Micro-sized spherical polypropylene particles and methods of preparation; 3D printing raw materials and applications.

Abstract

Invention details;

Description

Polypropylene microspheres, preparation method thereof, 3D printing raw materials and uses thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present invention claims priority to the Chinese patent application entitled “A kind of polymerized synthetic polypropylene microspheres” and application number CN202111258205.6 filed on October 27, 2021. The entire contents of the application are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of polypropylene materials, and in particular to polypropylene microspheres, a preparation method thereof, 3D printing raw materials and uses thereof. Background Art

[0004] 3D printing, also known as "additive manufacturing," is a form of rapid prototyping technology. It uses a 3D printer to create an object using materials such as metal powder or plastic, layer by layer, following a digital blueprint. This technology enables on-demand, anytime, anywhere production, and has applications in everyday products such as footwear, construction, the automotive industry, aerospace, healthcare, and education. This emerging technology is steadily transforming human life, and its prospects are promising across various industries. Time magazine ranked 3D printing first among the "10 fastest-growing industries in the United States." The British magazine The Economist believes that 3D printing will drive the third industrial revolution.

[0005] Selective Laser Sintering (SLS) is a rapid prototyping technology that is currently the most widely used and promising additive manufacturing technology, and has shown rapid growth in recent years. SLS involves computer scanning of a three-dimensional solid. High-intensity laser irradiation then selectively melts and sinters a layer of powdered material, pre-applied to a workbench or component, to achieve layer-by-layer molding. SLS offers a high degree of design flexibility, enabling the production of precise models and prototypes, and the formation of reliable, ready-to-use components. It also shortens production cycles and simplifies processes, making it particularly suitable for new product development.

[0006] In theory, a wide range of molding materials can be used in SLS technology, such as polymers, paraffin wax, metals, ceramics, and their composites. However, the performance and properties of the molding material are an important factor in the successful sintering of SLS technology, which directly affects the molding speed, precision, physical and chemical properties, and overall performance of the molded parts. Currently, polymer powder raw materials that can be directly applied to SLS technology and successfully produce molded products with small dimensional errors, regular surfaces, and low porosity are rare on the market. Therefore, there is an urgent need to develop and improve the types of polymers suitable for SLS technology and their corresponding solid powder raw materials.

[0007] In the prior art, pulverization methods, such as cryogenic pulverization, are commonly used to prepare powder raw materials suitable for SLS. For example, CN104031319A discloses a polypropylene powder obtained using cryogenic pulverization. However, this method not only requires specialized equipment but also produces raw powder raw materials with rough surfaces, uneven particle size, and irregular shapes, which are not conducive to the formation of sintered compacts and affect the performance of the compacts.

[0008] Precipitation methods are also used to prepare polymer powder raw materials, such as polyamide powder. In this method, the polyamide is typically dissolved in a suitable solvent, stirred to evenly distribute the material in the solvent, and cooled to precipitate a powder. For example, CN103374223A discloses a precipitated polymer powder based on an AABB-type polyamide. This powder is obtained by reprecipitating the polyamide obtained by the polycondensation of a diamine and a dicarboxylic acid. The method described in this patent uses an alcoholic solvent during the reprecipitation process. However, this method requires the use of a large amount of organic solvent, has low yield and efficiency, and lacks environmental and economic advantages.

[0009] When the polymer is polypropylene, due to its production characteristics, conventional polymer microparticle preparation methods such as emulsion polymerization, soap-free emulsion polymerization, microemulsion polymerization, miniemulsion polymerization, suspension polymerization, dispersion polymerization, precipitation polymerization, and seed polymerization cannot be used. Instead, the material's low-temperature brittleness can be exploited to crush it into a micron-sized powder at low temperatures. However, pulverizing polyolefins often requires relatively expensive cryogenic treatment with liquid nitrogen. The most significant drawback is the poor morphology of the resulting powder, with irregular shapes and poor flowability. During SLS sintering, polymer microparticles must be layered and then sintered. However, using such irregularly shaped and poorly flowable particles makes spreading extremely difficult, rendering printing impossible. The more uniform the polymer's crystalline composition, the higher the melt flow rate index, which facilitates uniform melting during printing and improves the structural stability of the printed part. Therefore, there is an urgent need for polypropylene microspheres with excellent flowability and morphology to meet practical needs.

[0010] Polypropylene foam materials offer advantages such as low density, high specific strength, good thermal stability, excellent impact resistance, environmentally friendly raw materials and processes, and easy recycling. They can be used as functional materials for cushioning, shock absorption, sound insulation, and thermal insulation. Currently, common polypropylene foam materials can be categorized into four types based on the processing techniques: autoclave foaming, molded foaming, extrusion foaming, and injection molding. In addition to sharing the common advantages of polypropylene foam materials, autoclave foamed polypropylene (EPP) beads and molded bodies possess the most significant advantage of free formability. EPP beads can be molded to create foamed products with complex geometries and high three-dimensional dimensional precision. Polypropylene foam particle molded products offer excellent rigidity and impact resistance compared to polystyrene. Furthermore, unlike polystyrene foam, which is difficult to recycle, polypropylene foam is an environmentally friendly material with a high heat deformation temperature, suitable for use in certain high-temperature applications. It also possesses excellent energy absorption properties and superior compressive energy absorption, along with excellent dimensional and shape recovery stability, allowing products to withstand repeated impacts and flexing without permanent deformation. Furthermore, polypropylene foam products have a low density and are easily recyclable. They are non-toxic and do not produce toxic substances when burned. These excellent properties have led to its widespread application in packaging, automotive, construction, and other fields, with its applications continuously expanding. It is particularly well-suited for high-end applications such as automotive interior and exterior trim, cold chain logistics, and electronics packaging.

[0011] For EPP beads, in-mold secondary molding performance is crucial. This requires selecting polypropylene microparticles with a regular shape (preferably approximately spherical) and a small particle size as the foaming raw material. Regular spherical microparticles produce foamed beads that are also approximately spherical, facilitating dense packing during the molding process and preventing the formation of large pores. The production of polypropylene foam particles also requires the relatively costly cryogenic treatment with liquid nitrogen for pulverization, resulting in poor powder morphology, irregular shapes, and poor flowability. This can easily cause particle bridging during transport, leading to unstable production. Furthermore, such pulverized particles often lead to uneven foaming, a rough surface, and a whitening effect. At the same expansion ratio, smaller PP microparticles result in smaller foamed beads, facilitating transport of EPP beads through the molding equipment's process piping, reducing clogging and enabling dense packing within the mold cavity. This results in better bonding between beads during molding, reduced steam usage, and improved mechanical and thermal insulation properties of the finished product. Furthermore, a smaller particle size facilitates the production of thin-walled, complexly structured products, resulting in a smoother and more even surface.

[0012] Conventional strand pelletizing and underwater pelletizing methods often struggle to produce particles with a diameter below 0.5mm, often resulting in a high aspect ratio. To obtain microparticles with an average particle size below 0.5mm, the relatively expensive liquid nitrogen cryogenic treatment method is often required for pulverization. This results in poor powder morphology, irregular shapes, and poor fluidity, making it easy for particles to form bridges during transport, leading to unstable production. Furthermore, such pulverized particles often result in uneven foaming, a rough surface, and a whitening effect.

[0013] The crystallization distribution of polypropylene prepared using ZN catalyst often has greater dispersion, which is reflected in the relatively wide half-peak width in the DSC test results. The crystallization distribution of polypropylene prepared using metallocene catalyst is more uniform, but the molecular weight distribution of the latter is narrower, which often makes its product processing performance poor. The molecular weight distribution of the product obtained by the former is wider, which is more conducive to improving the rigidity and toughness balance of the resin.

[0014] Therefore, it is of great practical significance to develop a method for preparing polypropylene microspheres with good fluidity and morphology that can be used for 3D printing and foaming materials.

[0015] Summary of the Invention

[0016] In order to solve the technical problem in the prior art that polypropylene microspheres have poor uniformity in crystallization sequence distribution and poor product quality when melted uniformly when used for 3D printing, the present invention proposes polypropylene microspheres and a preparation method thereof.

[0017] According to a first aspect of the present invention, there are provided polypropylene microspheres, comprising 0.2 wt% to 10 wt% of structural units derived from ethylene and 90 wt% to 99.8 wt% of structural units derived from propylene, wherein a melting endothermic curve of the polypropylene microspheres is obtained by differential scanning calorimetry (DSC), and a half-peak width (Wm) of the melting endothermic curve of the polypropylene microspheres is 4 to 10°C.

[0018] Optionally, the half-peak width of the melting endothermic curve of the polypropylene microspheres is 5 to 8°C.

[0019] Optionally, the molecular weight distribution (Mw / Mn) of the polypropylene microspheres is 4-9.

[0020] Optionally, the molecular weight distribution of the polypropylene microspheres is 5, 6, 7, 8, or any value between any two of the above points.

[0021] Optionally, the bulk density of the polypropylene microspheres is 0.20 g / cm 3 ~0.50g / cm 3 , preferably 0.32 g / cm 3 ~0.48g / cm 3 .

[0022] Optionally, the angle of repose of the polypropylene microspheres is 10° to 23°, preferably 13° to 20°.

[0023] Optionally, the isotactic index of the polypropylene microspheres is 60% to 94%, preferably 64% to 90%.

[0024] Optionally, the ash content of the polypropylene microspheres is 0.005% to 0.04%.

[0025] Optionally, the ash content of the polypropylene microspheres is 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, or any value between any two of the above points.

[0026] Optionally, the polypropylene microspheres have a melt index of 3 to 160 g / 10 min, preferably 15 to 100 g / 10 min.

[0027] Optionally, when performing a DSC test, the DSC result satisfies the following characteristics: λi=(dH / dt) i+1 -(dH / dt) i ,λi≮0(i satisfies T m <T i <T fm ), where the ordinate is the heat flow rate dH / dt and the abscissa is the temperature T.

[0028] In the melting endothermic curve obtained by DSC testing, the endothermic effect is characterized by a raised peak (increase in thermal enthalpy).

[0029] DSC uses a Perkin-Elmer DSC-7 differential scanning calorimeter. The sample is heated to 200°C at 10°C / min, held for 5 minutes, then reduced to 50°C at 10°C / min, held at 50°C for 1 minute, and then increased to 200°C at 10°C / min. The DSC schematic is shown in Figure 2. The vertical axis of the DSC result is the dH / dt heat flow rate, and the horizontal axis is the temperature (T). The endothermic effect is characterized by a raised peak (increase in thermal enthalpy). The heating curve is the curve of the second heating as the result (usually the second heating curve is used to eliminate the thermal history of the test sample). As usually expressed, T m Indicates the melting point of the test sample, T fm Indicates the temperature where the melting peak joins the baseline.

[0030] The polymer microspheres obtained by the present invention, which have a narrower half-width, can significantly improve the expansion ratio and uniformity of EPP beads during autoclave foaming and molding. They can also be molded at lower temperatures, reducing energy consumption during EPP bead molding and accelerating the production cycle of EPP bead molding, thereby effectively reducing the production cost of EPP beads and molded bodies. Furthermore, EPP bead molded bodies prepared using these beads have superior appearance quality, making them particularly advantageous for preparing thin-walled or complex-shaped EPP molded products.

[0031] Optionally, the average particle size of the polypropylene microspheres is 50 μm to 200 μm; preferably, the average particle size of the polypropylene microspheres is 60 μm to 160 μm; most preferably, the average particle size of the polypropylene microspheres is 80 μm to 120 μm.

[0032] Optionally, the aspect ratio of the polypropylene microspheres is 0.9 to 1.1; preferably, the aspect ratio of the polypropylene microspheres is 0.95 to 1.05; most preferably, the aspect ratio of the polypropylene microspheres is 1.

[0033] As a specific embodiment of the present invention, the polypropylene microspheres are prepared by direct copolymerization.

[0034] According to a second aspect of the present invention, there is provided a method for preparing the polypropylene microspheres, comprising: copolymerizing olefins containing propylene in the presence of an olefin polymerization catalyst system to obtain polypropylene microspheres.

[0035] Alternatively, the olefin polymerization catalyst system comprises the following components or the reaction product of the following components: a catalyst, an alkyl aluminum compound, and an external electron donor compound which may be added or not.

[0036] The aluminum alkyl compound may be any of various aluminum alkyl compounds commonly used in the field of olefin polymerization that can be used as a co-catalyst for a Ziegler-Natta catalyst.

[0037] Alternatively, the alkylaluminum compound may be, but is not limited to, at least one of trimethylaluminum, triethylaluminum, triisobutylaluminum, trioctylaluminum, diethylaluminum monohydrogen, diisobutylaluminum monohydrogen, diethylaluminum monochloride, diisobutylaluminum monochloride, ethylaluminum sesquichloride, and ethylaluminum dichloride.

[0038] The external electron donor compound can be any external electron donor compound commonly used in the field of olefin polymerization that can be used as a co-catalyst for Ziegler-Natta catalysts.

[0039] Alternatively, the external electron donor compound may be, but is not limited to, trimethylmethoxysilane, trimethylethoxysilane, trimethylphenoxytriethylmethoxysilane, triethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, ethylisopropyldimethoxysilane, propylisopropyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, isopropylisobutyldimethoxysilane, di-tert-butyldimethoxysilane, tert-butylmethyldimethoxysilane, tert-butylethyldimethoxysilane, tert-butylpropyldimethoxysilane, tert-butylisopropyldimethoxysilane, tert-butyl Butyldimethoxysilane, tert-butylisobutyldimethoxysilane, tert-butyl(sec-butyl)dimethoxysilane, tert-butylpentyldimethoxysilane, tert-butylnonyldimethoxysilane, tert-butylhexyldimethoxysilane, tert-butylheptyldimethoxysilane, tert-butyloctyldimethoxysilane, tert-butyldecyldimethoxysilane, tert-butylmethyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane, cyclohexylpropyldimethoxysilane, cyclohexylisobutyldimethoxysilane, dicyclohexyldimethoxysilane, tert-butylcyclohexyldimethoxysilane, cyclopentylmethyldimethoxysilane , cyclopentylethyldimethoxysilane, cyclopentylpropyldimethoxysilane, cyclopentyltert-butyldimethoxysilane, dicyclopentyldimethoxysilane, cyclopentylcyclohexyldimethoxysilane, bis(2-methylcyclopentyl)dimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, isopropyltrimethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, isobutyltrimethoxysilane, tert-butyltrimethoxysilane, sec-butyltrimethoxysilane At least one of methoxysilane, amyltrimethoxysilane, isopentyltrimethoxysilane, cyclopentyltrimethoxysilane, cyclohexyltrimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, 2-ethylpiperidinyl-2-tert-butyldimethoxysilane, (1,1,1-trifluoro-2-propyl)-2-ethylpiperidinyldimethoxysilane and (1,1,1-trifluoro-2-propyl)-methyldimethoxysilane. More preferably, the external electron donor compound may be at least one of dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, cyclohexylmethyldimethoxysilane, methyl-tert-butyldimethoxysilane and tetramethoxysilane.

[0040] Optionally, the catalyst comprises a magnesium-containing compound support, a titanium compound and an internal electron donor compound.

[0041] Optionally, the molar ratio of the titanium compound, the magnesium-containing compound carrier, and the internal electron donor compound is (37-255):(2-15):1, preferably (67-235):(4-12):1.

[0042] Optionally, the structure of the magnesium-containing compound carrier is as shown in formula (I);

[0043]

[0044] In formula (I), R1 is an alkyl group of C1-C 10 ;

[0045] R2 and R3 are the same or different and are each independently H, an alkyl group of C1-C 10 or a C1-C 10 haloalkyl group substituted by 1-10 halogen atoms;

[0046] R4 is a C1-C 10 haloalkyl group substituted by at least one halogen atom or a C6-C 20 haloaryl group substituted by at least one halogen atom;

[0047] R5 is an alkyl group of C1-C5;

[0048] X is fluorine, chlorine, bromine or iodine; preferably, X is chlorine or bromine; [[ID=3G]]

[0049] m is 0.1-1.9, n is 0.1-1.9, and m + n = 2; preferably, m is 0.8-1.2 and n is 0.8-1.2;

[0050] 0 < q < 0.2; 0 < a < 0.1; preferably, 0.005 ≤ q ≤ 0.2; 0.001 < a < 0.05.

[0051] Optionally, the internal electron donor compound is selected from at least one of carboxylic acid esters, alcohol esters, ethers, ketones, nitriles, amines and silanes, preferably at least one of mono- or polyvalent aliphatic carboxylic acid esters, mono- or polyvalent aromatic carboxylic acid esters, diol esters and diethers.

[0052] Optionally, the diol ester can be a carboxylic acid diol ester.

[0053] Optionally, the internal electron donor compound is at least one of diethers, and the structure of the diether is as shown in formula (Ⅲ):

[0054]

[0055] Wherein, R 21 and R 22 are each independently selected from hydrogen, C1-C 20Alkyl, C3-C 20 Cycloalkyl, C6-C 20 Aryl, C7-C 20 Arylalkyl or C7-C 20 The alkylaryl group, R 21 and R 22 They may be optionally linked to form a ring; R 23 and R 24 Each independently is C1-C 10 of alkyl.

[0056] Specifically, the internal electron donor compound can be selected from 2-(2-ethylhexyl)-1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-1,3-dimethoxypropane, 2-phenyl-1,3-dimethoxypropane, 2-(2-phenylethyl)-1,3-dimethoxypropane, 2-(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-(p-chlorophenyl)-1,3-dimethoxypropane, 2-(diphenylmethyl)-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane , 2,2-dicyclopentyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2,2-diisopropyl-1,3-dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl-2-benzyl-1,3-dimethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2-methyl-2-phenyl-1,3-dimethoxypropane, 2-methyl-2-cyclohexyl-1,3-dimethoxypropane, 2, 2-bis(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2-methyl-2-(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-diphenyl-1,3-dimethoxypropane, 2,2-dibenzyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2-(1-methylbutyl)-2-isopropyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane , 2-phenyl-2-isopropyl-1,3-dimethoxypropane, 2-phenyl-2-sec-butyl-1,3-dimethoxypropane, 2-benzyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclopentyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclopentyl-2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-2-isopropyl-1,3-dimethoxypropane, 2-cyclohexyl-2-sec-butyl-1,3-dimethoxypropane, 2-isopropyl-2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane and at least one of 9,9-dimethoxymethylfluorene.

[0057] Optionally, the general formula of the titanium compound is Ti(OR6) 4-b X' b , where R6 is C1-C14 wherein X' is F, Cl or Br, and b is an integer of 1 to 4.

[0058] The titanium compound is preferably at least one of titanium tetrachloride, titanium tetrabromide, titanium tetrafluoride, tributoxytitanium chloride, dibutoxytitanium dichloride, butoxytitanium chloride, triethoxytitanium chloride, diethoxytitanium dichloride and ethoxytitanium chloride.

[0059] Optionally, the method for preparing the magnesium-containing compound carrier comprises the following steps:

[0060] S1: contacting and emulsifying a magnesium halide of the general formula MgX"Y and a first alcohol compound of the general formula R7OH for the first time to obtain a first product;

[0061] S2: contacting the first product with the oxirane compound having the structure represented by formula (II) for a second time to obtain a second product;

[0062] S3: The product containing the general formula R 10 OH halohydrin, general formula R 11 The second alcohol compound containing OH is contacted with the second product for a third time to obtain a third product;

[0063] S4: spray-drying the third product to obtain a magnesium-containing compound carrier.

[0064] Alternatively, as a specific embodiment of the present invention, in said S1, in said general formula MgX"Y, X" is selected from fluorine, chlorine, bromine or iodine; Y is selected from fluorine, chlorine, bromine, iodine, C 1-6 Alkyl, C 1-6 Alkoxy, C 6-14 Aryl or C 6-14 of aryloxy.

[0065] Preferably, X is selected from chlorine or bromine, and Y is selected from chlorine, bromine, C 1-5 Alkyl, C 1-5 Alkoxy, C 6-10 Aryl or C 6-10 When Y is selected from C 1-6 Alkyl, C 1-6 When the alkoxy group is C, the alkyl group and the alkoxy group are straight-chain or branched alkyl and alkoxy groups; 1-6 The alkyl group refers to an alkyl group having 1 to 6 carbon atoms, including but not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, etc.; the C 1-6The alkoxy group refers to an alkoxy group having 1 to 6 carbon atoms, including but not limited to methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, etc.

[0066] The C 6-14 The aryl group refers to an aryl group having 6 to 14 carbon atoms, including but not limited to phenyl, o-tolyl, m-tolyl, p-tolyl, o-ethylphenyl, m-ethylphenyl, p-ethylphenyl, naphthyl, and the like.

[0067] The C 6-14 The aryloxy group refers to an aryloxy group having 6 to 14 carbon atoms, including but not limited to phenoxy, naphthoxy, o-methylphenoxy, o-ethylphenoxy, m-methylphenoxy and the like.

[0068] Optionally, the magnesium halide is at least one selected from magnesium chloride, magnesium bromide, phenoxymagnesium chloride, isopropoxymagnesium chloride and n-butoxymagnesium chloride, preferably magnesium chloride.

[0069] Optionally, in the formula R7OH, R7 is C 1-10 of alkyl.

[0070] Optionally, in S2, the structural formula of the ethylene oxide compound is as shown in formula (II),

[0071]

[0072] Wherein, R8 and R9 are each independently selected from H, C 1-10 Alkyl, C substituted by 1 to 10 halogen atoms 1-10 Preferably, R8 and R9 are each independently selected from H, C 1-5 Alkyl, C substituted by 1 to 10 halogen atoms 1-5 of a halogenated alkyl group.

[0073] Optionally, the oxirane compound is at least one selected from ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epichlorohydrin, epibromohydrin and epibromobutylene oxide.

[0074] Optionally, in said S3, said formula R 10 OH, R 10 Selected from C substituted by at least one halogen atom 1-10 or a C 6-20 of a halogenated aromatic group.

[0075] The halohydrin may be a monohalohydrin or a polyhalohydrin, preferably a chlorohydrin, a bromohydrin or an iodohydrin, for example, 2,2,2-trichloroethanol, 2,2-dichloroethanol, 2-chloroethanol, 3-chloro-1-propanol, 6-chloro-1-hexanol, 3-bromo-1-propanol, 5-chloro-1-pentanol, 4-chloro-1-butanol, 2-chlorocyclohexanol, 1,2-dichloroethanol, 1,3-dichloropropanol, 1,4-dichlorobutanol or 2-iodoethanol.

[0076] However, in order to obtain a catalyst support with better performance, according to another preferred embodiment of the present invention, in formula R 10 OH, R 10 Selected from C substituted by at least two halogen atoms 1-10 or a C 6-20 The halogenated aromatic group is a halogenated aromatic group, wherein the halogen atom is selected from at least one of a chlorine atom, a bromine atom and an iodine atom.

[0077] Preferably, the halogenated alcohol is selected from at least one of 2,2,2-trichloroethanol, 2,2-dichloroethanol, 1,2-dichloroethanol, 1,3-dichloropropanol and 1,4-dichlorobutanol.

[0078] Optionally, the formula R 11 OH, R 11 C 1-5 of alkyl.

[0079] In the present invention, the second alcohol compound is ethanol, methanol, n-propanol, isopropanol, n-butanol or isobutanol. However, in order to obtain a catalyst support with better performance, according to another preferred embodiment of the present invention, in formula R 11 OH, R 11 C 1-2 The alkyl group, that is, the second alcohol compound is methanol and / or ethanol.

[0080] Optionally, relative to 1 mol of the magnesium halide, the amount of the halohydrin used is 0.05 to 6.5 mol, and the amount of the second alcohol compound used is 5 to 100 mol.

[0081] When the amount of the halohydrin compound used is too large, the resulting catalyst carrier will form sticky blocks and subsequent operations cannot be performed.

[0082] Optionally, relative to 1 mol of the magnesium halide, the amount of the first alcohol compound used is 1 to 30 mol, and the amount of the ethylene oxide compound used is 1 to 10 mol.

[0083] Preferably, relative to 1 mol of the magnesium halide, the amount of the first alcohol compound is 6-22 mol, the amount of the ethylene oxide compound is 2-6 mol, the amount of the halohydrin is 1-5 mol, and the amount of the second alcohol compound is 8-80 mol, more preferably 31-50 mol.

[0084] It should be noted that the trace amount of water carried by the above-mentioned reactants will also participate in the reaction to form the spherical carrier. Therefore, the prepared spherical carrier may contain trace amounts of water from the reaction raw materials and the reaction medium, which should not be understood by those skilled in the art as a limitation of the present invention.

[0085] Optionally, the first contact in S1 is carried out under stirring conditions, and the conditions for the first contact include: temperature of 80-120°C and time of 0.5-5h; preferably, in S1, the conditions for the first contact include: temperature of 80-100°C and time of 0.5-3h.

[0086] In S1, the present invention does not particularly limit the specific operation method of the emulsification, and it can be carried out by methods known to those skilled in the art. For example, low-speed shear or high-speed shear is used for emulsification. Preferably, when low-speed shear is used, the stirring rate of the low-speed shear is 400-800 rpm. The high-speed shear method is well known to those skilled in the art, for example, it is carried out using the high-speed stirring speed disclosed in CN1330086A. In addition, the emulsification operation can also be carried out with reference to the methods disclosed in the following patent applications, such as CN1580136A discloses that a solution containing a liquid magnesium halide compound is subjected to rotational dispersion in a supergravity bed (the rotation speed is 100-3000 rpm); CN1463990A discloses that a solution containing a liquid magnesium halide adduct is output in an emulsifier at a speed of 1500-8000 rpm; and US6020279A discloses that a solution containing a liquid magnesium halide adduct is emulsified by a spray method.

[0087] Optionally, in S2, the second contact conditions include: temperature of 50-120°C, time of 20-60 min; preferably, the second contact conditions include: temperature of 80-100°C, time of 20-50 min.

[0088] Optionally, S3 further includes washing the second product with an inert solvent and then mixing with a mixture containing a general formula R 10 OH halohydrin, general formula R 11 The third contact is carried out with a second alcohol compound containing OH; preferably, the inert solvent is selected from at least one of pentane, hexane, heptane, petroleum ether and gasoline.

[0089] The present invention has no particular restrictions on the specific conditions of the third contact in S3, as long as the conditions of the third contact containing the general formula R 10 OH halohydrin, general formula R 11 The second alcohol compound of OH and the second product can fully contact to form a fluid. However, in order to obtain a catalyst support with better performance; preferably, in S3, the third contacting conditions include: stirring, a temperature of 0 to 120°C, and a time of 0.5 to 6 hours.

[0090] The present invention has no particular limitation on the specific manner of the third contact in S3. The halohydrin and the second alcohol compound may be mixed and contacted with the second component simultaneously, or the halohydrin and the second alcohol compound may be contacted with the second component separately and in sequence.

[0091] As a specific embodiment of the present invention, in S4, the spray drying conditions can adopt existing conditions that can form a catalyst support for olefin polymerization. However, in order to obtain a catalyst support with better performance, according to a preferred specific embodiment of the present invention, the spray drying is carried out in a sprayer having an atomizing nozzle, wherein the atomizing nozzle includes a material conduit and a nozzle head. The third product is introduced into the nozzle head through the material conduit and sprayed into the tower body of the sprayer containing an inert medium through the nozzle head for solidification. Preferably, the temperature of the third product in the material conduit is between 0°C and 80°C, and the temperature of the third product in the nozzle head is between 80°C and 180°C; more preferably, the temperature of the third product in the nozzle head is between 120°C and 180°C.

[0092] Optionally, in S4, the spray drying conditions include: a temperature of 60 to 200° C., more preferably 90 to 150° C. In the present invention, the spray drying temperature refers to the temperature of the inert medium in the sprayer.

[0093] As a specific embodiment of the present invention, the inert medium may include a protective gas medium and / or an inert liquid medium. There is no particular limitation on the type of the protective gas medium. For example, it may be nitrogen, an inert gas medium such as helium, or other suitable gases such as carbon dioxide. The inert liquid medium is any liquid medium commonly used in the art that does not chemically react with the reactants and reaction products. Preferably, the inert liquid medium is silicone oil and / or an inert liquid hydrocarbon solvent. More preferably, the inert liquid medium is selected from at least one of kerosene, paraffin oil, vaseline oil, white oil, methyl silicone oil, ethyl silicone oil, methylethyl silicone oil, phenyl silicone oil and methylphenyl silicone oil, and is further preferably white oil.

[0094] As a specific embodiment of the present invention, the amount of the inert liquid medium in the sprayer can be selected according to the amount of the magnesium halide of the general formula MgX"Y, preferably 0.8 to 10 L, more preferably 2 to 8 L.

[0095] As a specific embodiment of the present invention, the preparation method described in the present invention also includes conventional post-processing means in the art such as solid-liquid separation, washing, drying, etc., and the present invention has no particular restrictions on this. The solid-liquid separation can adopt various existing methods that can achieve separation of solid and liquid phases, such as suction filtration, filter press or centrifugal separation, etc. Preferably, the method of solid-liquid separation is filter press. The present invention does not particularly limit the conditions for filter press, and the separation of solid and liquid phases is achieved as fully as possible. The washing can be carried out by washing the obtained solid phase product using methods well known to those skilled in the art, for example, the obtained solid phase product can be washed using an inert hydrocarbon solvent (such as pentane, hexane, heptane, petroleum ether and gasoline). The present invention has no particular restrictions on the specific conditions of the drying, for example, the drying temperature can be 20 to 70 ° C, the drying time can be 0.5 to 10 hours, and the drying can be carried out under normal pressure or reduced pressure.

[0096] As a specific embodiment of the present invention, the composition of the catalyst is not particularly limited and can be any composition of catalysts currently used in the art for olefin polymerization. However, in order to obtain a catalyst suitable for olefin polymerization, particularly propylene polymerization, the catalyst preferably contains the support, a titanium halide compound, and an electron donor compound. Preferably, the titanium halide compound is selected from at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tetra-n-butoxytitanium, tetraethoxytitanium, tri-n-butoxytitanium monochloride, di-n-butoxytitanium dichloride, mono-n-butoxytitanium trichloride, triethoxytitanium monochloride, diethoxytitanium dichloride, monoethoxytitanium trichloride, and titanium trichloride. Preferably, the electron donor compound is selected from at least one of diisobutyl phthalate, carboxylic acid glycol esters, and phosphate esters. Furthermore, the present invention does not particularly limit the content of the various components in the catalyst, and those skilled in the art can reasonably adjust and design the catalyst according to actual needs.

[0097] Optionally, the average particle diameter of the magnesium-containing compound carrier is 2 to 100 microns, and the particle size distribution is less than 2; preferably, the average particle diameter of the magnesium-containing compound carrier is 2 to 19 microns, and the particle size distribution is 0.6 to 1.6.

[0098] In order to obtain an olefin polymer with a higher bulk density when a catalyst containing a magnesium-containing compound carrier is used for olefin polymerization, it is further preferred that the average particle diameter of the magnesium-containing compound carrier is 2 to 10 microns and the particle size distribution is 0.6 to 1.

[0099] In the polypropylene microsphere preparation method of the present invention, the catalyst exhibits "morphology replication" properties during the catalytic propylene polymerization process. While spherical catalysts do not necessarily produce spherical polymers, spherical polymers can generally only be produced from spherical catalysts. Catalysts with smaller particle sizes generally produce smaller polymer particle sizes. Furthermore, the structure and morphology of the catalyst itself play a significant role in the polymer morphology. A favorable catalyst structure and morphology can help reduce friction between polymers, lowering the angle of repose of the final polymer, thereby facilitating polymer production and transport.

[0100] According to a third aspect of the present invention, a 3D printing material is provided, comprising: the above-mentioned polypropylene microspheres and / or the polypropylene microspheres prepared according to the above-mentioned preparation method.

[0101] According to a fourth aspect of the present invention, there is provided a use of the above-mentioned polypropylene microspheres or the polypropylene microspheres prepared according to the above-mentioned preparation method for 3D printing, especially for laser sintering printing, and most preferably for selective laser sintering (SLS).

[0102] Compared with the prior art, the present invention has the following beneficial effects:

[0103] 1. The half-peak width of existing ordinary polypropylene microspheres is relatively wide, while the half-peak width of the polypropylene microspheres of the present invention is only 4 to 10°C, which is narrower than the existing ones. This shows that the crystallization sequence distribution of the obtained polypropylene microspheres is relatively uniform. When used in 3D printing, it can improve the uniformity of polymer particle melting and fusion, and can make the 3D printed melt-uniform products have good performance, and improve the structural strength and surface properties of the sintered samples. At the same time, compared with the polypropylene microspheres prepared by metallocene catalysts, the present invention has a wider molecular weight distribution, so that the resulting sintered products have a better balance of rigidity and toughness.

[0104] 2. The polypropylene microspheres of the present invention have an average particle size of less than 160 microns and can be used directly in 3D printing without secondary processing. Their angle of repose is less than 23°, providing improved fluidity and more uniform powder distribution during printing. Their ethylene content is greater than 0.2 wt%, preventing warping during 3D printing. These polypropylene microspheres exhibit a well-defined spherical morphology, regular particles, and excellent fluidity, demonstrating promising industrial applications.

[0105] 3. The method for preparing polypropylene microspheres of the present invention has a catalyst with a large specific surface area and good polymerization activity. At the same time, due to the characteristics of the catalyst, the use of alkyl aluminum can be reduced. A smaller amount of triethyl aluminum is used to react with cyclohexylmethyldimethoxysilane, a catalyst, hydrogen and propylene monomer to obtain polypropylene microspheres, so that the ash content of the obtained polymer microspheres is further reduced and there is basically no irregular shape.

[0106] 4. In the method for preparing polypropylene microspheres of the present invention, spherical polymers are directly polymerized through the "morphology replication" property of the catalyst; due to the good structure and morphology of the catalyst, the friction between the obtained polymers is small, and the angle of repose of the polymers is small, which is beneficial to the production and transmission of the polymers.

[0107] 5. The polypropylene microspheres provided by the present invention are obtained by direct polymerization in a reactor, thus avoiding the need for post-processing and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] FIG1 is an electron microscope image of the polypropylene powder obtained in Example 1-1.

[0109] Figure 2 is a schematic diagram of DSC. DETAILED DESCRIPTION

[0110] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0111] In the present invention, the average particle diameter and particle size distribution of the magnesium-containing compound carrier are measured using a Masters Sizer 2000 particle size analyzer (manufactured by Malvern Instruments Ltd).

[0112] In the present invention, the surface morphology of the polypropylene powder is observed by using an XL-30 field emission electron microscope produced by FEI Company of the United States.

[0113] In the present invention, the structure and composition of the magnesium-containing compound carrier are obtained by performing 1H-NMR testing on the carrier using an AVANCE 300 nuclear magnetic resonance spectrometer from Bruker, Switzerland, and by testing the carrier using a PY-2020iD cracker from Fronteerlab, a TraceGC Ultra chromatograph from Thermo Fisher, and a DSDⅡ mass spectrometer.

[0114] In the present invention, DSC testing is performed using the method specified in GBT 19466 Plastics Differential Scanning Calorimetry (DSC). The half-width (FWHM) of DSC testing refers to the absolute value of the temperature difference between the two points on either side of the peak where a straight line parallel to the baseline, drawn through the midpoint of the peak height, intersects the line.

[0115] In the present invention, the molecular weight distribution index Mw / Mn of the polypropylene powder is measured by the method specified in GB / T36214-2018.

[0116] In the present invention, the copolymerization activity of the catalyst is evaluated by the ratio of the weight of the product obtained after polymerization to the weight of the catalyst used.

[0117] In the present invention, the bulk density of the polypropylene powder is measured using the method specified in GB / T 1636-2008.

[0118] In the present invention, the ash content of the polypropylene powder is determined by the method specified in GB_T 9345.1-2008.

[0119] In the present invention, the specific surface area of ​​the polypropylene powder is tested using a POREMASTER GT60 mercury porosimeter.

[0120] In the present invention, the angle of repose of the polypropylene powder is measured using the method specified in GB / T 11986-1989.

[0121] In the present invention, the aspect ratio of the polypropylene powder refers to the ratio of the major axis of the particle projection to the average minor axis thereof.

[0122] In the present invention, the ethylene content of the polypropylene powder is determined by Fourier transform infrared spectrometer, and the sample is prepared by hot pressing film method.

[0123] In the present invention, the tensile strength of the spline is measured using the method specified in GB / T 1040.2-2006.

[0124] In this invention, surface smoothness is determined by a comparative method: the surface being tested is compared with a standard sample, and the roughness of the surface being tested is assessed by visual, tactile, or other methods. Five staff members perform the assessment, with the standard sample receiving a score of 10, and the average score is taken.

[0125] Score evaluation 1-2 Very bad 3-4 Poor 5-6 Average 7-8 Good 9-10 Good

[0126] In the present invention, unless otherwise specified, all raw materials used are commercially available products:

[0127] 1,3-Dichloropropanol was purchased from J&K Company;

[0128] Epichlorohydrin was purchased from J&K Company;

[0129] Diisobutyl phthalate was purchased from J&K Company;

[0130] Titanium tetrachloride was purchased from J&K;

[0131] Triethylaluminum was purchased from J&K;

[0132] Cyclohexylmethyldimethoxysilane was purchased from J&K Company.

[0133] In the various embodiments and comparative examples of the present invention, unless otherwise specified, during the preparation of the catalyst support, emulsification was performed under stirring at 600 rpm.

[0134] DSC was performed using a Perkin-Elmer DSC-7 differential scanning calorimeter. The sample was heated to 200°C at 10°C / min, held for 5 minutes, then reduced to 50°C at 10°C / min, held at 50°C for 1 minute, and then raised to 200°C at 10°C / min. The formula λi = (dH / dt) was used in the results of the second heating test. i+1 -(dH / dt) i Calculate λi≮0(i satisfies T m <T i <T fm If any of the results is less than 0, then λi≮0 is no; otherwise, if all the calculated values ​​are not less than 0, then λ i ≮0 means yes. λi is T i+1 Temperature and T i The difference in heat flow rate at temperature.

[0135] Example 1-1

[0136] 1) Preparation of magnesium-containing compound carrier

[0137] S1: In a 0.6 L reactor, 0.08 mol of magnesium chloride and 1.7 mol of ethanol (the first alcohol compound) were added in sequence, and the temperature was raised to 90°C under stirring. The mixture was kept at this temperature for 1 hour for the first contact, and then emulsified to obtain the first product;

[0138] S2: contacting the first product with 0.48 mol of epichlorohydrin for a second time to obtain a second product, wherein the conditions of the second contact include: temperature of 90° C. and time of 30 minutes;

[0139] S3: After the second product is filtered, it is thoroughly mixed with 2.5 mol of ethanol (second alcohol compound) and 0.35 mol of 1,3-dichloropropanol (halohydrin) by stirring to perform a third contact to form a fluid, thereby obtaining a third product;

[0140] S4: Use a sprayer B-290 containing a nozzle head and a material conduit to spray the third product into the circulating nitrogen at 100°C in the sprayer tower for spray drying. The temperature of the third product in the material conduit is 15°C, and the temperature in the nozzle head is 120°C to obtain a catalyst spherical carrier Z1.

[0141] According to tests, the average particle diameter (D50) of the catalyst spherical carrier Z1 is 4 microns, and the particle size distribution ((D90-D10) / D50) is 0.9.

[0142] Observation shows that the particle shape of the catalyst spherical carrier Z1 is relatively regular, the surface is smooth, and they are basically spherical. The particle size distribution is relatively concentrated, and there are basically no irregular particles.

[0143] During the preparation of the catalyst spherical carrier Z1, no clogging occurred at the nozzle head of the sprayer, and a total of 11.8 g of the catalyst spherical carrier Z1 was obtained.

[0144] 2) Preparation of catalysts for olefin polymerization

[0145] S1: Add 100 mL of titanium tetrachloride to a 300 mL reaction flask, cool to -20°C, add 8 g of the catalyst spherical carrier Z1 obtained in Example 1, and stir at -20°C for 30 min to obtain the first product;

[0146] S2: Slowly heat the first product obtained in S1 to 110°C, add 1.5 mL of 2-isopropyl-2-isopentyl-1,3-dimethoxypropane during the heating process, maintain the temperature at 110°C for 30 minutes, and filter out the liquid to obtain the second product;

[0147] S3: The second product obtained in S2 was washed twice with titanium tetrachloride and then three times with hexane, and dried to obtain catalyst C1 for olefin polymerization.

[0148] 3) Preparation of polypropylene copolymer microspheres

[0149] In a 5 L stainless steel autoclave, under a nitrogen atmosphere, 0.25 mmol of a hexane solution of triethylaluminum (the concentration of triethylaluminum is 0.5 mmol / mL), 10 mL of anhydrous hexane, 10 mg of catalyst C1, 1.5 L (standard volume) of hydrogen, and 2 L of liquid propylene monomer were added. Ethylene was introduced, the temperature was raised to 70°C, and the reaction was carried out at this temperature for 40 min. The temperature was then lowered, the pressure was released, the material was discharged, and the material was dried to obtain a copolymerized polypropylene powder.

[0150] The copolymerized polypropylene powder obtained in Example 1-1 exhibited a good spherical morphology as observed under an electron microscope ( FIG. 1 ), with substantially no irregularly shaped particles.

[0151] Example 1-2

[0152] This example uses the method provided in Example 1-1 to prepare polypropylene, except that the volume of hydrogen used is different, and all other aspects are the same.

[0153] Specifically: 1.5 L (standard volume) of hydrogen is replaced with 6.5 L (standard volume) of hydrogen to obtain polypropylene powder.

[0154] The polypropylene powder is observed to have a good spherical shape under an electron microscope, and there is basically no irregular shape.

[0155] Example 2-1

[0156] (1) In a 0.6 L reactor, 0.08 mol of magnesium chloride and 1.4 mol of ethanol (a first alcohol compound) were added, and the temperature was raised to 90° C. under stirring. The reaction was carried out at a constant temperature for 1.5 hours to perform a first contact, and then emulsified to obtain a first product;

[0157] (2) contacting the first product with 0.35 mol of epichlorohydrin for a second time to obtain a second product, wherein the conditions of the second contact include: temperature of 90° C. and time of 30 minutes;

[0158] (3) After the second product is filtered, it is fully mixed and stirred with 2.5 mol of ethanol (second alcohol compound) and 0.25 mol of 1,3-dichloropropanol (halohydrin) to form a fluid, thereby obtaining a third product;

[0159] (4) Using a sprayer B-290 containing a nozzle head and a material conduit, the third product is sprayed into the circulating nitrogen at 100°C in the sprayer tower for spray drying. The temperature of the third product in the material conduit is 15°C, and the temperature in the nozzle head is 120°C, to obtain a catalyst spherical carrier Z2.

[0160] According to tests, the average particle diameter (D50) of the catalyst spherical carrier Z2 is 4 microns, and the particle size distribution ((D90-D10) / D50) is 0.8.

[0161] Observation shows that the particles of the spherical carrier Z2 for olefin polymerization catalyst are relatively regular in shape, smooth in surface, and are basically spherical. The particle size distribution is relatively concentrated, and there are basically no irregular particles.

[0162] During the preparation of the catalyst spherical carrier Z2, no clogging occurred at the nozzle head of the sprayer, and a total of 11.9 g of the catalyst spherical carrier Z2 was obtained.

[0163] Polypropylene was prepared in a manner similar to that of Example 1-1, except that in step S1, the type of catalyst carrier used was different. The rest was the same as that of Example 1-1.

[0164] Specifically: the catalyst spherical carrier Z2 prepared in Example 2-1 is used in place of the catalyst spherical carrier Z1 to obtain the olefin polymerization catalyst C2;

[0165] The catalyst C2 was tested and observed under an electron microscope to be spherical. The average particle diameter (D50) of the catalyst C2 was 4 microns, and the particle size distribution ((D90-D10) / D50) was 0.8.

[0166] The obtained polypropylene powder particles have good morphology and are well spherical when viewed under an electron microscope, with almost no irregular particles.

[0167] Example 2-2

[0168] This example uses the method provided in Example 2-1 to prepare polypropylene, except that the volume of hydrogen used is different, and all other aspects are the same.

[0169] Specifically: 1.5 L (standard volume) of hydrogen is replaced with 6.5 L (standard volume) of hydrogen to obtain polypropylene powder.

[0170] The polypropylene powder is observed to have a good spherical shape under an electron microscope, and there is basically no irregular shape.

[0171] Example 3-1

[0172] (1) In a 0.6 L reactor, 0.08 mol of magnesium chloride and 1.4 mol of ethanol (a first alcohol compound) were added, and the temperature was raised to 90° C. under stirring. The mixture was kept at this temperature for 1.5 h for a first contact, and then emulsified to obtain a first product;

[0173] (2) contacting the first product with 0.35 mol of epichlorohydrin for a second time to obtain a second product, wherein the conditions of the second contact include: temperature of 90° C. and time of 30 min;

[0174] (3) After filter pressing, the second product is mixed with 2.5 mol of ethanol (second alcohol compound) and 0.1 mol of 1,3-dichloropropanol (halohydrin) and stirred until a third contact is performed to form a fluid, thereby obtaining a third product;

[0175] (4) Using a sprayer B-290 containing a nozzle head and a material conduit, the third product is sprayed into the circulating nitrogen at 100°C in the sprayer tower. The temperature of the third product in the material conduit is 15°C, and the temperature in the nozzle head is 120°C, to obtain a catalyst spherical carrier Z3.

[0176] According to tests, the average particle diameter (D50) of the catalyst spherical carrier Z3 is 5 microns, and the particle size distribution ((D90-D10) / D50) is 0.8.

[0177] Observation shows that the particles of the catalyst spherical carrier Z3 are relatively regular in shape, smooth in surface, and are basically spherical. The particle size distribution is relatively concentrated, and there are basically no irregular particles.

[0178] During the preparation of the catalyst spherical carrier Z3, no clogging occurred at the nozzle head of the sprayer, and a total of 12.0 g of the catalyst spherical carrier Z3 was obtained.

[0179] The catalyst polymerization was the same as in Example 2-1, except that Z3 replaced Z2.

[0180] The polypropylene powder is observed to have a good spherical shape under an electron microscope, and there is basically no irregular shape.

[0181] Example 3-2

[0182] This example uses the method provided in Example 3-1 to prepare polypropylene, except that the volume of hydrogen used is different, and all other aspects are the same.

[0183] Specifically: 1.5 L (standard volume) of hydrogen is replaced with 6.5 L (standard volume) of hydrogen to obtain polypropylene powder.

[0184] The polypropylene powder is observed to have a good spherical shape under an electron microscope, and there is basically no irregular shape.

[0185] Example 4

[0186] This example uses the method provided in Example 1-1 to prepare polypropylene, except that in addition to adding 0.25 mmol of triethylaluminum, 0.01 mmol of cyclohexylmethyldimethoxysilane is also added. Other steps are the same as in Example 1-1 to obtain polypropylene powder.

[0187] The polypropylene powder showed a good spherical shape when viewed under an electron microscope, and there was basically no irregular shape.

[0188] (1) In a 0.6 L reactor, 0.08 mol of magnesium chloride and 1.7 mol of ethanol were added, and the temperature was raised to 90°C under stirring. After the reaction was kept at this temperature for 1 hour, 0.48 mol of epichlorohydrin was added and the reaction was continued at 90°C for 30 minutes to obtain the first product;

[0189] (2) After filtering the first product, 2.5 mol of ethanol was added and stirred until a fluid mixture was formed;

[0190] (3) Using a sprayer containing a nozzle head and a material conduit, the fluidized mixture is sprayed into circulating nitrogen at 100° C., and the temperature of the third product in the material conduit is 15° C. and the temperature in the nozzle head is 120° C., to obtain a catalyst support DZ3 for olefin polymerization.

[0191] The average particle diameter (D50) of the olefin polymerization catalyst carrier DZ3 is 3 μm, and the particle size distribution ((D90-D10) / D50) is 0.8.

[0192] Comparative Example 1

[0193] Polypropylene was prepared in a manner similar to Example 1-1, except that diisobutyl phthalate was used instead of 2-isopropyl-2-isopentyl-1,3-dimethoxypropane in the preparation of the catalyst for olefin polymerization, and the rest was the same.

[0194] Comparative Example 2

[0195] Polypropylene was prepared in a manner similar to that of Comparative Example 1, except that the volume of hydrogen used in the preparation of polypropylene copolymer microspheres was different, namely 6.5 NL. The rest was the same as that of Comparative Example 1.

[0196] Comparative Example 3

[0197] Polypropylene was prepared in a manner similar to Example 1-1, except that DZ3 was used instead of Z1, and all other aspects were the same.

[0198] Comparative Example 4

[0199] Polypropylene was prepared in a manner similar to Example 1-1, except that no ethylene was added during polymerization.

[0200] Comparative Example 5

[0201] (1) The magnesium halide adduct MgXY·mR1OH was prepared according to the method disclosed in Example 1 of CN1718595, as follows:

[0202] In a 150-liter stirred reactor, 10 kg of anhydrous magnesium chloride and 12.6 kg of ethanol were added to 60 L of white oil with a viscosity of 30 centipoise (20°C) and reacted at 125°C for 2 hours. The resulting mixture of the molten adduct and white oil was then transferred to 120 L of methyl silicone oil preheated to 125°C (with a viscosity of 300 centipoise (20°C)). The mixture was stirred at 200 rpm for 10-30 minutes to obtain a mixture. The mixture was then introduced into a high-gravity rotating bed for dispersion. The dispersed mixture was then introduced into 1200 L of hexane precooled to -35°C under stirring. The magnesium chloride / alcohol adduct melt, dispersed into small droplets, cooled and solidified to form spherical solid particles. Solid particles were filtered out from the suspension obtained after rapid cooling, and washed with hexane at room temperature. The amount of hexane used was 100 L / time, and the washing was performed 5 times in total. The solid was then vacuumed at 60°C to obtain a solid.

[0203] The average particle diameter (D50) of the magnesium halide adduct was 52 μm, and the particle size distribution ((D90-D10) / D50) was 1.1. Electron microscopic observation of the particle morphology revealed that the magnesium halide adduct had a relatively regular particle morphology, a relatively smooth surface, and a relatively concentrated particle size distribution.

[0204] The structural formula of the magnesium halide adduct D5 was determined to be MgCl2·2.5C2H5OH by GC-MS, NMR and elemental analysis.

[0205] Except that Z1 is replaced by D5, the rest is the same as in Example 1-1.

[0206] Comparative Example 6

[0207] The volume of hydrogen used in the preparation of polypropylene copolymer microspheres was different, namely 6.5 NL, and the rest was the same as in Comparative Example 5.

[0208] Comparative Example 7

[0209] Random copolymer polypropylene pellets prepared using commercial DDC401 catalyst were pulverized after deep cooling with liquid nitrogen.

[0210] Table 1

[0211]

[0212]

[0213] *Cannot flow; **Cannot fall by gravity

[0214] Table 2

[0215] Half-peak width (°C) Molecular weight distribution Aspect ratio Example 1-17.27.01 Example 1-27.06.91 Example 2-17.26.81 Example 2-27.06.81 Example 3-17.26.61 Example 3-27.06.51 Example 48.05.81 Comparative Example 1 16.1--Comparative Example 2 15.6--Comparative Example 3-5.81 Comparative Example 4-5.51 Comparative Example 5 16.35.61.06 Comparative Example 6 16.05.41.07 Comparative Example 7 16.2-1.8

[0216] As shown in Table 2, the polypropylene microspheres of the present invention have a wider molecular weight distribution and a narrower half-value width. The resulting polypropylene microspheres have a relatively uniform crystalline sequence distribution. When used in 3D printing, the particles melt evenly, resulting in excellent product performance. Furthermore, the wider molecular weight distribution also imparts a better balance of rigidity and toughness to the product.

[0217] Test Example 1: Laser Sintering 3D Printing

[0218] 5 mg of antioxidant 1010 was dissolved in 100 ml of hexane and a certain amount of polypropylene powder described in the above examples or comparative examples was added. The mixture was evenly mixed and then dried. A certain amount of the above polypropylene powder was added to the selective laser sintering printer. The parameters were adjusted as follows: operating temperature 130-132°C, laser power 40W, scanning speed 1500 mm·s -1 , the scanning interval is 0.1mm, the spline is printed, and then the mechanical properties of the spline are tested. The specific results are shown in Table 3.

[0219] Table 3

[0220] Polymer shape Tensile strength / MPa Surface smoothness Example 1-1 Spherical 33.9 Good Example 1-2 Spherical 29.3 Good Example 2-1 Spherical 31.0 Good Example 2-2 Spherical 27.3 Good Example 3-1 Spherical 28.7 Good Example 3-2 Spherical 25.2 Good Example 4 Spherical 30.1 Good Comparative Example 1 Spherical shape cannot be printed - Comparative Example 2 Spherical shape cannot be printed - Comparative Example 3 Spherical shape 16.8 Poor Comparative Example 4 Spherical shape cannot be printed - Comparative Example 5 Spherical shape cannot be printed - Comparative Example 6 Spherical shape cannot be printed - Comparative Example 7 Irregular particle shape cannot be printed -

[0221] In summary, the copolymerized polypropylene powder prepared by the catalyst provided by the present invention presents a good spherical morphology, good fluidity, a small angle of repose, good tensile properties of 3D printed parts, and good smoothness of the objects. Due to the smaller angle of repose, the powder spreading effect is good, which is conducive to reducing spatial defects in the printing process. It also has a large specific surface area and a good fusion effect with antioxidants, which greatly reduces the local degradation of polypropylene during the laser sintering process. The ethylene-propylene copolymer product of the present invention has a narrower DSC measurement half-peak width and a more uniform copolymer crystal composition, which improves the uniformity of polymer particle melting and fusion, and improves the structural strength and surface properties of the sintered sample.

[0222] Test Example 2: Kettle Pressed Foam Beads

[0223] 1. The compressive strength of the foamed body is measured according to the method of Determination of Compression Properties of Rigid Foam Plastics GB / T8813-2008, and the flexural strength of the foamed body is measured according to the method of Determination of Flexural Properties of Rigid Foam Plastics GB / T8812-2007;

[0224] 2. Expansion Ratio Test Method for Expanded Beads: The density of the polypropylene composition expanded beads was determined using the displacement method using the YDK01 density accessory of a German Satorius CPA225D balance. Measurements were made according to the national standards GB / T1033.1-2008 and ISO1183-1:2012. The expansion ratio of the resulting polypropylene composition foam was calculated using the formula: b = ρ1 / ρ2, where b is the expansion ratio, ρ1 is the density of the binary random copolymer polypropylene base resin, and ρ2 is the apparent density of the foam.

[0225] 200g of copolymerized polypropylene microspheres were placed in an autoclave, and 0.2g of antioxidant 1010, 1000g of dispersion medium (deionized water), 1g of surfactant (sodium dodecylbenzene sulfonate), 1g of dispersant (kaolin) and 0.02g of dispersion enhancer (aluminum sulfate) were added and mixed; low-pressure carbon dioxide was then injected to completely replace the air in the autoclave, and high-pressure carbon dioxide was then injected again. The autoclave temperature was raised to 138°C, the pressure was controlled to 6MPa, and the swelling and penetration were allowed to proceed for 30 minutes. The pressure was then quickly released to 0 gauge pressure, the pressure release rate was controlled to 10MPa / s, and the contents of the autoclave were placed in 5°C cold water and dried. The different foam beads obtained by the foaming process described above were compression molded using a molding machine under a certain steam pressure for a certain time, and the resulting molded body was then aged for 24 hours at a temperature of 100°C and a pressure of standard atmospheric pressure to obtain a foamed bead molded body.

[0226] The expansion ratio of the foamed beads, the steam pressure during molding, and the molding time are shown in Table 4.

[0227] Table 4

[0228]

[0229]

[0230] As can be seen from the data in Table 4, the polymer copolymer microspheres of the present invention not only achieve a higher expansion ratio when used for foaming, but also require lower steam pressure and shorter molding time. Lower steam pressure not only helps save energy and reduce costs, but also helps reduce process risks. Shorter molding time means higher production efficiency, which is very meaningful for increasing profits and revenue.

[0231] It should be noted that the endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0232] The embodiments described above are intended only to illustrate the present invention and do not constitute any limitation thereto. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory rather than restrictive. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the invention described therein relates to specific methods, materials and embodiments, it does not mean that the invention is limited to the specific examples disclosed therein. On the contrary, the invention may be extended to all other methods and applications having the same function.

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