DESC:FIELD
The present disclosure relates to a process for reducing amount of chloride in a chlorinated polymer.
DEFINITIONS
As used in the present disclosure, the following term is generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
Thermally stimulated conductivity (TSC) refers to the conductivity measured (in seconds) as a result of transport of charged carriers, electrons or holes that are thermally released from trapping states to a medium, solution, or excitation states.
BACKGROUND
Chlorinated polymers, such as chlorinated polyvinyl chloride (CPVC), are thermoplastic polymers used for high temperature applications. The thermal stability of the chlorinated polymers is a critical parameter for using in high temperature applications.
One of the reasons for lower thermal stability of the chlorinated polymers is the presence of residual chloride in the polymers. Chlorinated polymers with improved thermal stability have been obtained conventionally by taking measures at the synthesis stage, such as reducing the reaction time, minimizing the radiation exposure, using a minimum amount of chlorine in the reaction, maximizing utilization and incorporation of chlorine during chlorination, and using polyvinyl chloride (PVC) as a raw material. However, these strategies have low efficiency for the removal of chloride. Moreover, a substantial amount of chloride remains in the chlorinated polymers even after the synthesis.
There is, therefore, felt a need for an effective and economical process to reduce the amount of chloride in a chlorinated polymer.
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 a process for reducing the amount of chloride in a chlorinated polymer.
Another object of the present disclosure is to provide a process that improves the thermal stability of the chlorinated polymer without altering its inherent properties.
Still another object of the present disclosure is to provide a process that is effective and economical.
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 one aspect, the present disclosure provides a process for reducing amount of chloride in a chlorinated polymer. The process comprises adding an acid component to a chlorinated polymer and mixing thoroughly at a pre-determined temperature for a pre-determined time to obtain a first slurry. The first slurry is filtered to obtain a first filtrate and a first residue.
The first residue is neutralized by adding a neutralizing agent and mixing to obtain a second slurry. The second slurry is filtered to obtain a second filtrate and a second residue followed by washing the second residue with water to obtain washed second residue.
The washed second residue is treated by adding alkali metal hypochlorite and mixing to obtain a third slurry. The third slurry is filtered to obtain a third filtrate and a third residue followed by washing the third residue to obtain washed third residue. The washed third residue is dried at a temperature in the range of 50°C to 100°C to obtain a chlorinated polymer having reduced amount of chloride.
The mixing in the step of acid treatment is carried out at a speed in the range of 10 rpm to 3000 rpm. The pre-determined temperature is in the range of 20 °C to 80 °C. The pre-determined time is in the range of 5 minutes to 400 minutes.
The chlorinated polymer is at least one selected from the group consisting of chlorinated polyvinyl chloride (CPVC), polyvinylidene chloride, chlorinated butyl polymer, polychlorinated hydrocarbons, chlorinated polyester, chlorinated polyethylene, and chlorinated polypropylene.
The chlorinated polymer is in a pre-determined form selected from the group consisting of powder, granules and extrudates.
The water used for washing the second residue and/or for washing the third residue is demineralized water.
Typically, the acid component is an aqueous solution of hydrochloric acid, wherein the concentration of the aqueous hydrochloric acid solution is in the range of 0.5% to 7%.
The weight ratio of the chlorinated polymer to the acid component is in the range of 1:1 to 1:10.
The weight ratio of the chlorinated polymer to the neutralizing agent is in the range of 1:1 to 1:50.
The neutralizing agent is at least one compound selected from the group consisting of calcium hydroxide, sodium carbonate, ammonium carbonate, calcium carbonate and sodium citrate.
In an embodiment, the neutralizing agent is an aqueous solution of calcium hydroxide. The amount of calcium hydroxide in the aqueous solution is in the range of 20 wt.% to 30 wt.%.
The alkali metal hypochlorite is at least one compound selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite.
In an embodiment, the alkali metal hypochlorite is an aqueous solution of sodium hypochlorite. The concentration of the aqueous sodium hypochlorite solution is in the range of 0.05 to 0.5%.
The weight ratio of the powdered form of the chlorinated polymer to the alkali metal hypochlorite is in the range of 1:1 to 5:1.
Typically, the acid component in the first filtrate is recovered and further recycled to the step of acid treatment. Typically, unreacted alkali metal hypochlorite in the third filtrate is recovered and further recycled to the step of hypochlorite treatment.
In another aspect, the present disclosure provides a chlorinated polymer with reduced amount of chloride. The chlorinated polymer with reduced amount of chloride is characterized by thermally stimulated conductivity (TSC) in the range of 500 seconds to 800 seconds and inherent viscosity (IV) in the range of 0.75 dL/g to 0.85 dL/g.
DETAILED DESCRIPTION
The thermal stability of a chlorinated polymer is a critical parameter for employing the chlorinated polymer for high temperature applications. The conventional method for improving the thermal stability of the chlorinated polymers includes incorporation of stabilizers and/or additives. The stabilizers or additives tend to remain in the resultant chlorinated polymer, thereby affecting the quality of the polymer.
One of the causes for lower thermal stability of the chlorinated polymers is the presence of trace amount of hydrochloric acid trapped within the pores of the chlorinated polymer resin. The trapped hydrochloric acid accelerates acid catalyzed thermal degradation of the chlorinated polymer, upon heating.
The conventional methods prefer to reduce the amount of chloride in the polymer at the synthesis stage. However, such methods are not only ineffective and costly but also tend to negatively affect the inherent properties of the polymer.
In order to overcome the above limitations, the polymers can be subjected to post-synthesis treatment that can effectively remove the chloride and thereby lead to improved thermal stability of the chlorinated polymers without affecting other properties of the polymer.
In one aspect, the present disclosure provides a process for reducing amount of chloride present in a chlorinated polymer. The process is carried out in the steps described herein below.
In first step, an acid component is added to a chlorinated polymer and mixed thoroughly at a pre-determined temperature for a pre-determined time to obtain a first slurry.
Typically, the chlorinated polymer is at least one selected from the group consisting of chlorinated polyvinyl chloride (CPVC), polyvinylidene chloride, chlorinated butyl polymer, polychlorinated hydrocarbons, chlorinated polyester, chlorinated polyethylene, and chlorinated polypropylene. In an embodiment, the chlorinated polymer is chlorinated polyvinyl chloride (CPVC).
Typically, the chlorinated polymer is in a pre-determined form selected from the group consisting of powder, granules and extrudates. In an embodiment, the chlorinated polymer is in powder form.
Typically, the acid component is a mineral acid. In an embodiment, the acid component is an aqueous solution of hydrochloric acid. The concentration of the aqueous hydrochloric acid solution is in the range of 0.5% to 7%.
Typically, the mixing in the step of acid treatment is carried out at a speed in the range of 10 rpm to 3000 rpm.
Typically, the pre-determined temperature is in the range of 20 °C to 80 °C. In one embodiment, the pre-determined temperature is 25 °C. In another embodiment, the pre-determined temperature is 70 °C.
Typically, the pre-determined time is in the range of 5 minutes to 400 minutes. In an embodiment, the pre-determined time is 10 minutes. In another embodiment, the pre-determined time is 360 minutes.
The weight ratio of the chlorinated polymer to the acid component is in the range of 1:1 to 1:10.
The mixing of the chlorinated polymer with the acid component results in an interaction between hydrogen ions (H+) present in the chlorinated polymer and chloride ions (Cl-) present in the acid and vice versa, i.e., interaction between chloride ions (Cl-) present in the chlorinated polymer and hydrogen ions (H+) present in the acid.
The hydrogen chloride trapped within the pores of the chlorinated polymer moves towards the bulk solution due to the increased concentration of hydrochloric acid in the bulk solution, thereby reducing the amount of chloride in the chlorinated polymer.

In second step, the first slurry is filtered to obtain a first filtrate and a first residue.
In accordance with one embodiment of the present disclosure, the first residue comprises an acid treated chlorinated polymer.
In an embodiment, the acid component in the first filtrate is recovered and further recycled to the step of acid treatment.
In third step, the first residue is neutralized by adding a neutralizing agent and mixing to obtain a second slurry.
The neutralization of acid treated chlorinated polymer ensures the removal of the traces of acid present therein.
The mixing in the neutralization step is carried out for a time period in the range of 5 minutes to 15 minutes.
The weight ratio of the chlorinated polymer to the neutralizing agent is in the range of 1:1 to 1:50.
The neutralizing agent is at least one compound selected from the group consisting of calcium hydroxide, sodium carbonate, ammonium carbonate, calcium carbonate and sodium citrate.
Preferably, the neutralizing agent is an aqueous solution of calcium hydroxide wherein the amount of calcium hydroxide in the aqueous solution is in the range of 20 wt.% to 30 wt.%.
In fourth step, the second slurry is filtered to obtain a second filtrate and a second residue.
In accordance with one embodiment of the present disclosure, the second residue comprises a neutralized chlorinated polymer.
The second residue is washed with water to obtain washed second residue. In an embodiment, the water used for washing the second residue is demineralized water.
In fifth step, the washed second residue is treated by adding alkali metal hypochlorite and mixing to obtain a third slurry.
The mixing is carried out for a time period in the range of 5 minutes to 15 minutes.
The weight ratio of the chlorinated polymer to the alkali metal hypochlorite is in the range of 1:1 to 5:1.
Typically, the alkali metal hypochlorite is at least one compound selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite.
In an embodiment, the alkali metal hypochlorite is an aqueous solution of sodium hypochlorite. The concentration of the aqueous sodium hypochlorite solution is in the range of 0.05% to 0.5%.
In sixth step, the third slurry is filtered to obtain a third filtrate and a third residue. In accordance with one embodiment of the present disclosure, the third residue comprises a hypochlorite treated chlorinated polymer.
In an embodiment, the third residue is washed with water to obtain a washed third residue. In an embodiment, the water used for washing the third residue is demineralized water.
In an embodiment, unreacted alkali metal hypochlorite in the third filtrate is recovered and further recycled to the step of hypochlorite treatment.
In seventh step, the washed third residue is dried at a temperature in the range of 50°C to 100°C to obtain a chlorinated polymer having reduced amount of chloride.
The step of drying is carried out for a time period in the range of 60 minutes to 300 minutes. In an embodiment, the drying of the washed third residue is carried out for 180 minutes.
The reduction in the amount of chloride in the chlorinated polymer leads to improvement in the thermal stability of the polymer. The improvement in thermal stability is analyzed by measuring thermally stimulated conductivity (TSC). The TSC analysis involves heating of the chlorinated polymer thereby releasing HCl gas. The time required for the release of a pre-determined amount of HCl gas is a measure of the amount of chloride present in a sample. A reduction in amount of the chloride present in a treated sample is indicated by an increase in the time taken for release of the predetermined amount of HCl from the treated sample as compared to the time required for the starting material. A decrease in the amount of chloride present in a treated sample indicates improvement in the thermal stability of the treated sample.
In another aspect, the present disclosure provides a chlorinated polymer with reduced amount of chloride, obtained by the process of the present disclosure. The chlorinated polymer with reduced amount of chloride is characterized by thermally stimulated conductivity (TSC) in the range of 500 seconds to 800 seconds, and inherent viscosity (IV) in the range of 0.75 dL/g to 0.85 dL/g. Other properties such as appearance or whiteness are also not affected.
The present disclosure provides a chlorinated polymer having reduced amount of chloride and improved thermal stability without affecting its inherent properties like inherent viscosity (IV) and whiteness. The process avoids use of any additional stabilizers and/or additives.
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. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
Experiment 1: (Acid treatment of CPVC with 1% HCl at 25 °C for 10 minutes)
An aqueous solution of 1% hydrochloric acid (500 ml) was added to powdered form of chlorinated polyvinyl chloride (CPVC) (100 g) and mixed thoroughly at 25 °C for 30 minutes at 300 rpm speed to obtain a first slurry. The first slurry was filtered to obtain a first residue and a first filtrate. An aqueous solution of 0.0125 M calcium hydroxide (2 litres) was added to the first residue and mixed for 10 minutes for neutralizing the residue, thereby obtaining a second slurry. The second slurry was filtered to obtain a second filtrate and a second residue. The second residue was washed with demineralized water for three times. To the washed second residue, an aqueous solution of 0.1% sodium hypochlorite (NaOCl) (25 mL) was added and mixed for 10 minutes to obtain a third slurry. The third slurry was filtered to obtain a third filtrate and a third residue. The third residue was further washed with water for three times. The washed residue, so obtained was dried at 70°C for 180 minutes to obtain a chlorinated polymer having reduced amount of chloride.
The sample of the chlorinated polymer as obtained from Experiment 1 was subjected to measurement of properties such as thermally stimulated conductivity (TSC), intrinsic viscosity (IV) and appearance (whiteness) as summarized in Table 1.
TSC was measured in Metrohm instrument, 895 PVC thermomat using StabNet software. The method is as per DIN 53381 Part 1 or ISO 182 Part 3.
TSC value is directly related to the thermal stability of the chlorinated polymer. The chlorinated polymer CPVC releases HCl gas upon heating. The released HCl gas is transferred by a stream of nitrogen into a measuring cell filled with specific amount of distilled water, where the conductivity of this solution is measured. The thermal stability of the chlorinated polymer is defined as the time that elapses until HCl is released, and is determined by measuring the change in conductivity of the solution containing HCl. The thermal stability is expressed in terms of the time (in seconds) corresponding to conductivity difference of 50 µS/cm in the measuring vessel.
The inherent viscosity was measured as per ASTM D1243-95. For the measurements of appearance or whiteness, 30 gm dry powder sample was taken in 2 inch cubical cell, wherein the appearance was compared with starting reference sample of the experiment. The visual appearance was reported in terms of whiteness.
Experiments 2-3: (Acid treatment of CPVC with 1 % HCl at 25 °C for 60 and 360 minutes)
Experiments 2 and 3 were carried out in a similar manner as described in Experiment 1 except that the mixing in the acid treatment step (mixing of the 1% aqueous hydrochloric acid solution with CPVC polymer) was carried out for 60 minutes and 360 minutes respectively.
The samples of the chlorinated polymer as obtained from Experiments 2 and 3 were subjected to measurement of properties such as thermally stimulated conductivity (TSC), intrinsic viscosity (IV) and appearance (whiteness).
The results are summarized below in Table 1.
Table-1:
Experiment No. Sample (acid treatment at 25 °C) TSC (s)*
(standard deviation (SD)) = +/- 50 IV** (dL/g)
SD = +/- 0.01 Appearance
Powdered CPVC (starting material) 600 0.82 white
1 1% HCl – 30 mins 612 0.82 white
2 1% HCl – 60 mins 630 0.82 white
3 1% HCl-360 mins 648 0.83 white
(* Thermally stimulated conductivity (TSC),
** Inherent viscosity (IV))
From Table-1, it is observed that the TSC of the chlorinated polymer obtained after treating the starting material (powdered CPVC) with 1% HCl for 30, 60 and 360 minutes is higher as compared to that of the starting CPVC material. Therefore, it is concluded that the thermal stability of the chlorinated polymer improved after treating the starting material with 1% HCl.
From Table-1, it is also observed that the inherent properties like inherent viscosity and appearance (whiteness) of the chlorinated polymer and the starting material remain approximately the same (i.e., there is no significant deviation in the values of the inherent properties).
Experiments 4 to 6: (Acid treatment of CPVC with 1 % HCl at 70 °C for 10-360 minutes)
Experiments 4-6 were carried out in a similar manner as described in Experiment 1 except that the step of acid treatment (i.e. mixing of the aqueous solution of 1% hydrochloric acid with CPVC polymer) was carried at 70 °C instead of 25 °C. Experiments 4-6 were carried out for 10 minutes, 30 minutes and 60 minutes respectively.
The samples of the chlorinated polymer as obtained from Experiments 4-6 were subjected to measurement of thermally stimulated conductivity (TSC), intrinsic viscosity (IV) and appearance (whiteness). The results are summarized below in Table 2.
Table-2:
Experiment No. Sample (acid treatment at 70 °C) TSC (s)
SD = +/- 50 IV (dL/g)
SD = +/- 0.01 Appearance
Powdered CPVC (starting material) 600 0.82 white
4 1% HCl – 10 mins 672 0.82 white
5 1% HCl – 30 mins 708 0.83 white
6 1% HCl – 60 mins 732 0.83 white

From Table-2, it is observed that the TSC of the chlorinated polymer obtained after treating the starting CPVC polymer with 1% HCl solution for 10 minutes to 60 minutes are higher as compared to that of the starting material.
Therefore, it is concluded that the thermal stability of the chlorinated polymer has increased after treating the starting CPVC material with 1% HCl solution.
From Table-2, it is also observed that the inherent properties like inherent viscosity (IV) and appearance (whiteness) of the chlorinated polymer and the starting material remain approximately same (i.e., there is no significant deviation in the values of the inherent properties). Therefore, it is concluded that the process of the present disclosure does not significantly alter the inherent properties of CPVC.
Further, from Table-1 and Table-2, it is observed that the TSC of the chlorinated polymer obtained after treating the starting CPVC material with 1% HCl solution at 70°C are comparatively higher than that of the TSC of the chlorinated polymer obtained after treating the starting material with 1% HCl solution at ambient temperature (25 °C). Therefore, with respect to this, it is concluded that the thermal stability of the chlorinated polymer obtained after treating the starting CPVC material with 1% HCl solution at 70°C is comparatively higher than that of the chlorinated polymer obtained after treating the starting CPVC material at ambient temperature (25 °C).
Experiment 7: (Acid treatment of CPVC at 25 °C; Sample preparation without the steps of neutralization and hypochlorite treatment)
Experiment 7 was carried out in a similar manner as described in Experiment 1 except that the acid treatment step was carried out at 25 °C for 360 minutes and the steps of neutralization, post filtering and hypochlorite treatment were not performed. The sample was additionally washed with demineralized water before drying the final sample.
Experiment 8: (Acid treatment of CPVC at 70 °C; Sample preparation without the steps of neutralization and hypochlorite treatment)
Experiment 8 was carried out in a similar manner as described in Experiment 1 except that the acid treatment step was carried out at 70 °C for 360 minutes and the steps of neutralization, post filtering and hypochlorite treatment were not performed. The sample was additionally washed with demineralized water before drying the final sample.
The samples of the chlorinated polymer as obtained from experiments 7 and 8 were subjected to measurement of TSC, intrinsic viscosity (IV) and appearance (whiteness). The results are summarized below in Table 3.
Table-3:
Experiment No. Experiment conditions TSC (s)
SD = +/- 50 IV (dL/g)
SD= +/- 0.01 WI
7 1% HCl - 360 min @ 25 °C followed by washing with demineralized water 564 0.827 white
8 1% HCl - 360 min @ 70°C followed by washing with demineralized water 660 0.836 white

From experiment 3 (Table 1) and experiment 7 (Table 3), it is observed that the TSC value of the chlorinated polymer (CPVC) obtained in experiment 7 (without the steps of neutralization, post filtering and washing) is less as compared to the chlorinated polymer (CPVC) as obtained in experiment 3. Therefore, it is concluded that the steps of neutralization and hypochlorite treatment are important and the absence of these steps negatively affects the thermal stability of the chlorinated polymer.
Experiments 9 to 12 (Acid treatment with 6% HCl at 25 °C for 10-360 minutes):
Experiments 9-12 were carried out in a similar manner as described in Experiment 1 except that 6% HCl solution was used instead of 1% HCl solution and the step of acid treatment (i.e. mixing of the aqueous solution of hydrochloric acid with CPVC polymer). Experiments 9-12 were carried out for 30 minutes, 120 minutes, 240 minutes and 360 minutes respectively.
The samples of the chlorinated polymer as obtained from Experiments 9-12 were subjected to measurement of TSC, intrinsic viscosity (IV) and appearance (whiteness). The results are summarized below in Table 4.
Table-4:
Experiment No. Sample (acid treatment at 25 °C) TSC (s)
(standard deviation = +/- 50 IV (dL/g)
(standard deviation = +/- 0.01 Appearance
Powdered CPVC (starting material) 600 0.82 white
9 6% HCl – 30 mins 618 0.81 white
10 6% HCl - 120 mins 627 0.82 white
11 6% HCl - 240 mins 669 0.82 white
12 6% HCl - 360 mins 675 0.82 white

From Table-4, it is observed that the TSC of the chlorinated polymer obtained after treating CPVC polymer with 6% HCl solution for 10 minutes to 360 minutes are higher as compared to TSC of the starting CPVC material. Therefore, with respect to this, it is concluded that the thermal stability of the chlorinated polymer improved on being treated with 6% HCl solution.
In view of the above discussion, it is concluded that the thermal stability of the chlorinated polymer obtained after treating the starting material with 6% HCl solution at ambient temperature (25 °C) is comparatively higher than that of the chlorinated polymer obtained after treating the starting material with 1% HCl solution at ambient temperature (25 °C).
From Table-4, it is also observed that the inherent properties like inherent viscosity and appearance (whiteness) of the chlorinated polymer and the starting material remain approximately same (i.e., there is no significant deviation in the values of the inherent properties).
Experiments 13 to 16 (Acid treatment with 6% HCl at 70 °C for 10-360 minutes):
Experiments 13-16 were carried out in a similar manner as described in Experiment 1 except that 6% HCl solution was used instead of 1% HCl solution and the step of acid treatment (i.e. mixing of the aqueous solution of hydrochloric acid with CPVC polymer) was carried out at 70 °C instead of 25 °C for 30 minutes, 60 minutes, 120 minutes and 240 minutes respectively.
The samples of the chlorinated polymer as obtained from Experiments 13-16 were subjected to measurement of TSC, intrinsic viscosity (IV) and (appearance) whiteness. The results are summarized below in Table 5.
Table-5:
Experiment No. Sample (acid treatment at 70 °C) TSC (s)
SD = +/- 50 IV (dL/g)
SD = +/- 0.01 Appearance
Powdered CPVC (starting material) 600 0.82 white
13 6% HCl – 30 mins 642 0.82 white
14 6% HC l – 60 mins 651 0.81 white
15 6% HCl - 120 mins 678 0.81 white
16 6% HCl - 240 mins 750 0.81 white
From Table-5, it is observed that the TSC of the chlorinated polymer obtained after treating the starting CPVC polymer with 6% HCl solution for 10 minutes to 360 minutes are higher as compared to that of the starting material. Therefore, with respect to this, it is concluded that the thermal stability of the chlorinated polymer improved on being treated with 6% HCl solution.
From Table-5, it is also observed that the inherent properties like inherent viscosity and whiteness of the chlorinated polymer and the starting material remain approximately the same (i.e., there is no significant deviation in the values of the inherent properties). Therefore, it is concluded that the process of the present disclosure does not significantly alter the inherent properties of CPVC.
Furthermore, in view of the above discussions, it is concluded that the thermal stability of the chlorinated polymer obtained after treating the starting material with 6% HCl solution at ambient temperature or 70°C (Tables 4 and 5) is comparatively higher than that of the chlorinated polymer obtained after treating the starting material with 1% HCl solution at ambient temperature or 70°C (Tables 1 and 2).
The process of the present disclosure reduces the amount of chloride in the chlorinated polymer and significantly improves the thermal stability without altering the inherent properties of the polymer. Moreover, the process is effective and economical.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process that:
• reduces the amount of chloride in a chlorinated polymer;
• improves the thermal stability of the chlorinated polymer without altering its inherent properties; and
• is efficient and economical.
The disclosure has been 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 foregoing description of the specific embodiments so fully revealed 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.
,CLAIMS:WE CLAIM:
1. A process for reducing amount of chloride in a chlorinated polymer; the process comprising the following steps:
(a) adding an acid component to a chlorinated polymer and mixing thoroughly at a pre-determined temperature for a pre-determined time to obtain a first slurry;
(b) filtering said first slurry to obtain a first filtrate and a first residue;
(c) neutralizing said first residue by adding a neutralizing agent, and mixing to obtain a second slurry;
(d) filtering said second slurry to obtain a second filtrate and a second residue, followed by washing said second residue with water to obtain washed second residue;
(e) treating said washed second residue by adding alkali metal hypochlorite, and mixing to obtain a third slurry;
(f) filtering said third slurry to obtain a third filtrate and a third residue, followed by washing said third residue with water to obtain washed third residue; and
(g) drying said washed third residue at a temperature in the range of 50°C to 100°C to obtain a chlorinated polymer having reduced amount of chloride.
2. The process as claimed in claim 1, wherein the mixing in the step (a) of acid treatment is carried out at a speed in the range of 10 rpm to 3000 rpm.
3. The process as claimed in claim 1, wherein the pre-determined temperature is in the range of 20 °C to 80 °C.
4. The process as claimed in claim 1, wherein the pre-determined time is in the range of 5 minutes to 400 minutes.
5. The process as claimed in claim 1, wherein the chlorinated polymer is at least one selected from the group consisting of chlorinated polyvinyl chloride (CPVC), polyvinylidene chloride, chlorinated butyl polymer, polychlorinated hydrocarbons, chlorinated polyester, chlorinated polyethylene, and chlorinated polypropylene.
6. The process as claimed in claim 1, wherein the chlorinated polymer is in a pre-determined form selected from the group consisting of powder, granules and extrudates.
7. The process as claimed in claim 1, wherein the water used for washing the second residue in step (d) and/or washing the third residue in step (f) is demineralized water.
8. The process as claimed in claim 1, wherein the acid component is an aqueous solution of hydrochloric acid, wherein the concentration of the aqueous hydrochloric acid solution is in the range of 0.5% to 7%.
9. The process as claimed in claim 1, wherein the weight ratio of the chlorinated polymer to the acid component is in the range of 1:1 to 1:10.
10. The process as claimed in claim 1, wherein the weight ratio of the chlorinated polymer to the neutralizing agent is in the range of 1:1 to 1:50.
11. The process as claimed in claim 1, wherein the neutralizing agent is at least one compound selected from the group consisting of calcium hydroxide, sodium carbonate, ammonium carbonate, calcium carbonate and sodium citrate.
12. The process as claimed in claim 1, wherein the neutralizing agent is an aqueous solution of calcium hydroxide, wherein the amount of calcium hydroxide in the aqueous solution is in the range of 20 wt.% to 30 wt.%.
13. The process as claimed in claim 1, wherein the alkali metal hypochlorite is at least one compound selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite.
14. The process as claimed in claim 1, wherein the alkali metal hypochlorite is an aqueous solution of sodium hypochlorite, wherein the concentration of the aqueous sodium hypochlorite solution is in the range of 0.05% to 0.5%.
15. The process as claimed in claim 1, wherein the weight ratio of the chlorinated polymer to the alkali metal hypochlorite is in the range of 1:1 to 5:1.
16. The process as claimed in claim 1, wherein the acid component in the first filtrate is recovered and further recycled to the step (a) of acid treatment.
17. The process as claimed in claim 1, wherein unreacted alkali metal hypochlorite in the third filtrate is recovered and further recycled to the step (e) of hypochlorite treatment.
18. A chlorinated polymer with reduced amount of chloride prepared by the process as claimed in claim 1, wherein the chlorinated polymer with reduced amount of chloride is characterized by thermally stimulated conductivity (TSC) in the range of 500 seconds to 800 seconds and inherent viscosity (IV) in the range of 0.75 dL/g to 0.85 dL/g.