CN115873240B - High-multiplexing-rate nylon powder for 3D printing - Google Patents
High-multiplexing-rate nylon powder for 3D printing Download PDFInfo
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Abstract
The invention provides nylon powder for high-multiplexing-rate 3D printing. The nylon powder is endowed with strong molecular chain mobility and flexibility to the whole polyamide chain segment by introducing the functional aromatic hydroxyl-terminated polyether end-capping modifier, and the melt fluidity of the nylon powder can be effectively improved. The nylon powder can obviously improve the multiplexing rate, improve the surface roughness of the workpiece and enhance the toughness of the sintered workpiece.
Description
Technical Field
The invention belongs to the field of 3D printing resin, and particularly relates to nylon powder for 3D printing with high multiplexing rate.
Background
The 3D printing, namely the additive manufacturing technology, is a novel manufacturing and processing technology, changes the traditional material reduction manufacturing technology (cutting and processing technology) and is applied to the fields of industry, construction, medical treatment and the like. The Selective Laser Sintering (SLS) has the advantages of being rich in applicable material types, good in product performance and the like, becomes a hot spot in the field of 3D printing, and is applicable to most of consumable materials including polymeric materials and metal materials.
At present, the polymer powder material with wider application of the selective laser sintering material is nylon material, and has the advantages of good thermal stability, low melt viscosity, high strength, good compactness and the like of the sintered molding part, but the cost is higher, so that the consumable use cost can be reduced through the recycling of the powder in actual use. Research shows that the sintered nylon powder generates viscous flow due to the aggravated molecular chain segment movement, which can cause the increase of viscosity and the deterioration of melt fluidity, thereby causing the reduction of the performance and the reduction of the surface finish of the sintered part; it can be seen that improving the melt flow of nylon powder is a key factor in improving the reuse rate of nylon powder.
In the nitrogen atmosphere in the sintering process, condensation reaction can occur on the terminal carboxyl groups and the terminal amino groups which are not completely blocked in the main chain of the nylon molecules, so that the molecular weight of the recovered powder is increased, a high-temperature aging phenomenon is generated, the melt fluidity is obviously reduced, and the reuse rate of the nylon powder is reduced. The current common method is to mix uncured powder around the sintered part with new powder and then reuse the mixture. However, since the mixing amount of new powder is large, the reuse rate of the reclaimed powder is low, and the property change of the added reclaimed powder material can have a certain influence on the performance of the sintered part, the recycling frequency of the reclaimed powder is very limited.
Therefore, nylon needs to be modified, entanglement of nylon molecular chains in the sintering process is effectively reduced, and molecular weight in the aging process is prevented from increasing, so that the reduction of melt fluidity is avoided, and the reuse rate of nylon powder is improved.
Disclosure of Invention
The invention aims to provide the nylon powder for high-multiplexing-rate 3D printing, which improves the multiplexing rate, has a plurality of recycling times, reduces the cost and improves the roughness of the surface of a sintered part.
The nylon powder for high-multiplexing-rate 3D printing is prepared from nylon monomers and a blocking modifier, wherein the blocking modifier has the following structure:
Wherein x=1 to 20, preferably x=5 to 15.
In order to reduce the influence of high-temperature aging of nylon powder on melt fluidity in the sintering process, the novel functionalized aromatic hydroxyl-terminated polyether end-capping modifier is introduced, so that the reduction of melt fluidity caused by end group condensation in the high-temperature sintering process is avoided. By introducing an aromatic benzene ring structure, the aromatic benzene ring structure is conjugated with O, N atoms in an amide bond, and simultaneously the introduced amide bond enhances intermolecular acting force, so that the heat resistance and stability of a nylon molecular chain are better; meanwhile, a polyether soft chain segment is introduced, so that molecular chain entanglement is effectively prevented.
The nylon self is of a long carbon chain structure and has better flexibility, so that aromatic hydroxyl-terminated polyether of a novel structure is introduced as an end-capping modifier, the direction of an added ether chain is consistent with the direction of a nylon main chain, the flexibility of the tail end of the nylon chain is properly increased by the ether chain, the molecular structure of the nylon chain is linear, the tail end distance of mean square is reduced, the entanglement degree of the tail end of the nylon is effectively avoided, the toughness is improved, the entanglement of the molecular chain in the sintering process is reduced, and the fluidity of nylon powder is increased; the benzene ring structure introduced at the tail end of the chain increases rigidity through conjugation, reduces the decrease of strength and glass transition temperature caused by the introduction of a flexible chain segment, and improves the heat resistance of a molecular chain; the introduced amide bond can effectively improve the stability thereof.
In the invention, the nylon monomer is one or more raw materials for preparing PA6, PA11, PA12, PA66, PA610, PA612, PA1010, PA1012 and PA 1212; preferably, the molar ratio of the nylon monomer to the capping modifier is (100-130): 1, preferably (110-120): 1.
In the invention, the preparation steps of the end capping modifier are as follows:
s1: placing monoamine polyether amine and benzoic acid in an organic solvent I, adding a dehydrating agent to react with a catalyst, washing and drying to obtain a compound A;
s2: and (3) dissolving the compound A in an organic solvent II, adding Lewis acid, cooling, heating for reaction, quenching, removing water and drying after the reaction is finished to obtain the target end-capped modifier.
In one embodiment, the above end-capping modifier preparation step is of the formula:
in the invention, the monoamine polyether amine S1 has the following structure:
Wherein x=1 to 20, preferably x=5 to 15.
In the invention, the organic solvent I in S1 is anhydrous Dimethylformamide (DMF) and/or Dichloromethane (DCM).
In the present invention, the dehydrating agent S1 is a carbodiimide condensing agent, preferably 1- (3-dimethylaminopropyl) -3-Ethylcarbodiimide (EDCI).
In the present invention, the catalyst of S1 is a nucleophilic acylation catalyst, preferably 4-Dimethylaminopyridine (DMAP); preferably, the mol ratio of the monoamine polyether amine, the benzoic acid, the dehydrating agent and the catalyst is 1 (1-1.1): 1-3): 0.5-2;
in the present invention, S1 was washed with saturated NaCl solution and dried over anhydrous Na 2SO4.
In the present invention, the compound a of S1 has the following structure:
Wherein x=1 to 20, preferably x=5 to 15.
In the invention, the organic solvent II of S2 is Dichloromethane (DCM) and/or N, N-Dimethylformamide (DMF).
In the invention, the Lewis acid S2 is boron tribromide and/or boron trifluoride; preferably, the molar ratio of Lewis acid to compound A is (1-2): 1.
In the invention, S2 is cooled by dry ice-acetone bath and naturally warmed to room temperature.
In the invention, S2 is stirred for 2-4 h.
In the invention, S2 is quenched by adding water.
Another object of the present invention is to provide a method for preparing nylon powder for high reuse rate 3D printing.
A method for preparing nylon powder for high multiplexing rate 3D printing, which comprises the following steps:
optionally, for copolymerized nylon, nylon salt is first prepared, SS1: adding dibasic acid, diamine and water into a reaction kettle, filtering and drying to obtain nylon salt B;
SS2: adding nylon salt B or nylon monomer for homopolymerization, water, a blocking modifier and a catalyst into a polymerization reaction kettle for reaction, and then bracing and granulating to obtain target nylon C;
SS3: and (3) dissolving the nylon C in an organic solvent IV, filtering and drying to obtain nylon powder.
In the invention, the dibasic acid of SS1 is one or more of adipic acid, sebacic acid, undecanedioic acid, dodecaanedioic acid, tridecanedioic acid and tetradecanedioic acid.
In the invention, the diamine of SS1 is one or more of hexamethylenediamine, decamethylenediamine, undecanediamine, dodecamethylenediamine, tridecyldiamine and tetradecanediamine.
In the invention, the nylon monomer for homopolymerization of SS2 is one or more of caprolactam, undecanoic acid and laurolactam.
In the invention, the catalyst SS2 is zirconium n-butoxide and/or tetrabutyl titanate; preferably, the catalyst is added in an amount of 0.1-0.3% by mass of nylon salt and/or nylon monomer for homopolymerization.
In the present invention, the organic solvent IV described in SS3 is absolute ethanol and/or N, N-Dimethylformamide (DMF), preferably absolute ethanol.
In the invention, an antioxidant is added into SS3, the antioxidant is a composite antioxidant composed of hindered phenol antioxidants and phosphite antioxidants, the hindered phenol antioxidants are preferably N, N' -bis- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine (antioxidant 1098), and the phosphite antioxidants are preferably tris (2, 4-di-tert-butyl) phenyl phosphite (antioxidant 168).
In the present invention, SS3 is added with a flow aid which is fumed silica and/or fumed alumina, preferably fumed silica.
Compared with the prior art, the invention has the following positive effects:
(1) The entanglement of nylon molecular chains in the sintering process is effectively reduced, and the molecular weight in the process is prevented from increasing;
(2) The melt fluidity is prevented from being reduced in the powder sintering process, the nylon powder multiplexing rate is improved, the melt index reduction degree is less than 20% after 8 times of sintering, and the mechanical property is not obviously reduced.
Drawings
FIG. 1 is a graph showing the results of melt index (235 ℃,2.16 kg) over time during high temperature aging of the nylon powder of example 1 (novel end-capping modifier) and the nylon powder of comparative example 1 (adipic acid end-capping).
Detailed Description
The present invention is further illustrated by the following specific examples, which are given by way of illustration only and are not intended to limit the scope of the invention.
Main raw material information: monoamine polyetheramines, hensite JEFF AMINE M series monoamines; benzoic acid, tianjin, denou chemical Co., ltd; carbodiimide hydrochloride (EDCI, analytically pure), beijing coupling technologies limited; catalyst DMAP (analytically pure), shanghai taitan technologies, inc; absolute ethyl alcohol, methylene dichloride, dimethylformamide, sodium chloride and anhydrous sodium sulfate are all analytically pure, and are available from national pharmaceutical groups chemical reagent Co., ltd; zirconium n-butoxide, tetrabutyl titanate, boron trifluoride and boron tribromide are all analytically pure, and the boron tribromide is Alatine; antioxidant 168, antioxidant 1098, basf; titanium dioxide TR52, hensmal.
Instrument and equipment information: melt index apparatus, 7026, italy Ceast;3D printer, HT252P, hunan Hua Shugao family, company of liability, inc; heating a high-temperature furnace, YJDQ-8-12, and detecting Chongqing English; universal tester, 5984, instron; pendulum impact tester, 9400, instron.
Test standard: tensile properties, reference standard ISO 527-1/2; notched impact strength of a simply supported beam is referred to in the standard ISO 179/1eA.
Example 1
Preparing a blocking modifier:
S1: 120g of monoamine polyetheramine M-100, 122g of benzoic acid, 191g of a dehydrating agent EDCI and 61.1g of a catalyst DMAP (molar ratio 1:1:1:0.5) are added into 0.5L of anhydrous dichloromethane, the mixture is stirred at room temperature for reaction for 12 hours, then saturated NaCl aqueous solution is added for washing 3 times, anhydrous Na 2SO4 is added into the solution, and the mixture is kept stand for 1 hour, and then the product is obtained by filtration.
S2: adding the S1 product into 0.5L of anhydrous dichloromethane, placing the system into a dry ice-acetone bath, dropwise adding 250g of boron tribromide (the molar ratio is 1:1), naturally heating to room temperature, stirring for reaction for 3h, and adding 0.5L of pure water for quenching reaction; separating the water phase from the organic phase by using a separating funnel, and performing rotary evaporation on the organic phase to obtain the target aromatic hydroxyl-terminated polyether end-capping modifier.
Preparing nylon powder:
SS1: adding 1.72kg of decanediamine, 2.30kg of dodecanedioic acid and 4kg of deionized water into a reaction kettle (the molar ratio of amine to acid is 1:1, the mass of deionized water is the sum of the mass of amine and the mass of acid), replacing air in the kettle with nitrogen for three times, heating to 60 ℃ for reaction for 1-2 hours, discharging, naturally cooling the product to room temperature, filtering and vacuum drying the salt solution after nylon 1012 salt is separated out, and obtaining about 3.8kg of nylon 1012 salt.
SS2: adding 3.8kg of nylon 1012 salt, 3.8g of zirconium n-butoxide and 18.2g of end-capping modifier into a polymerization kettle (the molar ratio of the sum of nylon raw materials to the end-capping modifier is 110:1, the molar ratio of the nylon 1012 salt to the end-capping modifier is 55:1, the zirconium n-butoxide is 0.1% of the salt mass), adding 304g of deionized water (the deionized water weight is 8% of the salt weight), replacing air in the kettle with nitrogen for three times after the deionized water is added, then introducing nitrogen with the pressure of 0.2MPa (gauge pressure) as inert gas shielding gas, heating to 210 ℃, keeping the pressure in the reaction kettle to 1.5MPa for 1h, then slowly reducing the pressure to normal pressure, heating to 250 ℃, vacuumizing and reducing the pressure for drainage, continuing to react for 2h, stopping heating, and performing grain cutting after water cooling bracing to obtain nylon 1012 granules.
SS3: 1kg of nylon 1012 granules, 5kg of ethanol, 1g of antioxidant 1098 and 1g of antioxidant 168 are added into a high-pressure reaction kettle (the weight ratio of the nylon 1012 to the ethanol solvent to the antioxidant 1098 to the antioxidant 168 is 1:5:0.1 percent: 0.1 percent), stirred and heated to 150 ℃ for 1h at constant temperature, the pressure is maintained at 0.8MPa, then the temperature and the pressure are reduced to normal pressure, and nylon 1012 powder is separated out. After the nylon 1012 powder was dried by a centrifuge, it was placed in a vacuum oven to remove residual solvent.
And adding the obtained dry nylon powder and fumed silica with the mass ratio of 0.1% into a high-speed mixer, and uniformly mixing to obtain the target nylon powder.
Nylon powder evaluation:
A selective laser sintering environment was simulated in a heating furnace at 170℃under nitrogen atmosphere, and the melt index (235℃and 2.16 kg) was varied with time during high temperature ageing of the powder as shown in FIG. 1.
3D printing test is continuously carried out for 8 times on the basis of no new powder addition, the forming parameters of each time are the same, the temperature of a temperature field is set to 170 ℃, the laser power is 45W, the scanning speed is 4000mm/s, the powder laying thickness is 0.1mm, the scanning interval is 0.1mm, the sintering is carried out, and the melt index (235 ℃,2.16 kg), the tensile strength and the tensile breaking elongation are changed along with the sintering times as shown in table 1:
TABLE 1 PA1012 powder melt index and sintered part physical Property Change
Example 2
S1: 300g of monoamine polyetheramine M-300, 122g of benzoic acid, 382g of a dehydrating agent EDCI and 122.2g of a catalyst DMAP (molar ratio 1:1:2:1) are added into 0.5L of anhydrous dichloromethane, the mixture is stirred at room temperature for reaction for 12 hours, then saturated NaCl aqueous solution is added for washing 3 times, anhydrous Na 2SO4 is added into the solution, and the mixture is kept stand for 1 hour, and then the product is obtained by filtration.
S2: adding the S1 product into 0.5L of anhydrous dichloromethane, placing the system into a dry ice-acetone bath, dropwise adding 500g of boron tribromide (the molar ratio is 1:2), naturally heating to room temperature, stirring for reaction for 3h, and adding 0.5L of pure water for quenching reaction; separating the water phase from the organic phase by using a separating funnel, and performing rotary evaporation on the organic phase to obtain the target aromatic hydroxyl-terminated polyether end-capping modifier.
Preparing nylon powder:
SS2: adding 2.01kg of 11-aminoundecanoic acid, 6.0g of zirconium n-butoxide and 25.0g of end-capping modifier into a reaction kettle (the mol ratio of the 11-aminoundecanoic acid to the end-capping modifier is 120:1, the zirconium n-butoxide is 0.3 percent of the mass of the 11-aminoundecanoic acid), adding 160g of deionized water (the weight of the deionized water is 8 percent of the weight of the 11-aminoundecanoic acid), replacing air in the kettle with nitrogen for three times after the deionized water is added, then introducing nitrogen with the pressure of 0.2MPa (gauge pressure) as inert gas shielding gas, heating to 220 ℃, keeping the pressure in the reaction kettle to about 2.5MPa, keeping the pressure for 1h, slowly reducing the pressure to normal pressure, reducing the temperature to 250 ℃, vacuumizing, reducing the pressure for drainage, continuously reacting for 2h, stopping heating, and carrying out granulating after water cooling bracing to obtain nylon 11 granules.
SS3: 1kg of nylon 11 granules, 5kg of ethanol, 1g of antioxidant 1098 and 1g of antioxidant 168 are added into a high-pressure reaction kettle (the weight ratio of nylon 11 to ethanol solvent to antioxidant 1098 to antioxidant 168 is 1:5:0.1 percent: 0.1 percent), stirred and heated to 150 ℃ for 1h at constant temperature, the pressure is maintained at 0.8Mpa, then the temperature is reduced and the pressure is reduced to normal pressure, and nylon 11 powder is separated out. After the nylon 11 powder was dried by a centrifuge, it was placed in a vacuum oven to remove residual solvent.
And adding the obtained dry nylon powder and fumed silica with the mass ratio of 0.1% into a high-speed mixer, and uniformly mixing to obtain the target nylon powder.
Nylon powder evaluation:
3D printing test is continuously carried out for 8 times on the basis of no new powder addition, the forming parameters of each time are the same, the temperature of a temperature field is set to 170 ℃, the laser power is 45W, the scanning speed is 4000mm/s, the powder laying thickness is 0.1mm, the scanning interval is 0.1mm, the sintering is carried out, and the melt index (235 ℃,2.16 kg), the tensile strength and the tensile breaking elongation are changed along with the sintering times, as shown in Table 2:
TABLE 2 melt index of PA11 powder and physical Properties change of sintered article
Example 3
Preparing a blocking modifier:
S1: 600g of monoamine polyetheramine M-600, 134.2g of benzoic acid, 382g of a dehydrating agent EDCI and 183.3g of a catalyst DMAP (molar ratio 1:1.1:2:1.5) are added into 0.5L of anhydrous dichloromethane, the mixture is stirred at room temperature for reaction for 12 hours, then saturated NaCl aqueous solution is added for washing 3 times, anhydrous Na 2SO4 is added into the solution for standing for 1 hour, and the product is obtained by filtration.
S2: adding the S1 product into 0.5L of anhydrous dichloromethane, placing the system into a dry ice-acetone bath, dropwise adding 67.8g of boron trifluoride (the molar ratio is 1:1), naturally heating to room temperature, stirring for reaction for 3h, and adding 0.5L of pure water for quenching reaction; separating the water phase from the organic phase by using a separating funnel, and performing rotary evaporation on the organic phase to obtain the target aromatic hydroxyl-terminated polyether end-capping modifier.
Preparing nylon powder:
SS1: adding 1.72kg of decanediamine, 2.02kg of sebacic acid and 3.74kg of deionized water into a reaction kettle (the molar ratio of amine to acid is 1:1, the mass of deionized water is the sum of the mass of amine and the mass of acid), replacing air in the kettle with nitrogen for three times, heating to 60 ℃ for reaction for 1-2 hours, discharging, naturally cooling the product to room temperature, filtering and vacuum drying the salt solution after the nylon 1010 salt is separated out, and obtaining about 3.6kg of nylon 1010 salt.
SS2: adding 3.6kg of nylon 1010 salt, 5.4g of tetrabutyl titanate and 100g of end-capping modifier into a polymerization kettle (the molar ratio of the sum of nylon raw materials to the end-capping modifier is 120:1, the molar ratio of the nylon 1010 salt to the end-capping modifier is 60:1, the tetrabutyl titanate is 0.15% of the salt mass), adding 288g of deionized water (the deionized water weight is 8% of the salt weight), replacing air in the kettle with nitrogen for three times after the deionized water is added, then introducing nitrogen with the pressure of 0.2MPa (gauge pressure) as inert gas shielding gas, heating to 210 ℃, keeping the pressure in the reaction kettle to about 3MPa, keeping the pressure for 1h, then slowly reducing the pressure to normal pressure, heating to 250 ℃, vacuumizing, reducing the pressure to drain water, continuing to react for 2h, stopping heating, and performing grain cutting after water cooling bracing to obtain nylon 66 granules.
SS3: 1kg of nylon 1010 granules, 5kg of ethanol, 1g of antioxidant 1098 and 1g of antioxidant 168 are added into a high-pressure reaction kettle (the weight ratio of nylon 1010 to ethanol solvent to antioxidant 1098 to antioxidant 168 is 1:5:0.1 percent: 0.1 percent), stirred and heated to 150 ℃ for 1h at constant temperature, the pressure is maintained at 0.8MPa, then the temperature and the pressure are reduced to normal pressure, and nylon 1010 powder is separated out. After the nylon 1010 powder was dried by centrifuge, it was placed in a vacuum oven to remove residual solvent.
And adding the obtained dry nylon powder and fumed silica with the mass ratio of 0.1% into a high-speed mixer, and uniformly mixing to obtain the target nylon powder.
Nylon powder evaluation:
3D printing test is continuously carried out for 8 times on the basis of no new powder addition, the forming parameters of each time are the same, the temperature of a temperature field is set to 185 ℃, the laser power is 45W, the scanning speed is 4000mm/s, the powder laying thickness is 0.1mm, the scanning interval is 0.1mm, the sintering is carried out, and the melt index (235 ℃,2.16 kg), the tensile strength and the tensile breaking elongation are changed along with the sintering times, as shown in Table 3:
TABLE 3 melt index of PA1010 powder and physical property change of sintered article
Example 4
S1: 950g of monoamine polyetheramine M-1000, 134g of benzoic acid, 573g of a dehydrating agent EDCI and 244.4g of a catalyst DMAP (molar ratio 1:1.1:3:2) are added into 0.8L of anhydrous dichloromethane, the mixture is stirred at room temperature for reaction for 12 hours, then saturated NaCl aqueous solution is added for washing 3 times, anhydrous Na 2SO4 is added into the solution for standing for 1 hour, and the product is obtained by filtration.
S2: adding the S1 product into 0.8L of anhydrous dichloromethane, placing the system into a dry ice-acetone bath, dropwise adding 135.6g of boron trifluoride (the molar ratio is 1:2), naturally heating to room temperature, stirring for reaction for 3h, and adding 0.8L of pure water for quenching reaction; separating the water phase from the organic phase by using a separating funnel, and performing rotary evaporation on the organic phase to obtain the target aromatic hydroxyl-terminated polyether end-capping modifier.
Preparing nylon powder:
SS2: adding 1.97kg of laurolactam, 4.9g of tetrabutyl titanate and 90g of end-capping modifier into a reaction kettle (the molar ratio of the laurolactam to the end-capping modifier is 110:1, the tetrabutyl titanate is 0.25% of the weight of the laurolactam), adding 157g of deionized water (the weight of the deionized water is 8% of the weight of the laurolactam), replacing air in the kettle with nitrogen for three times after the deionized water is added, then introducing nitrogen with the pressure of 0.2MPa (gauge pressure) as inert gas shielding gas, heating to 270 ℃, keeping the pressure in the reaction kettle to about 2MPa, keeping the pressure for 4 hours, slowly reducing the pressure to normal pressure, reducing the temperature to 250 ℃, vacuumizing, reducing the pressure, draining water, continuously reacting for 2 hours, stopping heating, and performing granulating after water cooling bracing to obtain nylon 12 granules.
SS3: 1kg of nylon 12 granules, 5kg of ethanol, 1g of antioxidant 1098 and 1g of antioxidant 168 are added into a high-pressure reaction kettle (the weight ratio of the nylon 12 to the ethanol solvent to the antioxidant 1098 to the antioxidant 168 is 1:5:0.1 percent: 0.1 percent), stirred and heated to 150 ℃ for 1h at constant temperature, the pressure is maintained at 0.8MPa, then the temperature and the pressure are reduced to normal pressure, and nylon 12 powder is separated out. After the nylon 12 powder was dried by a centrifuge, it was placed in a vacuum oven to remove residual solvent.
And adding the obtained dry nylon powder and fumed silica with the mass ratio of 0.1% into a high-speed mixer, and uniformly mixing to obtain the target nylon powder.
Nylon powder evaluation:
3D printing test is continuously carried out for 8 times on the basis of no new powder addition, the recycling molding parameters are the same each time, the temperature field temperature is set to 170 ℃, the laser power is set to 45W, the scanning speed is 4000mm/s, the powder laying thickness is 0.1mm, the scanning interval is 0.1mm, sintering is carried out, and the melt index, the tensile strength and the tensile breaking elongation are changed along with the sintering times as shown in Table 4:
TABLE 4 PA12 powder melt index and sintered part physical Property Change
Comparative example 1
In comparison with example 1, adipic acid was used as a capping agent.
Preparing nylon powder:
SS1: adding 1.72kg of decanediamine, 2.30kg of dodecanedioic acid and 4kg of deionized water into a reaction kettle (the molar ratio of amine to acid is 1:1, the mass of deionized water is the sum of the mass of amine and the mass of acid), replacing air in the kettle with nitrogen for three times, heating to 60 ℃ for reaction for 1-2 hours, discharging, naturally cooling the product to room temperature, filtering and vacuum drying the salt solution after nylon 1012 salt is separated out, and obtaining about 3.8kg of nylon 1012 salt.
SS2: 3.8kg of nylon 1012 salt and 26.6g of adipic acid (end capping agent) are added into a polymerization kettle (the molar ratio of the sum of the nylon raw materials to the adipic acid is 110:1, the molar ratio of the nylon 1012 salt to the end capping agent is 55:1), 304g of deionized water (the weight of the deionized water is 8% of the weight of the salt) is added, after the deionized water is added, the air in the kettle is replaced by nitrogen for three times, then nitrogen with the pressure of 0.2MPa (gauge pressure) is introduced as inert gas shielding gas, the temperature is raised to 210 ℃, the pressure in the reaction kettle reaches 1.5MPa, the pressure is maintained for 1h, then the pressure is slowly reduced to normal pressure, the temperature is raised to 250 ℃, the vacuum pumping and the pressure reducing drainage are carried out, the reaction is continued for 2h, then the heating is stopped, and the nylon 1012 granules are obtained after the water cooling bracing and granulating.
SS3: 1kg of nylon 1012 granules, 5kg of ethanol, 1g of antioxidant 1098 and 1g of antioxidant 168 are added into a high-pressure reaction kettle (the weight ratio of the nylon 1012 to the ethanol solvent to the antioxidant 1098 to the antioxidant 168 is 1:5:0.1 percent: 0.1 percent), stirred and heated to 150 ℃ for 1h at constant temperature, the pressure is maintained at 0.8MPa, then the temperature and the pressure are reduced to normal pressure, and nylon 1012 powder is separated out. After the nylon 1012 powder was dried by a centrifuge, it was placed in a vacuum oven to remove residual solvent.
And adding the obtained dry nylon powder and fumed silica with the mass ratio of 0.1% into a high-speed mixer, and uniformly mixing to obtain the target nylon powder.
Nylon powder evaluation:
The selective laser sintering environment is simulated in a heating furnace, the temperature is 170 ℃ under the nitrogen atmosphere, and the melt index changes with time in the high-temperature aging process of the powder, which is shown in the figure 1.
3D printing test is continuously carried out for 8 times on the basis of no new powder addition, the forming parameters of each time are the same, the temperature of a temperature field is set to 170 ℃, the laser power is 45W, the scanning speed is 4000mm/s, the powder laying thickness is 0.1mm, the scanning interval is 0.1mm, the sintering is carried out, and the melt index (235 ℃,2.16 kg), the tensile strength and the tensile breaking elongation are changed along with the sintering times, as shown in Table 5:
TABLE 5 PA1012 powder melt index and sintered part physical Property Change
As compared with example 1, except that adipic acid was used as the end-capping agent, it can be seen from table 5 that the melt index of PA1012 powder significantly decreased with the increase of the number of sintering, i.e., the melt flowability significantly decreased; meanwhile, the tensile strength, the elongation at break and the impact toughness are low, but the tensile strength is increased to a certain extent along with the increase of the multiplexing times, and the elongation at break shows a remarkable decreasing trend; the impact toughness of the composite material shows a trend of increasing and then decreasing with the increase of the multiplexing times. The melt flowability and mechanical properties are inferior to those of the novel end-capping modifier used in example 1.
Comparative example 2
In comparison with example 4, adipic acid was used as a capping agent.
Preparing nylon powder:
SS2: adding 1.97kg of laurolactam and 13.3g of adipic acid (end capping agent) into a reaction kettle (the molar ratio of laurolactam to adipic acid is 110:1), adding 157g of deionized water (the weight of deionized water is 8% of the weight of laurolactam), replacing air in the kettle with nitrogen three times after the deionized water is added, then introducing nitrogen with the pressure of 0.2MPa (gauge pressure) as inert gas shielding gas, heating to 270 ℃, maintaining the pressure in the reaction kettle for 4 hours, slowly reducing the pressure to normal pressure, reducing the temperature to 250 ℃, vacuumizing, reducing the pressure to drain water, continuing to react for 2 hours, stopping heating, and granulating after water cooling bracing to obtain nylon 12 granules.
SS3: 1kg of nylon 12 granules, 5kg of ethanol, 1g of antioxidant 1098 and 1g of antioxidant 168 are added into a high-pressure reaction kettle (the weight ratio of the nylon 12 to the ethanol solvent to the antioxidant 1098 to the antioxidant 168 is 1:5:0.1 percent: 0.1 percent), stirred and heated to 150 ℃ for 1h at constant temperature, the pressure is maintained at 0.8MPa, then the temperature and the pressure are reduced to normal pressure, and nylon 12 powder is separated out. After the nylon 12 powder was dried by a centrifuge, it was placed in a vacuum oven to remove residual solvent.
And adding the obtained dry nylon powder and fumed silica with the mass ratio of 0.1% into a high-speed mixer, and uniformly mixing to obtain the target nylon powder.
Nylon powder evaluation:
3D printing test is continuously carried out for 8 times on the basis of no new powder addition, the recycling molding parameters are the same each time, the temperature field temperature is set to 170 ℃, the laser power is set to 45W, the scanning speed is 4000mm/s, the powder laying thickness is 0.1mm, the scanning interval is 0.1mm, sintering is carried out, and the melt index, the tensile strength and the tensile breaking elongation are changed along with the sintering times as shown in Table 6:
TABLE 6 PA12 powder melt index and sintered part physical Property Change
Compared with example 4, the difference is that adipic acid is used as the end capping agent, and as shown in table 6, the melt index of PA12 powder is obviously reduced along with the increase of sintering times, and the tensile strength, the elongation at break and the impact toughness are lower, but along with the increase of multiplexing times, the tensile strength is increased to a certain extent, and the elongation at break shows a obvious reduction trend; the impact toughness of the composite material shows a trend of increasing and then decreasing with the increase of the multiplexing times. The melt flowability and mechanical properties are inferior to those of example 4, which uses the novel end-capping modifier.
After the nylon 12 powder prepared by the method is repeatedly sintered for eight times, the melt index is reduced from 48.8g/10min to 42.3g/10min, and is reduced by 13.3% compared with the melt index of the new powder, the tensile strength and the elongation at break of a formed part prepared from the powder subjected to end-capped modification are not obviously reduced for 8 times, and the impact toughness is more stable. Therefore, the aromatic hydroxyl-terminated polyether modifier with a novel structure is introduced, so that the melt fluidity reduction caused by the increase of the molecular weight and the molecular chain entanglement in the nylon powder sintering process can be effectively avoided, the powder reusability is obviously improved, and meanwhile, the toughness of a formed part is enhanced.
Claims (16)
1. The nylon powder for high-multiplexing-rate 3D printing is characterized by being prepared from nylon monomers and a blocking modifier, wherein the blocking modifier has the following structure:
wherein x=1 to 20.
2. Nylon powder according to claim 1, characterized in that in the end-capping modifier structure, X = 5-15.
3. Nylon powder according to claim 1, characterized in that the nylon monomer is a raw material for preparing one or more of PA6, PA11, PA12, PA66, PA610, PA612, PA1010, PA1012, PA 1212.
4. The nylon powder of claim 3, wherein the molar ratio of the nylon monomer to the capping modifier is (100-130): 1.
5. The nylon powder of claim 4, wherein the molar ratio of the nylon monomer to the capping modifier is (110-120): 1.
6. Nylon powder according to claim 1 or 2, characterized in that the end-capping modifier preparation step is:
s1: placing monoamine polyether amine and benzoic acid in an organic solvent I, adding a dehydrating agent to react with a catalyst, washing and drying to obtain a compound A;
S2: dissolving a compound A in an organic solvent II, adding Lewis acid, cooling, heating to react, quenching, removing water and drying after the reaction is finished to obtain a target end-capped modifier;
wherein, S1 monoamine polyether amine has the following structure:
wherein x=1 to 20.
7. The nylon powder of claim 6, wherein X = 5-15 in the monoamine polyetheramine of step S1;
and/or, the organic solvent I in the step S1 is anhydrous dimethylformamide and/or dichloromethane;
And/or, the dehydrating agent in the step S1 is a carbodiimide condensing agent;
and/or, the catalyst in the step S1 is a nucleophilic acylation catalyst;
And/or, washing with saturated NaCl solution, and drying with anhydrous Na 2SO4;
and/or, the compound A in the step S1 has the following structure:
wherein x=1 to 20.
8. The nylon powder of claim 7 wherein the dehydrating agent of step S1 is 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide;
And/or the catalyst in the step S1 is 4-dimethylaminopyridine;
the mol ratio of the monoamine polyether amine, the benzoic acid, the dehydrating agent and the catalyst in the step S1 is 1 (1-1.1): 1-3): 0.5-2;
and/or, in the compound a described in step S1, x=5 to 15.
9. Nylon powder according to claim 6, characterized in that the organic solvent II of step S2 is dichloromethane and/or N, N-dimethylformamide;
And/or the Lewis acid in the step S2 is boron tribromide and/or boron trifluoride;
And/or, the temperature-reducing and temperature-increasing reaction in the step S2 is to adopt dry ice-acetone bath for temperature reduction, and naturally temperature-increasing to room temperature;
and/or, the temperature-rising reaction after the temperature reduction in the step S2 is stirring reaction for 2-4 h;
and/or, adding water to quench after the temperature rising reaction after the temperature is reduced in the step S2 is finished.
10. The nylon powder of claim 9, wherein the molar ratio of Lewis acid to compound A in step S2 is (1-2): 1.
11. A method for preparing nylon powder for high multiplexing rate 3D printing, the nylon powder being the nylon powder according to any one of claims 1 to 10, the method comprising the steps of:
optionally, for copolymerized nylon, nylon salt is first prepared, SS1: adding dibasic acid, diamine and water into a reaction kettle, filtering and drying to obtain nylon salt B;
SS2: adding nylon salt B or nylon monomer for homopolymerization, water, a blocking modifier and a catalyst into a polymerization reaction kettle for reaction, and then bracing and granulating to obtain target nylon C;
SS3: dissolving nylon C in an organic solvent IV, filtering and drying to obtain nylon powder;
wherein, the end capping modifier of SS2 has the following structure:
wherein x=1 to 20.
12. The method for preparing nylon powder according to claim 11, wherein the diacid in step SS1 is one or more of adipic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid;
And/or diamine in the step SS1 is one or more of hexamethylenediamine, decamethylenediamine, undecanediamine and dodecamethylenediamine.
13. The method for producing nylon powder according to claim 11, wherein the nylon monomer for homopolymerization in step SS2 is one or more of caprolactam, undecanoic acid and dodecalactam;
And/or the catalyst in the step SS2 is zirconium n-butoxide and/or tetrabutyl titanate.
14. The method of claim 13, wherein the catalyst is added in an amount of 0.1 to 0.3% based on the mass of the nylon salt and/or the nylon monomer for homopolymerization in step SS 2.
15. The method for preparing nylon powder according to claim 11, wherein the organic solvent iv in step SS3 is absolute ethanol and/or N, N-dimethylformamide.
16. The method for preparing nylon powder as defined in claim 15, wherein the organic solvent iv in step SS3 is absolute ethanol.
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