A solution emulsification preparation method of a high molecular weight polypropylene aqueous dispersion

Abstract

The present invention relates to a solution emulsification preparation method of a high molecular weight polypropylene aqueous dispersion, belonging to the field of aqueous polymer preparation. The method comprises the following steps: S1, dissolving a high molecular weight maleic anhydride grafted polypropylene resin in an organic solvent, adding citric acid and a catalyst for grafting reaction to obtain a citric acid modified polypropylene solution; S2, dissolving an emulsifier in deionized water to form an emulsifier aqueous solution; S3, under stirring conditions, slowly adding the citric acid modified polypropylene solution of S1 into the emulsifier aqueous solution of S2 to form a pre-emulsion; S4, transferring the pre-emulsion to a reaction kettle for emulsification, and removing the organic solvent by vacuum distillation to obtain a high molecular weight citric acid modified polypropylene aqueous dispersion. The present invention ensures good dispersibility and stability of the high molecular weight polypropylene aqueous dispersion through further graft modification of maleic anhydride grafted polypropylene and optimization of the dosage of the emulsifier.

Description

Technical Field

[0001] The present invention relates to the field of preparation of aqueous polymers, and particularly to a solution emulsification method for preparing a high molecular weight polypropylene aqueous dispersion. Background Art

[0002] Polypropylene is an important polymer material with excellent mechanical properties, chemical corrosion resistance and processing properties, and 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. By introducing a polar group-functionalized high molecular weight polypropylene aqueous dispersion, on the one hand, it can functionalize and modify high molecular weight polypropylene, graft polar groups such as maleic anhydride, endow polypropylene with certain polarity and reactivity, and enable polypropylene to have good compatibility and interfacial interaction with other polar substances; at the same time, the aqueous dispersion also solves the problem of high melt viscosity of high molecular weight polypropylene and difficult industrial direct application, and can expand its application fields.

[0003] Currently, the methods for preparing high molecular weight polypropylene aqueous dispersions mainly include melt emulsification and solution emulsification methods. High molecular weight functionalized polypropylene (relative molecular weight ≥ 10,000) has a high melt viscosity due to its high molecular weight, high hydrophobicity and relatively low polarity, making it difficult to be melt-emulsified. The solution emulsification method is a method of dissolving polypropylene in an organic solvent to form a solution and then emulsifying it. The main process is as follows: an organic solvent immiscible with water is used to dissolve polypropylene, and then an emulsifier and water are added to emulsify the high molecular weight functionalized polypropylene. Finally, the organic solvent is removed to obtain a high molecular weight functionalized polypropylene aqueous dispersion. The advantage of this method is that high molecular weight functionalized polypropylene has a relatively large solubility in conventional organic solvents, the solution viscosity is low, it is easy to emulsify and can be emulsified at a high concentration. Therefore, it is suitable for the emulsification and dispersion of polypropylene with a relatively high molecular weight and a relatively high degree of functionalization. Summary of the Invention

[0004] The object of the present invention is to provide a solution emulsification method for preparing a high molecular weight polypropylene aqueous dispersion with a relatively high molecular weight but a relatively low degree of functionalization. This method further reacts the hydroxyl group of citric acid with the anhydride group of maleic anhydride grafted polypropylene, thereby introducing more carboxyl groups into the polypropylene molecular chain to enhance the degree of functionalization of polypropylene, and then being able to efficiently prepare a high molecular weight polypropylene aqueous dispersion by the solution emulsification method, and having good dispersibility and stability at the same time.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A solution emulsification method for preparing a high molecular weight polypropylene aqueous dispersion, comprising the following steps:

[0007] S1. Dissolve the high molecular weight maleic anhydride grafted polypropylene resin in an organic solvent, add citric acid and a catalyst for grafting reaction to obtain a citric acid modified polypropylene solution;

[0008] S2. Dissolve the emulsifier in deionized water to form an emulsifier aqueous solution;

[0009] S3. Under stirring conditions, slowly add the citric acid modified polypropylene solution of S1 to the emulsifier aqueous solution of S2 to form a pre-emulsion;

[0010] S4. Transfer the pre-emulsion to a reaction kettle for emulsification, and remove the organic solvent by vacuum distillation to obtain a high molecular weight citric acid modified polypropylene aqueous dispersion.

[0011] Furthermore, in the preparation method, the dosages of the high molecular weight maleic anhydride grafted polypropylene resin, citric acid, emulsifier, and catalyst are 100 parts by mass, 20 parts by mass, 10 - 30 parts by mass, and 2 parts by mass respectively; the dosage of deionized water is 300 - 730 ml, and the dosage of the solvent is 200 - 250 ml.

[0012] Furthermore, the emulsification conditions of S4 are 60 - 100 °C for 2 - 4 hours.

[0013] Furthermore, the molecular weight of the high molecular weight maleic anhydride grafted polypropylene resin is greater than or equal to 10,000.

[0014] Furthermore, the organic solvent used is toluene, ethanol or a mixture thereof.

[0015] Furthermore, the emulsifier is selected from an anionic emulsifier, a non-ionic emulsifier or a mixture thereof.

[0016] Furthermore, the anionic emulsifier is sodium dodecylbenzenesulfonate, and the non-ionic emulsifier is polyoxyethylene octadecyl ether or polyetheramine M-1000.

[0017] Furthermore, the catalyst used is p-toluenesulfonic acid.

[0018] Furthermore, the solid content of the high molecular weight citric acid modified polypropylene aqueous dispersion is 15 - 30 wt%.

[0019] A high molecular weight citric acid modified polypropylene aqueous dispersion of the present invention has the following technical effects:

[0020] 1) The present invention uses the hydroxyl group of citric acid to carry out a condensation reaction with the 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, thereby improving the emulsification and dispersion characteristics;

[0021] 2) By the solution emulsification method, an organic solvent is used to dissolve high molecular weight polypropylene to make the solution viscosity lower, and a functionalized polypropylene aqueous dispersion with a molecular weight greater than 10,000 can be effectively prepared.

[0022] 3) By optimizing the type and dosage of the emulsifier, the good stability of the dispersion is ensured. Detailed implementation mode

[0023] The technical solution of the present invention will be further described below through examples.

[0024] Example 1

[0025] Maleic anhydride grafted polypropylene resin: 100 g (molecular weight of 20,000);

[0026] Citric acid: 20 g;

[0027] Sodium dodecylbenzenesulfonate: 15 g;

[0028] Deionized water: 400 mL;

[0029] p-Toluenesulfonic acid: 2 g;

[0030] Toluene: 200 mL.

[0031] S1. Further modification of polypropylene

[0032] Dissolve 100 g of maleic anhydride grafted polypropylene resin in 200 ml of toluene, add 20 g of citric acid and 2 g of p-toluenesulfonic acid, stir and heat up to 100 °C, and react for 4 h to obtain a citric acid modified polypropylene solution;

[0033] S2. Preparation of emulsifier aqueous solution

[0034] Dissolve 15 g of sodium dodecylbenzenesulfonate in 400 ml of deionized water to form an emulsifier aqueous solution;

[0035] S3. Pre-emulsification

[0036] Under stirring conditions, slowly add the citric acid modified polypropylene solution to the emulsifier aqueous solution to form a pre-emulsion;

[0037] S4. Emulsification

[0038] Transfer the pre-emulsion to a reaction kettle for emulsification, emulsify at 100 °C for 2 hours; then remove toluene by vacuum distillation to obtain a high molecular weight citric acid modified polypropylene aqueous dispersion with good dispersibility and stability, and the solid content is 25 wt%.

[0039] Example 2:

[0040] Maleic anhydride grafted polypropylene resin: 100 g (molecular weight 10,000);

[0041] Citric acid: 20 g;

[0042] Polyoxyethylene octadecanol ether: 30 g;

[0043] Deionized water: 500 mL;

[0044] p-Toluenesulfonic acid: 2 g;

[0045] Toluene: 200 mL;

[0046] Ethanol: 50 mL.

[0047] S1. Further modification of polypropylene

[0048] Mix 200 ml of toluene with 50 ml of ethanol, then dissolve 100 g of high molecular weight maleic anhydride grafted polypropylene resin in the toluene-ethanol mixture, add 20 g of citric acid and 2 g of p-toluenesulfonic acid, stir and heat to 100 °C, and react for 4 h to obtain a citric acid modified polypropylene solution;

[0049] S2. Preparation of emulsifier aqueous solution

[0050] Dissolve 30 g of polyoxyethylene octadecanol ether in 500 ml of deionized water to form an emulsifier aqueous solution;

[0051] S3. Pre-emulsification

[0052] Under stirring conditions, slowly add the citric acid modified polypropylene solution to the emulsifier aqueous solution to form a pre-emulsion;

[0053] S4. Emulsification

[0054] Transfer the pre-emulsion to a reaction kettle, emulsify at 90 °C for 2 h; then remove toluene and ethanol by vacuum distillation to obtain a high molecular weight citric acid modified polypropylene aqueous dispersion with good dispersibility and stability, and the solid content is 23 wt%.

[0055] Example 3:

[0056] Maleic anhydride grafted polypropylene resin: 100 g (molecular weight 30,000);

[0057] Citric acid: 20 g;

[0058] Sodium dodecylbenzenesulfonate: 6 g;

[0059] Polyoxyethylene octadecanol ether: 4 g;

[0060] Deionized water: 300 mL;

[0061] p-Toluenesulfonic acid: 2 g;

[0062] Toluene: 200 mL.

[0063] S1. Further modification of polypropylene

[0064] Dissolve 100 g of high molecular weight maleic anhydride grafted polypropylene resin in 200 ml of toluene, add 20 g of citric acid and 2 g of p-toluenesulfonic acid, stir and heat up to 100 °C, and react for 4 h to obtain a citric acid modified polypropylene solution;

[0065] S2. Preparation of emulsifier aqueous solution

[0066] Dissolve 6 g of sodium dodecylbenzenesulfonate and 4 g of polyoxyethylene octadecyl ether in 300 ml of deionized water to form an emulsifier aqueous solution;

[0067] S3. Pre-emulsification

[0068] Under stirring conditions, slowly add the citric acid modified polypropylene solution to the emulsifier aqueous solution to form a pre-emulsion;

[0069] S4. Emulsification

[0070] Transfer the pre-emulsion to a reaction kettle, emulsify at 70 °C for 2 hours; then remove toluene by vacuum distillation to obtain a high molecular weight citric acid modified polypropylene aqueous dispersion with good dispersibility and stability, and the solid content is 30 wt%.

[0071] Example 4:

[0072] Maleic anhydride grafted polypropylene resin: 100 g (molecular weight 10,000);

[0073] Citric acid: 20 g;

[0074] Sodium dodecylbenzenesulfonate: 5 g;

[0075] Polyetheramine M-1000: 5 g;

[0076] Deionized water: 500 mL;

[0077] p-Toluenesulfonic acid: 2 g;

[0078] Toluene: 200 mL.

[0079] S1. Further modification of polypropylene

[0080] Dissolve 100 g of high molecular weight maleic anhydride grafted polypropylene resin in 200 ml of toluene, add 20 g of citric acid and 2 g of p-toluenesulfonic acid, stir and heat up to 100 °C, and react for 4 h to obtain a citric acid modified polypropylene solution;

[0081] S2. Preparation of Aqueous Emulsifier Solution

[0082] Dissolve 5 g of sodium dodecylbenzenesulfonate and 5 g of polyetheramine M-1000 in 500 ml of deionized water to form an aqueous emulsifier solution;

[0083] S3. Pre-emulsification

[0084] Under stirring conditions, slowly add the citric acid-modified polypropylene solution to the aqueous emulsifier solution to form a pre-emulsion;

[0085] S4. Emulsification

[0086] Transfer the pre-emulsion to a reaction kettle and emulsify it at 80 °C for 4 hours; then remove toluene by vacuum distillation to obtain a high-molecular-weight aqueous dispersion of citric acid-modified polypropylene with good dispersibility and stability, and the solid content is 20 wt%.

[0087] Example 5:

[0088] Maleic anhydride grafted polypropylene resin: 100 g (molecular weight 10,000);

[0089] Citric acid: 20 g;

[0090] Sodium dodecylbenzenesulfonate: 8 g;

[0091] Polyoxyethylene octadecanol ether: 2 g;

[0092] Deionized water: 600 mL;

[0093] p-Toluenesulfonic acid: 2 g;

[0094] Toluene: 200 mL.

[0095] S1. Further Modification of Polypropylene

[0096] Dissolve 100 g of high-molecular-weight maleic anhydride grafted polypropylene resin in 200 ml of toluene, add 20 g of citric acid and 2 g of p-toluenesulfonic acid, stir and heat up to 100 °C, and react for 4 h to obtain a citric acid-modified polypropylene solution;

[0097] S2. Preparation of Aqueous Emulsifier Solution

[0098] Dissolve 8 g of sodium dodecylbenzenesulfonate and 2 g of polyoxyethylene octadecanol ether in 600 ml of deionized water to form an aqueous emulsifier solution;

[0099] S3. Pre-emulsification

[0100] Under stirring conditions, slowly add the citric acid-modified polypropylene solution to the aqueous emulsifier solution to form a pre-emulsion;

[0101] S4. Emulsification

[0102] Transfer the pre-emulsion to a reaction kettle and emulsify it at 80 °C for 2 hours; then remove toluene by vacuum distillation to obtain a high molecular weight waterborne dispersion of citric acid-modified polypropylene with good dispersibility and stability, and the solid content is 18 wt%.

[0103] Example 6:

[0104] Maleic anhydride grafted polypropylene resin: 100 g (molecular weight 10,000);

[0105] Citric acid: 20 g;

[0106] Sodium dodecylbenzenesulfonate: 2 g;

[0107] Polyetheramine M-1000: 8 g;

[0108] Deionized water: 730 mL;

[0109] p-Toluenesulfonic acid: 2 g;

[0110] Toluene: 200 mL.

[0111] S1. Further modification of polypropylene

[0112] Dissolve 100 g of high molecular weight maleic anhydride grafted polypropylene resin in 200 ml of toluene, add 20 g of citric acid and 2 g of p-toluenesulfonic acid, stir and heat up to 100 °C, and react for 4 h to obtain a citric acid-modified polypropylene solution;

[0113] S2. Preparation of emulsifier aqueous solution

[0114] Dissolve 2 g of sodium dodecylbenzenesulfonate and 8 g of polyetheramine M-1000 in deionized water to form an emulsifier aqueous solution;

[0115] S3. Pre-emulsification

[0116] Under stirring conditions, slowly add the citric acid-modified polypropylene solution to the emulsifier aqueous solution to form a pre-emulsion;

[0117] S4. Emulsification

[0118] Transfer the pre-emulsion to a reaction kettle and emulsify it at 60 °C for 4 hours; then remove toluene by vacuum distillation to obtain a high molecular weight waterborne dispersion of citric acid-modified polypropylene with good dispersibility and stability, the solid content is 15 wt%, and the particle size distribution is uniform.

[0119] Test the particle size, centrifugal stability and thermal storage stability of the high molecular weight polypropylene waterborne dispersions finally prepared in Examples 1-6, and the data results are shown in Table 1.

[0120] Table 1 Test Results of Performance Indicators of Related Products in Examples 1-6

[0121]

[0122] It can be seen from the data in Table 1 that the aqueous polypropylene dispersion of the present invention has good stability, and the particle size ranges from 5 to 35 μm.

[0123] The high-molecular-weight aqueous polypropylene dispersion prepared by the present invention can be widely applied to fields such as coatings, adhesives, and composite materials, and has broad application prospects.

[0124] The present invention is not limited to the embodiments discussed above. The above description of the specific embodiments is intended to describe and explain the technical solutions involved in the present invention. Obvious transformations, substitutions, or combinations based on the inspiration of the present invention should also be considered to fall within the protection scope of the present invention. The above specific embodiments are used to disclose the best implementation methods of the present invention, so that those of ordinary skill in the art can apply various embodiments and various alternative methods of the present invention to achieve the purpose of the present invention.

Claims

1. A method for preparing a waterborne dispersion of high molecular weight polypropylene by solution emulsification, characterized in that, It includes the following steps: S1. Dissolve the high molecular weight maleic anhydride grafted polypropylene resin in an organic solvent, add citric acid and a catalyst for grafting reaction to obtain a citric acid modified polypropylene solution; S2. Dissolve the emulsifier in deionized water to form an emulsifier aqueous solution; S3. Under stirring conditions, slowly add the citric acid modified polypropylene solution of S1 into the emulsifier aqueous solution of S2 to form a pre-emulsion; S4. Transfer the pre-emulsion to a reaction kettle for emulsification, and then remove the organic solvent by vacuum distillation to obtain a high molecular weight citric acid modified polypropylene aqueous dispersion; In the preparation method, the dosages of the high molecular weight maleic anhydride grafted polypropylene resin, citric acid, emulsifier and catalyst are 100 parts by mass, 20 parts by mass, 10 - 30 parts by mass and 2 parts by mass respectively; the dosage of deionized water is 300 - 730 ml, and the dosage of the solvent is 200 - 250 ml; The emulsifier is selected from an anionic emulsifier, a non-ionic emulsifier or a mixture thereof; wherein, the anionic emulsifier is sodium dodecylbenzenesulfonate, and the non-ionic emulsifier is octadecyl alcohol polyoxyethylene ether or polyetheramine M-1000.

2. The solution emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 1, characterized in that, The emulsification conditions of S4 are 60 - 100 °C for 2 - 4 hours.

3. The solution emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 1, characterized in that The molecular weight of the high molecular weight maleic anhydride grafted polypropylene resin is greater than or equal to 10,000.

4. The solution emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 1, characterized in that, The organic solvent used is toluene, ethanol or a mixture thereof.

5. The solution emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 1, characterized in that, The catalyst is p-toluenesulfonic acid.

6. The solution emulsification preparation method of a high molecular weight polypropylene aqueous dispersion according to claim 1, characterized in that, The solid content of the high molecular weight citric acid modified polypropylene aqueous dispersion is 15 - 30 wt%.

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