Preparation method of high-fluidity polypropylene resin

Abstract

The invention belongs to the technical field of polypropylene materials, and provides a preparation method of high-fluidity polypropylene resin. The low-fluidity polypropylene material is subjected to closed near-critical water heating treatment at the temperature of 180-230 DEG C in a high-pressure reaction kettle in the presence of a surfactant and a dispersing agent, degradation of polypropylene molecular chains in the low-fluidity polypropylene material is realized, and the low-fluidity polypropylene material is cooled to the room temperature to obtain the high-fluidity polypropylene resin. According to the preparation method disclosed by the invention, a degradation agent (organic peroxide) is not used, so that the problems of recycling of the degradation agent and environmental pollution caused by the degradation agent are solved; the preparation method is shorter in time, higher in efficiency and safe in equipment, and the prepared high-fluidity polypropylene resin is free of degradation agent (organic peroxide) residues and more stable in product quality; in addition, a degradation agent is not used, so that the problems of toxicity, peculiar smell and high cost of the degradation agent can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene materials, and in particular to a method for preparing a high-fluidity polypropylene resin. Background Art

[0002] Polypropylene (PP) has developed rapidly around the world and is widely used in many fields such as mechanical parts, building materials, medical and health care, agriculture, forestry and fishery, etc., due to its excellent performance in strength, chemical stability, impact resistance, low production cost and recyclability. It is one of the most in-demand general-purpose plastics. High-flowability polypropylene generally refers to polypropylene with a melt index (MFR) higher than 20g / 10min. It has high flowability, strong melt strength and good mechanical properties. It can not only be used to produce thin-walled injection molding products with large and complex structures, but also can realize the processing of thin-walled products under low injection pressure. Therefore, it is widely used in automobiles, household appliances, daily utensils and other fields.

[0003] At present, the production method of high-fluidity polypropylene includes a degradation method. The degradation method is to add a peroxide degradation agent to the granulation device after producing a polypropylene powder with an MFR of 2.0 to 3.0 g / 10 min in a polymerization device to further degrade the MFR of polypropylene to more than 45 g / 10 min. The existing degradation method is complicated to operate, and the use of peroxide degradation agents will bring environmental problems. Summary of the invention

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

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a high-fluidity polypropylene resin, comprising the following steps:

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

[0008] The low-fluidity polypropylene material includes a low-fluidity polypropylene resin or a low-fluidity polypropylene molding material, and the melt index of the low-fluidity 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-fluidity polypropylene material to water does not exceed 1:1;

[0011] The auxiliary agent includes a surfactant and / or a dispersant.

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

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

[0014] Preferably, the dispersant comprises calcium hydroxyphosphate.

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

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

[0017] Preferably, the heating treatment is performed under stirring conditions, and the stirring speed is 300-600 rpm.

[0018] Preferably, the heating treatment is performed at a pressure of 0.5 to 4.5 MPa and for a time of 0.5 to 1.5 h.

[0019] Preferably, the particle size of the low-fluidity polypropylene material is 2 to 6 mm. Before use, the low-fluidity polypropylene material is further subjected to pretreatment, and the pretreatment includes sequentially washing, crushing and screening.

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

[0021] After cooling to room temperature, the method 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 screening the slurry to obtain the high-fluidity polypropylene resin.

[0022] The invention provides a method for preparing a high-fluidity polypropylene resin.

[0023] The preparation method of the present invention is to heat the low-fluidity polypropylene material in a closed, 200-250°C, near-critical water in the presence of an auxiliary agent (surfactant and / or dispersant) in a high-pressure reactor, thereby achieving degradation of the polypropylene molecular chain in the low-fluidity polypropylene material, and cooling to room temperature to obtain a high-fluidity polypropylene resin. The preparation method of the present invention does not use a degradation agent (organic peroxide), so it does not involve the problem of recycling the degradation agent and the environmental pollution of the degradation agent; and the preparation method of the present invention is simple to operate, more efficient, and safe in equipment. The prepared high-fluidity polypropylene resin has no degradation agent (organic peroxide) residue, and the product quality is more stable; in addition, the use of the degradation agent can avoid the toxicity, odor and high cost of the degradation agent; in addition, the use of the auxiliary agent (surfactant and / or dispersant) makes the obtained polypropylene resin have good dispersibility, which is conducive to the processing of subsequent products. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The melt index curve of the high fluidity polypropylene resin obtained in Examples 1 to 5 at 230° C.

[0025] Figure 2 The following are appearance diagrams of the polypropylene resins obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a high-fluidity polypropylene resin, comprising the following steps:

[0027] Putting a low-fluidity polypropylene material, water and an additive into a high-pressure reactor, sealing the high-pressure reactor, heating the reactor to 180-230° C., and cooling the reactor to room temperature to obtain the high-fluidity polypropylene resin;

[0028] The low-fluidity polypropylene material includes a low-fluidity polypropylene resin or a low-fluidity polypropylene molding material, and the low-fluidity polypropylene material has a melt index of 2.0 to 3.0 g / 10 min at 230° C.;

[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-fluidity polypropylene material to water does not exceed 1:1;

[0031] The auxiliary agent includes a surfactant and / or a dispersant.

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

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

[0034] In the present invention, the particle size of the low-fluidity polypropylene material is preferably 2 to 6 mm. Before using the low-fluidity polypropylene material, the present invention preferably also includes pretreatment, and the pretreatment includes washing, crushing and screening in sequence. In the present invention, the cleaning agent is preferably water, and the present invention does not specifically limit the number of times of washing and the amount of the cleaning agent, as long as the low-fluidity polypropylene material can be cleaned; the present invention does not specifically limit the crushing and screening, as long as a low-fluidity polypropylene material with a particle size of 2 to 6 mm can be obtained.

[0035] In the present invention, the water is preferably distilled water. In the present invention, the volume of the water is 1 / 3 to 3 / 4 of the effective volume of the autoclave, and is preferably 1 / 3, 1 / 2, 2 / 3 or 3 / 4.

[0036] In the present invention, the mass ratio of the low-fluidity polypropylene material to water is not more than 1:1, and is preferably 10:1500, 100:1500, 500:1500, 1000:15000 or 1500:1500.

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

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

[0039] In the present invention, the temperature of the heat treatment is 180-230°C, and is 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 the present invention, the pressure of the heat treatment is preferably 0.5-4.5MPa, and is preferably 0.5MPa, 1MPa, 1.5MPa, 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa or 4.5MPa; the time is preferably 0.5-1.5h, and is preferably 0.5h, 1.0h or 1.5h. In the present invention, the heating rate of the temperature rise to 180-230°C is preferably 0.5-1°C / min, and is 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 the present invention, the heat treatment is preferably performed under stirring conditions, and the stirring speed is preferably 300 to 600 rpm, and specifically preferably 300 rpm, 400 rpm, 500 rpm or 600 rpm.

[0040] In the present invention, the cooling is preferably carried out under stirring and closed 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 comprises: opening the high-pressure reactor to take out the material; performing solid-liquid separation on the material, discarding the liquid, and retaining the slurry; and sequentially washing, drying, cooling and screening the slurry to obtain the high-fluidity polypropylene resin.

[0042] The preparation method of the high fluidity polypropylene resin provided by the present invention is described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] (1) A low-fluidity polypropylene resin raw material (melt index at 230° C. is 2.350 g / 10 min) is washed, crushed and sieved to obtain a low-fluidity polypropylene resin with a particle size of 2 to 6 mm; 10 g of the low-fluidity polypropylene resin with a particle size of 2 to 6 mm is added to an autoclave through a solid feed port of the autoclave, and the autoclave is sealed.

[0045] (2) 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the autoclave), 15 g of sodium dodecylbenzene sulfonate (the mass of sodium dodecylbenzene sulfonate 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) are added through the liquid feeding port of the autoclave, and the autoclave is closed. Stirring is continued at a stirring speed of 500 rpm, and the temperature inside the autoclave is raised to 190° C. at a heating rate of 1° C. / min, and stirring is carried out at a constant temperature and pressure of 0.5 MPa for 1 hour.

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

[0047] (4) opening the high-pressure reactor, taking out the material, separating the material into solid and liquid, discarding the upper layer of liquid, and retaining the lower layer of slurry; drying, cooling, and sieving the slurry to obtain a high-fluidity polypropylene resin.

[0048] Example 2

[0049] (1) A low-fluidity polypropylene resin raw material (melt index at 230° C. is 2.350 g / 10 min) is washed, crushed and sieved to obtain a low-fluidity polypropylene resin with a particle size of 2 to 6 mm; 10 g of the low-fluidity polypropylene resin with a particle size of 2 to 6 mm is added to an autoclave through a solid feed port of the autoclave, and the autoclave is sealed.

[0050] (2) 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the autoclave), 15 g of sodium dodecylbenzene sulfonate (the mass of sodium dodecylbenzene sulfonate 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) are added through the liquid feeding port of the autoclave, and the autoclave is closed. Stirring is continued at a stirring speed of 500 rpm, and the temperature inside the autoclave is heated to 200° C. at a heating rate of 1° C. / min, and stirring is carried out at a constant temperature and pressure of 1.0 MPa for 1 hour.

[0051] (3) After the heating treatment is completed, the high-pressure reactor cooling device is opened under stirring and sealed conditions to cool to room temperature.

[0052] (4) opening the high-pressure reactor, taking out the material, separating the material into solid and liquid, discarding the upper layer of liquid, and retaining the lower layer of slurry; drying, cooling, and sieving the slurry to obtain a high-fluidity polypropylene resin.

[0053] Example 3

[0054] (1) A low-fluidity polypropylene resin raw material (melt index at 230° C. is 2.350 g / 10 min) is washed, crushed and sieved to obtain a low-fluidity polypropylene resin with a particle size of 2 to 6 mm; 10 g of the low-fluidity polypropylene resin with a particle size of 2 to 6 mm is added to an autoclave through a solid feed port of the autoclave, and the autoclave is sealed.

[0055] (2) 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the autoclave), 15 g of sodium dodecylbenzene sulfonate (the mass of sodium dodecylbenzene sulfonate 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) are added through the liquid feeding port of the autoclave, and the autoclave is closed. Stirring is continued at a stirring speed of 500 rpm, and the temperature in the autoclave is raised to 210° C. at a heating rate of 1° C. / min. Stirring is carried out at a constant temperature and pressure of 2.0 MPa for 1 hour.

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

[0057] (4) opening the high-pressure reactor, taking out the material, separating the material into solid and liquid, discarding the upper liquid layer, and retaining the lower slurry; drying, cooling, and screening the slurry to obtain a high-fluidity polypropylene resin.

[0058] Example 4

[0059] (1) A low-fluidity polypropylene resin raw material (melt index at 230° C. is 2.350 g / 10 min) is washed, crushed and sieved to obtain a low-fluidity polypropylene resin with a particle size of 2 to 6 mm; 10 g of the low-fluidity polypropylene resin with a particle size of 2 to 6 mm is added to an autoclave through a solid feed port of the autoclave, and the autoclave is sealed.

[0060] (2) 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the autoclave), 15 g of sodium dodecylbenzene sulfonate (the mass of sodium dodecylbenzene sulfonate 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) were added through the liquid feeding port of the autoclave, and the autoclave was closed. Stirring was continued at a stirring speed of 500 rpm, and the temperature inside the autoclave was heated to 220° C. at a heating rate of 1° C. / min, and stirred at constant temperature and pressure for 1 h at 3.0 MPa.

[0061] (3) After the heating treatment is completed, the cooling device of the high-pressure reactor is opened under stirring and sealed conditions to cool to room temperature.

[0062] (4) opening the high-pressure reactor, taking out the material, separating the material into solid and liquid, discarding the upper layer of liquid, and retaining the lower layer of slurry; drying, cooling, and sieving the slurry to obtain a high-fluidity polypropylene resin.

[0063] Example 5

[0064] (1) A low-fluidity polypropylene resin raw material (melt index at 230° C. is 2.350 g / 10 min) is washed, crushed and sieved to obtain a low-fluidity polypropylene resin with a particle size of 2 to 6 mm; 10 g of the low-fluidity polypropylene resin with a particle size of 2 to 6 mm is added to an autoclave through a solid feed port of the autoclave, and the autoclave is sealed.

[0065] (2) 1500 mL of distilled water (the volume of distilled water is 1 / 2 of the effective volume of the autoclave), 15 g of sodium dodecylbenzene sulfonate (the mass of sodium dodecylbenzene sulfonate 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) are added through the liquid feeding port of the autoclave, and the autoclave is closed. Stirring is continued at a stirring speed of 500 rpm, and the temperature inside the autoclave is heated to 230° C. at a heating rate of 1° C. / min, and stirring is carried out at a constant temperature and pressure of 4.0 MPa for 1 hour.

[0066] (3) After the heating treatment is completed, the high-pressure reactor cooling device is opened under stirring and sealed conditions to cool to room temperature.

[0067] (4) opening the high-pressure reactor, taking out the material, separating the material into solid and liquid, discarding the upper layer of liquid, and retaining the lower layer of slurry; drying, cooling, and sieving the slurry to obtain a high-fluidity polypropylene resin.

[0068] Example 6

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

[0074] Example 9

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

[0076] Example 10

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

[0078] Embodiment 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] Embodiment 13

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

[0084] Embodiment 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 index of the high-fluidity polypropylene resin obtained in the examples and comparative examples at 230° C. was tested using a melt flow rate meter. The melt index results of the high-fluidity polypropylene resin obtained in Examples 1 to 5 at 230° C. are shown in Tables 1 and Figure 1 shown. Figure 1 The melt index curves of the high fluidity polypropylene resins obtained in Examples 1 to 5 at 230°C are shown.

[0089] Table 1 Melt index of high fluidity polypropylene resin obtained in Examples 1 to 5

[0090] project Example 1 Example 2 Example 3 Example 4 Example 5 230℃MFR(g / 10min) 63.384 73.065 88.479 98.110 617.267

[0091] From Table 1 and Figure 1 It can be seen that the melt index of the obtained polypropylene increases with the increase of the heating temperature.

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

[0093] Table 2 Melt index of high fluidity polypropylene resin obtained in Examples 6 to 14 and Comparative Example 1

[0094]

[0095]

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

[0097] Figure 2 The appearance of the polypropylene resin obtained in Example 1 and Comparative Example 1 is shown in FIG. Figure 2 It can be seen that without adding 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 is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a high-fluidity polypropylene resin, characterized in that: The following steps are involved: The low-fluidity polypropylene material, water and additives are placed in a high-pressure reactor, and the high-pressure reactor is sealed, heated to 180-230° C. for heating treatment, and then cooled to room temperature to obtain the high-fluidity polypropylene resin; The low-fluidity polypropylene material includes a low-fluidity polypropylene resin or a low-fluidity polypropylene molding material, and the melt index of the low-fluidity polypropylene material at 230° C. is 2.0 to 3.0 g / 10 min; The volume of the water is 1 / 3 to 3 / 4 of the effective volume of the high-pressure reactor; The mass ratio of the low-fluidity polypropylene material to water does not exceed 1:1; The auxiliary agent includes a surfactant and / or a dispersant.

2. The preparation method according to claim 1, characterized in that: The surfactant includes one or more of stearate, sodium palmitate, oleate, alkyl cellulose, cetyltrimethylammonium bromide, hydroxyethyl cellulose, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium polyacrylate and disproportionated rosin acid salt.

3. The preparation method according to claim 1 or 2, characterized in that: The mass of the surfactant is 1-5% of the mass of the water.

4. The preparation method according to claim 1, characterized in that: The dispersant includes calcium hydroxyphosphate.

5. The preparation method according to claim 1 or 4, characterized in that: The mass of the dispersant is 1-5% of the mass of the water.

6. The preparation method according to claim 1, characterized in that: The heating rate to 180-230° C. is 0.5-1° C. / min.

7. The preparation method according to claim 1, characterized in that: The heating treatment is performed under stirring conditions, and the stirring speed is 300-600 rpm.

8. The preparation method according to claim 1 or 7, characterized in that: The heating treatment is performed at a pressure of 0.5 to 4.5 MPa and for a time of 0.5 to 1.5 h.

9. The preparation method according to claim 1, characterized in that: The particle size of the low-fluidity polypropylene material is 2-6 mm. Before use, the low-fluidity polypropylene material is further pretreated, and the pretreatment includes washing, crushing and screening in sequence.

10. The preparation method according to claim 1, characterized in that: The cooling is carried out under stirring and airtight conditions, and the cooling equipment is a cooling device of the high-pressure reactor; After cooling to room temperature, the method 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 screening the slurry to obtain the high-fluidity polypropylene resin.

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