Specification
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See Section 10 : Rule 13)
TITLE
Process for manufacture of water-soluble, substantive UV-absorbing polymers
^
Field of Invention :
This invention relates to a process for manufacture of water-soluble cationic polymers containing cinnamidoalkylamine and / or benzamidoalkylamine moieties. This invention particularly relates to synthesis of non-hydrolyzable, UV-absorbing polymers that are substantive to skin, hair and fabric and hence useful for personal care and fabric care formulations.
Background and Prior Art:
US patent 3,864,473 (1975) reveals substantive sunscreen polymer based on polyethyleneimine and p-A^.A^-dimethylaminobenzoic acid. US patent 4,004,074 (1977) provides substantive polymeric sunscreen agents comprising an UV-absorbing moiety selected from salicylates, aminobenzoates and carboxy succinates and a substrate linking moiety selected from the group consisting of thiocarboxylic acids, mercaptans, guanidines and biguanidines. Plurality of substrate binding moieties is reported to make these polymers substantive.
US patent 4,233,430 (1980) discloses an antisolar acrylamide backbone polymer containing coumarins, benzothiazoles, 3-(acrylamidomethylbenzylidine) DL camphor as sunscreen moieties. The water insoluble polymers of this invention are used in leave on applications like antisolar lotion, cream, aerosol and oil. US patent 4,524,061 (1985) teaches the art of making polymeric sunscreen agents that comprise of olefinic p-aminobenzoate, A^-vinylpyrrolidinone, a vinyl lactam and acrylic or methacrylic acid. The polymeric sunscreens are claimed to have good adhesion to skin and to resist removal by salt or plain water. They are claimed to form a thin film that is easily removable by mildly alkaline soap or shampoo.
Interestingly, US patent 5,204,090 (1993) discloses use of combination of water insoluble film forming acrylic polymer and sunscreen agents to yield water proof high SPF compositions. US patent 4,508,882 (1985) employs UV-absorbing benzotriazole having vinyl group to make homopolymers as well as copolymers that are most effectively used for UV protection of plastics and wood. US patent 5,063,048 (1991) discloses UV Hght absorbing skin-protecting composition based on acrylic polymeric backbone containing salicylates, benzophenones and benzotriazoles as sunscreen moieties.
It is pertinent to mention here that all the polymeric sunscreens reported so far have been water-insoluble. It was in 1992-93, US patent 5,134,223 (1992), 5,243,021 (1993), 5,250,652 (1993) disclosed novel, water dispersible copolymers that contain UV-absorbing monomers based on moieties such as aminobenzoates and hydrophilicity was introduced by polyethylene glycol backbone. These polymers were mainly designed for fabric care to provide anti-fading effect. These patents describe sunscreen polymers that cover the entire UV range from 280 nm to 400 nm and making subtle changes in hydrophobicity and hydrophilicity to control dispersibility and adsorption properties with respect to fabric care application.
Polymer bound 2-(2-hydroxyphenyl)2H-benzotriazole as UV absorber is disclosed by US patent 5,099,027 (1992) for any exterior coating application (as in manufacture of optical lenses) and as components for sunscreening and suntanning lotions.
On the similar lines US patents 5,487,885 (1996) and 5,741,924 (1998) provide acrylic polymers with UV absorbing moieties having different ranges in conjugation with another hydrophilic monomer. The polymers are insoluble in water but reported to swell in water and are meant for dermatological formulation that can be coated, sprayed, spread on the surface and are claimed not to unduly penetrate the dermal layer. Use of such polymers in coating of lens surface and in other opthalmological solutions is described. The UV absorbing moieties cover derivatives of dibenzoyl methanes, dimethylamino benzoates and phenyl benzamides.
From above discussion it is clear that a polymeric sunscreens of prior art are substantive by virtue of their film forming nature. Only exception is US patent 4,004,074 (1977) where substantivity to skin was achieved through substrate linking groups like thiocarboxylic acids and mercaptans, etc.
Most of the UV-absorbing polymers reported so far are water-insoluble. To make these polymers useful for personal care products they need to be formulated with hydrophobic bases that give greasy feel. The water-insoluble polymers can be applied by aerosol spray preparations. However, the water-resistant films they form are quite difficult to remove. Hence there is a need to synthesise polymeric sunscreens that are water-soluble yet water-resistant once they are applied to skin, hair or fabric.
This is achieved in the present invention by synthesising water-soluble polymers containing cinnamidoalkylamines and / or benzamidoalkylamines that have lower critical solution temperature (LCST) of 35°C and through cationic centres for enhanced substantivity. When these water-soluble polymers are applied to skin, the temperature of body as well as the temperature of water and the salt content of water (in case of swimming in the sea) make them insoluble and hence do not get easily washed off. However, they can be easily removed by plain water (without salt) at ambient temperature (25°C).
Object of the Invention :
The main object of the present invention is to synthesise water-soluble macromolecules with cinnamido and benzamido moieties to provide UV-absorption and to provide significant levels of substantivity especially during an activity like swimming.
Another object of the present invention is to prepare useful cosmetic formulations and formulations for fabric care employing these new macromolecules.
Summarv of the Invention :
The present invention provides a process for synthesis of cationic polymers as represented by f Formula I,
Formula I
wherein; ArCO is group selected from p-methoxy cinnamoyl and / orp-dimethyl amino benzoyl;
R2 and R3 are selected from hydrogen, alkyl and cycloalkyl group containing from 1 to 6 carbon atoms;
m is an integer from 5 to 9 and n is an integer between 1 to 5 and m + n = 10;
comprising steps of
(i) reacting 1.0 mole of a compound of Formula n, wherein, ArCO is same as that in the compound of Formula I, and Ri is -OH, -CI or -0(CH2)pCH3 (p = 0 to 3), with 1 to 3 moles of a MA^-dimethyl propyl diamine, with or without a basic catalyst, with or without a solvent, to obtain a compound of Formula HI, till all of the said compound of Formula n has been reacted, removing the unreacted N,N-dimethyl propyl diamine remaining after the reaction and the solvent to obtain said compound of Formula HI;
(ii) copolymerising monomer of Formula IV and vinyl benzyl chloride (single isomer or mixture of isomers) in a solvent such as /-butanol in the range of 50 to 95 % by weight, preferably at 80 %, at 60 - 80°C, preferably at 80°C, by stirring under nitrogen with a peroxy or azo radical initiator;
(iii)quatemisation of tertiary cinnamidoalkyl amine and / or benzamidoalkyl amine of Formula HI with exact equivalence of copolymer of step (ii), compound of formula IV to displace chloro group of the copolymer, wherein ArCO, R2, R3, m, and n are same as those for compounds of Formula I, by stirring under nitrogen in the presence of a suitable polar solvent preferably isopropanol from about 30 % to 80 % by weight of reaction mass, until CI" reaches stoichiometric level forming the solution of polymers of Formula I.
Detailed Description of the Invention :
Formula V
The synthesis of the polymers represented by Formula I is carried out in three steps, (a) synthesis of cinnamidoalkylamines and / or benzamidoalkylamines, (b) copolymerisation of monomer of Formula IV and vinyl benzyl chloride, (c) functionalisation of this copolymer by quatemisation.
(a) Synthesis of cinnamidoalkylamines and / or benzamidoalkylamines :
In this process, the synthesis of cinnamidoalkylamines and / or benzamidoalkylamines involves, the amidification reaction between a compound of the Formula n when R1 = -OH or O-(CH2)pCH3 (p = 0 to 3), with A^.A^-dimethyl propyl diamine. It is carried in one embodiment of the invention, under pressure from about 10 psi to about 100 psi, in the presence of a basic catalyst such as sodium methoxide, sodium hydroxide from 0.25 % to 5.0 % by weight of the reaction mass at from about 120°C to about 200°C, to afford the intermediate compound of Formula El. The preferred amount of such a catalyst is 1.0 % w/w. The reaction is conveniently monitored by TLC using Merck's silica gel coated on either aluminium of plastic or reversed phase HPLC using UV detection. After the complete disappearance of Formula n, the excess diamine is distilled off under vacuum.
The compounds of Formula DI are synthesised by reacting acid chlorides of Formula n (1.0 mole) when Ri is -CI with the A^,A^-dimethyl propyl diamine (1.0 to 1.2 mole) at 20 - 50°C in an inert solvent like dichloromethane, ethylene dichloride, tetrahydrofuran and the like. The amidification reaction between a compound of Formula n when Ri = -CI is carried out with N,N-dimethyl propyl diamine at room temperature in the presence of a solvent.
(b) copolymerisation of monomer of Formula IV and vinyl benzyl chloride :
Copolymerisation of monomers of Formula IV and vinyl benzyl chloride (single isomer or mixture of isomers) is carried out in an inert atmosphere of either nitrogen or argon at temperature from about 60 to 120°C, in a suitable solvent in the presence of an initiator.
The concentration of monomers, substituted alkylacrylamides (Formula IV) and vinyl benzyl chloride in reaction mixture ranges from 10 % to 50 %, preferably 20 to 30 % by weight of reaction mass, balance being the solvent. The mole ratio of compounds of Formula IV to vinyl benzyl chloride varies from 5 : 5 : : 9 : 1. The preferred mole ratio of the two monomers is 8 : 2. The polymerisation is carried out in protic solvents such as lower alcohols (containing carbons from 1 to 4) or glycols, aprotic polar solvents like N,N-dimethyl formamide and dimethyl sulphoxide and combinations thereof.
The peroxy or azo initiators in polymerisation step of this process are employed from about 0.1 % to 5.0 % by weight of total mass of monomers. A variety of organic as well as inorganic peroxy initiators are used such as dibenzoyl peroxide, dilauroyl peroxide, ammonium persulphate and the like. Similarly, amongst a variety of azo initiators such as azocyanovaleric acid, azobisisobytyronitrile, azobiscyclohexanecarbonitrile and the like can be employed. Thus, the temperature for polymerisation is dictated by (a) monomer concentration, (b) the catalyst and (c) the solvent. The preferred conditions for polymerisations are such that the copolymer that is formed has average molecular weight of around 5 x 105.
(c) functionalisation of copolymer by quatemisation :
The quatemisation of cinnamidoalkylamine and / or benzamidoalkylamine (Formula HI) is carried out with copolymer of substituted alkylacrylamides and vinyl benzyl chloride in the presence of a suitable solvent such as A/,7V-dimethyl formamide, lower alcohols and glycols having carbon atoms from 1 to 6 or aqueous solution of these solvents. The temperature of quatemisation ranges from 60 to 120°C and the duration ranges from about 8 to 16 hours depending upon the solvent. The completion of reaction is ascertained by estimation of liberated Cr, the anion of quaternary nitrogen. The quatemisation of the copolymer gives water-soluble cationic macromolecules with UV absorbing cinnamido and / or benzamido moiety (Formula I).
TVi\is, \\\t copolymer cati be fuTiclicinialised b^ reactiTig Nvi\h ciimamidozAkylamTOe arid / or benzamidoalkylamine (Formula HI) to generate cationic polymers (Formula I) with substantivity to skin, hair and fabric. In functionalised polymers of Formula I, mole ratio of m : n varies from 5 : 5 to 9 : 1. The preferred ratio for m : n is between 8 : 2. The copolymers thus obtained are water-soluble with lower critical solution temperature (LCST) of 35°C. This means at or above 35°C the polymer phase-separates from its aqueous solution. Addition of small quantities of electrolytes also results in lowering of LCST and polymer loses its solubility and precipitates out. This inverse temperature dependant solubility behaviour of aqueous solution of these polymers is also exploited for their purification. The phase-separated polymers can either be dissolved in water or alcoholic solvents for their final use in formulations.
The number and the nature of the substituents selected are such that they do not render the final cationic polymers water-insoluble.
The preferred substituents in cationic polymers of Formula I containing cinnamidoalkylamine and / or benzamidoalkylamine are as follows;
ArCO is selected from p-methoxy cinnamoyl and / or p-dimethylamino benzoyl. Referring again to Formula I, the groups R2 and R3 are selected from H or alkyl groups containing from 1 to 6 carbon atoms.
The cationic polymers of the present invention are formed by quatemising tertiary amines of Formula EI by the copolymer made from compounds of Formula IV and vinyl benzyl chloride. The cationic polymers of the present invention, will also include an anion derived from quatemisation reactions. Thus, the cationic polymers of the present invention have CI" as the anion.
In another embodiment the process of the present invention relates to manufacture of cationic, UV absorbing, water-soluble polymers of Formula*I, in which ArCO is selected from p-methoxy cinnamoyl and / or p-dimethylamino benzoyl; R2 and R3 are selected from hydrogen, alkyl or cycloalkyl groups containing from 1 to 6 carbon atoms; the mole ratio of m : n is from 5 : 5 to 9 : 1, from the compounds of Formula n, EI, IV, and V, with respective substituents ArCO of Formula n, R2 and R3 of Formula IV as defined for the nolvmers of Formula T. in this embodiment and R\ of Formula II being,
In another embodiment the process of the present invention relates to manufacture of cationic, UV absorbing, water-soluble polymers of Formula I, in which ArCO = p-methoxy cinnamoyl, R2 = -H, R3 = isopropyl, the mole ratio, m : n is 8 : 2, from the compounds of Formula n (ethyl p-methoxy cinnamate, ArCO = p-methoxy cinnamoyl and R1 = -OC2H5) and N,N dimethylpropyldiamine, forming an intermediate compound of Formula HI (p-methoxy cinnamidopropyldimethyl amine, ArCO = p-methoxy cinnamoyl). Formula IV (A/-isopropyl acrylamide, R2 = -H, R3 = isopropyl) and Formula V (copolymer, m : n :: 8 : 2). Along with the synthesis of this polymeric UV-absorber, its substantivity and photoprotection efficacy to skin are described in Example I.
In another embodiment the process of the present invention relates to manufacture of cationic, UV absorbing, water-soluble polymers of Formula I, in which ArCO = p-dimethylamino benzoyl, R2 = -H, R3 = isopropyl, the mole ratio, m : n is 8 : 2, from the compounds of Formula II (ethyl p-dimethylamino benzoate, ArCO = p-dimethylamino benzoyl and R1 = -OC2H5) and N,N-dimethylpropyldiamine, forming an intermediate compound of Formula m (p-dimethylamino benzamidopropyldimethyl amine, ArCO = p-dimethylamino benzoyl), Formula IV (A^-isopropyl acrylamide, R2 = -H, R3 = isopropyl) and Formula V (copolymer, m : n :: 8 : 2).
In another embodiment the process of the present invention relates to manufacture of cationic, UV absorbing, water-soluble polymers of Formula I, in which ArCO = p-methoxy cinnamoyl, R2, R3 = -C2H5, the mole ratio m : n is 8 : 2, from the compounds of Formula n (p-methoxy cinnamoyl chloride, ArCO = p-methoxy cinnamoyl and R] = -CI) and N,N-dimethylpropyldiamine, forming an intermediate compound of Formula HI (p-methoxy cinnamidopropyldimethyl amine, ArCO = p-methoxy cinnamoyl). Formula IV (A^,A^-diethyl acrylamide, R2, R3 = -C2H5) and Formula V (copolymer, m : n :: 8 : 2).
Examples
The invention will now be illustrated with the help of examples. The examples are by way of illustrations only and in no way restrict the scope of invention.
p-Methoxy cinnamic acid was obtained from Galaxy Surfactants Ltd., Mumbai, p-dimethylamino benzoic acid was purchased from Nagase Chemical Co., Japan, N,N-dimethyl propyl diamine from BASF, A^-isopropyl acrylamide, vinyl benzyl chloride from Seimi, Japan. DMF, r-butanol, methylene chloride, thionyl chloride, acrylic acid and acetone were purchased from S. D. Fine Chem, Mumbai.
Example I
Process for preparation of cationic polymer of Formula I; wherein ArCO = p-methoxy cinnamoyl, R2 = -H, R3 = isopropyl; mole ratio, m : n :: 8 : 2 :
This polymer was synthesised by following three steps;
(a) Preparation of p-methoxy cinnamidopropvldimethylamine :
Ethyl p-methoxy cinnamate (206.0 g, 1.0 mole), A^,A/^-dimethylpropyldiamine (306.0 g, 3.0 mole) and sodium methoxide (2.0 g) were charged in a pressure reactor. The air inside the reactor was flushed out by purging of nitrogen. The reaction mixture was then stirred at 180°C (this generated pressure of 18 kg / cm^) for 36 hours when p-methoxy cinnamidoalkylamine is formed. The progress of reaction was monitored by disappearance of ethyl p-methoxy cinnamate on chromatography (TLC and HPLC). The TLC was performed on aluminium coated silica gel plates (Merck - 60-F-254) and viewed with a UV lamp at 254 nm. HPLC was performed using reversed phase technique on a C-18 bonded (octadecyl silane) column and 60 % v/v aqueous methanol as mobile phase (1.0 ml / min) and detection at 280 nm.
The excess amine was removed under vacuum. The golden yellow solid (263.0 g) thus obtained had amine value of 220. Molar extinction coefficient, e, in methanol was found to be 24,224 at 290 nm.
ER in dichloromethane showed carbonyl stretching of amide at 1660 cm"' and NH stretching at 3300 cm"'.
'H NMR (300 MHz, CDCI3) : 6 1.73 (p, 2H, J = 6.6 Hz), 2.26 (s, 6H), 2.42 (t, 2H, J = 6.6 Hz), 3.45 (q, 2H, J = 6.0 Hz), 3.81 (s, 3H), 6.27 (d, IH, J = 15.6 Hz), 6.86 (d, 2H, J = 8.7 Hz), 7.43 (d, 2H, J = 8.7 Hz), 7.53 (d, IH, J = 15.6 Hz).
(b) Copolvmerisation of A^-isopropvl acrvlamide and vinyl benzvl chloride (m : n :: 8 : 2):
A solution of A^-isopropyl acrylamide (10.0 g, 88.8 mmol), vinyl benzyl chloride (3.37 g, 22.1 mmol) and AIBN (100 mg) in r-butanol (120 ml) was stirred under nitrogen blanket at 80°C for 12 hours. The polymer solution was concentrated to half of its volume using rotary evaporator under vacuum. The copolymer was precipitated by adding concentrated ^butanolic solution to stirred petroleum ether (1000 ml). The precipitated polymer was filtered and dried under high vacuum to yield 12.75 g (95 %) of white powder. Mv of the copolymer was found to be around 5 xlOl
IR (KBr): 1643 cm"' (carbonyl of amide), 3278 cm"' (-NH of amide).
'H NMR : (CDCI3, 300 MHz): 5 (broad signals at 0.89 to 1.6, 2.1, 4.45, 6.4 - 7.2). Showed total absence of signals due to vinylic protons of monomers.
(c) Quatemisation of p-methoxv cinnamidopropvldimethylamine with polv(N-isopropyl
acrylamide - c - vinyl benzyl chloride):
A mixture of copolymer of A/'-isopropyl acrylamide and vinyl benzyl chloride (3.68 g, 6.1 mmol of vinyl benzyl chloride) from the previous step (b),-methoxy cinnamidopropyldimethylamine (1.6 g, 6.1 mmol) in isopropanol (50 ml) was stirred under nitrogen at 80°C for 48 hours. The progress of reaction was followed by estimation of chloride ions. After quantitative liberation of chloride ions (0.38 %), the solvent from the reaction mass was removed using a rotary evaporator
to give pale yellow coloured powdery solid. This powder was further used for recording IR and NMR. It was redissolyed in water or propylene glycol to form 10 % solution. E'*icm of this quatemised copolymer was found to be 213 at Amax 296 nm.
^ IR (KBr): 1650 cm"', 3250 cm"' (broad).
'H NMR (D2O, 300 MHz) : 5 (broad signals at 1.05, 2.0 - 2.1, 2.9 - 3.1, 3.65 - 3.85, 6.4 - 7.6). After quatemisation there is significant increase in aromatic protons relative to aliphatic protons.
Substantivity and photoprotection efficacy to skin :
Photoprotection efficacy of the polymer of the present invention was estimated by measuring the melanin content by Mexameter-18. This device is manufactured by Courage-Khazaka Electronic Gmbh, Koln, Germany.
Aqueous solution (100 mg) containing 10 mg of polymer was applied to a marked area (15 cmO of forearm and the subject swam in the sea water for 30 minutes in midnoon. The melanin content of the protected skin and the unprotected skin of the forearm was measured. The melanin content of protected skin changed from 334 to 338 units on the Mexameter after the 30 minutes of swimming in the sea whereas the melanin content of the unprotected skin shot from 334 to 380 units on the Mexameter. After the 30 minutes of swimming, the applied polymer (10 mg) was extracted using cotton swabs soaked in ethyl alcohol. On analysing ethyl alcohol extracts spectrophotometrically, the substantivity to skin was found to be 200 \ig I cm2
Example II
Process for preparation of cationic polymer of Formula I; wherein ArCO = p-methoxy cinnamovl R^^RT = -Cr>R
