Melt emulsification preparation method of high molecular weight polypropylene aqueous dispersion

Abstract

The invention discloses a melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion, and belongs to the field of aqueous polymer preparation. Comprising the following steps: (1) mixing maleic anhydride grafted polypropylene and citric acid in a mass ratio of 100: (5-20), adding p-toluenesulfonic acid which accounts for 0.5 wt% of the maleic anhydride grafted polypropylene, heating and melting under the protection of nitrogen, and carrying out condensation reaction at 160-170 DEG C to obtain citric acid modified polypropylene; and (2) adding citric acid modified polypropylene, low molecular weight oxidized polyethylene, a compound emulsifier and triethanolamine into a stirring kettle according to a mass ratio of 100: (5-25): (10-30): (2-6), mixing, heating to 160 DEG C, keeping for 1-5 hours, dripping hot water, and stirring, emulsifying and dispersing to obtain the high molecular weight polypropylene aqueous dispersion. According to the invention, the preparation of the high molecular weight functionalized polypropylene aqueous dispersion is realized, and the obtained dispersion has good stability.

Description

Technical Field

[0001] The invention relates to a method for preparing a polypropylene aqueous dispersion, in particular to a method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification, and belongs to the field of aqueous polymer preparation. Background Art

[0002] As one of the most promising thermoplastic polymer materials today, polypropylene has been widely used in packaging, automotive parts, home appliances, daily utensils and other fields. However, the non-polar characteristics of polypropylene limit its use with some polar materials. The functionalized high molecular weight polypropylene aqueous dispersion with polar groups has been grafted with polar groups due to functional modification. At the same time, based on the aqueous dispersion, it solves the problem of high molecular weight polypropylene's high melt viscosity and difficulty in direct industrial application, thus expanding its application field.

[0003] High molecular weight functionalized polypropylene (relative molecular weight ≥ 10000) is difficult to emulsify due to its high molecular weight resulting in high melt viscosity, high hydrophobicity and relatively low polarity. Therefore, the emulsification conditions are more stringent than those of low molecular weight polypropylene. From the literature and patent reports, there are mainly two methods: solution emulsification method and melt emulsification method.

[0004] Solution emulsification is a method of dissolving polypropylene in an organic solvent to form a solution and then emulsifying it. This method of dissolving high molecular weight polypropylene in an organic solvent, extracting it after emulsification and then removing the solvent is not an ideal method. Not only is the equipment and process complicated and costly, but it is also not conducive to safety and environmental protection. The melt emulsification method is to melt the polypropylene at a temperature above the melting point or under high pressure and then emulsify the melt. When melt emulsification is used to prepare polypropylene aqueous dispersions for high molecular weight polypropylene, it is necessary to use high pressure / high temperature melting, or change the emulsifier, the order of material melting and mixing, or add some low molecular weight polypropylene to reduce the melt viscosity and improve the emulsification effect.

[0005] Patent documents with publication numbers of US20060069187A1, WO2004031246A1, and WO2006039462A2 all involve a one-step method for preparing a functionalized polypropylene emulsion, which is to heat the functionalized polypropylene, an acid, a base, an emulsifier, and water to a temperature above the melting point of the polypropylene under stirring, and maintain the temperature for a sufficiently long time. However, such a one-step melt emulsification method is only applicable to the preparation of a functionalized polypropylene aqueous dispersion with a relatively low molecular weight.

[0006] The high molecular weight functionalized polypropylene available domestically has a relatively high molecular weight and a low maleic anhydride grafting rate, so it has a high melt viscosity and a low degree of functionalization, making it difficult to emulsify.

[0007] Based on the above problems, a melt emulsification preparation method of high molecular weight polypropylene aqueous dispersion is proposed. Summary of the invention

[0008] The purpose of the present invention is to provide a melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion. The preparation method introduces multiple carboxyl groups into the polypropylene molecular chain to further improve its functionalization degree, adds low molecular weight oxidized polyethylene to reduce its melt viscosity, adopts a melt emulsification method and combines emulsifier compounding by regulating and controlling dispersion process conditions to achieve the preparation of a high molecular weight functionalized polypropylene aqueous dispersion.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows: A method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification, comprising the following steps: (1) maleic anhydride grafted polypropylene and citric acid are mixed in a mass ratio of 100:(5-20), 0.5 wt% of p-toluenesulfonic acid relative to the maleic anhydride grafted polypropylene is added, the mixture is heated to melt under nitrogen protection, and a condensation reaction is carried out at a temperature of 160°C-170°C for 1-5 h to obtain citric acid modified polypropylene; (2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene, composite emulsifier and triethanolamine in a mass ratio of 100:(5-25):(10-30):(2-6) into a stirring kettle and mix, heat to 160°C and maintain for 1-5 hours, add 95-100°C hot water dropwise, stir and emulsify to obtain a high molecular weight polypropylene aqueous dispersion.

[0010] Preferably, the composite emulsifier is compounded from anionic emulsifier, nonionic emulsifier and polymer emulsifier.

[0011] Preferably, the composite emulsifier is compounded by anionic emulsifier, nonionic emulsifier and polymer emulsifier in a mass ratio of (3-5): (5-3): 2.

[0012] Preferably, the low molecular weight oxidized polyethylene is any one of EP629, EP316, OPE-1, and OPE-2.

[0013] Preferably, the anionic emulsifier is any one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium stearate and sodium oleate.

[0014] Preferably, the nonionic emulsifier is any one of the fatty alcohol polyoxyethylene ether AEO series and the isomeric alcohol ether E-1300 series.

[0015] Preferably, the polymer emulsifier is any one of EO-PO copolymer, polyoxyethylene glycol, and ethylene glycol ethyl acetate.

[0016] Preferably, the stirring rate in the melt emulsification process step is 5000 rpm to 15000 rpm.

[0017] Preferably, the emulsification time in the melt emulsification process step is 2h~4h.

[0018] Compared with the prior art, the advantages of the present invention are: 1. The present invention uses the hydroxyl group of citric acid to carry out condensation reaction with maleic anhydride grafted on the surface of polypropylene, so as to introduce more carboxyl groups on the molecular chain of polypropylene, so as to further improve its functionalization degree and polarity, thereby improving the emulsification and dispersion characteristics; 2. The present invention achieves the purpose of reducing melt viscosity by adding low molecular weight oxidized polyethylene. The main structure of low molecular weight oxidized polyethylene is polyethylene, and part of the ethyl group is oxidized. Since it is similar to polypropylene in structure, has good compatibility and is easy to emulsify, adding a proper amount can reduce the melt viscosity without significantly affecting the application performance of the polypropylene dispersion, and solve the problem of emulsification and dispersion; 3. The present invention further improves the emulsification and dispersion performance of polypropylene by compounding a polymer emulsifier with traditional small molecule anionic and non-ionic emulsifiers and utilizing the compatibility of the polymer emulsifier with the polypropylene matrix. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further illustrated by the following examples.

[0020] Example 1 1) 10 g of maleic anhydride grafted polypropylene was mixed with 0.96 g of citric acid, and 0.05 g of p-toluenesulfonic acid was added. The mixture was heated to melt under nitrogen protection, and condensed at 160 ° C for 3 h to obtain citric acid modified polypropylene.

[0021] 2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene (EP629, Qingdao East International Trade Co., Ltd.), anionic emulsifier (sodium dodecyl sulfate), nonionic emulsifier (isomeric alcohol polyoxyethylene ether E-1309), polymer emulsifier (EO-PO block copolymer, BASF) and triethanolamine into a stirring tank for mixing, wherein the mass ratio of citric acid modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: nonionic emulsifier: polymer emulsifier: triethanolamine is 100:25:4:4:2:3, heat to 160°C and keep for 2h, then add 95-100°C hot water dropwise under stirring for emulsification and dispersion, keep for 2h, and the stirring rate is 5000rpm to finally obtain a high molecular weight polypropylene aqueous dispersion.

[0022] Example 2 1) Mix 10g of maleic anhydride grafted polypropylene with 1.92g of citric acid, add 0.05g of p-toluenesulfonic acid, heat and melt under nitrogen protection, and condense at about 170°C for 1h to obtain citric acid modified polypropylene.

[0023] 2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene (EP316, Qingdao East International Trade Co., Ltd.), anionic emulsifier (sodium dodecylbenzene sulfonate), nonionic emulsifier (fatty alcohol polyoxyethylene ether AEO-9), polymer emulsifier (polyoxyethylene glycol) and triethanolamine into a stirring tank for mixing, wherein the mass ratio of citric acid modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: nonionic emulsifier: polymer emulsifier: triethanolamine is 100:5:10:6:4:6, heat to 160°C and keep for 2h, then add 95-100°C hot water dropwise under stirring for emulsification and dispersion, keep for 3h, and the stirring rate is 10000rpm to finally obtain a high molecular weight polypropylene aqueous dispersion.

[0024] Example 3 1) 10 g of maleic anhydride grafted polypropylene was mixed with 1.44 g of citric acid, and 0.05 g of p-toluenesulfonic acid was added. The mixture was heated to melt under nitrogen protection, and condensed at about 165°C for 2 h to obtain citric acid modified polypropylene.

[0025] 2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene (OPE-1, Jiangxi Fumei Technology Development Co., Ltd.), anionic emulsifier (sodium stearate), nonionic emulsifier (fatty alcohol polyoxyethylene ether AEO-7), polymer emulsifier (ethylene glycol ethyl acetate) and triethanolamine into a stirring tank for mixing, wherein the mass ratio of citric acid modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: nonionic emulsifier: polymer emulsifier: triethanolamine is 100:10:9:15:6:5, heat to 160°C and maintain for 2h, then add 95-100°C hot water dropwise under stirring for emulsification and dispersion, maintain for 4h, and the stirring rate is 15000rpm to finally obtain a high molecular weight polypropylene aqueous dispersion.

[0026] Example 4 1) 10 g of maleic anhydride grafted polypropylene was mixed with 1.92 g of citric acid, and 0.05 g of p-toluenesulfonic acid was added. The mixture was heated to melt under nitrogen protection, and condensed at about 160°C for 3 h to obtain citric acid modified polypropylene.

[0027] 2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene (OPE-2, Jiangxi Fumei Technology Development Co., Ltd.), anionic emulsifier (sodium oleate), nonionic emulsifier (isomeric alcohol ether E-1306), polymer emulsifier (EO-PO block copolymer, BASF) and triethanolamine into a stirred tank for mixing, wherein the mass ratio of citric acid modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: nonionic emulsifier: polymer emulsifier: triethanolamine is 100:5:10:6:4:3, heat to 160°C and keep for 2h, then add 95-100°C hot water dropwise under stirring for emulsification and dispersion, keep for 2h, and the stirring rate is 15000rpm to finally obtain a high molecular weight polypropylene aqueous dispersion.

[0028] Example 5 1) 10g of maleic anhydride grafted polypropylene was mixed with 0.96g of citric acid, and 0.05g of p-toluenesulfonic acid was added. The mixture was heated to melt under nitrogen protection, and condensed at about 160°C for 4h to obtain citric acid modified polypropylene.

[0029] 2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene (OPE-1, Jiangxi Fumei Technology Development Co., Ltd.), anionic emulsifier (sodium dodecyl sulfate), nonionic emulsifier (fatty alcohol polyoxyethylene ether AEO-5), polymer emulsifier (EO-PO block copolymer, BASF) and triethanolamine into a stirring tank for mixing, wherein the mass ratio of citric acid modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: nonionic emulsifier: polymer emulsifier: triethanolamine is 100:15:8:8:2:4, heat to 160°C and maintain for 2h, then add 95-100°C hot water dropwise under stirring for emulsification and dispersion, maintain for 3h, and the stirring rate is 10000rpm to finally obtain a high molecular weight polypropylene aqueous dispersion.

[0030] Example 6 1) Mix 10g of maleic anhydride grafted polypropylene with 1.44g of citric acid, add 0.05g of p-toluenesulfonic acid, heat and melt under nitrogen protection, and condense at about 160°C for 5h to obtain citric acid modified polypropylene.

[0031] 2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene (OPE-2, Jiangxi Fumei Technology Development Co., Ltd.), anionic emulsifier (sodium dodecyl sulfate), nonionic emulsifier (isomeric alcohol ether E-1303), polymer emulsifier (EO-PO block copolymer, BASF) and triethanolamine into a stirring tank for mixing, wherein the mass ratio of citric acid modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: nonionic emulsifier: polymer emulsifier: triethanolamine is 100:10:4:4:2:2, heat to 160°C and maintain for 2h, then add 95-100°C hot water dropwise under stirring for emulsification and dispersion, maintain for 4h, and stir at a rate of 5000rpm to finally obtain a high molecular weight polypropylene aqueous dispersion.

[0032] The particle size, centrifugal stability and thermal storage stability of the high molecular weight polypropylene aqueous dispersion finally obtained in Examples 1-6 were tested for performance indicators. The data results are shown in Table 1.

[0033] Table 1 Performance index test results of relevant products of Examples 1-6 It can be seen from the data in Table 1 that the polypropylene aqueous dispersion of the present invention has good stability and a particle size in the range of 5-30 μm.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification, It is characterized in that Here are the steps: (1) maleic anhydride grafted polypropylene and citric acid are mixed in a mass ratio of 100:(5-20), 0.5 wt% of p-toluenesulfonic acid relative to the maleic anhydride grafted polypropylene is added, the mixture is heated to melt under nitrogen protection, and a condensation reaction is carried out at a temperature of 160°C-170°C for 1-5 h to obtain citric acid modified polypropylene; (2) Add citric acid modified polypropylene, low molecular weight oxidized polyethylene, composite emulsifier and triethanolamine in a mass ratio of 100:(5-25):(10-30):(2-6) into a stirring kettle and mix, heat to 160°C and maintain for 1-5 hours, add 95-100°C hot water dropwise, stir and emulsify to obtain a high molecular weight polypropylene aqueous dispersion.

2. The method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification according to claim 1, It is characterized in that The composite emulsifier is prepared by compounding an anionic emulsifier, a nonionic emulsifier and a polymer emulsifier.

3. The melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 2, It is characterized in that The composite emulsifier is prepared by compounding an anionic emulsifier, a nonionic emulsifier and a polymer emulsifier in a mass ratio of (3-5):(5-3):

2.

4. The melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 1, It is characterized in that The low molecular weight oxidized polyethylene is any one of EP629, EP316, OPE-1 and OPE-2.

5. The melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 3, It is characterized in that The anionic emulsifier is any one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium stearate and sodium oleate.

6. The melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 3, It is characterized in that The nonionic emulsifier is any one of the fatty alcohol polyoxyethylene ether AEO series and the isomeric alcohol ether E-1300 series.

7. The melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 3, It is characterized in that The polymer emulsifier is any one of EO-PO copolymer, polyoxyethylene glycol and ethylene glycol ethyl acetate.

8. The melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 1, It is characterized in that The stirring rate in the melt emulsification process step is 5000rpm~15000rpm.

9. The method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification according to claim 1, It is characterized in that The emulsification time in the melt emulsification process step is 2h~4h.

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