WO2016075567A1

WO2016075567A1 - Preparation of chlorinated polyvinyl chloride

Info

Publication number: WO2016075567A1
Application number: PCT/IB2015/057966
Authority: WO
Inventors: Pradip Munshi; Jayesh P VORA; Ninad Deepak INGLE; Pradeep Paresh KAPADIA; Raksh Vir Jasra; Shashikant RAJAN; Ajit Behari Mathur
Original assignee: Reliance Industries Limited
Priority date: 2014-11-11
Filing date: 2015-10-16
Publication date: 2016-05-19

Abstract

The present disclosure relates to an apparatus and a process for the preparation of chlorinated polyvinyl chloride (CPVC). The apparatus includes a chamber (16), at least one sparger tube (12), at least one agitator (2) and at least two baffles (18) fitted in the chamber and a plurality of irradiation sources (20) fitted inside the baffles in order to bring about accelerated photochlorination of polyvinyl chloride. The process includes reacting polyvinyl chloride (PVC) with chlorine in the presence of irradiation of wavelength ranging from 250 and 550 nm and power ranging from 0.01 to 0.04 Watt/ g of PVC, under agitation at a speed ranging from 100 to 1600 rpm, for a time period ranging from 2 to 12 hours, to obtain CPVC.

Description

PREPARATION OF CHLORINATED POLYVINYL CHLORIDE

FIELD

The present disclosure relates to chlorinated polyvinyl chloride (CPVC). Particularly, the present disclosure relates to an apparatus and a process for the preparation of CPVC.

BACKGROUND

Chlorinated polyvinyl chloride (CPVC) is a thermoplastic polymer that is characterized by properties such as high glass transition (Tg), fire resistance, corrosion resistance, superior ductility, and good flexural and crush resistance, which enables its use in industrial liquid handling applications such as hot and cold water pipes. CPVC is generally prepared by free radical chlorination reaction, wherein chlorine gas is initially decomposed into free radicals of chlorine by thermal or ultra violet (UV) energy, following which, the free radicals reacts with PVC to form CPVC.

Photo-chlorination of PVC in suspension form is a heterogeneous reaction which is primarily driven by mass transfer phenomenon and is controlled by diffusion of chlorine into the pores of the PVC particles. As chlorine diffusion is the rate limiting step, efforts have been directed towards increasing the rate of the reaction by using various strategies. Improved stirring is one such technique known in the art. The pore size of PVC can also be increased to facilitate chlorine diffusion as recited in US patent 4412898. US 4049517 discloses the use of ramping irradiation in order to control the rate of reaction. Elevating the temperature to enhance the rate of the reaction is also known in the art. US 4377459 recites subjecting the PVC dissolved in organic solvent to chlorine gas at a high pressure so as to accelerate the rate of reaction. The rate of the reaction can also be controlled by supplying controlled UV in the reactor as disclosed in US 4049517. US 3328371 discloses the use of additives such as chlorinating agents (S0₂C1₂) and swelling agents in order to further increase the rate of the reaction. US 6197895 recites adding organic peroxide compounds to the PVC suspension in order to increase the rate of chlorination.

It is evident that most of the afore-stated processes have the limitation of using raw materials with certain physical specifications and inclusion of certain reagents and additives which makes the process expensive.

The inventors of the present disclosure envisage a simple apparatus and a relatively less expensive process to bring about photochlorination of PVC at an increased rate in order to mitigate the drawbacks associated with the prior art processes.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment is able to achieve, are discussed herein below.

It is an object of the present disclosure to provide an apparatus for the preparation of chlorinated polyvinyl chloride (CPVC).

It is another object of the present disclosure to provide an apparatus for the preparation of chlorinated polyvinyl chloride (CPVC), which has industrial applicability.

It is yet another object of the present disclosure to provide a process for the preparation of chlorinated polyvinyl chloride (CPVC).

It is still another object of the present disclosure to provide a process for the preparation of chlorinated polyvinyl chloride (CPVC), which is rapid, simple and environment friendly.

It is yet another object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative. Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.

SUMMARY

In accordance with one aspect, the present disclosure provides an apparatus for the preparation of chlorinated polyvinyl chloride (CPVC) comprising: i. a chamber for receiving polyvinyl chloride (PVC) and delivering CPVC; ii. at least one first inlet (6) leading into said chamber for introducing at least one fluid into said chamber (16); iii. at least one sparger (12) extending into said chamber for introducing fluid into said chamber (16); iv. at least one agitator fitted in said chamber; v. at least two baffles fitted in said chamber; and vi. a plurality of irradiation sources fitted to said baffles.

The baffles can be in the form of transparent tubes, approximately equidistant from the center of the chamber and almost parallel to the wall of the chamber. The irradiation source of the apparatus can be at least one selected from the group consisting of ultra violet (UV) lamps and light-emitting diodes (LEDs), having wavelength ranging from 250 nm to 550 nm, and may be fitted inside said transparent baffles. In accordance with another aspect, the present disclosure provides a process for the preparation of chlorinated CPVC using the apparatus disclosed herein above. The rate of reaction can range from 1.50 to 2.63 mole of (Cl)/h/kg of PVC.

BRIEF DESCRIPTION OF THE DRAWING The disclosure will now be described with reference to the accompanying non- limiting drawing, wherein:

Figure 1 illustrates the apparatus for the preparation of CPVC in accordance with one embodiment of the present disclosure wherein:

2 represents an agitator;

4 represents an outlet;

6 represents an inlet;

10 represents a thermocouple;

12 represents a sparger;

14 represents an impeller;

16 represents a chamber;

18 represents baffles; and

20 represents irradiation sources.

DETAILED DESCRIPTION

The process for the preparation of CPVC from PVC suspension, as provided in the present disclosure, is based on a gas-liquid- solid heterogeneous reaction. However, in such reactions, diffusion of chlorine into the pore of the solid PVC particles is a major rate limiting step. In order to overcome this impediment, the inventors of the present disclosure have provided an apparatus, having a particular construction of its components, which increases the overall rate of the reaction. The apparatus includes a chamber (16), at least one inlet (6) and a sparger (12), at least one agitator (2), at least two baffles (18) and a plurality of irradiation sources (20) fitted to said baffles (18). The chamber (16) of the present apparatus further includes at least one inlet for receiving the polyvinyl chloride (PVC) and at least one outlet (4) for delivering the chlorinated PVC once the reaction of photochlorination is complete. The chamber (16) includes at least one inlet (6) and sparger (12) for introducing at least one fluid into the chamberln accordance with the present disclosure, chlorine may be in gaseous or liquid form. In another embodiment, nitrogen is introduced in the chamber (16) via the sparger (12). The agitator (2) of the present disclosure is fitted centrally in said chamber (16) in order to achieve optimum mass transfer.

The apparatus characteristically employs at least two baffles (18), which can be in the form of transparent tubes, typically made of glass or polymeric material. In one exemplary embodiment, the baffles comprise two transparent tubes, fitted opposite each other in the chamber (16), approximately equidistant from the center of the chamber (16) and almost parallel to the wall of the chamber (16). The length of the tubes can be sufficient to cover from the top to the bottom wall of the chamber (16). In one embodiment, the length of the tube is equal to the length of the chamber (16). The presence of at least two tubes not only avoids vortex formation during agitation but also creates more frequent contact between the PVC particles and the chlorine radicals; thereby causing diffusion of chlorine into the pores of the solid PVC particles. Typically, these transparent tubes house a plurality of irradiation sources (20) along their length. The irradiation sources (20) have a wavelength ranging from 250 nm to 550 nm, and can be selected from the group consisting of ultra violet (UV) lamps and light-emitting diodes (LEDs). The transparent tubes, thus, function both as baffles (18) and as irradiation sources (20), which facilitates good contact between the photons generated from the irradiation sources, chlorine and the PVC particles (both outer surface and pore surface). This effects faster chlorine diffusion inside the pores, which in turn leads to a faster reaction rate and a greater yield in a small time period.

The chamber (16) of the present disclosure further comprises at least one pocket for holding a thermocouple (10). The chamber (16) also comprises at least one outlet (4) for discharging excess of chlorine and nitrogen from the chamber along with delivering CPVC. The outlet (4), in another embodiment, can also be used for charging PVC and/ or water.

In accordance with another aspect of the present disclosure, there is provided a process for the preparation of CPVC, which is carried out in the afore-stated apparatus. The process of the present disclosure includes reacting PVC with chlorine in the presence of a plurality of irradiation sources (20), under agitation at a speed ranging from 100 to 1600 rpm, for a time period ranging from 2 to 12 hours to obtain chlorinated polyvinyl chloride (CPVC).

The PVC used in the present process may be in a dried form or in slurry form. The dried PVC is characterized by 0.2 to 1 % loss on heating at 70 °C for 2 hours. The PVC in slurry form is prepared by admixing water and PVC and has a concentration ranging from 10 to 25 % w/v. Typically, the PVC is obtained by suspension polymerization of vinyl chloride monomer, having polymerization degree ranging from 200 to 15000, particle size ranging from 40 to 300 microns, surface area ranging from 1 to 3 m²/g, porosity ranging from of 0.02 to 0.40 mL/g and viscosity ranging from 0.9 to 1.2 dL/g.

In one embodiment, PVC is reacted with chlorine gas to yield CPVC. In another embodiment, PVC is reacted with liquid chlorine to yield CPVC. The irradiation sources (20) used in the present process can be selected from the group that includes ultra violet (UV) lamps and light-emitting diodes (LEDs) of wavelength ranging from 250 and 550 nm. The power input for these sources ranges from 0.01 to 0.04 Watt/ g of PVC.

Further, the present process is carried out at a temperature ranging from 40 to 90 °C and at a pressure ranging from 0.5 to 4 atmospheres. The tip speed of the agitator (2) can range from 0.5 m/s to 20 m/s.

The apparatus and process of the present disclosure bring about a faster rate of photo- chlorination in a much shorter time as compared to conventional apparatus, by increasing the probability of interactions between the photons, the reactive center of PVC and the chlorine radical, primarily by agitation or stirring of the PVC and creating obstacles (baffles) to the motion of the PVC. Moreover, by placing the irradiation source inside the chamber, the Reynolds number of the PVC in the slurry form remains in the range of 4000 to 3,00,000 which brings about accelerated photochlorination. Typically, the rate of reaction of the present process ranges from 1.50 to 2.63 mole of (Cl)/h/kg of PVC.

Flotation of CPVC during photochlorination of PVC in suspension form is another problem which results in uneven chlorination of PVC and creates difficulty during processing. This problem of floatation of CPVC is also overcome by the process described in the present disclosure. This is because, as the irradiation sources also act as baffles, the CPVC remains homogeneously dispersed so that no flotation occurs during the reaction. Furthermore, during the photochlorination of PVC using chlorine, HC1 gets generated as a byproduct and remains firmly inside the pores of the CPVC particles. The presence of HC1 in the final dried CPVC resin accelerates thermal degradation of CPVC as it is catalyzed by proton (H+) or any hydrated form of proton, making the CPVC thermally unstable. Therefore, it becomes necessary to reduce the amount of HC1 generated as well as to reduce the contact time between CPVC and HC1. As the present disclosure causes a reduction in the reaction time, the contact time between CPVC and HC1 reduces, which further reduces the diffusion of HC1 into the pores of CPVC particles.

The present disclosure will now be discussed in the light of the following non-limiting embodiments:

Process of preparation of CPVC according to the present disclosure

Example 1:

630 g of PVC (average particle size 147 microns, apparent bulk density 0.56 g/mL, inherent viscosity 0.93 and porosity 0.25 mL/g) was taken in 3500 mL water in a chamber (16) as described in Figure 1. For the first 5 minutes, this reaction mass was agitated at the speed of 200 rpm with the agitator tip speed at 0.875 m/s and agitator blade angle 45°. At the same time, nitrogen gas was purged inside the chamber through the slurry and the temperature was increased to reach 70 °C. The speed of rotation was then increased to 800 rpm and the agitator tip speed to 3.49 m/s. Nitrogen purging was continued for another 40 minutes in order to remove both air or oxygen from the chamber and the slurry, while the temperature was maintained at 70 °C. Nitrogen purging was then replaced by purging of chlorine gas, (at flow rate of 200 g/h, while maintaining the same conditions. Irradiation (450 nm LED) having 7W as the input power was switched on when the chamber and the slurry were found to be saturated with chlorine (checked by means of the ammonia torch at the exit of the chlorine outlet on the chamber) and this was counted as the reaction starting time. The pressure was maintained at 1 atmosphere throughout the process. Periodically, the rate of reaction was monitored by withdrawing a sample in every hour and titrating the mother liquor against 0.1 N NaOH. The reaction was stopped at 5 hours. The titer value corresponded to 67% (by weight) chlorinated PVC.

Irradiation (20) was stopped and chlorine purging was again replaced by nitrogen purging for an hour to expel out chlorine. Thereafter, the CPVC slurry was filtered and washed with water until the litmus paper showed a neutral pH. The filtered wet cake was dried at 55 °C under vacuum at <1.0 torr for 2 hours. The dried powder was neutralized using 0.0125 N Ca(OH)₂, 10 mL/g of CPVC for 10 minutes. Filtration and washing (25 mL/g CPVC dry basis) followed, which yielded CPVC that was dried under at 70 °C for 3 hours. The % chlorine content (by weight) was checked by weight increase in respect to PVC dry powder using the formula:

% Chlorine in CPVC = [102.9 - 46.2(A/B)] where:

A = weight of PVC in grams,

B = weight of CPVC obtained in grams.

The chorine present in 'A' grams PVC was 0.567A grams. The result was validated by ASTM F 442M - 99, oxygen flask method, the results of which remained within + 0.5 %. The thermal stability (sec) of the CPVC resin was measured by a conductivity meter using PVC thermomat (Metrohm 895), as per DIN53381, ISO 182-3 and it was found to be 612 sec.

This procedure was carried out for varying time periods (samples 1-5), and the results are tabulated in Table 1.

Example 2:

The experiment carried out in Example 1 was repeated, however, the agitation used in Example 2 was 400 rpm with the agitator tip speed of 1.745 m/s. The rest of the reaction parameters were the same as in Example 1. The reaction took 8 hours to reach 67 % chlorination. Moreover, the chlorination was uneven and flotation of CPVC occurred during reaction. The thermal stability was found to be 252 sec.

Example 3:

The experiment carried out in Example 1 was repeated, however, the agitation used in Example 2 was 600 rpm and the agitator tip speed was 2.625 m/s. The rest of the reaction parameters were the same as in Example 1. The reaction took 7 hours to reach 67 % chlorination and flotation of CPVC did not occur during chlorination.

Example 4:

The experiment carried out in Example 1 was repeated, however, the PVC amount was taken as 400 g. The rest of the reaction parameters were the same as in Example 1. The results obtained are demonstrated in Table 1.

Example 5:

The experiment carried out in Example 1 was repeated, however, just one irradiation source was used instead of two. The reaction time increased to 7 hours.

Example 6:

The experiment carried out in Example 1 was repeated, however, the irradiation source was kept above the slurry level. The reaction took more than 9 hours to achieve 67% by weight chlorination. The thermal stability was found to be 108 sec. Example 7:

The experiment carried out in Example 1 was repeated, however, the irradiation source was inserted only till the mid-level of the slurry. The reaction time increased to 7 hours (67% by weight chlorination). The reaction rate was found to be 1.23 mole Cl/h/Kg PVC and the thermal stability by conductivity 324 sec.

Example 8:

The experiment carried out in Example 1 was repeated, however, the irradiation source was removed from the transparent tube and kept outside the chamber, leaving the empty tube in position. The reaction took 7 hours to achieve 67% by weight chlorination.

The results obtained for examples 1-8 are tabulated in Table 1.

Table 1. Optimization of the process for the preparation of CPVC

6 800 3.45 9 67.3 0.92

7 800 3.45 7 67.3 1.23

8 800 3.45 7 67.3 1.23

Comparative Example 1: Time requirement

The experiment carried out in Example 1 was repeated, however, the light source was kept above the slurry level. After 9 hours, the reaction yield reached 66.8%.

When the apparatus of the present disclosure was used, the reaction yield reached 67.3% after just 4.5 hours (please refer to Example 4 of Table 1). It is thus clear that the process of the present is faster and gives better results in a less time period.

Comparative Example 2: Chlorine consumption

180 g of chlorine gas is used up for achieving 67% chlorination of 630 g of PVC. For effecting the same, the process of chlorination mentioned in Comparative Example 1 (keeping the light source above the slurry level) requires purging 1800 g of chlorine; whereas the process of chlorination mentioned in Example 1 (process of the present disclosure) requires purging of just 900 g of chlorine. Therefore, there is a 50% reduction in chlorine consumption in the process of the present disclosure.

Chlorine purged as in Comparative Example 1 = 9 h x 200 g (purge rate/ flow rate per hour) = 1800 g of CI

Chlorine purged according to the process of the present disclosure = 4.5 h x 200 g (purge rate/ flow rate per hour) = 900 g of CI

% reduction in chlorine consumption: 50 %

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The present disclosure provides an apparatus and a process for bringing about accelerated photochlorination of CPVC.

The apparatus uses irradiation sources (20) having input power of less than 5 Watt/g of PVC; thereby reducing the energy consumption.

Further, a reduction in the reaction time increases the number batch cycles, which makes the process economic.

Even further, floatation of CPVC, a common problem associated with its preparation, does not occur in the present process.

Still further, the chlorine consumption of the present process is 50% less than the prior art processes and consequently the hydrogen chloride formation is also less.

Furthermore, accelerated preparation of CPVC increases the stability of the resin. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention and the claims unless there is a statement in the specification to the contrary.

While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications in the process or compound or formulation or combination of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.

Claims

CLAIMS:

1. An apparatus for the preparation of chlorinated polyvinyl chloride (CPVC) comprising: i. a chamber (16) for receiving polyvinyl chloride (PVC) and delivering CPVC; ii. at least one first inlet (6) leading into said chamber for introducing at least one fluid into said chamber (16); iii. at least one sparger (12) extending into said chamber for introducing said fluid into said chamber (16); iv. at least one agitator (2) fitted in said chamber (16); v. at least two baffles (18) fitted in said chamber; and vi. a plurality of irradiation sources (20) fitted to said at least two baffles (18).

2. The apparatus as claimed in claim 1, wherein said agitator (2) is fitted centrally in said chamber (16).

3. The apparatus as claimed in claim 1, wherein said at least two baffles (18) are transparent tubes and said irradiation sources are fitted inside said baffles.

4. The apparatus as claimed in claim 1, wherein said baffles (18) are equidistant from the center of said chamber (16).

5. The apparatus as claimed in claim 1, wherein said baffles (18) are parallel to the wall of said chamber (16).

6. The apparatus as claimed in claim 1, wherein said irradiation source (20) is at least one selected from the group consisting of ultra violet (UV) lamps and light-emitting diodes (LEDs).

7. The apparatus as claimed in claim 1, wherein said irradiation source (20) has wavelength ranging from 250 nm to 550 nm.

8. The apparatus as claimed in claim 1, wherein said chamber (16) further comprises at least one pocket for holding a thermocouple (10).

9. The apparatus as claimed in claim 1, wherein said chamber (16) further comprises at least one first outlet (4) for discharging said fluid and delivering the CPVC.

10. A process for the preparation of CPVC comprising reacting PVC, in at least one form selected from the group consisting of PVC in completely dried form characterized by 0.2 to 1 % loss on heating at 70 °C for 2 hours and PVC in slurry form having concentration ranging from 10 to 25 % w/v, with chlorine in the presence of at least one irradiation source (20) selected from the group consisting of ultra violet (UV) lamps and light-emitting diodes (LEDs) of wavelength ranging from 250 and 550 nm and power ranging from 0.01 to 0.04 Watt/ g of PVC, under agitation (2) at a speed ranging from 100 to 1600 rpm, for a time period ranging from 2 to 12 hours to obtain CPVC.

11. The process as claimed in claim 10, wherein said PVC in slurry form is prepared by admixing water and PVC obtained by suspension polymerization of vinyl chloride monomer, having polymerization degree ranging from 200 to 15000, particle size ranging from 40 to 300 microns, surface area ranging from 1 to 3 m /g, porosity ranging from 0.02 to 0.40 mL/g and viscosity ranging from 0.9 to 1.2 dL/g.

12. The process as claimed in claim 10, wherein Reynolds number of said PVC in slurry form ranges from 4,000 to 3,00,000.

13. The process as claimed in claim 10, being carried out at a temperature ranging from 40 to 90 °C, pressure ranging from 0.5 to 4 atmospheres and agitator tip speed ranging from 0.5 m/s to 20 m/s.

14. The process as claimed in claim 10, being characterized by the rate of reaction ranging from 1.50 to 2.63 mole of (Cl)/h/kg of PVC.