CLIAMS:We claim:

1. A drying aid for a redispersible polymer powder, the drying aid being a formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is selected from alkyl having a formula CnH2n+1, wherein n = 1-6, alkylaryl and aryl;
X is selected from H+, alkali and alkaline earth metal.

2. A drying aid as claimed in claim 1 wherein, R1 is methyl and R2 is selected from methyl and ethyl.

3. A drying aid as claimed in claim 1, wherein alkali and alkaline earth metal is selected from calcium, barium, magnesium, potassium and sodium..

4. A process for preparing a drying aid, the process comprising:
reacting alkyl substituted alkoxy benzene having alkyl substitution at ortho position of the alkoxy group with sulfuric acid to obtain alkyl substituted alkoxy benzene sulfonic acid; and
condensing the alkyl substituted alkoxy benzene sulfonic acid with formaldehyde to obtain the drying aid, wherein the drying aid is a formaldehyde condensate of alkyl substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkyl aryl or aryl;
X is H+.

5. A process as claimed in claim 4, further comprising obtaining a salt of the dying aid by reacting the drying aid with an alkaline or alkaline earth metal to obtain a drying aid, having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkyl aryl or aryl;
X is any one of alkali and alkaline earth metal.

6. A process as claimed in claim 5, wherein the alkaline or alkaline earth metal is selected from calcium, barium, magnesium, potassium and sodium.

7. A process as claimed in claim 4, wherein the alkyl substituted alkoxy benzene is reacted with excess of sulfuric acid than that required for a molar reaction.

8. A process as claimed in claim 4, wherein reacting alkyl substituted alkoxy benzene with sulfuric acid comprises of mixing sulfuric acid with alkyl substituted alkoxy benzene at a temperature in a range of 35C to 60C and heating the mixture to a temperature in a range of 85C to 95C to obtain alkyl substituted alkoxy benzene sulfonic acid.

9. A redispersible powder comprising:
a polymer; and
a drying aid, the drying aid being a formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is selected from alkyl having a formula CnH2n+1, wherein n = 1-6, alkyl aryl and aryl;
X is selected from H+, alkali and alkaline earth metal;
a protective colloid; and
an anti-blocking agent.

10. A redispersible powder as claimed in claim 9, wherein R1 is methyl and R2 is selected from methyl and ethyl.

11. A redispersible powder as claimed in claim 9, wherein alkali and alkaline earth metal is selected from calcium, barium, magnesium, potassium and sodium.

12. A redispersible powder as claimed in claim 9, wherein the drying aid is in a range of 1-20 weight % with respect to the weight of the polymer.

13. A redispesible powder as claimed in claim 9, wherein the polymer is a co-polymer of ethylenically unsaturated monomers, their esters, acrylic esters and halides.

14. A redispesible powder as claimed in claim 9, wherein the polymer is a co-polymer of substituted vinyl ester having formula (III);

(III)
wherein,
R'1 is selected from H and CH3;
R'2 is selected from alkyl, alkyl aryl, and alkyl halide; and
substituted vinyl acrylate having formula (IV)

(IV)
wherein,
R'3 is selected from H and CH3;
R'4 is selected from alkyl, alkyl aryl and alkyl halide.

15. A redispersible powder as claimed in claim 9, wherein the polymer is co-polymer of vinyl acetate and n-butyl acrylate.

16. A redispersible powder as claimed in claim 9, wherein the protective colloid is selected from partially hydrolyzed polyvinyl alcohol, fully hydrolyzed polyvinyl alcohol, partially hydrolyzed acetate and mixtures thereof.

17. A redispersible powder as claimed in claim 9, wherein the anti-blocking agent is selected from silicon dioxide, talc, kaolin, calcium carbonate, dolomite, calcium silicate, sodium aluminosilicate, dicalcium phosphate potato starch, microcrystalline cellulose, calcined clay, uncalcined clay and mixtures thereof.

Dated this 27th day of October 2014

Aparna Kareer
Of Obhan & Associates
Agent for the Applicant
Patent Agent No. 1359

,TagSPECI:The present disclosure relates to a drying aid for re-dispersible polymer powders and a process of preparation thereof. The present disclosure also relates to a redispersible powder.
BACKGROUND
Polymers find application in a number of industries. For example polymers are used as construction binders in adhesives, paints, plasters, concrete, mortar or coating material. In most applications it is desirable that the polymer be supplied in powder form.
In order to obtain polymers in powder form, liquid polymer dispersion is subjected to a drying step for example by spray drying or freeze drying. Generally, polymers tend to form pre-formed films during the drying process. These pre-formed films are retained when the polymers are re-dispersed, which reduces the performance characteristics of the polymer dispersions obtained by re-dispersion.
Generally, pre-formed film formation of the polymer particles can be prevented by including hard, water-soluble additives known as a drying aid or spray additive to the emulsion polymer prior to the drying step. The drying aid distributes itself between the continuous aqueous phase and the surface of the polymer particles acting as an inter-particle spacer. Irreversible coalescence of the polymer particles to form pre-formed films is thus prevented. When the dried polymer powder is subsequently mixed with water again, even low-level shear is sufficient to cause the drying aid to dissolve completely thereby releasing the polymer particles. The polymer powder is thus re-dispersible [Dörr, H.; Doing without water - optimized formulations and the production of dispersible powder pigments, Farbe & Lack 101 (1995), No. 8, p. 708].
Various drying aids are known in the art. EP 0134451, for example discloses the use of various naturally occurring water-soluble substances, such as starches, starch derivatives, proteins and/or water-soluble polymers as drying aid in the preparation of redispersible polymer powders. U.S. Patent 3883489 describes the use of polyvinyl alcohol as a drying aid for ethylene vinyl acetate dispersions.
Additionally, use of salts of arylsulfonic acid-formaldehyde condensates as drying aid is also known, especially for acrylic dispersions. U.S. Patent 5225478 describes the use of phenol sulfonic acid formaldehyde condensates and their alkali salts or alkali earth metal salts as a drying aid. The main drawback of using such drying aids is the formation of colour and compatibility issue with cementious material.
Further, WO 2005/021145 discloses an ortho-cresol based condensation polymer as a drying aid. The ortho-cresol based condensation polymer has a strong amber colour and hence is also not suitable for white or light colour cementious application. Further, this drying aid does not adhere to the cementious material matrix and tends to come on the outer surface after final application.
There, however, remains a need for a suitable drying aid that may be used for the preparation of polymeric powders, especially for the application in white or light colour cementious materials. Particularly, the drying aid should be such that it prevents the pre-formed film formation of the polymer particles efficiently.
SUMMARY
In one aspect a drying aid for a redispersible polymer powder is provided. The drying aid being a formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)
(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is selected from alkyl having a formula CnH2n+1, wherein n = 1-6, alkylaryl and aryl;
X is selected from H+, alkali and alkaline earth metal.
In another aspect, a process for preparing a drying aid is provided. The process comprises reacting alkyl substituted alkoxy benzene having alkyl substitution at ortho position of the alkoxy group with sulfuric acid to obtain alkyl substituted alkoxy benzene sulfonic acid; and condensing the alkyl substituted alkoxy benzene sulfonic acid with formaldehyde to obtain the drying aid, wherein the drying aid is a formaldehyde condensate of alkyl substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkyl aryl or aryl;
X is H+.
In yet another aspect, a redispersible powder is provided. The redispersible powder comprises a polymer; a dying aid, the drying aid being a formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is selected from alkyl having a formula CnH2n+1, wherein n = 1-6, alkylaryl and aryl;
X is selected from H+, alkali and alkaline earth metal;
a protective colloid; and
an anti-blocking agent.
DETAILED DESCRIPTION:
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the disclosed composition and process, and such further applications of the principles of the invention therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The present disclosure relates to a drying aid for a redispersible polymer powder. The drying aid is an aldehyde condensate of substituted alkoxy benzene sulfonic acid or their salts.
In accordance with an aspect, the drying aid is a formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is any one of alkyl chain of formulaCnH2n+1, wherein n = 1-6;
R2 is any one of alkyl chain of formula CnH2n+1, wherein n = 1-6 or alkylaryl or aryl;
X is any one of H+, any alkali or alkaline earth metal
In accordance with an aspect, alkaline or alkaline earth metal is selected from calcium, barium, magnesium, potassium or sodium.
In accordance with an aspect, R1 is methyl and R2 is selected from methyl and ethyl.
By way of a specific example, the drying aid is 2-methyl anisole sulfonic acid-formaldehyde condensate having the formula (II)

(II)
By way of another example, the drying aid is 2-ethyl anisole sulfonic acid-formaldehyde condensate.
The present disclosure also relates to a process for preparing the drying aid.
The process comprises of reacting alkyl substituted alkoxy benzene having alkyl substitution at ortho position of the alkoxy group with sulfuric acid to obtain alkyl substituted alkoxy benzene sulfonic acid; and condensing the alkyl substituted alkoxy benzene sulfonic acid with formaldehyde to obtain the drying aid, wherein the drying aid is a formaldehyde condensate of alkyl substituted alkoxy benzene sulfonic acid having formula (I).

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkyl aryl or aryl;
X is H+.
In accordance with an aspect, the process further comprises obtaining a salt of the dying aid by reacting the drying aid with an alkaline or alkaline earth metal to obtain a drying aid, having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkyl aryl or aryl;
X is any one of alkali and alkaline earth metal.
The alkaline or alkaline earth metal includes calcium, barium, magnesium, potassium and sodium.
In accordance with an aspect, the alkyl substituted alkoxy benzene is heated to a temperature in the range of 35 to 60°C prior to addition of sulfuric acid. The sulfuric acid is added slowly. Once the sulfuric acid is added the temperature of the reaction mixture is raised to 85-95 °C to allow for sulfonation of alkyl substituted alkoxy benzene.
In accordance with an aspect, a slight excess of sulfuric acid is reacted with the alkyl substituted alkoxy benzene than required for molar reaction to obtain the sulfonated alkyl substituted alkoxy benzene.
The disclosure also relates to a redispersible powder. The redispersible powder comprises of a polymer; and a drying aid, the drying aid is formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkylaryl or aryl;
X is any one of H+, alkali or alkaline earth metal.
In accordance with an aspect, the redispersible powder further comprises of a protective colloid. The protective colloid is selected from partially hydrolyzed polyvinyl alcohol, fully hydrolyzed polyvinyl alcohol, partially hydrolyzed acetate, and mixtures thereof.
In accordance with an aspect, the redispersible powder further comprises of an anticaking agent. Anticaking agents include but are not limited to silicon dioxide, talc, kaolin, calcium carbonate, dolomite, calcium silicate, sodium aluminosilicate, dicalcium phosphate potato starch, microcrystalline cellulose, calcined clay, uncalcined clay and mixtures thereof.
In accordance with an aspect, the drying aid is in a range of 1-20 weight % with respect to the weight of the polymer.
In accordance with an aspect, the polymer is a co-polymer of ethylenically unsaturated monomers, their esters, acrylic esters and halides.
The disclosure also relates to a method for preparing a re-dispersible polymer powder. The method comprises preparing a polymer dispersion; adding a drying aid to the polymer dispersion, the drying aid being aldehyde condensate of substituted alkoxy benzene sulfonic acid or their salts to obtain a mixture of polymer and drying aid; and drying the mixture of polymer and drying aid to obtain the redispersible polymer powder.
In accordance with an aspect, the drying aid is added to the polymer dispersion in a range of 1-20 weight % with respect to the weight of the polymer.
The polymers used in combination with the drying aid include polymer is a film forming polymer or co-polymer based on one or more monomer from the group consisting of (meth) acrylic ester; vinyl aromatics; 1,2-dienes; ethnylically unsaturated monomers, their esters and halides.
In accordance with an aspect, the polymer is prepared from aqueous emulsion polymerization of monomers containing ethylenic unsaturation, vinyl acetate, vinyl chloride, ethylene, butadiene, acrylonitrile, and a dialkyl fumarate acrylic acid, acrylamide, acryloyl chloride, and methyl methacrylate. Typical examples of such co-monomers include (meth)acrylate type monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, α-chloroethyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate and ethoxypropyl (meth)acrylate; styrene type monomers such as styrene, methylstyrene, chlorostyrene and methoxystyrene; carboxyl group-containing monomers such as (meth)acrylic acid, crotonic acid, itaconic acid, itaconic acid half ester, maleic acid and maleic acid half ester; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2(3)-hydroxypropyl (meth)acrylate, 4-hydroxybutyl acrylate and mono(meth)acrylic acid ester of allyl alcohol polyhydric alcohol; amide group-containing monomers such as (meth)acrylamide and maleinamide; amino group-containing monomers such as 2-aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, 3-aminopropyl (meth)acrylate, 2-butylaminoethyl (meth)acrylate and vinylpyridine; acrylamide, vinyl acetate, vinyl chloride, ethylene, butadiene, acrylonitrile, and a dialkyl fumarate. By way of example the monomers are selected from substituted vinyl ester having formula (III), where and substituted vinyl acrylate having formula (IV).

(III)
wherein,
R'1 is H, CH3;
R'2 is alkyl, alkyl aryl, alkyl halide

(IV)
wherein,
R'3 is H, CH3;
R'4 is alkyl, alkyl aryl, alkyl halide.
By way of a specific example, the polymer is a polymer of vinyl acetate and n-butyl acrylate. However, the type of polymer is not critical for the use of the invention. Thus, the drying aid described above may be used in combination with most polymers used in the manufacture of construction products and as dispersion polymers in water as long as the two components are compatible when mixed in liquid form before drying.
In accordance with an aspect, the drying aid is mixed with the polymer dispersion prior to drying. The mixture of drying aid and polymer dispersion may be dried using any convention method. In accordance with an aspect, the mixture is dried at a temperature in the range of internal temperature from 80 °C to 200 °C.
In accordance with an embodiment, other known drying aids for example, polyvinyl alcohol may also be added to the mixture of polymer dispersion and drying aid prior to drying. Other known drying aids for example polyvinyl alcohol is added to the mixture of polymer dispersion and drying aid, in a range of 0 to 20 % weight with respect to the weight of the total monomers
Anticaking agent may also be added to the polymer powder while the same is suspended in the air stream. Anticaking agents include but are not limited to silicon dioxide, talc, kaolin, calcium carbonate, dolomite, calcium silicate, sodium aluminosilicate, dicalcium phosphate potato starch, microcrystalline cellulose, calcined clay, uncalcined clay and mixtures thereof.
The embodiments of the invention will now be discussed in more detail with reference to the following examples which are provided for exemplification only and which should not be considered limiting on the scope of the invention in any way.
Example-1:
A 250 mL glass reactor equipped with dropping funnel, mechanical stirrer, and a reflux condenser was charged with 24.4 grams of 2-methyl anisole and heated to 40 °C in a water bath. Slowly it was heated to 60 °C and 24.08 grams of sulfuric acid (98%) was added over 40 minutes to the reaction mixture. The temperature of the reaction mixture was raised to 85-95 °C and the same was stirred at this temperature for 75 minutes. The content of the reactor was cooled to 60 °C and 80 grams of water was added. 11 grams of formaldehyde (30% aq. solution) was added drop-wise into the reactor over 30 minutes and contents were continued to be heated at 85-95° C for 2 hours and 30 minutes to obtain 2-methyl anisole sulfonic acid-formaldehyde condensate. The content of reactor was then poured into 220 grams of water containing 17.17 grams of calcium hydroxide to convert 2-methyl anisole sulfonic acid-formaldehyde condensate into its calcium salt. This solution was filtered and the filtrate was then evaporated to produce off white solid, drying aid.
Example-2:
A 250 mL glass reactor equipped with dropping funnel, mechanical stirrer, and a reflux condenser was charged with 24.4 grams of 2-methyl anisole and heated to 40 °C in a water bath. Slowly it was heated to 60 °C and 30 grams (molar excess) of sulfuric acid (98%) was added over 40 minutes to the reaction mixture. The temperature of the reaction mixture was raised to 85-95 °C and the same was stirred at this temperature for 75 minutes. The content of the reactor was cooled to 60 °C and 80 grams of water was added. 11 grams of formaldehyde (30% aq. solution) was added drop-wise into the reactor over 30 minutes and contents were continued to be heated at 85-95° C for 2 hours and 30 minutes to obtain 2-methyl anisole sulfonic acid-formaldehyde condensate. The content of reactor was then poured into 220 grams of water containing 24 grams of calcium hydroxide to convert 2-methyl anisole sulfonic acid-formaldehyde condensate into its calcium salt. A layer of calcium sulfate settles down, which is formed due to excess sulfuric acid. This solution was filtered and the filtrate was then evaporated to produce off white solid, drying aid.
Example 3:
A 250 mL glass reactor equipped with dropping funnel, mechanical stirrer, and a reflux condenser was charged with 27.2 grams of 2-ethyl anisole and heated to 40 °C in a water bath. Slowly it was heated to 60 °C and 23.91 grams of sulfuric acid (98%) was added over 40 minutes to the reaction mixture. The temperature of the reaction mixture was raised to 85-95 °C and the same was stirred at this temperature for 75 minutes. The content of the reactor was cooled to 60 °C and 80 grams of water was added. 11 grams of formaldehyde (30% aq. solution) was added drop-wise into the reactor over 30 minutes and contents were continued to be heated at 85-95° C for 2 hours and 30 minutes to obtain 2-ethyl anisole sulfonic acid-formaldehyde condensate. The content of reactor was then poured into 245 grams of water containing 17.19 grams of calcium hydroxide to convert 2-ethyl anisole sulfonic acid-formaldehyde condensate into its calcium salt. This solution was filtered and the filtrate was then evaporated to produce off white solid, drying aid.
Example 4:
A 250 mL glass reactor equipped with dropping funnel, mechanical stirrer, and a reflux condenser was charged with 24.4 grams of 2-methyl anisole and heated to 40 °C in a water bath. Slowly it was heated to 60 °C and 24.08 grams of sulfuric acid (98%) was added over 40 minutes to the reaction mixture. The temperature of the reaction mixture was raised to 85-95 °C and the same was stirred at this temperature for 75 minutes. The content of the reactor was cooled to 60 °C and 80 grams of water was added. 11 grams of formaldehyde (30% aq. solution) was added drop-wise into the reactor over 30 minutes and contents were continued to be heated at 85-95° C for 2 hours and 30 minutes to obtain 2-methyl anisole sulfonic acid-formaldehyde condensate. The content of reactor was then poured into 264 grams of water containing 18.56 grams of sodium hydroxide to convert 2-methyl anisole sulfonic acid-formaldehyde condensate into its calcium salt. This solution was filtered and the filtrate was then evaporated to produce off white solid, drying aid.
Example 5
A 250 mL glass reactor equipped with dropping funnel, mechanical stirrer, and a reflux condenser was charged with 35.64 grams of 1-butyl-2-ethoxybenzene and heated to 40 °C in a water bath. Slowly it was heated to 60 °C and 23.91 grams of sulfuric acid (98%) was added over 40 minutes to the reaction mixture. The temperature of the reaction mixture was raised to 85-95 °C and the same was stirred at this temperature for 75 minutes. The content of the reactor was cooled to 60 °C and 80 grams of water was added. 11 grams of formaldehyde (30% aq. solution) was added drop-wise into the reactor over 30 minutes and contents were continued to be heated at 85-95°C for 2 hours and 30 minutes to obtain 1-butyl-2-ethoxybenzene sulfonic acid-formaldehyde condensate. The content of reactor was then poured into 381 grams of water containing 26.04 grams of potassium hydroxide to convert 1-butyl-2-ethoxybenzene sulfonic acid-formaldehyde condensate into its potassium salt. This solution was filtered and the filtrate was then evaporated to produce off white solid, drying aid.
Example 6:
The polymer dispersion described here is of 70% vinyl acetate and 30% n-butyl acrylate (w/w). Emulsion polymerization is carried out by seed polymerization technique. A resin kettle glass reactor equipped with overhead stirrer, reflux condenser, dropping addition funnel and thermometer was charged with 128 grams of de-mineralized water, 6.25 grams of nonylphenol ethoxylate (ethoxylate 15 mole) as nonionic surfactant, 25 grams of polyvinyl alcohol (mol. wt. 14000) solution (15% w/w aq. solution) as co-surfactant, 0.79 grams sodium bicarbonate as buffer, 12.6 grams of vinyl acetate and 5.4 grams of n-butyl acrylate. It was heated at 55 °C with stirring at 280 RPM. To initiate the polymerization with redox initiators, 0.25 grams of t-butyl hydroperoxide (used as 2% aq. solution) and 0.87 grams of sodium formaldehyde sulfoxylate (used as 6% aq. solution) was added drop wise through separate dropping funnels for over a period of 30 minutes. After the formation of vinyl acetate - butyl acrylate pre-polymer emulsion (in previous stage), 113.4 grams of vinyl acetate, 48.6 grams of butyl acrylate, 0.468 grams of t-butyl hydroperoxide (used as 1% aq. solution), and 1.6 grams of sodium formaldehyde sulfoxylate (used as 3% aq. solution) each were taken in separate dropping funnels and added drop-wise. Subsequently, another lot of 0.08 grams of t-butyl hydroperoxide (used as 1% aq. solution) and 0.29 grams of sodium formaldehyde sulfoxylate (used as 3% aq. solution) was added drop wise for another 120 minutes at same speed. In order to reduce the unreacted monomer, 0.04 grams of t-butyl hydroperoxide (used as 2% aqueous solution) and 0.15 grams of sodium formaldehyde sulfoxylate (used as 6% aqueous solution) was added at once with stirring. The polymer dispersion (emulsion) was cooled to room temperature. To store the polymer dispersion (emulsion) pH was maintained at approximately 7 by adding aqueous solution of sodium carbonate. The solid content of the emulsion was about 40% with conversion rate of 99%. The Brookfield viscosity is 250 cps (#3, 100 mL at 25 °C).
Example 7:
The above emulsion polymer was mixed with 3% polyvinyl alcohol (87-89 mole % hydrolyzed; MW=13000-23000) and 10% methyl anisole based drying aid (prepared in example 1) with respect to the solid content of polymer dispersion (emulsion) to form a spray dry feed having the following composition:
34% emulsion copolymer solids; 1.0% polyvinyl alcohol; 3.4 % drying aid, 61.6% water.
This spray dry feed having a viscosity of 220 cps was fed through a spray dry tower (having water evaporation capacity 2 kilograms/hour) at a rate of 720 grams/hour through a plunger pump. As a result, 270 grams/hour of dry polymer powder was produced and 440 grams/hour of water was evaporated. During the drying process 30 grams/hour of clay was metered into spray dry tower with the help of compressed air. The spray dryer was operated utilizing two fluid nozzle having compressed air pressure of 4 kilograms/centimeter2 with an inlet temperature of 110 °C, and an outlet temperature of 85 °C. To this powder product a mixture of 5% of clay and 5% of fumed silica with respect to the final dried product were blended to act as anti-caking agents. The product showed good dispersibility having sedimentation value of 0mm and 12mm at 1 hour and 24 hours respectively.
Sedimentation value yields information about the redispersibility of the investigated powder. For determining sedimentation value, the powder is redispersed in water at a ratio of 1:1 and then diluted. 50 grams of the 5% redispersions are filled into calibrated tubes and after 1 hour and 24 hours, the height of the sedimented layer is measured. The lower the obtained values the better is the redispersibility of the powder.
Example 8:
3% of the dispersible powder is mixed with white cement, mineral fillers, specialty polymers (proprietary materials) and 36% water (w/w) at the time of application, followed by vigorous mixing for 5-10 minutes to give homogeneous paste or putty paste. After cleaning and wetting of a cementitious surface with water, a thin coat of the putty paste is applied with the help of 10inch steel blade in order to fill the pores and hairline cracks of the cementitious surface. After drying, a second coat of putty is applied which gives a smooth finish and sheen to the surface. The thickness of each coat of putty is between 0.5 to 1.0 millimeters. On this surface different tests were performed according to the standard as mentioned below-
• Tensile adhesion strength (Test method: EN 1348)
• Pot life (Test method: EN 196)
• Water absorption (Test method: Karsten tube)
• Dry and Wet chalking (Rub test)
• Workability
Properties of the surface with the putty coats are described in Table-1. The Tensile Adhesion Strength and pot life of putty is compared with specification of HDB (Housing & Development Board), Singapore.

Table-1: Characteristics of putty with time
Test Period Tensile Adhesion Strength improvement (%) Water Absorption (mL/30min) Chalking
(Dry and Wet) Pot Life
3rd Day 24 0.3 Nil 3 h
7th Day 44 0.37 Nil
HDB Specification 0.8 N/mm2 - Nil < 6 h

Specific embodiments are disclosed below:
A drying aid for a redispersible polymer powder, the drying aid being a formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is selected from alkyl having a formula CnH2n+1, wherein n = 1-6, alkyl aryl and aryl;
X is selected from H+, alkali and alkaline earth metal.
Such drying aid(s) wherein, R1 is methyl and R2 is selected from methyl and ethyl.
Such drying aid(s), wherein wherein alkali and alkaline earth metal is selected from calcium, barium, magnesium, potassium and sodium.
Further specific embodiments are disclosed below:
A process for preparing a drying aid, the process comprising reacting alkyl substituted alkoxy benzene having alkyl substitution at ortho position of the alkoxy group with sulfuric acid to obtain alkyl substituted alkoxy benzene sulfonic acid; and condensing the alkyl substituted alkoxy benzene sulfonic acid with formaldehyde to obtain the drying aid, wherein the drying aid is a formaldehyde condensate of alkyl substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkyl aryl or aryl;
X is H+.
Such process(s), further comprising obtaining a salt of the drying aid by reacting the drying aid with an alkaline or alkaline earth metal to obtain a drying aid, having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is alkyl having a formula CnH2n+1, wherein n = 1-6; alkyl aryl or aryl;
X is any one of alkali and alkaline earth metal.
Such process(s), wherein the alkaline or alkaline earth metal is selected from calcium, barium, magnesium, potassium and sodium.
Such process(s), wherein the alkyl substituted alkoxy benzene is reacted with excess of sulfuric acid than that required for a molar reaction.
Such process(s), wherein reacting alkyl substituted alkoxy benzene with sulfuric acid comprises of mixing sulfuric acid with alkyl substituted alkoxy benzene at a temperature in a range of 35C to 60C and heating the mixture to a temperature in a range of 85C to 95C to obtain alkyl substituted alkoxy benzene sulfonic acid.

Further specific embodiments are disclosed below:
A redispersible powder comprising a polymer; and a dying aid, the drying aid being a formaldehyde condensate of substituted alkoxy benzene sulfonic acid having formula (I)

(I)
wherein,
R1 is alkyl having a formula CnH2n+1, wherein n = 1-6;
R2 is selected from alkyl having a formula CnH2n+1, wherein n = 1-6, alkylaryl and aryl;
X is selected from H+, alkali and alkaline earth metal;
a protective colloid; and
an anti-blocking agent.
Such redispersible powder(s), wherein R1 is methyl and R2 is selected from methyl and ethyl.
Such redispersible powder(s), wherein wherein alkali and alkaline earth metal is selected from calcium, barium, magnesium, potassium and sodium.
Such redispersible powder(s), wherein the drying aid is in a range of 1-20 weight % with respect to the weight of the polymer.
Such redispersible powder(s), wherein the polymer is a co-polymer of ethylenically unsaturated monomers, their esters, acrylic esters and halides.
Such redispersible powder(s), wherein the polymer is a co-polymer of substituted vinyl ester having formula (III);

(III)
wherein,
R'1 is selected from H and CH3;
R'2 is selected from alkyl, alkyl aryl, and alkyl halide; and
substituted vinyl acrylate having formula (IV)

(IV)
wherein,
R'3 is selected from H and CH3;
R'4 is selected from alkyl, alkyl aryl and alkyl halide.
Such redispersible powder(s), wherein the polymer is co-polymer of vinyl acetate and n-butyl acrylate.
Such redispersible powder(s), wherein the protective colloid is selected from partially hydrolyzed polyvinyl alcohol, fully hydrolyzed polyvinyl alcohol, partially hydrolyzed acetate and mixtures thereof.
Such redispersible powder(s), wherein the anti-blocking agent is selected from silicon dioxide, talc, kaolin, calcium carbonate, dolomite, calcium silicate, sodium aluminosilicate, dicalcium phosphate potato starch microcrystalline cellulose, calcined clay, uncalcined clay and mixtures thereof.

INDUSTRIAL APPLICABILITY:
The drying aid as disclosed above allows for the production of stable re-dispersible polymer powders with narrow particle size distribution. Further, as the drying aid is whitish in colour it may be used along with white cement. Further, the re-dispersible polymer powder has better re-despersibility in water that allows for homogeneous distribution of the polymer powder in the final composition.