Method for preparing polypropylene with high melt strength by taking divinyl benzene as monomer

Abstract

The invention discloses a method for preparing high-melt-strength polypropylene by taking divinyl benzene as a monomer, belongs to the technical field of high polymer materials, and particularly relates to a preparation method of the high-melt-strength polypropylene. The invention particularly relates to a method for preparing high-melt-strength polypropylene by using divinyl benzene as monomer long-chain branched modified polypropylene. The invention aims to solve the problem of low melt strength of polypropylene. The method is a water phase suspension method and comprises the following steps: swelling polypropylene, a divinyl benzene monomer, an interface agent, a co-monomer, deionized water, an antioxidant and an initiator, then carrying out a grafting reaction, washing, extracting and drying. According to the invention, the divinyl benzene is used as a monomer for long-chain branching modification of polypropylene, and the method has the advantages of good processing effect, simple process, environmental protection and low cost. The high-melt-strength polypropylene prepared by the method is mainly used in the fields of electronics, electric appliances, packaging, light industry, buildings, automobiles and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and specifically relates to a method for preparing high melt strength polypropylene; in particular, it relates to a method for preparing high melt strength polypropylene by using divinylbenzene as a monomer to modify long-chain branched polypropylene. Background Art

[0002] Polypropylene is one of the most widely used and fastest growing resins in the world. Compared with other general thermoplastic resins (polyethylene, polyvinyl chloride and polystyrene), it has many advantages such as light weight, easy degradability, easy recycling, non-toxicity, good chemical corrosion resistance and low price. However, it also has disadvantages. Poor sag resistance and poor toughness limit the application of polypropylene in the fields of thermoforming and extrusion coating. High melt strength polypropylene has good thermal stability, wide processing temperature, good sag resistance and strain hardening characteristics, which greatly broadens the application range of polypropylene. In recent years, polypropylene has developed into one of the indispensable basic raw materials for packaging, light industry, construction, electronics, electrical appliances, automobiles and other industries.

[0003] Since the advent of high melt strength polypropylene, it has been favored by domestic and foreign research institutions. There are many types of high melt strength polypropylene for sale abroad. Although there are many high melt strength polypropylene products in China, there is still a big gap with foreign countries. At present, the methods for preparing high melt strength polypropylene are generally divided into two categories. One is the post-modification method, that is, modifying the commercial polypropylene, and the other is the catalytic polymerization method, that is, introducing the long chain branching structure into the polypropylene molecular chain through catalytic polymerization. The post-modification method is simple to operate and easy to implement, so it is a method that is widely used in the preparation of high melt strength polypropylene. It mainly modifies linear polypropylene through free radical reactions. Due to the complexity of free radical reactions, there are two major problems in the preparation of high melt strength polypropylene by post-modification methods. One is the degradation and gelation of polypropylene; the other is the competition between polymer grafting and monomer homopolymerization, and the competition between polymer main chain B-bond breaking and crosslinking and branching. In addition, the processing technology of this preparation method is difficult to control, so that the obtained high melt strength polypropylene is usually a mixture of various products. Summary of the invention

[0004] The present invention aims to solve the problem of low melt strength of polypropylene, which in turn affects the application performance, and thus invents a method for preparing high melt strength polypropylene using divinylbenzene as a monomer.

[0005] A method for preparing high melt strength polypropylene using divinylbenzene as a monomer is specifically carried out according to the following steps:

[0006] Step 1, adding polypropylene, divinylbenzene, an interfacial agent, a comonomer, deionized water, an antioxidant and an initiator into a reactor, controlling the temperature to 40-80° C. for swelling, and then controlling the temperature to 80-95° C. for grafting reaction to obtain modified polypropylene;

[0007] Step 2: Wash the modified polypropylene obtained in step 1, then extract it with acetone, control the extraction time to be 2 to 12 hours, and then dry it to obtain the high melt strength polypropylene, thereby completing the preparation.

[0008] Furthermore, the weight ratio of the polypropylene, divinylbenzene, interfacial agent, comonomer, deionized water, antioxidant and initiator in step 1 is 1: (0.5-8): (0.04-0.15): (0.1-0.4): (1-6): (0.001-0.006): (0.001-0.008).

[0009] Furthermore, the interface agent in step 1 is one or a mixture of benzene, toluene, xylene and cyclohexane.

[0010] Furthermore, the comonomer in step 1 is one or a mixture of two of styrene and acrylic acid.

[0011] Furthermore, the antioxidant in step 1 is one of tetrakis[B-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, tris[2,4-di-tert-butylphenyl]phosphite, B-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 1.1.3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane and bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite, or a mixture of several of them.

[0012] Furthermore, the initiator in step 1 is one of diisopropylbenzene peroxide, dibenzoyl peroxide, azobisisobutyronitrile, tert-butyl perbenzoate, bis(2-phenylethoxy) peroxydicarbonate, dicyclopentadiene and ammonium persulfate, or a mixture of several of them.

[0013] Furthermore, the swelling time in step 1 is 20 minutes to 5 hours.

[0014] Furthermore, the grafting reaction time in step 1 is 0.5 to 8 hours.

[0015] Furthermore, in step 2, deionized water and anhydrous ethanol are used for washing in sequence.

[0016] Furthermore, in step 2, the drying temperature is controlled to be 35-70°C.

[0017] The present invention discloses a method for modifying polypropylene by long-chain branching by using divinylbenzene as a monomer. The method adopted by the present invention is a water-phase suspension grafting method, which has the characteristics of good working effect, simple process, green environmental protection and low cost, and has good application prospects.

[0018] Beneficial effects of the present invention:

[0019] The method of the present invention adjusts the grafting effect of high melt strength polypropylene by adjusting the preparation process after a certain amount of polypropylene, divinylbenzene, interface agent, comonomer, deionized water, antioxidant and initiator are swollen at a certain temperature. The method is used to enhance the melt strength of polypropylene and further improve the application performance. The method has the characteristics of good working effect, simple process, green environmental protection and low cost, and has good application prospects.

[0020] According to tests, the mechanical properties of polypropylene modified by long-chain branching are greatly improved, and high melt strength polypropylene with ideal properties is prepared.

[0021] The high melt strength polypropylene prepared by the method of the present invention is mainly used in the fields of electronics, electrical appliances, packaging, light industry, construction, automobiles, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FT-IR image of the original polypropylene roughened film;

[0023] Figure 2 is the XRD image of the original polypropylene roughened film;

[0024] Figure 3 DMA image of the original polypropylene roughened film;

[0025] Figure 4 FT-IR image of high melt strength polypropylene prepared in Example 1;

[0026] Figure 5 XRD pattern of high melt strength polypropylene prepared in Example 1;

[0027] Figure 6 This is a DMA image of the high melt strength polypropylene prepared in Example 1. DETAILED DESCRIPTION

[0028] Specific implementation method 1: This implementation method is a method for preparing high melt strength polypropylene using divinylbenzene as a monomer, which is specifically carried out according to the following steps:

[0029] Step 1, adding polypropylene, divinylbenzene, an interfacial agent, a comonomer, deionized water, an antioxidant and an initiator into a reactor, controlling the temperature to 40-80° C. for swelling, and then controlling the temperature to 80-95° C. for grafting reaction to obtain modified polypropylene;

[0030] Step 2: Wash the modified polypropylene obtained in step 1, then extract it with acetone, control the extraction time to be 2 to 12 hours, and then dry it to obtain the high melt strength polypropylene, thereby completing the preparation.

[0031] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the weight ratio of polypropylene, divinylbenzene, interfacial agent, comonomer, deionized water, antioxidant and initiator in step 1 is 1: (0.5-8): (0.04-0.15): (0.1-0.4): (1-6): (0.001-0.006): (0.001-0.008). Others are the same as specific embodiments 1 to 9.

[0032] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: the interface agent in step 1 is one or a mixture of benzene, toluene, xylene and cyclohexane. The rest is the same as specific implementation method 1 or 2.

[0033] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the comonomer in step 1 is a mixture of one or both of styrene and acrylic acid. The rest is the same as specific embodiments 1 to 3.

[0034] Specific embodiment 5: This embodiment is different from specific embodiments 1 to 4 in that: the antioxidant in step 1 is one or a mixture of tetrakis[B-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester, tris[2,4-di-tert-butylphenyl] phosphite, B-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 1.1.3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl) butane and bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite. Others are the same as specific embodiments 1 to 4.

[0035] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that: the initiator in step 1 is one of diisopropylbenzene peroxide, dibenzoyl peroxide, azobisisobutyronitrile, tert-butyl perbenzoate, bis(2-phenylethoxy) peroxydicarbonate, dicyclopentadiene and ammonium persulfate, or a mixture of several of them. The rest is the same as specific embodiments 1 to 5.

[0036] Specific implementation method 7: This implementation method is different from specific implementation methods 1 to 6 in that the swelling time in step 1 is 20 minutes to 5 hours. The rest is the same as specific implementation methods 1 to 6.

[0037] Specific embodiment 8: This embodiment is different from specific embodiments 1 to 7 in that the grafting reaction time in step 1 is 0.5 to 8 hours. The rest is the same as specific embodiments 1 to 7.

[0038] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: step 2 uses deionized water and anhydrous ethanol to wash in sequence. The rest is the same as specific embodiments 1 to 8.

[0039] Specific embodiment 10: This embodiment is different from specific embodiments 1 to 9 in that the drying temperature in step 2 is controlled to be 35-70° C. The rest is the same as specific embodiments 1 to 9.

[0040] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0041] Embodiment 1:

[0042] This embodiment provides a method for preparing high melt strength polypropylene using divinylbenzene as a monomer, which is specifically carried out in the following steps:

[0043] Step 1: add 10g polypropylene, 1g divinylbenzene, 2g xylene, 4g styrene, 25g deionized water, 0.02g antioxidant 1010 and 0.04g DCP into a reactor, control the temperature to 60°C for swelling for 1h, and then control the temperature to 90°C for grafting reaction for 4h to obtain modified polypropylene;

[0044] Step 2: Wash the modified polypropylene obtained in step 1 three times with deionized water and anhydrous ethanol respectively, then extract with acetone for 6 hours, and then dry at 60° C. to obtain the high melt strength polypropylene, thereby completing the preparation.

[0045] Embodiment 2:

[0046] This embodiment provides a method for preparing high melt strength polypropylene using divinylbenzene as a monomer, which is specifically carried out in the following steps:

[0047] Step 1: add 10g polypropylene, 2g divinylbenzene, 2g cyclohexane, 4g acrylic acid, 25g deionized water, 0.02g antioxidant 1076 and 0.02g AIBN into a reactor, control the temperature to 60°C for swelling for 1h, and then control the temperature to 90°C for grafting reaction for 4h to obtain modified polypropylene;

[0048] Step 2: Wash the modified polypropylene obtained in step 1 three times with deionized water and anhydrous ethanol respectively, then extract with acetone for 6 hours, and then dry at 60° C. to obtain the high melt strength polypropylene, thereby completing the preparation.

[0049] Embodiment 3:

[0050] This embodiment provides a method for preparing high melt strength polypropylene using divinylbenzene as a monomer, which is specifically carried out in the following steps:

[0051] Step 1: add 10g polypropylene, 4g divinylbenzene, 2g xylene, 3g styrene, 20g deionized water, 0.02g antioxidant 168 and 0.04g DCP into a reactor, control the temperature to 60°C for swelling for 2h, and then control the temperature to 90°C for grafting reaction for 4h to obtain modified polypropylene;

[0052] Step 2: Wash the modified polypropylene obtained in step 1 three times with deionized water and anhydrous ethanol respectively, then extract with acetone for 8 hours, and then dry at 60° C. to obtain the high melt strength polypropylene, thereby completing the preparation.

[0053] Embodiment 4:

[0054] This embodiment provides a method for preparing high melt strength polypropylene using divinylbenzene as a monomer, which is specifically carried out in the following steps:

[0055] Step 1: add 10 g polypropylene, 6 g divinylbenzene, 4 g cyclohexane, 3 g acrylic acid, 40 g deionized water, 0.04 g antioxidant 1076 and 0.08 g BPO into a reactor, control the temperature at 60° C. to swell for 2 h, and then control the temperature at 90° C. to carry out grafting reaction for 4 h to obtain modified polypropylene;

[0056] Step 2: Wash the modified polypropylene obtained in step 1 three times with deionized water and anhydrous ethanol respectively, then extract with acetone for 12 hours, and then dry at 60° C. to obtain the high melt strength polypropylene, thereby completing the preparation.

[0057] From the test data in the attached figure, it can be seen that compared with the characterization and test of the roughened polypropylene film in the comparative example, the molecular structure of the divinylbenzene grafted polypropylene in the FT-IR image of the long-chain branched modified polypropylene using divinylbenzene as the monomer in Example 1 of the present invention has not changed significantly. The XRD image of the long-chain branched modified polypropylene using divinylbenzene as the monomer in Example 1 shows that the crystallization of the modified polypropylene is ideal. Figure 5 It appeared in Figure 2The α-crystal form in the embodiment corresponds to the 14.0° 110 crystal plane, the 16.9° 040 crystal plane, the 18.4° 130 crystal plane, the 21.4° 101 crystal plane, the 21.9° 131 crystal plane, and the 16.0° 300 crystal plane corresponding to the β-crystal form. The DMA image of the long-chain branched modified polypropylene using divinylbenzene as a monomer in Example 1 shows that the mechanical properties of the long-chain branched modified polypropylene at 30-150°C are greatly improved. At 30°C, the storage modulus is increased by more than 5%, and the loss modulus is increased by more than 7%; at 140°C, the storage modulus is increased by more than 20%, and the loss modulus is increased by more than 20%, and the high melt strength polypropylene with ideal performance is prepared.

Claims

1. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer, characterized in that The method is specifically carried out in the following steps: Step 1, adding polypropylene, divinylbenzene, an interfacial agent, a comonomer, deionized water, an antioxidant and an initiator into a reactor, controlling the temperature to 40-80° C. for swelling, and then controlling the temperature to 80-95° C. for grafting reaction to obtain modified polypropylene; Step 2: Wash the modified polypropylene obtained in step 1, then extract it with acetone, control the extraction time to be 2 to 12 hours, and then dry it to obtain the high melt strength polypropylene, thereby completing the preparation.

2. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that The weight ratio of the polypropylene, divinylbenzene, interfacial agent, comonomer, deionized water, antioxidant and initiator in step 1 is 1: (0.5-8): (0.04-0.15): (0.1-0.4): (1-6): (0.001-0.006): (0.001-0.008).

3. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that The interface agent in step 1 is one or a mixture of benzene, toluene, xylene and cyclohexane.

4. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that The comonomer in step 1 is one or a mixture of styrene and acrylic acid.

5. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that The antioxidant in step 1 is pentaerythritol tetrakis[B-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tris[2,4-di-tert-butylphenyl]phosphite, B-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 1.1.3-Tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane and bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite or a mixture of several thereof.

6. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that The initiator in step 1 is one of diisopropylbenzene peroxide, dibenzoyl peroxide, azobisisobutyronitrile, tert-butyl perbenzoate, bis(2-phenylethoxy) peroxydicarbonate, dicyclopentadiene and ammonium persulfate, or a mixture of several of them.

7. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that The swelling time in step 1 is 20 minutes to 5 hours.

8. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that The grafting reaction time in step 1 is 0.5 to 8 hours.

9. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that Step 2: washing with deionized water and anhydrous ethanol in sequence.

10. A method for preparing high melt strength polypropylene using divinylbenzene as a monomer according to claim 1, characterized in that Step 2: Control the drying temperature to 35-70°C.

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