching machine, it enters a hot air heating box, and the yarn bundle is subjected to a second stretching process by using 150° C. hot air as a stretching medium between the second stretching machine and a tension heat setting machine, with a stretching ratio of 1.28, to obtain a low-refractive index resin-coated black polyester stretched yarn; wherein the first low-refractive index resin aqueous emulsion contains an amino-modified silicone resin having a refractive index not higher than 1.5, and its mass content is 3%;

[0092] (3) The low refractive index resin coated black polyester drawn yarn is subjected to tension heat setting in a tension heat setting machine to obtain a low refractive index resin coated black polyester tension heat setting yarn, wherein the hot roller temperature of the tension heat setting machine is 195° C. and the yarn residence time is 16 seconds;

[0093] (4) The low refractive index resin coated black polyester tension heat-set yarn is sprayed with a second low refractive index resin aqueous emulsion, then baked and set in a hot roller traction machine, and then enters a relaxation heat-setting machine for relaxation heat-setting after a post-spinning oil coating process and a curling process, to obtain a low refractive index resin twice coated black polyester relaxation heat-set yarn; wherein the second low refractive index resin aqueous emulsion for spraying contains a quaternary ammonium silicone resin with a refractive index not higher than 1.5, and its mass content is 2%; the heating roller temperature of the hot roller traction machine is 130° C., the yarn bundle residence time is 5 s, the heating temperature of the relaxation heat-setting machine is 120° C., and the yarn bundle residence time is 8 min;

[0094] (5) The low refractive index resin is coated twice on the black polyester relaxed heat-set yarn, and the yarn is cut and packaged to obtain a finished product of ultra-black low-shrinkage polyester staple fiber.

[0095] Example 5

[0096] In this embodiment, the ultra-black low-shrinkage polyester staple fibers are prepared according to the following steps:

[0097] (1) A black polyester melt having a carbon black mass content of 3.0% is extruded from a spinneret, coated with a pre-spinning oil agent, and wound into a barrel to obtain a black polyester undrawn yarn, wherein the black polyester melt temperature is 288° C. and the winding speed is 1455 m / min;

[0098] (2) After being bundled by a guide wire rack, the black polyester unstretched yarn is pulled into an impregnation tank by a guide wire machine, and is fully impregnated with a first low-refractive index resin aqueous emulsion in the impregnation tank, and then is subjected to a first stretching process by a first stretching machine and a second stretching machine under room temperature air, with a stretching ratio of 2.80; then, after being subjected to a second stretching process, the yarn enters a hot air heating box, and the yarn bundle is subjected to a second stretching process by using 140° C. hot air as a stretching medium between the second stretching machine and a tension heat setting machine, with a stretching ratio of 1.18, to obtain a low-refractive index resin-coated black polyester drawn yarn; wherein the first low-refractive index resin aqueous emulsion contains an amino-modified organic fluorosilicone resin having a refractive index not higher than 1.5, and the mass content of the amino-modified organic fluorosilicone resin is 2%;

[0099] (3) The low refractive index resin coated black polyester drawn yarn is subjected to tension heat setting in a tension heat setting machine to obtain a low refractive index resin coated black polyester tension heat setting yarn, wherein the hot roller temperature of the tension heat setting machine is 180° C. and the yarn residence time is 16 seconds;

[0100] (4) The low refractive index resin coated black polyester tension heat-setting yarn is sprayed with a second low refractive index resin aqueous emulsion, and then baked and set in a hot roller traction machine, and then enters a relaxation heat-setting machine for relaxation heat-setting after a post-spinning oil coating process and a curling process, to obtain a low refractive index resin twice coated black polyester relaxation heat-setting yarn; wherein the second low refractive index resin aqueous emulsion for spraying contains an amino-modified silicone resin with a refractive index not higher than 1.5, and its mass content is 2%; the heating roller temperature of the hot roller traction machine is 120° C., the yarn bundle residence time is 5 s, the heating temperature of the relaxation heat-setting machine is 120° C., and the yarn bundle residence time is 8 min;

[0101] (5) The low refractive index resin is coated twice on the black polyester relaxed heat-set yarn, and the yarn is cut and packaged to obtain a finished product of ultra-black low-shrinkage polyester staple fiber.

[0102] Example 6

[0103] In this embodiment, the ultra-black low-shrinkage polyester staple fibers are prepared according to the following steps:

[0104] (1) A black polyester melt having a carbon black content of 1.8% by mass is extruded from a spinneret, coated with a pre-spinning oil agent, and wound into a barrel to obtain a black polyester undrawn yarn, wherein the black polyester melt temperature is 284° C. and the winding speed is 1360 m / min;

[0105] (2) After being bundled by a guide wire rack, the black polyester unstretched yarn is pulled into an impregnation tank by a guide wire machine, and is fully impregnated with a first low-refractive index resin aqueous emulsion in the impregnation tank, and then is subjected to a first stretching process by a first stretching machine and a second stretching machine under room temperature air, with a stretching ratio of 2.42; then, after being subjected to a second stretching process, the yarn bundle is subjected to a second stretching process by a hot air heating box between the second stretching machine and a tension heat setting machine with 150° C. hot air as a stretching medium, with a stretching ratio of 1.29, to obtain a low-refractive index resin-coated black polyester stretched yarn; wherein the first low-refractive index resin aqueous emulsion contains a quaternary ammonium silicone resin having a refractive index not higher than 1.5, and the mass content of the quaternary ammonium silicone resin is 4%;

[0106] (3) The low refractive index resin coated black polyester drawn yarn is subjected to tension heat setting in a tension heat setting machine to obtain a low refractive index resin coated black polyester tension heat setting yarn, wherein the hot roller temperature of the tension heat setting machine is 200° C. and the yarn residence time is 16 seconds;

[0107] (4) The black polyester tension heat-setting filaments coated with the low refractive index resin are subjected to spraying with the second aqueous emulsion of the low refractive index resin, then baked and set by a hot roller traction machine, and then enter a relaxation heat-setting machine for relaxation heat setting after passing through the post-spinning oil agent coating process and the crimping process, obtaining black polyester relaxation heat-setting filaments with two coatings of the low refractive index resin; wherein, the second aqueous emulsion of the low refractive index resin for spraying contains an amino-modified organofluorosilicon resin with a refractive index not higher than 1.5, and its mass content is 3%; the heating roller temperature of the hot roller traction machine is 130 °C, the residence time of the filament bundle is 5 s, the heating temperature of the relaxation heat-setting machine is 130 °C, and the residence time of the filament bundle is 8 min;

[0108] (5) The black polyester relaxation heat-setting filaments with two coatings of the low refractive index resin are subjected to a cutting process and a packing process to obtain finished super-black low-shrinkage polyester staple fibers.

[0109] Comparative Example 1

[0110] The preparation of black polyester staple fibers in this comparative example is carried out according to the following steps:

[0111] (1) The black polyester melt with a carbon black mass content of 1.2% is extruded from the spinneret holes, and after being coated with the pre-spinning oil agent and wound into a bucket, black polyester undrawn filaments are obtained, wherein, the temperature of the black polyester melt is 290 °C, and the winding speed is 1550 m / min;

[0112] (2) After the black polyester undrawn filaments are bundled by a godet frame, they are led into a water bath through a godet machine to wash off the pre-spinning oil agent, and then subjected to the first drawing at room temperature air by a first drawframe and a second drawframe, with a draw ratio of 2.18; then, after passing through the second drawframe, they enter a steam heating box, and the filament bundle is subjected to the second drawing with 140 °C steam as the drawing medium between the second drawframe and the tension heat-setting machine, with a draw ratio of 1.33, obtaining black polyester drawn filaments;

[0113] (3) The black polyester drawn filaments are subjected to tension heat setting by a tension heat-setting machine, obtaining black polyester tension heat-setting filaments, wherein, the hot roller temperature of the tension heat-setting machine is 210 °C, and the residence time of the filament bundle is 12 s;

[0114] (4) The black polyester tension heat-setting filaments are subjected to desalted water spraying, then cooled by a filament cooler, and then enter a relaxation heat-setting machine for relaxation heat setting after passing through the post-spinning oil agent coating process and the crimping process, obtaining black polyester relaxation heat-setting filaments; wherein, the temperature of the filament cooler is 55 °C, the residence time of the filament bundle is 4 s, the heating temperature of the relaxation heat-setting machine is 80 °C, and the residence time of the filament bundle is 6 min;

[0115] (5) The black polyester relaxation heat-setting filaments are subjected to a cutting process and a packing process to obtain finished black polyester staple fibers.

[0116] Comparative Example 2

[0117] The difference between this comparative example and the above-mentioned Example 1 lies in that the process in step (4) is replaced as follows:

[0118] (4) The low refractive index resin-coated black polyester drawn heat-setting filaments are sprayed with a second low refractive index resin aqueous emulsion, and then enter the relaxation heat-setting machine for relaxation heat-setting after passing through the post-spinning oil agent coating process and the crimping process, obtaining low refractive index resin double-coated black polyester relaxation heat-setting filaments; wherein, the second low refractive index resin aqueous emulsion for spraying contains a quaternized organofluorosilicon resin with a refractive index not higher than 1.5, and its mass content is 2%; the heating temperature of the relaxation heat-setting machine is 130 °C, and the residence time of the filament bundle is 6 min.

[0119] The processes and parameters of other steps in this comparative example are the same as those in Example 1.

[0120] Test Example 1

[0121] This test example conducted relevant performance tests on the polyester staple fibers prepared in the above-mentioned Examples 1-6 and Comparative Examples 1 and 2. The specific test items and test methods are as follows.

[0122] Dry heat shrinkage rate at 180 °C: The test method refers to FZ / T 50004-2011;

[0123] Black and white index L value: Weigh 1 g of the polyester staple fiber sample to be tested, manually comb the staple fibers smoothly and stack them layer by layer into the HunterLab loose fiber clip, ensuring that the staple fibers on the test surface are arranged neatly and smoothly. Then place the test surface of the HunterLab loose fiber clip on the measuring hole of the DATACOLOR 400 spectrophotometer (D65 light source, 10° viewing angle, HunterLab color system) to measure the black and white index L value of the staple fiber sample. Take the average value of five groups of test data;

[0124] Soaping color fastness: The test method refers to GB / T 3921-2008.

[0125] The test results of this test example are shown in Table 1 below.

[0126] Table 1

[0127]

[0128] As can be seen from the above test results, the black-and-white index L values characterizing the blackness of the super black and low shrinkage polyester staple fibers prepared in Examples 1 to 6 are all not higher than 17.6, the dry heat shrinkage rate at 180°C characterizing the dimensional stability is all not higher than 4.2%, and the soaping color fastness characterizing the color fastness is not lower than Grade 4-5, indicating that they all have the performance characteristics of high blackness and low dry heat shrinkage rate, and the surface-coated low refractive index resin is firmly fixed.

[0129] Compared with Example 1, the carbon black mass content in the black polyester melt used in Comparative Example 1 is 1.2%. However, for the black polyester staple fibers prepared in Comparative Example 1, the black-and-white index L value is 19.1, the dry heat shrinkage rate at 180°C is 5.3%, and the soaping color fastness is Grade 4, which has lower blackness, larger dry heat shrinkage rate, and lower soaping color fastness than the staple fibers prepared in Example 1. Specifically, compared with Example 1, the short fibers prepared in Comparative Example 1 are 1.5 higher in the black-and-white index L value, 2.0% higher in the dry heat shrinkage rate at 180°C, and 1 grade lower in the soaping color fastness. It can be shown that in Example 1, the preparation method of the present invention is adopted. Before the two drawing processes and after the tension heat setting process, a cationic acrylic resin aqueous emulsion and a quaternized organofluorosilicon resin aqueous emulsion with a refractive index not higher than 1.5 are respectively coated, and two low refractive index resin films with different refractive indices are firmly formed on the surface of the black polyester fiber through heat treatment, effectively reducing the reflection of light on the fiber surface, enabling more incident light to enter the fiber interior and be absorbed by the carbon black pigment, thereby achieving the effect of deepening the color; at the same time, the low refractive index resin film firmly fixed on the surface of the black polyester fiber further improves the fastness of the carbon black pigment to soaping. In addition, different from the post-processing process in Comparative Example 1 where the second drawing uses steam as the drawing medium and the tow is cooled by a tow cooler before the post-spinning oil coating process, in Example 1, the second drawing uses high-temperature hot air directly sprayed on the surface of the tow as the drawing medium, and the tow is baked and shaped by a hot roll traction machine before the post-spinning oil coating process, and a higher relaxation heat setting heating temperature is adopted. Therefore, the prepared staple fibers have more excellent dimensional stability performance due to the more perfect supramolecular structure and more sufficient relaxation of internal stress, and their dry heat shrinkage rate at 180°C is also lower.

[0130] Comparative Example 2 and Example 1 used black polyester melts with a carbon black mass content of 1.2%. However, for the black polyester staple fibers prepared in Comparative Example 2, the black and white index L value was 18.2, the dry heat shrinkage rate at 180°C was 4.3%, and the soaping color fastness was 4-5 levels. Compared with the staple fibers prepared in Example 1, the blackness was lower, the dry heat shrinkage rate was higher, and the soaping color fastness was lower. Specifically, compared with Example 1, the staple fibers prepared in Comparative Example 2 had a higher black and white index L value by 0.6, a higher dry heat shrinkage rate at 180°C by 1.0%, and a half-level reduction in soaping color fastness. It can be shown that for the low refractive index resin-coated black polyester tension heat-set filaments prepared in Comparative Example 2, after spraying with the second low refractive index resin aqueous emulsion and without baking and setting directly, the second low refractive index resin aqueous emulsion partially coated on the surface of the black polyester fibers was washed away by the applied post-spinning oil agent during the post-spinning oil agent coating process. Therefore, while the deepening effect decreased and the L value of the black polyester staple fibers increased, the soaping color fastness also decreased. In addition, the omission of the baking and setting process would also lead to a decrease in the perfection degree of the supramolecular structure and dimensional stability of the black polyester fibers, and an increase in the dry heat shrinkage rate at 180°C.

[0131] The above description is only a preferred embodiment of the present invention and does not impose any formal restrictions on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art of this patent, without departing from the scope of the technical solution of the present invention, can make some changes or modifications using the technical content prompted above as equivalent embodiments of equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the present invention's solution.

Claims

1. A method for preparing super black and low shrinkage polyester staple fibers, characterized in that, It includes the following steps: (1) The black polyester melt is extruded from the spinneret holes and coated with a spinning oil for the pre-spinning process to obtain black polyester undrawn filaments; (2) The black polyester undrawn filaments are impregnated with a first low refractive index resin aqueous emulsion, then subjected to a first drawing process, and then a second drawing process using hot air as the drawing medium to obtain black polyester drawn filaments coated with a low refractive index resin; (3) The black polyester drawn filaments coated with a low refractive index resin are subjected to a tension heat setting process to obtain black polyester tension heat set filaments coated with a low refractive index resin; (4) The black polyester tension heat set filaments coated with a low refractive index resin are sprayed with a second low refractive index resin aqueous emulsion, then heated for baking and setting, and then after being coated with a spinning oil for the post-spinning process and a crimping process, a relaxation heat setting process is carried out to obtain black polyester relaxation heat set filaments coated with a low refractive index resin twice; (5) The black polyester relaxation heat set filaments coated with a low refractive index resin twice are subjected to a cutting process and a packing process to obtain finished super black low shrinkage polyester staple fibers; Among them, the first low refractive index resin aqueous emulsion contains a first low refractive index resin, and the second low refractive index resin aqueous emulsion contains a second low refractive index resin; the refractive indices of the first low refractive index resin and the second low refractive index resin are different and both are not higher than 1.

5.

2. The preparation method of the super black and low shrinkage polyester staple fiber according to claim 1, characterized in that, In step (2), the mass content of the first low refractive index resin in the first low refractive index resin aqueous emulsion is 2% - 6%.

3. The preparation method of the super black and low shrinkage polyester staple fiber according to claim 1 or 2, characterized in that, In step (2), the drawing medium for the first drawing process is room temperature air, and the drawing ratio is 2.18 - 2.80; when carrying out the second drawing process, the temperature of the hot air is 140 - 160 °C, and the drawing ratio is 1.18 - 1.33; Preferably, the second drawing process is carried out in a hot air heating box, and the hot air is sprayed onto the surface of the filament bundle as the drawing medium for the second drawing process.

4. The preparation method of the super black and low shrinkage polyester staple fiber according to any one of claims 1-3, characterized in that, In step (4), the mass content of the second low refractive index resin in the second low refractive index resin aqueous emulsion is 1% - 4%.

5. The preparation method of the super black and low shrinkage polyester staple fiber according to any one of claims 1-4, characterized in that, In step (3), the heating temperature for the tension heat setting process is 180 - 210 °C, and the residence time of the filament bundle is 12 - 20 s.

6. The preparation method of the super black and low shrinkage polyester staple fiber according to any one of claims 1-5, characterized in that, In step (4), the heating temperature for the baking and setting process is 110 - 140 °C, and the residence time of the filament bundle is 4 - 6 s; Preferably, the filament bundle is subjected to baking and setting by a hot roll traction machine, and the temperature of the heating roll of the hot roll traction machine is controlled at 110 - 140 °C.

7. The preparation method of the super black and low shrinkage polyester staple fiber according to any one of claims 1-6, characterized in that, In step (4), the heating temperature for the relaxation heat setting process is 100 - 130 °C, and the residence time of the filament bundle is 6 - 10 min; Preferably, the heating temperature for the relaxation heat setting process is 120 - 130 °C.

8. The preparation method of the super black and low shrinkage polyester staple fiber according to any one of claims 1-7, characterized in that, Both the first low refractive index resin and the second low refractive index resin are selected from one or a combination of several of cationic acrylic resin, polyether modified silicone resin, quaternized silicone resin, quaternized fluorosilicone resin, amino modified silicone resin, and amino modified fluorosilicone resin, and the compositions of the first low refractive index resin and the second low refractive index resin are different.

9. The preparation method of the super black and low shrinkage polyester staple fiber according to any one of claims 1-8, characterized in that, In step (1), the black polyester melt contains carbon black, and the mass content of the carbon black is 1.2% - 3.0%; Preferably, the temperature of the black polyester melt is 280 - 290 °C; Preferably, the black polyester melt is extruded from the spinneret holes, coated with a spinning oil agent in the front spinning process, and wound into a barrel to obtain the black undrawn polyester filaments; More preferably, the winding speed for preparing the black undrawn polyester filaments is 1150 - 1550 m / min.

10. A super black and low shrinkage polyester staple fiber, characterized in that, It includes a black polyester fiber matrix, and a first low refractive index resin layer and a second low refractive index resin layer that are sequentially wrapped on the black polyester fiber matrix; the refractive indices of the first low refractive index resin layer and the second low refractive index resin layer are different and both are not higher than 1.5; Preferably, the mass content of carbon black in the black polyester fiber matrix is 1.2% - 3.0%, the L value of the black - and - white index of the super - black low - shrinkage polyester staple fiber is not higher than 17.6, the dry heat shrinkage rate at 180 °C is not higher than 4.2%, and the color fastness to soaping is not lower than grade 4 - 5; Preferably, the super - black low - shrinkage polyester staple fiber is prepared by the preparation method of the super - black low - shrinkage polyester staple fiber according to any one of claims 1 - 9.

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