Polypropylene granule for 3D printing and preparation method and application thereof

Abstract

The invention provides a polypropylene material for 3D printing, which is prepared from the following raw materials in parts by weight: 30 to 80 parts of co-polypropylene, 1 to 15 parts of thermoplastic elastomer, 1 to 15 parts of UHMWPE (Ultra High Molecular Weight Polyethylene), 1 to 15 parts of adhesive, 10 to 40 parts of glass fiber, 5 to 30 parts of mineral powder, 0.5 to 5 parts of compatilizer and 0.1 to 1 part of nucleating agent, 0.1-1 part by weight of a main antioxidant, 0.1-1 part by weight of an auxiliary antioxidant and 0.1-1 part by weight of a lubricant. The polypropylene material has the advantages of high strength, high modulus, excellent thermal stability, high interlayer bonding force, small shrinkage warping, difficult cracking and deformation of printed products, and bright and clean appearance quality, and is suitable for particle 3D printing of large industrial molds.

Description

Technical Field

[0001] The present invention belongs to the field of polymer composites, and particularly relates to a polypropylene material, a preparation method thereof, and an application thereof. Background Art

[0002] Polypropylene (PP) has the advantages of low density, heat resistance, good insulation, chemical stability, low price, etc., and is widely used in the fields of household appliances, automobiles, electronics, etc. However, when applied to 3D printing, due to its high crystallinity and fast crystallization rate, there are problems such as serious warping deformation, poor interlayer adhesion resulting in sample cracking, poor dimensional accuracy, and rough appearance, which limit its application in the field of 3D printing. It is necessary to modify the polypropylene material to reduce the shrinkage rate and improve the interlayer adhesion in order to obtain a material suitable for 3D printing.

[0003] CN117700872A adds fibers to reduce the shrinkage rate of the material, but the anisotropy of the fibers is obvious. The shrinkage in the flow direction is indeed small, while the shrinkage in the direction perpendicular to the flow direction is large, which will cause uneven shrinkage of the product and warping deformation. CN109721928A uses polyester polyol as an adhesive to improve the interlayer bonding force, but cracking and warping problems still occur when printing industrial-grade and large samples over one meter, and the surface of the product is rough. CN111073160A uses dopamine-grafted acrylic acid-acrylate copolymer as an adhesive, and its bonding performance is greatly improved compared with the existing commercially available adhesives, but the compatibility of this material with polypropylene is poor, and the strength and rigidity of the product are insufficient. CN116218123A and CN117820770A adopt terpene resin tackifier systems, but the material properties are poor and cannot be applied to 3D printing large industrial molds. Summary of the Invention

[0004] Aiming at the above problems existing in the prior art, the purpose of the present invention is to provide a polypropylene pellet for 3D printing and a preparation method thereof. While having high strength, high modulus, and excellent thermal stability, this material has high interlayer bonding force, small shrinkage and warping, the printed product is not easy to crack and deform, and has a smooth appearance quality.

[0005] To achieve the above invention purpose, the present invention adopts the following technical solutions:

[0006] In the first aspect of the present invention, there is provided a polypropylene pellet for 3D printing, which is made of raw materials including the following parts by weight:

[0007] Copolypropylene 30 - 80 parts by weight, preferably 30 - 60 parts by weight;

[0008] Thermoplastic elastomer 1 - 15 parts by weight, preferably 5 - 10 parts by weight;

[0009] UHMWPE 1 - 15 parts by weight, preferably 3 - 10 parts by weight;

[0010] Binder 1 - 15 parts by weight, preferably 3 - 10 parts by weight;

[0011] Glass fiber 10 - 40 parts by weight, preferably 15 - 30 parts by weight;

[0012] Mineral powder 5 - 30 parts by weight, preferably 10 - 20 parts by weight;

[0013] Compatibilizer 0.5 - 5 parts by weight, preferably 2 - 4 parts by weight;

[0014] Nucleating agent 0.1 - 1 part by weight, preferably 0.3 - 0.8 part by weight;

[0015] Other additives 0.3 - 3 parts by weight, preferably 0.5 - 1.5 parts by weight.

[0016] In some preferred embodiments, the melt index of the copolymerized polypropylene under a load of 2.16 kg and at 230 °C is 10 - 100 g / 10 min, preferably 10 - 70 g / 10 min, such as 10 g / 10 min, 30 g / 10 min, 50 g / 10 min, 60 g / 10 min, 70 g / 10 min.

[0017] In some preferred embodiments, the thermoplastic elastomer is one or more of ethylene propylene diene monomer (EPDM), ethylene - butene copolymer, and ethylene - octene copolymer;

[0018] Preferably, the ethylene content in the ethylene propylene diene monomer is 40 - 80%, such as 50%, 60%, 70%, 75%, etc.; the melt index of the ethylene - butene copolymer and ethylene - octene copolymer under a load of 2.16 kg and at 190 °C is 0.5 - 30 g / 10 min, such as 1 g / 10 min, 5 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, etc.

[0019] In some preferred embodiments, the weight - average molecular weight of the UHMWPE is 1,000,000 - 4,000,000;

[0020] Adding UHMWPE can disrupt the crystallinity of polypropylene, reduce shrinkage and warpage. Its ultra-high molecular weight can improve the melt strength of the material, making the interlayer adhesion more excellent. At the same time, UHMWPE has an extremely low friction coefficient and excellent self-lubricity, making the surface of the composite material smoother. However, the blending effect of UHMWPE and PP is poor and it is difficult to disperse evenly. Thermoplastic elastomers have good affinity for both PP and UHMWPE, can form a linear interpenetrating network with the PP / UHMWPE system, play a compatibilizing role, improve the compatibility of each component, and enhance the toughness of the material.

[0021] In some preferred embodiments, the binder is an ethylene-hydroxytryptamine grafted methacrylic acid copolymer, and its molecular structural formula is as follows:

[0022]

[0023] Where x is the number of repeating units of ethylene and y is the number of repeating units of acrylic acid; the weight average molecular weight Mw = 4000 - 500000, preferably Mw = 10000 - 200000, such as 20000, 30000, 50000, 60000, 100000, 120000, 150000, etc.;

[0024] Preferably, the acrylic acid content of the binder is 5 - 15%, and the grafting rate of acrylic acid is 40 - 90%;

[0025] The binder has a low melting point and remains in a molten state for a long time during the printing process, which can improve the bonding effect between layers during the printing process. Compared with the existing commercially available binders, its bonding performance has been greatly improved. The ethylene chain segments in the structure are entangled with PP and the elastomer, enhancing the compatibility of the binder with the matrix. At the same time, its phenolic hydroxyl group, amino group and maleic anhydride grafted polypropylene, and mineral powder form hydrogen bonds with each other, improving the interfacial interaction between polar and non-polar components;

[0026] In a specific embodiment, the preparation method of the binder is:

[0027] Dissolve ethylene-acrylic acid copolymer and hydroxytryptamine in a sufficient amount of solvent (such as dichloromethane / dimethylformamide (1:1)), add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), 1-hydroxybenzotriazole (HOBT) and triethylamine, react at room temperature for a period of time (such as 12 - 24h), after the reaction is completed, wash the reaction solution with a sufficient amount of n-hexane for multiple times, and dry it under vacuum at 30 - 50°C for a period of time (such as 20 - 30h) to obtain the binder;

[0028] The hydroxytryptamine is 5-hydroxytryptamine or 5,6-dihydroxytryptamine;

[0029] Preferably, the mass ratio of the ethylene-acrylic acid copolymer, hydroxytryptamine, EDC, HOBT, and triethylamine is 1:(1-3):(0.5-1.5):(0.1-0.3):(0.2-0.4).

[0030] In some preferred embodiments, the length of the glass fiber is 2-10 mm.

[0031] In some preferred embodiments, the mineral powder is one or more of calcium carbonate, talc powder, mica, and whiskers, and the particle size is preferably 1000-7000 mesh.

[0032] In some preferred embodiments, the compatibilizer is maleic anhydride-grafted polypropylene, and the maleic anhydride content is 0.5-2 wt%.

[0033] In some preferred embodiments, the nucleating agent is one or more of sorbitol-based, phosphate-based, and rosin-based nucleating agents.

[0034] In some preferred embodiments, the other additives include antioxidants and lubricants; preferably, the dosages of each component are as follows:

[0035] The primary antioxidant is 0.1-1 part by weight, preferably 0.2-0.5 part by weight;

[0036] The secondary antioxidant is 0.1-1 part by weight, preferably 0.2-0.5 part by weight;

[0037] The lubricant is 0.1-1 part by weight, preferably 0.2-0.5 part by weight;

[0038] Preferably, the primary antioxidant is a hindered phenol antioxidant, preferably at least one of antioxidant 1010 (pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]) and antioxidant 1076 (octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate); the secondary antioxidant is a phosphite antioxidant, preferably at least one of antioxidant 168 (tris [2,4-di-tert-butylphenyl] phosphite) and antioxidant 626 (pentaerythritol bis [2,4-di-tert-butylphenyl] diphosphite); the lubricant is at least one of stearates and amide lubricants.

[0039] The second aspect of the present invention provides a method for preparing the above polypropylene material, comprising the following steps:

[0040] a. Mix other raw materials except glass fiber evenly to obtain a mixture;

[0041] b. Feed the above mixture into the main feeding port of a twin-screw extruder, add glass fiber from the side feeding port, melt and extrude, and pelletize to obtain the polypropylene material.

[0042] In some preferred embodiments, the extrusion temperature of the twin-screw extruder is 140 - 240 °C, the screw length-diameter ratio is (45 - 55) / 1, and the rotational speed is 400 - 800 revolutions per minute.

[0043] The third aspect of the present invention provides an application of the above-mentioned polypropylene material or the polypropylene material prepared by the above-mentioned preparation method as a granular 3D printing large industrial mold.

[0044] The technical solution provided by the present invention has the following beneficial effects:

[0045] 1. Adding UHMWPE can disrupt the crystallinity of polypropylene, reduce shrinkage and warpage. Its ultra-high molecular weight can improve the melt strength of the material, making the interlayer adhesion more excellent. At the same time, UHMWPE has an extremely low friction coefficient and excellent self-lubricity, making the surface of the composite material smoother. However, the blending effect of UHMWPE and PP is poor and it is difficult to disperse evenly. The thermoplastic elastomer has a good affinity for both PP and UHMWPE, can form a linear interpenetrating network with the PP / UHMWPE system, play a compatibilizing role, improve the compatibility of each component, and enhance the toughness of the material;

[0046] 2. The added binder has a low melting point and remains in a molten state for a long time during the printing process, which can improve the bonding effect between layers during the printing process. Compared with the commercially available binders, its bonding performance has been greatly improved. The ethylene segments in the structure are entangled with PP and the elastomer, enhancing the compatibility of the binder with the matrix. At the same time, its phenolic hydroxyl groups, amino groups and maleic anhydride grafted polypropylene and mineral powder form hydrogen bonds with each other, improving the interfacial interaction between polar and non-polar components;

[0047] 3. The polypropylene granule material obtained by the present invention has a simple preparation method, high production efficiency, and has the advantages of high strength, high modulus, excellent thermal stability, high interlayer bonding force, small shrinkage and warpage, the printed products are not easy to crack and deform, and the surface is smooth. It is particularly suitable for the application of 3D printing large industrial molds and has a broad market prospect. Specific Embodiments

[0048] To facilitate the understanding of the present invention, the present invention will be further described below in conjunction with embodiments. It should be understood that the following embodiments are only for better understanding of the present invention and do not mean that the present invention is limited only to the following embodiments.

[0049] Sources of Main Raw Materials

[0050] PP1: Copolypropylene, with a melt index of 28 g / 10 min under a load of 2.16 kg and at 230 °C;

[0051] PP2: Copolypropylene, with a melt index of 60 g / 10 min at a load of 2.16 kg and a temperature of 230 °C;

[0052] Elastomer 1: Ethylene propylene diene monomer rubber EPDM - 553, containing 60% ethylene;

[0053] Elastomer 2: Ethylene - butene copolymer, with a melt index of 5 g / 10 min at a load of 2.16 kg and a temperature of 190 °C;

[0054] UHMWPE - 1: Weight - average molecular weight of 3.7 million;

[0055] UHMWPE - 2: Weight - average molecular weight of 1.5 million;

[0056] Adhesive 1: Ethylene - (5 - hydroxytryptamine) grafted methyl methacrylate copolymer, the preparation method is as follows:

[0057] Dissolve 3 g of ethylene - acrylic acid copolymer and 6 g of 5 - hydroxytryptamine in 40 mL of dichloromethane / dimethylformamide (1:1) solvent, add 3 g of 1 - (3 - dimethylaminopropyl) - 3 - ethylcarbodiimide hydrochloride (EDC), 0.6 g of 1 - hydroxybenzotriazole (HOBT) and 0.9 g of triethylamine, react at room temperature for 24 h. After the reaction is completed, wash the reaction solution 3 times with 50 mL of n - hexane, and dry it under vacuum at 50 °C for 20 h to obtain the said Adhesive 1, with a weight - average molecular weight of 80,000.

[0058] Adhesive 2: Ethylene - (5,6 - dihydroxytryptamine) grafted methyl methacrylate copolymer, the preparation method is as follows:

[0059] Dissolve 3 g of ethylene - acrylic acid copolymer and 7.5 g of 5,6 - dihydroxytryptamine in 40 mL of dichloromethane / dimethylformamide (1:1) solvent, add 3 g of 1 - (3 - dimethylaminopropyl) - 3 - ethylcarbodiimide hydrochloride (EDC), 0.6 g of 1 - hydroxybenzotriazole (HOBT) and 0.9 g of triethylamine, react at room temperature for 24 h. After the reaction is completed, wash the reaction solution 3 times with 50 mL of n - hexane, and dry it under vacuum at 50 °C for 20 h to obtain the said Adhesive 2, with a weight - average molecular weight of 120,000.

[0060] Glass fiber: Fiber length 4.5 mm, commercially available;

[0061] Calcium carbonate: Mesh number 1000 mesh, commercially available;

[0062] Compatibilizer: GPM200A, commercially available;

[0063] Nucleating agent: TMY - 4, commercially available;

[0064] Primary antioxidant: Antioxidant 1010, commercially available;

[0065] Co - antioxidant: Irganox 168, commercially available;

[0066] Lubricant: Zinc stearate, commercially available.

[0067] All other raw materials are commercially available raw materials of analytical purity.

[0068] Main equipment:

[0069] Twin - screw extruder: The ratio of screw length to diameter is 52:1; JSW Co., Ltd.;

[0070] Injection molding machine: Kraussmaffei 200 750CX injection molding machine;

[0071] 3D printing equipment: Creative Three Emperor G5 pellet printer.

[0072] Main testing methods:

[0073] The polypropylene materials prepared in the following examples and comparative examples are respectively injection - molded into specimens for performance testing:

[0074] Density test is carried out according to ISO 1133 - 1:2011;

[0075] Tensile property test is carried out according to ISO 527 - 2 - 2012;

[0076] Flexural property test is carried out according to ISO 178 - 2019;

[0077] Izod notched impact strength test is carried out according to ISO 179 - 1 / 1eA - 2019;

[0078] Warpage property test: Inject a 150*300*3mm sample plate, test the shrinkage rates in the MD and TD directions, and visually observe the warpage degree;

[0079] Printing effect: Visually observe the moldability and appearance of the sample;

[0080] Adhesion property test: Use the polypropylene pellets obtained in the present invention to vertically print a 3D printing sample plate of 200mm×100mm, and then cut out a Type A tensile specimen required in ISO 527 - 2 - 2012 along the Z - axis (i.e., vertically) direction to test its tensile property.

[0081] Examples

[0082] Example 1

[0083] According to the formulation ratio of Example 1 in Table 1 (unit: g), mix the other raw materials except glass fiber evenly, feed them into the main feeding port of the twin-screw extruder, and at the same time add the glass fiber from the side feeding port, melt and extrude, and pelletize to obtain the polypropylene material. The temperature of the extruder is set as follows: Zone 1: 140 °C, Zones 2 and 3: 210 °C, Zones 4 - 6: 220 °C, Zones 7 and 8: 210 °C, and the screw speed is 500 revolutions per minute.

[0084] Examples 2 - 4

[0085] Prepare the polypropylene materials in Examples 2 - 4 respectively according to the method basically the same as that of Example 1, with the only difference being that the types and ratios of the raw materials are adjusted according to Table 1 (unit: g), and other parameters and operating conditions remain unchanged.

[0086] Comparative Examples

[0087] Comparative Examples 1 - 3

[0088] Prepare the polypropylene material according to the method basically the same as that of Example 1, and the usage amounts of the raw materials are as shown in Table 1.

[0089] Table 1 Raw material information and formulation ratios of Examples 1 - 4 and Comparative Examples 1 - 3

[0090] Raw materials Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 PP1 43 30 43 48 48 51 PP2 36 20 Elastomer 1 8 10 10 8 8 / Elastomer 2 8 UHMWPE-1 5 5 5 / 5 UHMWPE-2 5 5 Adhesive 1 5 5 / 5 5 Adhesive 2 5 5 Glass fiber 20 25 25 15 20 20 20 Calcium carbonate 15 15 5 20 15 15 15 Compatibilizer 3 3 3 2 3 3 3 Nucleating agent 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Primary antioxidant 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Secondary antioxidant 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Lubricant 0.2 0.2 0.2 0.2 0.2 0.2 0.2

[0091] Table 2 Properties of the polypropylene materials prepared in Examples 1 - 4 and Comparative Examples 1 - 3

[0092]

[0093] It can be seen from Examples 1 - 4 in Table 2 that under the action of the binder, UHMWPE, and elastomer, the material has good balance between rigidity and toughness, small difference in shrinkage rates in the MD and TD directions, and relatively light warping degree of the sample observed visually. When 3D printed into a flat plate, the surface of the sample is smooth and has no obvious defects. After cutting samples, the tensile strength and modulus are relatively high, indicating that the material has excellent interlayer bonding properties.

[0094] It can be seen from Comparative Examples 1 - 3 that when the binder is not added, the formability during 3D printing is very poor, and it is impossible to print completely, let alone test. When UHMWPE is not added, the 3D printed sample cracks, the surface is rough, and the performance is very poor after cutting samples. When the elastomer is not added, the toughness of the material decreases, the sample warps severely, and it is difficult to form during 3D printing, and the performance also decreases significantly after cutting samples.

[0095] A kind of polypropylene pellet material for 3D printing provided by the present invention has high strength, high modulus, excellent thermal stability, high interlayer bonding force, small shrinkage and warping, the printed product is not easy to crack and deform, and has a smooth appearance quality, and is suitable for the application of granule 3D printing of large industrial molds.

[0096] It is easy to understand that the above embodiments are merely examples given for clear illustration, and do not mean that the present invention is limited thereto. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A polypropylene material, characterized in that: The polypropylene material comprises the following raw materials in parts by weight: Copolymer polypropylene 30-80 parts by weight, preferably 30-60 parts by weight; Thermoplastic elastomer 1-15 parts by weight, preferably 5-10 parts by weight; UHMWPE 1-15 parts by weight, preferably 3-10 parts by weight; 1-15 parts by weight of adhesive, preferably 3-10 parts by weight; 10-40 parts by weight of glass fiber, preferably 15-30 parts by weight; 5-30 parts by weight of mineral powder, preferably 10-20 parts by weight; Compatibilizer 0.5-5 parts by weight, preferably 2-4 parts by weight; Nucleating agent 0.1-1 weight part, preferably 0.3-0.8 weight part; The other additives are 0.3-3 parts by weight, preferably 0.5-1.5 parts by weight.

2. The polypropylene material according to claim 1, characterized in that: The copolymerized polypropylene has a melt index of 10 to 100 g / 10 min, preferably 10 to 70 g / 10 min, at a load of 2.16 kg and 230° C.

3. The polypropylene material according to claim 1, characterized in that: The thermoplastic elastomer is one or more of EPDM, ethylene-butene copolymer and ethylene-octene copolymer; Preferably, the ethylene content of the EPDM rubber is 40-80%; the melt index of the ethylene-butene copolymer and the ethylene-octene copolymer at a load of 2.16 kg and 190° C. is 0.5-30 g / 10 min.

4. The polypropylene material according to claim 1, characterized in that: The weight average molecular weight of the UHMWPE is 1 to 4 million.

5. The polypropylene material according to claim 1, characterized in that: The adhesive is an ethylene-hydroxytryptamine grafted methacrylic acid copolymer, and the molecular structure is as follows: x is the number of repeating units of ethylene, y is the number of repeating units of acrylic acid, Mw=4000-500000, preferably Mw=10000-200000.

6. The polypropylene material according to claim 1, characterized in that: The glass fiber length is 2 to 10 mm; And / or: the mineral powder is one or more of calcium carbonate, talc, mica, whisker, and the particle size is preferably 1000-7000 mesh.

7. The polypropylene material according to claim 1, characterized in that: The compatibilizer is maleic anhydride grafted modified polypropylene, and the maleic anhydride content is 0.5-2wt%; And / or: the nucleating agent is one or more of sorbitol, phosphate and rosin nucleating agents.

8. The polypropylene material according to claim 1, characterized in that: The other additives include antioxidants and lubricants; preferably, the amount of each component is: Primary antioxidant 0.1-1 weight part, preferably 0.2-0.5 weight part; 0.1-1 weight part of secondary antioxidant, preferably 0.2-0.5 weight part; Lubricant 0.1-1 parts by weight, preferably 0.2-0.5 parts by weight; Preferably, the main antioxidant is a hindered phenol antioxidant, preferably antioxidant 1010 (tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester) and antioxidant 1076 (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl ester); the auxiliary antioxidant is a phosphite antioxidant, preferably antioxidant 168 (tris[2.4-di-tert-butylphenyl] phosphite) and antioxidant 626 (bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite); the lubricant is a stearate or an amide lubricant.

9. The method for preparing the polypropylene material according to any one of claims 1 to 8, characterized in that: The following steps are involved: a. Mixing the other raw materials except the glass fiber uniformly to obtain a mixture; b. The mixture was fed through the main feed port of a twin-screw extruder, glass fiber was added from the side feed port, melt extruded, and granulated to obtain a polypropylene material; Preferably, the extrusion temperature of the twin-screw extruder is 140-240° C., the screw aspect ratio is (45-55) / 1, and the rotation speed is 400-800 rpm.

10. Application of the polypropylene material according to any one of claims 1 to 8 in the field of 3D printing.

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