Method for Preparing Polyvinyl Chloride by Suspension and Polymerization, and Feeding Device

Abstract

The present invention provides a production method of polyvinyl chloride by suspension polymerization and a feeding apparatus. This method comprises: Step 1: injecting a vinyl chloride monomer and water at 25-98° C. into a reaction vessel to obtain a water suspension, closing the reaction kettle, repeatedly and cyclically performing vacuum-pumping and cleansing with nitrogen, stirring and evacuating oxygen in the reaction kettle; Step 2: adding a first suspension agent and a second suspension agent into the reaction kettle, and then adding a nanopowder and an initiator composite, to carry out the polymerization reaction; Step 3: adding cold water to terminate the polymerization reaction upon the pressure in the reaction kettle is reduced to 3.5 bar or less; Step 4: evacuating and vacuumizing the reaction kettle, and then filtering, washing and drying the resulted polymer, to obtain polyvinyl chloride. The present invention also provides a feeding apparatus used for the above production method. Polyvinyl chloride produced by the method of this invention has good performance and can meet the requirements of physical and chemical properties and applicability for most applications.

Claims

1. A production method of polyvinyl chloride by suspension polymerization, comprising the steps of: Step 1: injecting a vinyl chloride monomer and water at 25° C. to 98° C. into a reaction kettle to obtain a water suspension, closing the reaction kettle, repeatedly and cyclically performing vacuum-pumping and cleansing with nitrogen, stirring, to evacuate oxygen in the reaction kettle; Step 2: adding a first suspension agent and a second suspension agent into the reaction kettle, and then adding a suspension stabilizer and an initiator composite, to carry out the polymerization reaction; Step 3: adding a cold water to terminate the polymerization reaction when the pressure in the reaction kettle is reduced to 3.5 bar or less; Step 4: evacuating and vacuumizing the reaction kettle, and then filtering, washing and drying the resulted polymer, to obtain polyvinyl chloride; wherein, the vinyl chloride monomer and water are in a ratio by mass of 1:3-1:0.5; the first suspension agent is a polyvinyl alcohol having an alcoholysis degree of 95-66%, and the second suspension agent is a polyvinyl alcohol having an alcoholysis degree of 80-60%; the starting materials of the initiator composite include chloroformate, peroxide, organic acid anhydride and sodium hydroxide in a ratio by mass of 3-7:0.5-1.5:0.5-2:2-4; the first suspension agent is added at an amount of 200-500 ppm, the second suspension agent is added at an amount of 800-1000 ppm, the suspension stabilizer is added at an amount of 2800-3300 ppm, the initiator composite is added at an amount of 2700-3600 ppm, in relative to the mass of the vinyl chloride monomer.

2. The production method according to claim 1, wherein the initiator composite is added in two portions: for the first time, 30% to 70% is added before the reaction: firstly adding a chloroformate and an organic acid anhydride, and then adding a peroxide and sodium hydroxide; for the second time, after the start of the reaction, the remaining initiator composite is added before the half-life of the previously added initiator composite: firstly adding the remaining chloroformate and the organic acid anhydride, and then adding the remaining peroxide and sodium hydroxide.

3. The production method according to claim 1, wherein the first suspension agent is a polyvinyl alcohol having an alcoholysis degree of 88%, and the second suspension agent is a polyvinyl alcohol having an alcoholysis degree of 72%.

4. The production method according to claim 1, wherein the chloroformate, the peroxide, the organic acid anhydride and sodium hydroxide in the initiator composite are in a ratio by mass of 5:1:1.5:3.

5. The production method according to claim 1, wherein the vinyl chloride monomer and water are in a ratio by mass of 1:1.

6. The production method according to claim 1, wherein the suspension stabilizer contains zinc oxide, a nanopowder and an organic acid salt compound, and the nanopowder contains magnesium hydroxide and aluminum hydroxide.

7. The production method according to claim 6, wherein the amount of magnesium hydroxide is 4-12 wt % and the amount of aluminum hydroxide is 2-8 wt %, in relative to the weight of the water suspension, and the zinc oxide, the nanopowder and the organic acid salt compound are in a ratio by mass of 1:3:3.

8. The production method according to claim 7, wherein the amount of magnesium hydroxide is 7-8%, the amount of aluminum hydroxide is 4%, in relative to weight of the suspension of water and the monomer.

9. The production method according to claim 6, wherein the organic acid salt compound has a structural formula:
[M.sup.2+.sub.1-xM.sup.3+.sub.x(OH)].sup.x+(A.sup.n−.sub.x/y).yH.sub.2O M.sup.2+ represents a divalent metal cation selected from the group consisting of Mg, Ca, Zn, and Co; M.sup.3+ represents Al.sup.3+ or Bi.sup.3+; A.sup.n− represents an anion having a valence of 1 to 4 and includes HCO.sub.3.sup.−, Cl.sup.−, CO.sub.3.sup.2− or CH.sub.3COO.sup.−; x and y are numbers in the following ranges:0.2<x<0.33 and y>0.

10. The production method according to claim 1, wherein the method further comprises the steps of adding a primary dispersant and a secondary dispersant; the primary dispersant is a polyvinyl alcohol having an alcoholysis degree of 80-72.5%; and the primary dispersant is added at an amount of 800-1500 ppm, in relative to the weight of the water suspension; the secondary dispersant is a polyvinyl alcohol having an alcoholysis degree of 35-55%.

11. The production method according to claim 10, wherein the primary dispersant is added in Step 1, and the secondary dispersant is added in Step 2.

12. The production method according to claim 1, the chloroformate has a molecular formula of ClCOOR.sub.1, wherein R.sub.1 is methyl, ethyl, isopropyl, m-propyl or 2-ethyl; the organic acid anhydride has a molecular formula of (RCO).sub.2O, wherein R is methyl or ethyl; the peroxide is hydrogen peroxide and/or sodium peroxide.

13. The production method according to claim 12, wherein the organic acid anhydride comprises propionic anhydride, isopropionic anhydride or the like.

14. The production method according to claim 12, wherein the starting materials of the initiator composite comprise ethyl chloroformate, hydrogen peroxide, propionic anhydride and sodium hydroxide.

15. The production method according to claim 12, wherein the m of the m-propyl is 1.

16. The production method according to claim 1, wherein the vacuum-pumping treatment to the reaction kettle is carried out at 42-48 mbar, 33-37° C. for 45 minutes, the washing is carried out by using reverse osmosis water, and the temperature for drying is 50-60° C.

17. The production method according to claim 1, wherein an anti-sticking-to-kettle agent is first added to the reaction kettle to perform treatment prior to the addition of the vinyl chloride monomer and water.

18. A feeding apparatus for the production method of polyvinyl chloride by suspension polymerization according claim 1, which comprises: a peroxide vessel, a peroxide storage tank, a sodium hydroxide solution vessel, a sodium hydroxide solution storage tank, a chloroformate storage drum, an organic acid anhydride storage drum, a waste liquid tank, a washing tower, an box for automatic drums handling, and an inlet pipe for starting material water; the peroxide solution vessel is connected to the peroxide storage tank by a first pump, and the peroxide solution storage tank is connected to the inlet pipe for starting material water by a first feeding pump; the sodium hydroxide solution vessel is connected to the sodium hydroxide solution storage tank by a second pump, and the sodium hydroxide solution storage tank is connected to the inlet pipe for starting material water by a second feeding pump; the chloroformate storage drum and the organic acid anhydride storage drum are arranged in the box for automatic drums handling, and the box for automatic drums handling is provided with an exhaust ventilation device, a blower and a vertical pump; the blower is connected to the washing tower, and the vertical pump is connected to the waste liquid tank; one end of the inlet pipe for starting material water is used for inputting the starting material water, and the other end thereof is connected to the top of the reaction kettle; the chloroformate storage drum is connected to the inlet pipe for starting material water by a third feeding pump, and the organic acid anhydride storage drum is connected to the inlet pipe for starting material water by a fourth feeding pump; the bottom of the washing tower is connected to the waste liquid tank; the waste liquid tank is provided with a sodium hydroxide inlet pipe; the waste liquid tank is connected to the outside of the apparatus by a fourth pump.

19. The feeding apparatus for the production method of polyvinyl chloride by suspension polymerization according to claim 18, characterized in that, a pipeline on top of the washing tower is connected to an incineration collection place outside the feeding apparatus, and a pipeline on the left side of the washing tower is connected to a waste liquid treatment device outside the feeding apparatus.

20. The feeding apparatus for the production method of polyvinyl chloride by suspension polymerization according to claim 18, characterized in that, the waste liquid tank is connected to a press-filter device outside the feeding apparatus by the fourth pump.

Description

DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1 is a structural schematic view of the feeding apparatus provided in Example 2;

[0051] FIGS. 2-5 are transmission electron microscope photographs of the PVC produced in the examples.

DESCRIPTION OF MAIN REFERENCE NUMBERS

[0052] peroxide vessel 1, peroxide storage tank 2, sodium hydroxide solution vessel 3, sodium hydroxide solution storage tank 4, chloroformate storage drum 5, organic acid anhydride storage drum 6, waste liquid tank 7, washing tower 8, box for automatic drums handling 9, inlet pipe for starting material water 10, exhaust ventilation device 11, blower 12, sodium hydroxide inlet pipe 13, first pump 101, second pump 102, vertical pump 103, fourth pump 104, first feeding pump 201, second feeding pump 202, third feeding pump 203, fourth feeding pump 204

DETAILED DESCRIPTION OF EMBODIMENT

[0053] The technical solutions of the present invention will now be described in detail in order to provide a clearer understanding of the technical features, objects and advantages of the present invention, but are not to be construed as limiting the scope of the invention.

Example 1

[0054] This example provides a production method of polyvinyl chloride by suspension polymerization, which comprises the following steps:

adding an anti-sticking-to-kettle agent into a reaction kettle for treatment;
adding water and a VCM monomer into the reaction kettle to obtain a suspension of water and the monomer, and then closing the reaction kettle, repeatedly and cyclically performing vacuum-pumping (11 bar) and cleansing with nitrogen (4 bar), stirring at a speed of 400 rpm and evacuating oxygen in the reaction kettle;
to the reaction kettle, a first suspension agent (primary PVA1) and a second suspension agent (primary PVA2) are added, and then a suspension stabilizer (Appak Nano1000) and an initiator composite (Irispak system) are added, to carry out the polymerization reaction;
adding a cold water to terminate the polymerization reaction upon the pressure in the reaction kettle is reduced to 3.5 bar or less;
evacuating and vacuumizing the reaction kettle, and then filtering, washing and drying the resulted polymer, to obtain polyvinyl chloride;
wherein, the VCM monomer and water are in a ratio by mass of 1:1, and the temperature of water is 25-98° C.;
in relative to mass of the vinyl chloride monomer, the amount of the first suspension agent added, the amount of the second suspension agent added, the amount of the suspension stabilizer added, and the amount of the initiator composite added are as shown in Table 1.

[0055] PVC of each specifications prepared in Example 1 was subjected to three groups of tests. The specific amounts of components and the reaction conditions and the reaction results are as shown in Table 1.

TABLE-US-00001 TABLE 1 K57 K65 K67 K70 PVC Hard injection Pipe Extrusion Soft specifications molding grade grade product Testing T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 Primary 850 870 900 990 1050 1150 825 850 895 990 1000 1200 PVA1 & 2 (ppm) Appak 2900 3150 3280 2980 3120 3210 2900 3100 3200 2950 3000 3100 Nano1000 (ppm) Irispak 2800 2900 3000 3250 3350 3500 3000 3150 3350 2200 2350 2500 system (ppm) Irispak 1400 1450 1500 1625 1675 1750 1500 1575 1675 1100 1175 1250 initial feeding, % Irispak 1400 1450 1500 1625 1675 1750 1500 1575 1675 1100 1175 1250 successive feeding, % Reaction 70 70 70 60 60 60 56 56 56 60 60 60 temperature (° C.) Reaction 267 248 260 251 255 250 246 240 240 342 342 324 time (min) Temperature Cold Cold Hot Cold Hot Hot Cold Hot Hot Cold Hot Hot for adding water If a buffer No No No No No No No No No No No No was used If a killing No No No No No No No No No No No No agent was used Operation No Yes Yes No Yes Yes No Yes Yes No Yes Yes of the reflux condenser Injection of Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes cooling water Final 90 91 92 91 91 91 89 89 91 89 90 91 conversion rate %

[0056] Wherein, the primary PVA1 has an alcoholysis degree of 88%, the primary PVA2 has an alcoholysis degree of 72%, and the ratio by mass of these two is 1:3;

[0057] Appak Nano 1000 is a solution composed of zinc oxide, a nanopowder (consisting of magnesium hydroxide and aluminum hydroxide, which are in amount of 7-8% and 4% in water suspension, respectively; having particle size of 600-200 nm), and an organic acid salt (the organic acid salt is Al.sub.2Mg.sub.4.5(OH).sub.13CO.sub.3.xH.sub.2O), at a ratio by mass of 1:3:3;

the initial addition of Irispak and the successive addition of Irispak mean that the initiator composite is added in two portions: for the first time, 50% is added before the reaction: firstly adding a chloroformate and an propionic acid anhydride, and then a hydrogen peroxide and sodium hydroxide; for the second time, after the start of the reaction, the remaining initiator composite is added before the half-life of the previously added initiator composite: firstly adding the remaining chloroformate and the propionic acid anhydride, and then adding the remaining hydrogen peroxide and sodium hydroxide; these starting material will form the initiator composite in the kettle;
In the temperature at which water is added, cold refers to the water at normal temperature, and hot refers to the water at 50-60° C.

[0058] The results of the quality of the finished product PVC are tested, specifically, in accordance with the following steps:

100 g of PVC resin was mixed with 3.5 g of orgartotin and 1.5 g of epoxidized soybean oil (ESO); the obtained mixture was ground by using a Brabender Torque Rheometry for 6 minutes (The initial temperature of laboratory chamber is set at 175° C. and the rotor speed is 50 rpm), and then molded into a thin sample sheet by a laboratory press machine at the condition of 185° C. and 30 mPa for 10 minutes.

[0059] The thin sample sheet (ie, PVC spline) was sliced using a diamond knife at the impact of a simple beam. The sliced sample was observed and photographed by a JEM-1230 transmission electron microscope (JEOL Co., Japan), specifically, as shown in FIGS. 2-5. From FIGS. 2-5, it can be seen, that the active ingredient (nanopowder) enters or partially enters the interior of the particles, from the slice experiment of polyvinyl chloride particles, providing an objective and observable support for the improvement of its physical and chemical properties.

[0060] The thermal stability of PVC was mainly detected by Congo red analysis and thermogravimetric analysis (TGA), taking into account the steps of the Congo red analysis method described in DIN 53381. The change in color on the Congo red test paper was observed by gradually changed HCl, and the elapsed time was measured when the PVC resin is heated to 175° C.

[0061] The thermal degradation of PVC was measured using a Perkin-Elmer Pyrts-1 TGA heating analyzer at a temperature raising rate of 10° C./min under nitrogen condition. The “reverse feeding” mode was used to successfully carry out VCM suspension polymerization. The slurry and PVC resin are separated to obtain transparent water, indicating that Appak stabilizer nanoparticles can be effectively bonded to PVC particles.

[0062] As can be seen from the above, the thermal stability of the obtained PVC resin is longer than that of the pure PVC resin and increases with the increase of the Appak Nano1000. HCL derived from dehydrochlorination in the PVC chain has an automatic catalytic effect on the thermal degradation of PVC. Because the metal nanostabilizer enters the PVC resin, hydrogen chloride can be absorbed by the metal nanostabilizer, and react with the CO.sub.3.sup.2− anion between the metal layers. Thus the degradation of PVC is prevented, and the time of thermal stability for PVC resin is increased.

[0063] The quality testing results of the produced PVC are as shown in Table 2.

[0064] Each of the quality testing results of the finished PVC given in Table 2 shows that each of products produced for all K values have reached fairly stable and satisfactory level with good a particle size distribution (for example, the testing result of the particle size distribution of PVC for K65 hard pipe is: D10=79.76 μm, D50=115.48 μm, D90=178.71 μm, D99=288.46 μm), high apparent density, and enhanced thermal stability (Congo red analysis). The major range of the assessment is to verify that whether the use of Irispak system technology (different initiation systems and components, shortened polymerization time, use of cold water, use of reflux condenser) has a negative influence on the major process, and whether it has a negative effect on the standard PVC characteristics. The answer is no negative influence and no negative effect existing.

TABLE-US-00002 TABLE 2 K57 K67 K70 PVC Hard injection K65 Extrusion Soft specifications molding grade Pipe grade product Testing T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 Viscosity 76 80 78 102 103 105 111 114 112 125 126 128 (ml/g) apparent 0.560 0.562 0.595 0.505 0.515 0.510 0.570 0.590 0.591 0.492 0.495 0.491 density (g/cm.sup.3) particle <2.2 <2.1 <2.1 <0.5 <0.6 <0.55 <2.1 <1.9 <2.2 <0.52 <0.6 <0.58 size >250 μm (%) particle >91 >95 >93 >91 >93 >94 >94 >96 >93 >97 >94 >93 size >60 μm (%) Plasticizer 14 16 17 25 26 28 17 18 19 32 34 36 absorption (%) Thermal High High Very Very Very Very High Very Very High High Very stability high high high high high high high (tendency) Volatile <0.31 <0.19 <0.23 <0.11 <0.29 <0.28 <0.43 <0.41 <0.41 <0.32 <0.29 <0.28 content (%)

Results of Final Polymerization Process:

[0065] In order to increase the yield of the reaction kettle, the polymerization water is added as it has reached a sufficient high temperature, and the specific polymerization temperature at the end of the addition of water is 50-75° C.

[0066] Compared with the use of conventional catalysts (slow), even with the use of rapid catalysts, the technical solution provided in present invention gives a significant improvement. When a rapid catalyst is contacted with water at a high temperature (usually around 90° C.), it would immediately produce a great amount of active free radicals which will be partially self-degraded, self-recombined, partially formed into glassy and/or low molecular weight polymeric particles. Thus, this problem will be further aggravated when it is desired to use the Irispak system instead of using a preformed rapid catalyst, because the composition of the produced Irispak system is very unstable, and the higher the temperature the faster decomposition. As a result, the reaction is irregular and the free radical distribution in the polymer particles is not uniform, resulting in unevenness in the particle size, porosity and molecular weight of the polymer itself. Surprisingly, by using the formulation of the present invention, none of the above problems arise when the water at a high temperature was added, this is primarily attributed to the successive feeding during the process of the polymerization reaction (50% was added firstly, and the remaining 50% was gradually added over 2-3 hours as the reaction progressed). A reflux condenser can be used at same time to keep the temperature of the polymerization reaction in an appropriate range, the reaction can be terminated by injection of cold water, and the final conversion rate is improved, which also bring more critical advantages. It is to be noted that the polymerization process can freely carry out cold water and hot water feeding at the start of the polymerization.

Example 2

[0067] This example provides a feeding apparatus for the above production method of polyvinyl chloride by suspension polymerization, the structure of which is as shown in FIG. 1. This feeding apparatus comprises: a peroxide vessel 1, a peroxide storage tank 2, a sodium hydroxide solution vessel 3, a sodium hydroxide solution storage tank 4, a chloroformate storage drum 5, an organic acid anhydride storage drum 6, a waste liquid tank 7, a washing tower 8, a box for automatic drums handling 9, and an inlet pipe for starting material water 10;

the peroxide vessel 1 is connected to the peroxide storage tank 2 by a first pump 101, and the peroxide storage tank 2 is connected to the inlet pipe for starting material water 10 by a first feeding pump 201;
the sodium hydroxide solution vessel 3 is connected to the sodium hydroxide solution storage tank 4 by a second pump 102, and the sodium hydroxide solution storage tank 4 is connected to the inlet pipe for starting material water 10 by a second feeding pump 202;
the chloroformate storage drum 5 and the organic acid anhydride storage drum 6 are arranged in the box for automatic drums handling 9, and the box for automatic drums handling 9 is provided with an exhaust ventilation device 11, a blower 12 and a vertical pump 103; the blower 12 is connected to the washing tower 8, and the vertical pump 103 is connected to the waste liquid tank 7;
the chloroformate storage drum 5 is connected to the inlet pipe for starting material water 10 by a third feeding pump 203, and the organic acid anhydride storage drum 6 is connected to the inlet pipe for starting material water 10 by a fourth feeding pump 204;
one end of the inlet pipe for starting material water 10 is used for inputting the starting material water and the other end is connected to the top of the reaction kettle, and various starting materials can be brought into the reaction kettle through the input water;
the bottom of the washing tower 8 is connected to the waste liquid tank 7;
the waste liquid tank 7 is provided with a sodium hydroxide inlet pipe 13;
the waste liquid tank 7 is connected to the outside of the device by a fourth pump 104.

[0068] In the practice of the production method of polyvinyl chloride by suspension polymerization, for example, the method according to example 1, the operation can be performed in the following manner:

the solutions of hydrogen peroxide and sodium hydroxide are added to the peroxide vessel 1 and the sodium hydroxide solution vessel 3, respectively, and when used, they are input into the peroxide storage tank 2 and the sodium hydroxide solution storage tank 4 respectively by the first pump 101 and the second pump 102; when they are required to be added to the reaction kettle, solutions of hydrogen peroxide and sodium hydroxide are added into the inlet pipe for starting material water 10 respectively by the first feeding pump 201 and the second feeding pump 202, and added through the inlet on top of the reaction kettle via the inlet pipe for starting material water 10;
chloroformate and the propionic acid anhydride are stored in the chloroformate storage drum 5 and the organic acid anhydride storage drum 6, respectively; when they are required to be added, chloroformate and the propionic acid anhydride are added into the inlet pipe for starting material water 10 respectively by the third feeding pump 203 and the fourth feeding pump 204, and added through the inlet on top of the reaction kettle via the inlet pipe for starting material water 10;
when the material concentration in the box for automatic drums handling 9 is too high, it can be adjusted by the blower 12 and the exhaust ventilation device 11; the generated waste liquid is collected and injected into the waste liquid tank 7 by the vertical pump 103, and is processed by the washing tower 8; the sodium hydroxide solution required for the washing tower 8 is added through the sodium hydroxide inlet pipe 13; the pipe on top of the washing tower 8 is connected to the incineration collection place for outputting the generated gas from washing; the bottoms of the waste liquid tank 7 and the washing tower 8 are connected to the waste liquid treatment device outside by the fourth pump 104 for further processing of the waste liquid.