A process for the preparation of a high flow polypropylene resin

Abstract

The present application belongs to the technical field of polypropylene material, and provides a preparation method of high-fluidity polypropylene resin. In the present application, low-fluidity polypropylene material is heated and treated under the condition of existence of surfactant and dispersant in a high-pressure reaction kettle under closed condition at 180-230 DEG C and near-critical water, so as to realize degradation of polypropylene molecular chain in the low-fluidity polypropylene material, and high-fluidity polypropylene resin can be obtained after cooling to room temperature. The preparation method of the present application does not use degrading agent (organic peroxide), so it does not involve problems of recovery of the degrading agent and environmental pollution caused by the degrading agent; moreover, the preparation method of the present application is shorter in time, higher in efficiency and safer in equipment, the prepared high-fluidity polypropylene resin has no degrading agent (organic peroxide) residue, and the product quality is more stable; in addition, the use of degrading agent can avoid problems of toxicity, peculiar smell and high cost of the degrading agent.

Description

A method for preparing a high-flowability polypropylene resin Technical Field

[0001] This invention relates to the field of polypropylene materials technology, and more particularly to a method for preparing a high-flowability polypropylene resin. Background Technology

[0002] Polypropylene (PP), with its excellent properties in strength, chemical stability, and impact resistance, as well as its low production cost and recyclability, has experienced rapid global development and is widely used in many fields such as machinery parts, building materials, medical and health care, agriculture, forestry and fisheries. It is currently one of the most in-demand general-purpose plastics. High-flow polypropylene generally refers to polypropylene with a melt flow rate (MFR) higher than 20 g / 10 min. It has high flowability, strong melt strength, and good mechanical properties. It can not only be used to produce large and complex thin-walled injection molded products, but also to process thin-walled products under low injection pressure. Therefore, it is widely used in automobiles, home appliances, and daily necessities.

[0003] Currently, high-flowability polypropylene is produced using a degradation method. This method involves producing polypropylene powder with an MFR of 2.0–3.0 g / 10 min in the polymerization unit, followed by the addition of a peroxide degrading agent in the granulation unit to further degrade the MFR of the polypropylene to above 45 g / 10 min. However, existing degradation methods are complex to operate, and the use of peroxide degrading agents raises environmental concerns. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for preparing a high-flowability polypropylene resin. The preparation method provided by this invention is simple to operate and does not cause environmental problems.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing high-flowability polypropylene resin, comprising the following steps:

[0007] Low-flow polypropylene material, water, and additives are placed in a high-pressure reactor, which is then sealed. The reactor is heated to 180–230°C for heat treatment and then cooled to room temperature to obtain the high-flow polypropylene resin.

[0008] The low-flow polypropylene material includes low-flow polypropylene resin or low-flow polypropylene molding material, wherein the melt flow index of the low-flow polypropylene material at 230°C is 2.0 to 3.0 g / 10 min.

[0009] The volume of the water is 1 / 3 to 3 / 4 of the effective volume of the high-pressure reactor;

[0010] The mass ratio of the low-flow polypropylene material to water does not exceed 1:1;

[0011] The additives include surfactants and / or dispersants.

[0012] Preferably, the surfactant comprises one or more of stearate, sodium palmitate, oleate, alkyl cellulose, hexadecyltrimethylammonium bromide, hydroxyethyl cellulose, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium polyacrylate, and disproportionated rosin acid salt.

[0013] Preferably, the mass of the surfactant is 1 to 5% of the mass of the water.

[0014] Preferably, the dispersant comprises calcium hydroxyphosphate.

[0015] Preferably, the mass of the dispersant is 1 to 5% of the mass of the water.

[0016] Preferably, the heating rate to 180-230°C is 0.5-1°C / min.

[0017] Preferably, the heat treatment is carried out under stirring conditions, and the stirring speed is 300-600 rpm.

[0018] Preferably, the heat treatment pressure is 0.5 to 4.5 MPa and the time is 0.5 to 1.5 h.

[0019] Preferably, the particle size of the low-flow polypropylene material is 2-6 mm; before use, the low-flow polypropylene material is further subjected to pretreatment, which includes washing, crushing and sieving in sequence.

[0020] Preferably, the cooling is carried out under stirring and sealed conditions, and the cooling equipment is the cooling device of the high-pressure reactor;

[0021] After cooling to room temperature, the process further includes opening the high-pressure reactor and removing the material; performing solid-liquid separation on the material, discarding the liquid and retaining the slurry; and sequentially washing, drying, cooling, and sieving the slurry to obtain the high-flowability polypropylene resin.

[0022] This invention provides a method for preparing a high-flowability polypropylene resin.

[0023] The preparation method of this invention involves heating a low-flow polypropylene material in a high-pressure reactor at 200–250°C near-critical underwater in the presence of additives (surfactants and / or dispersants) in a sealed environment. This process degrades the polypropylene molecular chains in the low-flow polypropylene material. Cooling to room temperature yields a high-flow polypropylene resin. This method does not use degrading agents (organic peroxides), thus avoiding issues related to agent recovery and environmental pollution. Furthermore, the method is simple to operate, more efficient, and uses safer equipment. The resulting high-flow polypropylene resin has no residual degrading agents (organic peroxides), resulting in more stable product quality. Additionally, the absence of degrading agents avoids their toxicity, odor, and high cost. Moreover, the use of additives (surfactants and / or dispersants) ensures good dispersibility of the resulting polypropylene resin, which is beneficial for subsequent product processing. Attached Figure Description

[0024] Figure 1 shows the melt index curves of the high-flowability polypropylene resins obtained in Examples 1-5 at 230°C.

[0025] Figure 2 shows the appearance of the polypropylene resins obtained in Example 1 and Comparative Example 1. Detailed Implementation

[0026] This invention provides a method for preparing high-flowability polypropylene resin, comprising the following steps:

[0027] Low-flow polypropylene material, water, and additives are placed in a high-pressure reactor and the reactor is sealed. The reactor is then heated to 180–230°C for heat treatment and then cooled to room temperature to obtain the high-flow polypropylene resin.

[0028] The low-flow polypropylene material includes low-flow polypropylene resin or low-flow polypropylene molding material, wherein the melt index of the low-flow polypropylene material at 230°C is 2.0 to 3.0 g / 10 min.

[0029] The volume of the water is 1 / 3 to 3 / 4 of the effective volume of the high-pressure reactor;

[0030] The mass ratio of the low-flow polypropylene material to water does not exceed 1:1;

[0031] The additives include surfactants and / or dispersants.

[0032] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0033] In this invention, the low-flow polypropylene material includes low-flow polypropylene resin or low-flow polypropylene molding material, and the low-flow polypropylene material has a melt index of 2.0 to 3.0 g / 10 min at 230°C.

[0034] In this invention, the particle size of the low-flow polypropylene material is preferably 2-6 mm. Before using the low-flow polypropylene material, this invention preferably further includes pretreatment, which includes sequential washing, crushing, and sieving. In this invention, the washing reagent is preferably water. This invention does not specifically limit the number of washing cycles or the amount of washing reagent used, as long as the low-flow polypropylene material is cleaned effectively. This invention does not specifically limit the crushing and sieving processes, as long as a low-flow polypropylene material with a particle size of 2-6 mm is obtained.

[0035] In this invention, the water is preferably distilled water. The volume of the water is 1 / 3 to 3 / 4 of the effective volume of the high-pressure reactor, specifically preferably 1 / 3, 1 / 2, 2 / 3, or 3 / 4.

[0036] In this invention, the mass ratio of the low-flow polypropylene material to water does not exceed 1:1, and is preferably 10:1500, 100:1500, 500:1500, 1000:15000 or 1500:1500.

[0037] In this invention, the surfactant preferably comprises one or more of stearate, sodium palmitate, oleate, alkyl cellulose, hexadecyltrimethylammonium bromide, hydroxyethyl cellulose, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium polyacrylate, and disproportionated rosin acid salt, and more preferably sodium dodecylbenzenesulfonate. In this invention, the mass of the surfactant is preferably 1-5% of the mass of the water, specifically preferably 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0038] In this invention, the dispersant preferably comprises calcium hydroxyphosphate. In this invention, the mass of the dispersant is preferably 1-5% of the mass of the water, specifically preferably 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0039] In this invention, the temperature of the heat treatment is 180–230°C, preferably 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, or 230°C. In this invention, the pressure of the heat treatment is preferably 0.5–4.5 MPa, preferably 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, or 4.5 MPa; the time is preferably 0.5–1.5 h, preferably 0.5 h, 1.0 h, or 1.5 h. In this invention, the heating rate to 180–230°C is preferably 0.5–1°C / min, preferably 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, or 1°C / min. In this invention, the heat treatment is preferably carried out under stirring conditions, and the stirring speed is preferably 300 to 600 rpm, specifically 300 rpm, 400 rpm, 500 rpm or 600 rpm.

[0040] In this invention, the cooling is preferably carried out under stirring and sealed conditions, and the cooling equipment is preferably the cooling device of the high-pressure reactor.

[0041] After cooling to room temperature, the present invention preferably further includes: opening the high-pressure reactor and taking out the material; performing solid-liquid separation on the material, discarding the liquid and retaining the slurry; and sequentially washing, drying, cooling and sieving the slurry to obtain the high-flowability polypropylene resin.

[0042] The following detailed description of the preparation method of the high-flowability polypropylene resin provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] (1) The low-flow polypropylene resin raw material (melt index of 2.350 g / 10 min at 230℃) is washed, crushed and sieved to obtain low-flow polypropylene resin with a particle size of 2-6 mm; 10 g of low-flow polypropylene resin with a particle size of 2-6 mm is added to the high-pressure reactor through the solid feed port of the high-pressure reactor and the high-pressure reactor is sealed.

[0045] (2) Add 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the high-pressure reactor), 15 g of sodium dodecylbenzenesulfonate (the mass of sodium dodecylbenzenesulfonate is 1% of the mass of distilled water), and 15 g of calcium hydroxyphosphate (the mass of calcium hydroxyphosphate is 1% of the mass of distilled water) through the liquid feed port of the high-pressure reactor, and seal the high-pressure reactor. Stir continuously at a stirring speed of 500 rpm, and raise the temperature inside the high-pressure reactor to 190°C at a heating rate of 1°C / min. Stir at a constant temperature and pressure of 0.5 MPa for 1 h.

[0046] (3) After the heat treatment is completed, the cooling device of the high-pressure reactor is turned on under stirring and sealing conditions to cool down to room temperature.

[0047] (4) Open the high-pressure reactor, take out the material, separate the material into solid and liquid, discard the upper liquid and keep the lower slurry; dry, cool and screen the slurry to obtain high-flow polypropylene resin.

[0048] Example 2

[0049] (1) The low-flow polypropylene resin raw material (melt index of 2.350 g / 10 min at 230℃) is washed, crushed and sieved to obtain low-flow polypropylene resin with a particle size of 2-6 mm; 10 g of low-flow polypropylene resin with a particle size of 2-6 mm is added to the high-pressure reactor through the solid feed port of the high-pressure reactor and the high-pressure reactor is sealed.

[0050] (2) Add 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the high-pressure reactor), 15 g of sodium dodecylbenzenesulfonate (the mass of sodium dodecylbenzenesulfonate is 1% of the mass of distilled water), and 15 g of calcium hydroxyphosphate (the mass of calcium hydroxyphosphate is 1% of the mass of distilled water) through the liquid feed port of the high-pressure reactor, and seal the high-pressure reactor. Stir continuously at a stirring speed of 500 rpm, and heat the internal temperature of the high-pressure reactor to 200°C at a heating rate of 1°C / min. Stir at a constant temperature and pressure of 1.0 MPa for 1 h.

[0051] (3) After the heat treatment is completed, the cooling device of the high-pressure reactor is turned on under stirring and sealing to cool down to room temperature.

[0052] (4) Open the high-pressure reactor, take out the material, separate the material into solid and liquid, discard the upper liquid and keep the lower slurry; dry, cool and screen the slurry to obtain high-flow polypropylene resin.

[0053] Example 3

[0054] (1) The low-flow polypropylene resin raw material (melt index of 2.350 g / 10 min at 230℃) is washed, crushed and sieved to obtain low-flow polypropylene resin with a particle size of 2-6 mm; 10 g of low-flow polypropylene resin with a particle size of 2-6 mm is added to the high-pressure reactor through the solid feed port of the high-pressure reactor and the high-pressure reactor is sealed.

[0055] (2) Add 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the high-pressure reactor), 15 g of sodium dodecylbenzenesulfonate (the mass of sodium dodecylbenzenesulfonate is 1% of the mass of distilled water), and 15 g of calcium hydroxyphosphate (the mass of calcium hydroxyphosphate is 1% of the mass of distilled water) through the liquid feed port of the high-pressure reactor, and seal the high-pressure reactor. Stir continuously at a stirring speed of 500 rpm, and raise the temperature inside the high-pressure reactor to 210 °C at a heating rate of 1 °C / min. Stir at a constant temperature and pressure of 2.0 MPa for 1 h.

[0056] (3) After the heat treatment is completed, the cooling device of the high-pressure reactor is turned on under stirring and sealing conditions to cool down to room temperature.

[0057] (4) Open the high-pressure reactor, take out the material, separate the material into solid and liquid, discard the upper liquid and keep the lower slurry; dry, cool and screen the slurry to obtain high-flow polypropylene resin.

[0058] Example 4

[0059] (1) The low-flow polypropylene resin raw material (melt index of 2.350 g / 10 min at 230℃) is washed, crushed and sieved to obtain low-flow polypropylene resin with a particle size of 2-6 mm; 10 g of low-flow polypropylene resin with a particle size of 2-6 mm is added to the high-pressure reactor through the solid feed port of the high-pressure reactor and the high-pressure reactor is sealed.

[0060] (2) Add 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the high-pressure reactor), 15 g of sodium dodecylbenzenesulfonate (the mass of sodium dodecylbenzenesulfonate is 1% of the mass of distilled water), and 15 g of calcium hydroxyphosphate (the mass of calcium hydroxyphosphate is 1% of the mass of distilled water) through the liquid feed port of the high-pressure reactor, and seal the high-pressure reactor. Stir continuously at a stirring speed of 500 rpm, and heat the internal temperature of the high-pressure reactor to 220°C at a heating rate of 1°C / min. Stir at a constant temperature and pressure of 3.0 MPa for 1 h.

[0061] (3) After the heat treatment is completed, the cooling device of the high-pressure reactor is turned on under stirring and sealing to cool down to room temperature.

[0062] (4) Open the high-pressure reactor, take out the material, separate the material into solid and liquid, discard the upper liquid and keep the lower slurry; dry, cool and screen the slurry to obtain high-flow polypropylene resin.

[0063] Example 5

[0064] (1) The low-flow polypropylene resin raw material (melt index of 2.350 g / 10 min at 230℃) is washed, crushed and sieved to obtain low-flow polypropylene resin with a particle size of 2-6 mm; 10 g of low-flow polypropylene resin with a particle size of 2-6 mm is added to the high-pressure reactor through the solid feed port of the high-pressure reactor and the high-pressure reactor is sealed.

[0065] (2) Add 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the high-pressure reactor), 15 g of sodium dodecylbenzenesulfonate (the mass of sodium dodecylbenzenesulfonate is 1% of the mass of distilled water), and 15 g of calcium hydroxyphosphate (the mass of calcium hydroxyphosphate is 1% of the mass of distilled water) through the liquid feed port of the high-pressure reactor, and seal the high-pressure reactor. Stir continuously at a stirring speed of 500 rpm, and heat the internal temperature of the high-pressure reactor to 230°C at a heating rate of 1°C / min. Stir at a constant temperature and pressure of 4.0 MPa for 1 h.

[0066] (3) After the heat treatment is completed, the cooling device of the high-pressure reactor is turned on under stirring and sealing to cool down to room temperature.

[0067] (4) Open the high-pressure reactor, take out the material, separate the material into solid and liquid, discard the upper liquid and keep the lower slurry; dry, cool and screen the slurry to obtain high-flow polypropylene resin.

[0068] Example 6

[0069] The difference from Example 1 is that the mass of the surfactant is 2% of the mass of distilled water.

[0070] Example 7

[0071] The difference from Example 1 is that the mass of the surfactant is 3% of the mass of distilled water.

[0072] Example 8

[0073] The difference from Example 1 is that the mass of the surfactant is 4% of the mass of distilled water.

[0074] Example 9

[0075] The difference from Example 1 is that the mass of the surfactant is 5% of the mass of distilled water.

[0076] Example 10

[0077] The difference from Example 1 is that the surfactant is hydroxyethyl cellulose.

[0078] Example 11

[0079] The difference from Example 1 is that the surfactant is alkyl cellulose.

[0080] Example 12

[0081] The difference from Example 1 is that the surfactant is sodium polyacrylate.

[0082] Example 13

[0083] The difference from Example 1 is that no surfactant is added.

[0084] Example 14

[0085] The difference from Example 1 is that no dispersant is added.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that no dispersant and surfactant are added.

[0088] The melt flow rate of the high-flow polypropylene resins obtained in the examples and comparative examples at 230°C was tested using a melt flow rate tester. The melt flow rate results of the high-flow polypropylene resins obtained in Examples 1 to 5 at 230°C are shown in Table 1 and Figure 1. Figure 1 is a melt flow rate curve of the high-flow polypropylene resins obtained in Examples 1 to 5 at 230°C.

[0089] Table 1 Melt index of the high-flowability polypropylene resins obtained in Examples 1-5

[0090] Project Example 1 Example 2 Example 3 Example 4 Example 5 230℃ MFR (g / 10min) 63.38 473.0 658 8.47 998.11 0617.267 surface

[0091] As shown in Table 1 and Figure 1, the melt index of the prepared polypropylene increases with the increase of the heat treatment temperature.

[0092] The melt flow indexes of the high-flowability polypropylene resins obtained in Examples 6-14 and Comparative Example 1 are shown in Table 2.

[0093] Table 2 Melt index of the high-flowability polypropylene resins obtained in Examples 6-14 and Comparative Example 1.

[0094]

[0095]

[0096] As can be seen from Table 2, the melt index of the prepared polypropylene does not change much at the same temperature when using different surfactant concentrations, with an error of no more than 4%. Therefore, the melt index of polypropylene prepared by this method is relatively stable.

[0097] Figure 2 shows the appearance of the polypropylene resin obtained in Example 1 and Comparative Example 1. As can be seen from Figure 2, without the addition of surfactants or dispersants, polypropylene will stick together, which will have an adverse effect on the processing of subsequent products. Therefore, surfactants or dispersants need to be added to achieve the effect of dispersion.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-flowability polypropylene resin, characterized in that, The steps are as follows: Low-flow polypropylene material, water, and additives are placed in a high-pressure reactor, which is then sealed. The reactor is heated to 180-230°C for heat treatment, and then cooled to room temperature to obtain the high-flow polypropylene resin. The particle size of the low-flow polypropylene material is 2-6 mm. Before use, the low-flow polypropylene material undergoes pretreatment, which includes sequential washing, crushing, and sieving. The low-flow polypropylene material includes low-flow polypropylene resin or low-flow polypropylene molding material, and its melt index at 230°C is 2.0-3.0 g / 10 min. Cooling is carried out under stirring and sealed conditions, using the cooling device of the high-pressure reactor. After cooling to room temperature, the high-pressure reactor is opened, and the material is removed. The material undergoes solid-liquid separation, discarding the liquid and retaining the slurry. The slurry is then sequentially washed, dried, cooled, and... The high-flowability polypropylene resin is obtained by sieving; the volume of water is 1 / 2 of the effective volume of the high-pressure reactor; the mass ratio of the low-flowability polypropylene material to water does not exceed 1:1; the additives include surfactants and / or dispersants; the surfactants include one or more of stearate, sodium palmitate, oleate, alkyl cellulose, hexadecyltrimethylammonium bromide, hydroxyethyl cellulose, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium polyacrylate, and disproportionated rosin acid salt; the mass of the surfactant is 1-5% of the mass of the water; the dispersant includes calcium hydroxyphosphate; the mass of the dispersant is 1-5% of the mass of the water; the heating rate to 180-230℃ is 0.5-1℃ / min; the heat treatment is carried out under stirring conditions, the stirring speed is 300-600 rpm; the pressure of the heat treatment is 0.5-4.5 MPa, and the time is 0.5-1.5 h.

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