Preparation method of long-chain branched modified polypropylene

Abstract

The invention discloses a preparation method of long-chain branched modified polypropylene, and belongs to the technical field of high polymer materials. The invention discloses a preparation method of long-chain branched modified polypropylene, which is a water phase suspension method and specifically comprises the following steps: adding polypropylene, an acrylic acid n-alkyl ester monomer, an interface agent, a co-monomer, deionized water, an antioxidant and an initiator into a reactor according to a certain weight ratio; the preparation method comprises the following steps: swelling at a certain temperature for a certain time, then carrying out a reaction at a certain temperature for a certain time, and finally washing, extracting and drying. According to the invention, the acrylic acid n-alkyl ester is used as a monomer for long-chain branching modification of polypropylene, and the problem of low melt strength of polypropylene is solved. The method has the advantages of simple process, environmental protection, low cost, good processing effect and the like.

Description

Technical Field

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

[0002] Polypropylene (PP) is a high molecular compound obtained by polymerization of propylene. It is one of the four major types of thermoplastics (polyethylene, polyvinyl chloride, polystyrene, and polypropylene). It has become an indispensable basic raw material for packaging, light industry, electronics, electrical appliances, construction, and automobile industries due to its rich raw material sources, low production cost, low density, high melting point, good chemical stability, high product transparency, non-toxicity, and easy processing.

[0003] However, due to the linear structure of the polypropylene macromolecular chain, polypropylene has many defects, such as poor toughness, large molding shrinkage, easy brittle cracking at low temperature, insufficient resistance, poor aging resistance, low heat deformation temperature, low melt strength in the molten state, and the melt cannot show strain hardening effect, which directly causes some defects of polypropylene during melt processing, including edge curling and shrinkage during high-speed extrusion coating, sag and local thinning during thermoforming, unstable fluid flow during co-extrusion of multi-layer structures, and cell collapse during extrusion foaming, difficulty in film blowing and preparation of foamed products, etc. Due to these defects, the application of polypropylene in thermoforming, blow molding, foaming and other molding processing fields is severely limited.

[0004] Introducing long-chain branching structure into the polypropylene molecular chain is an effective method to improve the melt properties of polypropylene. The long-chain branching structure can significantly improve the melt properties of polypropylene and improve problems such as poor toughness and brittle cracking at low temperatures. At present, the preparation methods of long-chain branched polypropylene are generally divided into two categories, one is the post-modification method, that is, modifying 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 mainly divided into melt grafting method, solution grafting method, suspension grafting method, solid phase grafting method and radiation grafting method.

[0005] The suspension grafting method has attracted widespread attention in recent years and has broad application prospects due to its simple synthesis process, mild reaction conditions, low system viscosity, uniform mixing of reaction materials, easy product post-processing and green environmental protection. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of low melt strength, poor toughness, brittle cracking at low temperature and the like of existing polypropylene, which further affect the application of polypropylene, and to provide a preparation method of polypropylene modified by long-chain branching of n-alkyl acrylate.

[0007] A method for preparing long-chain branched modified polypropylene is specifically carried out according to the following steps:

[0008] 1. Add 1 part of polypropylene, 0.04 to 0.8 parts of n-alkyl acrylate monomer, 0.02 to 0.15 parts of interface agent, 0.1 to 0.4 parts of comonomer, 1 to 6 parts of deionized water, 0.001 to 0.006 parts of antioxidant and 0.001 to 0.008 parts of initiator into the reactor, and swell at a certain temperature for a certain time;

[0009] The n-alkyl acrylate monomer described in step 1 is one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, behenyl acrylate, tetradecyl acrylate and tetratridecyl acrylate;

[0010] 2. Raising the temperature of the reactor, and carrying out a grafting reaction at a certain temperature for a certain period of time to obtain a reaction product;

[0011] 3. First, the reaction product is washed, then extracted with acetone, and finally dried to obtain long-chain branched modified polypropylene.

[0012] Principle of the present invention:

[0013] The present invention adopts a water phase suspension method, firstly swells the polypropylene at a certain temperature, so that reactants such as initiators and monomers are mixed more fully with the polypropylene; then the temperature is increased to start the reaction, and the n-alkyl acrylate monomer is grafted onto the polypropylene molecular chain. Since the n-alkyl acrylate monomer is introduced into the polypropylene molecular chain, the polypropylene has a long-chain branched structure, and due to the effect of the long chain branches, entanglements are generated between the polypropylene molecules. At the same time, the long chain branches also reduce the free volume of the polypropylene, greatly improving the melt strength of the polypropylene.

[0014] Advantages of the present invention:

[0015] 1. The present invention adjusts the grafting effect of long-chain branched modified polypropylene by adjusting the preparation process after a certain amount of polypropylene, n-alkyl acrylate monomer, interface agent, comonomer, deionized water, antioxidant and initiator are swollen at a certain temperature; it is used to solve the problems of low melt strength, poor toughness, easy brittle cracking at low temperature of polypropylene, and thus improve the application performance of polypropylene.

[0016] Second, the present invention adopts a simple and environmentally friendly aqueous suspension method to graft the n-alkyl acrylate monomer onto the polypropylene molecular chain, thereby changing the molecular structure of the polypropylene, preparing long-chain branched polypropylene, and improving the melt strength of the polypropylene.

[0017] 3. The aqueous suspension method adopted in the present invention has the advantages of simple process, green environmental protection, low cost and good processing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FT-IR image of pristine polypropylene;

[0019] Figure 2 is the XRD pattern of pristine polypropylene;

[0020] Figure 3 DMA image of pristine polypropylene;

[0021] Figure 4 FT-IR image of the long-chain branched modified polypropylene prepared in Example 1;

[0022] Figure 5 XRD pattern of the long-chain branched modified polypropylene prepared in Example 1;

[0023] Figure 6 DMA image of the long-chain branched modified polypropylene prepared in Example 1;

[0024] Figure 7 FT-IR image of the long-chain branched modified polypropylene prepared in Example 2;

[0025] Figure 8 XRD pattern of the long-chain branched modified polypropylene prepared in Example 2;

[0026] Fig. 9 DMA image of the long-chain branched modified polypropylene prepared in Example 2;

[0027] Fig.10 FT-IR image of the long-chain branched modified polypropylene prepared in Example 3;

[0028] Fig.11 XRD pattern of the long-chain branched modified polypropylene prepared in Example 3;

[0029] Fig.12 DMA image of the long-chain branched modified polypropylene prepared in Example 3;

[0030] Fig.13 FT-IR image of the long-chain branched modified polypropylene prepared in Example 4;

[0031] Fig.14 XRD pattern of the long-chain branched modified polypropylene prepared in Example 4;

[0032] Fig.15 This is the DMA image of the long-chain branched modified polypropylene prepared in Example 4. DETAILED DESCRIPTION

[0033] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0034] Specific implementation method 1: This implementation method is a method for preparing long-chain branched modified polypropylene, which is specifically carried out according to the following steps:

[0035] 1. Add 1 part of polypropylene, 0.04 to 0.8 parts of n-alkyl acrylate monomer, 0.02 to 0.15 parts of interface agent, 0.1 to 0.4 parts of comonomer, 1 to 6 parts of deionized water, 0.001 to 0.006 parts of antioxidant and 0.001 to 0.008 parts of initiator into the reactor, and swell at a certain temperature for a certain time;

[0036] The n-alkyl acrylate monomer described in step 1 is one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, behenyl acrylate, tetradecyl acrylate and tetratridecyl acrylate;

[0037] 2. Raising the temperature of the reactor, and carrying out a grafting reaction at a certain temperature for a certain period of time to obtain a reaction product;

[0038] 3. First, the reaction product is washed, then extracted with acetone, and finally dried to obtain long-chain branched modified polypropylene.

[0039] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the interface agent in step 1 is one or more of benzene, toluene and cyclohexane. The other steps are the same as those in specific implementation method 1.

[0040] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the comonomer in step 1 is acrylic acid. The other steps are the same as those in specific implementation method 1 or 2.

[0041] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the antioxidant described in step 1 is one or more of tris[2,4-di-tert-butylphenyl]phosphite, 2,2'-methylenebis(4-methyl-6-tert-butylphenol) and bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite. The other steps are the same as those of specific embodiments 1 to 3.

[0042] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the initiator in step 1 is one or more of azobisisobutyronitrile, dicyclopentadiene or ammonium persulfate. The other steps are the same as those of specific embodiments 1 to 4.

[0043] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that: in step 1, swelling is performed at 40° C. to 80° C. for 30 min to 240 min. The other steps are the same as those of specific embodiments 1 to 5.

[0044] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that: in step 2, the grafting is carried out at 75° C. to 95° C. for 30 min to 480 min. The other steps are the same as those of specific embodiments 1 to 6.

[0045] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the washing in step 3 is washing with deionized water and anhydrous ethanol 3 to 4 times respectively. The other steps are the same as those of specific embodiments 1 to 7.

[0046] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the extraction time using acetone in step 3 is 2 hours to 24 hours. The other steps are the same as those of specific embodiments 1 to 8.

[0047] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the drying temperature in step 3 is 40° C. to 75° C. The other steps are the same as those in specific embodiments 1 to 9.

[0048] The following examples are used to verify the beneficial effects of the present invention:

[0049] Embodiment 1: A method for preparing long-chain branched modified polypropylene is specifically completed according to the following steps:

[0050] 1. Add 10g polypropylene, 0.25g octadecyl acrylate, 0.2g cyclohexane, 4g acrylic acid, 25g deionized water, 0.02g antioxidant 168 and 0.04g DCPD into the reactor and swell at 60°C for 1 hour.

[0051] Step 2, raising the temperature of the reactor to 90°C, and carrying out a grafting reaction at 90°C for 4 hours;

[0052] Step 3: Wash with deionized water and anhydrous ethanol three times respectively, then extract with acetone for 12 hours, and finally dry at 60° C. to obtain long-chain branched modified polypropylene.

[0053] Embodiment 2: A method for preparing long-chain branched modified polypropylene is specifically completed according to the following steps:

[0054] 1. Add 10g polypropylene, 0.5g octadecyl acrylate, 0.2g cyclohexane, 3g acrylic acid, 25g deionized water, 0.02g antioxidant 168 and 0.02g AIBN into the reactor and swell at 60°C for 1 hour.

[0055] 2. Raise the temperature of the reactor to 80°C and carry out the grafting reaction at 80°C for 6 hours;

[0056] 3. Wash with deionized water and anhydrous ethanol three times respectively, then extract with acetone for 6 hours, and finally dry at 45°C to obtain long-chain branched modified polypropylene.

[0057] Embodiment 3: A method for preparing long-chain branched modified polypropylene is specifically completed according to the following steps:

[0058] 1. Add 10g polypropylene, 1g tetradecyl acrylate, 0.2g cyclohexane, 4g acrylic acid, 20g deionized water, 0.02g antioxidant 1010 and 0.04g AIBN into the reactor and swell at 60°C for 2 hours.

[0059] 2. Raise the temperature of the reactor to 85°C and carry out the grafting reaction at 85°C for 4 hours;

[0060] 3. Wash with deionized water and anhydrous ethanol three times respectively, then extract with acetone for 24 hours, and finally dry at 50°C to obtain long-chain branched modified polypropylene.

[0061] Embodiment 4: A method for preparing long-chain branched modified polypropylene is specifically completed according to the following steps:

[0062] Step 1: 10 g polypropylene, 2 g tetradecyl acrylate monomer, 0.4 g cyclohexane, 4 g acrylic acid, 40 g deionized water, 0.04 g antioxidant 168 and 0.08 g DCPD were added into a reactor and first swelled at 60° C. for 2 hours;

[0063] Step 2, raising the temperature of the reactor to 90°C, and carrying out a grafting reaction at 90°C for 8 hours;

[0064] Step 3: Wash with deionized water and anhydrous ethanol three times respectively, then extract with acetone for 12 hours, and finally dry at 60° C. to obtain long-chain branched modified polypropylene.

[0065] From the attached Figure 1 , 4It can be seen from the test data in , 7, 10 and 13 that the FT-IR images of the long-chain branched modified polypropylene in Examples 1-4 of the present invention show that different n-alkyl acrylates are grafted onto the polypropylene molecular chain, and the different characteristic peak sizes represent different grafting rates of different n-alkyl acrylates.

[0066] From the attached Figure 2 , 5 From the test data in , 8, 11 and 14, it can be seen that the XRD images of the long-chain branched modified polypropylene in Examples 1-4 show that the crystallization of the modified polypropylene by different processes is ideal.

[0067] From the attached Figure 3 , 6 From the test data in , 9, 12 and 15, it can be seen that the DMA images of the long-chain branched modified polypropylene in Examples 1-4 show that the mechanical properties of the long-chain branched modified polypropylene by different processes at 30-150°C are greatly improved, and high melt strength polypropylene with ideal performance is prepared.

Claims

1. A method for preparing long-chain branched modified polypropylene, characterized in that The preparation method is specifically carried out according to the following steps:

1. Add 1 part of polypropylene, 0.04 to 0.8 parts of n-alkyl acrylate monomer, 0.02 to 0.15 parts of interface agent, 0.1 to 0.4 parts of comonomer, 1 to 6 parts of deionized water, 0.001 to 0.006 parts of antioxidant and 0.001 to 0.008 parts of initiator into the reactor, and swell at a certain temperature for a certain time; The n-alkyl acrylate monomer described in step 1 is one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, behenyl acrylate, tetradecyl acrylate and tetratridecyl acrylate; 2. Raising the temperature of the reactor, and carrying out a grafting reaction at a certain temperature for a certain period of time to obtain a reaction product; 3. First, the reaction product is washed, then extracted with acetone, and finally dried to obtain long-chain branched modified polypropylene.

2. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that The interfacial agent described in step 1 is one or more of benzene, toluene and cyclohexane.

3. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that The comonomer described in step 1 is acrylic acid.

4. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that The antioxidant described in step 1 is one or more of tris[2,4-di-tert-butylphenyl]phosphite, 2,2'-methylenebis(4-methyl-6-tert-butylphenol) and bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite.

5. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that The initiator described in step 1 is one or more of azobisisobutyronitrile, dicyclopentadiene or ammonium persulfate.

6. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that In step 1, the swelling is carried out at 40°C to 80°C for 30min to 240min.

7. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that In step 2, the grafting is carried out at 75°C to 95°C for 30min to 480min.

8. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that The washing described in step 3 is washing with deionized water and anhydrous ethanol respectively 3 to 4 times.

9. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that The extraction time using acetone in step 3 is 2h to 24h.

10. The method for preparing a long-chain branched modified polypropylene according to claim 1, characterized in that The drying temperature in step 3 is 40°C to 75°C.

Images