Patent Application
20240052532
The present invention belongs to the field of polyester fiber, and more particularly, relates to a low-thermal-shrinkage polyester industrial yarn and preparation method thereof.
The high symmetry of the molecular chain structure of the polyester and the rigidity of the benzene ring make the product have good mechanical processing performance, chemical corrosion resistance, anti-microbial erosion performance and so on, and is widely applied to various fields such as fibers, films, and plastic products due to the advantages of relatively low price and easy recycling.
The thermal stability of the polyester is mainly manifested in two aspects, the ability to resist high temperature decomposition and the ability to resist higher environmental temperature when applied. The glass transition temperature is 70-76° C., the melting point is 250-260° C., and the thermal deformation temperature is 80-85° C. In order to meet the requirements of specific situations, the requirements for the performance of the industrial yarn are getting higher and higher, so that the polyester industrial yarn products need continuous innovation and research.
The disadvantage of the high-strength polyester industrial yarns is large thermal shrinkage, when the high-strength polyester industrial yarn is used for preparing tires, it is necessary to reduce the shrinkage rate and increase the modulus by adjusting the heat treatment condition of the cord fabric. With the increasing production of the polyester fiber, the quality of the fiber is increasingly demanding, often requiring excellent mechanical properties of the fiber, for example, fibers used in the preparation of automobile safety belts and sunshade cloths for household or industrial use, often requiring a lower dry-heat shrinkage rate, but due to the relatively large thermal shrinkage in the fibers prepared in the prior art, the application of the polyester industrial yarn is restricted.
It can be seen from the data of the polyester industry that the lower the shrinkage rate, the higher the crystallinity of the fiber, so to achieve a low shrinkage rate, the crystallinity of the yarn must be improved; the existing preparation process of the polyester industrial yarn mostly uses processes of spinning, multiple stretching and multiple shaping. On the one hand, high orientation is the structural basis for fiber materials to obtain high strength and high modulus; on the other hand, the high orientation system is also a thermodynamically unstable system entropy elasticity, which shows that the size of the fiber is unstable, that is, the fiber shrinks under the action of heat. Therefore, the requirements of both modulus and shrinkage performances on the structure are contradictory in nature. In the existing preparation process of the polyester industry, the shrinkage rate has reached a limit.
Therefore, it is an urgent problem to be solved to prepare a high-quality fiber with low shrinkage.
In order to solve the problem of certain limitations of how to reduce the shrinkage rate of the polyester industrial yarn in the prior art, the invention provides a low shrinkage polyester industrial yarn and preparation method thereof.
The invention solves the technical problem that the thermal shrinkage of the polyester industrial yarn in the prior art is relatively large, thereby restricting the application of the polyester industrial yarn.
The invention uses the coordination technology to reduce the thermal shrinkage rate of the polyester industrial yarn, so as to adapt to and broaden the application of the polyester industrial yarn.
To this end, the technical schemes of the invention are as follows: A low-thermal-shrinkage polyester industrial yarn, including: polyester segments of the low-thermal-shrinkage polyester industrial yarn includes a terephthalic acid segment, an ethylene glycol segment and a 2,5-pyridinedicarboxylic acid segment, and 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu2+;
For complexes, factors such as the charge, the radius, the ionization potential, and the electronegativity of the central atom all affect the stability of the coordination, that is, the higher the charge of the central atom, the smaller the radius, the higher the charge potential, and the more stable the generated complex. When metal ions form complexes with N and O in pyridine, the stability constant increases gradually with the number of d electrons in the central atom, reaching the maximum value in copper.
The electronic configuration of the outer layer of copper is 3d(10)4s(1), generally, the copper loses two electrons, and the electronic configuration on the outer layer is 3d(9). Nine electrons occupy five d orbitals, and there will inevitably be a single electron on one orbital. Copper ions form tetracoordinated compounds because the energy of one d orbital, one s orbital, and two p orbitals is similar, and can be hybridized to form unequal dsp2 hybridized orbitals, which can accommodate lone pair electrons of ligands and are easily coordinated with elements such as nitrogen, oxygen and so on to form stable complexes, forming a tetracoordinated compound.
The metal-ligand coordination interaction enhances the molecular interaction of macromolecular segments and hinders the movement of polymer chains. In the CuCl2-doped polyester fiber, one core of Cu(II) contains two pyridine ligands, and the coordination structure of the two intermolecular pyridine ligands tends to promote the aggregation of polymer chains. The formation of the metal-ligand coordination interaction enhances the intermolecular interaction, making the polymer segment more likely to be frozen, reducing the movement of molecular chains, and requiring more energy to “thaw” the “frozen” segments, which increases the difficulty of deorientation of the amorphous region, thereby reducing the thermal shrinkage of the polyester industrial yarn.
For ligands, most of the commonly used ligands are carboxylic acid and nitrogen-containing ligands: the carboxyl groups in carboxylic acid ligands can have strong coordination and chelation capabilities with metal ions. The 2,5-pyridinedicarboxylic acid belongs to nitrogen heterocyclic aromatic carboxylic acid ligands, which integrates the advantages of aromatic carboxylic acid ligands and nitrogen-containing heterocyclic ligands, and pyridine heterocycles can be combined with a variety of metals to form more metal complexes because of good electron-donating and electron-accepting capabilities; it has a closed large a bond, and there is a pair of lone pair electrons on the sp2 orbital of the N atom, which belongs to a non-centrosymmetric structure, and the conjugated electron donating and withdrawing groups can undergo charge transfer in the molecule, and it has a strong coordination ability, and its conjugation effect increases the stability of the complex.
Copper and 2,5-pyridinedicarboxylic acid forms two five-membered ring structure chelates. The chelate is a complex with a ring structure, and is obtained by chelating two or more ligands with the same metal ion to form a chelating ring. The stability of the chelate is closely related to the ring formation, which increases the stability of the chelate, wherein the five-membered ring and the six-membered ring are the most stable.
Since the coordination formed by copper with N and O is the most stable five-membered ring and six-membered ring, if the copper is coordinated with N and oxygen on the 4-position carbonyl, it is a seven-membered ring, which is unstable; copper forms a five-membered ring with N and oxygen on the 2-position carbonyl, and the coordination of copper is a tetracoordination, so the final formation is a chelate of two five-membered ring structures formed by copper and two 2,5-pyridine dicarboxylic acids.
The following preferred technology program is presented to give a detailed description for this invention: The said low-thermal-shrinkage polyester industrial yarn, wherein a coordination structure formed by Cu2+ coordination between 2,5-pyridinedicarboxylic acid segments of different polyester segments is:
The present invention also provides a method of preparing the low-thermal-shrinkage polyester industrial yarn, wherein the low-thermal-shrinkage polyester industrial yarn is prepared by spinning and winding a modified polyester after solid-state polycondensation to increase viscosity;
In the invention, copper chloride is added during polymerization, because the metal-ligand interaction maintains the dynamic reversibility of the supramolecular bond while achieve the memory property of thermal responsiveness through reversible covalent cross-linking in the form of metal-ligand coordination bonds. The property is, when the polyester is at a certain temperature, the cross-linked node between molecular segments will be dissociated, and the cross-linked network node will be regenerated during the cooling process.
The diffusion of the coordination agent into polyester fibers can be described by the so-called channel and free-volume models. Above the glass transition temperature of the polyester fiber, the free volume inside the fiber is relatively large, containing many “holes” enough to accommodate the entry of the coordination agent, the coordination agent molecules diffuse through the “hole”, and the polyester fiber has multiple movements units, including side groups, segments, and the entire polymer chain, etc., when the coordination agent molecule diffuses into the fiber, the coordination agent molecule is gradually combined with the ligand of the fiber within a certain time to form a relatively stable coordination compound structure unit, which greatly affects the amorphous region of the fiber and effectively reduces the thermal motion of the segment in the amorphous region, thereby reducing the thermal shrinkage of the polyester industrial filament. The coordination treatment after winding is a method of coordination, which has minimal impact on fiber processing, but takes a longer time; on the other hand, the weak point of the fiber tends to be in the amorphous region, and the method of coordination treatment is optimal for the effect of improving the amorphous region. After Cu(II) is coordinated with pyridine, the anion can participate in the coordination or play a role of neutralizing the charge in the complex.
At the same time, due to the large crystallinity of the polyester industrial yarn, under the condition of 80-100° C., the crystallization region has not yet been changed due to the heating temperature, while the molecular segment of the amorphous region is optimally arranged in a small range, which will not bring adverse effects on the breaking strength and breaking elongation of the fiber.
The following preferred technology program is presented to give a detailed description for this invention:
The mechanism of this invention is as follows:
For polyester industrial yarn, although the forming process is subject to high stress stretching and high temperature heat-setting, forming a highly crystalline and highly oriented structural feature, but due to the activity capability of the high-molecular-weight polyester molecular chain segment is limited (ie, the relaxation time is long), and the crystallization time in the thermal stretching and heat-setting process on the spinning process is limited, some segments that are not discharged into the crystal lattice are in a higher-energy straightening state or entanglement state, and stable “freezing” in this state at room temperature due to the decrease of temperature, far from reaching thermodynamic equilibrium state. Therefore, during the heating process of the polyester industrial yarn, that is, under the condition of 177° C., this part of the “frozen” segment first “thaws”, the activity capability is increased, that is, the deorientation of the amorphous region occurs, and the effect is especially obvious at a higher temperature and a shorter heating time, the occurrence of deorientation will lead to shrinkage of the fiber. At the same time, the shrinkage of the polyester industrial yarn is closely related to the degree of crystallinity and the integrity of crystallization.
In the invention, when the copper chloride molecules are dispersed into the fiber of the polyester industrial yarn, the copper chloride molecule and the ligand in the macromolecule are combined to form a relatively stable coordination structure unit, and the formation of the metal-ligand coordination interaction enhances intermolecular interaction and forms a physical cross-linking point, so that the “frozen” segment in the amorphous region forms a real “freeze”, effectively reduces the thermal movement of the segments in the amorphous region, which requires more energy to “thaw” the “frozen” segments, and increases the difficulty of deorientation in the amorphous region, thereby reducing the thermal shrinkage of the polyester industrial yarn; at the same time, the ligand used in the invention is 2,5-pyridinedicarboxylic acid, and when 2,5-pyridinedicarboxylic acid is introduced instead of terephthalic acid, the position of the two carboxyls is on the opposite side of the pyridine ring, and is highly similar to the terephthalic acid, reducing the influence on the structural regularity of the formed polyester, thereby will not affecting the degree of crystallinity and the integrity of crystallization.
From the thermodynamic perspective, the orientation decreases the entropy of the polymer system, thereby increasing the free energy, compared with the state before stretching, which is an unstable thermodynamic state that spontaneously converts into a non-oriented state-deorientation, and the speed of this process depends on kinetic factors. The polymer molecule motion unit has multiple properties, has different relaxation processes, and relies on temperature. Rapid cooling and quenching after drawing can “freeze” the orientation structure. If such a system is kept at a lower temperature, the rate of conversion to the equilibrium state is very slow, but at a higher temperature, the molecular motion is intensified, and the conversion rate of the system to the equilibrium state increases, which macroscopically appears as a shrinkage of the size. At the same time, the motions of various moving units of polymers are closely related to its stress state. There are interaction forces between molecular chains and within molecular chains; the macromolecular chains also have topological entanglement and physical entanglement, such as cohesive entanglement, microcrystals, etc., and the continuous polymer chains and the entanglements acting as physical crosslinks form a physical network structure. For oriented polymer materials such as crystallizable fibers, the possible influence of the presence of the crystalline region on the motion of segments in the amorphous region must be taken into account when analyzing their thermal shrinkage behavior.
In practical applications, polyester, due to the linear arrangement of molecular chains, is often subject to unavoidable effects on mechanical properties when heated because its segments are not supported by relatively strong cross-linking nodes. The cross-linking point can be a chemical cross-linking point or a physical cross-linking point, wherein the chemical cross-linking structure forms a stable intramolecular chemical bond, while the physical cross-linking structure includes hydrogen bonds, ionic bonds, and coordination bonds, etc.
Regardless of the physical cross-linking point or the chemical cross-linking point can effectively reduce the mobility of molecular segments, and the conversion rate of the system to the equilibrium state is reduced, which macroscopically appears as a reduction in the shrinkage rate of the size. At the same time, the stability of the cross-linking point is conducive to improving the interaction force between the molecular chains of the cross-linking point, which is beneficial to reducing the shrinkage rate.
Benefits:
Based on above mentioned method, the following embodiments are carried out for further demonstration in the present invention. It is to be understood that these embodiments are only intended to illustrate the invention and are not intended to limit the scope of the invention. In addition, it should be understood that after reading the contents described in the present invention, those technical personnel in this field can make various changes or modifications to the invention, and these equivalent forms also fall within the scope of the claims attached to the application.
A method of preparing the low-thermal-shrinkage polyester industrial yarn, including the following steps:
The polyester segments of the prepared low-thermal-shrinkage polyester industrial yarn includes the terephthalic acid segment, the ethylene glycol segment and the 2,5-pyridinedicarboxylic acid segment, the molar ratio of the terephthalic acid segment to the 2,5-pyridinedicarboxylic acid segment is 1:0.03; the 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu2, and the O atom on a carbonyl group and the N atom on the pyridine of the 2,5-pyridinedicarboxylic acid segment are involved in the coordination; the coordination structure formed by coordination is:
the low-thermal-shrinkage polyester industrial yarn has a linear density deviation rate of −1.5%, a breaking strength of 7.8 cN/dtex, a breaking strength CV value of 2.7%, a breaking elongation of 16%, a breaking elongation CV value of 6.4%, and a dry heat shrinkage rate of 2.5% at 177° C., 10 min and 0.05 cN/dtex.
A method of preparing the low-thermal-shrinkage polyester industrial yarn, including the following steps:
The polyester segments of the prepared low-thermal-shrinkage polyester industrial yarn includes the terephthalic acid segment, the ethylene glycol segment and the 2,5-pyridinedicarboxylic acid segment, the molar ratio of the terephthalic acid segment to the 2,5-pyridinedicarboxylic acid segment is 1:0.04; the 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu2+, and the O atom on a carbonyl group and the N atom on the pyridine of the 2,5-pyridinedicarboxylic acid segment are involved in the coordination; the coordination structure formed by coordination is:
the low-thermal-shrinkage polyester industrial yarn has a linear density deviation rate of −1%, a breaking strength of 8 cN/dtex, a breaking strength CV value of 2.75%, a breaking elongation of 14.7%, a breaking elongation CV value of 6.3%, and a dry heat shrinkage rate of 2.2% at 177° C., 10 min and 0.05 cN/dtex.
A method of preparing the low-thermal-shrinkage polyester industrial yarn, including the following steps:
The polyester segments of the prepared low-thermal-shrinkage polyester industrial yarn includes the terephthalic acid segment, the ethylene glycol segment and the 2,5-pyridinedicarboxylic acid segment, the molar ratio of the terephthalic acid segment to the 2,5-pyridinedicarboxylic acid segment is 1:0.05; the 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu2+, and the O atom on a carbonyl group and the N atom on the pyridine of the 2,5-pyridinedicarboxylic acid segment are involved in the coordination; the coordination structure formed by coordination is;
the low-thermal-shrinkage polyester industrial yarn has a linear density deviation rate of −0.5%, a breaking strength of 8.3 cN/dtex, a breaking strength CV value of 2.8%, a breaking elongation of 12.8%, a breaking elongation CV value of 6.5%, and a dry heat shrinkage rate of 2% at 177° C., 10 min and 0.05 cN/dtex.
A method of preparing the low-thermal-shrinkage polyester industrial yarn, including the following steps:
The polyester segments of the prepared low-thermal-shrinkage polyester industrial yarn includes the terephthalic acid segment, the ethylene glycol segment and the 2,5-pyridinedicarboxylic acid segment, the molar ratio of the terephthalic acid segment to the 2,5-pyridinedicarboxylic acid segment is 1:0.03; the 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu2, and the O atom on a carbonyl group and the N atom on the pyridine of the 2,5-pyridinedicarboxylic acid segment are involved in the coordination; the coordination structure formed by coordination is:
the low-thermal-shrinkage polyester industrial yarn has a linear density deviation rate of −0.4%, a breaking strength of 7.9 cN/dtex, a breaking strength CV value of 2.9%, a breaking elongation of 15.6%, a breaking elongation CV value of 6.6%, and a dry heat shrinkage rate of 2.4% at 177° C., 10 min and 0.05 cN/dtex.
A method of preparing the low-thermal-shrinkage polyester industrial yarn, including the following steps:
The polyester segments of the prepared low-thermal-shrinkage polyester industrial yarn includes the terephthalic acid segment, the ethylene glycol segment and the 2,5-pyridinedicarboxylic acid segment, the molar ratio of the terephthalic acid segment to the 2,5-pyridinedicarboxylic acid segment is 1:0.04; the 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu-+, and the O atom on a carbonyl group and the N atom on the pyridine of the 2,5-pyridinedicarboxylic acid segment are involved in the coordination; the coordination structure formed by coordination is:
the low-thermal-shrinkage polyester industrial yarn has a linear density deviation rate of 0.2%, a breaking strength of 8.1 cN/dtex, a breaking strength CV value of 2.8%, a breaking elongation of 13.9%, a breaking elongation CV value of 6.9%, and a dry heat shrinkage rate of 2.1% at 177° C., 10 min and 0.05 cN/dtex.
A method of preparing the low-thermal-shrinkage polyester industrial yarn, including the following steps:
The polyester segments of the prepared low-thermal-shrinkage polyester industrial yarn includes the terephthalic acid segment, the ethylene glycol segment and the 2,5-pyridinedicarboxylic acid segment, the molar ratio of the terephthalic acid segment to the 2,5-pyridinedicarboxylic acid segment is 1:0.04; the 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu2′, and the O atom on a carbonyl group and the N atom on the pyridine of the 2,5-pyridinedicarboxylic acid segment are involved in the coordination; the coordination structure formed by coordination is:
the low-thermal-shrinkage polyester industrial yarn has a linear density deviation rate of 0.9%, a breaking strength of 8.4 cN/dtex, a breaking strength CV value of 2.95%, a breaking elongation of 13.5%, a breaking elongation CV value of 6.7%, and a dry heat shrinkage rate of 2% at 177° C., 10 min and 0.05 cN/dtex.
A method of preparing the low-thermal-shrinkage polyester industrial yarn, including the following steps:
The polyester segments of the prepared low-thermal-shrinkage polyester industrial yarn includes the terephthalic acid segment, the ethylene glycol segment and the 2,5-pyridinedicarboxylic acid segment, the molar ratio of the terephthalic acid segment to the 2,5-pyridinedicarboxylic acid segment is 1:0.05; the 2,5-pyridinedicarboxylic acid segments of different polyester segments are coordinated by Cu2+, and the O atom on a carbonyl group and the N atom on the pyridine of the 2,5-pyridinedicarboxylic acid segment are involved in the coordination; the coordination structure formed by coordination is:
the low-thermal-shrinkage polyester industrial yarn has a linear density deviation rate of 1.5%, a breaking strength of 8.5 cN/dtex, a breaking strength CV value of 3%, a breaking elongation of 12.5%, a breaking elongation CV value of 7%, and a dry heat shrinkage rate of 1.9% at 177° C., 10 min and 0.05 cN/dtex.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202011607943.2 | Dec 2020 | CN | national |
This application is the national phase entry of International Application No. PCT/CN2021/114437, filed on Aug. 25, 2021, which is based upon and claims priority to Chinese Patent Application No. 202011607943.2, filed on Dec. 29, 2020, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/114437 | 8/25/2021 | WO |
