Associative acrylic thickening agent containing polyglycerols and its use to increase the open time of thin or thick films

Abstract

The present invention relates to new acrylic associative thickening agents which, when polymerized in the presence of particular polyglycerols, ultimately result in an increase of the open time of the paint or of the thick coating in which they are incorporated. By so doing, painters and applicators will have more time to work the paint layers gradually or to correct imperfections such as paint droplets, traces of brushes and filling-knives.

Claims

1. A method for manufacturing an associative thickening agent, the method comprising polymerizing, in an aqueous dispersion, monomers a), b) and c): a) (meth)acrylic acid, b) an ester of (meth)acrylic acid, and c) a monomer having a formula R-(EO).sub.p(PO).sub.qR, where: p and q designate integers of less than or equal to 150, at least one of which is non-zero, EO and PO designate respectively ethylene oxide and propylene oxide, R designates a polymerizable group, and R designates a hydrophobic group comprising from 6 to 36 carbon atoms, wherein the polymerizing is performed in the presence of at least one polyglycerol of formula (I) and in the presence of a surfactant other that the polyglycerol of formula (I) ##STR00003## where: n represents an integer or decimal greater than 1 and equal to or lower than 10 and designates an average degree of polymerization; and R designates hydrogen, an ester group functionalized by an alkyl group having from 8 to 22 carbon atoms, or an alkyl group having from 8 to 22 carbon atoms, to obtain an associative thickening agent.

2. The method according to claim 1, comprising: (i) introducing into water the polyglycerol of formula (I) and the surfactant other than the polyglycerol of formula (I), to form a mixture, then (ii) increasing a temperature of the mixture, then (iii) introducing a polymerization initiator to the mixture, and then (iv) adding the monomers a), b) and c) to the mixture, optionally in combination with water and an additional surfactant.

3. The method according to claim 1, wherein the surfactant other than the polyglycerol of formula (I) is an anionic surfactant, a non-ionic surfactant, or a mixture thereof.

4. The method according to claim 1, wherein the surfactant other than the polyglycerol of formula (I) is present in an amount of 1% to 5%.

5. The method according to claim 1, wherein, compared to a total weight of the associative thickening agent: 20% to 60% by weight of the (meth)acrylic acid a), 40% to 80% of the ester of (meth)acrylic acid b), 0.5% to 25% of the monomer having a formula R-(EO).sub.p(PO).sub.qRc), and 0.1% to 10% by weight of the polyglycerol of formula (I) d), are present during the polymerizing, where the sum of the percentages a), b), c) and d) is equal to 100%.

6. The method according to claim 1, wherein R designates a hydrophobic group having from 12 and 36 carbon atoms.

7. The method according to claim 1, wherein the obtained associative thickening agent has an average molecular mass by weight of between 20,000 g/mole and 1,000,000 g/mole, as measured by GPC.

8. The method according to claim 1, wherein the monomer a) is methacrylic acid.

9. The method according to claim 1, wherein the monomer b) is ethyl acrylate.

10. The method according to claim 1, wherein the surfactant other than the polyglycerol of formula (I) is at least one member selected from the group consisting of sodium dodecyl sulfate, dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, an ether of a fatty alcohol, an ether of polyoxyethylene glycol, and an ester of polyoxyethylene glycol.

11. The method according to claim 1, wherein q=0 and 0<p<80.

12. The method according to claim 1, wherein R is a methacrylate group.

13. The method according to claim 1, wherein R is a methacrylurethane group.

14. The method according to claim 1, wherein: the monomer a) is methacrylic acid; the monomer b) is ethyl acrylate; q=0 and 0<p<80; R is a methacrylate group or a methacrylurethane group; R designates a hydrophobic group having from 12 and 36 carbon atoms; and the surfactant other than the polyglycerol of formula (I) is at least one member selected from the group consisting of sodium dodecyl sulfate, dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, an ether of a fatty alcohol, an ether of polyoxyethylene glycol, and an ester of polyoxyethylene glycol.

Description

EXAMPLES

(1) In each of the following examples, the molecular mass of the associative thickening agents is determined by GPC.

(2) Synthesis of the said thickening agents is well known to the skilled man in the art, and reference may be made in particular to the various documents cited in the Application as background concerning HASE technology.

(3) The paints are formulated using the methods well known to the skilled man in the art. All the Brookfield viscosities of the paint formulations are measured at 25 C.

(4) Finally, the open time of the paints is determined using 2 techniques, depending on whether a thin film or a thick film of moist paint is applied.

(5) When a thin film is concerned, the open time is measured by means of a test undertaken in a controlled atmosphere (climate-controlled room), where the time when the first layer is no longer diluted is determined on a freshly applied film, by successive repeats.

(6) In concrete terms, in a climate-controlled room with the temperature set at 231 C. and with 50% relative humidity, 240 m of a paint having cured for at least 24 h is applied using a multi-layer applicator on a black Leneta card (wet abrasion card). The chronometer is then started and this card is attached with adhesive tape to a Placoplatre plate; a check is made that the length of the adhesive strip is equal to the width of the card.

(7) After 15 min. one begins to sweep the surface of the still-wet film with a 30 brush from left to right over a 3 cm strip; a proportion of the paint is thus moved with the brush to the unpainted surface on the right.

(8) This operation is undertaken every minute, taking care to use a brush which is always dry, and always to apply the same pressure.

(9) The sweeping is stopped when it is no longer possible to move paint rightwards. From that point forth, the Leneta card moves when the brush moves over it: this is the instant when the film can no longer be soaked; consequently the brush no longer slides. This instant is the open time.

(10) When a thick film is concerned, the open time is determined indirectly by means of a spreading test.

(11) In a climate-controlled room with a temperature set at 231 C. and with hygrometry controlled at 505%, a determined quantity in terms of shape and volume of the product to be tested is applied on a Placoplatre plate using a jig.

(12) This jig consists of a trapezoid-shaped stainless steel frame (with no background) of a thickness ranging from 0 to 14 mm, with a large base B=72 mm, a small base b=58 mm and a height h=150 mm. The depth is 0 mm for B and 14 mm for b and varies in linear proportion. This jig is attached to the Placoplatre plate, with the larger base upward.

(13) The product is placed inside until the jig is filled completely. The surplus product is removed by levelling-off using a wall scraper of width greater than B, so as to position the product perfectly and such that it perfectly follows the shape of the jig.

(14) The latter is then removed (mould release), taking care to leave nothing on the edges of the frame. The product settles to a greater or lesser degree during the drying time. The spreading amplitude is measured in the widest location 24 hours after application. It is expressed as a percentage of the additional spreading proportion relative to the width of the jig. It is considered that the larger the amplitude the greater the open time of the thick film.

Example 1

(15) This example illustrates the synthesis and use of the various associative thickening agents according to the invention (presence of polyglycerol during the synthesis), or outside the invention (without additives, with glycerol used during the synthesis or as a formulation agent, with polyglycerol added as a formulation surfactant).

(16) The use in question occurs in a water-based paint, the constitution of which is given in table 1, the figures indicate the mass in grams of each constituent.

(17) TABLE-US-00001 TABLE 1 Water 294.0 Ammonia 31% 2.0 Ecodis 40 (Coatex) 3.0 Acticide MBS (Thor) 2.0 Byk 34 (Byk) 1.0 TiONA 568 (Cristal) 41.0 Durcal 5 (Omya) 328.0 Omyacoat 850 OG (Omya) 215.0 Axilat DS 910 (Hexion) 82.0 Butyl diglycol 20.0 Thickening agent subject to testing 12.0 * * the value of 12 grams is equal to the mass of an emulsion containing 30% by dry weight of polymer (except for test n 4 which uses 9.0 grams by dry weight of a commercial thickening agent in powder form).
Test No 1:

(18) This test illustrates a HASE thickening agent outside the invention, polymerized with a conventional surfactant.

(19) This thickening agent results from the synthesis, expressed as a % by weight of the monomers, of: a) 37.4% of methacrylic acid, b) 54.3% of ethyl acrylate, c) 8.3% of a monomer of formula (I), with: R designates the methacrylate group, q=0, p=25, R designates the hydrophobic group resulting from oxo alcohol having 16 carbon atoms.

(20) In a 1-liter reactor, 485.4 grams of bipermuted water and 6.66 grams of sodium dodecyl sulphate and 11.5 g of non-ionic surfactant, which is isotridecyl alcohol condensed with 3 molecules of ethylene oxide, are weighed. The base of the tank is then heated to 72 C.2 C.

(21) During this time, a pre-emulsion is prepared by weighing the following in a beaker: 149 grams of bipermuted water, 2.33 grams of sodium dodecyl sulphate, 111.33 grams of methacrylic acid, 161.45 grams of ethyl acrylate, 24.6 grams of macromonomer of formula (I).

(22) The mass of non-ionic surfactant therefore accounts in this case for 3.7% of the total mass of the manufactured polymer.

(23) 0.95 gram of ammonium persulphate is then weighed, diluted in 10 grams of bipermuted water for the first catalyst, and 0.095 gram of sodium metabisulphite diluted in 10 grams of bipermuted water for the second catalyst. When the base of the tank is at the required temperature both catalysts are added, and polymerization is effected for 2 hours at 76 C.2 C., with simultaneous addition of the pre-emulsion. The pump is rinsed with 20 grams of bipermuted water, and is fired for 1 hour at 76 C.2 C. Finally it is cooled to ambient temperature, and the dispersion obtained in this manner is filtered.

(24) Test No 2:

(25) This test illustrates a HASE thickening agent outside the invention, polymerized with a conventional surfactant.

(26) This is the same thickening agent as that of test no 1, in which the non-ionic surfactant has been replaced, in mass terms, by nonylphenol condensed with 4 molecules of ethylene oxide.

(27) Test No 3:

(28) This test illustrates a HASE thickening agent outside the invention, polymerized with a conventional surfactant.

(29) This is the same thickening agent as that of test no 1, in which the non-ionic surfactant has been replaced, in mass terms, by a surfactant sold by the company Clariant under the name Polyglykol B11/150.

(30) Test No 4:

(31) This test illustrates an HEC-type thickening agent outside the invention which is Natrosol 250 HR (Aqualon); it is used as a reference.

(32) Test No 5:

(33) This test illustrates a thickening agent outside the invention, formulated in water with the introduction of glycerol after polymerization.

(34) The thickening agent is that of test no 1, polymerized according to the technique described in test no 1.

(35) In the final solution with 30% by dry weight of active matter, 3% by dry weight of glycerol from the company Oleon relative to the dry weight of polymer is introduced.

(36) Test No 6:

(37) This test illustrates a thickening agent outside the invention, formulated in water with the introduction of polyglycerol after polymerization.

(38) The thickening agent is that of test no 1, polymerized according to the technique described in test no 1.

(39) In the final solution with 30% by dry weight of active matter, 3% by dry weight, relative to the dry weight of polymer, of polyglycerol-3 of formula (I), with RH, and n=3 sold by the company Solvay, is introduced.

(40) Test No 7:

(41) This test illustrates a thickening agent outside the invention, formulated in water with the introduction of polyglycerol after polymerization.

(42) The thickening agent is that of test no 1, polymerized according to the technique described in test no 1.

(43) In the final solution with 30% by dry weight of active matter, 3% by dry weight, relative to the dry weight of polymer, of hydrophobic polyglycerol, which is Chimexane NB of formula (I) with RC.sub.18H.sub.35 and n=2 sold by the company Chimex, is introduced.

(44) Test No 8:

(45) This test illustrates a thickening agent outside the invention, polymerized in the presence of glycerol.

(46) The thickening agent is that of test no 1, polymerized according to the technique described in test no 1, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by glycerol from the company Oleon.

(47) Test No 9:

(48) This test illustrates a thickening agent according to the invention, polymerized in the presence of polyglycerol-3, which is the one used in test no 6.

(49) The thickening agent is that of test no 1, polymerized according to the technique described in test no 1, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by the polyglycerol-3 of test no 6.

(50) Test No 10:

(51) This test illustrates a thickening agent according to the invention, polymerized in the presence of Chimexane NB, which is the one used in test no 7.

(52) The thickening agent is that of test no 1, polymerized according to the technique described in test no 1, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by the Chimexane NB of test no 7.

(53) For each of these tests the Brookfield viscosities were determined at 25 C., at 10 and 100 revolutions per minute, at instant t=1 day (.sub.10 IJ, .sub.100 IJ), where instant t=0 is the time of manufacture of the paint.

(54) The open time of the paint expressed in minutes using the protocol set out in the preamble for a thin film is also determined, at instant t=1 day.

(55) The results are shown in table 2.

(56) TABLE-US-00002 TABLE 2 Test n 1 2 3 4 5 REFerence OI OI OI REF OI Outside Invention INvention .sub.10 1J (mPa .Math. s) 6,600 6,500 6,800 5,500 5,600 .sub.100 1J (mPa .Math. s) 2,600 2,700 2,800 2,000 2,200 open time (min.) 33 33 33 35 34 Test n 6 7 8 9 10 REFerence OI OI OI IN IN Outside Invention INvention .sub.10 1J (mPa .Math. s) 6,200 6,400 9,100 10,500 5,000 .sub.100 1J (mPa .Math. s) 2,700 2,800 3,600 3,800 2,100 open time (min.) 34 34 34 36 37

(57) Tests no 1 to 3 demonstrate that the choice of a habitual polymerization surfactant has no influence on the open time.

(58) When glycerol or polyglycerols are used as the formulation surfactant (tests no 5 to 8), the influence on the open time is minimal.

(59) Test no 4 demonstrates that a modified cellulose indeed enables the open time to be increased; a substantial mass of it must however be used (9 grams of active product, compared to 3.6 grams of active product of the 12 grams of emulsion at 30% dry extract) to obtain levels of viscosity comparable to those obtained with HASE-type emulsions.

(60) Only tests no 9 and 10 (use of polyglycerols during the polymerization step) lead to a significant increase of the open time, with unchanged thickening efficacy. The greatest open time is obtained for test no 10, which is the preferential variant of the invention.

Example 2

(61) This example illustrates the synthesis and use of different associative thickening agents, according to the invention (presence of polyglycerol during the synthesis), or outside the invention (without addition of polyglycerol during the synthesis).

(62) The use occurs in a water-based paint, the constitution of which is given in table 3; the figures indicate the mass in grams of each constituent.

(63) TABLE-US-00003 TABLE 3 Water 281.0 Ammonia 31% 2.0 Ecodis 40 (Coatex) 3.0 Acticide MBS (Thor) 2.0 Byk 34 (Byk) 1.0 TiONA 568 (Cristal) 41.0 Durcal 5 (Omya) 328.0 Omyacoat 850 OG (Omya) 215.0 Axilat DS 910 (Hexion) 82.0 Butyl diglycol 20.0 Thickening agent subject to testing 24.0 * * the value of 24 grams is the mass of an emulsion containing 30% by dry weight of polymer.
Test No 11:

(64) This test illustrates a HASE thickening agent outside the invention, polymerized with a conventional surfactant.

(65) This thickening agent results from the synthesis, expressed as a % by weight of the monomers, of: a) 33.7% of methacrylic acid, b) 59.4% of ethyl acrylate, c) 6.9% of a monomer of formula (I), with: R designates the methacrylate group, q=0, p=25, R designates the branched hydrophobic group with 16 carbon atoms.

(66) In a 1-liter reactor, 288 grams of bipermuted water, 3.5 grams of sodium dodecyl sulphate and 11.5 g of non-ionic surfactant, which is isotridecyl alcohol condensed with 3 molecules of ethylene oxide, are weighed. The base of the tank is then heated to 72 C.2 C.

(67) During this time, a pre-emulsion is prepared by weighing the following in a beaker: 285 grams of bipermuted water, 3.5 grams of sodium dodecyl sulphate, 102.06 grams of methacrylic acid, 180 grams of ethyl acrylate, 21 grams of macromonomer of formula (I), 0.64 gram of dodecylmercaptan.

(68) The mass of non-ionic surfactant therefore accounts in this case for 3.6% of the total mass of the manufactured polymer.

(69) 0.95 gram of ammonium persulphate is then weighed, diluted in 10 grams of bipermuted water for the first catalyst, and 0.095 gram of sodium metabisulphite diluted in 10 grams of bipermuted water for the second catalyst. When the base of the tank is at the required temperature both catalysts are added, and polymerization is effected for 2 hours at 76 C.2 C., with simultaneous addition of the pre-emulsion. The pump is rinsed with 20 grams of bipermuted water, and is fired for 1 hour at 76 C.2 C. Finally it is cooled to ambient temperature, and the dispersion obtained in this manner is filtered.

(70) Test No 12:

(71) This test illustrates a thickening agent according to the invention, polymerized in the presence of polyglycerol-4 sold by the company Solvay.

(72) The thickening agent is that of test no 11, polymerized according to the technique described in test no 11, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by the polyglycerol-4 of test no 6.

(73) Test No 13:

(74) This test illustrates a thickening agent according to the invention, polymerized in the presence of Chimexane NB.

(75) The thickening agent is that of test no 11, polymerized according to the technique described in test no 11, except that the polymerization surfactant has been substituted, in mass terms, by the Chimexane NB.

(76) Test No 14:

(77) This test illustrates a HASE thickening agent outside the invention, polymerized with a conventional surfactant.

(78) This thickening agent results from the synthesis, expressed as a % by weight of the monomers, of: a) 35.57% of methacrylic acid, b) 52.43% of ethyl acrylate, c) 12% of a monomer of formula (I), with: R designates the methacrylate group, q=0, p=30, R designates the hydrophobic group consisting of 12 carbon atoms and derived from ethoxylation of an oxo alcohol consisting of 12 carbon atoms.

(79) In a 1-liter reactor, 485.4 grams of bipermuted water and 6.66 grams of sodium dodecyl sulphate and 11.5 g of a surfactant sold by the company Clariant under the name Polyglykol B11/150 are weighed. The base of the tank is then heated to 72 C.2 C.

(80) During this time, a pre-emulsion is prepared by weighing the following in a beaker: 149 grams of bipermuted water, 0.33 gram of sodium dodecyl sulphate, 105.8 grams of methacrylic acid, 155.9 grams of ethyl acrylate, 35.7 grams of macromonomer of formula (I).

(81) The mass of surfactant therefore accounts in this case for 3.7% of the total mass of the manufactured polymer.

(82) 0.95 gram of ammonium persulphate is then weighed, diluted in 10 grams of bipermuted water for the first catalyst, and 0.095 gram of sodium metabisulphite diluted in 10 grams of bipermuted water for the second catalyst. When the base of the tank is at the required temperature both catalysts are added, and polymerization is effected for 2 hours at 76 C.2 C., with simultaneous addition of the pre-emulsion. The pump is rinsed with 20 grams of bipermuted water, and is fired for 1 hour at 76 C.2 C. Finally it is cooled to ambient temperature, and the dispersion obtained in this manner is filtered.

(83) Test No 15:

(84) This test illustrates a thickening agent according to the invention, polymerized in the presence of polyglycerol-4 of the company Solvay.

(85) The thickening agent is that of test no 14, polymerized according to the technique described in test no 14, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by polyglycerol-4.

(86) Test No 16:

(87) This test illustrates a thickening agent according to the invention, polymerized in the presence of Chimexane NB sold by the company Chimex.

(88) The thickening agent is that of test no 14, polymerized according to the technique described in test no 14, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by the Chimexane NB.

(89) For each of these tests, the Brookfield viscosities were determined at 25 C., at 10 and 100 revolutions per minute, at instant t=1 day (.sub.10 IJ, .sub.100 IJ), where instant t=0 is the time of manufacture of the paint.

(90) The open time of the paint expressed in minutes using the protocol set out in the preamble for a thin film is also determined, at instant t=1 day.

(91) The results are shown in table 4.

(92) TABLE-US-00004 TABLE 4 Test n 11 12 13 REFerence OI IN IN Outside Invention INvention .sub.10 1J (mPa .Math. s) 7,700 8,500 8,200 .sub.100 1J (mPa .Math. s) 2,700 2,900 3,000 open time (min.) 30 32 34 Test n 14 15 16 REFerence OI IN IN Outside Invention INvention .sub.10 1J (mPa .Math. s) 7,300 7,000 7,100 .sub.100 1J (mPa .Math. s) 3,000 2,400 2,500 open time (min.) 29 31 33

(93) If tests no 12 and 13 are compared with test no 11, and tests no 15 and 16 with test no 14, it can be ascertained that the use of polyglycerols according to the invention, during the polymerization step, enables the open time to be increased appreciably, without affecting the thickening power.

(94) The longest open times are obtained for tests no 13 and 16, which are the preferential variant of the invention.

Example 3

(95) This example illustrates the synthesis and use of different associative thickening agents, according to the invention (presence of polyglycerol during the synthesis), or outside the invention (without addition of polyglycerol during the synthesis).

(96) The use in question occurs in a water-based thick coating, the constitution of which is given in table 5, the figures indicate the mass in grams of each constituent.

(97) TABLE-US-00005 TABLE 5 Water 258.5 Ammonia 31% 2.5 Ecodis 40 (Coatex) 3.0 Mergal K6N 2.0 Nopco NDW 1.0 Durcal 130 (Omya) 380.0 Durcal 2 (Omya) 200.0 Axilat DS 910 (Hexion) 40.0 Thickening agent subject to testing 14.0 * * the value of 14 grams is equal to the mass of an emulsion containing 30% by dry weight of polymer (except for test n 18 which uses 9.0 grams of Natrosol in powder form).
Test No 17:

(98) This test illustrates a HASE thickening agent outside the invention, polymerized with a conventional surfactant.

(99) This thickening agent results from the synthesis, expressed as a % by weight of the monomers, of: a) 37.1% of methacrylic acid, b) 52.9% of ethyl acrylate, c) 10% of a monomer of formula (I), with: R designates the methacrylate group, q=0, p=35, R designates the branched hydrophobic group having 20 carbon atoms.

(100) In a 1-liter reactor, 473.55 grams of bipermuted water and 4.42 grams of sodium dodecyl sulphate and 11 g of non-ionic surfactant, which is isotridecyl alcohol condensed with 3 molecules of ethylene oxide, are weighed. The base of the tank is then heated to 72 C.2 C.

(101) During this time, a pre-emulsion is prepared by weighing the following in a beaker: 116 grams of bipermuted water, 108.14 grams of methacrylic acid, 153.75 grams of ethyl acrylate, 29 grams of macromonomer of formula (I).

(102) The mass of non-ionic surfactant therefore accounts in this case for 3.6% of the total mass of the manufactured polymer.

(103) 0.95 gram of ammonium persulphate is then weighed, diluted in 10 grams of bipermuted water for the first catalyst, and 0.095 gram of sodium metabisulphite diluted in 10 grams of bipermuted water for the second catalyst. When the base of the tank is at the required temperature, both catalysts are added, and polymerization is effected for 2 hours at 76 C.2 C., with simultaneous addition of the pre-emulsion. The pump is rinsed with 20 grams of bipermuted water, and is fired for 1 hour at 76 C.2 C. Finally it is cooled to ambient temperature, and the dispersion obtained in this manner is filtered.

(104) Test No 18:

(105) This test illustrates an HEC-type thickening agent outside the invention which is Natrosol 250 HR (Aqualon); it is used as a reference.

(106) Test No 19:

(107) This test illustrates a thickening agent according to the invention, polymerized in the presence of Chimexane NB sold by the company Chimex.

(108) The thickening agent is that of test no 17, polymerized according to the technique described in test no 17, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by the Chimexane NB.

(109) Test No 20:

(110) This test illustrates a thickening agent according to the invention, polymerized in the presence of Chimexane NC sold by the company Chimex.

(111) The thickening agent is that of test no 17, polymerized according to the technique described in test no 17, except that the non-ionic polymerization surfactant has been substituted, in mass terms, by the Chimexane NC of formula (I) with RC.sub.18H.sub.35 and n=4.

(112) Test No 21:

(113) This test illustrates a thickening agent according to the invention, polymerized in the presence of Chimexane NB sold by the company Chimex.

(114) The thickening agent is that of test no 17, polymerized according to the technique described in test no 17, except that the polymerization surfactant has been substituted (twice the mass) by the Chimexane NB.

(115) For each of these tests, the Brookfield viscosities were determined at 25 C., at 10 and 100 revolutions per minute, at instant t=1 day (.sub.10 IJ, .sub.100 IJ), where instant t=0 is the time of manufacture of the thick coating.

(116) The open time of the thick coating using the protocol set out in the preamble for a thick film is also determined, at instant t=1 day.

(117) The results are shown in table 6.

(118) TABLE-US-00006 TABLE 6 Test n 17 18 19 20 21 REFerence OI REF IN IN IN Outside Invention INvention .sub.10 1J (Pa .Math. s) 109 83 103 88 112 .sub.100 1J (Pa .Math. s) 27 30 26 23 30 open time (% of extension) 60 120 103 95 122

(119) These results demonstrate that the thickening agents according to the invention (tests n 19 to 21) enable the open time to be increased, relative to the reference, whilst retaining a satisfactory thickening power.

(120) Test no 21 even enables the open time as obtained with the reference product according to test no 18 to be improved (but with only 4.2 grams of active product, compared to 9.0 grams for the HEC-type product).