Tire-grade high-tenacity and modulus recycled nylon 6.6 yarn and its manufacturing method.

Abstract

In this invention, tire grade oiled and unoiled nylon 6.6 drawn and undrawn yarns are converted into recycled nylon 6.6 pellets. The recycled nylon 6.6 pellets and virgin nylon 6.6 pellets are then used in different ratios to produce tire grade regenerated nylon 6.6 yarn.

Description

Technical Field

[0001] The present invention relates to the production of recycled nylon 6.6 pellets from tire-grade nylon 6.6 yarn (or thread; yarn) scrap (or waste, or offcuts, or pieces, or waste; scrap). Such recycled nylon 6.6 pellets are used in the production of tire-grade nylon 6.6 yarn at a different ratio from virgin nylon 6.6 pellets. The purpose of this research is to obtain recycled nylon 6.6 tire-grade yarn with physical, thermal, mechanical properties and manufacturing processes comparable to virgin nylon 6.6. Also, this research contributes to the global sustainability issue, which will be explained in depth below.

Background Art

[0002] Nylon is a polymer composed of repeating units of diamine and dicarboxylic acid with different numbers of carbon atoms. The polymerization reaction is carried out in a batch or continuous process with pressure, vacuum, and heat. Nylon 6.6 thermoplastic polymer is made from petrochemical monomers and is bonded to form long chains by a condensation polymerization reaction.

[0003] Petroleum-based polymers have been used for a long time because of their convenience, durability, flexibility, and low reactivity to water and other chemicals. In recent years, with the increasing problems of the global environment and sustainability, humans have begun to recognize that the supply source of petrochemical products is limited. This threatens the balance between the natural environment and scientific development. Therefore, how to balance environmental and human development has become an issue in recent research.

[0004] Nylon is not biodegradable and remains in the environment indefinitely. The two main causes of microplastic pollution in the ocean are nylon fishing nets and synthetic textile fibers. In other words, nylon has a significant impact on the aquatic environment. On the other hand, the property of nylon being difficult to decompose means that it can be recycled indefinitely, and if all existing nylon materials are recycled, the demand for nylon can be met even if new nylon production is stopped. Therefore, it is necessary to make nylon recycling schemes more accessible to general consumers. [Overview of the project]

[0005] This invention consists of the following two main processes and products. i. Production of recycled (or regenerated, or recirculated) nylon 6.6 pellets from tire-grade oiled (or oiled) and non-oiled (or non-oiled, non-oiled, or non-oiled) nylon 6.6 drawn yarn and undrawn yarn scrap generated in standard tire-grade yarn manufacturing processes. ii. Manufacturing tire-grade yarn with equivalent processes and product characteristics by mixing virgin (or unprocessed) nylon 6.6 pellets and recycled nylon 6.6 pellets at different recycled pellet ratios.

[0006] A pellet mixture consisting of a certain proportion of virgin nylon 6.6 pellets and recycled nylon 6.6 pellets undergoes a solid polymerization process at a controlled temperature to obtain a relative viscosity level desirable for the spinning process. The virgin to recycled pellet ratio is produced in the range of 10:90 to 90:10, preferably 80:20 to 50:50, to obtain equivalent yield, process performance, productivity, production and product sustainability, and yarn properties. The moisture level of either flake type is a maximum of 0.5%.

[0007] Furthermore, the finishing oil level of chopped nylon 6.6 yarn scrap is 0.7–1.0%. There is no washing unit for oil removal of the scrap before the production of recycled nylon 6.6 pellets. In the recycled nylon 6.6 pellet production process detailed in Figure 2, the finishing oil is removed from the scrap polymer in the vacuum zone of the extruder. The finishing oil level of recycled nylon 6.6 pellets at the end of production is 0.01–0.05%. [Brief explanation of the drawing]

[0008] This disclosure can be better understood by reading the detailed description of the drawings below.

[0009] [Figure 1] Figure 1: The manufacturing process for a standard yarn bobbin (1.8) (tire-grade nylon 6.6 yarn bobbin) consists of supplying virgin nylon 6,6 pellets (virgin nylon 6,6 pellet flakes) (1.1) to a silo, first purging (or purifying) the nylon 6,6 pellets (1.2), then undergoing a solid (or solid-phase, or solid-state) polymerization process (1.3), converting the polymerized nylon 6,6 pellets into molten nylon 6.6 polymer (1.4), passing the molten nylon 6.6 polymer through a die to obtain a round filament shape (1.5), cooling the nylon 6.6 polymer filament (1.6), the nylon 6.6 filament undergoing several process steps to obtain the desired final properties (1.7), and finally manufacturing a tire-grade nylon 6.6 yarn bobbin (1.8).

[0010] [Figure 2]Figure 2: The recycling method for nylon 6,6 pellets consists of the following steps: (2.1) collecting oiled and unoiled nylon 6,6 drawn yarn scrap and undrawn yarn scrap during yarn manufacturing; (2.2) cutting the nylon 6,6 yarn scrap into short strands; (2.3) transporting the cut nylon 6,6 yarn scrap to a compression device; and (2.4) supplying the compressed nylon 6,6 yarn scrap to an extruder. The process includes: melting (2.5); suctioning oil from the molten polymer (2.6); forming strands of nylon 6.6 (2.7); cooling the strands of nylon 6.6 in a water bath (2.8); drying the strands of nylon 6.6 after removing them from the water bath (2.9); pelletizing the strands of nylon 6.6 (2.10); recovering the recycled nylon 6.6 pellets (2.11); and packaging the recycled nylon 6.6 pellets (2.12).

[0011] [Figure 3] Figure 3: This figure is very similar to Figure 1. The only difference is that at the beginning of the process, virgin flakes (3.1) and recycled flakes (3.2) are homogeneously mixed in a mixing system in a fixed ratio.

[0012] Tire-grade yarn: Nylon 6.6 yarn having a tenacity (or tensile strength, or toughness) of at least 8.0 gpd (grams per denier) and a density level of 100 to 5000 dtex. 4% SASE: Stress (gpd) at 4% elongation Tenacity: Yarn strength (grams) / Yarn density (denier) (gpd) Virgin nylon 6,6 pellets: Unprocessed nylon 6,6 pellets Recycled nylon 6,6 pellets: Nylon 6,6 pellets formed from scrap materials. Tire-grade nylon 6.6 yarn: Nylon 6.6 yarn used for tire cords. Oiled and unoiled nylon 6,6 drawn yarn scrap and undrawn yarn scrap: processed yarn scrap and unprocessed yarn scrap Nylon 6.6 strands: Molten polymer after extrusion (spaghetti-like) [Modes for carrying out the invention]

[0013] The present invention relates to a tire-grade nylon 6,6 mono and / or multifilament yarn comprising at least 10% recycled nylon 6,6, preferably 20% recycled nylon 6,6, wherein the nylon 6,6 mono or multifilament yarn has a tenacity of at least 8.0 gpd according to ASTM-D885.

[0014] ASTM-D885 is a standard test method for tire cords, tire cord fabrics, and industrial filament yarns made from synthetic organic-based fibers. Tire-grade nylon 6,6 monofilament and / or multifilament yarns have at least 1.25 gpd 4% SASE in accordance with ASTM-D885.

[0015] A method for manufacturing tire-grade nylon 6,6 monofilament and / or multifilament yarn includes the following steps: Process a) Manufacturing of recycled nylon 6,6 pellets, - Cut tire-grade oil-coated and / or un-oil-coated drawn and / or undrawn nylon 6.6 fiber scraps, including monofilament and / or multifilament yarns, into 3cm to 5cm pieces to obtain nylon 6.6 chopped fiber. - The material is fed into an extruder having six zones with a minimum temperature of 250°C and a maximum temperature of 290°C to obtain a polymer of molten nylon 6.6 from scrap yarn. - Cooling the strand, -Formed into pellet form and cut into pieces with a size of 300-500 pellets per 10 grams, where the recycled nylon 6.6 pellets contain up to 0.05% finishing oil. Process b) Manufacturing of virgin nylon 6,6 pellets, Process c) Virgin nylon 6,6 pellets and recycled nylon 6,6 pellets are mixed with a minimum recycling rate of 20% to produce tire-grade recycled nylon 6,6 yarn.

[0016] At the beginning of this process, stretched and / or unstretched nylon 6.6 fiber scrap, including filament yarn, is cut into pieces ranging from 3 cm to 5 cm in length, coated with tire-grade oil and / or un-oiled. This process yields chopped nylon 6.6 fibers. The chopped fibers are fed into an extruder to obtain a molten polymer from the scrap yarn. The molten polymer is formed into molten fibers of a certain diameter and cooled in a water bath. After the fiber polymer has cooled, it is cut into pieces of a certain size, a process referred to in the literature as a strand pelletizing system.

[0017] During the production of tire-grade recycled pellets, vacuuming is used to remove finishing oil from the polymer matrix generated during the scrap oil yarn manufacturing process. This is a critical process for production because high levels of finishing oil reduce production yield and increase the breakage level during spinning. The main objective is to minimize the level of finishing oil in the recycled pellets.

[0018] Since tire-grade recycled pellets and virgin pellets are mixed during manufacturing, homogeneous mixing is another important parameter in the preparation stage for solid polymerization. To prevent separation within the silo, the pellet sizes of the two pellet grades need to be as close as possible. Therefore, the particle size of tire-grade recycled pellets has been improved for the production of tire-grade recycled yarn.

[0019] The amount of recycled tire-grade material included in the yarn varies depending on customer expectations and minimum specification requirements. However, according to the Global Recycling Certification system, the minimum requirement for recycled material in the final product is 20%. Therefore, in accordance with this regulation, we conducted research focusing on 20% recycled material in tire-grade yarn. Recycled pellets and virgin pellets were mixed and fed into a silo for adjustment. The degree of solid polymerization was adjusted according to the new mixed material so that the same RV level was achieved at the conditioner outlet.

Claims

1. A tire-grade nylon 6,6 mono and / or multifilament yarn comprising a mixture of virgin nylon 6,6 pellets and recycled nylon 6,6 pellets, The recycled nylon 6,6 pellets are present in an amount of at least 10% by weight relative to the total weight of the nylon 6,6. The recycled nylon 6,6 pellets have a finishing oil content of 0.01% by weight or more and 0.05% by weight or less relative to the total weight of the recycled nylon 6,6, as measured according to ASTM D2257-20. The nylon 6,6 mono and / or multifilament yarn is a tire-grade nylon 6,6 mono and / or multifilament yarn having a tenacity of at least 8.0 gpd (grams per denier) and a density level of 100 to 5000 dtex according to ASTM-D885.

2. The tire-grade filament yarn according to Claim 1, comprising 20% ​​by weight of recycled nylon 6,6 relative to the total weight of nylon 6,6 pellets.

3. A tire-grade filament yarn according to claim 1, having at least 1.25 gpd of 4% SASE (stress at specified elongation) in accordance with ASTM-D885.

4. A method for producing tire-grade filament yarn according to claim 1, comprising the following steps. Process a) Recycled nylon 6,6 pellets, - Cut tire-grade oil-coated and / or un-oil-coated stretched and / or unstretched nylon 6,6 fiber scraps, including monofilament and / or multifilament yarns, into 3-5 cm pieces to obtain nylon 6,6 chopped fibers. - The material is supplied to an extruder having six zones with a minimum temperature of 250°C and a maximum temperature of 290°C to obtain a polymer of molten nylon 6,6 from scrap yarn. - Cool the strands, - Formed into pellet form and cut to a size of 300-500 pellets per 10 grams, where, relative to the total pellet mixture, as measured according to ASTM D2257-20, the recycled nylon 6,6 pellets contain a maximum of 0.05% by weight of finishing oil. To prepare by, Step b) Prepare pellets of virgin nylon 6,6. Mixing virgin nylon 6,6 pellets with recycled nylon 6,6 pellets.

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