A method for preparing a post-processed impregnated PP product and a flame-retardant PP product

Abstract

The present invention belongs to the technical field of functional post-processing of 3D printed PP parts, and specifically relates to a method for preparing a post-processed impregnant for a PP part and a flame-retardant PP part. The present invention synthesizes a new carbon-forming agent hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene, and then compounded with ammonium polyphosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and polyvinyl alcohol acetal to form a flame-retardant impregnant, and the proportion is adjusted to have optimal viscosity and flame-retardant properties. The impregnant is used to post-process the SLS-molded PP part, and the impregnant penetrates into the micro-voids of the PP part and adheres to the surface, and a firmly attached flame-retardant coating is formed after curing, which not only significantly improves the flame-retardant properties of the PP part, but also improves the durability of the flame-retardant coating, and can also produce a certain strengthening effect on the part. The present invention solves the problem of decreased mechanical properties due to the addition of flame retardants in filled flame-retardant modification, and significantly improves the flame-retardant properties without changing the original SLS molding process characteristics of PP and retaining the original mechanical properties of PP.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional processing of 3D printed PP parts, and in particular relates to a preparation method of a post-processed impregnation body of a PP part and a flame-retardant PP part. Background Art

[0002] Polypropylene (PP) is a thermoplastic resin made by propylene polymerization. It has the advantages of low price, high relative hardness, low density, high tensile strength, high impact strength, stress cracking resistance, good corrosion resistance and easy processing and molding. However, PP is very flammable, and its oxygen index (LOI) is only 17.4~18.5. When burning, it produces a large number of droplets and is very easy to spread flames. PP materials are used in many parts of automotive interiors, such as dashboards, door inner panels, glove boxes, pillar guards, seat guards, etc. When PP is used in automotive interior parts, its flame retardant properties must be improved to meet the combustion characteristics standards of automotive interior materials.

[0003] The advantage of 3D printing technology is that the product parts are highly designable, and almost any geometric and spatial shape can be manufactured. It has been widely used in many fields such as architecture, automotive parts, cultural relics restoration, and medical treatment. Selective laser sintering (SLS) is a relatively mature and widely used technology in 3D printing. In the manufacturing of automotive interior parts, it has the ability to generate large-size parts, and the printed products have excellent mechanical properties, temperature resistance and durability. It can be used for trial production of interior plastic parts, size assembly verification, functional verification, etc., and can even directly print the final parts used in the car.

[0004] Filling-type flame retardant modification is a very common polymer flame retardant modification technology currently used, that is, adding flame retardants to polymers for molding, thereby improving the flame retardant properties of molded parts. Therefore, the use of filling-type flame retardant modification technology to obtain flame retardant modified PP composite powder for SLS molding is expected to become a universal manufacturing method for various complex shapes of high flame retardant PP parts.

[0005] However, through practice, we gradually realized that if the filling flame retardant modification technology is directly combined with the SLS molding technology, many technical difficulties that are difficult to overcome will be faced. Since the powder spreading stage has high requirements on the morphology and particle size of the powder during SLS molding, the PP powder used for SLS molding should be in the shape of a tiny sphere as much as possible, so that it can be easily spread evenly. However, most flame retardants have irregular morphological structures and different sizes. There is a huge difference and serious mismatch between the morphological structure of the flame retardant and the morphological structure of the PP powder, which leads to uneven powder spreading during SLS molding, affecting the smooth sintering between layers, and then affecting the flame retardant properties and mechanical properties of PP parts. On the other hand, SLS molding is stress-free molding, lacking the effects and processes of traditional molding processes such as extrusion, injection molding, and compression molding to mix PP and flame retardants through huge compressive stress, resulting in weak interface effects between PP and flame retardants in SLS molded parts, further affecting the flame retardant properties and mechanical properties of PP parts. In addition, when flame retardants are added to PP powder, as the content of flame retardants increases, the spatial density of the flame retardant powder distributed in the PP powder gradually increases, resulting in a weakening of the bonding force between adjacent PP powders during sintering. Therefore, in practice, the improvement of flame retardant properties and mechanical properties is often contradictory. Summary of the invention

[0006] In view of the fact that in the prior art, when the flame-retardant modified PP composite powder obtained by using the filling flame-retardant modification technology is subjected to SLS molding, there are problems such as powder morphology mismatch and lack of external compressive stress, which leads to limited improvement in flame retardant performance and poor mechanical properties. The present invention proposes a method for preparing a post-processed impregnation body of a PP product and a flame-retardant PP product, with the aim of achieving a good flame retardant effect without affecting the normal SLS molding process of PP and the mechanical properties of its products.

[0007] The invention uses hexachlorocyclotriphosphazene (HCCP) and 4,4-diaminodiphenyl sulfone (DDS) to synthesize a novel carbon former hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene by a one-step method, compound the novel carbon former with flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acid source gas source ammonium polyphosphate (APP), and use polyvinyl alcohol formal (PVFA) as a film-forming agent to prepare an impregnated body with excellent flame retardant performance and bonding performance; then, the impregnated body is used to perform wet vacuum impregnation treatment on a PP product formed by SLS, and the impregnated body is bonded to the surface and micro-voids of the PP product to form a flame retardant protective layer, thereby preparing a PP product with both excellent flame retardant performance and mechanical properties.

[0008] The scheme of the present invention has the following advantages: firstly, the original SLS molding process characteristics and mechanical properties of PP are not affected, and the SLS molding process performance and mechanical properties of PP are not reduced due to the addition of flame retardants; secondly, the micro-voids existing on the surface of SLS molded parts are cleverly utilized to allow the flame-retardant impregnation body to penetrate into the micro-voids, which can not only greatly improve the compatibility between PP and the flame retardant and improve the durability of the flame-retardant coating, but also increase the thickness of the flame-retardant impregnation body on the surface of the PP parts and improve the flame retardant performance; thirdly, the cleaning and polishing post-processing steps for surface defects such as micro-thorns and micro-voids after SLS parts are formed are omitted, and the flame-retardant impregnation body coating replaces these post-processing steps.

[0009] The PP article post-processing impregnation body provided by the present invention comprises the following functional raw material components:

[0010] (1) Flame retardant, 100 parts by mass;

[0011] (2) Acid source and gas source, 5 to 11 parts by weight, preferably 6 to 8 parts by weight;

[0012] (3) charring agent, 2.5-10 parts by weight;

[0013] (4) Film-forming agent: 8 to 14 parts by weight, preferably 10 to 12 parts by weight.

[0014] Among them, the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO); the acid source and gas source are ammonium polyphosphate (APP), and APP has the functions of both acid source and gas source; the carbon former is hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene generated by the nucleophilic substitution reaction between hexachlorocyclotriphosphazene and 4,4-diaminodiphenyl sulfone; and the film former is polyvinyl alcohol acetal (PVFA).

[0015] Furthermore, the preparation method of the flame retardant carbon-forming agent hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene is carried out according to the following steps:

[0016] (1) Dissolve hexachlorocyclotriphosphazene (HCCP) in 1,4-dioxane and add the mixture into a 500 ml three-necked flask. Then, dissolve 4,4-diaminodiphenyl sulfone (DDS) in acetone at a molar ratio of 1:4 between hexachlorocyclotriphosphazene and 4,4-diaminodiphenyl sulfone. Condensate and reflux at 30-35°C. Add the mixture dropwise into the reaction system over a period of 1-1.5 hours and stir evenly at a speed of 500 r / min to obtain a mixed solution of the two.

[0017] (2) The mixed solution obtained in step (1) is gradually heated to 70-80° C., preferably 75° C., and condensed under reflux, and stirred evenly at a speed of 800 r / min for 24-48 h to obtain a crude reaction product of hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene.

[0018] (3) The crude reaction product hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene obtained in step (2) is cooled to room temperature, filtered and washed with acetone for 6 times, and dried in a vacuum oven at 60°C for 6 hours to finally obtain a purified carbon-forming agent hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene.

[0019] Further, the PP article post-treatment impregnation body is prepared by following the steps below or by scaling the preparation as required:

[0020] (1) Slowly add 8-14 g of film-forming agent polyvinyl methyl acetaldehyde (PVFA) into a beaker containing an appropriate amount of ethanol, stir for 15 min at 18-25 °C and a speed of 800 r / min to completely dissolve it in ethanol to obtain a PVFA solution.

[0021] (2) Add 100 g of DOPO to the PVFA solution obtained in step (1), stir at 18-25° C. for 10 min at a rotation speed of 800 r / min to obtain a DOPO-PVFA solution.

[0022] (3) 5-11 g of APP and 2.5-10 g of carbon-forming agent were slowly added to the above DOPO-PVFA solution in sequence, and stirred at room temperature for 20 min at a speed of 800 r / min to obtain a flame retardant impregnation solution.

[0023] (4) The flame retardant impregnation solution obtained in step (3) is placed in a 500 ml beaker, heated to 110-120°C to volatilize the ethanol, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reaches 350-400 mPa•s. The heating is stopped to obtain a post-treated flame retardant impregnation body.

[0024] The present invention also provides a method for preparing a flame-retardant PP product, firstly, the PP molded product is manufactured by using the SLS molding technology, and then the PP molded product is treated with the above-mentioned impregnation body. The specific treatment method comprises the following steps:

[0025] (1) Pretreatment: The SLS-molded PP parts are washed in clean water at 15-30°C for 3-8 minutes, drained, and dried in an oven at 70-75°C for 1-5 hours.

[0026] (2) Dry vacuum treatment: Place the pretreated PP parts into the impregnation basket, and then place the impregnation basket into the impregnation tank. Start the vacuum pump and draw vacuum for 5 to 15 minutes at a vacuum degree below 0.09 MPa to extract the air (or moisture) from the micropores and cracks of the parts.

[0027] (3) Wet vacuum treatment: inject the impregnation body into the impregnation tank, the liquid level of the impregnation body exceeds the impregnation basket by 3~5mm, evacuate the vacuum degree below 0.09MPa for 15~45min, then slowly release the pressure to normal pressure and continue impregnation for 3~5min.

[0028] (4) Drying: After the impregnation is completed, open the lid of the impregnation tank, use a hook to lift the impregnation basket off the surface of the impregnation body, put it into the spin dryer, spin dry the surface liquid until there is no impregnation liquid flowing on the surface, and then put the impregnation basket into the washing tank.

[0029] (5) Washing: Shake the immersion basket up and down 3 to 8 times in the washing tank, and shake it left and right 3 to 8 times for one wash, and the washing time is 2 to 3 minutes; after one wash, drain the water, refill the water, and repeat the washing 3 to 8 times. Drain the water for 3 to 8 hours after washing.

[0030] (6) Curing: Place the washed and drained PP parts in a constant temperature box and cure them at 80-90°C for 20-60 minutes. After curing, cool them naturally to room temperature to obtain a flame-retardant PP product with surface impregnation treatment.

[0031] Beneficial Effects

[0032] (1) The solution of the present invention is to post-treat the SLS-molded PP parts with a homemade impregnation body. There is no need to add flame retardant to the PP powder during SLS molding, so it will not affect the normal SLS molding process and parameters of PP.

[0033] (2) The solution of the present invention avoids directly adding flame retardants to PP powders, so there will be no uneven powder spreading and sintering due to powder morphology mismatch, and there will be no reduction in the mechanical properties of SLS-molded PP parts due to interference from flame retardant powders.

[0034] (3) In the impregnation body of the present invention, the homemade charring agent is compounded with DOPO and APP to form a high-performance flame retardant component system, which significantly improves the limiting oxygen index and vertical combustion level of the PP parts and improves the melting droplet situation of the PP parts.

[0035] (4) The flame retardant component and the film-forming component in the impregnation body of the present invention are mixed and adjusted to a reasonable viscosity, so that a high-quality protective layer with good toughness, water resistance and aging resistance can be formed on the surface of the SLS molded part.

[0036] (5) The present invention makes full use of the micro voids existing on the surface of the SLS molded part and adopts wet vacuum impregnation treatment to fully bond the impregnant to the surface and micro voids of the PP part to form a flame retardant protective layer, which significantly improves the bonding strength of the impregnant on the PP part and also significantly improves the penetration depth and utilization efficiency of the flame retardant component.

[0037] (6) The impregnation body of the present invention is fully combined with the PP product and covers its surface, which plays a good role in repairing and modifying surface defects such as burrs and micropores, significantly improving the surface state of the PP product and eliminating the cleaning and polishing post-processing steps for improving the surface state after SLS product molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Shown are the performance test results of each sample. DETAILED DESCRIPTION

[0039] The present invention is further illustrated by specific examples below. These examples are exemplary and are intended to illustrate the problem and explain the present invention, but are not intended to be limiting.

[0040] Carbon forming agent

[0041] The char-forming agent used in the subsequent examples of the present invention is hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene (CPCFA) generated by a nucleophilic substitution reaction between hexachlorocyclotriphosphazene and 4,4-diaminodiphenylsulfone.

[0042] The preparation method of the flame retardant carbon-forming agent hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene is carried out according to the following steps:

[0043] (1) Dissolve hexachlorocyclotriphosphazene (HCCP) in 1,4-dioxane and add the mixture to a 500 ml three-necked flask. Then, dissolve 4,4-diaminodiphenyl sulfone (DDS) in acetone at a molar ratio of 1:4 between hexachlorocyclotriphosphazene and 4,4-diaminodiphenyl sulfone. Condensate and reflux at 35°C. Add the mixture dropwise to the reaction system within 1.2 hours and stir evenly at a speed of 500 r / min to obtain a mixed solution of the two.

[0044] (2) The mixed solution obtained in step (1) was gradually heated to 75° C., condensed and refluxed, and stirred evenly at a speed of 800 r / min. The reaction was carried out for 48 hours to obtain a crude reaction product of hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene.

[0045] (3) The crude reaction product hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene obtained in step (2) is cooled to room temperature, filtered and washed with acetone for 6 times, and dried in a vacuum oven at 60°C for 6 hours to finally obtain a purified carbon-forming agent hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene.

[0046] (4) The product obtained in step (3) was subjected to Fourier transform infrared spectroscopy (FTIR) analysis. The infrared spectrum of hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene was 1498 cm -1 To 1596 cm -1The strong absorption peak at 1217 cm -1 The absorption peak at 606 cm -1 The P-Cl stretching vibration peak at 874 cm -1 A new PN absorption peak appeared nearby, indicating that a polycondensation reaction occurred between the two. -1 To 3457 cm -1 The absorption peak at represents the active -NH 2 , 3440 cm -1 The absorption peak at represents the stretching vibration of -NH-. The above results show that the polycondensation reaction of HCCP and DDS produces hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene (CPCFA).

[0047] Example 1

[0048] (1) Dissolve 8 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0049] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0050] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0051] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0052] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0053] Example 2

[0054] (1) Dissolve 10 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0055] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0056] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0057] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0058] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0059] Example 3

[0060] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0061] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0062] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, dry it in the impregnation tank at a vacuum pressure of less than 0.09MPa for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and then vacuum it for 15 minutes at less than 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0063] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0064] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0065] Example 4

[0066] (1) Dissolve 14 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0067] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0068] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0069] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0070] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0071] Example 5

[0072] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 5 g of APP and 5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0073] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0074] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0075] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0076] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0077] Example 6

[0078] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 9 g of APP and 5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0079] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0080] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0081] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0082] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0083] Example 7

[0084] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 11 g of APP and 5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0085] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0086] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0087] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0088] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0089] Example 8

[0090] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 2.5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0091] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0092] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0093] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0094] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0095] Example 9

[0096] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 7.5 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0097] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0098] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0099] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0100] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0101] Example 10

[0102] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 10 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0103] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0104] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0105] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0106] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0107] Embodiment 11

[0108] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 10 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0109] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0110] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, in the impregnation tank, the vacuum pressure is below 0.09MPa, and the dry vacuum treatment is carried out for 15 minutes. Then, the impregnation body is injected so that the liquid level of the impregnation liquid exceeds the impregnation basket by 3mm, and the vacuum is drawn for 30 minutes at below 0.09MPa, and the pressure is slowly released to normal pressure, and the impregnation is continued for 5 minutes. The impregnation basket is lifted off the surface of the impregnation body and placed in a spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0111] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0112] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0113] Example 12

[0114] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 10 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0115] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0116] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, in the impregnation tank, the vacuum pressure is below 0.09MPa, and the dry vacuum treatment is carried out for 15 minutes. Then, the impregnation body is injected so that the liquid level of the impregnation liquid exceeds the impregnation basket by 3mm, and the vacuum is drawn below 0.09MPa for 45 minutes, and the pressure is slowly released to normal pressure, and the impregnation is continued for 5 minutes. The impregnation basket is lifted off the surface of the impregnation body and placed in a spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0117] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0118] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0119] Embodiment 13

[0120] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 10 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0121] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0122] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0123] (4) The washed parts are placed in a hot water curing tank at a constant temperature of 85°C for 40 minutes.

[0124] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0125] Embodiment 14

[0126] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 10 g of CPCFA to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0127] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0128] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, place the vacuum pressure in the impregnation tank below 0.09MPa and dry vacuum for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and vacuum for 15 minutes at below 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0129] (4) The washed parts are placed in a hot water curing tank at a constant temperature of 85°C for 60 minutes.

[0130] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0131] Comparative Example 1

[0132] Carry out relevant performance tests on blank standard samples.

[0133] Comparative Example 2

[0134] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min to obtain an impregnation solution;

[0135] (2) placing the impregnation solution obtained in (1) above in a 500 ml beaker, heating it to 120° C., stirring it at a speed of 800 r / min, and after mixing evenly, stopping heating to obtain a post-treated impregnation body;

[0136] (3) Set the parameters for the pre-impregnation treatment: the washing water temperature is 25°C, the time is 5 minutes; the drying temperature is 75°C, the time is 2.5 hours. The parameters for the dry vacuum treatment are: the vacuum degree is below 0.09 MPa, and the time is 15 minutes. The parameters for the wet vacuum treatment are: 3 mm above the impregnation basket, the vacuum is below 0.09 MPa for 15 minutes, the pressure is slowly released to normal pressure, and the impregnation is continued for 5 minutes. Drying. Washing, the time is 3 minutes, and the washing is repeated 3 times.

[0137] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0138] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0139] Comparative Example 3

[0140] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of dimethyl methylphosphonate (DMMP) in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of CPCFA to the DMMP-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0141] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0142] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, dry it in the impregnation tank at a vacuum pressure of less than 0.09MPa for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and then vacuum it for 15 minutes at less than 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0143] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0144] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0145] Comparative Example 4

[0146] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of toluene diphenyl phosphate (CDP) in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of CPCFA to the CDP-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0147] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0148] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, dry it in the impregnation tank at a vacuum pressure of less than 0.09MPa for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and then vacuum it for 15 minutes at less than 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0149] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0150] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0151] Comparative Example 5

[0152] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of pentaerythritol to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0153] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0154] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, dry it in the impregnation tank at a vacuum pressure of less than 0.09MPa for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and then vacuum it for 15 minutes at less than 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0155] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0156] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0157] Comparative Example 6

[0158] (1) Dissolve 12 g of PVFA in anhydrous ethanol in a beaker and stir at 20 °C for 15 min. Then dissolve 100 g of DOPO in the PVFA solution and continue stirring for 10 min. Then add 7 g of APP and 5 g of isocyanate to the DOPO-PVFA solution and stir at room temperature for 20 min to obtain a flame retardant impregnation solution.

[0159] (2) The flame retardant impregnation solution obtained in (1) above was placed in a 500 ml beaker, heated to 120°C, and stirred at 800 r / min until the viscosity of the flame retardant impregnation solution reached 350 mPa·s. The heating was stopped to obtain a post-treated flame retardant impregnation body.

[0160] (3) Place the SLS-molded PP standard sample in clean water at 25°C for 5 minutes, and then dry it at 75°C for 2.5 hours. Then, dry it in the impregnation tank at a vacuum pressure of less than 0.09MPa for 15 minutes. Then inject the impregnation body so that the impregnation liquid level exceeds the impregnation basket by 3mm, and then vacuum it for 15 minutes at less than 0.09MPa, slowly release the pressure to normal pressure, and continue impregnation for 5 minutes. Lift the impregnation basket off the surface of the impregnation body and put it into the spin dryer for drying. Wash for 3 minutes, and repeat the washing 3 times.

[0161] (4) Place the washed parts into a hot water curing tank at a constant temperature of 85°C for 20 minutes.

[0162] (5) Conduct relevant performance tests on the standard specimens after infiltration.

[0163] Effect verification

[0164] The following properties of the PP standard specimens molded by SLS in Examples 1 to 14 and Control Examples 1 and 2 were tested: a vertical burning test was performed with reference to ASTM D3801-10, with a specimen size of 130 mm × 130 mm × 1.6 mm; a limiting oxygen index test was performed with reference to ASTM D2863-17, with a specimen size of 100 mm × 100 mm × 3.2 mm; and tensile strength was tested with reference to GB / T 1040.1-2018, using a dumbbell-shaped specimen of type A at a tensile rate of 50 mm / min.

[0165] Test results such as Figure 1 shown.

[0166] Through Figure 1Data analysis shows that for the PP standard sample formed by SLS, compared with the blank sample (Control Example 1), after adding hexa(4,4-diaminodiphenyl sulfone) cyclotriphosphazene, ammonium polyphosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and polyvinyl alcohol acetaldehyde (Examples 1 to 10), the limiting oxygen index is significantly increased, the vertical combustion reaches a higher level, the molten drop situation is significantly improved, and the tensile strength is also significantly improved with the increase of the addition amount. Compared with only the film-forming agent polyvinyl alcohol acetaldehyde (Control Example 2), after adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene and ammonium polyphosphate (Examples 1 to 10), the limiting oxygen index is also significantly increased, the vertical burning grade is significantly improved, and the tensile strength is also significantly improved with the increase of the addition amount. Moreover, with the increase of hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene (Examples 8 to 10) and ammonium polyphosphate (Examples 5 to 7), the three groups of data are improved respectively.

[0167] Compared with the flame retardant system formed by compounding hexa(4,4-diaminodiphenyl sulfone) cyclotriphosphazene, ammonium polyphosphate, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, Control Examples 3 and 4 respectively investigated the flame retardant system formed by compounding hexa(4,4-diaminodiphenyl sulfone) cyclotriphosphazene, ammonium polyphosphate, and dimethyl methylphosphonate, and the flame retardant system formed by compounding hexa(4,4-diaminodiphenyl sulfone) cyclotriphosphazene, ammonium polyphosphate, and diphenyl methyl phosphate. Compared with the flame retardants dimethyl methylphosphonate and diphenyl methyl phosphate (Control Examples 3 and 4), the tensile strength of DOPO as a flame retardant in the system is not much different, but due to the presence of PC bonds, its limiting oxygen index, hydrolysis resistance and flame retardant durability are better.

[0168] Compared with the flame retardant system formed by compounding hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene, ammonium polyphosphate, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, Control Examples 5 and 6 respectively investigated the flame retardant system formed by compounding pentaerythritol, ammonium polyphosphate, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and the flame retardant system formed by compounding isocyanate, ammonium polyphosphate, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Compared with the carbon forming agent pentaerythritol and isocyanate (Control Examples 5 and 6), the limiting oxygen index of the carbon forming agent CPCFA is higher and the flame retardant performance is better. Because CPCFA can form a highly cross-linked spatial structure in the system, it has excellent thermal stability and carbon forming performance.

[0169] With the extension of wet vacuum treatment time and curing time (Examples 11 to 14), the limiting oxygen index is further increased to more than 31%, and the vertical combustion all reaches the V-0 level, and no droplets occur, all achieve good flame retardant effects, and the mechanical properties are further improved. The reason is that ammonium polyphosphate carbonizes when heated, which can isolate the air and reduce the ignition point. The synergistic effect of phosphorus and nitrogen in cyclotriphosphazene has better flame retardant properties and self-extinguishing ability; and the coating is impregnated on the surface and micro-voids of the product, and has a certain enhancement function after full impregnation and curing. The post-treated flame-retardant impregnation body of the present invention can significantly improve the flame retardant properties of the PP standard sample formed by SLS, and the mechanical properties are significantly enhanced. Among them, the improvement of flame retardant properties is mainly contributed by the expansion flame retardant coating, and the improvement of its mechanical properties is due to the process of the present invention, which adopts the post-treatment method to impregnate the flame retardant coating on the surface of the product instead of directly using it as a filler to destroy its internal force.

[0170] Because the performance test must be carried out in accordance with the test standards, the above-mentioned Examples 1 to 14 and Comparative Examples 1 to 6 all use PP standard samples, and the post-treated flame-retardant impregnation body of the present invention is impregnated on the PP standard sample. Based on the flexibility of SLS molding, the shapes and structural parameters of the products that can be molded are more abundant, and it is especially good at molding hollow structure products with extremely complex structures. The size of the solid part that constitutes the hollow structure will be smaller, so that the ratio of the coating thickness to the size of the solid part of the product will be larger, and the unit mass of the PP product will contain more post-treated flame retardant, the flame retardant effect will be better, and the mechanical reinforcement effect will also be better. It can be seen that the application of the post-treated flame-retardant impregnation body of the present invention to the PP parts molded by SLS can not only improve the flame retardant properties of the PP products, but also avoid the loss of mechanical properties of the products caused by directly adding flame-retardant fillers. 。

[0171] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and features of the present invention so that people familiar with the technology in this field can understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a flame retardant PP product. Features: The PP molded parts are manufactured by SLS molding technology. The PP molded parts formed by SLS are spatial three-dimensional networks with hollow lattice structures. Then, the PP molded parts are impregnated with a post-treatment flame retardant impregnant for PP parts. The impregnant is combined with the surface and micro-voids of the PP parts and solidified to form a flame retardant protective layer. The impregnation process includes the following steps: Pretreatment: Wash the SLS-molded PP parts in clean water at 15-30°C, drain the water, and dry them at 70-75°C for 1-5 hours; Dry vacuum treatment: put the pretreated PP parts into the impregnation basket, and then put the impregnation basket into the impregnation tank, and evacuate the vacuum for 5-15 minutes at a vacuum degree below 0.09MPa to extract the air and / or moisture in the micropores and cracks of the PP parts; Wet vacuum treatment: Pour the impregnation body into the impregnation tank, the liquid level of the impregnation body exceeds the impregnation basket by 3~5mm, evacuate the vacuum degree below 0.09MPa for 15~45min, then slowly release the pressure to normal pressure, and continue impregnation for 3~5min; Drying: After the impregnation is completed, take out the impregnation basket and put it into the spin dryer to dry until there is no impregnation liquid flowing on the surface; Washing: Put the immersion basket into a washing tank containing clean water for washing. Shake the immersion basket up and down 3 to 8 times in the washing tank, and shake it left and right 3 to 8 times for one washing, and the washing time is 2 to 3 minutes. After completing one washing, change the water and wash again. Repeat the washing 3 to 8 times and drain the water after washing. Curing: Put the washed and drained PP parts into a constant temperature box and cure them at 80-90℃ for 20-60min. After curing, cool them naturally to room temperature to obtain a flame-retardant PP product with surface impregnation treatment. The post-processed flame-retardant impregnation body of the PP article comprises a dispersion medium and functional components dispersed in the dispersion medium, and the functional components comprise the following components by mass: Flame retardant, 100 parts by mass; Acid source and gas source, 5-11 parts by weight; Carbon-forming agent, 2.5-10 parts by weight; Film-forming agent, 8-14 parts by weight; The PP product is a molded product obtained by selective laser sintering of raw material powder containing PP; The flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the acid source and gas source are ammonium polyphosphate, which has the functions of both acid source and gas source; the carbon forming agent is hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene; and the film forming agent is polyvinyl alcohol formal; The dispersion medium is ethanol; The viscosity of the post-processed flame-retardant impregnation body of the PP product is 350-400 mPa•s.

2. The method for preparing the flame-retardant PP article according to claim 1, Features: The carbon-forming agent hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene is produced by a nucleophilic substitution reaction between hexachlorocyclotriphosphazene and 4,4-diaminodiphenyl sulfone.

3. The method for preparing the flame-retardant PP article according to claim 2, Features: The preparation method of the carbon-forming agent hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene comprises the following steps: Step 1.1: dissolving hexachlorocyclotriphosphazene in 1,4-dioxane, dissolving 4,4-diaminodiphenyl sulfone in acetone at a molar ratio of hexachlorocyclotriphosphazene to 4,4-diaminodiphenyl sulfone of 1:4, and adding the mixture dropwise to the 1,4-dioxane solution of hexachlorocyclotriphosphazene; Step 1.2: heating the mixed solution obtained in step 1.1 to 70-80°C and reacting for 24-48 hours to obtain a crude reaction product, hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene; Step 1.3: The crude reaction product hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene obtained in step 1.2 is cooled to room temperature, filtered, washed and dried to obtain the purified carbon-forming agent hexa(4,4-diaminodiphenyl sulfone)cyclotriphosphazene.

4. The method for preparing the flame-retardant PP article according to claim 1, Features: The preparation of the post-processed flame retardant impregnation body of PP parts includes the following steps: Step 2.1: dissolving 8 to 14 parts by weight of a film-forming agent, polyvinyl formal, in ethanol to obtain an ethanol solution of polyvinyl formal; Step 2.2: adding 100 parts by weight of flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the ethanol solution of polyvinyl alcohol acetal obtained in step 2.1, and mixing at 18-25° C. to obtain a DOPO-PVFA solution; Step 2.3: adding 5 to 11 parts by weight of ammonium polyphosphate and 2.5 to 10 parts by weight of a carbon-forming agent hexa(4,4-diaminodiphenylsulfone)cyclotriphosphazene to the above DOPO-PVFA solution, and mixing well to obtain a flame retardant impregnation solution; Step 2.4: Stir the flame retardant impregnation solution obtained in step 2.3 and heat it to 110°C-120°C to volatilize the ethanol until the viscosity of the flame retardant impregnation solution reaches 350-400 mPa•s, then stop heating to obtain a post-treated flame retardant impregnation body.

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