Hydrophobically modified hydroxyethylcellulose derivatives are known and described suitable to the use as thickeners of aqueous compositions.

For example in the US Patent 4,228,277 ethers of non-ionic cellulose derivatives with alkyl groups from C-^Q to C2 are described. The derivatives of hydroxyethylcellulose, hydroxypropyl cellulose, methylcellulose, hydroxypropylmethylcellulose, ethylhydroxyethyl- cellulose and methylhydroxyethylcellulose are cited as examples. In the European Patent Application 0 307 915 a modified hydroxyethyl¬ cellulose containing carboxymethyl groups, carboxyethyl groups and long hydrophobic chains was described. The relative substrates may be prepared by a treatment of cellulosic material with an alkylene oxide in an alkaline medium. To said substrates the hydrophobic chains are then linked. In order to give solubility in water to the structure and then in order to exploit its technological characteristics in an aqueous solution, it is necessary to link to the polysaccharidic chain some hydrophile units, represented in the cited cases by the hydroxyethyl groups, obtained by reaction with ethylene oxide. In a specific example, chemical cotton was reacted with ethylene oxide in a medium containing sodium hydroxide and consisting of water, tert- butanol and acetone. The product obtained by this treatment was then reacted with cetyl bromide to obtain the modification with the hydrophobic chains. The described process turns out to be rather complex, expensive and

dangerous as the ethylene oxide shows marked flam ability, explosiveness and toxicity characteristics.

The need to have a simpler, economical and danger free process available was therefore felt. Moreover the need is felt to have cellulose derivatives available having hydrophobic chains, different from hydroxyethylcellulose and possibly having improved applicative characteristics.

SUMMARY

The present invention refers to cellulose ionic derivatives having long chain hydrophobic groups, which show improved characteristics of thickeners than the prior art ones and are prepared by a simpler and more economical process than the known cellulose hydrophobic derivatives.

The derivatives according to the present invention consist of ethers of carboxymethylcellulose having long chain substituents of formula (I)

R-(A) _m -(B) _n - (I) wherein:

R = linear or branched alkyl or alkenyl group, A = 0-C H2 _D oxyalkylene group, linear or branched with p = 2-4,

B = -0-CH ₂ -CH(0H)-CH ₂ -, or B = -CH(0H)-CH ₂ - only when m = 0, m = 0-20, n = 0-1 and having a degree of substitution (alkyl D.S.) ranging from

0.01-10 to 2-10 , wherein the degree of substitution is intended as the average number of hydroxyls substituted by long chain on each anhydroglucosidic unit.

Said derivatives turn out to be suitable for the use as thickening

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additives for aqueous compositions, particularly for paints, plasters and cosmetics.

Said derivatives are prepared preferably by direct reaction of carboxymethyl cellulose with a suitable agent able to introduce the long chain group represented in the formula (I) , in an environment consisting of water and an organic solvent, in presence of a base and if necessary of a phase transfer catalyst, in a nitrogen atmosphere. Illustrative conditions of this preparation process are reported in the following description. BRIEF DESCRIPTION OF THE FIGURES

The figures 1, 2 and 3 represent the rheological behaviour of aqueous solutions containing some products according to the invention. In particular, figures 1, 2 and 3 refer to solutions containing the products of examples 2, and 6 respectively. The curves indicated with H ₂ 0 refer to the aqueous solution of the product whereas the curves indicated with SDS refer to aqueous solutions of the same product containing dodecylsulfate. In the figures the viscosity ■) (o) as a function of the shear rate is represented. DETAILED DESCRIPTION OF THE INVENTION

The characteristics and the advantages of the ethers of the carboxymethyl cellulose with long chain groups according to the present invention, of the process for their preparation and their use, will be mostly pointed out during the following detailed description. The ethers according to the present invention are prepared by reaction of carboxymethyl cellulose, eventually not isolated from the reaction mixture obtained during the preparation of the carboxymethyl cellulose

itself, with a long chain agent having an efficient leaving group, for example an halogen, an oxygen of an oxyranic group or an alkylsul- fonyloxy or arylsulfonyloxy group, under the experimental conditions described below, or they are prepared by carboxymethylation on a previously substituted cellulose bearing groups having formula (I) or they are prepared adding simultaneously carboxymethylating agents and agents having formula (II) in analogous reaction conditions. According to a preferred method the carboxymethyl cellulose is reacted with an agent selected in the group of the compounds having the following general formula (II)

R-(A) _m X (II) wherein m = 0-20

0 0

/I /I X = Cl. Br, 0S0 ₂ R-\ 0CH2CHCH2, or X = CHCH2 only when m = 0, wherein

R = C1-C3 alkyl group, C6-C12 aryl group or C7 arylalkyl group, R = linear or branched, alkyl or alkenyl group A = 0-C H _2D oxyalkylene group, linear or branched with p = 2-4. Several kinds of carboxymethyl cellulose may be used and carboxymethyl cellulose having a degree of substitution in carboxymethyl groups (D. S.) ranging from 0.5 to 1.2, determined according to the ASTM D1439 method, are preferred. The reaction medium consists of water and of an organic solvent selected from the group consisting of an alcohol from Ci to C _/ , in particular of ethanol, isopropanol and tert-BuOH or toluene or acetone. The carboxymethyl cellulose is reacted with said agent in presence of

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a base and, if necessary, of a phase transfer catalyst at a temperature ranging from 20 to 100 "C in a nitrogen atmosphere. The reaction mixture is neutralized with an inorganic or organic acid and the product is separated by filtering, eventually after precipitation by addition of a solvent in which the product is insoluble, for example of acetone. The obtained product is washed with an organic solvent for example ethanol, vacuum dried and eventually submitted to purification by extraction with organic or aqueous organic solvent. The base used in the reaction is selected from the group consisting of NaOH, LiOH, K ₂ C0 and N-ethyl-diisopropylamine while the phase transfer catalyst is an ammonium or quaternary phosphonium salt or a compound containing polyoxyethylene or polyoxypropylene groups and preferably it is tetramethylammonium chloride (TMAC1) . The ratio by weight between carboxymethyl cellulose and the agent having formula (II) ranges from 0.5:1 to 350:1 and the ratio by weight between carboxymethyl cellulose and said base is ranging from 0. 1 to 3500:1. The products according to the present invention have a degree of substitution (alkyl D.S.) ranging from 0.01-10 ^-2 to 2-10 ^"1 , wherein the degree of substitution is intended as the average number of hydroxyls substituted by long chain on each anhydroglucosidic unit, determined by NMR, computing the ratio of the integrals of the peaks ascribed to the R alkyl groups hydrogens with respect to those ones of the glucosidic chain hydrogens.

Said products have high associative properties as proved by the technological tests reported below.

Thanks to their characteristics, the products according to the present invention may be advantageously used as additives for aqueous compositions to be thickened, particularly in the fields of paints, plasters and cosmetics. The amount of product used for this purpose varies from 0.5 to 5% by weight with respect to the aqueous composition. For illustrative and not limitative aim of the invention the following experimental examples are reported. The assay of the used carboxymethyl cellulose has been determined according to the ASTM D1439 method. EXAMPLE 1

Alkylation of carboxymethyl cellulose (D.S. 0.55) with 1- epoxyoctadecane.

Carboxymethyl cellulose (5-0 g, assay 99$). water (25-0 g) and tert- butanol (43-3 g) . have been loaded into a three necked, rounded bottom reactor, equipped with mechanical stirrer and condenser.

The oxygen has been removed by a nitrogen flux passage through the system for minutes and then lithium hydroxide monohydrate (2.0 g) and 1-epoxyoctadecane (3-7 g) have been added. The reaction mixture has been heated at 90 °C and stirred for 4 hours under nitrogen pressure (about 2 bar) . The mixture has been then left to cool at room temperature in an hour period, then it has been neutralized by hydrochloric acid 14% w/w (about 13-3 g) and purified by extraction with dichloromethane (2 x 100 ml). The product has been precipitated from the aqueous layer by pouring in acetone (300 ml) with vigorous stirring, filtered, washed with ethanol (3 x 50 ml) and vacuum stove dried at 50 °C for 15 hours on P2 c- 4.2 g of dried product have been obtained.

A sample of the dried product (3-8 g) has been purified by extraction with dichloromethane (400 ml) for 4 hours using a Soxhlet apparatus. The resulting product has been dried in a vacuum stove at 50 °C on P ₂ 0c for 15 hours obtaining 3-7 S of a product having alkyl D.S. of 0.016-10 ^~2 , determined by NMR. EXAMPLE 2

Alkylation of carboxymethyl cellulose (D.S. 0.55) with 1- mesyldocosane. Carboxymethyl cellulose (5-0 g, assay 99%) » water (25-0 g) and toluene (14.9 g) have been loaded into a rounded bottom reactor equipped with a mechanical stirrer. The oxygen has been removed by a nitrogen flux passage through the system, a solution of tetramethylammonium chloride (190 mg) in water (1.0 g) has been added, the mixture has been heated at 90 °C and a solution of 50% by weight (15-3 g) sodium hydroxide has been added. After 30 minutes a solution of 1-mesyldocosane (5-0 g) in toluene (22.4 g) has been added. The mixture has been stirred for 3 hours at 90 °C under a nitrogen flux and then left to cool at room temperature in an hour period, neutralized with hydrochloric acid l % w/w (about 33 g) and purified by extraction with dichloromethane (2 x 100 ml).

The product has been precipitated from the aqueous layer by pouring in acetone (300 ml) with vigorous stirring, filtered, washed with ethanol (3 x 5 ml) and vacuum stove dried at 50 °C for 15 hours on P _{2 c} . 4.0 g of product having alkyl D.S. of 0.31'10 have been obtained. EXAMPLE 3

Alkylation of carboxymethyl cellulose (D.S. 0.55) with 1- bromodocosane.

Carboxymethyl cellulose (10.0 g, assay 99%). water (20 g) and tert- butanol (4.0 g) , have been loaded into a jacketed stainless alloy reactor previously heated at 90 "C. The oxygen has been removed by a nitrogen flux passage through the system for 5 minutes. After 15 minutes a solution of lithium hydroxide monohydrate (4.0 g) in water (5.0 g) has been added and after 10 minutes a solution of 1- bromodocosane (4.8 g) in tert-butanol (15.8 g) has been added. The reaction mixture has been stirred for 3 hours at 90 °C under nitrogen pressure ( 2 bar) and then it has been left to cool at room temperature for an hour period, neutralized with hydrochloric acid 1 % w/w (about 13.3 g) and purified by extraction with dichloromethane (2 x 100 ml) .

The product has been precipitated from the aqueous layer by pouring in acetone (300 ml) with vigorous stirring, filtered, washed with ethanol (3 x 50 ml) and vacuum stove dried at 50 °C for 1 hours on P ₂ 0j-. 8.6 g of product have been obtained.

The product has been purified by extraction with dichloromethane (400 ml) for 4 hours using a Soxhlet apparatus. The product has been dried in a vacuum stove at °C on P ₂ 0j- for 15 hours obtaining 7-9 g of a product having alkyl D.S. of 0.98-10 ^"2 . EXAMPLES FROM 4 TO 18

The examples from 4 to 18 have been carried out according to the process described in the Example 3■ The substances used for the reaction, the operative conditions, the obtained amounts of product and the relative characteristics (alkyl D.S.) are reported in Table 1.

TABLE 1 REACTION OF CARBOXYMETHYL CELLULOSE (CMC) WITH 1-BROMODOCOSANE (BrD)

Ex. DS of CMC CMC BrD LiOH NaOH Yield Alkyl DS No. (g) (g) (g) (g) (g) 10 ^"2

4 0.55 10 9-6 4 8/7-2 1.2

5 0.55 10 1.2 4 7-7/5 0.33

6 0.55 10 2.4 4 8.4/5.6 0.09

7 0-55 10 4.8 4 8.6/7.9 0.98

8 0.55 5 9-6 4 4.8/4.8 2.7

9 0.55 10 4.8 6.6 8.8/4.6 1.13

10 0.55 5 4.8 7 4.3 0.79

11 0.85 5 4.6 1.8 4.4/2.9 0.16

12 0.75 10 8.6 3-7 4.4/3.6 1.3

13 1.0 10 8.1 6.3 8.8/4.8 1.7

14 1.0 15 12.2 9.5 121.2 0.88

15 1.0 15 3 9-5 /14.1 2.1

16 1.0 15 1-5 9-5 /16.0 2.2

17 1.0 10 0.5 0.08 0.65

18 1.0 10 0.03 0.005 0.095

All the reactions are carried out at 90 °C for three hours in 50 ml of a solution 1:1 by weight of ter-BuOH and water. LiOH = Lithium hy¬ droxide monohydrate; NaOH = sodium hydroxide 98%. LiOH and NaOH are added as 5 weight/volume aqueous solutions. CMC = commercial CMC having assay of 99%- The reaction of the Example 11 is carried out in a mixture 1:1 by weight of water and toluene, with the addition of 0.13 g of tetramethylammonium chloride. In the yield column the first digit refers to the crude precipitated product, the second digit

refers to the product purified by extraction with CH ₂ C1 ₂ in Soxhlet. EXAMPLE 19

Alkylation of carboxymethyl cellulose (D.S. 0.75) with 2-[dodecyloxy- methylen]oxirane. Carboxymethyl cellulose (10.0 g, assay 99%). water (20.0 g) and tert- butanol (4.0 g) , have been loaded into a stainless steel reactor equipped with mechanical stirrer and previously heated at 90 °C. The oxygen has been removed by a continuous nitrogen flux through the system for minutes. After 1 minutes a solution of sodium hydroxide (6.6 g) in water (5-0 g) has been added and after 10 minutes a solution of dodecyl glycidyl ether (5-3 g) in tert-butanol (15-8 g) has been added. The reaction mixture has been stirred for 3 hours at

90 °C under nitrogen pressure (about 2 bar). Then the mixture has been cooled at room temperature for one hour period, neutralized with HCl 14% w/w (about 26.6 g) and purified by extraction with dichloromethane (2 x 100 ml) .

The product has been precipitated from the aqueous layer by pouring in acetone (300 ml) with vigorous stirring, filtered, washed with ethanol (3 x 50 ml) and vacuum stove dried at 50 °C for 15 hours on P ₂ 0c to give 10.1 g of product.

A sample of this product (8.0 g) has been purified by extraction with dichloromethane (400 ml) for 4 hours in a Soxhlet apparatus. The resulting product has been dried in a vacuum stove at 50 °C for 15 hours on _{? r} ; to give 7-3 g of a compound having alkyl D.S. of 5-6- 10 ^"2 . EXAMPLE 20 Alkylation of carboxymethyl cellulose (D.S. = 0.9) with 2-

[docosiloxymethylen]oxyrane.

The carboxymethyl cellulose (60 g) was put into a three necked, rounded bottom, glass reactor equipped with mechanical stirring. The reactor was set under vacuum and subsequently in a nitrogen atmosphere (p= 1 bar) . Throughout the reaction the operations were carried out witha nitrogen flux.

Tertbutanol (60 g) was added, leaving it under stirring for 10 minutes. H 0 (240 g) was added, leaving it under stirring for 20 minutes. Then, a solution prepared dissolving NaOH (0.3 g) in H 0 (30 g) was added, leaving it under stirring for 30 minutes. A solution prepared hot dissolving docosiloxy-methyloxyrane (6.4 g, assay 87%. prepared from epichlorohydrin and commercial docosanol according to N.

Takaishi et al., JA0CS, 1988. 65. 1299) in tert-butanol (95 g) was then added. The reaction mixture was heated at 75 °C for 3 hours, always under vigorous stirring; then it was left to cool to room temperature and neutralized with HCl 1M (about 7-5 ml)- Propan-2-ol (200 ml) was then added to precipitate the reaction product.

The solid was filtered on a glass funnel with porous septum, washed with ρropan-2-ol (2 x 1 0 ml), with acetone (2 x 100 ml), dried in a stove at 80 °C overnight and milled. 56 g of dried product have been obtained.

A sample of dried product (5 g) has been purified by the following procedure. The solid was put into a 100 ml Erlenmeyer flask and it was suspended, with magnetic stirring, in propan-2-ol (50 ml). The reaction mixture was heated to 65 °C and it was left under stirring at this temperature

for 30 minutes. The suspension was hot filtered on a glass funnel with porous septum, the solid was taken back in propan-2-ol (50 ml) and the suspension was put again at 65 °C for 30 minutes, repeating the just described procedure twice. Then, the solid was washed with aqueous ethanol (80% w/w), until the washing waters contain no more chlorides. The solid was washed with acetone (2 x 15 ml), it was dried in a stove at 110 °C overnight and it was milled. In this way, 4.1 g of purified product, having alkyl D.S. (C ₂ ) equal to 4.3 x 10 ^" , determined by NMR, were obtained. The Examples from 21 to 23 were carried out according to the process described in the Example 20, but using the different epoxidic alkylating agents which have been prepared reacting the suitable commercial R-0H alcohols with epichlorohydrin, according to N. Takaishi et al. , JA0CS, 1988, 65, 1299. obtaining the alkyl DS reported in table 2.

TABLE

EXAMPLE ALKYLATING AGENT R-OH Alkyl D.S.

21 2-[0ctadecyl-deca(oxy-1.2-ethandiyl)- Brji 76 ^R l^-lO ^-1 oxymethylen]oxyrane

22 2-[Dodecyl-tetra(oxy-l,2-ethandiyl)- Brji 30 ^R 9- 10 ^" ^ oxymethylen]oxyrane

23 2-[Hexadecyloxy-methylen]oxyrane Cetyl alcohol 1.6-10

R = Registered trade mark of ICI

EXAMPLE 24

Etherification of cellulose with monochloroacetic acid and subsequent alkylation with 2-[octadecyl-deca(oxy-1 ,2-ethandiyl) - oxymethylenjoxyrane. Alkali Phase

Propan-2-ol (462 g) , aqueous ethanol (63-4 g, 80% w/w), water (66.6g) were put in a four necked, rounded bottom, glass flask, equipped with mechanical stirring. The flask was placed under vacuum and subsequently in nitrogen atmosphere (p = 1 bar). Throughout the reaction the operations were carried out with a nitrogen flux.

After 5 minutes of stirring NaOH in beads (30 g) was added. After 5 minutes of stirring finely milled cellulose (49-12 g) was added. The reaction mixture was left under stirring for 1 hour. Etherifications: A solution containing monochloroacetic acid (33-6 g) , propan-2-ol (18 g) , aqueous ethanol (2.6 g, 80% w/w), water (1.8 g) was then added in the flask. It was left under stirring at T = 75 °C for 1 hour, left

cooling under stirring for minutes and acetic acid (1.1 g, 80% w/w) was then added. It was left under stirring for 10 minutes and then it was filtered on a porous glass filtration funnel. It was purified with aqueous ethanol (70% w/w) until chloride ion is no more detectable in the washing solution. The obtained solid was dried in a stove at 80 °C overnight and milled. 3 g of milled product have been obtained. (Alkyl D.S. 1.8.10 ^"3 , NMR)

The viscosity in solution of the products (obtained in the example 24, 2 e 26) has been estimated against a "blank" prepared submitting the cellulose to the treatment described in the Examples 24-26, but without the addition of the epoxidic alkylating reagent. The results are summarized in the Table 3-

TABLE 3

EXAMPLE BROOKFIELD RVT VISCOSITY, 20 "C. 20rpm.(l)

Blank 8,600 Cp 24 6,750 Cp

25 10,100 Cp 26 12,900 Cp

(1) Measured on a aqueous solution containing 1% w/w of the product. RHE0L0GICAL BEHAVIOUR In order to estimate the applicative characteristics of the products according to the present invention the Theological behaviour of

aqueous solutions containing the products obtained as described in the Examples 2, 5 and 6 has been studied. Aqueous solutions containing 4% by weight of said products and aqueous solutions containing 4% by weight of said products and sodium dodecylsulfate (Fluka, 98%) have been prepared in amounts such that they reached a concentration equal to 1-10 ^"5 M (2.8-10 ^"2 % by weight).

On said solutions the dynamical viscosity has been determined according to the following method. A rotational viscometer controlled by an electronic computer (Rheometrics RFS 8500) has been used and the viscosity of the solutions has been measured in the rotation range between 0.05 and 100 s , varying the rotation speed in a continuous and uniform manner in a 4 minutes time and measuring in a continuous manner the viscosity change. The solution temperature has been kept constant at 20 °C.

The Theological curves of said solutions are reported in the Figures 1, 2 and 3. for the products of the Examples 2, and 6 respectively. In each Figure the Theological curve of the aqueous solution of the product (indicated with H ₂ 0) and the rheological curve of the aqueous solution of the product containing sodium dodecylsulfate (indicated with SDS) are reported.

In the Figures the viscosity ^' j (o) (expressed in Pa-s) as a function of the shear rate Y (expressed in s ) was represented. As one may notice from the Figures the presence of sodium dodecylsulfate as a surface-active agent causes a marked increase of the viscosity of the solution thus showing the associative properties of the products according to the present invention, determined from

the hydrophobic groups linked by ether linkages to carboxymethyl cellulose. The utility of this behaviour and its dependence from the presence of long alkyl chains on a hydrosoluble polymeric structure, was also cited in Polymers, ACS Symposium Series 467, Chap. 14. ed. by S. W. Shalaby, C. L. McCormick and G. B. Butler, and in EP 281360 (1988). Thanks to these characteristics, the ethers of be successfully used as thickening additives for aqueous compositions, to which they are added in amounts from 0. to 5% by weight.