High-fluidity nylon 6 with narrow molecular weight distribution and preparation method thereof
By adding comonomer in the ring-open polymerization stage of caprolactam and controlling the polymerization conditions, the problem of widening the molecular weight distribution of nylon 6 was solved, and a high-flowing nylon 6 with narrow molecular weight distribution was prepared, which had good mechanical properties and easy moldability.
Patent Information
- Application Number
- CN202311423069.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-30
- Publication Date
- 2025-05-02
AI Technical Summary
In the preparation of high-flow nylon 6, the molecular weight distribution is easily widened, and gel particles or partially crosslinked structures are generated, affecting subsequent processing.
The appropriate comonomer is added during the ring-opening polymerization stage of caprolactam and the polymerization conditions are controlled to obtain a high-flowing nylon 6 with a narrow molecular weight distribution.
The narrowing of the molecular weight distribution and the reduction of relative viscosity are achieved, while the mechanical strength of nylon 6 is improved, easy molding and filler dispersion are achieved.
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Figure CN119912678A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a high-fluidity nylon 6 with a narrow molecular weight distribution and a preparation method thereof. Background Art
[0002] Nylon is a multi-variety polymer material with good comprehensive properties, including mechanical properties, heat resistance, chemical resistance, wear resistance and self-lubrication. It is easy to process and has the largest output, the most varieties and the widest application among the five major engineering plastics. It is used in automobiles, electrical equipment, mechanical parts, transportation, etc. With the acceleration of the process of miniaturization and lightweighting of automobiles and the high performance of electronic and electrical equipment, the demand for nylon will be greater, and higher requirements will be placed on the performance of nylon.
[0003] Nylon 6 is one of the most important varieties of nylon materials, with excellent comprehensive performance and easy processing and production. In order to meet the needs of different fields, nylon 6 is usually further processed and modified. In recent years, the dimensional accuracy requirements for nylon parts in automotive parts and electrical parts have become increasingly higher. At the same time, in the face of the requirements for large and thin-walled parts with complex structures, the fibers and other materials added during the processing process affect the fluidity of nylon 6, limiting their application.
[0004] High-flow nylon 6 has the characteristics of easy molding and excellent surface performance of products. It has low processing temperature and injection pressure and short molding cycle. It has obvious advantages in the preparation of high-mineral-filled and high-content glass fiber reinforced composite materials. Introducing branched structures into the molecular structure of nylon 6 is an important direction for the modification of nylon 6. By introducing branched structures into the polymer structure, the polymer is transformed from a linear structure to a three-dimensional spherical structure, which can obtain higher fluidity without significantly reducing the molecular weight. High-flow nylon 6 containing branched structures is usually prepared by blending or copolymerization. The blending processing method often requires adding a blending step after polymerization, which increases the complexity of the processing. Directly adding a branching agent for copolymerization often leads to a broadening of the molecular weight distribution, and even generates gel particles or partially cross-linked structures, which affects subsequent further processing. Summary of the invention
[0005] In order to solve the above technical problems existing in the prior art, the purpose of the present invention is to provide a high-flow nylon 6 with narrow molecular weight distribution and a preparation method thereof. By adding a suitable comonomer in the ring-opening polymerization stage of caprolactam and controlling the polymerization conditions, a branched nylon 6 with narrow molecular weight distribution, low relative viscosity and certain mechanical strength can be obtained, so as to achieve the purpose of easy molding and good dispersibility of fillers.
[0006] The first aspect of the present invention provides a high-flow nylon 6 with a narrow molecular weight distribution, the structure of which is shown in formula (1):
[0007]
[0008] In formula (1), A is a C2-C15 alkyl or aryl group; m is any integer from 2 to 4; n is any integer from 10 to 100;
[0009] When X is Then Y is Z is
[0010] When X is Then Y is Z is
[0011] When X is Then Y is Z is
[0012] The number average molecular weight of nylon 6 is 1.5×10 4 ~3.0×10 4 , molecular weight distribution is 1.4-2.0, melting point is 210-230°C, crystallization temperature is 170-195°C, and relative viscosity is 1.50-2.20.
[0013] The second aspect of the present invention provides a method for preparing the above-mentioned high-fluidity nylon 6 with narrow molecular weight distribution, the preparation method comprising: reacting a comonomer with caprolactam under ring-opening polymerization conditions in the presence of a ring-opening polymerization initiator;
[0014] The comonomer includes a small molecule or a dendritic macromolecule containing two or more amino groups, hydroxyl groups or carboxyl groups.
[0015] Compared with the prior art, the present invention has the following beneficial effects:
[0016] The invention adds a suitable comonomer in the ring-opening polymerization stage of caprolactam and controls the polymerization conditions to obtain branched nylon 6 with narrow molecular weight distribution, low relative viscosity and certain mechanical strength. The invention can solve the problem that the molecular weight distribution becomes broad and even gel particles or partially cross-linked structures are generated, which affect the subsequent further processing, and at the same time achieves the purpose of easy molding and good dispersibility for fillers, and has broad application prospects.
[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION
[0018] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0019] According to a first aspect of the present invention, the present invention provides a high-flow nylon 6 with a narrow molecular weight distribution, the structure of the nylon 6 is shown in formula (1):
[0020]
[0021] In formula (1), A is a C2-C15 alkyl or aryl group; m is any integer from 2 to 4; n is any integer from 10 to 100;
[0022] When X is Then Y is Z is
[0023] When X is Then Y is Z is
[0024] When X is Then Y is Z is
[0025] The number average molecular weight of nylon 6 is 1.5×10 4 ~3.0×10 4 , molecular weight distribution is 1.4-2.0, melting point is 210-230°C, crystallization temperature is 170-195°C, and relative viscosity is 1.50-2.20.
[0026] Preferably, the number average molecular weight of nylon 6 is 1.8×10 4 ~2.4×10 4 , molecular weight distribution is 1.6-1.8, melting point is 215-220°C, crystallization temperature is 175-190°C, and relative viscosity is 1.50-2.0.
[0027] In the present invention, the tensile elastic modulus of the nylon 6 is 2.50-4.00 GPa, the tensile stress is 40.0-80.0 MPa, the tensile strain is 1.0-7.0%, the fixed flexural bending stress is 50.0-100.0 MPa, the bending elastic modulus is 1.60-3.20 GPa, and the impact strength is 1.0-5.5 KJ / m 2 .
[0028] Preferably, the nylon 6 has a tensile elastic modulus of 2.70 to 3.80 GPa, a tensile stress of 47.0 to 68.0 MPa, a tensile strain of 1.2 to 5.0%, a constant flexural bending stress of 54.0 to 91.0 MPa, a bending elastic modulus of 1.70 to 3.00 GPa, and an impact strength of 1.2 to 5.2 KJ / m 2 .
[0029] According to a second aspect of the present invention, the present invention provides a method for preparing the above-mentioned high-fluidity nylon 6 with narrow molecular weight distribution, the preparation method comprising: reacting a comonomer with caprolactam under ring-opening polymerization conditions in the presence of a ring-opening polymerization initiator;
[0030] The comonomer includes a small molecule or a dendritic macromolecule containing two or more amino groups, hydroxyl groups or carboxyl groups.
[0031] Preferably, the comonomer is selected from at least one of small molecule 1,4-naphthalene dicarboxylic acid, 1,3,5-trimellitic acid, 1,2,4-trimellitic acid, pyromellitic acid, 2-aminoterephthalic acid, 2,2',2"-triaminotriethylamine and trimethylolpropane. The structure of each comonomer is as follows:
[0032]
[0033] According to the present invention, based on the amount of caprolactam, the amount of initiator can be 0.5-20.0 wt%, preferably 1.0-18.0 wt%; the amount of comonomer can be 0.01-10.0 wt%, preferably 0.1-5.0 wt%.
[0034] In the present invention, the ring-opening polymerization initiator can be selected from at least one of water, aminocaproic acid, sodium hydroxide, potassium hydroxide and alkali metals, preferably water or aminocaproic acid. The water is desalted water.
[0035] According to the present invention, the conditions of the ring-opening polymerization reaction may include: a reaction temperature of 200 to 280° C., a reaction pressure of 0 to 0.3 MPa, and a reaction time of 1 to 15 hours.
[0036] Preferably, the conditions of the ring-opening polymerization reaction include: reaction temperature of 230-265° C., reaction pressure of 0.05-0.1 MPa, and reaction time of 1.5-10 hours.
[0037] The preparation method of the present invention further comprises: removing unreacted monomers from the nylon 6 melt obtained after the reaction under reduced pressure, and then discharging the nylon 6 melt into desalted water for crystallization and pelletization.
[0038] The materials and process parameters not limited in the present invention can be selected according to the existing technology and belong to the conventional technical means in this field.
[0039] The present invention will be further described below with reference to the following examples, but is not limited to these examples.
[0040] In the following examples and comparative examples, the relevant data were obtained according to the following test methods:
[0041] 1. Relative viscosity: Weigh 0.25g of nylon sample into a 25mL volumetric flask, add concentrated sulfuric acid (below the scale line), and after the nylon sample is completely dissolved, add concentrated sulfuric acid to the liquid level in the volumetric flask to the scale line and shake well for testing. Use a pipette to measure 10mL of the prepared solution and add it to an Ubbelohde viscometer with a capillary diameter of 1.0-1.1mm, and install the viscometer vertically in a constant temperature water bath at (25±0.5)℃ and keep the constant temperature for 20min. Measure the time for the solution to flow between the two scale lines of the viscometer, which is the flow time t of the solution. The flow time of pure solvent concentrated sulfuric acid is t0. Each sample is tested 3 times, and the error before and after does not exceed ±0.2s, and the average value is taken. The relative viscosity η of the nylon sample can be calculated according to the following formula:
[0042]
[0043] 2. Number average molecular weight and molecular weight distribution: determined by GPC.
[0044] 3. Melting point and crystallization temperature: determined by DSC.
[0045] 4. Mechanical properties: Tensile elastic modulus is measured according to GB / T1040.2-2022; tensile stress and tensile strain are measured according to GB / T1040.2-2006; constant flexural bending stress and bending elastic modulus are measured according to GB9341; impact strength is measured according to GB / T1043.1-2008.
[0046] Example 1
[0047] 18 g of aminocaproic acid, 140 g of caprolactam and 2.80 g (2.0 wt%) of 1,4-naphthalene dicarboxylic acid were added to a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 170°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 258°C. After 2.5 hours of polymerization, the heating was turned off and the unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P1 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0048] Example 2
[0049] 20 g of aminocaproic acid, 140 g of caprolactam and 2.10 g (1.5 wt%) of 1,3,5-trimethylbenzene were added into a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 180°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 255°C. After polymerization for 3.5 hours, the heating was turned off and the unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P2 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0050] Example 3
[0051] 22 g of aminocaproic acid, 140 g of caprolactam and 2.52 g (1.8 wt%) of 1,2,4-trimethylolpropane were added into a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 175°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 252°C. After polymerization for 3.5 hours, the heating was turned off and the unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P3 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0052] Example 4
[0053] 2 g of desalted water, 140 g of caprolactam and 3.08 g (2.2 wt%) of pyromellitic acid were added into a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 178°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 265°C. After 2.5 hours of polymerization, the heating was turned off and the unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P4 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0054] Example 5
[0055] 15 g of aminocaproic acid, 140 g of caprolactam and 3.50 g (2.5 wt%) of 2-aminoterephthalic acid were added to a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 185°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 250°C. After 4 hours of polymerization, the heating was turned off and the unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P5 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0056] Example 6
[0057] 5 g of desalted water, 140 g of caprolactam and 1.40 g (1.0 wt%) of 2,2',2"-triaminotriethylamine were added to a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 188°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 261°C. After polymerization for 3 hours, the heating was turned off and unreacted monomers were removed at a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P6 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0058] Example 7
[0059] 24 g of aminocaproic acid, 140 g of caprolactam and 2.10 g (1.5 wt%) of 2,2',2"-triaminotriethylamine were added to a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 182°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 261°C. After polymerization for 3 hours, the heating was turned off and the unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P7 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0060] Example 8
[0061] 4 g of desalted water, 140 g of caprolactam and 1.54 g (1.1 wt%) of trimethylolpropane were added into a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 180°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 255°C. After polymerization for 3 hours, the heating was turned off and unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P8 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0062] Example 9
[0063] 20 g of aminocaproic acid, 140 g of caprolactam and 1.96 g of trimethylolpropane (1.4 wt%) were added into a polymerization reactor. After nitrogen substitution, the reactor was stirred and heated to 178°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 259°C. After polymerization for 3.5 hours, the heating was turned off and the unreacted monomers were removed under a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain high-fluidity nylon 6 polymer P9 chips with narrow molecular weight distribution. The performance parameters are shown in Table 1.
[0064] Comparative Example 1
[0065] 24 g of aminocaproic acid and 140 g of caprolactam were added into a polymerization reactor and replaced with nitrogen. The reactor was stirred and heated to 182°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 261°C. After polymerization for 3 hours, the heating was turned off and the unreacted monomers were removed at a pressure of 2000 Pa. The nylon melt was discharged into desalted water, crystallized and pelletized to obtain nylon polymer P-c1 chips. The performance parameters are shown in Table 1.
[0066] Comparative Example 2
[0067] 24 g of aminocaproic acid, 140 g of caprolactam, and 16.80 g (12.0 wt%) of 2,2',2"-triaminotriethylamine were added to a polymerization reactor. After nitrogen replacement, the reactor was stirred and heated to 182°C to make the reactants uniformly mixed in a molten state. The reactor was kept at normal pressure and heated to 261°C. After polymerization for 3 hours, the heating was turned off, and the unreacted monomers were removed at a pressure of 2000 Pa, and the nylon melt was discharged into desalted water. Since the nylon melt has too high fluidity and is in a low-viscosity liquid state, it cannot be effectively cooled and crystallized in the process of rapidly flowing out of the reactor into the desalted water, making it difficult to conduct subsequent relative viscosity testing and characterization.
[0068] Table 1
[0069]
[0070] The reaction conditions of Comparative Example 1 are the same as those of Example 7, except that no comonomer is added, and the reaction is a homopolymerization of caprolactam. It can be seen that the molecular weight distribution of the polymer is relatively wide (2.81). From the data of Examples 1 to 9 and Comparative Examples 1 to 2, it can be seen that the method of adding a certain proportion of branched polymerization monomers during the caprolactam ring-opening polymerization used in Examples 1 to 9 can prepare high-flow nylon 6 with a narrow molecular weight distribution.
[0071] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.
Claims
1. A high-flow nylon 6 with a narrow molecular weight distribution, characterized in that: The structure of nylon 6 is shown in formula (1): In formula (1), A is a C2-C15 alkyl or aryl group; m is any integer from 2 to 4; n is any integer from 10 to 100; When X is Then Y is Z is When X is Then Y is Z is When X is Then Y is Z is The number average molecular weight of nylon 6 is 1.5×10 4 ~3.0×10 4 , molecular weight distribution is 1.4-2.0, melting point is 210-230°C, crystallization temperature is 170-195°C, and relative viscosity is 1.50-2.
20.
2. The high-flow nylon 6 with narrow molecular weight distribution according to claim 1, wherein The number average molecular weight of nylon 6 is 1.8×10 4 ~2.4×10 4 , molecular weight distribution is 1.6-1.8, melting point is 215-220°C, crystallization temperature is 175-190°C, and relative viscosity is 1.50-2.
0.
3. The high-flow nylon 6 with narrow molecular weight distribution according to claim 1, wherein The nylon 6 has a tensile elastic modulus of 2.50 to 4.00 GPa, a tensile stress of 40.0 to 80.0 MPa, a tensile strain of 1.0 to 7.0%, a constant flexural bending stress of 50.0 to 100.0 MPa, a bending elastic modulus of 1.60 to 3.20 GPa, and an impact strength of 1.0 to 5.5 KJ / m 2 .
4. The high-flow nylon 6 with narrow molecular weight distribution according to claim 3, wherein The nylon 6 has a tensile elastic modulus of 2.70 to 3.80 GPa, a tensile stress of 47.0 to 68.0 MPa, a tensile strain of 1.2 to 5.0%, a constant flexural bending stress of 54.0 to 91.0 MPa, a bending elastic modulus of 1.70 to 3.00 GPa, and an impact strength of 1.2 to 5.2 KJ / m 2 .
5. The method for preparing high-flow nylon 6 with narrow molecular weight distribution according to any one of claims 1 to 4, characterized in that: The preparation method comprises: reacting a comonomer with caprolactam under ring-opening polymerization conditions and in the presence of a ring-opening polymerization initiator; The comonomer includes a small molecule or a dendritic macromolecule containing two or more amino groups, hydroxyl groups or carboxyl groups.
6. The method for preparing high-flow nylon 6 with narrow molecular weight distribution according to claim 5, wherein: The comonomer is selected from at least one of 1,4-naphthalene dicarboxylic acid, 1,3,5-trimellitic acid, 1,2,4-trimellitic acid, pyromellitic acid, 2-aminoterephthalic acid, 2,2',2"-triaminotriethylamine and trimethylolpropane.
7. The method for preparing high-flow nylon 6 with narrow molecular weight distribution according to claim 5, wherein: Calculated on the amount of caprolactam, the amount of the initiator is 0.5-20.0 wt%, preferably 1.0-18.0 wt%; the amount of the comonomer is 0.01-10.0 wt%, preferably 0.1-5.0 wt%.
8. The method for preparing high-flow nylon 6 with narrow molecular weight distribution according to claim 5, wherein: The ring-opening polymerization initiator is selected from at least one of water, aminocaproic acid, sodium hydroxide, potassium hydroxide and alkali metals; preferably water or aminocaproic acid.
9. The method for preparing high-flow nylon 6 with narrow molecular weight distribution according to claim 5, wherein: The conditions of the ring-opening polymerization reaction include: reaction temperature of 200-280° C., reaction pressure of 0-0.3 MPa, and reaction time of 1-15 hours.
10. The method for preparing high-flow nylon 6 with narrow molecular weight distribution according to claim 9, wherein: The conditions of the ring-opening polymerization reaction include: reaction temperature of 230-265° C., reaction pressure of 0.05-0.1 MPa, and reaction time of 1.5-10 hours.