Claims:WE CLAIM
1. A process for preparing a chlorinated polymer by chlorination of a polymer, the process comprising:
(a) chlorinating the polymer with a chlorinating agent, in the presence of aqueous hydrochloric acid, under exposure to light radiation to obtain a product mixture comprising crude chlorinated polymer, and aqueous hydrochloric acid;
(b) filtering the product mixture to obtain a residue comprising crude chlorinated polymer and mother liquor comprising aqueous hydrochloric acid;
(c) partially dehydrating the residue by washing with a fluid medium to obtain a wet cake of crude chlorinated polymer containing less than 30% moisture;
(d) drying the wet cake under reduced pressure to obtain a dry mass of crude chlorinated polymer;
(e) neutralizing the dry mass of crude chlorinated polymer with a base to obtain neutralized chlorinated polymer;
(f) treating the neutralized chlorinated polymer with sodium hypochlorite solution to obtain a hypochlorite treated chlorinated polymer; and
(g) drying the hypochlorite treated chlorinated polymer to obtain chlorinated polymer.
2. The process as claimed in claim 1, wherein the polymer is at least one selected from the group consisting of polyvinyl chloride, polyethylene and polyvinylidene chloride.
3. The process as claimed in claim 1, wherein the polymer is in at least one form selected from the group consisting of powder, granules, fibres and mixture thereof; wherein the polymer has porosity in the range of 0.19 mL/g to 0.29 mL/g.
4. The process as claimed in claim 1, wherein the chlorinating agent is at least one selected from the group consisting of chlorine, and SO2Cl2; wherein the weight ratio of the chlorinating agent and the polymer is in the range of 5:1 to 1:5.
5. The process as claimed in claim 1, wherein the light radiations used in the step of chlorination have wavelength in the range of 400 to 700 nm and intensity in the range of 2 Watt/Kg of the polymer to 100 Watt/Kg of the polymer ; wherein the light radiations are emitted by a source of light radiation selected from the group consisting of Light Emitting Diode (LED), Light Amplification by Stimulated Emission of Radiation (LASER), and filament based lamp.
6. The process as claimed in claim 1, wherein the step of chlorination is carried out at a temperature in the range of 25 °C to 80 °C, for a period of time in the range of 60 minutes to 360 minutes.
7. The process as claimed in claim 1, wherein the concentration of the aqueous hydrochloric acid is in the range of 0.1 M to 0.55 M; wherein the weight ratio of the polymer and the aqueous hydrochloric acid is in the range of 1:20 to 1:1.
8. The process as claimed in claim 1, wherein the base is selected from the group consisting of Ca(OH)2, Mg(OH)2, NaOH, Na2CO3, NaHCO3, and CaCO3; wherein the base is in the form of an aqueous solution having a concentration in the range of 0.01 M to 0.03 M.
9. The process as claimed in claim 1, wherein the concentration of the sodium hypochlorite solution is in the range of 0.05 wt% to 0.15 wt%; and wherein the hypochlorite treated chlorinated polymer is dried at a temperature in the range of 30 °C to 130 °C.
10. The process as claimed in claim 1, wherein the mother liquor obtained in step (b), is recovered and the recovered mother liquor is reused in the step of chlorination.

Dated this 27th day of August, 2019

MOHAN DEWAN
of R.K. DEWAN & COMPANY
IN/PA-25
APPLICANT’S PATENT ATTORNEY

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI
, Description:

FIELD
The present disclosure relates to a process for preparing a chlorinated polymer.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Chlorinated polymers are important intermediates in the polymer industry. Typically, chlorination of a polymer is carried out using chlorine as the chlorinating agent, and water as a fluid medium. A portion of chlorine is utilized for chlorination of the polymer as described in equation (1).
-(CH2-CHCl-CH2)- + Cl2 ? -(CHCl-CH(Cl)-CHCl)- + HCl (1)
However, other portion of chlorine reacts with water and produces by-products HCl and hypochlorous acid (HOCl), as described in equation (2).
H2O + Cl2 ? HCl + HOCl (2)
The use of water as a fluid medium has various drawbacks. Firstly, the portion of chlorine that reacts with water is wasted, and it produces environmentally hazardous by-products. Further, the disposal of HCl and HOCl adds to the cost of the process. Secondly, the highly reactive HOCl oxidizes chlorinated polymer. The oxidized chlorinated polymer has reduced thermal stability and reduced inherent viscosity.
There is, therefore, felt a need to provide simple, efficient, and environmentally friendly process for preparing chlorinated polymer. Further, it is desired that the formation of HOCl during the chlorination of polymer is reduced.

OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a simple and efficient process for the preparation of chlorinated polymer.
Yet another object of the present disclosure is to provide a process for the preparation of chlorinated polymer, which involves reduced formation of hypochlorous acid (HOCl).
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 relates to a process for preparing a chlorinated polymer by chlorination of a polymer.
In accordance with the present disclosure, the process for preparation of the chlorinated polymer comprises the following steps. The polymer is chlorinated with a chlorinating agent, in the presence of aqueous hydrochloric acid, under exposure to light radiation to obtain a product mixture comprising crude chlorinated polymer, and aqueous hydrochloric acid. The product mixture is filtered to obtain a residue comprising crude chlorinated polymer and mother liquor comprising aqueous hydrochloric acid. The residue is partially dehydrated by washing with a fluid medium to obtain a wet cake of crude chlorinated polymer containing less than 30% moisture. The wet cake is dried under reduced pressure to obtain dry mass of crude chlorinated polymer. The dry mass of crude chlorinated polymer is contacted with a base to obtain neutralized chlorinated polymer. The neutralized chlorinated polymer is treated with sodium hypochlorite solution to obtain a hypochlorite treated chlorinated polymer. The hypochlorite treated chlorinated polymer is dried to obtain chlorinated polymer.
In accordance with the embodiments of the present disclosure, the polymer is at least one selected from the group consisting of polyvinyl chloride, polyethylene and polyvinylidene chloride.
In accordance with the embodiments of the present disclosure, the polymer is in at least one form selected from the group consisting of powder, granules, fibres, and mixture thereof. The polymer has porosity in the range of 0.19 mL/g to 0.29 mL/g.
In accordance with the embodiments of the present disclosure, the chlorinating agent is at least one selected from the group consisting of chlorine, and SO2Cl2. The weight ratio of the chlorinating agent and the polymer is in the range of 5:1 to 1:5.
In accordance with the embodiments of the present disclosure, the light radiations used in the step of chlorination have wavelength in the range of 400 nm to 700 nm, and intensity in the range of 2 Watt/Kg of the polymer to 100 Watt/Kg of the polymer. The light radiations are emitted by a source of light radiation selected from the group consisting of Light Emitting Diode (LED), Light Amplification by Stimulated Emission of Radiation (LASER), and filament based lamp.
In accordance with the embodiments of the present disclosure, the step of chlorination is carried out at a temperature in the range of 25 °C to 80 °C, and for a period of time in the range of 60 minutes to 360 minutes.
In accordance with the embodiments of the present disclosure, the concentration of the aqueous hydrochloric acid is in the range of 0.01 M to 0.55 M. The weight ratio of the polymer and the aqueous hydrochloric acid is in the range of 1:20 to 1:1.
In accordance with the embodiments of the present disclosure, the base is selected from the group consisting of Ca(OH)2, NaOH, Na2CO3, NaHCO3, and CaCO3. The base is in the form of an aqueous solution having a concentration in the range of 0.01 M to 2.55 M.
In accordance with the embodiments of the present disclosure, the concentration of the sodium hypochlorite solution is in the range of 0.05 wt% to 0.15 wt%. The hypochlorite treated chlorinated polymer is dried at a temperature in the range of 30 °C to 130 °C.
In accordance with the embodiments of the present disclosure, the mother liquor obtained in the step of filtering the product mixture is recovered and the recovered mother liquor cab be reused in the step of chlorination.
DETAILED DESCRIPTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details, are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
Chlorinated polymers are important intermediates in the polymer industry. However, the processes for preparation of chlorinated polymer involve use of chlorine in water as a fluid medium leading to the formation of hypochlorous acid (HOCl). HOCl diminishes the properties of chlorinated polymers, and is hazardous in nature. Therefore, it is desired that the amount of HOCl formed during the chlorination process is reduced so that the chlorinated polymer has requisite thermally stimulated conductivity (TSC), and inherent viscosity (IV). The present disclosure envisages a simple and efficient process for the preparation of chlorinated polymer involving reduced amount of HOCl formation.
The present disclosure provides a process for the preparation of chlorinated polymer by chlorination of a polymer. The process involves the following steps.
The polymer is chlorinated with a chlorinating agent, in the presence of aqueous hydrochloric acid, under exposure to light radiation to obtain a product mixture comprising crude chlorinated polymer, and aqueous hydrochloric acid.
It is observed that the amount of HOCl formed during the process of the present disclosure depends upon the fluid medium used. In conventional processes, the chlorination of a polymer is carried out by using water as fluid medium. Chlorine reacts with water to generate HCl and HOCl [equation (2)]. HOCl is a highly reactive oxidizing agent that oxidizes the chlorinated polymer, resulting in a chlorinated polymer with reduced thermal stability (TSC), and inherent viscosity (IV). In conventional processes, the formation of HOCl is reduced by adding anti-oxidizing agents to the reaction mixture.
In the process of the present disclosure, the formation of HOCl was reduced by performing chlorination of the polymer in the presence of aqueous HCl as a fluid medium. The presence of HCl in the reaction mixture retards the reaction between water and chlorine gas, thus reducing the formation of HCl and HOCl [equation (2)]. Due to the lower amount of HOCl in the reaction medium, the chlorinated polymer prepared in the present disclosure has improved TSC, and IV, as compared to the chlorinated polymer prepared by the conventional process. Thus, reduced formation of HOCl is achieved without adding any anti-oxidizing agent to the reaction mixture in the process of the present disclosure.
The product mixture obtained in the chlorination step is filtered to obtain a residue comprising the crude chlorinated polymer and mother liquor comprising aqueous hydrochloric acid.
The residue is partially dehydrated by washing with a fluid medium selected from water, aqueous hydrochloric acid, and mother liquor from the chlorination reaction, to obtain a wet cake of the crude chlorinated polymer containing less than 30% moisture.
The wet cake is dried under reduced pressure to obtain a mass of the crude chlorinated polymer.
The dry mass of the crude chlorinated polymer is neutralized with a base to obtain neutralized chlorinated polymer.
The neutralized chlorinated polymer is treated with sodium hypochlorite to obtain hypochlorite treated chlorinated polymer.
The hypochlorite treated chlorinated polymer can be dried to obtain the chlorinated polymer.
In accordance with the embodiments of the present disclosure, the polymer is at least one selected from the group consisting of polyvinyl chloride (PVC), polyethylene and polyvinylidene chloride.
In accordance with one embodiment of the present disclosure, the polymer is polyvinyl chloride (PVC).
In conventional processes, PVC with high porosity, such as > 0.29 mL/g is used to achieve higher efficiency of chlorination. Greater porosity of the PVC improves the kinetics of chlorination reaction as a result of greater surface area and therefore provides greater rate of reaction.
In accordance with the embodiments of the present disclosure, the polyvinyl chloride (PVC) is in at least one form selected from the group consisting of powder, granules, fibres and mixture thereof. The polyvinyl chloride (PVC) has porosity in the range of 0.19 mL/g to 0.29 mL/g.
In accordance with one exemplary embodiment of the present disclosure, the polyvinyl chloride (PVC) is in the form of powder having porosity of 0.26 mL/g.
In accordance with the embodiments of the present disclosure, the chlorinating agent is at least one selected from the group consisting of chlorine, and SO2Cl2.
In accordance with one embodiment of the present disclosure, the chlorinating agent is chlorine.
In accordance with the embodiments of the present disclosure, the weight ratio of the chlorinating agent and the polymer is in the range of 5:1 to 1:5.
In accordance with one embodiment of the present disclosure, the weight ratio of chlorine and the polyvinyl chloride is 1.14 : 1.
The process of the present disclosure is environmentally friendly as it reduces the formation of HOCl.
Since, the reaction of chlorine and water is retarded, the amount of the chlorinating agent required for the chlorination of the polymer is also reduced.
The present invention uses 0.01M to 0.55M aqueous HCl (0.02 wt% to 2 wt% aqueous HCl), which inhibits the formation of HOCl and increases the solubility of chlorine gas in reaction mixture thereby increasing the rate of chlorination reaction.
In accordance with the embodiments of the present disclosure, the light radiations used in the step of chlorination have wavelength in the range of 400 nm to 700 nm, preferably, 400 nm to 570 nm, and intensity in the range of 2 watt/Kg of the polymer to 100 watt/Kg of the polymer. The light radiations are emitted by a source of light radiation selected from the group consisting of Light Emitting Diode (LED), Light Amplification by Stimulated Emission of Radiation (LASER), and filament based lamp.
In accordance with one embodiment of the present disclosure, the light radiations used in the step of chlorination have wavelength of 450 nm, and intensity of 16.5 watt/Kg of the polymer.
The present invention does not use initiators for carrying out the chlorination reaction and the Cl radicals are generated in presence of LED light.
In accordance with one embodiment of the present disclosure, the source of light radiation is LED.
In accordance with the embodiments of the present disclosure, the step of chlorination is carried out at a temperature in the range of 25 °C to 80 °C, for a period of time in the range of 60 minutes to 360 minutes.
In accordance with one embodiment of the present disclosure, the step of chlorination is carried out at a temperature of 70 °C, for 180 minutes.
The chlorination of the polymer by the process of the present disclosure is carried out in a single step.
In accordance with the embodiments of the present disclosure, the concentration of the aqueous hydrochloric acid is in the range of 0.01 M to 0.55 M (0.02 wt% to 2 wt% aqueous HCl).
In accordance with one embodiment of the present disclosure, the concentration of the aqueous hydrochloric acid is 0.5 M (1.8 wt% aqueous HCl).
In accordance with the embodiments of the present disclosure, the weight ratio of the polymer and the aqueous hydrochloric acid is in the range of 1:20 to 1:1.
In accordance with one embodiment of the present disclosure, the weight ratio of the polyvinyl chloride and the aqueous hydrochloric acid is 4:25.
In accordance with the embodiments of the present disclosure, the base is selected from the group consisting of Ca(OH)2, Mg(OH)2, NaOH, Na2CO3, NaHCO3, and CaCO3.
In accordance with the embodiments of the present disclosure, the base is used in the form of an aqueous solution. The aqueous solution of the base has a concentration in the range of 0.01 M to 2.55 M.
In accordance with the embodiments of the present disclosure, the concentration of the aqueous sodium hypochlorite solution is in the range of 0.01 wt% to 0.15 wt%.
In accordance with one embodiment of the present disclosure, the concentration of the aqueous sodium hypochlorite solution is 0.1 wt%.
In accordance with the embodiments of the present disclosure, the hypochlorite treated chlorinated polymer is dried at a temperature in the range of 30 °C to 130 °C.
In accordance with one embodiment of the present disclosure, the hypochlorite treated chlorinated polymer is dried at a temperature of 70 °C.
In accordance with the embodiments of the present disclosure, the mother liquor obtained in the step of filtering the product mixture is recovered. The recovered mother liquor is reused in the step of chlorination.
In the process of the present disclosure the recycling and reusing of the mother liquor for chlorination of polymer reduces the burden on environment.
It is observed that in the process of the present disclosure, the reaction time for chlorination of polymer is reduced by 10% to 20%, as compared to use of water as a fluid medium in conventional processes. Thus, the process of the present invention is efficient as compared to the conventional process.
It is observed that the chlorinated polymer obtained by chlorination of PVC in 0.5 M HCl solution has improved TSC, and improved IV as compared to the CPVC obtained by chlorination of PVC in water.
Typically, in a conventional process, enhancement in efficiency of chlorination of PVC is achieved by addition of additives such as dispersing agent or swelling agent to the reaction mixture.
In the process of the present disclosure high efficiency of chlorination of the polymer is achieved without adding any additives.
It was observed that in the process of the present disclosure formation of HOCl was suppressed.
The process of the present disclosure uses commonly available and inexpensive raw materials, reagents and fluid media, and recycles the fluid media. Further, in post chlorination process of the present invention, the effluent requires less cycles of water treatment to remove acid. Hence, the process of the present disclosure is simple, efficient, and economical.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
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 tested to scale up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTS
Experiments 1 and 2: Preparation of chlorinated polyvinyl chloride in aqueous hydrochloric acid (aqueous HCl).
Powder of polyvinyl chloride (PVC) (630 g, porosity 0.26 ml/g) was added to aqueous HCl solution (0.5 M, 4L) in a vessel equipped with a stirrer, a spurger, and a photo irradiation source to obtain a mixture. Chlorine (720 g, 10 moles) was passed through the mixture at a rate of 180 g/h to obtain a reaction mass. The reaction mass was irradiated using LED with light radiation having a wavelength of 450 nm, and intensity of 12 Watts, under stirring at a temperature of 70 °C, for 180 minutes to obtain a product mixture.
The product mixture was filtered to obtain a residue containing crude chlorinated polyvinyl chloride (820 g) and a mother liquor containing aqueous HCl. The residue was washed with water to obtain a wet cake of crude chlorinated polyvinyl chloride. The wet cake was dried under reduced pressure to obtain a mass of crude chlorinated polyvinyl chloride. The mass was neutralized with 2 L of 0.0125 (M) aqueous solution of Ca(OH)2 to obtain neutralized chlorinated polyvinyl chloride.
The neutralized chlorinated polyvinyl chloride was treated with 25 mL of sodium hypochlorite (0.1 wt%), to obtain hypochlorite treated chlorinated polyvinyl chloride. The hypochlorite treated chlorinated polyvinyl chloride was dried at 70°C for 180 minutes to obtain chlorinated polyvinyl chloride. The chlorinated polymer was analyzed for % chlorination, TSC, and IV. The mother liquor was titrated against 0.1 M NaOH solution and the results are presented in Table 1.
The experiment was repeated one more time.
Table 1: Chlorination of polyvinyl chloride (PVC) in 0.5 (M) HCl
Expt. No. Reaction in 0.5 (M) HCl
% Chlorination Burette Reading (Observed Value)* Burette Reading (Calculated Value)**
1. 67.02 7.58 7.29

2. 67.17 7.72 7.43

Thermally stimulated conductivity (TSC) (sec) = 672;
Inherent Viscosity (cm3/g) = 0.807
Reaction time = 180 minutes
* values obtained by titration of the mother liquor.
** values computed by theoretical calculation.
The observed values are identical to the calculated values. It indicates that HCl formation due to reaction of chlorine with water was suppressed.
% chlorination of the chlorinated PVC was found to be 67%.
Thermally stimulated conductivity (TSC) of the dried chlorinated polyvinyl chloride was found to be 672 (sec) and inherent viscosity (IV) of the dried chlorinated polyvinyl chloride was found to be 0.807.
Experiments 3 and 4: Comparative examples in DM Water.
The preparation of chlorinated polyvinyl chloride was carried out using DM water in place of 0.5 (M) HCl, using the procedure mentioned above for the Experiments 1 and 2.
The mother liquor was titrated against 0.1 M NaOH and the results are presented in Table 2.
Table 2: Chlorination of polyvinyl chloride (PVC) in water
Expt. No. Set 2: Reaction in DM water
%Chlorination Burette Reading (Observed Value)* Burette Reading (Calculated Value)**
3. 67.01 10.56 7.28

4. 67.48 11.01 7.71

Thermally stimulated conductivity (TSC) (sec) = 576;
Inherent Viscosity = 0.775
Reaction time = 210 minutes
* values obtained by titration of the mother liquor.
** values computed by theoretical calculation.
The observed values are greater than the calculated values. Large difference between observed and calculated values indicates that HCl was formed due to reaction of chlorine with water.
% chlorination of the chlorinated PVC was found to be 67%.
Thermally stimulated conductivity (TSC) of the dried chlorinated polyvinyl chloride was found to be 576 (sec) and inherent viscosity (IV) of the dried chlorinated polyvinyl chloride was found to be 0.775.
Upon comparing the results of experiments 1, and 2 (Table 1) with results of the experiments 3, and 4 (Table 2), it is evident that the use of aqueous HCl solution as a fluid medium resulted in chlorinated polyvinyl chloride (CPVC) having improved TSC, and improved IV as compared to the use of DM water as a fluid medium.
For obtaining 67% chlorination of polyvinyl chloride (PVC) using aqueous HCl solution as a fluid medium, reaction time of 180 minutes was required, whereas, on using DM water, reaction time of was 210 minutes. Thus, the 67% chlorination of polyvinyl chloride (CPVC) was achieved in 14% shorter time by using aqueous HCl solution in place of water.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The process of the present disclosure described herein above has several technical advantages including, but not limited to, the realization of;
• a simple, and efficient process for the preparation of chlorinated polymer,
• economical, and environmentally friendly process for the preparation of chlorinated polymer, and
• a process for the preparation of chlorinated polyvinyl chloride with improved TSC, and IV.
The embodiments as described herein above, and various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description.
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.
The foregoing description of specific embodiments 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 of 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. Further, 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.
Having described and illustrated the principles of the present disclosure with reference to the described embodiments, it will be recognized that the described embodiments can be modified in arrangement and detail without departing from the scope of such principles.
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.