Polyamide resin with low free diamine content, process for its preparation and use thereof

Abstract

The application relates to the technical field of high-molecular polymerization and engineering plastics, and particularly provides a polyamide resin with low free diamine content and a preparation method and application thereof. The preparation method comprises the following steps: extracting polyamide resin obtained after solid-phase viscosity increase with alcohol; and adding an alcohol extraction process after the viscosity increase of the polyamide resin is completed. The method can significantly reduce the content of free diamine in the polyamide resin and improve the color of the resin. The method is simple in process, convenient in operation and low in cost. The content of free diamine in the polyamide resin prepared by the method is not higher than 100 ppm.

Description

Technical Field

[0001] This invention relates to the field of polymer polymerization and engineering plastics technology, and in particular to a polyamide resin with low free diamine content, its preparation method and application. Background Technology

[0002] Polyamide (PA), commonly known as nylon, has been industrialized for over eighty years since the 1930s. Initially used primarily as a raw material for spinning, it was only after the 1950s that it was used as an engineering plastic. With the rapid development of applications in the automotive, electronics, transportation, machinery, aerospace, and various daily consumer industries, its production and demand have risen to the top among the five major engineering plastics. Polyamide resins possess excellent comprehensive properties, including mechanical properties, heat resistance, wear resistance, chemical resistance, and self-lubricating properties, as well as a low coefficient of friction and some flame retardancy. They are widely used for reinforcement and modification with glass fiber and other fillers to improve performance and expand applications. In recent years, semi-aromatic polyamides have been a focus of development due to their superior heat resistance and mechanical properties.

[0003] However, the presence of free diamines in polyamide resins can affect their processing and performance, especially for semi-aromatic polyamides, which are generally polymerized from monomers such as diamines with benzene rings and aliphatic diacids, or diamines with benzene rings and aliphatic diamines. Residual free diamines in the resin not only reduce its processing performance but also darken the color of semi-aromatic polyamides. This is mainly due to the yellowing of free diamines upon contact with air or under heat, which is one of the reasons for poor resin color. Furthermore, it is difficult to improve the resin color, especially by changing the current preparation process.

[0004] Therefore, reducing the content of free diamine in polyamide resins is of great significance. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in the prior art. Therefore, one object of this invention is to provide a polyamide resin with low free diamine content, its preparation method, and its applications.

[0006] In a first aspect, the present invention provides a method for preparing a polyamide resin with low free diamine content, the method comprising: The polyamide resin obtained after solid-phase thickening was extracted with alcohol.

[0007] According to the method for preparing polyamide resin with low free diamine content described above, the polyamide resin obtained after solid-phase thickening is extracted with alcohol. That is, an alcohol extraction process is added after the polyamide resin thickening is completed. This effectively removes residual free diamine from the polyamide resin, reduces the free diamine content, and thus improves the color and processing performance of the polyamide resin. Furthermore, this method is simple, easy to operate, and low in cost.

[0008] Specifically, the polyamide resin obtained after solid-phase thickening is extracted with alcohol. The alcohol containing dissolved free diamine is then filtered through a filter at the bottom of the reactor. The mixture is then heated (e.g., 70°C) and vacuumed to remove residual alcohol, thus obtaining a polyamide resin with low free diamine content. Furthermore, the reactor is a reaction vessel.

[0009] According to the method for preparing polyamide resin with low free diamine content of the present invention, the alcohol includes at least one of methanol, ethanol, and propanol, preferably ethanol.

[0010] According to the method for preparing polyamide resin with low free diamine content of the present invention, the mass ratio of polyamide resin to alcohol is 1:(2-10), preferably 1:(4-9), for example, a mass ratio of 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any range between any two of the above values. By controlling the mass ratio of polyamide resin to alcohol within the above range, residual free diamine in the polyamide resin can be effectively removed.

[0011] Preferably, the mass ratio of the semi-aromatic polyamide resin to the alcohol is 1:(2-10), more preferably 1:(4-9), for example, a mass ratio of 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any range between the above two values. The inventors have found that if the amount of alcohol added is too small, the free diamine is not completely removed; if the amount of alcohol added is too large, it affects the viscosity of the resin and reduces its processing performance. Therefore, by controlling the mass ratio of the semi-aromatic polyamide resin to the alcohol within the above range, the residual free diamine in the semi-aromatic polyamide resin can be effectively removed, significantly improving the color of the resin and ensuring its processing performance.

[0012] According to the method for preparing polyamide resin with low free diamine content of the present invention, the extraction temperature is 70℃ to 150℃, and the extraction time is 2h to 4h. For example, the extraction temperature is 70℃, 80℃, 100℃, 120℃, 150℃, etc., or any range between any two of the above values; the extraction time is 2h, 3h, 4h, etc., or any range between any two of the above values. By controlling the extraction temperature and time within the above range, the free diamine in the resin can be effectively extracted into ethanol, while retaining the resin's optimal processing properties.

[0013] Preferably, stirring is performed during the extraction process.

[0014] Preferably, the semi-aromatic polyamide resin obtained after solid-phase thickening is extracted with alcohol.

[0015] In some embodiments of the present invention, the semi-aromatic polyamide resin is composed of the following repeating units: (a) terephthalic acid or its derivatives, and optionally one or more other aromatic or aliphatic diacids; (b) One or more aliphatic diamines having 10 to 20 carbon atoms, and optionally one or more aliphatic diamines having 4 to 9 carbon atoms; (c) Optionally one or more aminocarboxylic acids and / or lactams; Of which, terephthalic acid or its derivatives account for 50 to 100 mol% of the total of (a), one or more aliphatic diamines having 10 to 20 carbon atoms account for 50 to 100 mol% of the total of (b), and one or more aminocarboxylic acids and / or lactams account for 0 to 25 mol% of the total of (a) + (b) + (c).

[0016] In some embodiments of the present invention, the aromatic or aliphatic diacid is selected from one or more of isophthalic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, 2-methyloctanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, or tetradecanoic acid.

[0017] In some embodiments of the present invention, the aliphatic diamine with 10 to 20 carbon atoms is selected from one or more of the following: decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecananediamine, octadecanediamine, nonadecananediamine, and eicosanediamine.

[0018] In some embodiments of the present invention, the aliphatic diamine with 4 to 9 carbon atoms is selected from one or more of butanediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, and 2-methyloctanediamine.

[0019] In some embodiments of the present invention, the aminocarboxylic acid or lactam is selected from one or more of 6-aminohexanoic acid, caprolactam, 10-aminodecanoic acid, 11-aminoundecanoic acid, undecanolactam, 12-aminododecanoic acid, or dodecanolactam.

[0020] Preferably, the repeating unit (b) contains only at least one of 1,10-decanediamine and 1,6-hexanediamine.

[0021] Preferably, the content of the repeating unit (c) is 0.

[0022] In some embodiments of the present invention, the polymerization method of the above-mentioned semi-aromatic polyamide resin includes: adding the reactants to a pressure vessel, evacuating and filling it with high-purity argon as a protective gas, initiating the reaction, heating the reaction mixture to 220°C–230°C and stirring for 3–5 hours, then opening the valve to slowly release pressure and drain water while maintaining constant temperature and pressure. Drainage continues until the amount of water reaches 70% of the amount of deionized water added. At this point, the temperature is raised to 250°C–270°C and held for 2 hours. After the reaction is complete, the valve is opened to discharge the material, obtaining the prepolymer. The melting point of the prepolymer is tested and set as T°C. The prepolymer is then vacuum-dried at 80°C for 24 hours.

[0023] Furthermore, the thickening stage includes: subjecting the above prepolymer to solid-phase thickening at a temperature 40–70°C below its melting point to obtain a semi-aromatic polyamide resin.

[0024] In a second aspect, the present invention provides a polyamide resin with low free diamine content, which is prepared by the method described above.

[0025] According to the polyamide resin with low free diamine content of the present invention, the free diamine content in the polyamide resin is not higher than 100 ppm. For example, the free diamine content in the polyamide resin is 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, etc., or a range between any two of the above values. Having a free diamine content in the polyamide resin not higher than 100 ppm can significantly improve the color change problem of the resin and enhance its processing performance and stability.

[0026] In some embodiments of the present invention, the content of free diamine in the semi-aromatic polyamide resin is not higher than 100 ppm.

[0027] According to the polyamide resin with low free diamine content of the present invention, the Gannz whiteness of the polyamide resin is 70 to 76. For example, the Gannz whiteness is 70, 71, 72, 73, 74, 75, 76, etc., or a range between any two of the above values.

[0028] In some embodiments of the present invention, the Ganz whiteness of the semi-aromatic polyamide resin is 70-76.

[0029] According to the polyamide resin with low free diamine content of the present invention, when the concentration of the polyamide resin is measured in 98% concentrated sulfuric acid at 25℃±0.01℃ at 10mg / ml, the relative viscosity of the polyamide resin is 1.85-2.8, preferably 2.0-2.45. For example, the relative viscosity is 1.85, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, etc., or any range between any two of the above values. The polyamide resin with low free diamine content having a viscosity within the above range has excellent processing and application value.

[0030] In some embodiments of the present invention, the relative viscosity of the semi-aromatic polyamide resin, measured in a 10 mg / ml sample in 98% concentrated sulfuric acid at 25°C ± 0.01°C, is 1.85-2.8, preferably 1.85-2.45, and more preferably 2.0-2.3. Semi-aromatic polyamide resins with lower relative viscosity have poorer performance, but those with excessively high relative viscosity have poor processing flowability. The semi-aromatic polyamide resin of the present invention has a viscosity within the above-mentioned range, exhibiting excellent processing performance.

[0031] In some embodiments of the present invention, the melting point of the semi-aromatic polyamide resin is 240°C to 340°C.

[0032] As an example, the melting point of a semi-aromatic polyamide resin with a high melting point is 280–340°C, preferably 290–330°C, and more preferably 295–325°C.

[0033] As an example, the melting point of a semi-aromatic polyamide resin with a low melting point is 240°C to 279°C, preferably 245°C to 270°C.

[0034] In a third aspect, the present invention provides a polyamide molding composition comprising the aforementioned polyamide resin with low free diamine content.

[0035] In some embodiments of the present invention, the above-described polyamide molding composition further includes at least one of a reinforcing material and an additive. It should be noted that the reinforcing material and the additive are conventional materials in the art, and those skilled in the art can select them according to actual needs.

[0036] Furthermore, on a 100% weight basis, the composition comprises 30-95 wt% of a polyamide resin with low free diamine content, 0-70 wt% of a reinforcing material, and 0-50 wt% of an additive.

[0037] In a fourth aspect, the present invention provides a molded article prepared using the above-described polyamide molding composition.

[0038] In some embodiments of the present invention, the molded articles described above include, but are not limited to, various components.

[0039] Furthermore, examples include automotive parts and mechanical parts, specifically automotive engine cooling water system parts, radiator water tank parts, coolant reservoirs, water pipes, water pump housings, water pump impellers, valves, miniature slide switches, DIP switches, switch housings, lamp holders, cable ties, connectors, connector housings, connector shells, IC sockets, spools, spool covers, relays, relay boxes, capacitor housings, internal motor parts, miniature motor housings, gear cams, balance wheels, gaskets, insulators, fasteners, buckles, wire clips, bicycle wheels, casters, safety helmets, terminal blocks, power tool housings, starter insulation parts, baffles, cans, radiator water tanks, cavity tanks, reservoirs, fuse boxes, air purifier housings, air conditioning fans, terminal housings, wheel covers, intake and exhaust pipes, bearing supports, cylinder head covers, intake manifolds, water pipe impellers, clutch release levers, speaker diaphragms, heat-resistant containers, microwave oven parts, rice cooker parts, printer ribbon guides, etc.

[0040] In some embodiments of the present invention, the above-mentioned molded articles are formed by any molding method such as injection molding, extrusion molding, blow molding, vacuum molding, melt spinning, and film molding.

[0041] The present invention has at least the following beneficial effects: This invention adds an extraction process after the thickening of semi-aromatic polyamide, which can significantly reduce the content of free diamine in the resin and improve the resin color. Detailed Implementation

[0042] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0043] Example 1 The raw materials used to prepare the semi-aromatic polyamide in this embodiment are shown in Table 1.

[0044] The preparation process of the semi-aromatic polyamide in this embodiment is as follows: (1) Add the reactants to a pressure vessel according to the formula in Table 1, evacuate the vessel, and purge with high-purity argon as a protective gas to begin the reaction. Heat the reaction mixture to 225°C and stir for 4 hours. Then, open the valve to slowly release the pressure and drain the water while maintaining constant temperature and pressure. Continue draining until the amount of water discharged reaches 70% of the amount of deionized water added. At this point, raise the temperature to 260°C and hold for 2 hours. After the reaction is complete, open the valve to discharge the prepolymer. Test the melting point of the prepolymer and set it as T°C.

[0045] (2) After the prepolymer is vacuum dried at 80°C for 24 hours, the prepolymer is subjected to solid-phase thickening at 50°C below the melting point to obtain a semi-aromatic polyamide resin.

[0046] (3) The semi-aromatic polyamide resin and the extractant ethanol were placed in a reaction vessel, with the ratio of semi-aromatic polyamide resin to ethanol being 1:2. The temperature was then raised to 100°C and stirred for 3 hours, followed by a drop to room temperature. The ethanol solution containing decanediamine was filtered out through a filter screen at the bottom of the reaction vessel. The temperature was then raised to 70°C, and the remaining ethanol was removed by vacuuming, finally yielding a semi-aromatic polyamide resin with low free diamine content.

[0047] Example 2 The raw materials used to prepare the semi-aromatic polyamide in this embodiment are shown in Table 1.

[0048] The difference between the preparation process of the semi-aromatic polyamide in this embodiment and that in Example 1 is that the ratio of semi-aromatic polyamide resin to ethanol is 1:4.

[0049] Example 3 The raw materials used to prepare the semi-aromatic polyamide in this embodiment are shown in Table 1.

[0050] The difference between the preparation process of the semi-aromatic polyamide in this embodiment and that in Example 1 is that the ratio of semi-aromatic polyamide resin to ethanol is 1:6.

[0051] Example 4 The raw materials used to prepare the semi-aromatic polyamide in this embodiment are shown in Table 1.

[0052] The difference between the preparation process of the semi-aromatic polyamide in this embodiment and that in Example 1 is that the ratio of semi-aromatic polyamide resin to ethanol is 1:9.

[0053] Example 5 The raw materials used to prepare the semi-aromatic polyamide in this embodiment are shown in Table 1.

[0054] The difference between the preparation process of the semi-aromatic polyamide in this embodiment and that in Example 1 is that the ratio of semi-aromatic polyamide resin to ethanol is 1:6.

[0055] Example 6 The raw materials used to prepare the semi-aromatic polyamide in this embodiment are shown in Table 1.

[0056] The preparation process of the semi-aromatic polyamide in this embodiment is the same as that in Example 5.

[0057] Example 7 The raw materials used to prepare the semi-aromatic polyamide in this embodiment are shown in Table 1.

[0058] The preparation process of the semi-aromatic polyamide in this embodiment is the same as that in Example 5.

[0059] Comparative Example 1 The raw materials used in the preparation of the semi-aromatic polyamide in this comparative example are shown in Table 1.

[0060] The difference between the preparation process of the semi-aromatic polyamide in this comparative example and that in Example 1 is that Comparative Example 1 has no step (3).

[0061] Comparative Example 2 The raw materials used in the preparation of the semi-aromatic polyamide in this comparative example are shown in Table 1.

[0062] The difference between the preparation process of the semi-aromatic polyamide in this comparative example and that in Example 1 is that the ratio of semi-aromatic polyamide resin to ethanol is 1:1.

[0063] Comparative Example 3 The raw materials used in the preparation of the semi-aromatic polyamide in this comparative example are shown in Table 1.

[0064] The difference between the preparation process of the semi-aromatic polyamide in this comparative example and that in Example 1 is that the ratio of semi-aromatic polyamide resin to ethanol is 1:15.

[0065] Comparative Example 4 The raw materials used in the preparation of the semi-aromatic polyamide in this comparative example are shown in Table 1.

[0066] The difference between the preparation process of the semi-aromatic polyamide in this comparative example and that in Example 3 is as follows: (3) Place the semi-aromatic polyamide resin and ethanol in a reaction vessel, wherein the ratio of the semi-aromatic polyamide resin to the extractant acetone is 1:6. Then raise the temperature to 100℃, stir for 3 hours, and then lower to room temperature. Filter the acetone solution containing decanediamine through the filter screen at the bottom of the reaction vessel. Then raise the temperature to 70℃, and remove the remaining acetone by vacuuming, finally obtaining a semi-aromatic polyamide resin with low free diamine content.

[0067] Comparative Example 5 The raw materials used in the preparation of the semi-aromatic polyamide in this comparative example are shown in Table 1.

[0068] The difference between the preparation process of the semi-aromatic polyamide in this comparative example and that in Example 3 is as follows: (3) The semi-aromatic polyamide resin and ethanol were placed in a reaction vessel, with the ratio of semi-aromatic polyamide resin to ethyl acetate extractant being 1:6. The temperature was then raised to 100°C and stirred for 3 hours, followed by a drop to room temperature. The ethyl acetate solution containing decanediamine was filtered out through a filter screen at the bottom of the reaction vessel. The temperature was then raised to 70°C, and the remaining ethyl acetate was removed under vacuum, finally yielding a semi-aromatic polyamide resin with low free diamine content.

[0069] The properties of the polyamide resins in the above embodiments and comparative examples were tested, and the specific methods are as follows: (1) Test method for melting point of semi-aromatic polyamide resin and its prepolymer: Refer to ASTM D3418-2003, Standard Test Method for Transition Temperatures of Polymers By Differential Scanning Calorimetry; The specific test method is: use a Perkin Elmer Diamond DSC analyzer to test the melting point of the sample; heating rate 10℃ / min; (2) Test method for relative viscosity of semi-aromatic polyamide resin: Refer to GB12006.1-89; The specific test method is as follows: Measure the relative viscosity η of semi-aromatic polyamide with a concentration of 10 mg / ml in 98% concentrated sulfuric acid at 25℃±0.01℃. r ; (3) Test method for free diamine content in semi-aromatic polyamide resin: Weigh 10.0g of semi-aromatic polyamide resin and test the free diamine content using a gas chromatography-headspace coupling device. The headspace temperature is 150℃ and the temperature is kept constant for 2h. Then, the content is detected by gas chromatography.

[0070] (4) The whiteness value of polyamide resin was measured by injection molding the polyamide resin into a color sample and then testing the color using a LIBERO X-rite color-Eye 7000A colorimeter. The measured Ganz whiteness value is represented by WI.

[0071] The test results of the polyamide resins in the examples and comparative examples are shown in Table 1.

[0072] As shown in Table 1, compared to Examples 1-7 and Comparative Example 1, the resins in the examples all have very low free diamine content and excellent color, with Ganz whiteness between 70 and 76 (a Ganz whiteness above 70 is considered good for semi-aromatic polyamide resins). In contrast, the resin in Comparative Example 1 not only has a higher free diamine content but also a Ganz whiteness of only 48, indicating that the process of the present invention can effectively reduce the free diamine content in the resin and improve its color. Comparing Examples 3 and Comparative Examples 3-4, using acetone and ethyl acetate cannot effectively reduce the free diamine content in the resin, and the resin's color is also poor. Comparative Example 3 used a large amount of ethanol, which effectively reduced the free diamine content in the resin, but the resin viscosity also decreased significantly, rendering it unusable. Similarly, in Comparative Examples 4 and 5, using acetone and ethyl acetate also reduced the resin viscosity to some extent, significantly affecting the resin's performance. Therefore, this application demonstrates that the process can not only remove the content of free diamine in the resin and improve the color of the resin, but also ensure the viscosity of the resin and improve the processing performance of the resin.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a polyamide resin with low free diamine content, characterized in that, include: The polyamide resin obtained after solid-phase thickening was extracted with alcohol.

2. The method according to claim 1, characterized in that, The alcohol includes at least one of methanol, ethanol, and propanol, with ethanol being preferred.

3. The method according to claim 1 or 2, characterized in that, The mass ratio of the polyamide resin to the alcohol is 1:(2-10), preferably 1:(4-9).

4. The method according to claim 1 or 2, characterized in that, The extraction temperature is 70℃~150℃, and the extraction time is 2h~4h.

5. The method according to claim 1 or 2, characterized in that, The polyamide resin includes semi-aromatic polyamide resin.

6. The method according to claim 5, characterized in that, The semi-aromatic polyamide resin is composed of the following repeating units: (a) terephthalic acid or its derivatives, and optionally one or more other aromatic or aliphatic diacids; (b) One or more aliphatic diamines having 10 to 20 carbon atoms, and optionally one or more aliphatic diamines having 4 to 9 carbon atoms; (c) Optionally one or more aminocarboxylic acids and / or lactams; Of which, terephthalic acid or its derivatives account for 50 to 100 mol% of the total of (a), one or more aliphatic diamines having 10 to 20 carbon atoms account for 50 to 100 mol% of the total of (b), and one or more aminocarboxylic acids and / or lactams account for 0 to 25 mol% of the total of (a) + (b) + (c).

7. A polyamide resin with low free diamine content, characterized in that, It is prepared by any one of the methods described in claims 1-6.

8. The polyamide resin according to claim 7, characterized in that, The content of free diamine in the polyamide resin is not higher than 100 ppm; And / or, the Gannz whiteness of the polyamide resin is 70-76; And / or, at 25°C, the relative viscosity of the polyamide resin is 1.85 to 2.8, preferably 2.0 to 2.

45.

9. A polyamide molding composition, characterized in that, Including the polyamide resin with low free diamine content as described in claim 7 or 8; Preferably, based on the total mass of the polyamide molding composition, the mass percentage of the polyamide resin with low free diamine content is 30-95%.

10. A molded article, characterized in that, It is prepared using the polyamide molding composition of claim 9.

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