METHOD FOR MANUFACTURING PAPER AND CARDBOARD

Abstract

This invention relates to a method for manufacturing a sheet of paper or cardboard, comprising the addition of a water-soluble polymer P with a weight-average molecular weight greater than 750,000 Dalton to a fibrous suspension. This method comprises the following successive steps: preparing an aqueous solution A containing at least one water-soluble polymer P at a concentration C of between 0.1 and 0.5% by weight, said polymer P having a factor F(C) strictly greater than 4, with F.sub.(C)=Δ600/C, Δ600 being the slope to reach 90% of the viscosity developed by aqueous solution A at 600 seconds at 25° C., obtained from the viscosity curve of aqueous solution A as a function of time, at the given concentration C, at 25° C., adding aqueous solution A to the fibrous suspension, at one or more injection points, forming a sheet of paper or cardboard.

Claims

1. A method for making a paper or cardboard sheet, comprising adding a water-soluble polymer P of weight average molecular weight greater than 750,000 Daltons to a fiber suspension, characterized in that it comprises the following successive steps: preparing an aqueous solution A containing at least one water-soluble polymer P at a concentration C comprising between 0.1 and 0.5% by weight, said polymer P having a factor F.sub.(C) strictly greater than 4, with F.sub.(C)=Δ.sub.600/C, Δ.sub.600 being the slope to reach 90% of the viscosity developed by aqueous solution A at 600 seconds at 25° C., obtained from the viscosity curve of aqueous solution A as a function of time, at the given concentration C, at 25° C., polymer P being, prior to the formation of aqueous solution A, in the form of an anhydrous oily suspension containing between 20 and 60% by weight of polymer P in the form of particles with a mean diameter of strictly less than 300 μm, the viscosity of solution A over time being determined at 25° C. with the aid of a viscometer equipped with a helical geometry, adding aqueous solution A to the fibrous suspension, at one or more injection points, forming a sheet of paper or cardboard.

2. The method according to claim 1, wherein polymer P is a polymer of at least one water-soluble monoethylenically unsaturated monomer selected from: at least one nonionic monomer selected from the group consisting of acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkyl acrylamides, N,N-dialkylmethacrylamides alkoxylated esters of acrylic acid, alkoxylated esters of methacrylic acid, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkylacrylates and hydroxyalkyl methacrylates, preferably acryl amide, at least one anionic monomer selected from the group comprising monomers having a carboxylic function and their salts, including acrylic acid, methacrylic acid, itaconic acid, maleic acid monomers having a sulfonic acid function and their salts, including acrylamido tertiary butyl sulfonic acid (ATBS), allyl sulfonic acid and methallyl sulfonic acid, and their alkali or alkaline earth salts, and monomers having a phosphonic acid function and their salts, at least one cationic monomer selected from the group consisting of quaternized or salified dimethylaminoethyl acrylate (ADAME); quaternized or salified dimethylaminoethyl methacrylate (MADAME), diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), and methacrylamidopropyltrimethylammonium chloride (MAPTAC), at least one zwitterionic monomer selected from the group consisting of sulfobetaine monomers such as sulfopropyl dimethylammonium ethyl methacrylate, sulfopropyl dimethylammonium propylmethacrylamide, and sulfopropyl 2-vinylpyridinium; phosphobetaine monomers, such as phosphato ethyl trimethylammonium ethyl methacrylate, and carboxybetaine monomers.

3. The method according to claim 1, wherein the anhydrous oily suspension of polymer P comprises between 30 and 55% by weight of water-soluble polymer P.

4. The method according to claim 1, wherein the anhydrous oily suspension of polymer P contains between 0.05 and 5.0% by weight of a rheology modifier.

5. The method according to claim 1, wherein the anhydrous oily suspension of polymer P contains between 0.05 and 5.0% by weight of a rheology modifying agent selected from hydroxyethylcellulose, attapulgite, laponite, hectorite, montmorillonite, bentonite, fumed silicas and mixtures thereof.

6. The method according to claim 1, wherein the anhydrous oily suspension of polymer P contains between 0.5 and 5.0% by weight of a rheology modifier.

7. The method according to claim 1, wherein the anhydrous oily suspension of polymer P contains between 0.5 and 5.0% by weight of an emulsifying agent selected from sorbitan esters, polyethoxylated sorbitan esters, diethoxylated oleocetyl alcohol, polyesters having an average molecular weight of between 1000 and 3000 Dalton resulting from the condensation between a poly(isobutenyl) succinic acid or its anhydride and a polyethylene glycol, block copolymers with an average molecular weight of between 2500 and 3500 Dalton resulting from the condensation between hydroxystearic acid and a polyethylene glycol, ethoxylated fatty amines, derivatives of di-alkanol amides, copolymers stearyl methacrylate, and mixtures thereof.

8. The method according to claim 1, wherein the anhydrous oily suspension of polymer P of contains between 0.1 and 4.0% by weight of a rheology modifier.

9. The method according to claim 1, wherein the anhydrous oily suspension of polymer P contains between 0.1 and 4.0% by weight of a reversing agent selected from ethoxylated nonylphenols; ethoxy and propoxylated alcohols; ethoxylated tridecyl alcohols; ethoxy/propoxylated fatty alcohols; ethoxylated sorbitan esters; polyethoxylated sorbitan laurate; polyethoxylated castor oil; decaethoxylated oleodecyl alcohol; heptaethoxylated lauryl alcohol; polyethoxylated sorbitan monostearate; polyethoxylated alkyl phenol cetyl ether; polyethylene oxide alkyl aryl ether; N-ketyl-N-ethyl morpholinium ethosulfate; sodium lauryl sulfate; condensation products of fatty alcohols with ethylene oxide; condensation products of alkylphenols and ethylene oxide condensation products of fatty amines with 5 or more molar equivalents of ethylene oxide; ethoxylated tristyryl phenols; condensates of ethylene oxide with polyhydric alcohols partially esterified with fatty chains and their anhydrous forms amine oxides; alkyl polyglucosides; glucamide; phosphate esters; alkylbenzene sulfonic acids and their salts; water-soluble surfactant polymers and mixtures thereof.

10. The method according to claim 1, wherein polymer P is introduced into the fibrous suspension at a rate of 100 to 5000 gt.sup.−1 of dry matter.

11. The method according to claim 1, wherein polymer P is linear or structured.

12. The method according to claim 1, wherein polymer P of the anhydrous oily suspension is in the form of particles with an average diameter of between 0.1 μm and less than 300 μm.

13. The method according to claim 1, wherein polymer P of the anhydrous oily suspension is in the form of particles with an average diameter of between 1 μm and less than 300 μm.

14. The method according to claim 1, wherein the oil of the anhydrous oily suspension of polymer P is selected from mineral oils and/or synthetic oils.

15. The method according to claim 1, wherein the oil represents 40 to 80% by weight of the anhydrous oily suspension of polymer P.

16. The method according to claim 2, wherein the anhydrous oily suspension of polymer P comprises: between 30 and 55% by weight of water-soluble polymer P; between 0.05 and 5.0% by weight of a rheology modifier.

17. The method according to claim 16, wherein the rheology modifier is selected from hydroxyethylcellulose, attapulgite, laponite, hectorite, montmorillonite, bentonite, fumed silicas and mixtures thereof.

18. The method according to claim 17, wherein the anhydrous oily suspension of polymer P contains between 0.5 and 5.0% by weight of an emulsifying agent selected from sorbitan esters, polyethoxylated sorbitan esters, diethoxylated oleocetyl alcohol, polyesters having an average molecular weight of between 1000 and 3000 Dalton resulting from the condensation between a poly(isobutenyl) succinic acid or its anhydride and a polyethylene glycol, block copolymers with an average molecular weight of between 2500 and 3500 Dalton resulting from the condensation between hydroxystearic acid and a polyethylene glycol, ethoxylated fatty amines, derivatives of di-alkanol amides, copolymers stearyl methacrylate, and mixtures thereof.

19. The method according to claim 18, wherein the anhydrous oily suspension of polymer P contains between 0.1 and 4.0% by weight of a reversing agent selected from ethoxylated nonylphenols; ethoxy and propoxylated alcohols; ethoxylated tridecyl alcohols; ethoxy/propoxylated fatty alcohols; ethoxylated sorbitan esters; polyethoxylated sorbitan laurate; polyethoxylated castor oil; decaethoxylated oleodecyl alcohol; heptaethoxylated lauryl alcohol; polyethoxylated sorbitan monostearate; polyethoxylated alkyl phenol cetyl ether; polyethylene oxide alkyl aryl ether; N-ketyl-N-ethyl morpholinium ethosulfate; sodium lauryl sulfate; condensation products of fatty alcohols with ethylene oxide; condensation products of alkylphenols and ethylene oxide condensation products of fatty amines with 5 or more molar equivalents of ethylene oxide; ethoxylated tristyryl phenols; condensates of ethylene oxide with polyhydric alcohols partially esterified with fatty chains and their anhydrous forms amine oxides; alkyl polyglucosides; glucamide; phosphate esters; alkylbenzene sulfonic acids and their salts; water-soluble surfactant polymers and mixtures thereof.

20. The method according to claim 19, wherein polymer P of the anhydrous oily suspension is in the form of particles with an average diameter of between 0.1 μm and less than 300 μm.

Description

DESCRIPTION OF FIGURES

[0064] FIG. 1 shows curves of viscosity as a function of time of polymers P of different factors F.sub.(C).

[0065] FIG. 2 represents a viscosity versus time curve of a polymer P for which the F.sub.(C) factor is calculated.

EXAMPLES OF EMBODIMENTS OF THE INVENTION

[0066] Procedures Used in the Examples:

[0067] a) Types of Pulp Used

[0068] Virgin Fiber Pulp:

[0069] Wet pulp is obtained by disintegrating dry pulp to obtain a final aqueous concentration of 1% by weight. It is a neutral pH pulp composed, by weight, of 90% bleached virgin long fibers, 10% bleached virgin short fibers, and 30% additional GCC (ground calcium carbonate) (Hydrocal® 55 from Omya) in relation to the weight of the fibers.

[0070] Recycled Fiber Pulp:

[0071] Wet pulp is obtained by disintegrating dry pulp to obtain a final aqueous concentration of 1% by weight. It is a pH-neutral pulp made from 100% recycled cardboard fibers.

[0072] b) Assessment of Total Retention and Charge Retention

[0073] The different results are obtained through the use of a “Britt Jar” type container, with a stirring speed of 1000 revolutions per minute.

[0074] The sequence for adding the different retention agents is as follows: [0075] T=0 s: Stirring 500 mL of pulp at 0.5% by weight [0076] T=10 s: Optional addition of agent X [0077] T=20 s: Optional addition of retention agent [0078] T=30 s: Removal of the first 20 mL corresponding to the dead volume under the fabric, then recovery of 100 mL of white water

[0079] The first pass retention (% FPR for “First Pass Retention”), corresponding to the total retention is calculated according to the following formula:

% FPR=(C.sub.HB−C.sub.WW)/C.sub.HB*100

[0080] The first pass retention of ash as a percentage (% FPAR for “First Pass Ash Retention”) is calculated according to the following formula:

% FPAR=(A.sub.HB−A.sub.WW)/A.sub.HB*100

[0081] with: [0082] C.sub.HB: Consistency of the head box [0083] C.sub.WW: Consistency of the white water [0084] A.sub.HB: Consistency of the ashes of the head box [0085] A.sub.WW: Consistency of the white-water ashes

[0086] c) Evaluation of Gravity Drainage Performance Using the “Canadian Standard Freeness” (CSF)

[0087] In a beaker, the pulp is treated, subjected to a stirring speed of 1000 revolutions per minute.

[0088] The sequence for adding the different retention agents is as follows: [0089] T=0 s: Stirring of 500 mL of pulp at 0.6% by weight [0090] T=10 s: Optional addition of agent X [0091] T=20 s: Added retention agent [0092] T=30 s: Stop stirring and add the quantity of water necessary to obtain 1 liter.

[0093] This liter of pulp is transferred to the “Canadian Standard Freeness Tester” and the TAPPI T227om-99 procedure is applied.

[0094] The volume, expressed in mL, collected by the side pipe gives a measure of gravity dripping. The higher this value, the better the gravity drainage.

[0095] This performance can also be expressed by calculating the percentage improvement over blank (% CSF).

[0096] d) Evaluation of Drainage Performance (DDA)

[0097] The DDA (“Dynamic Drainage Analyzer”) automatically determines the time (in seconds) required to drain a fibrous suspension under vacuum. The polymers are added to the wet pulp (0.6 liters of pulp at 1.0% by weight) in the DDA cylinder with stirring at 1000 rpm: [0098] T=0 s: stirring the pulp [0099] T=10 s: optional addition of agent X [0100] T=20 s: addition of retention agent [0101] T=30 s: stopping the stirring and draining under vacuum at 200 mbar (1 bar=10.sup.5 Pa) for 70 s.

[0102] The pressure under the fabric is recorded as a function of time. When all the water is evacuated from the fibrous mat, the air passes through it causing a break in the slope to appear on the curve representing the pressure under the fabric as a function of time. The time, expressed in seconds, recorded at this break in slope corresponds to the drip time. The shorter the time, the better the vacuum drainage.

[0103] e) Performance in DSR Application (Dry Strength), Grammage at 90 gm.sup.−2

[0104] The necessary quantity of pulp is removed so as to obtain in the end a sheet having a basis weight of 90 gm.sup.−2.

[0105] The wet pulp is introduced into the vat of the dynamic molder and is kept under agitation. The different components of the system are injected into this pulp according to the predefined sequence.

[0106] A contact time of 30 to 45 seconds is generally respected between each addition of polymer.

[0107] Paper formettes are produced with an automatic dynamic former: a blotter and the forming fabric are placed in the bowl of the dynamic former before starting the rotation of the bowl at 1000 rpm.sup.−1 and building the water wall. The treated pulp is spread over the water wall to form the fibrous mat on the forming fabric.

[0108] Once the water is drained, the fibrous mat is recovered, pressed under a press delivering 4 bar, then dried at 117° C. The sheet obtained is conditioned overnight in a room with controlled humidity and temperature (50% relative humidity and 23° C.). The dry strength properties of all the sheets obtained by this procedure are then measured.

[0109] The burst is measured with a Messmer Buchel M 405 burst tester according to the TAPPI T403 om-02 standard. The result is expressed in kPa. The bursting index is determined, expressed in kPa.Math.m.sup.2/g, by dividing this value by the grammage of the sheet tested.

[0110] Dry breaking length is measured in the machine direction with a Testometric AX tensile device according to TAPPI T494 om-01. The result is expressed in km.

[0111] f) Viscosity Measurement Over Time with HAAKE IQ Air

[0112] The Haake Viscometer IQ Air is a viscometer operating on the basis of an air bearing motor driving a geometry allowing controlled shear or controlled shear stress tests. With a propeller-type module, this device makes it possible to measure the viscosity deployed by the polymer during its dissolution over time. For the measurement, the polymer solution is prepared directly in the sample holder. At the end of the measurement, the data is saved and formatted via a viscosity graph=f (time).

[0113] Products Tested in the Examples:

[0114] In the following list, type A products are anionic and type C products are cationic. Type X products are high filler-dense products which can each be used, for example, as a coagulant. Product X.sub.1 is inorganic in nature, while product X.sub.2 is organic.

[0115] Polymer A.sub.1: Water-soluble polymer composed of 30 mol % of sodium acrylate and 70 mol % of acrylamide in the form of an inverse emulsion, this emulsion comprises 29% of A.sub.1, 30% of water, and 30% of oil by weight. A.sub.1 has an average molecular weight of 20 million Dalton (Brookfield viscosity of 8.16 cps (applicable for all polymers below: UL modulus, 0.1%, 1M NaCl, 60 rpm.sup.−1, 23° C.)).

[0116] Polymer A.sub.2: Water-soluble polymer composed of 30 mol % sodium acrylate and 70 mol % acrylamide in the form of an oily suspension (distilled inverse emulsion). This suspension contains 50% by weight of A.sub.2, 40% by weight of oil, 5% water. A.sub.2 has an average molecular weight of 18 million Daltons (Brookfield viscosity of 7.76 cps).

[0117] Polymer A.sub.3: Water-soluble polymer composed of 30 mol % sodium acrylate and 70 mol % acrylamide in powder form. A.sub.3 has an average molecular weight of 18 million Daltons (Brookfield viscosity 7.71 cps).

[0118] Polymer A.sub.4: Water-soluble polymer composed of 30 mol % sodium acrylate and 70 mol % acrylamide in powder form. A.sub.4 has an average molecular weight of 5 million Daltons (Brookfield viscosity 2.21 cps).

[0119] Polymer A.sub.5 (invention): Water-soluble polymer composed of 30 mol % of sodium acrylate and 70 mol % of acrylamide in the form of an anhydrous oily suspension. The average size of the polymer particles is between 1 and less than 300 μm. The oily suspension contains 55.5% by weight of polymer A.sub.5, 37.5% by weight of oil, 4.5% by weight of bentonite, 2% by weight of sorbitan monooleate, and 0.5% by weight of C13 oxo ethoxylatedalcohol, A.sub.6 has an average molecular weight of 18 million Daltons (Brookfield viscosity 7.71 cps).

[0120] Polymer A.sub.6 (invention): Water-soluble polymer composed of 30 mol % of sodium acrylate and 70 mol % of acrylamide in the form of an anhydrous oily suspension. The average size of the polymer particles is between 1 and less than 300 μm. The oily suspension contains 52.5% by weight of polymer A.sub.6, 40.5% by weight of oil, 4.5% by weight of bentonite, 2% by weight of sorbitan monooleate, and 0.5% by weight of C13 oxo ethoxylatedalcohol, A.sub.6 has an average molecular weight of 5 million Daltons (Brookfield viscosity 2.21 cps).

[0121] Polymer C.sub.1: Water-soluble polymer composed of 15 mol % of chloromethylated dimethylaminoethyl acrylate (ADAME) and 85 mol % of acrylamide in the form of an inverse emulsion, this emulsion containing 35% of C.sub.1, 30% of water, and 30% of oil by weight. C.sub.1 has an average molecular weight of 8 million Daltons (Brookfield viscosity of 4.86 cps).

[0122] Polymer C.sub.2: Water-soluble polymer composed of 15 mol % of chloromethylated dimethylaminoethyl acrylate (ADAME) and 85 mol % of acrylamide in the form of an oily suspension (distilled inverse emulsion). This suspension contains 50% by weight of C.sub.2, 40% by weight of oil, 5% water. C.sub.2 has an average molecular weight of 8 million Daltons (Brookfield viscosity of 4.96 cps).

[0123] Polymer C.sub.3: Water-soluble polymer composed of 15 mol % of chloromethylated dimethylaminoethyl acrylate (ADAME) and 85 mol % of acrylamide in powder form. C.sub.3 has an average molecular weight of 9 million Dalton (Brookfield viscosity 4.96 cps).

[0124] Polymer C.sub.4 (invention): Water-soluble polymer composed of 15 mol % of chloromethylated dimethylaminoethyl acrylate (ADAME) and 85 mol % of acrylamide in the form of an oily suspension (distilled inverse emulsion). The average size of the polymer particles is between 1 and less than 300 μm. The oily suspension contains 52.5% by weight of polymer C.sub.4, 40.5% by weight of oil, 4.5% by weight of bentonite, 2% by weight of sorbitan monooleate, and 0.5% by weight of ethoxylated C.sub.13 oxo alcohol. C.sub.4 has an average molecular weight of 8 million Daltons (Brookfield viscosity of 4.96 cps).

[0125] Product X.sub.1: Polyaluminium chloride containing 18% by weight of alumina (Al.sub.2O.sub.3).

[0126] Product X.sub.2: Cationic product with a cationic charge density of 5.5 meq/g, from the Hofmann reaction on a polyacrylamide.

[0127] Factors F.sub.(c) of polymers A.sub.n and C.sub.n at different concentrations C (in % in weight)

TABLE-US-00001 TABLE 1 Polymers A.sub.n Polymer A.sub.1 A.sub.2 A.sub.3 A.sub.4 Concentration 0.5 0.3 0.1 0.5 0.3 0.1 0.5 0.3 0.1 0.5 0.3 0.1 (% by weight) Viscosity 427 205 96 343 206 83 389 274 119 142 78 51 600 s (cps) Viscosity 384 185 86 309 185 75 350 247 107 128 70 46 90% (cps) Starting 17 17 17 17 17 17 17 17 17 17 17 17 viscosity (cps) Time 90% 340 374 441 266 340 360 315 400 486 330 414 330 (seconds) Factor F.sub.(C) 2.16 1.49 1.57 2.19 1.65 1.60 2.11 1.91 1.85 0.67 0.43 0.88 Polymer A.sub.5 A.sub.6 Concentration 0.5 0.3 0.1 0.5 0.3 0.1 (% by weight) Viscosity 600 380 305 196 145 92 70 secondes (cps) Viscosity 342 275 176 131 82 63 90% (cps) Starting 17 17 17 17 17 17 viscosity (cps) Time 90% 54 58 93 50 52 90 (secondes) Factor F.sub.(C) 12.04 14.80 17.14 4.54 4.22 5.11

TABLE-US-00002 TABLE 2 C.sub.n polymers Polymer C.sub.1 C.sub.2 C.sub.3 C.sub.4 Concentration 0.5 0.3 0.1 0.5 0.3 0.1 0.5 0.3 0.1 0.5 0.3 0.1 (% by weight) Viscosity 233 132 79 226 155 85 198 135 84 251 179 119 600 s (cps) Viscosity 210 119 71 203 140 77 178 121 76 226 161 107 90% (cps) Starting 17 17 17 17 17 17 17 17 17 17 17 17 viscosity (cps) Time 90% 107 102 144 176 114 168 410 490 468 70 78 90 (secondes) Factor F.sub.(C) 3.60 3.33 3.76 2.12 3.58 3.54 0.79 0.71 1.25 5.97 6.16 10.01

[0128] FIG. 1 represents the viscosity curves as a function of time for the polymers A.sub.1, A.sub.2 and A.sub.3 and A.sub.5 for a polymer concentration of 0.3% by weight in water.

[0129] FIG. 2 represents the curve of viscosity as a function of time for polymer A.sub.5 and details the method for calculating the factor F.sub.(c).

[0130] Only polymers A.sub.5, A.sub.6 and C.sub.4 have F.sub.(c) factors greater than 4. They are the only ones to have reached a maximum viscosity after 600 s.

[0131] Application Tests

[0132] For all the following tests, the polymer solutions are prepared at the desired concentration (0.1%, 0.3%, or 0.5% by weight). After 2 minutes of preparation, the polymer solutions are filtered through a 300 μm filter. If the filter is covered with polymer particles, the application test is not carried out (NA: Not Applicable). The filtrates are used directly for the application tests.

[0133] CSF Performance, Retention and Filler Retention

TABLE-US-00003 TABLE 3 CSF, retention and filler retention % CSF % CSF % CSF % FPR % FPAR % FPR % FPAR % FPR % FPAR 2 min 2 min 2 min 2 min 2 min 2 min 2 min 2 min 2 min 0.5% 0.3% 0.1% 0.5% 0.5% 0.3% 0.3% 0.1% 0.1% blank — — — 65.4  2.9 65.4 2.9 65.4  2.9 C.sub.2 (0.25 kg/t) 40.4 34.9 30.8 79.7 35.3 78.2 32 77.1 29.4 C.sub.1 (0.25 kg/t) 38.8 34.3 32.1 79.2 33.5 78   30.9 77.4 29.6 C.sub.4 (0.25 kg/t) 41.7 41.3 40.4 80   35.3 79.9 35.2 79.6 34.5 C.sub.3 (0.25 kg/t) NA NA NA NA NA NA NA NA NA X.sub.1 (0.25 kg/t) 31.7 26.0 21.8 74.8 25.8 73.7 23 72.8 20.9 A.sub.2 (0.2 kg/t) X.sub.1 (0.25 kg/t) 33.3 32.4 28.8 75.1 26.5 74.9 26 74.2 24.3 A.sub.1 (0.2 kg/t) X.sub.1 (0.25 kg/t) 48.7 45.2 40.1 78.3 34.7 77.6 33 76.6 30.4 A.sub.5 (0.2 kg/t) X.sub.1 (0.25 kg/t) NA NA NA NA NA NA NA NA NA A.sub.3 (0.2 kg/t)

[0134] DDA Performance and Mechanical Resistance

TABLE-US-00004 TABLE 4 DDA and mechanical strengths % DBL % Burst % DBL % Burst % DBL % Burst % DDA % DDA % DDA SM index SM index SM index 2 min 2 min 2 min 2 min 2 min 2 min 2 min 2 min 2 min 0.5% 0.3% 0.1% 0.5% 0.5% 0.3% 0.3% 0.1% 0.1% blank — — — — — — — — — X.sub.2 (1 kg/t) 35.9 35.9 35.6 10.1  8.6 10.6  8.8 10.3  8.6 X.sub.2 (1 kg/t) 62.0 60.8 58.5 19.6 19.8 18.7 17.8 15.5 15.7 A.sub.6 (1 kg/t) X.sub.2 (1 kg/t) NA NA NA NA NA NA NA NA NA A.sub.4 (1 kg/t)

[0135] For all the application tests, the best performances are obtained with polymers A.sub.5, A.sub.6 and C.sub.4 which have factors F.sub.(c) higher than 4. They show the importance of the form of the polymer (anhydrous oily suspension) beforehand when it is put into solution and of the factor F.sub.(c) in order to improve the properties of drainage, retention and the mechanical properties of the sheet of paper or cardboard.