Continuous polymerization method of high-temperature-resistant polyamide

Abstract

The invention discloses a continuous polymerization method of high-temperature-resistant polyamide. The method comprises the following steps: (1) carrying out prepolymerization reaction on a polyamide salt solution, and carrying out subsection control on the temperature and pressure of the prepolymerization reaction by adopting 3-10 sections to obtain a first polyamide melt; and (2) carrying out final polymerization reaction on the first polyamide melt to obtain a second polyamide melt, and cooling to obtain the polyamide resin. Therefore, according to the method, an existing continuous polymerization process is optimized, a flash evaporation link is omitted, so that energy consumption is reduced, the method is suitable for production of high-temperature-resistant polyamide, and the high-temperature-resistant polyamide slices with high melting point, high viscosity, low YI, high fluidity and low water content are prepared.

Description

Technical Field

[0001] The invention relates to the field of high temperature resistant polyamide, and in particular to a continuous polymerization method of high temperature resistant polyamide. Background Art

[0002] High temperature polyamide (HTPA) is a type of polymer material with a melting point above 280°C and can be used in an environment above 200°C for a long time. It is widely used in electronic appliances, automobiles, military industry, aviation and other industries. Currently, commercialized HTPA includes: PA46, 6T, 9T, 10T and 12T. HTPA is mainly produced by prepolymerization-solid phase viscosity enhancement method and intermittent high-pressure melt polymerization method. The prepolymerization-solid phase viscosity enhancement method requires large investment, large equipment and long production cycle; the intermittent high-pressure melt polymerization method has high reaction temperature, poor batch reproducibility, low production efficiency, high energy consumption, easy to produce gel and black spots, and affects product performance and appearance. Polyamide with 1,5-pentanediamine as raw material has excellent melt fluidity, which provides the basic conditions for the continuous polymerization of HTPA.

[0003] At present, the continuous polymerization of polyamide is mainly used for the production of PA66. The process mainly includes: salt formation → concentration → high pressure precondensation → flash evaporation → prepolymerization → final polymerization. When the above process is directly used for the continuous polymerization of HTPA, on the one hand, since the flash evaporation, prepolymerization and final polymerization processes all need to be carried out at a temperature higher than the melting point of HTPA, the long high temperature residence time will cause HTPA to degrade, and then the product appearance will turn yellow and the performance will deteriorate. On the other hand, since the concentration of the polyamide salt solution (PA66) is about 50%, a large amount of water needs to be discharged during the concentration and prepolymerization process, which consumes a lot of energy.

[0004] Therefore, the existing continuous polymerization process is not suitable for the continuous preparation of high temperature resistant polyamide. Summary of the invention

[0005] The present invention aims to solve one of the technical problems existing in the prior art. To this end, the present invention proposes a continuous polymerization method for high temperature resistant polyamide. Thus, the method optimizes the existing continuous polymerization process, omits the flash evaporation link, thereby reducing energy consumption, and the method is suitable for the production of high temperature resistant polyamide, and prepares high temperature polyamide slices with high melting point, high viscosity, low YI, high fluidity and low water content.

[0006] In one aspect of the present invention, a continuous polymerization method for high temperature resistant polyamide is provided. According to an embodiment of the present invention, the method comprises: (1) subjecting a polyamide salt solution to a prepolymerization reaction, wherein the temperature and pressure of the prepolymerization reaction are controlled in stages of 3 to 10 stages to obtain a first polyamide melt; (2) subjecting the first polyamide melt to a final polymerization reaction to obtain a second polyamide melt, and cooling the melt to obtain a polyamide resin.

[0007] According to an embodiment of the present invention, the above-mentioned continuous polymerization method of high temperature resistant polyamide may also have the following additional technical features:

[0008] According to a specific embodiment of the present invention, in step (1), the polyamide salt solution is obtained by mixing a diamine monomer, an aliphatic diacid monomer A1, an aromatic diacid monomer A2 and water.

[0009] According to a specific embodiment of the present invention, during the mixing process, those skilled in the art can add additives as needed, such as catalysts, antioxidants, heat stabilizers, weathering agents, pigments, gloss enhancers, dyes, crystal nucleating agents, matting agents, plasticizers, antistatic agents, flame retardants, metals and metal salts, any one or a combination of several of them. By adding additives, the reaction speed can be accelerated, the product performance and stability can be improved, the high temperature polyamide can be given a higher quality and meet different downstream requirements. Wherein, the content of the additives is 0.05-0.7wt% of the above polyamide salt solution.

[0010] According to a specific embodiment of the present invention, the mixing temperature is 50-160°C, preferably 90-155°C.

[0011] According to a specific embodiment of the present invention, in step (1), the diamine monomer includes at least one of terminal diamines having 1 to 15 carbon atoms.

[0012] According to a specific embodiment of the present invention, in step (1), the aliphatic diacid monomer A1 includes at least one of terminal diacids having 4 to 18 carbon atoms.

[0013] According to a specific embodiment of the present invention, in step (1), the aromatic diacid monomer A2 includes at least one of terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, dibutyl terephthalate, and sodium terephthalate.

[0014] According to a specific embodiment of the present invention, in step (1), the concentration of the polyamide salt solution is 50-80wt%, preferably 55-75wt%, such as 60wt%, 65wt%, 70wt%, etc. Specifically, the polyamide salt solution can be prepared with reference to the patent publication CN112029090A.

[0015] According to a specific embodiment of the present invention, in step (1), the prepolymerization reaction time is 60 to 570 min, preferably 70 to 550 min, such as 100 min, 150 min, 200 min, 250 min, 300 min, 350 min, 400 min, 450 min, 500 min, etc.

[0016] According to a specific embodiment of the present invention, in step (1), the content of the first polyamide melt is 85-100wt%, preferably 92-99wt%, such as 88wt%, 91wt%, 94wt%, 97wt%, etc.

[0017] According to a specific embodiment of the present invention, in step (1), the temperature of the prepolymerization reaction is controlled to be 200-310° C., and the pressure of the prepolymerization reaction is below 3.2 MPa, preferably below 2.5 MPa.

[0018] According to a specific embodiment of the present invention, in step (1), the temperature and pressure of the prepolymerization reaction are controlled in stages using 3 to 10 stages.

[0019] According to a specific embodiment of the present invention, in step (1), the temperature of the segmented control is set as follows: the temperature of the first segment is 200-270°C, the temperature increases gradually by 0-40°C / segment, the insulation time of each segment is 6-180 minutes, and the temperature of the last segment is 280-310°C.

[0020] According to a specific embodiment of the present invention, in step (1), the pressure of the segmented control is set as follows: the pressure of the first segment is 2 to 2.5 MPa, the pressure decreases gradually by 0 to 1 MPa / segment, the holding time of each segment is 6 to 180 minutes, and the pressure of the last segment is 0 to 0.6 MPa.

[0021] According to a specific embodiment of the present invention, in step (2), the temperature of the final polymerization reaction is 290-340°C, preferably 295-330°C.

[0022] According to a specific embodiment of the present invention, in step (2), the final polymerization reaction is carried out under normal pressure or vacuum conditions. The reaction is carried out under normal pressure with inert gas protection, and the pressure under vacuum conditions is -0.095 to 0 MPa, preferably -0.09 to 0 MPa.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with preferred embodiments and comparative examples. It should be noted that the described embodiments are only representative embodiments and cannot represent all embodiments. The content described below is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0025] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0026] The polyamide salt solutions in the following examples and comparative examples were purchased from Cathay (Jinxiang) Biomaterials Co., Ltd.

[0027] Example 1

[0028] (1) subjecting the polyamide salt solution to a prepolymerization reaction, wherein the prepolymerization is controlled in four stages, wherein the temperature of the first stage is 232-259° C., the pressure is 2.1 MPa, the temperature of the last stage is 280-284° C., the pressure is 0.2 MPa, the prepolymerization time is 370 min, and the concentration of the first polyamide melt after the prepolymerization is 97 wt %;

[0029] (2) subjecting the first polyamide melt to a final polymerization reaction at a temperature of 303° C. and a pressure of −0.07 MPa to obtain a second polyamide melt, which is then cooled and pelletized to obtain a polyamide resin.

[0030] Example 2

[0031] 1,5-pentanediamine, pimelic acid and terephthalic acid were prepolymerized and final polymerized according to the process parameters in Table 1.

[0032] Example 3

[0033] 1,5-pentanediamine, suberic acid and terephthalic acid were prepolymerized and final polymerized according to the process parameters in Table 1.

[0034] Example 4

[0035] 1,5-pentanediamine, sebacic acid and terephthalic acid were prepolymerized and final polymerized according to the process parameters in Table 1.

[0036] Example 5

[0037] 1,5-pentanediamine, dodecyl dibasic acid and terephthalic acid were prepolymerized and final polymerized according to the process parameters in Table 1.

[0038] Comparative Example 1

[0039] (1) prepolymerizing the polyamide salt solution without stage control at a temperature of 270° C. and a pressure of less than 2.1 MPa for 370 min. The concentration of the first polyamide melt after prepolymerization is 89 wt %;

[0040] (2) subjecting the first polyamide melt to a final polymerization reaction at a temperature of 303° C. and a pressure of −0.7 MPa to obtain a second polyamide melt, which is then cooled and pelletized to obtain a polyamide resin.

[0041] Comparative Example 2

[0042] (1) subjecting the polyamide salt solution to a prepolymerization reaction, wherein the temperature of the prepolymerization reaction is controlled in four stages, wherein the temperature of the first stage is 232-259° C., the temperature of the last stage is 280-284° C., the pressure is 2.1 MPa, the prepolymerization time is 370 min, and the concentration of the first polyamide melt after the prepolymerization is 90 wt %;

[0043] (2) subjecting the first polyamide melt to a final polymerization reaction at a temperature of 303° C. and a pressure of −0.7 MPa to obtain a second polyamide melt, which is then cooled and pelletized to obtain a polyamide resin.

[0044] Comparative Example 3

[0045] (1) The temperature in the prepolymerization stage was controlled in 7 stages in the same manner as in Example 4, and the pressure in all 7 stages was 2.3 MPa;

[0046] (2) flashing the first polyamide melt obtained by prepolymerization, wherein the temperature of the heat transfer oil in the flash evaporator is controlled at 325° C., and the temperature of the second melt after flashing is 310° C. and the pressure is 10 KPa;

[0047] (3) subjecting the second polyamide melt obtained in step (2) to a final polymerization reaction at a temperature of 316° C. and a pressure of −0.085 MPa to obtain a third polyamide melt, which is then cooled and pelletized to obtain a polyamide resin.

[0048] The comparison of the properties of the polyamide resins obtained in Examples 1 to 5 and Comparative Examples 1 to 3 is shown in Table 1.

[0049] 1) Melting point test method: refer to standard ISO 11357-3.

[0050] 2) Test method for relative viscosity ηr: Ubbelohde viscometer concentrated sulfuric acid method, 96% concentration of sulfuric acid.

[0051] 3) Terminal amino group content: Accurately weigh 1g of sample and dissolve it in 40ml of hexafluoroisopropanol, record the mass m of the sample, and after it is completely dissolved, titrate it with 0.1mol / L HCl standard solution, record the molar concentration c of the standard solution and the volume V of the hydrochloric acid consumed, and calculate the amino group content: Terminal amino group content

[0052] 4) Yellow index: refer to HG / T3862-2006.

[0053] 5) Melt index: refer to GB / T 3682-2018.

[0054] 6) Molecular weight distribution

[0055] Testing instrument: Gel permeation chromatography

[0056] Test method: The test was carried out by gel permeation chromatography (GPC). The standard substance was PMMA and the solvent was hexafluoroisopropanol. After complete dissolution, it was filtered through a PTFE membrane and analyzed at 40°C to obtain the molecular weight and distribution relative to PMMA.

[0057] Table 1

[0058]

[0059]

[0060] From the analysis of Table 1, it can be seen that by controlling the temperature and pressure in stages during the prepolymerization stage, the flash evaporation step is reduced, and high-temperature polyamide chips with high melting point, high viscosity, low YI, high fluidity and low water content can be prepared. At the same time, the reaction is controlled to proceed step by step to make the molecular weight distribution narrower.

[0061] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A continuous polymerization method for high temperature resistant polyamide, characterized in that: The method comprises: (1) subjecting a polyamide salt solution to a prepolymerization reaction, wherein the temperature and pressure of the prepolymerization reaction are controlled in stages using 3 to 10 stages to obtain a first polyamide melt; (2) subjecting the first polyamide melt to final polymerization to obtain a second polyamide melt, and cooling the melt to obtain a polyamide resin.

2. The method according to claim 1, characterized in that The polyamide salt solution is obtained by mixing a diamine monomer, an aliphatic diacid monomer A1, an aromatic diacid monomer A2 and water; Optionally, the concentration of the polyamide salt solution is 50 to 80 wt%, preferably 55 to 75 wt%; Optionally, the diamine monomer includes at least one of terminal diamines having 1 to 15 carbon atoms; Optionally, the aliphatic diacid monomer A1 includes at least one of terminal diacids having 4 to 18 carbon atoms; optionally, the aromatic diacid monomer A2 includes at least one of terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, dibutyl terephthalate, and sodium terephthalate.

3. The method according to claim 1, characterized in that The prepolymerization reaction time is 60 to 570 minutes, preferably 70 to 550 minutes; Optionally, the content of the first polyamide melt is 85 to 100 wt%, preferably 92 to 99 wt%.

4. The method according to claim 1 or 3, characterized in that: The temperature setting of the segmented control is: the temperature of the first segment is 200-270°C, the temperature increases gradually by 0-40°C / segment, the insulation time of each segment is 6-180 minutes, and the temperature of the last segment is 280-310°C; Optionally, the pressure of the segmented control is set as follows: the pressure of the first segment is 2-2.5 MPa, the pressure decreases gradually by 0-1 MPa / segment, the pressure holding time of each segment is 6-180 min, and the pressure of the last segment is 0-0.6 MPa.

5. The method according to claim 1, characterized in that The temperature of the final polymerization reaction is 290-340°C, preferably 295-330°C; Optionally, the final polymerization reaction is carried out under normal pressure or vacuum conditions. The reaction is carried out under normal pressure with inert gas protection, and the pressure under vacuum conditions is -0.095 to 0 MPa, preferably -0.09 to 0 MPa.

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