A modified engineering plastic based on PPA and a preparation method thereof

Abstract

The application discloses a modified engineering plastic based on PPA and a preparation method thereof in the field of engineering plastics, and comprises the following components in parts by weight: polyamide 66 salt 50-60 parts, polyamide 6T salt 20-30 parts, polyamide 6I salt 12-20 parts, flame-retardant polyurethane prepolymer 5-10 parts, and toughening agent 3-8 parts. The application solves the low-temperature brittleness problem of traditional PPA through the introduction of flexible chain segments and micro-crosslinking regulation, and meanwhile, high strength is maintained; the introduction of phosphine hetero-phenyl groups enables the material to achieve high-grade flame retardation, and additional flame retardant does not need to be added, thereby avoiding the negative influence on the mechanical properties; the synergistic effect of the semi-aromatic structure and the micro-crosslinking network can meet the high-temperature working condition requirement; the step-by-step polymerization controls the molecular weight distribution; the tackifying process adjusts the melt viscosity; the processing such as drawing and pelletizing is facilitated; and the application is suitable for injection molding.

Description

Technical Field

[0001] This invention belongs to the field of engineering plastics technology, specifically referring to a modified engineering plastic based on PPA and its preparation method. Background Technology

[0002] Polyphthalamide (PPA) is a semi-aromatic polyamide produced by the polycondensation reaction of phthalic acid with aliphatic or alicyclic diamines. The alternating aromatic rings and aliphatic segments in its molecular chain give the material a unique balance of properties. PPA belongs to the high-temperature nylon family and can be classified into types such as PA6T, PA9T, and PA10T according to the type of diamine. Among them, PA6T (produced by copolymerization of hexamethylenediamine and phthalic acid) is the most common commercial variety.

[0003] The chemical structure of PPA determines its excellent thermal stability. The melting point of semi-crystalline PPA is usually between 300-325℃, the glass transition temperature (Tg) is about 120-150℃, the heat distortion temperature (HDT) can reach more than 300℃ (0.45MPa load), and the continuous use temperature is as high as 170℃. This high temperature performance makes it significantly better than traditional nylon (such as PA66 with an HDT of about 100-120℃), close to polyphenylene sulfide (PPS) and polyether ether ketone (PEEK), but the cost is only 1 / 3 to 1 / 2 of the latter.

[0004] PPA is primarily used in the following technological fields: Automotive Industry: For example, powertrain components such as water pump impellers, oil filter housings, and turbocharger brackets, which need to withstand high temperatures of 150-200℃ and lubricant corrosion; cooling systems such as thermostat housings, radiator water chambers, and cooling pipes, where BASF's hydrolysis-resistant PPA extends lifespan by more than three times; new energy vehicles: high-voltage connectors, electric drive housings, and charging interfaces in the three-electric system (battery, motor, and electronic control), requiring materials that are both flame-retardant (UL94V-0) and track-resistant (CTI≥600V). Industrial and Aerospace: For example, fluid transportation such as natural gas pipelines and chemical pumps, utilizing its high-pressure resistance (15MPa burst pressure) and corrosion resistance; and aerospace components such as aircraft interior parts and engine compartment seals, where PPA's lightweight (40% weight reduction) and weather resistance meet aerospace standards.

[0005] The core performance advantages of PPA include the following: High strength and rigidity: 30% glass fiber reinforced PPA has a tensile strength of up to 180 MPa and a flexural modulus of 9800 MPa, far exceeding PA66 (tensile strength of approximately 120 MPa when 30% glass fiber reinforced). Its rigidity is comparable to aluminum alloy, but its density is only 1.43 g / cm³, enabling lightweight replacement of metal parts; Low water absorption and dimensional stability: PPA has a water absorption rate of only 6% at 23℃ and 100% humidity, far lower than PA66's 8.9%, and its dimensional change rate after moisture absorption is less than... With a purity of 1%, this characteristic allows it to maintain stable mechanical properties and electrical insulation even in humid environments, making it particularly suitable for applications requiring high precision, such as automotive sensor housings and electrical connectors. Chemical resistance: PPA exhibits extremely strong resistance to fuels, lubricants, and coolants (ethylene glycol / water mixtures), making it a preferred material for cooling system components in new energy vehicles due to its resistance to alcoholysis. Processing adaptability: PPA can be processed using traditional methods such as injection molding and extrusion. Its melt temperature is 324-343℃, and the mold temperature needs to be controlled above 135℃ to ensure crystallinity.

[0006] Technical limitations and modification requirements of PPA: Insufficient toughness: The notched impact strength of unmodified PPA is only 110 J / m, lower than that of Nylon 66 (200 J / m), making it prone to brittle fracture. Poor flame retardancy: Pure PPA only has an HB flame retardancy rating, requiring the addition of halogen-free flame retardants (such as aluminum diethylphosphinate) to achieve UL94V-0. Processing difficulty: High melt viscosity leads to high injection pressure, requiring a dedicated screw design and strict mold temperature control. Hydrolytic aging: Long-term contact with coolant or high-temperature and high-humidity environments can cause amide bond breakage, resulting in decreased mechanical properties. High-temperature oxidation: Long-term use above 200℃ can trigger thermal oxidative degradation, requiring the addition of antioxidants (such as a combination of 1010 and 168) to stabilize the molecular chain. Summary of the Invention

[0007] To address the above issues and overcome the shortcomings of existing technologies, this invention provides a modified engineering plastic based on PPA and its preparation method. This invention solves the low-temperature brittleness problem of traditional PPA by introducing flexible segments and controlling micro-crosslinking, while maintaining high strength. The introduction of phosphenanthrene groups enables the material to achieve a high level of flame retardancy, eliminating the need for additional flame retardants and avoiding negative impacts on mechanical properties. The synergistic effect of the semi-aromatic structure and micro-crosslinking network meets the requirements of high-temperature operating conditions. Stepwise polymerization controls molecular weight distribution, and the thickening process adjusts melt viscosity, facilitating processing such as strip making and pelletizing, making it suitable for injection molding.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention proposes a modified engineering plastic based on PPA, wherein the modified engineering plastic comprises the following components in parts by weight: 50-60 parts of polyamide 66 salt, 20-30 parts of polyamide 6T salt, 12-20 parts of polyamide 6I salt, 5-10 parts of flame retardant polyurethane prepolymer, and 3-8 parts of toughening agent.

[0009] Preferably, the modified engineering plastic further includes an initiator, the content of which is 0.4%-0.6% of the modified engineering plastic;

[0010] Preferably, the initiator is composed of di-tert-butyl peroxide (DTBP) and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane (DBPH) in a ratio of 1:1 to 1:2;

[0011] Preferably, the preparation method of the flame-retardant polyurethane prepolymer specifically includes the following steps:

[0012] A1. Allylphosphine(9,10-dihydro-9-oxa-10-allylphosphine-10-oxide) was dissolved in dry toluene. Flowing nitrogen gas was introduced, and diethanolamine was slowly added to the reaction system. After mixing evenly, the reaction temperature was increased to carry out a nucleophilic addition reaction. After the reaction was completed, the mixture was cooled, washed with deionized water, and the organic phase was collected to remove water. Excess reaction solvent was removed by vacuum distillation. After purification and drying, product 1 was obtained.

[0013] Preferably, in step A1, the mass ratio of allylphosphine to diethanolamine is 2-2.3:1;

[0014] Preferably, in step A1, the reaction temperature of the nucleophilic addition reaction is 80-100℃, and the reaction time is 4-6h;

[0015] A2. Dissolve product 1 prepared in step A1 in DMF, introduce flowing nitrogen gas, add dibutyltin dilaurate, mix well, add diisocyanate compound dropwise, raise the reaction temperature to carry out prepolymerization reaction, cool after the reaction is completed, and obtain flame retardant polyurethane prepolymer.

[0016] Preferably, the mass ratio of diethanolamine to diisocyanate compound is 1.2-1.6:1.2-1.8;

[0017] Preferably, in step A2, the diisocyanate compound includes any one of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate;

[0018] Preferably, in step A2, the mass of the catalyst added is 0.4%-0.6% of the mass of the diisocyanate compound;

[0019] Preferably, in step A2, the catalyst is at least one of dibutyltin dilaurate and stannous octoate;

[0020] Preferably, in step A2, the reaction temperature of the prepolymerization reaction is 60-70°C, and the reaction time of the prepolymerization reaction is 2-4 hours;

[0021] This invention also provides a method for preparing PPA-based modified engineering plastics, specifically including the following steps:

[0022] S1. Dissolve glycerol triglycidyl ether in DMF, purge with flowing nitrogen, add maleic anhydride dropwise, mix well, add catalyst and hydroquinone, raise the reaction temperature for pre-reaction, after the reaction is complete, continue to raise the temperature for branching polymerization reaction, after the reaction is complete, cool, add anhydrous methanol to quench the reaction, remove the reaction solvent by vacuum distillation, and after drying, obtain toughening agent.

[0023] Preferably, in step S1, the mass ratio between glycerol triglycidyl ether and maleic anhydride is 1:1.35-1.70;

[0024] Preferably, in step S1, the catalyst comprises at least one of triethylamine, 1,8-diazabicycloundec-7-ene (DBU), and boron trifluoride diethyl ether complex;

[0025] Preferably, in step S1, the mass of the catalyst added is 1%-2% of the total mass of the reactants;

[0026] Preferably, in step S1, the mass of hydroquinone added is 0.2%-0.4% of the mass of maleic anhydride;

[0027] Preferably, in step S1, the reaction temperature of the pre-reaction is 80-100℃, and the reaction time of the pre-reaction is 1-2 hours;

[0028] Preferably, in step S1, the reaction temperature of the branching polymerization reaction is 120-140℃, and the reaction time of the branching polymerization reaction is 2-4h;

[0029] S2. Place polyamide 66 salt, polyamide 6T salt and polyamide 6I salt in a polymerization reactor, add deionized water, stir until the reactants are completely dissolved, add benzoic acid and sodium hypophosphite, stir and mix evenly, then introduce flowing nitrogen gas, raise the reaction temperature to 220-230℃, and adjust the pressure inside the polymerization reactor to 2.5MPa. Open the exhaust valve to release water vapor, exhaust for 30-40 minutes. After exhaust, add flame-retardant polyurethane prepolymer into the polymerization reactor, and maintain constant temperature and pressure to carry out the first-stage polymerization reaction.

[0030] Preferably, in step S2, the mass-to-volume ratio of the polyamide 66 salt to deionized water is 0.5-0.6 g / mL;

[0031] Preferably, in step S2, the mass of benzoic acid added is 1.3%-1.9% of the mass of polyamide 66 salt;

[0032] Preferably, in step S2, the added mass of sodium hypophosphite is 1.0%-1.2% of the mass of polyamide 66 salt;

[0033] Preferably, in step S2, the reaction temperature of the primary polymerization reaction is 220-230℃, the reaction time of the primary polymerization reaction is 1-2h, and the pressure inside the reactor of the primary polymerization reaction is maintained between 2.3-2.5MPa;

[0034] S3. After the first-stage polymerization reaction in step S2 is completed, the reaction temperature is increased to carry out the second-stage polymerization reaction.

[0035] Preferably, in step S3, the reaction temperature of the secondary polymerization reaction is 275-285℃, the reaction time of the secondary polymerization reaction is 1.5-2.5h, and the pressure inside the reactor of the secondary polymerization reaction is maintained between 2.3-2.5MPa;

[0036] After the secondary polymerization reaction in step S4 and S3 is completed, the toughening agent prepared in step S1 is dissolved in N-methylpyrrolidone (NMP) and injected into the polymerization reactor. Mixing is carried out under constant temperature and pressure conditions, maintaining the temperature at 270-280℃ and the pressure inside the reactor at 2.3-2.5MPa. After mixing for 0.5-1h, the pressure inside the polymerization reactor is reduced to 0.5MPa, the reaction temperature is increased, and an initiator is added to the reaction system to carry out the micro-crosslinking reaction.

[0037] Preferably, in step S4, the toughening agent has a mass concentration of 0.12-0.20 g / mL in N-methylpyrrolidone;

[0038] Preferably, in step S4, the reaction temperature of the micro-crosslinking reaction is 290-300℃, and the reaction time of the micro-crosslinking reaction is 40-60 min;

[0039] After the micro-crosslinking reaction in step S5 and S4 is completed, the reaction temperature is raised to 310-320℃. Under vacuum conditions, a thickening reaction is carried out. After the reaction lasts for 1-1.5 hours, high-pressure nitrogen is introduced to press the molten material out from the bottom outlet of the reactor. After water cooling, stripping, pelletizing, and vacuum drying, modified engineering plastic is obtained.

[0040] The beneficial effects achieved by this invention are as follows:

[0041] This invention provides a modified engineering plastic based on PPA and its preparation method. By introducing flexible segments and controlling micro-crosslinking, this invention solves the problem of low-temperature brittleness of traditional PPA while maintaining high strength. The introduction of phosphenanthrene groups enables the material to achieve a high level of flame retardancy without the need for additional flame retardants, thus avoiding negative impacts on mechanical properties. The synergistic effect of the semi-aromatic structure and micro-crosslinking network can meet the requirements of high-temperature working conditions. Stepwise polymerization controls the molecular weight distribution, and the thickening process adjusts the melt viscosity, facilitating processing such as strip drawing and pelletizing, and making it suitable for injection molding. In this invention, allyl phosphonophenanthrene (containing a phosphonophenanthrene flame-retardant group and an allyl double bond) undergoes a nucleophilic addition reaction with diethanolamine (containing an active amino group). The amino group (-NH2) of diethanolamine acts as a nucleophile, attacking the allyl double bond (the carbon with a lower electron cloud density) to form a new CN bond, generating product 1 containing a phosphonophenanthrene group and two hydroxyl groups (-OH, from diethanolamine). This reaction introduces a flame-retardant core (phosphonophenanthrene) and an active site (hydroxyl group) for polyurethane prepolymerization. Then, under the action of a catalyst, it undergoes a polyurethane prepolymerization reaction with diisocyanate compounds. -NCO and -OH add to form a urethane bond (-NH-CO-O-), generating a polyurethane prepolymer with a main chain containing urethane bonds and side chains or terminals containing phosphonophenanthrene flame-retardant groups, possessing both flexible chain segments (urethane bonds are easily rotated) and flame-retardant function. In this invention, glycerol triglycidyl ether reacts with maleic anhydride to undergo an epoxy- The anhydride ring-opening reaction and branching polymerization: Under the action of an alkaline catalyst, the anhydride group of maleic anhydride undergoes ring-opening with the epoxy group to generate ester group (-COO-) and hydroxyl group (-OH), forming an oligomeric intermediate containing multiple active groups. Hydroquinone acts as a polymerization inhibitor, suppressing the free radical homopolymerization of the maleic anhydride double bond. The hydroxyl group of the intermediate undergoes esterification with the remaining anhydride group, or the hydroxyl group further ring-opens with the unreacted epoxy group, forming a branched structure through multi-arm extension. The final product is a hyperbranched toughening agent containing multiple hydroxyl and ester groups. The multi-reactive sites of the toughening agent coexist with the polyamide matrix. The grafted structure of polyurethane prepolymer and polyamide reduces phase separation, ensuring the synergistic effect of flexible segments and rigid matrix. This avoids the decrease in toughness caused by interfacial debonding at low temperatures. The local network formed by moderate micro-crosslinking can not only limit excessive slippage of molecular chains, but also disperse impact stress to a larger area through the network, preventing rapid crack propagation. The urethane bonds (easily rotatable) of flame-retardant polyurethane prepolymer and the branched flexible segments of toughening agent can still maintain a certain degree of mobility at low temperatures, which can absorb external impact energy (such as brittle fracture stress at low temperatures) and alleviate stress concentration. Attached Figure Description

[0042] Figure 1 The tensile properties of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-3 of this invention are shown in the figure.

[0043] Figure 2The graph shows the bending performance results of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0044] Figure 3 The graph shows the impact performance results of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0045] Figure 4 The graph shows the flame retardant performance results of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0046] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0050] The sources of the raw materials involved in this invention are as follows:

[0051] Polyamide 66 salt was prepared using conventional techniques. The specific method was as follows: Deionized water was heated to 50°C, and under a nitrogen atmosphere, adipic acid was added and stirred until completely dissolved. Then, an equimolar amount of hexamethylenediamine was slowly added, and the system temperature was controlled to not exceed 70°C. The mixture was stirred for 60 minutes to allow a neutralization reaction to occur. The reaction solution was then slowly cooled to 20-30°C, and polyamide 66 salt precipitated as white crystals. After filtration, the solution was washed twice with cold ethanol (or ice water) and dried under vacuum at 80°C for 4 hours to obtain PA66 salt with a purity ≥99.5%.

[0052] Polyamide 6T salt was prepared using conventional techniques. Specifically, deionized water and methanol were mixed at a volume ratio of 3:1 and heated to 80°C. Terephthalic acid was added and stirred until a suspension was formed. Under nitrogen protection, an equimolar amount of hexamethylenediamine was slowly added, the temperature was raised to 90°C, and the mixture was stirred for 1 hour until the terephthalic acid was completely dissolved. The reaction solution was then cooled to room temperature with stirring. PA6T salt precipitated as a white powder crystal. After filtration, the crystals were washed twice with methanol and dried under vacuum at 100°C for 6 hours to obtain polyamide 6T salt.

[0053] Polyamide 6I salt was prepared using conventional techniques. The specific method was as follows: deionized water was heated to 80°C, isophthalic acid was added, and the mixture was stirred to form a suspension. Under nitrogen protection, an equimolar amount of hexamethylenediamine was added dropwise, the temperature was raised to 90°C, and the mixture was stirred for 1 hour until the system became clear. The reaction solution was then naturally cooled to 40°C, and polyamide 6I salt crystallized out. After filtration, the crystals were washed twice with hot water at 60°C and dried under vacuum at 80°C for 6 hours to obtain polyamide 6I salt.

[0054] Example 1

[0055] This embodiment proposes a PPA-based modified engineering plastic, which comprises the following components in parts by weight: 50 parts of polyamide 66 salt, 30 parts of polyamide 6T salt, 12 parts of polyamide 6I salt, 5 parts of flame-retardant polyurethane prepolymer, and 3 parts of toughening agent; the modified engineering plastic also includes an initiator, the content of which is 0.4% of the modified engineering plastic.

[0056] The preparation method of flame-retardant polyurethane prepolymer specifically includes the following steps:

[0057] A1. Accurately weigh 2.5g of allylphosphine and place it in a flask. After completely removing oxygen from the reaction system by purging with nitrogen, add 80mL of anhydrous toluene to completely dissolve allylphosphine. Dissolve 1.1g of diethanolamine in 20mL of anhydrous toluene and add it dropwise to the reaction system at a rate of 1mL / min. After the addition is complete, raise the reaction temperature to 80℃ to carry out the nucleophilic addition reaction. After the reaction is completed, let the reaction system cool to room temperature, add deionized water to the reaction system and wash repeatedly. After collecting the organic phase, add anhydrous magnesium sulfate to dry the organic phase. Remove excess reaction solvent by vacuum distillation, purify and dry to obtain product 1.

[0058] A2. Take product 1 prepared in step A1 and place it in a flask. Add 20 mL of DMF to completely dissolve product 1. Then add 18 mg of dibutyltin dilaurate and mix well. Raise the temperature to 60°C. Dissolve 3.0 g of isophorone dicyanate in 10 mL of DMF and add it dropwise to the reaction system at a rate of 0.1 mL / mL. After the addition is complete, maintain the reaction temperature at 60°C for prepolymerization reaction for 2.5 h. After the reaction is completed, let the reaction system cool to room temperature to obtain flame-retardant polyurethane prepolymer.

[0059] This embodiment also provides a method for preparing PPA-based modified engineering plastics, specifically including the following steps:

[0060] S1. Accurately weigh 5.0 g of glycerol triglycidyl ether and place it in a flask. Add 20 mL of LDM to completely dissolve it. Then, purge the oxygen in the reaction system with flowing nitrogen. Add 8.5 g of maleic anhydride dropwise to the reaction system at a rate of 0.1 mL / min. After the addition is complete, mix evenly at a rate of 300 rpm. Add 0.27 g of triethylamine and 34 mg of hydroquinone. Raise the reaction temperature to 80 °C for pre-reaction. After reacting for 2 h, continue to raise the reaction temperature to 120 °C for branching polymerization. After the reaction is completed, wait for the reaction system to cool to room temperature. Add anhydrous methanol to quench the reaction. Remove the reaction solvent by vacuum distillation. After vacuum drying at 40 °C for 4 h, the toughening agent is obtained.

[0061] S2. Place 20g of polyamide 66 salt, 12g of polyamide 6T salt, and 6.8g of polyamide 6I salt into a polymerization reactor. Add 40mL of deionized water and stir at 500rpm until the reactants are completely dissolved. Add 0.38g of benzoic acid and 0.2g of sodium hypophosphite. After stirring and mixing evenly, introduce flowing nitrogen gas to raise the reaction temperature to 230℃ and adjust the pressure inside the polymerization reactor to 2.35MPa. Open the exhaust valve to release water vapor and exhaust for 30min. After exhaust, add 2g of flame-retardant polyurethane prepolymer into the polymerization reactor. Maintain the temperature at 230℃ and the pressure at 2.35MPa and carry out the first-stage polymerization reaction under constant temperature and pressure for 1h.

[0062] After the first-stage polymerization reaction in step S2 is completed, the reaction temperature is raised to 280℃ to carry out the second-stage polymerization reaction, while maintaining the pressure inside the reactor at 2.35MPa for 2 hours.

[0063] After the secondary polymerization reaction in step S4 and S3 is completed, 1.2g of the toughening agent prepared in step S1 is dissolved in 10mL of NMP and injected into the polymerization reactor. The temperature is maintained at 275℃ and the pressure inside the reactor is 2.35MPa. Mixing is carried out under constant temperature and pressure conditions. After mixing for 1 hour, the pressure inside the polymerization reactor is reduced to 0.5MPa and the reaction temperature is increased to 290℃. 0.25g of initiator (DTBP:DBPH=1.5:1) is added to the reaction system to carry out micro-crosslinking reaction for 60 minutes.

[0064] After the micro-crosslinking reaction in step S5 and S4 is completed, the reaction temperature is raised to 315℃. Under vacuum conditions, a thickening reaction is carried out. After 1 hour of reaction, high-pressure nitrogen is introduced to press the molten material out from the bottom outlet of the reactor. After water cooling, stripping, pelletizing, and vacuum drying, modified engineering plastic is obtained.

[0065] Example 2

[0066] This embodiment proposes a modified engineering plastic based on PPA, which comprises the following components in parts by weight: 55 parts of polyamide 66 salt, 20 parts of polyamide 6T salt, 20 parts of polyamide 6I salt, 8 parts of flame-retardant polyurethane prepolymer, and 5 parts of toughening agent.

[0067] The modified engineering plastic also includes an initiator, the initiator being present in an amount of 0.5% of the modified engineering plastic.

[0068] The preparation method of flame-retardant polyurethane prepolymer specifically includes the following steps:

[0069] A1. Accurately weigh 3.0 g of allylphosphine and place it in a flask. After completely removing oxygen from the reaction system by purging with nitrogen, add 80 mL of anhydrous toluene to completely dissolve allylphosphine. Dissolve 1.5 g of diethanolamine in 20 mL of anhydrous toluene and add it dropwise to the reaction system at a rate of 1 mL / min. After the addition is complete, raise the reaction temperature to 90 °C to carry out the nucleophilic addition reaction. After the reaction is completed, let the reaction system cool to room temperature, add deionized water to the reaction system and wash repeatedly. After collecting the organic phase, add anhydrous magnesium sulfate to dry the organic phase. Remove excess reaction solvent by vacuum distillation, purify and dry to obtain product 1.

[0070] A2. Take product 1 prepared in step A1 and place it in a flask. Add 20 mL of DMF to completely dissolve product 1. Then add 14 mg of stannous octoate and mix well. Raise the temperature to 60°C. Dissolve 3.5 g of toluene diisocyanate in 10 mL of DMF and add it dropwise to the reaction system at a rate of 0.1 mL / mL. After the addition is complete, maintain the reaction temperature at 60°C for the prepolymerization reaction for 2.5 h. After the reaction is completed, allow the reaction system to cool to room temperature to obtain the flame-retardant polyurethane prepolymer.

[0071] This invention also provides a method for preparing PPA-based modified engineering plastics, specifically including the following steps:

[0072] S1. Accurately weigh 6.0 g of glycerol triglycidyl ether and place it in a flask. Add 20 mL of LDM to completely dissolve it. Then, purge the oxygen in the reaction system with flowing nitrogen. Add 9.0 g of maleic anhydride dropwise to the reaction system at a rate of 0.1 mL / min. After the addition is complete, mix evenly at a rate of 300 rpm. Add 0.15 g of triethylamine and 27 mg of hydroquinone. Raise the reaction temperature to 80 °C for pre-reaction. After reacting for 2 h, continue to raise the reaction temperature to 120 °C for branching polymerization. After the reaction is completed, wait for the reaction system to cool to room temperature. Add anhydrous methanol to quench the reaction. Remove the reaction solvent by vacuum distillation. After drying under vacuum at 40 °C for 4 h, the toughening agent is obtained.

[0073] S2. Place 25g of polyamide 66 salt, 9g of polyamide 6T salt, and 9g of polyamide 6I salt into a polymerization reactor. Add 45mL of deionized water and stir at 500rpm until the reactants are completely dissolved. Add 0.35g of benzoic acid and 0.3g of sodium hypophosphite. After stirring and mixing evenly, introduce flowing nitrogen gas to raise the reaction temperature to 220℃ and adjust the pressure inside the polymerization reactor to 2.5MPa. Open the exhaust valve to release water vapor and exhaust for 30min. After exhaust, add 3.6g of flame-retardant polyurethane prepolymer into the polymerization reactor. Maintain the temperature at 220℃ and the pressure at 2.5MPa, and carry out the first-stage polymerization reaction under constant temperature and pressure for 2h.

[0074] After the first-stage polymerization reaction in step S2 is completed, the reaction temperature is increased to 285℃ to carry out the second-stage polymerization reaction, while maintaining the pressure inside the reactor at 2.5MPa for 1.5h.

[0075] After the secondary polymerization reaction in step S4 and S3 is completed, 2.3g of the toughening agent prepared in step S1 is dissolved in 15mL of NMP and injected into the polymerization reactor. The temperature is maintained at 280℃ and the pressure inside the reactor is 2.5MPa. Mixing is carried out under constant temperature and pressure conditions. After mixing for 0.5h, the pressure inside the polymerization reactor is reduced to 0.5MPa, the reaction temperature is increased to 300℃, and 0.26g of initiator (DTBP:DBPH=2:1) ​​is added to the reaction system to carry out micro-crosslinking reaction for 40min.

[0076] After the micro-crosslinking reaction in step S5 and S4 is completed, the reaction temperature is raised to 320℃. Under vacuum conditions, a thickening reaction is carried out. After 1 hour of reaction, high-pressure nitrogen is introduced to press the molten material out from the bottom outlet of the reactor. After water cooling, stripping, pelletizing, and vacuum drying, modified engineering plastic is obtained.

[0077] Example 3

[0078] This embodiment proposes a modified engineering plastic based on PPA, which comprises the following components in parts by weight: 60 parts of polyamide 66 salt, 20 parts of polyamide 6T salt, 20 parts of polyamide 6I salt, 10 parts of flame-retardant polyurethane prepolymer, and 8 parts of toughening agent.

[0079] The modified engineering plastic also includes an initiator, the initiator being present in an amount of 0.6% of the modified engineering plastic.

[0080] The preparation method of flame-retardant polyurethane prepolymer specifically includes the following steps:

[0081] A1. Accurately weigh 3.5g of allylphosphine and place it in a flask. After completely removing oxygen from the reaction system by purging with nitrogen, add 80mL of anhydrous toluene to completely dissolve allylphosphine. Dissolve 1.6g of diethanolamine in 20mL of anhydrous toluene and add it dropwise to the reaction system at a rate of 1mL / min. After the addition is complete, raise the reaction temperature to 100℃ to carry out the nucleophilic addition reaction. After the reaction is completed, let the reaction system cool to room temperature, add deionized water to the reaction system and wash repeatedly. After collecting the organic phase, add anhydrous magnesium sulfate to dry the organic phase. Remove excess reaction solvent by vacuum distillation, purify and dry to obtain product 1.

[0082] A2. Take product 1 prepared in step A1 and place it in a flask. Add 20 mL of DMF to completely dissolve product 1. Then add 20 mg of dibutyltin dilaurate and mix well. Raise the temperature to 60 °C. Dissolve 4.5 g of diphenylmethane diisocyanate in 10 mL of DMF and add it dropwise to the reaction system at a rate of 0.1 mL / mL. After the addition is complete, maintain the reaction temperature at 60 °C for prepolymerization reaction for 2.5 h. After the reaction is completed, let the reaction system cool to room temperature to obtain flame-retardant polyurethane prepolymer.

[0083] This invention also provides a method for preparing PPA-based modified engineering plastics, specifically including the following steps:

[0084] S1. Accurately weigh 7.0 g of glycerol triglycidyl ether and place it in a flask. Add 20 mL of LDM to completely dissolve it. Then, purge the oxygen in the reaction system with flowing nitrogen. Add 9.5 g of maleic anhydride dropwise to the reaction system at a rate of 0.1 mL / min. After the addition is complete, mix evenly at a rate of 300 rpm. Add 0.20 g of triethylamine and 19 mg of hydroquinone. Raise the reaction temperature to 80 °C for pre-reaction. After reacting for 2 h, continue to raise the reaction temperature to 120 °C for branching polymerization. After the reaction is completed, wait for the reaction system to cool to room temperature. Add anhydrous methanol to quench the reaction. Remove the reaction solvent by vacuum distillation. After vacuum drying at 40 °C for 4 h, the toughening agent is obtained.

[0085] S2. Place 30g of polyamide 66 salt, 10g of polyamide 6T salt, and 6.0g of polyamide 6I salt into a polymerization reactor. Add 50mL of deionized water and stir at 500rpm until the reactants are completely dissolved. Add 0.4g of benzoic acid and 0.3g of sodium hypophosphite. After stirring and mixing evenly, introduce flowing nitrogen gas to raise the reaction temperature to 225℃ and adjust the pressure inside the polymerization reactor to 2.0MPa. Open the exhaust valve to release water vapor and exhaust for 40min. After exhaust, add 5g of flame-retardant polyurethane prepolymer into the polymerization reactor. Maintain the temperature at 225℃ and the pressure at 2.4MPa and carry out the first-stage polymerization reaction under constant temperature and pressure for 1.5h.

[0086] After the first-stage polymerization reaction in step S2 is completed, the reaction temperature is increased to 275℃ to carry out the second-stage polymerization reaction, while maintaining the pressure inside the reactor at 2.4MPa for 2.5h.

[0087] After the secondary polymerization reaction in step S4 and S3 is completed, 4.0 g of the toughening agent prepared in step S1 is dissolved in 20 mL of NMP and injected into the polymerization reactor. The temperature is maintained at 270 °C and the pressure inside the reactor is 2.4 MPa. Mixing is carried out under constant temperature and pressure conditions. After mixing for 1 h, the pressure inside the polymerization reactor is reduced to 0.5 MPa and the reaction temperature is increased to 295 °C. 0.22 g of initiator (DTBP:DBPH=1:1) is added to the reaction system to carry out micro-crosslinking reaction for 50 min.

[0088] After the micro-crosslinking reaction in step S5 and S4 is completed, the reaction temperature is raised to 310℃. Under vacuum conditions, a thickening reaction is carried out. After 1.5 hours of reaction, high-pressure nitrogen is introduced to press the molten material out from the bottom outlet of the reactor. After water cooling, stripping, pelletizing, and vacuum drying, modified engineering plastic is obtained.

[0089] Comparative Example 1

[0090] This comparative example provides a modified engineering plastic and its preparation method. The only difference between this and Example 1 is that all components do not contain toughening agents and initiators, while the remaining components and their contents are the same as in Example 1.

[0091] Comparative Example 2

[0092] This comparative example provides a modified engineering plastic and its preparation method. The only difference between this example and Example 1 is that it does not contain an initiator in any of the components, while the other components and their contents are the same as in Example 1.

[0093] Comparative Example 3

[0094] This comparative example provides a modified engineering plastic and its preparation method. The only difference between this example and Example 1 is that it does not contain flame-retardant polyurethane prepolymer in any of the components. The other components and their contents are the same as in Example 1.

[0095] Comparative Example 4

[0096] This comparative example provides a modified engineering plastic and its preparation method. The only difference between this example and Example 1 is that the preparation method of the flame-retardant polyurethane prepolymer does not include step A1, and product 1 in step A2 is replaced with diethanolamine in the same molar ratio. The remaining components and component contents are the same as in Example 1.

[0097] Experimental Example 1

[0098] This experiment tests the mechanical properties of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-3:

[0099] 1. In accordance with GB / T 1040-2022, tensile properties were tested using a CMT-4204 electronic universal testing machine, with the tensile rate set to 55 mm / min;

[0100] 2. According to GB / T 9341-2008, use the CMT-4204 electronic universal testing machine to test the bending strength and bending modulus, and set the speed to 2 mm / min;

[0101] 3. In accordance with GB / T 1843-2008, use the ZBC8400-B pendulum impact testing machine to test the unnotched / notched impact strength. The pendulum energy for the notched impact strength test is 2.75J.

[0102] Figure 1 The graph shows the tensile properties of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. Figure 2 The graphs show the bending properties of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. Figure 3The figures show the impact performance results of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. The modified engineering plastics prepared in Examples 1-3 of this invention reduce intermolecular interactions through the use of hyperbranched polymer toughening agents with soft chain segments and flame-retardant polyurethane prepolymers. However, a small number of crosslinking points are formed through micro-crosslinking reactions, which to some extent inhibits molecular chain slippage and compensates for some strength loss. The "softening" effect of the flexible chain segments and the "reinforcing" effect of micro-crosslinking are balanced, resulting in no significant change in tensile strength. Similarly, the change in flexural strength may also be insignificant. Tensile modulus reflects the rigidity of the material (its ability to resist elastic deformation) and is closely related to the rigidity of the molecular chains and their packing density. The flexible segments (such as ether bonds) of toughening agents have good chain mobility, which reduces the rigidity of the overall molecular chain. At the same time, the branched structure may disrupt the regularity of the polyamide molecular chain, reduce crystallinity, and further reduce rigidity. Similarly, the flexural modulus also decreases to varying degrees. However, it can be seen from the notched impact strength that the interfacial bonding between the toughening agent and the polyamide matrix (possibly through the formation of chemical bonds by reactive groups) can avoid phase separation during impact, ensure effective energy transfer, improve the interfacial adhesion between the toughening agent and the matrix, and prevent the toughening agent particles from falling off the matrix during impact (debonding will lead to interruption of energy transfer and reduction of toughness). The notched impact strength of the modified engineering plastics prepared in Examples 1-3 is significantly improved.

[0103] Experiment Example 2

[0104] This experiment tested the flame retardant properties of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-4. The test strips prepared in Examples 1-3 and Comparative Examples 1-4 were made into test strips with dimensions of 100mm×13mm×3.2mm by hot pressing molding process, and the tests were conducted on a ZNJF-3 limiting oxygen index tester in accordance with GB / T 2406-2015.

[0105] Figure 4 The figures show the flame retardant performance results of the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-4 of this invention. As shown in the figures, the modified engineering plastics prepared in Examples 1-3 and Comparative Examples 1-2 after flame retardant modification have significantly higher flame retardant performance.

[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0107] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A modified engineering plastic based on PPA, characterized in that: The modified engineering plastic comprises the following components in parts by weight: 50-60 parts of polyamide 66 salt, 20-30 parts of polyamide 6T salt, 12-20 parts of polyamide 6I salt, 5-10 parts of flame-retardant polyurethane prepolymer, and 3-8 parts of toughening agent; the modified engineering plastic further comprises an initiator, the content of which is 0.4%-0.6% of the modified engineering plastic; the initiator is composed of di-tert-butyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane in a ratio of 1:1 to 1:2; The preparation method of the flame-retardant polyurethane prepolymer specifically includes the following steps: A1. Allylphosphine phenanthrene was dissolved in dry toluene, and flowing nitrogen gas was introduced. Diethanolamine was slowly added to the reaction system and mixed evenly. The reaction temperature was increased to carry out a nucleophilic addition reaction. After the reaction was completed, the mixture was cooled, washed with deionized water, and the organic phase was collected to remove water. Excess reaction solvent was removed by vacuum distillation. After purification and drying, product 1 was obtained. A2. Dissolve product 1 prepared in step A1 in DMF, introduce flowing nitrogen gas, add dibutyltin dilaurate, mix well, add diisocyanate compound dropwise, raise the reaction temperature to carry out prepolymerization reaction, cool after the reaction is completed, and obtain flame retardant polyurethane prepolymer. The preparation method of the modified engineering plastic specifically includes the following steps: S1. Dissolve glycerol triglycidyl ether in DMF, purge with flowing nitrogen, add maleic anhydride dropwise, mix well, add catalyst and hydroquinone, raise the reaction temperature for pre-reaction, after the reaction is complete, continue to raise the temperature for branching polymerization reaction, after the reaction is complete, cool, add anhydrous methanol to quench the reaction, remove the reaction solvent by vacuum distillation, and after drying, obtain toughening agent. S2. Place polyamide 66 salt, polyamide 6T salt and polyamide 6I salt in a polymerization reactor, add deionized water, stir until the reactants are completely dissolved, add benzoic acid and sodium hypophosphite, stir and mix evenly, then introduce flowing nitrogen gas, raise the reaction temperature to 220-230℃, and adjust the pressure inside the polymerization reactor to 2.5MPa. Open the exhaust valve to release water vapor, exhaust for 30-40 minutes. After exhaust, add flame-retardant polyurethane prepolymer into the polymerization reactor, and maintain constant temperature and pressure to carry out the first-stage polymerization reaction. S3. After the first-stage polymerization reaction in step S2 is completed, the reaction temperature is increased to carry out the second-stage polymerization reaction. After the secondary polymerization reaction in step S4 and S3 is completed, the toughening agent prepared in step S1 is dissolved in N-methylpyrrolidone and injected into the polymerization reactor. Mixing is carried out under constant temperature and pressure conditions, maintaining the temperature at 270-280℃ and the pressure inside the reactor at 2.3-2.5MPa. After mixing for 0.5-1h, the pressure inside the polymerization reactor is reduced to 0.5MPa, the reaction temperature is increased, and an initiator is added to the reaction system to carry out the micro-crosslinking reaction. After the micro-crosslinking reaction in step S5 and S4 is completed, the reaction temperature is raised to 310-320℃. Under vacuum conditions, a thickening reaction is carried out. After the reaction lasts for 1-1.5 hours, high-pressure nitrogen is introduced to press the molten material out from the bottom outlet of the reactor. After water cooling, stripping, pelletizing, and vacuum drying, modified engineering plastic is obtained.

2. The PPA-based modified engineering plastic according to claim 1, characterized in that: In step A1, the mass ratio of allylphosphenanthrene to diethanolamine is 2-2.3:1; the reaction temperature of the nucleophilic addition reaction is 80-100℃, and the reaction time of the nucleophilic addition reaction is 4-6h.

3. The PPA-based modified engineering plastic according to claim 2, characterized in that: The mass ratio of the diethanolamine to the diisocyanate compound is 1.2-1.6:1.2-1.

8.

4. The PPA-based modified engineering plastic according to claim 3, characterized in that: In step A2, the diisocyanate compound includes any one of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate; the mass of the catalyst added is 0.4%-0.6% of the mass of the diisocyanate compound; the catalyst is at least one of dibutyltin dilaurate and stannous octoate; the reaction temperature of the prepolymerization reaction is 60-70℃, and the reaction time of the prepolymerization reaction is 2-4h.

5. A PPA-based modified engineering plastic according to claim 4, characterized in that: The mass ratio of glycerol triglycidyl ether to maleic anhydride is 1:1.35-1.70; the catalyst includes at least one of triethylamine, 1,8-diazabicycloundec-7-ene, and boron trifluoride diethyl ether complex; the mass of the catalyst added is 1%-2% of the total mass of the reactants; the mass of hydroquinone added is 0.2%-0.4% of the mass of maleic anhydride; the pre-reaction temperature is 80-100℃, and the pre-reaction time is 1-2h; the branching polymerization reaction temperature is 120-140℃, and the branching polymerization reaction time is 2-4h.

6. A PPA-based modified engineering plastic according to claim 5, characterized in that: In step S2, the mass-to-volume ratio of the polyamide 66 salt to deionized water is 0.5-0.6 g / mL; the added benzoic acid is 1.3%-1.9% of the mass of the polyamide 66 salt; the added sodium hypophosphite is 1.0%-1.2% of the mass of the polyamide 66 salt; the reaction temperature of the primary polymerization reaction is 220-230℃, the reaction time of the primary polymerization reaction is 1-2 h, and the pressure inside the reactor of the primary polymerization reaction is maintained between 2.3-2.5 MPa.

7. A PPA-based modified engineering plastic according to claim 6, characterized in that: In step S3, the reaction temperature of the secondary polymerization reaction is 275-285℃, the reaction time of the secondary polymerization reaction is 1.5-2.5h, and the pressure inside the reactor of the secondary polymerization reaction is maintained between 2.3-2.5MPa.

8. A PPA-based modified engineering plastic according to claim 7, characterized in that: In step S4, the toughening agent has a mass concentration of 0.12-0.20 g / mL in N-methylpyrrolidone; the reaction temperature of the micro-crosslinking reaction is 290-300℃, and the reaction time of the micro-crosslinking reaction is 40-60 min.

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