WO2016075591A1

WO2016075591A1 - Apparatus and process for chlorination of polyvinyl chloride

Info

Publication number: WO2016075591A1
Application number: PCT/IB2015/058517
Authority: WO
Inventors: Ninad Deepak INGLE; Pradeep Paresh KAPADIA; Pradip Munshi; Ajit Behari Mathur; Raksh Vir Jasra
Original assignee: Reliance Industries Limited
Priority date: 2014-11-11
Filing date: 2015-11-04
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, at least one sparger and at least one agitator fitted in the chamber and at least one 5 monochromatic radiation source located outside the chamber to bring about photochlorination of polyvinyl chloride. The process includes reacting polyvinyl chloride (PVC) with chlorine in the presence of monochromatic radiation source of wavelength ranging from 300 nm to 450 nm, under agitation at a speed ranging from 100 rpm to 1600 rpm, for a time period ranging from 2 hours to 12 hours, to 10 obtain CPVC.

Description

CHLORINATED POLYVINYL CHLORIDE

FIELD

The present disclosure relates to an apparatus and a process for preparing chlorinated polyvinyl chloride (CPVC). BACKGROUND

Polyvinyl chloride (PVC) has a low softening temperature and hence, has many limitations in the field of its application. To overcome the limitations and improve the low softening point of PVC, chlorination of polyvinyl chloride is carried out to obtain chlorinated polyvinyl chloride (CPVC). Chlorinated polyvinyl chloride (CPVC) is more rigid than PVC and also more thermally resistant. Due to its rigidity and higher thermal resistant properties, CPVC has more applications than PVC. However, high content of chlorine in the CPVC confers, other characteristics that are not desirable. Hence, CPVC has to be prepared with the optimum percentage of chlorine. Previously known methods of chlorination include, bubbling chlorine gas into an organic solvent solution or suspension of PVC, contacting chlorine gas directly with solid PVC powder, bubbling chlorine gas into an aqueous suspension of PVC, photo-chlorination of PVC in the presence of irradiation of light and the like. Photo-chlorination of PVC 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 the diffusion of chlorine into the PVC pores determines the rate of the reaction, efforts have been directed towards increasing the rate of reaction by increasing chlorine penetration. 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 US4412898. Elevating the temperature to enhance the rate of the reaction is also known in the art. The rate of the reaction can also be controlled by supplying controlled Ultraviolet radiation (UV) in the reactor as suggested in US4049517. US3328371 suggests the use of additives such as chlorinating agents (SO₂CI₂) and swelling agents in order to further increase the rate of reaction.

US6197895 recites adding organic peroxide compounds to the PVC suspension in order to increase the rate of chlorination.

However, most of the afore-stated processes necessitate the use of raw materials having specific physical properties and entail the use of specific reagents and additives which make the overall process expensive. Furthermore, the rate of the reaction is also not as per the desired practical standard.

The inventors of the present disclosure, therefore, envisaged an apparatus and a process to carry out photo-chlorination of PVC at an increased rate and also mitigate the other drawbacks associated with the known processes.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.

It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

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

Another object of the present disclosure is to provide a process for the preparation of chlorinated polyvinyl chloride (CPVC). Still another object of the present disclosure is to provide a process for the preparation of chlorinated polyvinyl chloride, which is simple and rapid. 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 The present disclosure provides an apparatus and a process for the preparation of CPVC. The apparatus comprises a chamber for receiving PVC and delivering CPVC; at least one inlet leading into said chamber for introducing at least one reactant into said chamber; at least one sparger extending into said chamber through said inlet for introducing at least one reactant into said chamber; at least one agitator and at least one monochromatic light source located outside the chamber, at a distance ranging from 1 cm to 20 cm from the surface of PVC. Typically, the monochromatic light source can be a LASER.

The process of the present disclosure includes reacting PVC, with chlorine in the presence of at least one monochromatic light source having a wavelength ranging from 300 nm to 450 nm at an agitation speed ranging from 100 rpm to 1600 rpm, for a time period ranging from 2 hours to 12 hours to obtain CPVC. The PVC is 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 25 to 30% w/v. Typically, said monochromatic light source is a LASER.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING

The disclosure will now be described with reference to the accompanying non- limiting drawing, wherein:

Figure 1 illustrates an apparatus for the preparation of CPVC in accordance with one embodiment of the present disclosure. DETAILED DESCRIPTION

The disclosure will now be described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration. The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following 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 following 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 has 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. The present disclosure, in one aspect, provides an apparatus for the preparation of CPVC. The apparatus includes, but is not limited to a chamber, at least one inlet, at least one outlet, at least one sparger, at least one agitator and at least one monochromatic light source as illustrated in Figure 1. In one embodiment, the chamber (c) is a round bottom flask with a stopper (b) having multiple ports.

Referring to Figure 1, the chamber (c) of the apparatus for preparing CPVC is transparent and is adapted to receive PVC (f) and deliver CPVC. At least one inlet (i) leading into the chamber (c), through the stopper (b), is adapted to introduce at least one reactant and an inert gas into the chamber through a sparger, and at least one outlet (a) for discharging the fluids and for recovering the formed CPVC from the chamber. The sparger can extend through the inlet and introduce the inert gas into the said chamber. At least one agitator (e) is present in the chamber for the purpose of agitation. The light source (g) in the apparatus for preparing CPVC in accordance with the present disclosure includes at least one monochromatic light source having a wavelength ranging from 300 nm to 450 nm that is located outside the chamber. The wavelength of the light is adjusted using the controller (h) attached to the light source. The assembly is kept in a water bath (d), which is maintained at a temperature in the range of 65 °C to 75 °C.

In an embodiment of the present disclosure, the light source is a LASER. Typically, the light source is located at a distance ranging from 1cm to 20 cm from the material being chlorinated i.e. PVC slurry, from any side of the chamber. Typically, the agitation is carried out using a magnetic stirrer.

The chamber (c) of the apparatus for preparing CPVC in accordance with the present disclosure can also include at least one pocket for holding a thermocouple and at least one outlet (a) for delivering the CPVC and for discharging fluids.

In accordance with another aspect, the present disclosure provides a process for the preparing CPVC from PVC. In the process, PVC is reacted with chlorine in the presence of at least one monochromatic light (g) having a wavelength ranging from 300 nm to 450 nm and at an agitation speed ranging from 100 rpm to 1600 rpm, for a time period ranging from 2 hours to 12 hours to obtain CPVC. The PVC used in the process of the present disclosure is in at least one form selected from the group consisting of PVC in a completely dried form and PVC in slurry form. Completely dried PVC form is characterized by 0.2 % to 1 % loss on heating at 70 °C for 2 hours. PVC in slurry form is characterized by having a PVC concentration ranging from 25 to 30% w/v and Reynolds number ranging from 1 x 10³ to 3 x 10⁶. (Reynolds number is a dimensionless number used in fluid mechanics to indicate whether fluid flow past a body or in a duct is steady or turbulent). Typically, the PVC slurry is prepared by admixing water and PVC obtained by suspension polymerization of vinyl chloride monomer, having a polymerization degree ranging from 30000 to 60000, particle size ranging from 135 microns to 170 microns, porosity ranging from 0.18 to 0.36 ml/g and viscosity ranging from 0.60 dl/g to 1 dl/g.

Monochromatic light source (h) used in the process of the present disclosure can be LASER. The light source is kept outside the reaction vessel, at a distance ranging from 1 cm to 20 cm from the sides of the chamber (c) by ensuring that the light is able to irradiate to the sample efficiently, without any blockage. In one embodiment the light source is provided on the walls of the chamber. The monochromatic light can be selected from a light source having a wavelength ranging from 300 nm to 450 nm. The monochromatic light consists of maximum radiation of a single wavelength. All the light waves are also in the same phase, having maximum possibility of population inversion. This makes the light more powerful with better penetrating ability into the solid surface than conventional light. Hence, the major advantage of using LASER (as a monochromatic light source) in the preparation of chlorinated polyvinyl chloride is achieving comparatively better chlorination in a shorter time period.

The reaction mixture is stirred in an agitation chamber where the speed of the agitator ranges from 100 rpm to 1600 rpm. The stirring time of the reaction mixture ranges from 2 hours to 12 hours to obtain CPVC. The process of the present disclosure is carried out at a temperature ranging from 40 °C to 90 °C, at a pressure ranging from 0.5 to 4 atmospheres and at an agitator tip speed ranging from 0.5 m/s to 20 m/s. The rate of reaction ranges from 0.22 - 0.37 Kmole (CI²) /g (PVC). h² Hydrogen chloride (HC1) is produced during the chlorination of PVC and is monitored during the reaction. The chlorination degree (% of chlorination) is calculated from the hydrogen chloride concentration in the reaction solution. The reaction is stopped when chlorination of PVC reaches to about 65-67%.

The reaction vessel is allowed to cool and the remaining chlorine gas is purged with nitrogen gas. After purging the remaining chlorine gas, the slurry is discharged from the reaction vessel. In one embodiment one outlet is at the bottom of the chamber and the slurry is discharged from the bottom of the reaction vessel. The CPVC polymer obtained is filtered, and washed with de- mineralized water till it turns neutral. The neutralized CPVC polymer is dried to obtain CPVC in powder form which is further analyzed for its physical properties such as intrinsic viscosity and thermal stability.

The advantages associated with the use of stimulated emission (LASER), are presented herein below. The power of light of a specific wavelength can be amplified by stimulated emission. Such light has more power than conventional light. Therefore, photo-induced fission of a chemical bond generates free radicals in a shorter time period as compared to normal light having a similar wavelength and less energy. Moreover, the power of stimulated radiation causes chlorine gas to penetrate deeper into the solid materials. Therefore, chlorination of PVC occurs at a much deeper level in the solid PVC by interaction with diffused chlorine molecule into the pore, which in the presence of light generates chlorine radical. Furthermore, depending upon the nature of the molecule used for radiation, the wavelength can be changed. This makes the stimulated radiation desirable for chlorination. The present disclosure is further illustrated herein below with the help of the following experiments. The experiments 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 embodiments herein. The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/ commercial scale.

Experimental Details:

Experiment 1: Process of preparation of CPVC in accordance with the present disclosure

28% PVC slurry was prepared in a 100 ml glass flask and was kept under continuous agitation with the help of a magnetic bar arrangement. Continuous LASER source having a wavelength of 445 nm was placed at a distance of 5 cm from the surface of the flask as an irradiation source. The flask was kept in a water bath and the temperature of the water bath was set at 70 °C and nitrogen purging was done on a continuous basis for 15 minutes to remove air or oxygen from the reaction flask. After 15 minutes, the temperature of the reaction flask reached 70 °C, after which nitrogen purging was stopped and chlorine was purged through the slurry. The LASER was turned on, when the reactor and slurry were found to be saturated with chlorine. Periodical rate was monitored with respect to the hydrogen chloride (HC1) produced during the reaction. The reaction was stopped when chlorination reached 65-67%. The resin obtained was then filtered and washed with de-mineralized water till it turned neutral. The neutralized resin was dried to obtain CPVC resin which was further analyzed for critical properties such as intrinsic viscosity and thermal stability. Experiment 2 and 3: Comparative Example

Similar experiments, as described in experiment 1, were carried out by varying the amount PVC, and by varying the monochromatic light source. In comparative experiments 7.7 g of K67 PVC with porosity 0.26 mL/g was taken in 100 mL glass vessel and 42 mL water was added thus an aqueous PVC slurry of 15% (by wt) was made in the apparatus described in Figure 1.

With the above PVC concentration, experiment 2 was conducted using LASER irradiation as a monochromatic light source and experiment 3 was conducted using LED (465 nm) irradiation as a monochromatic light source.

The results obtained for different time intervals (1 hour, 2 hour, 3 hour and 4 hour) according to the process of the present disclosure are summarized in table 1.

Table 1

It can be clearly seen from Table 1 that higher chlorination is obtained when LASER is used as a light source as compared to when LED is used as a light source. TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:

The process of the present disclosure uses stimulated radiation (LASER) that has a more penetrating ability into a solid surface than conventional light.

Chlorination of solid polymer particle by using stimulated radiation gives deep penetration of chlorine into the solid pore causing maximum chlorination in a shorter time period as compared to conventional light source.

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 disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

1. An apparatus for the preparation of chlorinated polyvinyl chloride (CPVC), said apparatus comprising: i. a chamber having transparent walls for receiving polyvinyl chloride (PVC) and carrying out a reaction of chlorination of the received PVC and delivering CPVC; ii. at least one inlet leading into said chamber for introducing at least one reactant into said chamber; iii. at least one sparger extending into said chamber for introducing said reactant into said chamber; iv. at least one agitator; and v. at least one monochromatic light source located outside said chamber, at a distance ranging from 1 cm to 20 cm from said PVC .

2. The apparatus as claimed in claim 1, wherein said monochromatic light source has a wavelength ranging from 300 nm to 450 nm and is a LASER.

3. The apparatus as claimed in claim 1, wherein said chamber further comprises at least one pocket for holding a thermocouple.

4. The apparatus as claimed in claim 1, wherein said chamber further comprises at least one outlet for delivering the CPVC.

5. A process for the preparation of CPVC comprising reacting PVC with chlorine in the presence of at least one monochromatic light having a wavelength ranging from 300 nm to 450 nm at an agitation speed ranging from 100 rpm to 1600 rpm, for a time period ranging from 2 hours to 12 hours to obtain CPVC; wherein said monochromatic light source is a

LASER.

6. The process as claimed in claim 5, wherein said PVC is at least one 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 25 to 30 % w/v.

7. The process as claimed in claim 6, wherein said PVC in slurry form is prepared by admixing water and PVC obtained by suspension polymerization of vinyl chloride monomer, having a polymerization degree ranging from 30000 to 60000, particle size ranging from 135 microns to 170 microns, porosity ranging from 0.18 to 0.36 ml/g and viscosity ranging from 0.60 to 1 dl/g.

8. The process as claimed in claim 6, wherein the Reynolds number of said

PVC in slurry form ranges from 1 x 10³ to 3 x 10⁶.

9. The process as claimed in claim 5, wherein said process is carried out at a temperature ranging from 40 °C to 90 °C, pressure ranging from 0.5 atmosphere to 4 atmosphere and agitator tip speed ranging from 0.5 m s to 20 m s.

10. The process as claimed in claim 5, wherein said process is characterized

2 2 by the rate of reaction ranging from 0.22 - 0.37 Kmole(Cr)/g(PVC).h"