Industrial production method of tiger-texture-resistant polypropylene resin

Abstract

The invention relates to the technical field of high-molecular compounds, and particularly discloses an industrial production method of tiger-texture-resistant polypropylene resin. The Ziegler-Natta and metallocene composite catalyst is used, the advantages of different catalysts in different reactors are exerted, and the melt index of the formed regular homopolymer can be regulated and controlled by adjusting the dosage of an external electron donor; the metallocene catalyst can play a role in the gas-phase reactor, and the content, size and distribution of the rubber phase are controlled by adjusting the gas proportion of the gas-phase reactor and regulating and controlling the formation of the ethylene-propylene copolymer. The polypropylene resin which is high in melt index, wide in molecular weight distribution, uniform in rubber phase distribution and slow in plastic crystallization is prepared through an industrial device, the polypropylene resin has an excellent tiger skin texture resisting effect, and the defects that in the prior art, cost is high, the technological process is complex, and product selectivity is limited are overcome.

Description

Technical Field

[0001] The invention relates to the technical field of polymer compounds, and specifically discloses an industrial production method for anti-tiger-skin-grain polypropylene resin. Background Art

[0002] Polypropylene is a crystalline polymer with a regular structure. It has the advantages of light weight, easy processing and good flexibility. After being strengthened or toughened, it can be widely used in large injection molded parts, such as bumpers, side skirts, door inner panels, instrument panel frames and other automotive plastic parts and construction plastic parts. Such parts also have very high requirements for appearance, but during injection molding, it is easy to form wavy defects similar to tiger skin, which are called "tiger skin patterns". Tiger skin pattern defects not only affect the appearance of the product, but also the performance difference between the light and dark patterns, and even affect the performance of the product.

[0003] Tiger skin defects are mainly related to factors such as the melt index, molecular weight distribution, viscosity, and crystallization rate of the material. Materials with high melt index, wide molecular weight distribution, uniform rubber phase dispersion, and slow crystallization rate have better anti-tiger skin effect. In order to reduce the tiger skin defects produced by the material during injection molding. CN108219266B uses polypropylene with a high melt index (30-120g / 10min) and polypropylene with a low melt index (0.1-29g / 10min) to compound to improve the molecular weight distribution of the material, and blend with toughening agents, inorganic fillers, additives, etc., and eliminate tiger skin by adjusting the screw combination design and extrusion process parameters. CN111534008A mixes two different polypropylenes, two different toughening agents, talcum powder, wollastonite, nucleating agent, and lubricant, and prepares an anti-tiger skin polypropylene resin composition by extrusion granulation. CN114106470A uses tiger-skin-improving masterbatch and polypropylene with high and medium melt index, toughening agent, inorganic filler, etc. to prepare a polypropylene composition without tiger-skin-skin defects. CN114907642A uses low-isotactic polypropylene with high melt index (500-1500g / 10min) and slow crystallization rate as tiger-skin-skin modifier to prepare a polypropylene composite material that eliminates tiger-skin-skin-skin-skin-defects in bumpers. Similarly, CN114044977A and CN112708207A use different types of tiger-skin-improving agents to prepare anti-tiger-skin-skin-skin-modified materials by blending with materials such as polypropylene.

[0004] In the existing technical solutions, the tiger stripes are mainly eliminated by modification methods, which require the selection of different raw materials, the addition of functional additives, and the optimization of processing conditions. This has the disadvantages of high cost, complex process, and limited product selectivity, which is not conducive to large-scale production.

[0005] Therefore, it is urgent to develop a method for industrially producing anti-tiger-skin-grain polypropylene resin raw materials on a large-scale device. Summary of the invention

[0006] The technical problem to be solved by the present invention is to prepare an anti-tiger-skin-grain polypropylene resin capable of eliminating tiger-skin-grain defects in an industrial device by comprehensively regulating the melt index, molecular weight distribution, rubber phase distribution and crystallization rate of polypropylene.

[0007] The technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides an industrial production method of an anti-tiger-skin-grain polypropylene resin, using equipment including two serially connected loop reactors and a gas-phase fluidized bed reactor, and the preparation method comprises the following steps:

[0009] S1. Propylene is prepolymerized in a prepolymerization reactor under the combined action of a main catalyst, a co-catalyst, a dormant agent and an external electron donor to obtain a prepolymer;

[0010] The main catalyst is a Ziegler-Natta and metallocene composite catalyst, and the dosage of the main catalyst is 0.5-15 kg / h;

[0011] The co-catalyst is selected from one or more of trialkylaluminum and halogenated alkylaluminum compounds, and the amount of the co-catalyst is 0.5-10kg / h;

[0012] The dormant agent is selected from one or more of alkylethylene and phenylethylene compounds, and the amount of the dormant agent is 0.05-5% of the mass of the olefin monomer;

[0013] The external electron donor is selected from one or more of esters, carboxylic acids, organophosphorus compounds, and organosilicon compounds, and the dosage of the external electron donor is 0.5-10 kg / h;

[0014] In the main catalyst, the mass ratio of the metallocene composite catalyst to the Ziegler-Natta catalytic component is 5:1 to 1:2;

[0015] S2. The prepolymer obtained in step S1 is introduced into first and second loop reactors for liquid phase bulk polymerization with propylene and hydrogen, the amount of hydrogen added to the two loop reactors is controlled, the temperature, pressure and slurry density of the two loop reactors are continuously adjusted, and the two loop reactors are circulated in series to obtain homopolymerized polypropylene powder;

[0016] The hydrogen addition method in the first and second loop reactors is asymmetric hydrogenation, the hydrogen addition amount is 4000ppm-6000ppm; the propylene addition amount is 10000kg / h-30000kg / h;

[0017] The slurry density of the first and second loop reactors is 460-500 kg / m 3 , the reaction temperature is 65-75°C, and the reaction pressure is 3.5-4.5Mpa;

[0018] S3. The homopolymerized polypropylene powder obtained in step S2 is flashed to remove liquid propylene and then enters a gas phase reactor for gas phase copolymerization, ethylene is introduced as both an activator and a polymerization monomer, and the ethylene content, ethylene / (ethylene+propylene) and hydrogen / ethylene are controlled and adjusted to obtain a copolymerized polypropylene powder;

[0019] The gas phase reactor has an ethylene volume content of 10-20% of the total gas, an ethylene / (ethylene+propylene) volume ratio of 0.15-0.35, and a hydrogen / ethylene volume ratio of 0.015-0.040;

[0020] S4. Add compounding additives, including antioxidants, acid absorbers, lubricants and nucleating agents, to the obtained copolymer polypropylene powder, mix them evenly, and produce anti-tiger grain polypropylene material by extrusion granulation.

[0021] Preferably, the preparation method of the main catalyst is as follows:

[0022] The spherical alcohol MgCl2 carrier is added with the component TiCl4 at a temperature not higher than -10°C according to 15-30 mL TiCl4 per gram of carrier for full reaction; the temperature is raised to 50-70°C, and the carrier and the internal electron donor dibutyl adipate of 1-10% by mass of TiCl4 are added; the temperature is then raised to 110-130°C, stirred for reaction and filtered; then 20-40 ml TiCl4 is added per gram of carrier, stirred for reaction at 110-130°C and filtered;

[0023] The metallocene catalyst containing 0.1 mol of siloxane and 0.5 to 10 g of Zr element per 1 g of carrier is mixed at 30 to 50° C. after being fully stirred and mixed with the spherical Ziegler-Natta catalytic component prepared above. The mixing temperature is 30 to 50° C. After the reaction, it is filtered, washed, and dried to obtain a Ziegler-Natta and metallocene composite catalyst.

[0024] Furthermore, the molar ratio of alcohol to MgCl2 in the spherical alcohol-combined MgCl2 carrier is 2:1.

[0025] Furthermore, the alcohol is ethanol.

[0026] Preferably, the co-catalyst is triethylaluminum.

[0027] Preferably, the dormant agent is biphenylethylene.

[0028] Preferably, the external electron donor is tetraethoxysilane.

[0029] Preferably, in step S4, the nucleating agent is selected from one or more of carboxylic acid metal salts, phosphate metal salts and sorbitol benzyl derivatives.

[0030] Furthermore, the nucleating agent is a phosphate metal salt with a dosage of 0.08%-0.2%.

[0031] In a second aspect, the present invention provides an anti-tiger-skin-grain polypropylene resin prepared by the method described in the first aspect.

[0032] Beneficial effects achieved by the present invention:

[0033] The invention prepares a polypropylene resin with high melt index, wide molecular weight distribution, uniform rubber phase distribution and slow crystallization plasticity through an industrial device, has excellent anti-tiger stripe effect, and solves the shortcomings of the prior art such as high cost, complex process and limited product selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the morphology of the samples for tiger stripe status evaluation prepared in the examples and comparative examples of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the following examples. It should be noted that the present invention is not limited to the following examples.

[0036] Example 1

[0037] The main catalyst is a Ziegler-Natta and metallocene composite catalyst, and the preparation method is as follows:

[0038] Put the spherical alcohol-complexed MgCl2 carrier with a molar ratio of ethanol to MgCl2 of 2:1 into a preparation bottle, add 20mL TiCl4 per 1g of carrier at -10℃, and react for 1h. Stir and gradually increase the temperature. When it reaches 60℃, add 2% internal electron donor dibutyl adipate; then continue to heat to 120℃, stir and react for 2h, filter; then add 30ml TiCl4 per 1g of carrier, stir and react at 120℃ for 2h, and filter.

[0039] For every 1g of carrier, 0.1mol of siloxane and 2g of C2H4(lnd)2ZrCl2 were prepared and mixed at 40°C and then mixed with the spherical Ziegler-Natta catalytic component prepared above. The mixing temperature was 40°C and the reaction was stirred for 2h. Then it was filtered, washed with octane, and dried to obtain a Ziegler-Natta and metallocene composite catalyst.

[0040] Ziegler-Natta and metallocene composite catalyst, triethylaluminum, biphenylethylene and tetraethoxysilane were pre-contacted at 10°C for 15 minutes and then continuously added to the prepolymerization reactor for prepolymerization. The amount of Ziegler-Natta and metallocene composite catalyst was 5kg / h, the amount of triethylaluminum was 5kg / h, the amount of biphenylethylene was 0.1kg / h, and the amount of tetraethoxysilane was 10kg / h. The prepolymerization was carried out in a reactor filled with supercooled liquid propylene, the reaction temperature was 20°C, and the residence time was 15 minutes.

[0041] The prepolymer, fresh propylene and hydrogen are continuously fed into the first and second loop reactors. The propylene feed rates of the first and second loop reactors are 10,000 kg / h and 30,000 kg / h, respectively. The first and second loop reactors adopt asymmetric hydrogenation. The hydrogen feed rates are 5,500 ppm and 4,000 ppm, respectively. The temperature, pressure and slurry density of the reactors are 69° C., 3.7 MPa and 480 kg / m 3 , through two loop reactors connected in series and circulating, homopolymerized polypropylene powder is obtained.

[0042] The homopolymerized polypropylene powder is flashed to remove liquid propylene and then enters a gas phase reactor, where ethylene is introduced as both an activator and a polymerization monomer. The ethylene content is adjusted to 10%, ethylene / (ethylene+propylene) to 0.15, and hydrogen / ethylene to 0.035 to obtain a copolymerized polypropylene powder.

[0043] 0.1% of the main antioxidant 1010, 0.2% of the auxiliary antioxidant 168, 0.2% of the halogen absorber calcium stearate and 0.08% of the nucleating agent HPN-505 compounding auxiliary agent were added to the obtained copolymer polypropylene powder, mixed evenly, and then extruded and granulated to produce the anti-tiger grain polypropylene material.

[0044] Example 2

[0045] The same as Example 1, except that the amounts of Ziegler-Natta and metallocene composite catalysts, triethylaluminum, biphenylethylene and tetraethoxysilane used were 10 kg / h, 10 kg / h, 0.5 kg / h and 5 kg / h, respectively; the amounts of propylene added to the first and second loop reactors were 10000 kg / h and 30000 kg / h, respectively; the amounts of hydrogen added to the first and second loop reactors were 6000 ppm and 4000 ppm, respectively; the temperature, pressure and slurry density of the reactors were 70° C., 4.2 MPa and 500 kg / m 3 ; The ethylene content in the gas phase reactor was 15%, ethylene / (ethylene+propylene) was 0.20, and hydrogen / ethylene was 0.030; the addition amount of nucleating agent HPN-505 was 0.1%.

[0046] Example 3

[0047] Same as Example 1, except that: the amounts of Ziegler-Natta and metallocene composite catalysts, triethylaluminum, biphenylethylene and tetraethoxysilane used were 5kg / h, 10kg / h, 1kg / h and 8kg / h, respectively; the amounts of propylene added to the first and second loop reactors were 10000kg / h and 30000kg / h, respectively; the amounts of hydrogen added to the first and second loop reactors were 5500ppm and 4500ppm, respectively; the temperature, pressure and slurry density of the reactors were 72°C, 4.4MPa and 470kg / m 3 ; The ethylene content in the gas phase reactor was 17%, ethylene / (ethylene+propylene) was 0.25, and hydrogen / ethylene was 0.025; the addition amount of nucleating agent HPN-505 was 0.15%.

[0048] Example 4

[0049] Same as Example 1, except that: the amounts of Ziegler-Natta and metallocene composite catalysts, triethylaluminum, biphenylethylene and tetraethoxysilane used were 5kg / h, 8kg / h, 0.5kg / h and 15kg / h, respectively; the amounts of propylene added to the first and second loop reactors were 10000kg / h and 30000kg / h, respectively; the amounts of hydrogen added to the first and second loop reactors were 5000ppm and 4500ppm, respectively; the temperature, pressure and slurry density of the reactors were 70°C, 3.8MPa and 480kg / m 3 ; The ethylene content in the gas phase reactor was 20%, ethylene / (ethylene+propylene) was 0.30, and hydrogen / ethylene was 0.015; the addition amount of nucleating agent HPN-505 was 0.15%.

[0050] Example 5

[0051] Same as Example 1, except that: the amounts of Ziegler-Natta and metallocene composite catalysts, triethylaluminum, biphenylethylene and tetraethoxysilane used were 10 kg / h, 6 kg / h, 1.5 kg / h and 10 kg / h, respectively; the amounts of propylene added to the first and second loop reactors were 10000 kg / h and 30000 kg / h, respectively; the amounts of hydrogen added to the first and second loop reactors were 4500 ppm and 4000 ppm, respectively; the temperature, pressure and slurry density of the reactors were 66° C., 3.6 MPa and 470 kg / m 3 ; The ethylene content in the gas phase reactor was 14%, ethylene / (ethylene+propylene) was 0.20, and hydrogen / ethylene was 0.020; the addition amount of nucleating agent HPN-505 was 0.13%.

[0052] Example 6

[0053] Same as Example 1, except that: the amounts of Ziegler-Natta and metallocene composite catalysts, triethylaluminum, biphenylethylene and tetraethoxysilane used were 5kg / h, 10kg / h, 0.5kg / h and 15kg / h, respectively; the amounts of propylene added to the first and second loop reactors were 10000kg / h and 30000kg / h, respectively; the amounts of hydrogen added to the first and second loop reactors were 4500ppm and 4200ppm, respectively; the temperature, pressure and slurry density of the reactors were 67°C, 3.7MPa and 490kg / m 3 ; The ethylene content in the gas phase reactor was 18%, ethylene / (ethylene+propylene) was 0.25, and hydrogen / ethylene was 0.020; the addition amount of nucleating agent HPN-505 was 0.17%.

[0054] Comparative Example 1

[0055] The same as Example 1, except that the catalyst used is a Ziegler-Natta catalyst, and the amounts of the Ziegler-Natta catalyst, triethylaluminum and tetraethoxysilane used are 5 kg / h, 6 kg / h and 8 kg / h, respectively; the amounts of propylene added to the first and second loop reactors are 10000 kg / h and 30000 kg / h, respectively; the amounts of hydrogen added to the first and second loop reactors are 5000 ppm and 4000 ppm, respectively; the temperature, pressure and slurry density of the reactors are 70°C, 3.8 MPa and 470 kg / m 3 ; The ethylene content in the gas phase reactor was 15%, ethylene / (ethylene+propylene) was 0.25, and hydrogen / ethylene was 0.028; the addition amount of nucleating agent HPN-505 was 0.10%.

[0056] The test results are as follows:

[0057] Table 1 Test results of examples and comparative examples

[0058]

[0059] Test standard:

[0060] (1) Melt index: measured according to GB / T 3682.1-2018;

[0061] (2) Tensile strength: measured according to GB / T 1040.2-2006;

[0062] (3) Flexural modulus: measured according to GB / T 9341-2008;

[0063] (4) Impact strength: measured according to GB / T 1843-2008;

[0064] (5) Molecular weight distribution width: measured according to GB / T 21863-2008;

[0065] (6) Xylene soluble matter content: measured according to GB / T 24282-2009;

[0066] (7) Product appearance: see Figure 1 , a sample of 800mm×50mm×2.0mm was made by injection molding, and the tiger skin pattern on its surface was visually observed.

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An industrial production method of anti-tiger-skin-grain polypropylene resin, characterized in that: The preparation method comprises the following steps: S1. Propylene is prepolymerized in a prepolymerization reactor under the combined action of a main catalyst, a co-catalyst, a dormant agent and an external electron donor to obtain a prepolymer; The main catalyst is a Ziegler-Natta and metallocene composite catalyst, and the dosage of the main catalyst is 0.5-15 kg / h; The co-catalyst is selected from one or more of trialkylaluminum and halogenated alkylaluminum compounds, and the amount of the co-catalyst is 0.5-10kg / h; The dormant agent is selected from one or more of alkylethylene and phenylethylene compounds, and the amount of the dormant agent is 0.05-5% of the mass of the olefin monomer; The external electron donor is selected from one or more of esters, carboxylic acids, organophosphorus compounds, and organosilicon compounds, and the dosage of the external electron donor is 0.5-10 kg / h; In the main catalyst, the mass ratio of the metallocene composite catalyst to the Ziegler-Natta catalytic component is 5:1 to 1:2; S2. The prepolymer obtained in step S1 is introduced into the first and second loop reactors for liquid phase bulk polymerization with propylene and hydrogen, and the amount of hydrogen added to the two loop reactors, the temperature, pressure and slurry density of the two loop reactors are controlled, and the two loop reactors are circulated in series to obtain a homopolymerized polypropylene powder; The hydrogen addition method in the first and second loop reactors is asymmetric hydrogenation, the hydrogen addition amount is 4000ppm-6000ppm; the propylene addition amount is 10000kg / h-30000kg / h; The slurry density of the first and second loop reactors is 460-500 kg / m 3 , the reaction temperature is 65-75°C, and the reaction pressure is 3.5-4.5Mpa; S3. The homopolymerized polypropylene powder obtained in step S2 is flashed to remove liquid propylene and then enters a gas phase reactor for gas phase copolymerization to control and adjust the ethylene content, ethylene / (ethylene + propylene) and hydrogen / ethylene to obtain a copolymerized polypropylene powder; The gas phase reactor has an ethylene volume content of 10-20% of the total gas, an ethylene / (ethylene+propylene) volume ratio of 0.15-0.35, and a hydrogen / ethylene volume ratio of 0.015-0.040; S4. Add compounding additives, including antioxidants, acid absorbers, lubricants and nucleating agents, to the obtained copolymer polypropylene powder, mix them evenly, and produce anti-tiger grain polypropylene material by extrusion granulation.

2. The industrial production method of anti-tiger pattern polypropylene resin according to claim 1, characterized in that, The preparation method of the main catalyst is as follows: The spherical alcohol MgCl2 carrier is added with the component TiCl4 at a temperature not higher than -10°C according to 15-30 mL TiCl4 per gram of carrier for full reaction; the temperature is raised to 50-70°C, and the carrier and the internal electron donor dibutyl adipate of 1-10% by mass of TiCl4 are added; the temperature is then raised to 110-130°C, stirred for reaction and filtered; then 20-40 ml TiCl4 is added per gram of carrier, stirred for reaction at 110-130°C and filtered; The metallocene catalyst containing 0.1 mol of siloxane and 0.5 to 10 g of Zr element per 1 g of carrier is mixed at 30 to 50° C. after being fully stirred and mixed with the spherical Ziegler-Natta catalytic component prepared above. The mixing temperature is 30 to 50° C. After the reaction, it is filtered, washed, and dried to obtain a Ziegler-Natta and metallocene composite catalyst.

3. The industrial production method of anti-tiger pattern polypropylene resin according to claim 2, characterized in that, The molar ratio of alcohol to MgCl2 in the spherical alcohol-combined MgCl2 carrier is 2:

1.

4. The industrial production method of anti-tiger pattern polypropylene resin according to claim 3, characterized in that, The alcohol is ethanol.

5. The industrial production method of anti-tiger pattern polypropylene resin according to claim 1, characterized in that: The co-catalyst is triethylaluminum.

6. The industrial production method of anti-tiger pattern polypropylene resin according to claim 1, characterized in that: The dormant agent is biphenylethylene.

7. The industrial production method of anti-tiger pattern polypropylene resin according to claim 1, characterized in that: The external electron donor is tetraethoxysilane.

8. The industrial production method of anti-tiger grain polypropylene resin according to claim 1, characterized in that: In the step S4, the nucleating agent is selected from one or more of carboxylic acid metal salts, phosphate metal salts and sorbitol benzyl derivatives.

9. The industrial production method of anti-tiger pattern polypropylene resin according to claim 8, characterized in that: The nucleating agent is a phosphate metal salt, and the dosage is 0.08%-0.2%.

10. An anti-tiger-skin-grain polypropylene resin prepared by the method according to any one of claims 1 to 9.

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