Preparation method of heat-stable regenerated high-modulus low-shrinkage polyester industrial yarn

Abstract

The invention provides a preparation method of a regenerated high-modulus low-shrinkage polyester industrial yarn with good thermal stability, and belongs to the technical field of production of special products from recycled plastics. According to the method, chemical method regenerated polyester chips and / or bottle chip regenerated polyester chips are used as raw materials, the method comprises three steps of tackifying, melt extrusion and spinning which are sequentially carried out, the tackifying is carried out in a vacuum rotary drum and comprises three stages of heat preservation pre-crystallization at 100-120 DEG C for 160-240 minutes, heat preservation crystallization at 170-200 DEG C for 120-190 minutes and solid phase polymerization at 210-230 DEG C, the temperatures of all areas of a screw rod for melt extrusion are 290-300 DEG C, 300-310 DEG C, 295-305 DEG C, 275-285 DEG C, 275-285 DEG C and 275-285 DEG C in sequence, and the melt extrusion is carried out in a vacuum rotary drum. The breaking strength of the obtained finished product is greater than or equal to 6.5 cN / dtex, the dry heat shrinkage rate is less than or equal to 4.0%, and the thermal strength loss after tension-free heating at 170 DEG C for 4 h is less than or equal to 2.0%. The finished product not only has excellent physical and mechanical properties and excellent thermal stability, but also realizes high-quality utilization of the regenerated polyester, and meets the requirement of environmental protection.

Description

Technical Field

[0001] This application relates to a method for preparing heat-stable recycled high-modulus, low-shrinkage polyester industrial yarn, belonging to the technical field of producing special products from recycled plastics. Background Technology

[0002] Polyester industrial yarn, with its high strength, abrasion resistance, and chemical stability, has wide applications in various industrial fields. However, with the continuous advancement of industrial technology and the increasing awareness of environmental protection, the requirements for the performance and sustainability of polyester industrial yarn are also becoming increasingly stringent. High-modulus, low-shrinkage polyester industrial yarn possesses excellent properties such as high breaking strength, good impact resistance, high elastic modulus, and low elongation. Due to its high initial modulus and low heat shrinkage rate, its mechanical properties are excellent, and it is widely used in rubber skeleton substrates, such as automotive radial tires, tire cord fabrics, high-grade geogrids, and V-belt hard cords. With the continued increase in the radialization rate of domestic tires and the number of cars on the road, there is still significant room for growth in the future demand for polyester tire cord fabric production capacity in my country. At the same time, the global call for sustainable development is growing stronger, and waste treatment and resource recycling in the textile industry have become important issues. The research and development of recycled polyester industrial yarn can not only solve waste treatment problems but also effectively save resources, reduce production costs, and have a positive impact on the environment.

[0003] The development of recycled high-modulus, low-shrinkage polyester industrial yarn emerged against this backdrop. This new type of industrial yarn combines the advantages of recycled materials and high-performance polyester, achieving high strength and low shrinkage through a specific preparation process. Its high modulus ensures the material's rigidity and durability, while the low shrinkage rate ensures dimensional stability and long-term performance during use. However, the preparation of recycled high-modulus, low-shrinkage polyester industrial yarn is not easy. In this field, some companies modify equipment, such as providing melt extrusion devices for recycled polyester high-modulus, low-shrinkage fibers. They control the flow rate by setting up a telescopic cavity and use positioning components to drive a scraper to clean the melt extrusion process. More companies control the process itself, such as by increasing the fineness of the powder, crystallizing to increase viscosity, solid-phase polycondensation, and adding modifiers such as modified antistatic agents and chain extenders to achieve increased intrinsic viscosity and high draw ratio. However, in the above-mentioned production process, the original properties of polyester are mostly maintained by adding some original chips, and it is rare to use pure recycled polyester to achieve the original properties of polyester. In particular, the utilization of recycled polyester is not ideal in terms of shrinkage rate and thermal stability. Summary of the Invention

[0004] In view of this, this application provides a method for preparing heat-stable recycled high-modulus, low-shrinkage polyester industrial yarn, which not only endows the finished yarn with excellent physical and mechanical properties, but also gives it low shrinkage and heat loss, and good thermal stability.

[0005] Specifically, this application is implemented through the following scheme: A method for preparing heat-stable recycled high-modulus, low-shrinkage polyester industrial yarn involves processing chemically recycled polyester chips and / or bottle-flake recycled polyester chips, followed by thickening, melt extrusion, and spinning to obtain recycled high-modulus, low-shrinkage polyester industrial yarn. The thickening process is carried out in a vacuum drum and includes three stages: pre-crystallization, crystallization, and solid-state polymerization. Pre-crystallization stage: The temperature is raised from room temperature to 100~120℃ for 120~180 min, and then held at 100~120℃ for 160~240 min for pre-crystallization. Crystallization stage: The temperature is raised from the pre-crystallization temperature to 170~200℃ for 240~330 min, and then crystallized at 170~200℃ for 120~190 min. Solid-state polymerization stage: The temperature is raised from the crystallization temperature to 210~230℃ for 150~180 min. After solid-state polymerization is completed, the temperature is lowered for 3~5 h. The temperatures of the screw zones in the melt extrusion process are sequentially 290~300℃, 300~310℃, 295~305℃, 275~285℃, 275~285℃, 275~285℃, HTM: 290~300℃. The recycled high-modulus, low-shrinkage polyester industrial yarn obtained by spinning has the following properties: breaking strength ≥6.5cN / dtex, dry heat shrinkage ≤4.0%, and heat loss ≤2.0% after being heated at 170℃ without tension for 4 hours.

[0006] Furthermore, as a preferred option: The moisture content of the slices at the end of the pre-crystallization stage is ≤300ppm.

[0007] The viscosity of the chips after solid-phase polymerization was 1.11 ± 0.01 dl / g, and the viscosity of the chips after cooling was 1.14 ± 0.01 dl / g.

[0008] The temperature was lowered to below 150°C.

[0009] The drawing ratio of the spinning process is 1.5 to 2.5, and the winding speed is 5000 to 5500 m / min.

[0010] When chemically recycled polyester chips are used as the treatment object, the cooling time is 4-5 hours, and the heat loss of the recycled high-modulus, low-shrinkage polyester industrial yarn obtained by spinning is ≤1.6%.

[0011] When recycled polyester chips from bottle flakes are used as the processing target, the cooling time is 3-4 hours, and the heat loss of the recycled high-modulus, low-shrinkage polyester industrial yarn obtained by spinning is ≤1.2%.

[0012] The above preparation method uses chemically recycled polyester chips and bottle-grade recycled polyester chips as the processing objects. Under vacuum conditions, four stages are sequentially performed to complete solid-state thickening: pre-crystallization, crystallization, solid-state polymerization, and cooling. During the thickening process, the temperature is first raised from room temperature to 100-120℃ for pre-crystallization, then raised to 170-200℃ for crystallization, and finally raised to 210-230℃ for solid-state polymerization. When the viscosity reaches 1.11±0.01 dl / g, cooling begins, and the cooling time is controlled at approximately 3-5 hours. After cooling, the chip viscosity is 1.14±0.01 dl / g. The thickened recycled polyester chips are then used to prepare recycled high-modulus, low-shrinkage polyester industrial yarn using melt spinning technology. This application's technical solution not only achieves good spinnability of recycled polyester chips but also endows high-modulus, low-shrinkage polyester industrial yarn with characteristics such as environmental friendliness, excellent strength, and good thermal stability. Detailed Implementation

[0013] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions of this application will be further described in detail below with reference to specific examples in the embodiments of this application. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] Example 1

[0015] In this embodiment, chemically recycled polyester chips are used as raw materials. After solid-phase thickening is performed using a vacuum drum machine, recycled high-modulus, low-shrinkage polyester industrial yarn is prepared by melt extrusion and spinning.

[0016] The viscosity of chemically recycled polyester chips is 0.674±0.02 dl / g, and the terminal carboxyl group concentration is 32±1 mol / t.

[0017] The thickening process includes a pre-crystallization stage, a crystallization stage, a solid-state polymerization stage, and a cooling stage.

[0018] (1) Pre-crystallization stage: The temperature inside the vacuum drum is raised from room temperature to 100℃ and maintained for 180 min; then it is kept at 100℃ and pre-crystallized for 180 min. (2) Crystallization stage: The temperature inside the vacuum drum is raised from the pre-crystallization temperature to 180 ℃, and the heating process is maintained for 300 min; the temperature is then maintained at 180 ℃ and crystallized for 180 min; (3) Solid-state polymerization stage: The temperature inside the vacuum drum is raised from the crystallization temperature to 225 ℃, and the heating process is maintained for 180 min; solid-state polymerization is completed by holding at 225 ℃ for 840 min. (4) Cooling: When the viscosity reaches 1.1±0.01 dl / g, start cooling. The cooling time is controlled at about 5 h. After cooling, the viscosity of the slice is 1.146 dl / g.

[0019] (5) Melt extrusion: After the chemically recycled polyester chips are thickened, they are fed into the screw for extrusion. The temperatures of each zone of the screw are as follows: 298℃, 308℃, 300℃, 280℃, 280℃, 280℃.

[0020] (6) Spinning: The parameter settings are shown in Table 1.

[0021] Table 1: Process parameters of each drawing roller in the spinning process .

[0022] The above process yields chemically recycled high-modulus, low-shrinkage polyester industrial yarn, the properties of which are shown in Table 2.

[0023] Table 2: Main performance indicators of the recycled high-modulus, low-shrinkage polyester industrial yarn prepared in Example 1 .

[0024] The product in this embodiment meets the processing requirements of recycled high-modulus, low-shrinkage polyester industrial yarn.

[0025] Example 2 This embodiment uses recycled polyester chips from bottle flakes as the processing object. After solid-phase thickening using a vacuum drum machine, recycled high-modulus, low-shrinkage polyester industrial yarn is prepared by melt extrusion and spinning.

[0026] The viscosity of the recycled polyester chips for bottle flakes is 0.757±0.02 dl / g, and the terminal carboxyl group is 34±1 mol / t.

[0027] The thickening process includes a pre-crystallization stage, a crystallization stage, a solid-state polymerization stage, and a cooling stage.

[0028] (1) Pre-crystallization stage: The temperature inside the vacuum drum is raised from room temperature to 120℃ and maintained for 120 min; then it is kept at 120℃ and pre-crystallized for 240 min. (2) Crystallization stage: The temperature inside the vacuum drum is raised from the pre-crystallization temperature to 180 ℃, and the heating process is maintained for 240 min; the temperature is then maintained at 180 ℃ for 120 min for crystallization. (3) Solid-state polymerization stage: The temperature inside the vacuum drum is raised from the crystallization temperature to 210 ℃, and the heating process is maintained for 180 min; the solid-state polymerization is completed by holding at 210 ℃ for 1080 min. (4) Cooling: When the viscosity reaches 1.11±0.01 dl / g, start cooling. The cooling time is controlled at about 3 hours. After cooling, the viscosity of the slice is 1.137 dl / g.

[0029] (5) Melt extrusion: After the chemically recycled polyester chips are thickened, they are fed into the screw for extrusion. The temperatures of each zone of the screw are as follows: 298℃, 308℃, 300℃, 280℃, 280℃, 280℃.

[0030] (6) Spinning: The parameter settings are shown in Table 3.

[0031] Table 3: Process parameters of each drawing roller in the spinning process .

[0032] The above process yields recycled high-modulus, low-shrinkage polyester industrial yarn, the properties of which are shown in Table 4.

[0033] Table 4: Main performance indicators of the recycled high-modulus, low-shrinkage polyester industrial yarn prepared in Example 2 .

[0034] The product in this embodiment meets the processing requirements of recycled high-modulus, low-shrinkage polyester industrial yarn.

[0035] The recycled high-modulus, low-shrinkage polyester industrial yarns obtained in Examples 1 and 2 were placed in an oven (without tension). After the temperature reached 170°C, the tensile properties before and after the test were tested for 4 hours. The results are shown in Table 5.

[0036] Table 5: Comparison of Heat Loss of Regenerated High-Modulus Low-Shrinkage Polyester Industrial Yarn Prepared by Different Methods .

[0037] As can be seen from Table 5, the heat loss of the chemically recycled high-modulus low-shrinkage polyester industrial yarn obtained in Example 1 is 1.60%, and the heat loss of the recycled high-modulus low-shrinkage polyester industrial yarn obtained in Example 2 is 1.16%. Both recycled high-modulus low-shrinkage yarns have relatively low heat loss and good thermal stability.

[0038] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A process for the preparation of heat stable regenerated high modulus low shrinkage polyester industrial yarn, characterized by: The chemical method is used to regenerate polyester chip and / or bottle piece polyester chip as raw material, including three steps of tackifying, melt extruding and spinning in sequence, The tackifying is carried out in a vacuum drum, including three stages of pre-crystallization, crystallization and solid phase polymerization, The pre-crystallization stage: the temperature is increased from room temperature to 100-120℃, the temperature increasing time is 120-180min, and the pre-crystallization is carried out at 100-120℃ for 160-240min; The crystallization stage: the temperature is increased from the pre-crystallization temperature to 170-200℃, the temperature increasing time is 240-330min, and the crystallization is carried out at 170-200℃ for 120-190min; The solid phase polymerization stage: the temperature is increased from the temperature of the crystallization stage to 210-230℃, the temperature increasing time is 150-180min, and the solid phase polymerization is carried out at 210-230℃, then the temperature is decreased, and the temperature decreasing time is 3-5h; The screw temperature of the melt extruding is 290-300℃, 300-310℃, 295-305℃, 275-285℃, 275-285℃, 275-285℃ and HTM: 290-300℃ in sequence, The regenerated high modulus low shrinkage polyester industrial yarn obtained by spinning has a breaking strength of ≥6.5cN / dtex, a dry heat shrinkage rate of ≤4.0%, and a heat resistance loss of ≤2.0% at 170℃ without tension for 4h.

2. The process for the preparation of heat stable regenerated high modulus low shrinkage polyester industrial yarn as claimed in claim 1 wherein: The draw ratio of the spinning process is 1.5-2.5, and the winding speed is 5000-5500m / min.

3. The process for the preparation of heat stable regenerated high modulus low shrinkage polyester industrial yarn as claimed in claim 1 wherein: The viscosity of the chip after the solid phase polymerization is 1.11±0.01dl / g, and the viscosity of the chip after the temperature decreasing is 1.14±0.01dl / g.

4. The process for preparing heat-stable regenerated high-modulus low-shrinkage polyester industrial yarn according to claim 1, characterized in that: The temperature is decreased to below 150℃.

5. The method for preparing a heat-stable recycled high-modulus, low-shrinkage polyester industrial yarn according to claim 1, characterized in that: The water content of the chip at the end of the pre-crystallization stage is ≤300ppm.

6. The method for preparing a heat-stable recycled high-modulus, low-shrinkage polyester industrial yarn according to claim 1, characterized in that: The screw temperature is 298℃, 308℃, 300℃, 280℃, 280℃ and 280℃ in sequence.

7. The preparation method of the heat-stable regenerated high-modulus low-shrinkage polyester industrial yarn according to any one of claims 1-6, characterized in that: The heat resistance loss of the chemical method regenerated high modulus low shrinkage polyester industrial yarn obtained by spinning is ≤1.6% when the chemical method regenerated polyester chip is used as the processing object and the temperature decreasing time is 4-5h.

8. The preparation method of the heat-stable regenerated high-modulus low-shrinkage polyester industrial yarn according to any one of claims 1-6, characterized in that: The heat resistance loss of the bottle piece regenerated high modulus low shrinkage polyester industrial yarn obtained by spinning is ≤1.2% when the bottle piece polyester chip is used as the processing object and the temperature decreasing time is 3-4h.