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CN-121992653-A - Application of monofunctional isocyanate in surface end-capping modification of PA66 industrial yarn

CN121992653ACN 121992653 ACN121992653 ACN 121992653ACN-121992653-A

Abstract

The invention discloses an application of monofunctional isocyanate in the surface end-capping modification of PA66 industrial yarns, and belongs to the technical field of polyamide fibers. Aiming at the problems of high hydrolysis sensitivity and poor long-term stability of PA66 in a humid environment, the invention adopts monofunctional isocyanate to react with the terminal amino group of the outermost layer of PA66 fiber to form an alkyl/aryl urea end-capped structure, the formed urea bond is more hydrolysis-resistant than an amide bond, and the monofunctional design ensures that a bodily form crosslinked network is not formed, the modification reaction is limited to occur only on a surface layer, the performance loss caused by internal modification can be avoided, and the obtained surface end-capped modified PA66 industrial yarn has high strength retention rate in a high-humidity and heat environment and meets the industrial application requirement of long-term durability, so the invention has good application prospect in preparing radial tire cord fabrics, automobile safety belts, industrial conveyor belts or high-pressure rubber hose reinforcing layers.

Inventors

  • YI KAIHUA
  • YANG ZHOU
  • ZHOU YU
  • MA ZUQIANG
  • WU YINLONG

Assignees

  • 烟台华润锦纶有限公司

Dates

Publication Date
20260508
Application Date
20260212

Claims (10)

  1. 1. The application of monofunctional isocyanate in the surface end-capping modification of PA66 industrial yarn.
  2. 2. A surface blocking modification liquid for PA66 industrial yarns is characterized by comprising isocyanate, wherein the isocyanate is monofunctional isocyanate.
  3. 3. The surface-blocked modifying liquid according to claim 2, wherein the monofunctional isocyanate content in the surface-blocked modifying liquid is 0.3 to 4wt%; And/or the monofunctional isocyanate comprises at least one of cyclohexyl isocyanate, phenyl isocyanate, n-butyl isocyanate, isopropyl isocyanate, methyl isocyanate, ethyl isocyanate or octadecyl isocyanate.
  4. 4. The surface-capping modifying liquid of claim 2, further comprising a solvent, wherein the solvent satisfies at least one of the following characteristics: 1) The normal pressure boiling point of the solvent is 120-230 ℃; 2) The saturated vapor pressure of the solvent at 145 ℃ is less than or equal to 10kPa; 3) The retention rate of-NCO groups of the solvent and the monofunctional isocyanate after being mixed for 48 hours under the sealing condition of 140 ℃ is more than or equal to 98.5%; 4) The solubility of the solvent to the monofunctional isocyanate at 25 ℃ is more than or equal to 80g/100g; And/or the solvent comprises at least one of butyl acetate, amyl acetate, cyclohexanone, mesitylene, aromatic hydrocarbon solvent oil S-150, dibasic acid ester mixture, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone or dimethylacetamide; And/or the surface end-capping modifying liquid further comprises a catalyst, wherein the catalyst comprises an organotin catalyst, an amine catalyst or a combination thereof, and the catalyst content in the surface end-capping modifying liquid is 0.005-0.08wt%; and/or the linear density of the PA66 industrial yarn is 800-3000 dtex; And/or the amino end content of the PA66 industrial yarn is 40-50 mmol/kg.
  5. 5. A surface end-capping modification method for PA66 industrial yarn, characterized in that the surface end-capping modification solution according to any one of claims 2 to 4 is used for surface end-capping modification of PA66 industrial yarn.
  6. 6. The surface end-capping modification process of claim 5, comprising immersing the PA66 industrial yarn in the surface end-capping modification solution to obtain an immersed yarn, and sequentially pre-reacting and heat-setting the immersed yarn to obtain the surface end-capping modified PA66 industrial yarn.
  7. 7. The surface termination modification method according to claim 6, wherein the dipping temperature is 100 to 135 ℃; and/or the soaking time is 8-50 s; and/or the liquid carrying rate of the impregnated yarn is 8-25wt%; And/or the temperature of the pre-reaction is 120-160 ℃; and/or the pre-reaction time is 15-90 s; And/or the temperature of the heat setting is 160-200 ℃; and/or the heat setting time is 30-120 s.
  8. 8. The surface end-capping modified PA66 industrial yarn is characterized in that the surface end-capping modified PA66 industrial yarn comprises PA66 industrial yarn and a surface end-capping modified layer, the surface end-capping modified layer is coated on at least part of the surface of the PA66 industrial yarn, and the surface end-capping modified layer is formed by the surface end-capping modified liquid according to any one of claims 2-4 or is prepared by the surface end-capping modified method according to any one of claims 5-7.
  9. 9. The surface-terminated, modified PA66 industrial yarn of claim 8, wherein the surface-terminated, modified layer has a thickness of 5 μm or less; and/or the amino end content of the surface end-capped modified PA66 industrial yarn is less than or equal to 23mmol/k; And/or, the 14-day strength retention rate of the surface end-capped modified PA66 industrial yarn under the condition of 85 ℃ and 95% RH is more than or equal to 91%.
  10. 10. Use of the surface-terminated modified PA66 industrial yarn of claim 8 or 9 for the preparation of radial tire cord, automotive safety belts, industrial conveyor belts or high pressure rubber hose reinforcement.

Description

Application of monofunctional isocyanate in surface end-capping modification of PA66 industrial yarn Technical Field The invention belongs to the technical field of polyamide fibers, and particularly relates to application of monofunctional isocyanate in surface end-capping modification of PA66 industrial yarns. Background The industrial silk of polyhexamethylene adipamide (PA 66) has high content of terminal amino group (generally 40-50 mmol/kg), and is easy to hydrolyze under high-temperature and high-humidity environment, so that the strength is fast attenuated. The hydrolysis mechanism is mainly due to the reversibility of the polycondensation reaction of PA66, i.e. the reversible hydrolysis of the amide bond into carboxylic acid and amine end groups in the presence of moisture, further leading to polymer chain scission, molecular weight reduction and mechanical property decay. Specifically, a water molecule undergoes nucleophilic addition to a carbonyl group in an amide bond to form a tetrahedral intermediate, which is subsequently cleaved to yield a new carboxyl-and amino-terminated group. This chain scission process accelerates moisture diffusion, forming a vicious circle, resulting in a decrease in the 14-day strength retention of the fiber to below 70% at 85 ℃ per 95% rh. Existing hydrolysis-resistant schemes mainly include melt copolymerization to introduce hydrolysis-resistant monomers (e.g., aromatic diacids) to reduce end-group density, bulk crosslinking using difunctional isocyanates (e.g., hexamethylene diisocyanate), or post-application coatings of epoxy resins or silane coupling agents, etc. However, these methods have significant drawbacks in that melt copolymerization tends to increase cost and reduce fiber spinnability, difunctional isocyanate crosslinking tends to cause fiber embrittlement, elongation degradation, and fatigue property degradation, and post-coating suffers from weak adhesion, easy peeling, poor environmental compatibility, and the like. In addition, the difunctional isocyanate may form a three-dimensional network that impedes the drainage of moisture from the interior of the fiber, further promoting localized hydrolysis. Disclosure of Invention In order to overcome at least one of the problems of the prior art, it is an object of the present invention to provide a method for modifying the surface of PA66 industrial yarn by blocking the surface of the monofunctional isocyanate, wherein the surface is blocked by the monofunctional isocyanate to avoid the negative effect of the bulk cross-linked network, and the hydrolysis active site is significantly reduced by selectively blocking the terminal amino group (forming a stable urea structure). The second object of the invention is to provide a surface end-capping modifying liquid for PA66 industrial yarns. The invention further aims to provide a surface end-capping modification method for the PA66 industrial yarn. The fourth object of the invention is to provide a surface-terminated modified PA66 industrial yarn. The invention aims at providing an application of the surface end-capped modified PA66 industrial yarn. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the first aspect of the invention provides the application of monofunctional isocyanate in the surface end-capping modification of PA66 industrial yarns. PA66, which is a semi-crystalline thermoplastic polyamide, has excellent mechanical strength, heat resistance and chemical resistance, but its hydrolytic sensitivity in humid environments limits its long-term stability in high performance applications, and the surface-capping modification solutions provided by the present invention can specifically address this problem. The reactivity of the monofunctional isocyanates (Monofunctional Isocyanate, MI) results from the electrophilicity of the-NCO groups, which have an addition rate constant with the amine groups of up to 10 3~105 L/mol.s (depending on the substituents), and the alicyclic or aryl structure provides steric hindrance to control the reaction depth. The invention uses the monofunctional isocyanate to react with the terminal amino group at the outermost layer of the fiber to form an alkyl/aryl urea end-capped structure, the reaction is based on the rapid addition of the monofunctional isocyanate and the amino group to form a urea bond (-NH-CO-NH-) which is more hydrolysis-resistant than an amide bond, so that the water absorption rate (by shielding a hydrophilic end group) and the hydrolysis active point (reducing a reversible hydrolysis site) can be greatly reduced, the strength retention rate of the modified fiber in a high-humidity and hot environment is effectively improved, and the industrial application requirement of long-term durability is met. In some embodiments of the invention, the monofunctional isocyanate is used as the sole isocyanate component in the surface-capping modification of the PA66 t