Preparation method of tiger-texture-resistant and stress-cracking-resistant polypropylene material

Abstract

The invention relates to the technical field of high-molecular compounds, and particularly discloses a preparation method of a tiger-texture-resistant stress-cracking-resistant polypropylene material. The method specifically comprises the following steps: S1, respectively feeding a main catalyst, TEAL and an electron donor which are metered into a catalyst pre-contact tank, and enabling materials in the tank to be in pre-contact at a constant temperature of 10-15 DEG C; s2, propylene and hydrogen are used as raw materials and added into the loop reactor, and homo-polypropylene powder is obtained. S3, conveying the homo-polypropylene powder into a gas phase reactor, introducing ethylene, and controlling and adjusting hydrogen / ethylene to obtain anti-tiger skin and stress cracking resistant co-polypropylene powder; and S4, adding a compound auxiliary agent into the obtained polypropylene powder, uniformly mixing, and granulating and extruding to produce the tiger-skin-texture-resistant stress-cracking-resistant polypropylene material. Tests show that the obtained polypropylene material has good tiger wrinkle resistance and stress cracking resistance.

Description

Technical Field

[0001] The invention relates to the technical field of polymer compounds, and specifically discloses a method for preparing a tiger-skin-resistant and stress-cracking resistant polypropylene material. Background Art

[0002] High impact and high melt index polypropylene special materials are mainly used in the fields of automobiles, modification, home appliances, etc. With the emergence of the national mandatory standards for vehicle hazard resistance, the requirements for stress cracking resistance of automotive materials have become very strict. Accordingly, under the premise of similar basic physical properties, polypropylene products with stress cracking resistance and tiger skin grain resistance are more favored by the high-end polypropylene market.

[0003] The tiger stripe problem is essentially caused by the rubber phase in the formula system forming different phase forms during the filling process. Usually, the dispersed rubber phase presents a nearly spherical shape, but when the melt flows in the mold like a fountain, some rubber particles are stretched and oriented. In the subsequent cooling process, the oriented structure of the rubber phase does not recover in time, resulting in the existence of oriented and unoriented rubber phase structures in the system, causing light and dark stripes on the surface of the entire component, that is, tiger stripes.

[0004] Modified polypropylene as a material for automobile door panels must have good rigidity and impact resistance, as well as certain weather resistance and resistance to thermal oxidation aging. It must also have processing characteristics such as resistance to stress cracking and dimensional stability.

[0005] CN 111286127 A discloses a polypropylene composite material without tiger stripes at high temperature and a patent for a preparation method. The patent can eliminate the tiger stripe phenomenon generated by the composite material during the injection molding process at room temperature by adding a high temperature resistant tiger stripe eliminating agent.

[0006] CN 101058655 B discloses a stress whitening and stress cracking resistant filled modified polypropylene and its preparation method and application patent. The invention adopts a method of processing and modifying with multiple auxiliary agents, and each performance index of the prepared polypropylene material reaches or exceeds the predetermined requirements.

[0007] The above two patents are both polypropylene composite materials prepared by a processing modification method, which requires a large amount of processing aids, has a complex processing process and is costly.

[0008] Therefore, in view of the above problems, a method is provided for preparing a tiger-skin pattern-resistant and stress-cracking-resistant polypropylene material by producing homopolymerized polypropylene powder through two loop tube reactors and adding a certain proportion of simple compounding additives to solve the above problems. Summary of the invention

[0009] The technical solution adopted by the present invention is as follows:

[0010] In a first aspect, the present invention provides a method for preparing a tiger-skin-resistant stress-cracking polypropylene material, the preparation method comprising the following steps:

[0011] S1. The Ziegler-Natta catalyst and the electron donor are respectively fed into a catalyst pre-contact tank, the feed amount of propylene raw material is 3.0-10.0 L / h of main catalyst, 4.0-8.0 kg / h of co-catalyst, and 1.0-2.0 kg / h of external electron donor; the materials in the tank are pre-contacted at a constant temperature of 10-15°C, and the reaction time is 10-20 min;

[0012] S2. Propylene and hydrogen are added to the loop reactor as raw materials, and the prepolymer obtained in step S1 is added to control the amount of hydrogen added to the two loop reactors to be 3000-5000ppm, and the slurry density is 450~500kg / m 3 , the temperature is 60-70℃, the pressure is 3.0~4.0MPa; the reaction time is 1.5~3h;; through two loop reactors in series circulation, homopolymerized polypropylene powder is obtained;

[0013] S3. The homopolymerized polypropylene powder obtained in step S2 is transported to a gas phase reactor R401 for gas phase copolymerization with ethylene and propylene; the temperature of the gas phase reactor R401 is controlled to be 75 to 80°C, the pressure is 1.30 to 1.50 MPa, and the ethylene content is 8.0 to 16.0%; the reaction time is 30 to 50 min; the homopolymerized polypropylene powder is sent to a gas phase reactor and ethylene is introduced. The molar ratio of hydrogen to ethylene is adjusted to 0.035 to 0.040 to obtain a tiger-skin-resistant stress cracking copolymerized polypropylene powder;

[0014] S4. Add compounding additives and nucleating agents to the obtained anti-tiger pattern stress cracking resistant polypropylene powder, mix well, and produce anti-tiger pattern stress cracking resistant polypropylene material by granulation and extrusion;

[0015] The compound auxiliary agent is one or a mixture of two or more of antioxidants 1010, 626, and 3114, and the addition amount is 2000-3000ppm;

[0016] The amount of the nucleating agent added is 500-1000 ppm.

[0017] Preferably, the internal electron donor of the Ziegler-Natta catalyst is an organic compound containing nitrogen, phosphorus and silicon or a 1,3-diether compound.

[0018] Furthermore, the internal electron donor is 2,2-diisobutyl-1,3-dimethoxypropane.

[0019] Preferably, the external electron donor of the Ziegler-Natta catalyst is an alkoxyalkane compound.

[0020] Furthermore, the external electron donor is a composite external electron donor of cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P).

[0021] Furthermore, the cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P) are mixed in a ratio of 2:1.

[0022] Preferably, the titanium content of the Ziegler-Natta catalyst is 1.8-4.0%, and the ester content is 8-15%. The polymerization activity is 5×10 4 -10 5 gPP / gCat.

[0023] Preferably, the nucleating agent is one or a mixture of M161 and RNHS-03.

[0024] Preferably, when the compound auxiliary agent contains two components, the mass ratio is 1:2 to 2:1; when it contains three components, the mass ratio is equal.

[0025] In a second aspect, the present invention provides a tiger-skin-resistant stress-cracking polypropylene material, which is prepared by the method described in the first aspect.

[0026] Beneficial effects achieved by the present invention:

[0027] The polypropylene material is first produced into homopolymerized polypropylene powder through two loop reactors. In the catalyst prepolymerization process, the active center of the catalyst is improved by selecting a high-activity catalyst; the slurry density and loop temperature in the loop reactor are adjusted during the polymerization process; the ratio of hydrogen / ethylene in the gas phase reactor is further adjusted to form polypropylene powder, and then a compounding auxiliary agent is added to prepare a polypropylene material that is resistant to tiger stripes and stress cracking. The melt index of the polypropylene material produced by this device in China is 30-50g / 10min, and the impact strength is ≥50kJ / m 2 In addition, the polypropylene material has passed the test and has good anti-tiger pattern effect and stress cracking resistance. The product performance indicators can also meet the following requirements:

[0028] (1) Melt flow rate (2.16Kg): 40.00±10g / 10min;

[0029] (2) Impact strength: ≥50KJ / m 2 ;

[0030] (3) Flexural modulus: ≥1000MPa;

[0031] (4) Tiger skin pattern level: ≥ level 2

[0032] (5) Stress cracking test: No cracking. DETAILED DESCRIPTION

[0033] 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.

[0034] Example 1

[0035] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0036] The selection activity was 8×10 4 gPP / gCat Ziegler Natta catalyst main catalyst, 2,2-diisobutyl-1,3-dimethoxypropane is selected as the internal electron donor, cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P) are mixed in a mass ratio of 2:1 to form a composite external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 7L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0037] Propylene and hydrogen are used as raw materials, added into the loop reactor, and circulated through two loop reactors in series. The amount of hydrogen added to the two loop reactors is controlled to be 4000 / 3500ppm, and the slurry density is 460 / 460kg / m 3 , the temperature is 65 / 65℃, the pressure is 3.8MPa, and the reaction time is 1.5h; a homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0038] The homopolymerized polypropylene powder is transported to the gas phase reactor R401 to undergo gas phase copolymerization with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the sphere of the homopolymer, and finally a mixture of the homopolymer and the binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 75° C., the pressure to be 1.30 MPa, the ethylene content to be 15.0%, the reaction time to be 40 min, and the hydrogen / ethylene molar ratio to be 0.038; and the anti-tiger-skin-grain and stress-cracking resistant copolymerized polypropylene powder is obtained;

[0039] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a ratio of 1:2, with a total addition amount of 2500ppm; the nucleating agents are selected from M161 and RNHS-03, which are evenly mixed in a ratio of 1:1, with a total addition amount of 600ppm, and the two are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0040] See the table below for performance.

[0041] Example 2

[0042] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0043] The activity was selected to be 5×10 4 gPP / gCat Ziegler Natta catalyst main catalyst, 2,2-diisobutyl-1,3-dimethoxypropane is selected as the internal electron donor, cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P) are mixed in a mass ratio of 2:1 to form a composite external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 8 / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0044] Propylene and hydrogen are used as raw materials and added into the loop reactor. The two loop reactors are circulated in series. The amount of hydrogen added to the two loop reactors is controlled to be 4000 / 3000ppm, and the slurry density is 465 / 465kg / m 3 , temperature is 65 / 65℃, pressure is 3.6MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0045] The homopolymerized polypropylene powder is transported to the gas phase reactor R401, and the temperature of the gas phase reactor R401 is controlled to be 75° C., the pressure is 1.30 MPa, the ethylene content is 14.0%, the reaction time is 40 min, and the molar ratio of hydrogen to ethylene is 0.035, to obtain the anti-tiger pattern stress cracking resistant copolymerized polypropylene powder;

[0046] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a ratio of 1:2, with a total addition amount of 2500ppm; the nucleating agents are selected from M161 and RNHS-03, which are evenly mixed in a ratio of 1:1, with a total addition amount of 600ppm, and the two are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0047] Example 3

[0048] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0049] The selection activity was 8×10 4 gPP / gCat Ziegler Natta catalyst main catalyst, 1,1-bis(methoxymethyl)cyclobutane is selected as the internal electron donor, cyclohexylmethyldimethoxysilane (Donor-C) is selected as the external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 7L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0050] Propylene and hydrogen are used as raw materials, added into the loop reactor, and circulated through two loop reactors in series. The amount of hydrogen added to the two loop reactors is controlled to be 4000 / 3500ppm, and the slurry density is 470 / 470kg / m 3 , temperature is 66 / 66℃, pressure is 3.8MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0051] The homopolymerized polypropylene powder is transported to the gas phase reactor R401, and the temperature of the gas phase reactor R401 is controlled to be 75° C., the pressure is 1.30 MPa, the ethylene content is 13.5%, the reaction time is 40 min, and the molar ratio of hydrogen to ethylene is 0.036, to obtain the anti-tiger pattern and stress cracking resistant copolymerized polypropylene powder;

[0052] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a ratio of 1:2, with a total addition amount of 2500ppm; the nucleating agents are selected from M161 and RNHS-03, which are evenly mixed in a ratio of 1:1, with a total addition amount of 600ppm, and the two are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0053] Performance is shown in the table below.

[0054] Example 4

[0055] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0056] The selection activity was 8×10 4gPP / gCat Ziegler Natta catalyst main catalyst, 1,1-bis(methoxymethyl)cyclobutane is selected as the internal electron donor, dicyclopentyldimethoxysilane (Donor-D) and diisopropyldimethoxysilane (Donor-P) are mixed in a mass ratio of 2:1 to form a composite external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 7L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0057] Propylene and hydrogen are used as raw materials, added into the loop reactor, and circulated through two loop reactors in series. The amount of hydrogen added to the two loop reactors is controlled to be 4000 / 3000ppm, and the slurry density is 460 / 460kg / m 3 , temperature is 65 / 65℃, pressure is 3.8MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0058] The homopolymerized polypropylene powder is transported to the gas phase reactor R401 to undergo gas phase copolymerization with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the sphere of the homopolymer, and finally a mixture of the homopolymer and the binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 75° C., the pressure to be 1.30 MPa, the ethylene content to be 15.0%, the reaction time to be 40 min, and the hydrogen / ethylene molar ratio to be 0.038; and the anti-tiger-skin-grain and stress-cracking resistant copolymerized polypropylene powder is obtained;

[0059] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a ratio of 1:2, with a total addition amount of 2500ppm; the nucleating agents are selected from M161 and RNHS-03, which are evenly mixed in a ratio of 1:1, with a total addition amount of 600ppm, and the two are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0060] See the table below for performance.

[0061] Example 5

[0062] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0063] The selection activity was 8×10 4gPP / gCat Ziegler Natta catalyst main catalyst, 2,2-diisobutyl-1,3-dimethoxypropane is selected as the internal electron donor, dicyclopentyl dimethoxysilane (Donor-D) and diisopropyl dimethoxysilane (Donor-P) are mixed in a mass ratio of 2:1 to form a composite external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 7L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0064] Propylene and hydrogen are used as raw materials, added into the loop reactor, and circulated through two loop reactors in series. The amount of hydrogen added to the two loop reactors is controlled to be 3500 / 3500ppm, and the slurry density is 460 / 460kg / m 3 , temperature is 65.5 / 65.5℃, pressure is 3.6MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0065] The homopolymerized polypropylene powder is transported to the gas phase reactor R401 to undergo gas phase copolymerization with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the sphere of the homopolymer, and finally a mixture of the homopolymer and the binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 75° C., the pressure to be 1.30 MPa, the ethylene content to be 15.0%, the reaction time to be 40 min, and the molar ratio of hydrogen / ethylene to be 0.035, to obtain a tiger-skin-resistant stress cracking resistant copolymerized polypropylene powder;

[0066] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a ratio of 1:2, with a total addition amount of 2500ppm; the nucleating agents are selected from M161 and RNHS-03, which are evenly mixed in a ratio of 1:1, with a total addition amount of 600ppm, and the two are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0067] See the table below for performance.

[0068] Example 6

[0069] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0070] The selection activity was 8×10 4gPP / gCat Ziegler Natta catalyst main catalyst, 2,2-diisobutyl-1,3-dimethoxypropane is selected as the internal electron donor, cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P) are mixed in a ratio of 2:1 to form a composite external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 7L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0071] Propylene and hydrogen are used as raw materials, added into the loop reactor, and circulated through two loop reactors in series. The amount of hydrogen added to the two loop reactors is controlled to be 4000 / 3500ppm, and the slurry density is 460 / 460kg / m 3 , temperature is 65 / 65℃, pressure is 3.8MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0072] The homopolymerized polypropylene powder is transported to the gas phase reactor R401 to undergo gas phase copolymerization with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the sphere of the homopolymer, and finally a mixture of the homopolymer and the binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 70° C., the pressure is 1.35 MPa, the ethylene content is 14.5%, the reaction time is 40 min, and the molar ratio of hydrogen / ethylene is 0.030, to obtain a tiger-skin-resistant stress cracking resistant copolymerized polypropylene powder;

[0073] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a ratio of 1:2, with a total addition amount of 2500ppm; the nucleating agents are selected from M161 and RNHS-03, which are evenly mixed in a ratio of 1:1, with a total addition amount of 600ppm, and the two are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0074] See the table below for performance.

[0075] Example 7

[0076] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0077] The selection activity was 8×10 4gPP / gCat Ziegler Natta catalyst main catalyst, 2,2-diisobutyl-1,3-dimethoxypropane is selected as the internal electron donor, cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P) are mixed in a ratio of 2:1 to form a composite external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 6.5L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0078] Propylene and hydrogen are used as raw materials, added into the loop reactor, and circulated through two loop reactors in series. The amount of hydrogen added to the two loop reactors is controlled to be 3800 / 3500ppm, and the slurry density is 460 / 460kg / m 3 , temperature is 65 / 65℃, pressure is 3.8MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0079] The homopolymerized polypropylene powder is transported to the gas phase reactor R401 to undergo gas phase copolymerization with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the sphere of the homopolymer, and finally a mixture of the homopolymer and the binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 70° C., the pressure is 1.30 MPa, the ethylene content is 13.0%, the reaction time is 40 min, and the molar ratio of hydrogen / ethylene is 0.035; and the anti-tiger-skin-grain and stress-cracking resistant copolymerized polypropylene powder is obtained;

[0080] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and its added components are 1010:3114:626 mixed in a 1:1:1 manner, with a total addition amount of 2500ppm; its added components are 1010: the nucleating agent is M161, and both are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0081] Performance is shown in the table below.

[0082] Comparative Example 1

[0083] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0084] The activity was selected to be 4 × 10 4gPP / gCat Ziegler Natta catalyst main catalyst, 1,1-bis(methoxymethyl)cyclobutane is selected as the internal electron donor, cyclohexylmethyldimethoxysilane (Donor-C) is selected as the external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 7L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0085] Propylene and hydrogen are used as raw materials and added into the loop reactor. The two loop reactors are circulated in series. The amount of hydrogen added to the two loop reactors is controlled to be 4000 / 3500ppm, and the slurry density is 460 / 460kg / m 3 , temperature is 65 / 65℃, pressure is 3.8MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0086] The homopolymerized polypropylene powder is transported to the gas phase reactor R401 to undergo gas phase copolymerization with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the sphere of the homopolymer, and finally a mixture of the homopolymer and the binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 75° C., the pressure is 1.30 MPa, the ethylene content is 13.0%, the reaction time is 40 min, and the molar ratio of hydrogen / ethylene is 0.035; and the anti-tiger-skin-grain and stress-cracking resistant copolymerized polypropylene powder is obtained;

[0087] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a 1:2 manner, with a total addition amount of 2000ppm; RNHS-03 is selected as the nucleating agent, and the addition amount is 700ppm. Both are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0088] Performance is shown in the table below.

[0089] Comparative Example 2

[0090] A method for preparing a tiger-skin-resistant stress-cracking polypropylene material, characterized in that the preparation method comprises the following steps:

[0091] The selection activity was 6×10 4gPP / gCat Ziegler Natta catalyst main catalyst, 2,2-diisobutyl-1,3-dimethoxypropane is selected as the internal electron donor, cyclohexylmethyldimethoxysilane (Donor-C) and dicyclopentyldimethoxysilane (Donor-D) are mixed in a ratio of 2:1 to form a composite external electron donor, and the metered main catalyst, TEAL and electron donor are respectively sent to the catalyst pre-contact tank, so that the materials in the tank are pre-contacted at a constant temperature of 10°C. The feed amount of propylene raw material is 7L / h for the main catalyst, 5.0kg / h for the co-catalyst, and 1.0kg / h for the external electron donor;

[0092] Propylene and hydrogen are used as raw materials and added into the loop reactor. The two loop reactors are circulated in series. The amount of hydrogen added to the two loop reactors is controlled to be 4000 / 3500ppm, and the slurry density is 460 / 460kg / m 3 , temperature is 65 / 65℃, pressure is 3.8MPa; reaction time is 1.5h; homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained;

[0093] The homopolymerized polypropylene powder is transported to the gas phase reactor R401 to undergo gas phase copolymerization with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the sphere of the homopolymer, and finally a mixture of the homopolymer and the binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 75° C., the pressure is 1.30 MPa, the ethylene content is 13.0%, the reaction time is 40 min, and the molar ratio of hydrogen / ethylene is 0.035; and the anti-tiger-skin-grain and stress-cracking resistant copolymerized polypropylene powder is obtained;

[0094] A compounding auxiliary agent is added to the obtained anti-tiger-skin-grain and stress-cracking resistant copolymer polypropylene powder, and the added components are mixed in a ratio of 3114:626 in a 1:2 manner, with a total addition amount of 2500ppm; the nucleating agent is M161, and the addition amount is 700ppm. Both are added at the same time, and the anti-tiger-skin-grain and stress-cracking resistant polypropylene material is produced through granulation and extrusion.

[0095] The performance is shown in Table 1 below.

[0096] Table 1 Test results of examples and comparative examples

[0097]

[0098]

[0099] Test standard:

[0100] (1) Melt flow rate: GB / T 3682.1-2018

[0101] (2) Flexural modulus: GB / T 9341-2008

[0102] (3) Simply supported beam impact strength: GB / T 1043.1-2008

[0103] (4) Tiger pattern resistance level (no exposure): Use a spiral pattern mold to evaluate and observe the location of tiger pattern. If tiger pattern appears above 620 mm, the level is 1; if tiger pattern appears between 580-620 mm, the level is 2; if tiger pattern appears between 0-580 mm, the level is 3. The higher the level, the more obvious the tiger pattern.

[0104] (5) Stress cracking test: A 10-20 mm × 5 mm screw was screwed into an injection-molded screw column with an inner diameter of 4 mm. No obvious cracking occurred.

[0105] 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. A method for preparing a tiger-skin-resistant stress cracking resistant polypropylene material, characterized in that: The preparation method comprises the following steps: S1. The Ziegler-Natta catalyst and the electron donor are respectively fed into a catalyst pre-contact tank, the feed amount of propylene raw material is 3.0-10.0 L / h of main catalyst, 4.0-8.0 kg / h of co-catalyst, and 1.0-2.0 kg / h of external electron donor; the materials in the tank are pre-contacted at a constant temperature of 10-15°C, and the reaction time is 10-20 min; S2. Propylene and hydrogen are added to the loop reactor as raw materials, and the prepolymer obtained in step S1 is added to control the amount of hydrogen added to the two loop reactors to be 3000-5000ppm, and the slurry density is 450~500kg / m 3 , the temperature is 60-70°C, the pressure is 3.0-4.0MPa; the reaction time is 1.5-3h; through two loop reactors in series circulation, a homopolymer polypropylene powder with a melt index of 40.00±10g / 10min is obtained; S3. The homopolymerized polypropylene powder obtained in step S2 is transported to a gas phase reactor R401, and subjected to a gas phase copolymerization reaction with ethylene and propylene; the generated binary copolymer mainly composed of ethylene-propylene rubber grows mainly in the ball of the homopolymer, and finally a mixture of a homopolymer and a binary copolymer with an island-in-sea structure is obtained to form an impact copolymer; the temperature of the gas phase reactor R401 is controlled to be 75-80°C, the pressure is 1.30-1.50MPa, and the ethylene content is 8.0-16.0%; the reaction time is 30-50min; it is sent to a gas phase reactor and ethylene is introduced. By controlling and adjusting the hydrogen / ethylene molar ratio to 0.035-0.040, a tiger-skin-grain-resistant stress cracking copolymerized polypropylene powder is obtained; S4. Add compounding additives and nucleating agents to the obtained anti-tiger pattern stress cracking resistant polypropylene powder, mix well, and produce anti-tiger pattern stress cracking resistant polypropylene material by granulation and extrusion; The compound auxiliary agent is one or a mixture of two or more of antioxidants 1010, 626, and 3114, and the addition amount is 2000-3000ppm; The amount of the nucleating agent added is 500-1000 ppm.

2. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 1, characterized in that: The internal electron donor of the Ziegler-Natta catalyst is an organic compound containing nitrogen, phosphorus and silicon or a 1,3-diether compound.

3. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 2, characterized in that: The internal electron donor is 2,2-diisobutyl-1,3-dimethoxypropane.

4. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 1, characterized in that: The external electron donor of the Ziegler-Natta catalyst is an alkoxyalkane compound.

5. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 4, characterized in that: The external electron donor is a composite external electron donor of cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P).

6. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 5, characterized in that: The cyclohexylmethyldimethoxysilane (Donor-C) and diisopropyldimethoxysilane (Donor-P) are mixed in a ratio of 2:

1.

7. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 1, characterized in that: The Ziegler-Natta catalyst has a titanium content of 1.8-4.0%, an ester content of 8-15%, and a polymerization activity of 5×10 4 -10 5 gPP / gCat.

8. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 1, characterized in that: The nucleating agent is one of M161 and RNHS-03 or a mixture of the two.

9. The method for preparing the anti-tiger pattern stress cracking resistant polypropylene material according to claim 1, characterized in that: When the compound auxiliary agent contains two components, the mass ratio is 1:2 to 2:1; when it contains three components, the mass ratio is equal.

10. A tiger-skin-resistant stress-cracking polypropylene material prepared by the method according to any one of claims 1 to 9.

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