A method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification

Abstract

The invention discloses a method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification, belonging to the field of preparation of aqueous polymers. The method includes: (1) mixing maleic anhydride grafted polypropylene and citric acid in a mass ratio of 100: (5-20), adding p-toluenesulfonic acid accounting for 0.5 wt% of the maleic anhydride grafted polypropylene, heating and melting under nitrogen protection, and carrying out a condensation reaction at 160°C - 170°C to obtain citric acid modified polypropylene; (2) adding the citric acid modified polypropylene, low molecular weight oxidized polyethylene, a composite emulsifier and triethanolamine into a stirring kettle in a mass ratio of 100: (5-25): (10-30): (2-6), heating to 160°C and maintaining for 1-5 h, dropping hot water, and stirring and emulsifying and dispersing to obtain a high molecular weight polypropylene aqueous dispersion. The invention realizes the preparation of a high molecular weight functionalized polypropylene aqueous dispersion, and the obtained dispersion has good stability.

Description

Technical Field

[0001] The present invention relates to a preparation method of an aqueous dispersion of polypropylene, and in particular to a melt emulsification preparation method of a high molecular weight polypropylene aqueous dispersion, belonging to the field of preparation of aqueous polymers. Background Art

[0002] As one of the most promising thermoplastic polymer materials today, polypropylene has been widely used in fields such as packaging, automotive parts, household appliances, and daily utensils. However, the non-polar characteristics of polypropylene limit its use in combination with some polar materials. The functionalized high molecular weight polypropylene aqueous dispersion with polar groups introduced, due to the grafting of polar groups by functionalization modification, and at the same time, based on the aqueous dispersion, solves the problems of high melt viscosity of high molecular weight polypropylene and difficult industrial direct application, and expands its application fields.

[0003] High molecular weight functionalized polypropylene (relative molecular weight ≥ 10,000) 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 the following two methods: solution emulsification method and melt emulsification method.

[0004] The solution emulsification method 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 and removing the solvent after emulsification is not an ideal method. It not only has complex equipment and processes, high costs, but also is not conducive to safety and environmental protection. The melt emulsification method is to melt polypropylene at a temperature above the melting point or under high pressure and then emulsify the melt. When using melt emulsification to prepare an aqueous dispersion of polypropylene with high molecular weight polypropylene, it is necessary to adopt high pressure / high temperature melting, or change the emulsifier, and the order of melting and mixing of the materials, or add some low molecular weight polypropylene to reduce the melt viscosity and improve the emulsification effect.

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

[0006] The high molecular weight functionalized polypropylene that can be purchased domestically has a relatively high molecular weight and a low maleic anhydride grafting rate. Therefore, it has a high melt viscosity and a low degree of functionalization and is difficult to emulsify.

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

[0008] The object of the present invention is to provide a method for preparing a waterborne dispersion of high molecular weight polypropylene by melt emulsification. This preparation method further improves its functionalization degree by introducing polycarboxyl groups into the polypropylene molecular chain, adds low molecular weight oxidized polyethylene to reduce its melt viscosity, and adopts the melt emulsification method and combines the emulsifier compounding by regulating the dispersion process conditions to realize the preparation of the waterborne dispersion of high molecular weight functionalized polypropylene.

[0009] To achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a waterborne dispersion of high molecular weight polypropylene by melt emulsification, the steps are as follows:

[0011] (1) Graft polypropylene maleic anhydride and citric acid in a mass ratio of 100:(5 - 20), add p-toluenesulfonic acid at 0.5 wt% relative to the graft polypropylene maleic anhydride, heat to melt under nitrogen protection, and carry out a condensation reaction at a temperature of 160°C - 170°C for 1 - 5 h to obtain citric acid modified polypropylene;

[0012] (2) Add the citric acid modified polypropylene, low molecular weight oxidized polyethylene, composite emulsifier and triethanolamine to a stirring kettle in a mass ratio of 100:(5 - 25):(10 - 30):(2 - 6), heat up to 160°C and keep it for 1 - 5 h, dropwise add hot water at 95 - 100°C, and stir for emulsification and dispersion to obtain a waterborne dispersion of high molecular weight polypropylene.

[0013] Preferably, the composite emulsifier is compounded from an anionic emulsifier, a nonionic emulsifier and a polymeric emulsifier.

[0014] Preferably, the composite emulsifier is compounded from an anionic emulsifier, a nonionic emulsifier and a polymeric emulsifier in a mass ratio of (3 - 5):(5 - 3):2.

[0015] Preferably, the low molecular weight oxidized polyethylene used is any one of EP629, EP316, OPE-1, OPE-2.

[0016] Preferably, the anionic emulsifier used is any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium stearate, sodium oleate.

[0017] Preferably, the nonionic emulsifier used is any one of the fatty alcohol polyoxyethylene ether AEO series and the isomeric alcohol ether E-1300 series.

[0018] Preferably, the polymer emulsifier is any one of EO-PO copolymers, polyethylene glycol, and ethylene glycol acetate.

[0019] Preferably, the stirring rate in the melt emulsification process step is 5000 rpm to 15000 rpm.

[0020] Preferably, the emulsification time in the melt emulsification process step is 2 h to 4 h.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] 1. The present invention uses the hydroxyl group of citric acid to carry out a condensation reaction with maleic anhydride grafted on the surface of polypropylene, so as to introduce more carboxyl groups on the polypropylene molecular chain, further improving its functionalization degree and polarity, and thus improving the emulsification and dispersion characteristics;

[0023] 2. The present invention adds low molecular weight oxidized polyethylene to achieve the purpose of reducing the melt viscosity. The main structure of low molecular weight oxidized polyethylene is polyethylene, and some ethyl groups are oxidized. Since it has good compatibility with the polypropylene structure and is easy to emulsify, appropriate addition can reduce the melt viscosity without significantly affecting the application performance of the polypropylene dispersion, and solve the problem of emulsification and dispersion;

[0024] 3. The present invention uses a polymer emulsifier to compound with traditional small molecule anionic and non-ionic emulsifiers, and utilizes the compatibility of the polymer emulsifier with the polypropylene matrix to further improve the emulsification and dispersion performance of polypropylene. Specific Embodiments

[0025] The technical solutions of the present invention will be further described below through examples.

[0026] Example 1

[0027] 1) 10 g of maleic anhydride grafted polypropylene and 0.96 g of citric acid were mixed and 0.05 g of p-toluenesulfonic acid was added. It was heated to melt under nitrogen protection and subjected to a condensation reaction at 160 °C for 3 h to obtain citric acid modified polypropylene.

[0028] 2) Mix citric acid-modified polypropylene, low molecular weight oxidized polyethylene (EP629, Qingdao East International Trade Co., Ltd.), anionic emulsifier (sodium dodecyl sulfate), non-ionic emulsifier (isomeric alcohol polyoxyethylene ether E-1309), high molecular weight emulsifier (EO-PO block copolymer, BASF), and triethanolamine in a stirring kettle. The mass ratio of citric acid-modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: non-ionic emulsifier: high molecular weight emulsifier: triethanolamine is 100:25:4:4:2:3. Heat up to 160 °C and keep for 2 h, then dropwise add hot water at 95 - 100 °C under stirring for emulsification and dispersion, keep for 2 h, and the stirring rate is 5000 rpm. Finally, a high molecular weight polypropylene aqueous dispersion is obtained.

[0029] Example 2

[0030] 1) Mix 10 g of maleic anhydride grafted polypropylene with 1.92 g of citric acid and add 0.05 g of p-toluenesulfonic acid. Heat up to melt under nitrogen protection and carry out a condensation reaction at about 170 °C for 1 h to obtain citric acid-modified polypropylene.

[0031] 2) Mix citric acid-modified polypropylene, low molecular weight oxidized polyethylene (EP316, Qingdao East International Trade Co., Ltd.), anionic emulsifier (sodium dodecylbenzenesulfonate), non-ionic emulsifier (aliphatic alcohol polyoxyethylene ether AEO-9), high molecular weight emulsifier (polyethylene glycol), and triethanolamine in a stirring kettle. The mass ratio of citric acid-modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: non-ionic emulsifier: high molecular weight emulsifier: triethanolamine is 100:5:10:6:4:6. Heat up to 160 °C and keep for 2 h, then dropwise add hot water at 95 - 100 °C under stirring for emulsification and dispersion, keep for 3 h, and the stirring rate is 10000 rpm. Finally, a high molecular weight polypropylene aqueous dispersion is obtained.

[0032] Example 3

[0033] 1) Mix 10 g of maleic anhydride grafted polypropylene with 1.44 g of citric acid and add 0.05 g of p-toluenesulfonic acid. Heat up to melt under nitrogen protection and carry out a condensation reaction at about 165 °C for 2 h to obtain citric acid-modified polypropylene.

[0034] 2) Add citric acid-modified polypropylene, low molecular weight oxidized polyethylene (OPE-1, Jiangxi Fumei Science and Technology Development Co., Ltd.), anionic emulsifier (sodium stearate), non-ionic emulsifier (alcohol polyoxyethylene ether AEO-7), high molecular weight emulsifier (ethylene glycol acetate), and triethanolamine into a stirring kettle for mixing. The mass ratio of citric acid-modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: non-ionic emulsifier: high molecular weight emulsifier: triethanolamine is 100:10:9:15:6:5. Heat up to 160 °C and keep for 2 h, then dropwise add hot water at 95 - 100 °C under stirring for emulsification and dispersion, keep for 4 h, and the stirring rate is 15,000 rpm. Finally, a high molecular weight polypropylene aqueous dispersion is obtained.

[0035] Example 4

[0036] 1) Mix 10 g of maleic anhydride grafted polypropylene with 1.92 g of citric acid and add 0.05 g of p-toluenesulfonic acid. Heat up to melt under nitrogen protection and carry out a condensation reaction at about 160 °C for 3 h to obtain citric acid-modified polypropylene.

[0037] 2) Add citric acid-modified polypropylene, low molecular weight oxidized polyethylene (OPE-2, Jiangxi Fumei Science and Technology Development Co., Ltd.), anionic emulsifier (sodium oleate), non-ionic emulsifier (isomeric alcohol ether E-1306), high molecular weight emulsifier (EO-PO block copolymer, BASF), and triethanolamine into a stirring kettle for mixing. The mass ratio of citric acid-modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: non-ionic emulsifier: high molecular weight emulsifier: triethanolamine is 100:5:10:6:4:3. Heat up to 160 °C and keep for 2 h, then dropwise add hot water at 95 - 100 °C under stirring for emulsification and dispersion, keep for 2 h, and the stirring rate is 15,000 rpm. Finally, a high molecular weight polypropylene aqueous dispersion is obtained.

[0038] Example 5

[0039] 1) Mix 10 g of maleic anhydride grafted polypropylene with 0.96 g of citric acid and add 0.05 g of p-toluenesulfonic acid. Heat up to melt under nitrogen protection and carry out a condensation reaction at about 160 °C for 4 h to obtain citric acid-modified polypropylene.

[0040] 2) Mix citric acid-modified polypropylene, low molecular weight oxidized polyethylene (OPE-1, Jiangxi Fumei Science and Technology Development Co., Ltd.), anionic emulsifier (sodium dodecyl sulfate), non-ionic emulsifier (aliphatic alcohol polyoxyethylene ether AEO-5), high molecular weight emulsifier (EO-PO block copolymer, BASF), and triethanolamine in a stirring kettle. The mass ratio of citric acid-modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: non-ionic emulsifier: high molecular weight emulsifier: triethanolamine is 100:15:8:8:2:4. Heat up to 160 °C and keep for 2 h, then dropwise add hot water at 95 - 100 °C under stirring for emulsification and dispersion, keep for 3 h, and the stirring rate is 10,000 rpm. Finally, a high molecular weight polypropylene aqueous dispersion is obtained.

[0041] Example 6

[0042] 1) Mix 10 g of maleic anhydride grafted polypropylene with 1.44 g of citric acid and add 0.05 g of p-toluenesulfonic acid. Heat up to melt under nitrogen protection and carry out a condensation reaction at about 160 °C for 5 h to obtain citric acid-modified polypropylene.

[0043] 2) Mix citric acid-modified polypropylene, low molecular weight oxidized polyethylene (OPE-2, Jiangxi Fumei Science and Technology Development Co., Ltd.), anionic emulsifier (sodium dodecyl sulfate), non-ionic emulsifier (isomeric alcohol ether E-1303), high molecular weight emulsifier (EO-PO block copolymer, BASF), and triethanolamine in a stirring kettle. The mass ratio of citric acid-modified polypropylene: low molecular weight oxidized polyethylene: anionic emulsifier: non-ionic emulsifier: high molecular weight emulsifier: triethanolamine is 100:10:4:4:2:2. Heat up to 160 °C and keep for 2 h, then dropwise add hot water at 95 - 100 °C under stirring for emulsification and dispersion, keep for 4 h, and the stirring rate is 5,000 rpm. Finally, a high molecular weight polypropylene aqueous dispersion is obtained.

[0044] The performance index tests of the particle size, centrifugal stability, and thermal storage stability of the high molecular weight polypropylene aqueous dispersions finally prepared in Examples 1 - 6 are carried out as follows. The data results are shown in Table 1.

[0045] Table 1 Test results of performance indexes of related products in Examples 1 - 6

[0046]

[0047] It can be seen from the data in Table 1 that the polypropylene aqueous dispersion of the present invention has good stability, and the particle size is in the range of 5 - 30 μm.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and such modifications or equivalent replacements do not cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a waterborne dispersion of high molecular weight polypropylene by melt emulsification, characterized in that, The steps are as follows: (1) Mix maleic anhydride grafted polypropylene and citric acid in a mass ratio of 100:(5 - 20), add p-toluenesulfonic acid at 0.5 wt% relative to maleic anhydride grafted polypropylene, heat to melt under nitrogen protection, and carry out a condensation reaction 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 to a stirring kettle in a mass ratio of 100:(5 - 25):(10 - 30):(2 - 6), heat to 160°C and keep for 1 - 5 h, dropwise add hot water at 95 - 100°C, and stir for emulsifying dispersion to obtain a high molecular weight polypropylene aqueous dispersion; The composite emulsifier is compounded from an anionic emulsifier, a non-ionic emulsifier, and a polymer emulsifier in a mass ratio of (3 - 5):(5 - 3):2; among them, the anionic emulsifier is any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium stearate, and sodium oleate; the non-ionic emulsifier is any one of the fatty alcohol polyoxyethylene ether AEO series and the isomeric alcohol ether E-1300 series; the polymer emulsifier is any one of EO-PO copolymers and polyethylene glycol.

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

3. A method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification according to claim 1, characterized in that In step (2), the stirring rate is 5000 rpm to 15000 rpm.

4. A method for preparing a high molecular weight polypropylene aqueous dispersion by melt emulsification according to claim 1, characterized in that In step (2), the emulsification time is 2 h to 4 h.

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