Special fiber for wall cloth embroidery thread and production method thereof

Abstract

The present invention discloses a production method for special fibers for wall cloth embroidery thread, comprising the following steps: S1, melting purified terephthalic acid (PTA) and ethylene glycol (EG) into polyester to form a polyester melt having an intrinsic viscosity of 0.620-0.630 dL / g and a terminal carboxyl group of 42-46 mol / t; S2, drying a fully matte slice, extruding it through a screw extruder, and filtering it to form a matte melt; S3, converging the polyester melt and the matte melt through a melt pipe, injecting them into a dynamic mixer for thorough mixing and stirring; and S4, the mixed melt is again introduced into a static mixer for mixing, then transported outwards and extruded through a spinneret assembly to form special fibers for special-shaped wall cloth embroidery thread. The method can solve the problem of incomplete performance of existing polyester filament embroidery thread when used as wall cloth embroidery thread, making the woven fabric more colorful and having a better three-dimensional effect after dyeing, while having higher breaking strength and sunlight resistance.

Description

Technical Field

[0001] The invention relates to the technical field of textile fabrics and processes, and in particular to a special fiber for wall cloth embroidery thread and a production method thereof. Background Art

[0002] Polyester filament embroidery thread is a key textile accessory, widely used in clothing, shoes, hats, home textiles, and other fields. Embroidery thread plays a crucial role in the finishing touch of textiles, clothing, and wall coverings. Compared to wallpaper, wall coverings offer a less diverse range of colors and patterns. In recent years, the trend toward minimalist, modern styles, such as those favored by Nordic styles, has led most families to adopt less demanding colors and patterns. However, as consumer demand grows and diversifies, personalized wall coverings with vibrant colors, a stronger three-dimensional effect, and exquisite patterns are poised to gain popularity in more households. Wall coverings inlaid with dazzling silk threads can enhance their elegance and splendor, promising a broad market prospect.

[0003] Currently, polyester embroidery floss on the market primarily features glossy, shaped, and semi-gloss, circular-hole cross-sections. Glossy, shaped-cross-section embroidery floss is produced using spinnerets with special shapes, such as triangles and pentagons. The high light reflection from the shaped cross-section gives the floss a diamond-like shimmer. Furthermore, the larger surface area of ​​shaped-cross-section fibers allows for faster dyeing, resulting in a more vibrant embroidery floss under the same dyeing conditions. However, due to the shaped cross-section, the fiber's breaking strength is relatively poor, leading to more breakage during machine embroidery, impacting weaving efficiency. Furthermore, embroidery floss is susceptible to aging and deformation after prolonged exposure to sunlight. While embroidery floss with semi-gloss, circular-hole cross-sections offers high strength and dimensional stability, it suffers from the poor dyeing properties of standard polyester filament yarns and cannot meet the demand for vibrant colors and a three-dimensional effect.

[0004] Therefore, there is a need for a special fiber for wall cloth embroidery thread that is high-strength, sunlight-resistant, colorful, dimensionally stable, and has a strong three-dimensional effect, so as to solve the problem of incomplete performance of existing polyester filament embroidery thread when used as wall cloth embroidery thread. Summary of the Invention

[0005] In order to solve certain technical problems existing in the prior art, one of the purposes of this application is to provide a production method for special fibers for wall cloth embroidery thread, which can improve the breaking strength of the fibers and effectively reduce the breakage rate during machine embroidery. The fibers have better anti-ultraviolet and anti-sun effects, and the anti-aging performance of the formed fibers is stable. They are not easy to age after long-term sunlight exposure, so that the manufactured wall cloths are brightly colored, stable in size, and have a strong three-dimensional sense.

[0006] The second purpose of this application is to provide a special fiber for wall cloth embroidery thread, which can solve the problem of incomplete performance of existing polyester filament embroidery thread when used as wall cloth embroidery thread, so that the woven fabric will have brighter colors and better three-dimensional effect after dyeing, while having higher breaking strength and sunlight resistance.

[0007] In order to solve the above existing technical problems, one of the objectives of this application is achieved by adopting the following technical solutions:

[0008] A method for producing special fiber for wall cloth embroidery thread, the production method comprising

[0009] S1. Purified terephthalic acid (PTA) and ethylene glycol (EG) are subjected to a first esterification, a second esterification, a preliminary polycondensation, and a final polycondensation to form a polyester melt having an intrinsic viscosity of 0.620-0.630 dL / g and a terminal carboxyl group content of 42-46 mol / t.

[0010] S2, placing a certain proportion of fully matte chips into a drying tower for drying, then injecting them into a screw extruder for injection extrusion, and outputting them outward through a filtration system to form a matte melt, wherein the fully matte chips are composed of a polyester melt and a titanium dioxide coating layer;

[0011] S3, injecting the polyester melt in S1 into the dynamic mixer through the melt pipe, and injecting the matte melt in S2 into the melt pipe through the screw extruder to perform preliminary mixing with the polyester melt, and then entering the dynamic mixer for thorough mixing and stirring;

[0012] S4. The mixed melt is sequentially conveyed into the static mixer → metering pump → spinneret extrusion → cooling and forming → first godet roller → first hot roller → second hot roller → third hot roller → fourth hot roller → fifth hot roller → network device → second godet roller → winding and forming to form the special fiber for special-shaped wall cloth embroidery thread.

[0013] Preferably, the proportion of purified terephthalic acid (PTA) in step S1 is 70-71%, the acid value of the melt obtained by the first esterification is 58-62 mg / g, and the acid value of the melt obtained by the second esterification is 23-28 mg / g.

[0014] Preferably, the purified terephthalic acid (PTA) accounts for 70-71% of the total polyester melt, while the ethylene glycol (EG) accounts for 29-30%. The molar ratio of the slurry used for ethylene glycol (EG) and purified terephthalic acid (PTA) (ie, EG / PTA) = (MEG × MPTA) / (MPTA × MEG), where the weight units of MPTA and MEG are kg, and the molecular weight of purified terephthalic acid (PTA) in MPTA is 166.13 kg / kmol, and the molecular weight of ethylene glycol (EG) in MEG is 62.07 kg / kmol.

[0015] Preferably, the titanium dioxide content in the fully matte slice is 49-51%.

[0016] Preferably, the titanium dioxide coating layer is coated titanium dioxide obtained by SiO2 coating treatment, and the content of coated titanium dioxide in the special fiber for special-shaped wall cloth embroidery thread is 2-4%.

[0017] Preferably, the inside of the spinneret assembly is filtered by spinning through two layers of 40 μm mesh metal filters.

[0018] Preferably, the filtration system includes a filter, and the filtration accuracy of the filter element of the filter is 100μ.

[0019] Preferably, the drying temperature in the drying tower is 140-145° C., the drying time is 10-11 hours, and the moisture content of the fully matte slices after drying is controlled between 30-40 ppm.

[0020] Preferably, five temperature zones are formed inside the screw extruder, wherein the temperature of zone one is 250-260°C, the temperature of zone two is 60-270°C, the temperature of zone three is 270-280°C, the temperature of zone four is 275-285°C, and the temperature of zone five is 275-285°C.

[0021] Preferably, both ends of the screw extruder are connected by flanges, and a heating mechanism is provided on the flanges, and the temperature of the flanges formed by the heating mechanism is 275-285°C.

[0022] Preferably, the screw inlet of the screw extruder is provided with a nitrogen protection device, through which the pressure of the high-pressure nitrogen is reduced to ensure the stability of the fully matt slices.

[0023] Preferably, the spinneret on the spinneret in the spinneret assembly is a triangular cross-section spinneret, the triangle is an isosceles triangle symmetrically arranged inside and outside, the vertex angle is 60-80°, the isosceles side length of the outer isosceles triangle of the spinneret is 0.25-0.35 mm, the isosceles side length of the inner isosceles triangle is 0.15-0.25 mm, and the base of the isosceles triangle cross-section of the spinneret is parallel to the ring blowing tube.

[0024] Preferably, a three-step oil-free drawing, low-ratio and low-temperature stretching method is used to stretch the cooled and formed filament bundle: the three-step oil-free drawing, low-ratio and low-temperature stretching method includes five hot rollers, wherein the stretching ratio between the first hot roller and the second hot roller is 1.05~1.3, the stretching ratio between the second hot roller and the third hot roller is 1.05~1.5, the stretching ratio between the third hot roller and the fourth hot roller is 1.3~3.0, and there is no stretching between the fourth hot roller and the fifth hot roller, the temperature of the first hot roller is 50~60℃, the temperature of the second hot roller and the third hot roller is 55~65℃, the fourth hot roller and the fifth hot roller are shaping rollers with a temperature of 125~140℃.

[0025] Preferably, the three-step oil-free low-magnification and low-temperature stretching method comprises:

[0026] Step 1: performing a preliminary heating and stretching on the cooled and formed filament bundle by adjusting the temperature and stretching ratio of the drafting zone between the first hot roller and the second hot roller;

[0027] Step 2: heating and stretching the filament bundle again by adjusting the temperature and stretching ratio of the drafting zone between the second hot roller and the third hot roller;

[0028] Step 3: The temperature and stretching ratio of the drafting zone between the third hot roller and the fourth hot roller are used for stretching and heating setting;

[0029] Step 4: Final shaping of the filament bundle is performed by adjusting the temperature of the drafting zone between the fourth hot roller and the fifth hot roller.

[0030] Preferably, the melt pipe conveying temperature in S3 is 286-288° C., the spinning box temperature is 292-296° C., the cooling air pressure for cooling and molding is 34-36 Pa, and the cooling air humidity is 75-85%.

[0031] The second purpose of this application is achieved by the following technical solution:

[0032] A special fiber for wall cloth embroidery thread. The raw materials of the special fiber for wall cloth embroidery thread include purified terephthalic acid (PTA), ethylene glycol (EG), and a full-matt slice containing a titanium dioxide coating layer. The special fiber for wall cloth embroidery thread has a breaking strength of 3.35 cN / dtex or greater, an elongation at break of 28.0-31.0%, an oil content of 1.25-1.35%, a boiling water shrinkage of 7.3-7.5%, and the number of floating threads in 18 positions within 24 hours is less than or equal to 5.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] It can improve the breaking strength of the fiber and effectively reduce the breakage rate during machine embroidery. By adding full-matt slices, the titanium dioxide coating in the full-matt slices can make the fiber have an excellent refractive index after melting, thereby making the fiber more resistant to UV and sunlight, and making the anti-aging performance of the molded fiber stable, and not easy to age after long-term sunlight exposure.

[0035] By melting the fully matte chips, adding a filtration system for filtering, and then passing the mixture through a metering pump into the melt pipe for dynamic mixing, the adverse effects of impurities in the fully matte chips on the polyester fiber can be effectively solved, making the physical properties of the polyester fiber more stable.

[0036] After the polyester melt and the matte melt converge in the melt pipe, they are first injected into the dynamic mixer for dynamic mixing, and then flow into the static mixer for static mixing, so that the melts can be fully mixed. Finally, they are injected into the spinneret assembly through a metering pump for spinneret treatment to produce special fibers for special-shaped wall cloth embroidery threads. This can not only ensure the dyeing performance of the fiber, making the fabric more colorful and with better three-dimensional effect after dyeing, but also make the fiber have higher breaking strength and sunlight resistance, so that the manufactured wall cloth is colorful, dimensionally stable, and has a strong three-dimensional effect, thereby solving the problem of incomplete performance of existing polyester filament embroidery threads when used as wall cloth embroidery threads. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0038] Below, the present application is further described in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0039] In the description of this application, it should be understood that the terms "up", "down", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on this application.

[0040] The terms "first," "second," and the like in this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0041] like Figure 1 As shown, a production method of special fiber for wall cloth embroidery thread, the production method includes

[0042] S1. Purified terephthalic acid (PTA) and ethylene glycol (EG) are subjected to a first esterification, a second esterification, a preliminary polycondensation, and a final polycondensation to form a polyester melt having an intrinsic viscosity of 0.620-0.630 dL / g and a terminal carboxyl group content of 42-46 mol / t.

[0043] S2, placing a certain proportion of fully matte chips into a drying tower for drying, then injecting them into a screw extruder for injection extrusion, and outputting them outward through a filtration system to form a matte melt, wherein the fully matte chips are composed of a polyester melt and a titanium dioxide coating layer;

[0044] S3, injecting the polyester melt in S1 into the dynamic mixer through the melt pipe, and injecting the matte melt in S2 into the melt pipe through the screw extruder to perform preliminary mixing with the polyester melt, and then entering the dynamic mixer for thorough mixing and stirring;

[0045] S4. The mixed melt is sequentially conveyed into the static mixer → metering pump → spinneret extrusion → cooling and forming → first godet roller → first hot roller → second hot roller → third hot roller → fourth hot roller → fifth hot roller → network device → second godet roller → winding and forming to form the special fiber for special-shaped wall cloth embroidery thread.

[0046] Since a typical matte melt is approximately 50% polyester melt and 50% functional particles, it contains a high level of impurities. For polyester fibers, any additive can potentially become an "impurity" that affects the polyester, especially at high addition levels. This leads to problems during the polyester fiber production process, such as poor dispersion uniformity and incompatibility with polyester macromolecules, increasing the difficulty of fiber processing and reducing the physical properties of the polyester fiber. Therefore, in the production of specialized fibers for wall covering embroidery thread, the polyester melt is esterified from purified terephthalic acid (PTA) and ethylene glycol (EG) to form a polyester melt with an intrinsic viscosity of 0.620-0.630 dL / g and a terminal carboxyl group content of 42-46 mol / t. By adjusting the properties of the polyester melt to maintain an intrinsic viscosity between 0.620-0.630 dL / g and a terminal carboxyl group content of 42-46 mol / t, the esterification rate is increased, which improves the fiber's breaking strength and effectively reduces the breakage rate during machine embroidery. By adding full-matt slices, since the full-matt slices are composed of polyester melt and titanium dioxide coating, the titanium dioxide coating in the full-matt slices can make the special fiber for special-shaped wall cloth embroidery thread have excellent refractive index after melting, thereby making the fiber's anti-ultraviolet and anti-sun effects better, and making the anti-aging performance of the special fiber for special-shaped wall cloth embroidery thread after molding stable, and not easy to age after long-term sunlight exposure.

[0047] The long melt pipeline creates a temperature gradient between the top and bottom of the pipeline, leading to uneven melt quality. To address this, a dynamic mixer is installed within the pipeline. After the matte chips are melted, they are filtered through a filtration system before being fed into the melt pipeline via a metering pump for dynamic mixing. This ensures thorough mixing of the melt and ensures uniform melt quality. The dynamic mixer is installed when the matte melt is injected into the pipeline to thoroughly mix the polyester melt and the matte melt, ensuring uniform dispersion of the matte titanium dioxide in the melt. Furthermore, the filtration system effectively mitigates the adverse effects of impurities in the matte chips on the polyester fiber, resulting in more stable physical properties for the polyester fiber. In addition, after the polyester melt and the matte melt converge in the melt pipe, they are first injected into the dynamic mixer for dynamic mixing, then flow into the static mixer for static mixing, and finally injected into the spinneret assembly through a metering pump for spinneret treatment to make special fibers for special-shaped wall cloth embroidery threads. This can not only ensure the dyeing performance of the fiber, making the fabric more colorful and with better three-dimensional effect after dyeing, but also make the fiber have higher breaking strength and sunlight resistance, so that the manufactured wall cloth is colorful, dimensionally stable, and has a strong three-dimensional effect, thereby solving the problem of incomplete performance of existing polyester filament embroidery threads when used as wall cloth embroidery threads.

[0048] A further improvement is that the proportion of purified terephthalic acid (PTA) in step S1 is 70-71%, the acid value of the melt obtained by the first esterification is 58-62 mg / g, and the acid value of the melt obtained by the second esterification is 23-28 mg / g.

[0049] According to the esterification rate formula: esterification rate = (SN-AN) * 100% / SN

[0050] SN is the saponification value (550-560 mgKOH / g), AN is the acid value

[0051] According to the formula, the acid value of the melt obtained by the first esterification is 58-62 mg / g, and the acid value of the melt obtained by the second esterification is 23-28 mg / g. The first esterification rate is ≥90% and the second esterification rate is ≥95%, ensuring the polycondensation reaction.

[0052] A further improvement is that the purified terephthalic acid (PTA) accounts for 70-71% of the total polyester melt, while the ethylene glycol (EG) accounts for 29-30%. The molar ratio of the slurry used for ethylene glycol (EG) and purified terephthalic acid (PTA) (ie, EG / PTA) = (MEG × MPTA) / (MPTA × MEG), where the weight units of MPTA and MEG are kg, the molecular weight of purified terephthalic acid (PTA) in MPTA is 166.13 kg / kmol, and the molecular weight of ethylene glycol (EG) in MEG is 62.07 kg / kmol.

[0053] According to the above formula: slurry molar ratio = ((29-30)*166.13) / ((70-71)*62.07)≈1.139, that is, EG is in excess reaction, which accelerates the esterification reaction rate and also promotes the etherification of ethylene glycol EG to form diethylene glycol (DEG). In the esterification reaction with this molar ratio: the first esterification rate ≥90%, the second esterification rate ≥95%, the first esterified diethylene glycol 0.85%, the higher esterification rate ensures the polycondensation reaction, and the diethylene glycol of about 0.85% ensures the dyeing performance of the fiber. The principle is that the ether bond in DEG will destroy the regularity of the PET macromolecular structure, resulting in an increase in the amorphous region, thereby improving the dyeing rate and dyeing rate of polyester fibers.

[0054] A further improvement is that the titanium dioxide content in the full matte slice is 49-51%; the titanium dioxide coating layer is coated titanium dioxide obtained by SiO2 coating treatment, and the content of coated titanium dioxide in the special fiber for shaped wall cloth embroidery thread is 2-4%.

[0055] In the masterbatch drying tower and injection tower, the content of the fully matte chips coated with titanium dioxide is 4-8%. The fully matte chips make the titanium dioxide content in the fiber in the matte melt 2-4%. The large refractive index of titanium dioxide (the refractive index of titanium dioxide is 2.60, and that of air is 1.00) is utilized to achieve the effects of sun resistance and UV resistance. It can absorb ultraviolet rays, reflect and scatter ultraviolet rays, and transmit visible light. At the same time, the content of titanium dioxide is generally very small when it is used now. As a result, although the product has the effects of sun resistance and UV resistance, its functional durability is poor and it is easy to age and deform. Therefore, the titanium dioxide content is increased to 49-51% of the fully matte chips content, and coated titanium dioxide is used, that is, silicon-based substances are coated on the surface of titanium dioxide. This effectively solves the problems of reduced fiber strength, poor functional durability, and easy aging and deformation after long-term sun exposure.

[0056] A further improvement is that the inside of the spinneret assembly is filtered by spinning through two layers of 40um mesh metal filter screens; the filtration system includes a filter, and the filter element of the filter has a filtration accuracy of 100μ.

[0057] To improve filtration accuracy, a sandless spinning assembly technology was adopted. Instead of adding metal sand or sea sand to filter the melt within the spinning assembly, the melt was directly filtered using two layers of 40µm mesh metal filters. This resulted in higher filtration accuracy and solved the problem of high resistance to the melt passing through the metal sand, which led to degradation after prolonged residence time, thereby reducing the problem of drifting threads. The filter element in the filter has a 100µm filter element precision. This was achieved by melting fully matte slices and adding a filtration system for filtration. The original filter element had a 25µm filter element precision, resulting in a short filter cycle, frequent drifting threads, broken ends, and fuzzy finished threads during production. Therefore, the filter element precision was adjusted to 100µm to further reduce melt viscosity degradation and effectively address the issues of drifting threads, broken ends, and fuzzy threads during spinning.

[0058] The effects of different filter element precision on spinning yarn breakage and hairy yarns are shown in Table 1. The experimental comparison data is based on the average production situation 10 days after the filter is cut.

[0059] Filter element accuracy 25μ 40μ 60μ 80μ 100μ 120μ Filter cycle 12 days 14 days 14 days 15 days 18 days 21 days Number of floating threads (times / class, 60 people) 17 21 16 16 17 16 Number of ends broken (times / shift, 60 people) 7 8 7 7 6 8 Number of yarns (60 per class) 16.1 13.5 15.8 18.1 15.7 15.9

[0060] As can be seen from Table 1, when the filter element precision is lower, the number of broken ends and the number of hair strands do not decrease as the precision increases. When the filter element precision is 100μ, the number of broken ends and the number of hair strands are less than those of increasing or decreasing filter element precision, and the cycle can also meet higher requirements. The number of hair strands is also relatively close. By controlling the filter element precision at 100μ, unexpected results are achieved in this regard.

[0061] A further improvement is that the drying temperature in the drying tower is 140-145° C., the drying time is 10-11 hours, and the moisture content of the fully matte slices after drying is controlled between 30-40 ppm.

[0062] The moisture content of undried, fully matte chips is approximately 0.05%. However, when high-moisture chips enter the melt and are exposed to temperatures exceeding 100°C, they undergo hydrolysis, and the hydrolysis rate is much higher than thermal degradation, resulting in increased yarn drift and breakage during the spinning process. Therefore, when fully matte chips are dried in a drying tower at 140-145°C for 10-11 hours, and the moisture content is controlled between 30-40 ppm after drying, these problems can be avoided.

[0063] A further improvement is that five temperature zones are formed inside the screw extruder, among which the temperature of zone one is 250-260℃, the temperature of zone two is 60-270℃, the temperature of zone three is 270-280℃, the temperature of zone four is 275-285℃, and the temperature of zone five is 275-285℃.

[0064] The dried full-dull slices enter the screw extruder, are heated and melted into a full-dull melt, and are injected into the melt-spun polyester semi-dull melt pipeline at a certain temperature, pressure and pump supply. Since the viscosity of the full-dull masterbatch is lower than that of the polyester melt, in order to ensure spinnability and improve the mixing uniformity of the full-dull masterbatch and the polyester melt in the melt pipeline after melting, the temperature and pressure of the screw zone are increased. Among them, the temperatures of each zone in the screw extruder are: zone 1 temperature is 250-260℃, zone 2 temperature is 60-270℃, zone 3 temperature is 270-280℃, zone 4 temperature is 275-285℃, zone 5 temperature is 275-285℃, and the pressure is 9~11Mp, so that they are evenly integrated together, which is beneficial to the uniformity of spinning and winding stretching of subsequent components. At the same time, in order to reduce the viscosity degradation of polyester melt during transportation, the melt pipeline transportation temperature is appropriately lowered to 286-288℃ and the spinning box temperature is lowered to 292-296℃ to ensure the best fiber spinnability.

[0065] A further improvement is that both ends of the screw extruder are connected by flanges, and a heating mechanism is provided on the flanges, and the temperature of the flanges is formed to be 275-285°C by the heating mechanism.

[0066] At the same time, since the current screw extruder connection flange does not have a heating mechanism and its temperature is relatively low, when the heated high-temperature melt passes through the unheated low-temperature flange, it will cause the temperature to drop, thereby affecting the subsequent wire production performance of the melt, resulting in increased breakage or increased drifting of the yarn. Therefore, a heating mechanism is installed on the flange. The flange is kept at a temperature between 275-285℃ through the heating mechanism, so that the melt will not shrink when passing through the flange. In particular, after the flange at the discharge end of the screw extruder is heated, the temperature of the melt entering the spinning manifold can be better guaranteed, making the yarn bundle produced by the spinning manifold more stable.

[0067] A further improvement is that the screw inlet of the screw extruder is provided with a nitrogen protection device, and the pressure of the high-pressure nitrogen is reduced by the nitrogen protection device to ensure the stability of the fully matt slices.

[0068] Existing screw extruders, due to the high temperature of the screw feed port, contain air between the matte chips. At high temperatures, the matte chips are susceptible to oxidation, degradation, and yellowing, affecting spinning quality. Furthermore, a high-pressure space can easily form within the screw extruder's pipes. If the feed pipe is not properly sealed and air is admitted, the dry matte chips can easily become damp, affecting their moisture content. The matte chips, after entering the screw and melting at high temperatures, are easily hydrolyzed, causing spun yarn breakage and compromising product quality. Therefore, a nitrogen protection device is installed at the screw extruder's inlet. This device reduces the pressure of the high-pressure nitrogen, eliminating the problem of abnormal moisture content of the chips caused by the influx of external air and preventing excessive nitrogen pressure from affecting chip feeding. This effectively reduces spinning yarn drift and product quality instability caused by unstable moisture content, thereby improving production stability. A filter is also used to filter impurities from the nitrogen to prevent them from entering the chips and affecting production. This ensures stable moisture content detection of the matte chips and reduces spun yarn breakage.

[0069] The test results of the moisture content and breakage rate of the screw extruder before and after the installation of the nitrogen protection device are shown in Table 2:

[0070] Before installation After installation Water 1 48PPm 32PPm Water 2 49PPm 38PPm Water content 3 42PPm 31PPm Floating Silk / Class / 60 people 18 4 Head cutter / shift / 60 people 21 3

[0071] It can be seen from Table 2 that after the nitrogen protection device is installed, the moisture content of the slices is stable and the phenomenon of broken ends in spinning is significantly reduced.

[0072] A further improvement is that the spinneret on the spinneret in the spinneret assembly has a triangular cross-section, the triangle is an isosceles triangle symmetrically arranged inside and outside, the vertex angle is 60-80°, the isosceles side length of the outer isosceles triangle of the spinneret is 0.25-0.35 mm, the isosceles side length of the inner isosceles triangle is 0.15-0.25 mm, and the base of the isosceles triangle cross-section of the spinneret is parallel to the ring blowing tube.

[0073] Through this spinneret cross-section, that is, the spinneret with triangular cross-section spinnerets, it is utilized that under the irradiation of light, the triangular cross-section fiber refracts, deflects and splits the light like a prism. The refracted light is dazzling and colorful, giving the embroidery thread a diamond-like sparkling effect.

[0074] A further improvement is to use a three-step oil-free drawing, low-ratio, low-temperature drawing method to draw the cooled and formed tow: the three-step oil-free drawing, low-ratio, low-temperature drawing method includes five hot rollers, wherein the drawing ratio between the first hot roller and the second hot roller is 1.05-1.3, the drawing ratio between the second hot roller and the third hot roller is 1.05-1.5, the drawing ratio between the third hot roller and the fourth hot roller is 1.3-3.0, and there is no drawing between the fourth hot roller and the fifth hot roller, the temperature of the first hot roller is 50-60°C, the temperature of the second hot roller and the third hot roller is 55-65°C, the fourth hot roller and the fifth hot roller are sizing rollers, and the temperature is 125-140°C, wherein the three-step oil-free drawing, low-ratio, low-temperature drawing method includes:

[0075] Step 1: performing a preliminary heating and stretching on the cooled and formed filament bundle by adjusting the temperature and stretching ratio of the drafting zone between the first hot roller and the second hot roller;

[0076] Step 2: heating and stretching the filament bundle again by adjusting the temperature and stretching ratio of the drafting zone between the second hot roller and the third hot roller;

[0077] Step 3, stretching and heating the product by the temperature and stretching ratio of the drafting zone between the third hot roller and the fourth hot roller;

[0078] Step 4: Final shaping of the filament bundle is performed by adjusting the temperature of the drafting zone between the fourth hot roller and the fifth hot roller.

[0079] During the stretching and shaping of the tow, the macromolecules or aggregated structural units in the fiber expand and reorganize during the stretching process, increasing crystallinity and orientation while reducing elongation at break. The lower the temperature of the hot roller and the lower the draw ratio, the more relaxed the macromolecules are, making the fiber less likely to deform, resulting in a higher degree of irregularity. Therefore, by lowering the temperature and the draw ratio, the irregularity can be improved. Furthermore, the multiple stretching increases the fiber's stretching time, thereby increasing its orientation and, consequently, its breaking strength by approximately 0.2 cN / dtex. Furthermore, because the tow is free of oil and water, the evaporation of oil and water during the hot roller passage prevents the tow from absorbing heat from the roller, thereby reducing the roller's heating efficiency. This ensures a lower roller temperature while maintaining heating efficiency and reducing energy consumption. Finally, the tow is not oiled during stretching, eliminating the problem of oil volatilization during hot roller heating, which can lead to a relatively poor production environment.

[0080] Further improvement is that the melt pipe conveying temperature in S3 is 286-288°C, the spinning box temperature is 292-296°C, the cooling air pressure for cooling and molding is 34-36 Pa, and the cooling air humidity is 75-85%.

[0081] Because polyester melt takes a long time to pass through the pipeline, low temperatures are used for transport. However, if the temperature is too low, its fluidity will be poor. Therefore, after testing, 286-288°C was selected to reduce melt degradation during transport. Spinning temperature has a significant impact on yarn breakage and lint. Furthermore, because polyester fibers are shaped, high temperatures of 292-296°C can reduce irregular flow of the polyester melt, improve fiber spinnability, and reduce yarn breakage.

[0082] Specific examples and comparative examples are shown in Table 3, wherein the parameters of comparative example 1 are the same as those of embodiment 1, and the parameters of comparative examples 2 and 3 are the same as those of embodiment 2.

[0083] category Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 PTA share 70 70.5 71 70.8 70.4 No titanium dioxide coating Metal sand is used in the components No flange temperature Monoester acid value (mg / g) 58 60 62 59 61 Diester acid value (mg / g) 23 25 27 28 26 Melt intrinsic viscosity (dL / g) 0.620 0.624 0.625 0.630 0.628 Melt terminal carboxyl group (mol / t) 42 46 43 45 44 Titanium dioxide content (%) 2.0 2.4 3.0 3.5 4.0 Drying temperature (℃) 140 145 143 142 141 Drying time (h) 10 10.5 11 10.5 11 Moisture content in fully matte slices after drying (ppm) 40 30 32 35 34 Screw extruder zone 1 temperature (℃) 250 251 253 258 260 Screw extruder zone 2 temperature (℃) 260 265 270 268 263 Screw extruder zone three temperature (℃) 270 280 275 273 278 Temperature of screw extruder zone 4 (℃) 275 280 285 278 283 Screw extruder five-zone temperature (℃) 275 280 285 278 283 Flange temperature (℃) 275 280 285 278 283 Melt delivery temperature (℃) 286 286.5 287 287.5 288 Spinning box temperature (℃) 292 295 294 296 295 Cooling air pressure (pa) 34 35 36 35 36 Cooling air temperature (%) 75 76 78 80 85 Vertex angle of spinneret triangular section (°) 60 65 70 75 80 Length of the outer isosceles side of the triangular section of the spinneret (mm) 0.25 0.28 0.30 0.35 0.35 Length of isosceles side in triangular section of spinneret (mm) 0.15 0.20 0.25 0.25 0.15 The stretching ratio between the first hot roller and the second hot roller 1.05 1.10 1.15 1.20 1.30 The stretching ratio between the second and third hot rollers 1.05 1.20 1.30 1.40 1.50 The stretching ratio between the third and fourth hot rollers 1.30 1.8 2.0 2.5 3.0 Temperature of the first hot roller (°C) 50 52 55 57 60 Temperature of the second hot roller (°C) 55 58 60 63 65 Temperature of the third hot roller (℃) 55 58 60 63 65 Temperature of the fourth hot roller (°C) 125 128 135 140 130 Temperature of the fifth hot roller (°C) 125 128 135 140 130 Breaking strength of fiber used for wall covering embroidery thread (cN / dtex) 3.35 3.41 3.52 3.48 3.56 Elongation at break of special fiber for wall cloth embroidery thread (%) 29.5 30.1 28.7 30.4 29.6 Oil content of special fiber for wall covering embroidery thread (%) 1.30 1.28 1.32 1.30 1.29 Boiling water shrinkage of special fiber for wall covering embroidery thread (%) 7.4 7.5 7.4 7.5 7.3 After three months of high temperature exposure, breaking strength (cN / dtex) 3.31 3.35 3.40 3.34 3.39 2.89 Floating Silk (18 pieces / 24 hours) 3 2 0 1 2 2 15 8

[0084] From Table 3, we can see that the matte titanium dioxide in Comparative Example 1 did not use a titanium dioxide coating, resulting in the fiber breaking strength as low as 2.89 cN / dtex after three months of exposure. This is because the titanium dioxide coating can significantly improve the UV resistance, ensuring that the fiber breaking strength remains basically unchanged after exposure. In Comparative Example 2, metal sand is used in the component without a 40um mesh metal filter, resulting in poor impurity filtering effect of the component, especially when a high content of titanium dioxide is added, causing a significant increase in the number of floating threads. In Comparative Example 3, the flange connection at both ends of the screw extruder does not have an additional heating device. When the heated high-temperature melt passes through the unheated low-temperature flange, it will cause the viscosity temperature to drop, thereby affecting the subsequent wire-extrusion performance of the melt and causing an increase in floating threads.

[0085] A special fiber for wall cloth embroidery thread is prepared by the above method. The raw materials of the special fiber for wall cloth embroidery thread include purified terephthalic acid (PTA), ethylene glycol (EG) and full-matt chips containing a titanium dioxide coating layer. The special fiber for wall cloth embroidery thread has a breaking strength of ≥3.35 cN / dtex, an elongation at break of 28.0-31.0%, an oil content of 1.25-1.35%, a boiling water shrinkage of 7.3-7.5%, and the number of floating threads in 18 positions within 24 hours is less than or equal to 5.

[0086] The invention can solve the problem of incomplete performance of existing polyester filament embroidery thread when used as wall cloth embroidery thread, so that the woven fabric has brighter colors and better three-dimensional effect after dyeing, and has higher breaking strength and sunlight resistance.

Claims

1. A method for producing special fiber for wall cloth embroidery thread, characterized by: The production method comprises S1. Purified terephthalic acid (PTA) and ethylene glycol (EG) are subjected to a first esterification, a second esterification, a preliminary polycondensation, and a final polycondensation to form a polyester melt having an intrinsic viscosity of 0.620-0.630 dL / g and a terminal carboxyl group content of 42-46 mol / t. The slurry molar ratio of ethylene glycol (EG) to purified terephthalic acid (PTA) is approximately 1.139, i.e., EG is in excess, which accelerates the esterification reaction rate and promotes the etherification of ethylene glycol (EG) to produce diethylene glycol. S2, placing a certain proportion of fully matte chips into a drying tower for drying, then injecting them into a screw extruder for injection extrusion, and outputting them outward through a filtration system to form a matte melt, wherein the fully matte chips are composed of a polyester melt and a titanium dioxide coating layer; S3, injecting the polyester melt in S1 into the dynamic mixer through the melt pipe, and injecting the matte melt in S2 into the melt pipe through the screw extruder to perform preliminary mixing with the polyester melt, and then entering the dynamic mixer for thorough mixing and stirring; S4, the mixed melt is sequentially conveyed into a static mixer → a metering pump → a spinneret extrusion → cooling and forming → a first godet roller → a first hot roller → a second hot roller → a third hot roller → a fourth hot roller → a fifth hot roller → a network device → a second godet roller → winding and forming, to form a special fiber for special-shaped wall cloth embroidery thread; The cooled and formed filament bundle is stretched using a three-step oil-free drawing, low-ratio, and low-temperature stretching method: the three-step oil-free drawing, low-ratio, and low-temperature stretching method comprises five hot rollers, wherein the stretching ratio between the first and second hot rollers is 1.05-1.3, the stretching ratio between the second and third hot rollers is 1.05-1.5, the stretching ratio between the third and fourth hot rollers is 1.3-3.0, and there is no stretching between the fourth and fifth hot rollers; the temperature of the first hot roller is 50-60° C., the temperature of the second and third hot rollers is 55-65° C., and the fourth and fifth hot rollers are sizing rollers with a temperature of 125-140° C.; The inside of the spinneret is filtered by spinning through two layers of 40um mesh metal filter mesh; the filtration system includes a filter, and the filter element of the filter has a filtration accuracy of 100μ; The screw inlet of the screw extruder is provided with a nitrogen protection device, which reduces the pressure of the high-pressure nitrogen and ensures the stability of the fully matt slices; the two ends of the screw extruder are connected by flanges, and the flanges are provided with a heating mechanism, and the temperature of the flanges is formed to 275-285°C by the heating mechanism.

2. The method for producing special fiber for wall cloth embroidery thread according to claim 1, characterized in that: The proportion of purified terephthalic acid (PTA) in step S1 is 70-71%, the acid value of the melt obtained by the first esterification is 58-62 mg / g, and the acid value of the melt obtained by the second esterification is 23-28 mg / g.

3. The method for producing special fiber for wall cloth embroidery thread according to claim 2, characterized in that: The proportion of titanium dioxide in the fully matte slice is 49-51%.

4. The method for producing special fiber for wall cloth embroidery thread according to claim 1, characterized in that: The titanium dioxide coating layer is coated titanium dioxide obtained by SiO2 coating treatment, and the content of the coated titanium dioxide in the special fiber for special-shaped wall cloth embroidery thread is 2-4%.

5. The method for producing special fiber for wall cloth embroidery thread according to claim 1, characterized in that: The drying temperature in the drying tower is 140-145° C., the drying time is 10-11 hours, and the moisture content of the fully matte slices after drying is controlled between 30-40 ppm.

6. The method for producing special fiber for wall cloth embroidery thread according to claim 1, characterized in that: Five temperature zones are formed inside the screw extruder, wherein the temperature of zone 1 is 250-260°C, the temperature of zone 2 is 260-270°C, the temperature of zone 3 is 270-280°C, the temperature of zone 4 is 275-285°C, and the temperature of zone 5 is 275-285°C.

7. The method for producing special fiber for wall cloth embroidery thread according to any one of claims 1 to 6, characterized in that: The spinneret on the spinneret in the spinneret assembly has a triangular cross-section, and the triangle is an isosceles triangle symmetrically arranged inside and outside, with a vertex angle of 60-80°. The isosceles side length of the outer isosceles triangle of the spinneret is 0.25-0.35 mm, and the isosceles side length of the inner isosceles triangle is 0.15-0.25 mm. The base of the isosceles triangle cross-section of the spinneret is parallel to the ring blowing tube.

8. The method for producing special fiber for wall cloth embroidery thread according to claim 1, characterized in that: The melt pipe conveying temperature in S3 is 286-288°C, the spinning box temperature is 292-296°C, the cooling air pressure for cooling and molding is 34-36 Pa, and the cooling air temperature is 75-85°C.

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