Stress-whitening-resistant and high-gloss polypropylene resin material and production method thereof

Abstract

The invention relates to the technical field of high-molecular compounds, and particularly discloses a stress-whitening-resistant and high-gloss polypropylene resin material and a production method thereof. The method specifically comprises the following steps: S1, carrying out a main catalyst activation reaction on a main catalyst, a cocatalyst and an external electron donor, and carrying out a pre-polymerization reaction on the activated main catalyst in a pre-polymerization reactor; s2, the polymer continues to be subjected to a liquid-phase bulk reaction with propylene and hydrogen gas, and polypropylene powder is obtained; s3, continuously carrying out copolymerization reaction on the polypropylene powder and propylene, ethylene and hydrogen gas monomers to obtain block copolymerized polypropylene powder; and S4, granulating and extruding the block copolymerized polypropylene powder obtained in the S3 to obtain the stress whitening-resistant high-gloss impact-resistant polypropylene material. The polypropylene material has good stress whitening resistance and high glossiness on the premise that the bending property, the tensile property and the processability of the block polypropylene are not influenced, and also has relatively high impact resistance.

Description

Technical Field

[0001] The invention relates to the technical field of polymer compounds, and specifically discloses a stress-whitening-resistant, high-gloss polypropylene resin material and a production method. Background Art

[0002] Polypropylene stress whitening refers to the phenomenon that when plastic products are subjected to external forces such as impact, stretching, bending, etc. during manufacturing or use, a large number of microcracks, silver streak gathering areas or voids are generated, thereby reducing the refractive index of this area and making the material appear white.

[0003] Block copolymer polypropylene has good impact resistance, but the ethylene phase in block polypropylene easily induces stress concentration, causing silver streaks. The generation of defective areas affects the performance of polypropylene materials and seriously affects the use of materials. Therefore, in the application fields of automobiles, household appliances, toys and power tools, the stress whitening resistance of polymers urgently needs to be improved.

[0004] At present, all stress-whitening resistance products on the market are processed by modification, usually by mixing different types of materials (such as mixing some homopolymer PP or random copolymer PP to adjust the stress-whitening resistance of block copolymer PP materials), adding fillers and compatibilizers, chemical crosslinking, adding nucleating agents, and adding covering agents to achieve stress-whitening resistance. At present, downstream plastic modification manufacturers usually use block copolymer polypropylene as the base resin, such as SP179, K7726, etc., add talcum powder and toughening agent POE, and the resulting modified resin has improved stress-whitening resistance and no obvious whitening. The graft of polypropylene and maleic anhydride (PP-g-MAH) is used as a compatibilizer to increase the physical interaction between the additive and the matrix, with a flexural modulus of more than 800MPa and an impact performance of more than 10kJ / m 2 .

[0005] However, if a certain method is used alone to improve the stress whitening resistance of a material, other properties of the material (such as impact resistance) will usually decrease. Therefore, it is of great significance to develop products that can improve the stress whitening resistance while maintaining the good impact properties of polypropylene, or even products that simultaneously enhance the stress whitening resistance and other mechanical properties. Summary of the invention

[0006] The concept of the present invention is to synthesize stress-whitening-resistant and high-gloss impact-resistant polypropylene material in one step by using a direct polymerization method, so that the material has high impact resistance and high gloss on the premise of having stress-whitening-resistant function, solves the problem of product performance degradation caused by stress whitening of block copolymer polypropylene in application, and enables the block copolymer polypropylene to be better applied in application fields such as automobiles, household appliances, toys and electric tools.

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

[0008] In a first aspect, the present invention provides a stress-whitening-resistant, high-gloss impact-resistant polypropylene material and a production method, comprising the following steps:

[0009] S1: adding a main catalyst, a co-catalyst and an external electron donor into a catalyst pre-contact tank to perform a main catalyst activation reaction, and the activated main catalyst enters a prepolymerization reactor to perform a prepolymerization reaction;

[0010] S2: The polymer obtained by the reaction of S1 enters the first loop reactor and the second loop reactor to continue to react with propylene, hydrogen and ethylene in a liquid phase to obtain polypropylene powder;

[0011] S3: After the unreacted monomers are removed by flash evaporation, the polypropylene powder enters a vertical gas-phase fluidized bed reactor to continue copolymerization with propylene, ethylene and hydrogen gas monomers to obtain block copolymer polypropylene powder;

[0012] S4: adding compounding aids and nucleating agents to the block copolymer polypropylene powder obtained in S3, and then extruding through a granulation system to obtain a low-temperature resistant, high-impact transparent polypropylene material;

[0013] The prepolymerization reaction conditions described in S1 are a temperature of 15 to 30°C and a pressure of 3.5 to 4.5 MPa; the main catalyst described in S1 is a Ziegler-Natta catalyst; the ratio of vaseline oil to vaseline fat is 3:1 to 7:3; the mass ratio of the sum of vaseline fat and main catalyst is 1:1 to 5:1; the titanium content of the main catalyst is 3.5% to 6.0%; the co-catalyst is triethylaluminum; the aluminum-titanium molar ratio of the main catalyst and the co-catalyst as a whole is 120 to 200; the mass ratio of the co-catalyst to the external electron donor described in S1 is 2:1 to 4:1, and the mass ratio of the co-catalyst to the main catalyst is 0.13:1 to 0.2:1;

[0014] The temperature of the first loop reactor and the second loop reactor described in S2 is 65-70°C, the reaction pressure is 3.5-4.5MPa, the hydrogen concentration is 1500-4100mg / kg, and the loop slurry density is 450-530kg / m 3 ; Melt flow rate of loop reactor 50~110g / 10min;

[0015] The vertical gas phase fluidized bed reactor described in S3 has a reaction temperature of 70-85°C and a reaction pressure of 1.0-2.0 MPa, wherein the gas phase composition has an ethylene / ethylene+propylene molar volume ratio of 0.2-0.4, a hydrogen / ethylene volume ratio of 0.4-0.8, ethylene accounts for 5%-13% of the total gas volume, and a melt flow rate of 15-35 g / 10 min;

[0016] The compound auxiliary agent described in S4 includes a primary antioxidant, an auxiliary antioxidant, a halogen absorber and an antistatic agent; the primary antioxidant is added in an amount of 0.01 to 0.1% of the mass of the polypropylene powder, the auxiliary antioxidant is added in an amount of 0.05 to 0.15% of the mass of the polypropylene powder, the halogen absorber is added in an amount of 0.01 to 0.1% of the mass of the polypropylene powder, and the antistatic agent is added in an amount of 0 to 0.15% of the mass of the polypropylene powder; the nucleating agent is added in an amount of 0 to 0.15% of the mass of the polypropylene powder.

[0017] Preferably, the external electron donor described in S1 is any one of cyclohexylmethyldimethoxysilane and dicyclopentyldimethoxysilane or a mixture of two or more thereof.

[0018] Preferably, the main antioxidant component in S4 includes any one of antioxidant 1010 and antioxidant 1076 or a mixture of two or more thereof.

[0019] Preferably, the auxiliary antioxidant component described in S4 includes any one of antioxidant 168 and antioxidant 626 or a mixture of two or more thereof.

[0020] Preferably, the halogen absorbent component described in S4 includes any one of calcium stearate, zinc stearate, and synthetic hydrotalcite, or a mixture of two or more thereof.

[0021] Preferably, the antistatic agent described in S4 is glyceryl monostearate.

[0022] Preferably, the nucleating agent described in S4 is any one of Hyperform HPN-68L, HPN-20E, HPN-900ei, HPN-715, HPN-505, or a mixture of two or more thereof.

[0023] Preferably, the barrel temperature of the granulation system in S4 is 220-240°C.

[0024] Furthermore, the granulation water temperature of the granulation system in S4 is 45-55°C.

[0025] In a second aspect, the present invention provides a method according to the first aspect for producing a stress-whitening-resistant, high-gloss impact-resistant polypropylene material.

[0026] Beneficial effects achieved by the present invention:

[0027] The invention provides a stress whitening resistant, high-gloss impact-resistant polypropylene material, which has good stress whitening resistance and high gloss while maintaining the bending performance, tensile performance and processing performance of block polypropylene unaffected, and the polypropylene material still has high impact resistance; it does not need to add fillers and compatibilizers, chemical crosslinking, nucleating agents and covering agents to achieve the stress whitening resistance; it does not need to mix random copolymerized polypropylene or homopolymerized polypropylene with block copolymerized polypropylene to make the product have the stress whitening resistance; during polymerization, the rubber phase content and size are controlled by controlling the melt index and yield in a loop reactor and a vertical gas phase fluidized bed reactor, and the invention has the characteristics of simple operation and low requirements on equipment and technology.

[0028] The melt flow rate of the obtained polypropylene material is 15-35g / 10min, and the cantilever beam impact strength at room temperature of 23°C is ≥15kJ / m 2 , bending modulus ≥ 1000MPa, tensile yield stress ≥ 24MPa, yellow index ≤ -2, gloss (60°) ≥ 90%. The rubber phase content of the polypropylene material is 15%-25%, the rubber phase particle size distribution is 60-250nm, and d50 is 130nm. Whitening factor ≤ 1, whitening index ≤ 0.6. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The SEM image and particle size distribution diagram of the polypropylene prepared in Example 3 of the present invention.

[0030] Figure 2 The SEM image and particle size distribution diagram of the polypropylene prepared in Comparative Example 2 of the present invention.

[0031] Figure 3 The whiteness test graph and the sample state graph before and after the hammer drop when testing the whitening factor and whitening index of the polypropylene prepared in Example 3 of the present invention;

[0032] (a) Before the hammer is dropped; (b) After the hammer is dropped.

[0033] Figure 4 The whiteness test graph and the sample state graph before and after the hammer drop when testing the whitening factor and whitening index of the polypropylene prepared in Comparative Example 2 of the present invention;

[0034] (a) Before the hammer is dropped; (b) After the hammer is dropped. 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] It should be noted that the present invention is not limited to the following examples. The methods are conventional methods unless otherwise specified. The raw materials can be obtained from public commercial channels unless otherwise specified.

[0037] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0038] The performance test standards in each embodiment are as follows:

[0039] (1) Melt flow rate: GB / T 3682.1-2018

[0040] (2) Tensile yield stress: GB / T 1040.1-2018

[0041] (3) Flexural modulus: GB / T 9341-2008

[0042] (4) Izod impact strength: GB / T 1843-2008

[0043] (5) Yellow index: GB / T 39822-2021

[0044] (6) Glossiness: GB 8807-88

[0045] (7) Whiteness: GB / T 2913-1982.

[0046] Example 1

[0047] The production device adopts the Spheripol second-generation loop tube process, the main catalyst contains 4.9% titanium, the co-catalyst is triethylaluminum, the external electron donor is cyclohexylmethyldimethoxysilane, and the catalyst system aluminum-titanium ratio is 150.

[0048] Prepolymerization: The main catalyst, co-catalyst and external electron donor are configured into slurry, and then enter the prepolymerization reactor to react with propylene. The reactor temperature is 18°C, the reaction pressure is 3.8MPa, the catalyst contains 4.9% titanium, the ratio of vaseline oil to vaseline fat is 3:1, the mass ratio of co-catalyst to external electron donor is 3.0, and the ratio of co-catalyst to co-catalyst is 0.16.

[0049] Liquid phase bulk polymerization: The reaction temperature of the first loop reactor is 69°C, the reaction pressure is 3.7MPa, and the slurry density is 490kg / m 3 , hydrogen density 1500ppm, yield 52%. The temperature of the second loop reactor is 69℃, the reaction pressure is 3.7MPa, and the slurry density is 490kg / m 3, hydrogen density is 1500ppm, the yield is 40%, and after passing through the loop reactor, the polypropylene melt flow rate is 80.6g / 10min.

[0050] Gas phase copolymerization: The reaction temperature of the gas phase copolymerization reactor is 78°C, the reaction pressure is 1.4MPa, the molar volume ratio of ethylene to ethylene + propylene is 0.2, the molar volume ratio of hydrogen to ethylene is 0.4, ethylene accounts for 8% of the total gas volume, the yield is 23%, and the polypropylene melt flow rate is 18.0g / 10min.

[0051] Granulation part: the cylinder temperature is 240°C, the granule water temperature is 55°C. The compound additives are antioxidant 1010 added in an amount of 0.045%, antioxidant 168 added in an amount of 0.09%, calcium stearate added in an amount of 0.05%, and nucleating agent HPN-20E added in an amount of 0.08%.

[0052] The test method of whitening factor and whitening index is as follows: a 2cm diameter impact hammer weighing 500g is freely dropped from a height of 2m and falls on a preparation with the size of 61mm×61mm×1mm. After the impact, the diameter of the whitening ring on the preparation and the whiteness value of the same area before and after the impact are measured on the same area before and after the specific time. Whitening factor = whitening diameter × (whiteness value after impact - whiteness value before impact); whitening index = diameter of whitening ring / diameter of the impact ball used.

[0053] Embodiment 2-6

[0054] The production process is the same as in Example 1, but the process conditions are appropriately changed, as shown in Table 1.

[0055] Comparative Examples 1-3

[0056] The production process is the same as in Example 1, but the process conditions are appropriately changed, as shown in Table 1.

[0057] Under the conditions of Examples 1-6 and Comparative Examples 1-3, the performance indicators of the products are shown in Table 2.

[0058] Test results

[0059]

[0060]

[0061]

[0062] The above is a detailed introduction to a stress-whitening-resistant, high-gloss impact-resistant polypropylene material and a production method provided by the present invention. The above is only an exemplary embodiment and cannot be used to limit the protection scope of the present invention. Equal changes and improvements made within the scope of the application of the present invention still belong to the patent scope of the present invention.

Claims

1. A stress-whitening-resistant, high-gloss impact-resistant polypropylene material and a production method, characterized in that: The following steps are involved: S1: adding a main catalyst, a co-catalyst and an external electron donor into a catalyst pre-contact tank to carry out an activation reaction of the main catalyst, and the activated main catalyst enters a prepolymerization reactor to carry out a prepolymerization reaction; S2: The polymer obtained by the reaction of S1 enters the first loop reactor and the second loop reactor to continue to react with propylene, hydrogen and ethylene in a liquid phase to obtain polypropylene powder; S3: After the unreacted monomers are removed by flash evaporation, the polypropylene powder enters a vertical gas-phase fluidized bed reactor to continue copolymerization with propylene, ethylene and hydrogen gas monomers to obtain block copolymer polypropylene powder; S4: adding compounding aids and nucleating agents to the block copolymer polypropylene powder obtained in S3, and then extruding through a granulation system to obtain a low-temperature resistant, high-impact transparent polypropylene material; The prepolymerization reaction conditions described in S1 are a temperature of 15 to 30°C and a pressure of 3.5 to 4.5 MPa; the main catalyst described in S1 is a Ziegler-Natta catalyst; the ratio of vaseline oil to vaseline fat is 3:1 to 7:3; the mass ratio of the sum of vaseline fat and main catalyst is 1:1 to 5:1; the titanium content of the main catalyst is 3.5% to 6.0%; the co-catalyst is triethylaluminum; the aluminum-titanium molar ratio of the main catalyst and the co-catalyst as a whole is 120 to 200; the mass ratio of the co-catalyst to the external electron donor described in S1 is 2:1 to 4:1, and the mass ratio of the co-catalyst to the main catalyst is 0.13:1 to 0.2:1; The temperature of the first loop reactor and the second loop reactor described in S2 is 65-70°C, the reaction pressure is 3.5-4.5MPa, the hydrogen concentration is 1500-4100mg / kg, and the loop slurry density is 450-530kg / m 3 ; The vertical gas phase fluidized bed reactor described in S3 has a reaction temperature of 70-85°C and a reaction pressure of 1.0-2.0 MPa, wherein the gas phase composition has an ethylene / ethylene+propylene molar volume ratio of 0.2-0.4, a hydrogen / ethylene volume ratio of 0.4-0.8, and ethylene accounts for 5%-13% of the total gas volume; The compound auxiliary agent described in S4 includes a primary antioxidant, an auxiliary antioxidant, a halogen absorber and an antistatic agent; the primary antioxidant is added in an amount of 0.01 to 0.1% of the mass of the polypropylene powder, the auxiliary antioxidant is added in an amount of 0.05 to 0.15% of the mass of the polypropylene powder, the halogen absorber is added in an amount of 0.01 to 0.1% of the mass of the polypropylene powder, and the antistatic agent is added in an amount of 0 to 0.15% of the mass of the polypropylene powder; the nucleating agent is added in an amount of 0 to 0.15% of the mass of the polypropylene powder.

2. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 1, characterized in that: The external electron donor described in S1 is any one of cyclohexylmethyldimethoxysilane and dicyclopentyldimethoxysilane, or a mixture of two or more thereof.

3. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 1, characterized in that: The main antioxidant component in S4 includes any one of antioxidant 1010 and antioxidant 1076 or a mixture of two or more thereof.

4. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 1, characterized in that: The auxiliary antioxidant component described in S4 includes any one of antioxidant 168 and antioxidant 626 or a mixture of two or more thereof.

5. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 1, characterized in that: The halogen absorbent component described in S4 includes any one of calcium stearate, zinc stearate, and synthetic hydrotalcite, or a mixture of two or more thereof.

6. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 1, characterized in that: The antistatic agent described in S4 is glyceryl monostearate.

7. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 1, characterized in that: The nucleating agent described in S4 is any one of Hyperform HPN-68L, HPN-20E, HPN-900ei, HPN-715, HPN-505, or a mixture of two or more thereof.

8. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 1, characterized in that: The barrel temperature of the granulation system in S4 is 220-240°C.

9. The stress-whitening-resistant, high-gloss impact-resistant polypropylene material and production method according to claim 8, characterized in that: The granulation water temperature of the granulation system in S4 is 45-55°C.

10. A stress-whitening-resistant, high-gloss impact-resistant polypropylene material produced by the method of any one of claims 1 to 9.

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