A method for preparing modified alkylaluminoxane and its application in the preparation of polyolefin elastomer

Abstract

The present invention discloses a method for preparing a modified alkyl aluminoxane: the specific steps are as follows: (1) treating a molecular sieve with an acid solution, adding the obtained acid-treated molecular sieve and a surfactant to an ammonium salt solution for continued reaction to obtain a modified molecular sieve, and then activating the obtained modified molecular sieve to obtain an activated modified molecular sieve; (2) uniformly mixing an ionic liquid with an alkyl aluminum to form a stable alkyl aluminum solution; (3) adding the activated modified molecular sieve to the alkyl aluminum solution, and then slowly adding a modifier to react, centrifuging the obtained reaction solution to remove insoluble matter, and then extracting it with toluene, and then performing reduced pressure distillation on the extract to collect the obtained residue. The preparation method of the modified alkyl aluminoxane provided by the present invention has the advantages of mild reaction conditions and simple operation. The modified alkyl aluminoxane provided by the present invention can be successfully used to catalyze the reaction of ethylene / 1-octene polyolefin elastomers.

Description

Technical Field

[0001] The invention belongs to the technical field of metal organic compounds, and in particular relates to a preparation method of a modified alkyl aluminoxane and application of the modified alkyl aluminoxane in the preparation of a polyolefin elastomer. Background Art

[0002] Modified alkyl aluminoxane is a commonly used metal additive for the preparation of polyolefin elastomers (POE) using metallocene catalysts. In the preparation reaction of polyolefin elastomers, one of the commonly used catalytic systems is composed of metallocene catalysts and modified alkyl aluminoxanes; among them, the main functions of modified alkyl aluminoxane as a co-catalyst are as follows: first, modified alkyl aluminoxane can enhance the activity of the main catalyst metallocene and increase the rate of polymerization reaction; second, modified alkyl aluminoxane can adjust the molecular weight of POE polymer through interaction with metallocene catalysts, affecting the viscosity and rheological properties of polymers; third, modified alkyl aluminoxane can affect the branching degree and intermolecular interaction of polymers, thereby affecting the processing properties of polyolefin elastomers and the performance of the final product. It can be seen that modified alkyl aluminoxane and metallocene catalysts achieve precise control of polymerization reactions and polymer properties through interaction and influence in the preparation of polyolefin elastomers; the selection and optimization of this catalyst system is crucial for the production and preparation of polyolefin elastomers that meet specific application requirements. (Zhao Yan, Xu Dianhong, Li Nan, Wang Zaihua, Chen Hong. Research and application progress of polyolefin elastomer technology [J]. Synthetic Rubber Industry, 2020, 43(6): 514-520.).

[0003] POE (polyolefin elastomer) is usually obtained by random copolymerization of ethylene and high carbon α-olefins (such as 1-butene, 1-hexene, 1-octene, etc.). This unique molecular structure leads to the formation of a microscopic phase in which crystalline and non-crystalline regions are intertwined inside the material. The crystalline region provides the material with the necessary hardness, while the non-crystalline region gives the material flexibility. Thanks to these characteristics, POE has been widely used in many fields such as solar photovoltaic, automobile manufacturing, construction industry and cable manufacturing (Li Bogeng, Zhang Mingxuan, Liu Weifeng, Wang Wenjun. Polyolefin elastomers - Current status and progress [J]. Chemical Industry Progress, 2017, 36 (9): 3135-3144.). However, the commonly used metal additive modified alkyl aluminoxane for metallocene-catalyzed polyolefin elastomer preparation reaction has a series of disadvantages such as high price and complicated preparation method. In summary, modified alkyl aluminoxane plays a vital role in POE polymerization reaction. It is very necessary to explore and improve its preparation method to improve its synthesis efficiency and application performance to meet the needs of industrial production. Summary of the invention

[0004] In view of the shortcomings of the existing preparation methods of modified alkyl aluminoxane, the purpose of the present invention is to provide a preparation method of modified alkyl aluminoxane and its application in the preparation of polyolefin elastomers.

[0005] In order to achieve the above object, the solution of the present invention is:

[0006] A method for preparing a modified alkylaluminoxane comprises the following steps:

[0007] (1) treating a molecular sieve with an acid solution, adding the acid-treated molecular sieve and a surfactant to an ammonium salt solution to continue the reaction to obtain a modified molecular sieve, and then activating the modified molecular sieve to obtain an activated modified molecular sieve;

[0008] (2) uniformly mixing the ionic liquid and the alkyl aluminum to form a stable alkyl aluminum solution;

[0009] (3) adding the activated modified molecular sieve obtained in step (1) to the alkyl aluminum solution obtained in step (2), then slowly adding a modifier to react, centrifuging the obtained reaction solution to remove insoluble matter, and then extracting it with toluene, distilling the extract under reduced pressure, and collecting the obtained residue to obtain the modified alkyl aluminoxane.

[0010] Preferably, the molecular sieve described in step (1) is one of 13X molecular sieve, 5A molecular sieve, 3A molecular sieve or SBA-15.

[0011] Preferably, the acid solution in step (1) is a mixture of an organic acid solution and an inorganic acid solution.

[0012] Preferably, the surfactant described in step (1) is one of hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene (20) ether or hexadecyltrimethylammonium hydroxide.

[0013] Preferably, the ammonium salt solution in step (1) is one of ammonium chloride, ammonium nitrate, ammonium citrate, ammonium carbonate or ammonium bicarbonate.

[0014] Preferably, the ionic liquid described in step (2) is composed of one or two of 1-butyl-3-methylimidazolium chloroaluminate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate or tetrabutyl silicotungstate.

[0015] Preferably, the alkylaluminum described in step (2) is one of trimethylaluminum, triethylaluminum or triisopropylaluminum.

[0016] Preferably, the modifier described in step (3) is one of methanol, ethanol, isopropanol or isobutanol.

[0017] Application of the modified alkyl aluminoxane prepared by the above-mentioned preparation method of modified alkyl aluminoxane in the preparation of polyolefin elastomer.

[0018] The principle of the method provided by the present invention is as follows:

[0019] The main principle of the preparation method of the modified alkyl aluminoxane provided by the present invention is as follows: first, the molecular sieve is treated with a mixed acid solution composed of an organic acid and an inorganic acid; wherein the organic acid can effectively remove the free aluminum ions contained in the molecular sieve pores through a complex reaction and reinforce the hydroxyl vacancies in the molecular sieve to obtain a molecular sieve with a more stable structure; and the inorganic acid can help to improve the dealumination ability of the organic acid, and the dealumination effect of the organic acid alone is not good; then the molecular sieve is modified by using an ammonium salt to form a super-large mesopore to form a fast channel for the reaction and diffusion of alkyl aluminum molecules on the molecular sieve. Secondly, the preparation method of the modified alkyl aluminoxane provided by the present invention uses an ionic liquid as a reaction medium, fully utilizing the low volatility, high stability and adjustable chemical properties of the ionic liquid, successfully solving the problem of solvent volatility, effectively improving the controllability of the preparation process, and at the same time improving the purity and performance of the final product, which provides an effective way to optimize the preparation process of the modified alkyl aluminoxane.

[0020] Compared with the existing method, the gain effect of the present invention is as follows:

[0021] 1. The modified molecular sieve used in the method for preparing modified alkylaluminoxane provided by the present invention can undergo mild hydrolysis reaction with alkylaluminum solution in ionic liquid, thereby effectively improving the efficiency of preparing alkylaluminoxane by hydrolysis reaction of alkylaluminum.

[0022] 2. The ionic liquid used as the reaction solvent in the preparation method of the modified alkylaluminoxane provided by the present invention is not only convenient for separation and purification of the final product, but the ionic liquid itself can also be recycled and reused, thereby reducing the waste of solvent and meeting the requirements of green environmental protection.

[0023] 3. The preparation method of the modified alkylaluminoxane provided by the present invention also has the advantages of mild reaction conditions and simple operation.

[0024] 4. The modified alkyl aluminoxane obtained by the preparation method provided by the present invention can be successfully used to prepare metallocene catalysts. The catalyst system composed of the obtained metallocene catalyst as the main catalyst and the modified alkyl aluminoxane as the co-catalyst can be used to catalyze the reaction of ethylene / 1-octene polyolefin elastomer. The reaction results are: the polymerization activity of the catalyst is 2.11×10 3 (gCopolymer:gcat-1 h -1 ); Mw is 22.14×10 4 , Mn is 9.67×10 4 , PDI is 2.29; the density of the obtained polyolefin elastomer is 0.889 g / cm 3 ; The melting point Tm of the obtained polyolefin elastomer is 113°C. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the embodiments. It should also be understood that the following embodiments are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. The specific quality, reaction time and temperature, process parameters, etc. in the examples are only examples within the appropriate ranges. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present invention all belong to the scope of protection of the present invention.

[0026] All reagents used were commercial reagents unless otherwise specified and were not further purified before use.

[0027] Embodiment 1:

[0028] The preparation method of triisobutylaluminoxane specifically comprises the following steps:

[0029] (1) 10 g of 13X molecular sieve was added to 250 ml of deionized water and soaked for half an hour, then placed in a vacuum drying oven at 110° C. and dried for 6 hours. 5 g of the dried 13X molecular sieve was taken and immersed in a mixed acid solution consisting of 120 mL of 1 mol / L oxalic acid solution and 80 ml of 1 mol / L sulfuric acid solution. The obtained mixture was transferred to an ultrasonic reactor and subjected to ultrasonic oscillation reaction (80 kHz, 50 W) at 50° C. for 40 minutes, then filtered. The obtained solid was washed with 500 ml of deionized water (washed more than 5 times) and then placed in a vacuum drying oven at 110° C. and dried for 12 hours to obtain an acid-treated molecular sieve. The obtained acid-treated 13X molecular sieve was added to 2 50ml of 1mol / L ammonium bicarbonate solution, then add 0.4g of hexadecyltrimethylammonium bromide, heat the resulting mixture to 70°C and continue stirring for 1.5h before filtering, wash the resulting solid with 500ml of deionized water (wash more than 5 times) and then put it into a vacuum drying oven at 110°C for 10h, place the dried 13X molecular sieve in a muffle furnace and roast at 550°C for 1.5h to obtain a modified 13X molecular sieve; place the modified 13X molecular sieve in water vapor at 120°C for activation, the flow rate of the water vapor is 40mL / min, after activation for 30min, naturally dry the obtained molecular sieve to obtain the activated modified 13X molecular sieve;

[0030] (2) under the protection of nitrogen in an ice bath, 2.02 g of triisobutylaluminum was added to 67 g of 1-butyl-3-methylimidazolium chloroaluminate and mixed evenly to form a stable triisobutylaluminum solution;

[0031] (3) Under the protection of nitrogen in an ice bath, 0.8 g of the activated modified molecular sieve prepared in step (1) was added to the triisobutylaluminum solution prepared in step (2), and then 0.2 ml of isobutyl alcohol was slowly added using a microsyringe to react. The reaction was stirred for 1.5 h, and the obtained reaction solution was centrifuged to remove insoluble matter and then extracted with 150 ml of toluene (extracted more than 3 times). The extracts were combined and then vacuum distilled to collect the residue to obtain the isobutylaluminoxane, a total of 1.72 g.

[0032] Example 2

[0033] The preparation method of isobutylaluminoxane is the same as that of Example 1, except that the amount of oxalic acid solution in step (1) is adjusted to 200 ml, and the amount of sulfuric acid solution is adjusted to 0 ml; other conditions are the same, and finally 1.64 g of isobutylaluminoxane is obtained.

[0034] Example 3

[0035] The preparation method of isobutylaluminoxane is based on Example 1, except that the surfactant hexadecyltrimethylammonium bromide in step (1) is replaced with fatty alcohol polyoxyethylene (20) ether, and other conditions are the same, and finally 1.55 g of isobutylaluminoxane is obtained.

[0036] Example 4

[0037] The preparation method of isobutylaluminoxane is the same as that of Example 1, except that the surfactant hexadecyltrimethylammonium bromide in step (1) is replaced with hexadecyltrimethylammonium hydroxide, and other conditions are the same, and finally 1.76 g of isobutylaluminoxane is obtained.

[0038] Example 5

[0039] Preparation method of isobutylaluminoxane The preparation method is similar to that of Example 1, except that the 13X molecular sieve in step (1) is replaced with SBA-15, and other conditions are the same, and finally 1.53 g of isobutylaluminoxane is obtained.

[0040] Example 6

[0041] The preparation method of isobutylaluminoxane is the same as that of Example 1, except that the 1-butyl-3-methylimidazolium chloroaluminate in step (2) is replaced with 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the amount of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is 72 g; other conditions are the same, and 1.70 g of ethylaluminoxane is finally obtained.

[0042] Example 7

[0043] The preparation method of isobutylaluminoxane is based on Example 1, except that the 1-butyl-3-methylimidazolium chloroaluminate in step (2) is replaced by a mixed ionic liquid consisting of 40.2 g of 1-butyl-3-methylimidazolium chloroaluminate and 28.8 g of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; other conditions are the same, and 1.87 g of isobutylaluminoxane is finally obtained.

[0044] Example 8

[0045] The preparation method of ethylaluminoxane is as described in Example 1, except that the triisobutylaluminum in step (2) is replaced by triethylaluminum, the amount of triethylaluminum used is 1.14 g, and other conditions are the same, and finally 0.86 g of ethylaluminoxane is obtained.

[0046] Example 9

[0047] The steps for preparing ethylene / 1-octene polyolefin elastomer are as follows:

[0048] (1) Preparation of metallocene catalyst: All operations were performed under nitrogen protection. 15 g of silica gel carrier was placed in an oven at 110° C. for drying for 8 hours and then added to a reaction flask. Then, 1.4 g of isobutylaluminoxane, 0.16 g of pentafluorophenylzinc, 0.06 g of 1-(phenylbenzyl)azetidinol and 160 ml of toluene were added to the reaction flask. The reaction flask was transferred to an ultrasonic reactor and ultrasonically oscillated at 40° C. for 30 min. After filtering, the obtained solid was washed three times with 50 ml of toluene to obtain a silica gel carrier loaded with isobutylaluminoxane and 1-(phenylbenzyl)azetidinol. The obtained isobutylaluminoxane and 1-(phenylbenzyl)azetidinol loaded silica gel carrier and 0.30 g of metallocene complex Me were added. 2 SiC 2 ZrCl 2 Add to 80 ml of toluene, then move the reaction flask into an ultrasonic reactor and ultrasonically oscillate at 40°C for 30 min, filter and wash the obtained solid with 50 ml of toluene, repeat the washing at least 3 times, and vacuum dry the obtained solid to prepare the metallocene catalyst;

[0049] (2) Catalytic reaction of ethylene / 1-octene polyolefin elastomer:

[0050] All operations were carried out under nitrogen protection. The 1L stainless steel polymerization kettle was replaced with high-purity nitrogen for no less than three times, and then 70ml of n-hexane, 20ml of 1-octene, 0.71g isobutylaluminoxane and 0.02g of the metallocene catalyst prepared in step (1), after starting stirring, the temperature of the polymerization kettle is raised to 110°C, the pressure of ethylene injected into the polymerization kettle is 1.2MPa, the temperature and pressure of the reaction system are kept constant, the polymerization reaction is maintained for 2.5h and then cooled, the reaction solution is poured into 100ml of 10% acidified ethanol solution (hydrochloric acid / ethanol=1 / 10) to terminate the reaction, and the obtained polyolefin elastomer product is washed with 50ml of deionized water and 50ml of anhydrous ethanol in sequence after filtering, and finally placed in a vacuum drying oven at 80°C to dry to constant weight to obtain ethylene-1-octene polyolefin elastomer; the obtained ethylene-1-octene polyolefin elastomer is characterized, and the specific conditions are as follows: the weight average relative molecular mass (Mw), number average relative molecular mass (Mn) and relative molecular mass distribution (PDI=Mw / Mn) of the polyolefin elastomer are determined by high temperature gel permeation chromatography; DSC of the polyolefin elastomer is measured on a SHIMADZU The temperature was measured on DSC-50 at a rate of 20°C / min. The density of the polyolefin elastomer was measured using a density balance. The reaction results showed that the polymerization activity of the catalyst was 2.11×10 3 (gCopolymer:gcat -1 h -1 ); Mw is 22.14×10 4 , Mn is 9.67×10 4 , PDI is 2.29; the density of the obtained polyolefin elastomer is 0.889 g / cm 3 ; The melting point Tm of the obtained polyolefin elastomer is 113°C.

[0051] Comparative Example 1

[0052] The preparation steps of the preparation method of modified aluminoxane refer to embodiment 1, except that step (1) is changed to: add 10g of 13X molecular sieve to 250ml of deionized water, soak for half an hour, and then put it in a vacuum drying oven at 110°C for drying for 6h, take 5g of the dried 13X molecular sieve, place it in a muffle furnace and roast it at 550°C for 1.5h, and then put it into water vapor at 120°C for activation, the flow rate of water vapor is 40mL / min, after activation for 30min, the obtained molecular sieve is naturally dried to obtain the activated 13X molecular sieve;

[0053] Step (2) and step (3) are the same as in Example 1, and 1.36 g of isobutylaluminoxane is finally obtained.

[0054] Comparative Example 2

[0055] The preparation steps of the preparation method of modified aluminoxane refer to Example 1, step (1) is the same as Example 1;

[0056] Change step (2) to: under the protection of nitrogen in an ice bath, add 2.02 g of triisobutylaluminum to 50 ml of toluene and mix well to form a stable triisobutylaluminum solution;

[0057] Step (3) is changed to: under the protection of nitrogen in an ice bath, 0.8 g of the activated modified molecular sieve prepared in step (1) is added to the triisobutylaluminum solution prepared in step (2), and then 0.2 ml of isobutyl alcohol is slowly added using a microsyringe to react, and the reaction is stirred for 1.5 hours. The obtained reaction solution is filtered to remove insoluble matter, and the obtained filtrate is heated and distilled under reduced pressure to remove the solvent. The obtained residue is then dissolved in 150 ml of dry toluene and continued to be distilled under reduced pressure. Finally, the obtained residue is collected to obtain isobutylaluminoxane, a total of 1.59 g.

Claims

1. A method for preparing a modified alkylaluminoxane, characterized in that: The specific steps include: (1) treating a molecular sieve with an acid solution, adding the acid-treated molecular sieve and a surfactant to an ammonium salt solution to continue the reaction to obtain a modified molecular sieve, and then activating the modified molecular sieve to obtain an activated modified molecular sieve; (2) uniformly mixing the ionic liquid and the alkyl aluminum to form a stable alkyl aluminum solution; (3) adding the activated modified molecular sieve obtained in step (1) to the alkyl aluminum solution obtained in step (2), then slowly adding a modifier to react, centrifuging the obtained reaction solution to remove insoluble matter, and then extracting it with toluene, distilling the extract under reduced pressure, and collecting the obtained residue to obtain the modified alkyl aluminoxane.

2. The method for preparing modified alkylaluminoxane according to claim 1, characterized in that: The molecular sieve described in step (1) is one of 13X molecular sieve, 5A molecular sieve, 3A molecular sieve or SBA-15.

3. The method for preparing modified alkylaluminoxane according to claim 1, characterized in that: The acid solution described in step (1) is a mixture of an organic acid solution and an inorganic acid solution.

4. The method for preparing modified alkylaluminoxane according to claim 1, characterized in that: The surfactant described in step (1) is one of hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene (20) ether or hexadecyltrimethylammonium hydroxide.

5. The method for preparing modified alkylaluminoxane according to claim 1, characterized in that: The ammonium salt solution described in step (1) is one of ammonium chloride, ammonium nitrate, ammonium citrate, ammonium carbonate or ammonium bicarbonate.

6. The method for preparing modified alkylaluminoxane according to claim 1, characterized in that: The ionic liquid described in step (2) is composed of one or two of 1-butyl-3-methylimidazolium chloroaluminate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate or tetrabutyl silicotungstate.

7. The method for preparing modified alkylaluminoxane according to claim 1, characterized in that: The alkylaluminum described in step (2) is one of trimethylaluminum, triethylaluminum or triisopropylaluminum.

8. The method for preparing modified alkylaluminoxane according to claim 1, characterized in that: The modifier described in step (3) is one of methanol, ethanol, isopropanol or isobutanol.

9. Use of the modified alkylaluminoxane prepared by the method for preparing the modified alkylaluminoxane according to claims 1 to 8 in the preparation of polyolefin elastomer.