Method for producing an emulsion of alkenyl succinic anhydride (ASA) in an aqueous solution of a cationic amylaceous substance, resulting emulsion, and use thereof

Abstract

A method for producing an emulsion of ASA in an aqueous solution of a cationic amylaceous substance, without having to use a loop for recirculating the product at the emulsification unit. The produced emulsion is characterized by both a fine and monodisperse particle size, and no overheating is involved that could lead to negative phenomena of hydrolyzing the ASA. The corresponding production device is also described.

Claims

1. A process for manufacturing an emulsion of alkenylsuccinic anhydride (ASA) in an aqueous solution of cationic starchy material, comprising the steps of: a) preparing an aqueous solution of cationic starchy material, b) mixing the ASA and the aqueous solution of cationic starchy material obtained from step a), so as to obtain a cationic starchy material/ASA dry weight ratio of less than 1, c) preparing in a single pass in an emulsification unit an emulsion from the mixture obtained from step b), wherein: the process does not involve recirculation of the emulsion obtained from step c) in the emulsification unit, the aqueous solution of cationic starchy material obtained from step a) has a solids content between 5.5% and 11.5% of its total weight, and the aqueous solution of cationic starchy material has a content of fixed nitrogen of less than 3.5% by dry weight of nitrogen relative to the total dry weight of cationic starch material; wherein said process is performed in a device consisting of: a unit (a) for storing the aqueous solution of cationic starchy material to perform step a), a unit (b) for mixing ASA and the aqueous solution of cationic starchy material, connected to the unit (a) to perform step b), a emulsification unit (c) comprising mechanical means of shearing or milling for emulsifying the mixture of ASA and of the aqueous solution of cationic starchy material, the emulsification unit (c) being connected to the unit (b), to perform step c), said device not containing a recirculation loop in the emulsification unit (c).

2. The process as claimed in claim 1, wherein the ASA is a product of synthetic origin, which is a modified oil that results from C16-C18 fractions.

3. The process as claimed in claim 1, wherein the cationic starchy material is modified by one of a hydrolysis, chemical and physical, mechanical, thermomechanical or thermal transformation operation.

4. The process as claimed in claim 2, wherein the cationic starchy material is modified by one of a hydrolysis, chemical and physical, mechanical, thermomechanical or thermal transformation operations.

Description

EXAMPLES

(1) In all the examples, the granulometry of the emulsions is analyzed using a laser particle size analyzer sold by the company Malvern under the name Mastersizer 2000, with the following parameters: 800 ml of demineralized water stirring at 1900 rpm background measurement: 10 s 3 consecutive measurements per sample (interval between the measurements: 0 s) duration of each measurement: 10 s laser obscuration: between 8% and 13% refractive index: 1.5 dispersant (water) refractive index: 1.33 absorption: 0.01 particle shape model=spherical

Example 1

(2) The aim of this example is to illustrate the manufacture of an emulsion of ASA in an aqueous solution of cationic starchy material in a device according to the invention not containing a recirculation loop in the emulsification unit, and with a device according to the prior art. It also has the object of illustrating the influence of the solids content of the initial aqueous solution of cationic starchy material on the granulometry of the emulsion prepared.

(3) An aqueous solution of cationic starchy material sold by the company Roquette under the name Vector SCA 2015 is used. The ASA which is the product Chemsize A180 sold by the company Chemec is also used. This product contains 0.5% by weight of sodium dioctyl sulfosuccinate as surfactant (also known as DOSS).

(4) Feeding with water is performed using an existing distribution network. The transfers and metering of the ASA and of the aqueous solution of cationic starchy material to this emulsification platform are performed from their respective mobile container or storage tank, by means of pipes and volumetric pumps, the rotation speeds of which are regulated at the desired nominal flow rates and at the target cationic starchy material (dry)/ASA ratio.

(5) The aqueous solution of cationic starchy material is diluted online. The flow rate of dilution water is regulated by the flow rate of the commercial aqueous solution of cationic starchy material, as a function of the desired solids content. A static mixer homogenizes this dilute aqueous solution. The ASA is then introduced online, into the homogeneous dilute aqueous solution of cationic starchy material.

(6) This aqueous solution of cationic starchy material/ASA mixture is then conveyed via a pipe to the emulsification unit. This continuous single-pass emulsification system has a series of 3 consecutive rotors/stators, each rotor and each stator of which is composed of 3 rows of concentric toothed crowns. This process operates at variable speed; the rotation speed depends on the passing hydraulic flow rate, on the nature of the constituents and the proportions thereof, on the pressure in the emulsification chamber, and also on the desired fineness of the emulsion. The emulsification unit outlet is equipped with a temperature sensor, a pressure sensor, a valve for maintaining pressure of 3 bar in the process, and a flowmeter.

(7) In this example, the dry content of the aqueous solution of cationic starchy material was varied from 3% to 20%, the cationic starchy material/ASA dry ratio from 0.3 to 0.5, the flow rate at the emulsification unit outlet from 80 to 140 kg/h, the peripheral speed of the emulsification unit rotor being set at 40 m/s.

(8) In all the tests, the temperature T C. of the emulsion leaving the emulsification unit is determined, and a granulometric analysis is performed according to the protocol already presented, so as to determine the mean diameter and the parameter %<2 m. In all the tests, except test 6, the emulsion at the emulsification unit outlet is recovered, whereas in test 6, the emulsion is recirculated at least once more in said unit.

(9) The results are collated in Table 1, with the following abbreviations:

(10) Flow rate (kg/h): flow rate at the emulsification unit outlet

(11) SM/ASA: cationic Starchy Material/ASA dry weight ratio

(12) SC SM (%): solids content of cationic starchy material in the initial solution

(13) T ( C.): temperature of the final emulsion leaving the emulsification unit

(14) %<2 m: volume percentages of particles less than 2 m in diameter

(15) d mean (m): mean particle diameter

(16) TABLE-US-00001 TABLE 1 Flow rate SC SM T % < 2 d mean Tests (kg/h) SM/ASA (%) ( C.) m (m) 1 125 0.5 5 40 64.9 2.03 2 80 0.3 5 44 77.0 1.80 3 125 0.3 3 39 39.1 2.58 4 110 0.3 3 38 34.7 2.80 5 125 0.3 8 46 80.2 1.43 6* 125 0.3 8 63 75.4 1.55 7 100 0.3 20 83 47.0 2.36 8 140 0.3 13 56 58.2 2.04 9 125 0.3 7 43 82.5 1.46 10 125 0.5 7 42 84.9 1.48 11 125 0.5 6 41 81.7 1.49 11** 125 0.5 6 41 82.0 1.50 *2 circulations in the emulsification unit, by ordered and consecutive passings **granulometric analysis performed after 90 minutes of storage at room temperature

(17) Tests 1 to 4 demonstrate that, at two given SM/ASA ratios and for an excessively low solids content of cationic starchy material (3% and 5%), an excessively high mean diameter is obtained (notably very much higher than 2 m for tests 3 and 4) and/or an excessively low value of %<2 m is obtained. This therefore does not give an optimal amount of particles whose diameter is between 1 m and 1.5 m, which means that particles of larger size are generated, which may give rise to fouling problems.

(18) Similarly, tests 7 and 8 performed with a large solids content of starchy material do not give the desired granulometry. In addition, they lead to high emulsion temperatures which run the risk of facilitating detrimental hydrolysis of the ASA.

(19) As regards test 6*, it demonstrates that the 2 ordered and consecutive passings of the emulsion through the emulsification unit cause a very large increase in temperature.

(20) In summary, only tests 5, 9, 10 and 11 lead to a final product characterized by a mean particle diameter of between 1 m and 1.5 m, with a %<2 m index of greater than 80%, and with a low increase in temperature. This thus gives an emulsion that is potentially very efficient as a sizing agent by virtue of its granulometry, and which is advantageously free of any detrimental hydrolysis phenomenon. Test 11** demonstrates that, over a long storage period, the manufactured emulsion conserves its granulometric characteristics.

Example 2

(21) The aim of this example is to illustrate the manufacture of an emulsion from ASA and from an aqueous solution of cationic starchy material in a device according to the invention without a recirculation loop. It notably illustrates the influence of the solids content of the initial aqueous solution of cationic starchy material on the granulometry of the emulsion prepared, and on the hydrophobic nature of a paper manufactured with this emulsion.

(22) This example is performed under the same conditions as the preceding example, the only difference being that the continuous single-pass emulsification system has only one rotor/stator, each of the two parts of which is composed of 3 rows of concentric toothed crowns.

(23) Tests 12 to 16 use, in a device according to the invention, an aqueous solution of cationic starchy material sold by the company Roquette under the name Vector SCA 2015 and of ASA which is the product Chemsize A180 sold by the company Chemec. The cationic starchy material (SM)/ASA dry weight ratio here is equal to 0.3. The peripheral speed is set at 40 m/s and the flow rate at the emulsification unit outlet is equal to 140 kg/h. Tests 12, 13, 14, 15 and 16 use, respectively, a solids content of 2%, 7%, 9%, 12% and 16% cationic starchy material in the initial aqueous solution.

(24) In all the tests, the temperature T C. of the emulsion at the emulsification unit outlet is determined, and a granulometric analysis is performed according to the protocol already presented, so as to determine the mean diameter d and also the parameter %<2 m. All the results are given in Table 2, the abbreviations remaining unchanged.

(25) TABLE-US-00002 TABLE 2 SC SM T % < 2 d mean Tests (%) ( C.) m (m) 12 2 34 39.1 2.70 13 7 41 81.3 1.48 14 9 43 80.8 1.42 15 12 47 69.6 1.79 16 16 70 52.5 2.61

(26) It is clearly seen that the product obtained according to test 16 underwent a very large increase in its temperature: it is thus subject to ASA hydrolysis that is prohibitive to its use as a sizing agent, as will be demonstrated later.

(27) For these emulsions, laboratory sheets of paper known as handsheets are prepared using a FRET machine (handsheet retention tester) sold by the company Techpap. These handsheets have characteristics close to that of client industrial paper, notably as regards flocculation and retentions.

(28) The process for manufacturing the handsheet uses a paper pulp which is a pulp of virgin fibers (50% coniferous, 50% broad-leaved) with a refining level of 35 Schopper (SR). 35% (by dry weight relative to the total weight of the pulp) of natural calcium carbonate sold by the company Omya under the name Omyalite 50 is added. The charged fibrous suspension has a concentration of 2.5 g/l. 0.3% (dry equivalent/paper) of a size Hicat 5163AM (Roquette) is then added. Finally, 0.35% (relative to the paper) of the ASA emulsion is added. A handsheet with a basis weight of 70 g/m.sup.2 is thus prepared.

(29) After manufacture of the handsheet, it is placed between two sheets of blotting paper and the assembly is passed twice through a Techpap brand roll press. The handsheet is then separated from the blotting papers and is placed in a Techpap brand dryer for 5 minutes at 100 C. Maturation of the handsheets is then performed, by placing them for 30 minutes in an oven at 110 C., to allow the sizing agent to give the paper its hydrophobic nature. The handsheets are then placed for a minimum of 24 hours in an air-conditioned room at 23 C. (1 C.) and 50% relative humidity (2%) (standards ISO 187: 1990 and Tappi T402 sp-08).

(30) A Cobb 60 measurement (standards ISO 535: 1991 and Tappi T441 om-04) is then performed, which relates to the hydrophobicity of the paper: the smaller the amount of water absorbed, the more hydrophobic the paper (Table 3). For the handsheets made from the emulsions according to tests 12 to 16, a mean Cobb value equal to 47, 28, 25, 45 and 51 g/m.sup.2 is found, respectively. It is thus demonstrated that it is indeed the handsheets made according to the invention (tests 13 and 14) which have the highest hydrophobicity.

Example 3

(31) The aim of this example is to illustrate the manufacture of an emulsion from ASA and from an aqueous solution of cationic starchy material in a device according to the invention not containing a recirculation loop. It notably demonstrates that the granulometric characteristics of the manufactured emulsions are constant over time.

(32) The tests use the aqueous solution of cationic starchy material Vector SCA 2015 and the product Chemsize A180. They are performed using a device identical to that described in the preceding example.

(33) This example is performed under the same conditions as those of Example 2. Here, the solids content was set at 8%, the cationic starchy material/ASA dry ratio at 0.32 and the flow rate at the emulsification unit outlet at 220 L/h and the peripheral speed at 40 m/s.

(34) 3 granulometric analyses are formed here on 3 samples collected at 45 minutes, 3 hours and 5 hours. Besides the mean diameter d and the parameter %<2 m, the volume percentage of particles whose diameter is within a certain range was also determined: the corresponding results are given in Tables 3, 3a and 3b.

(35) TABLE-US-00003 TABLE 3 (after 45 minutes of running) % (volume) between (m) 100.00 0.48 3.80 99.73 0.55 3.31 82.15 0.83 2.19 75.32 0.83 1.90 48.50 1.10 1.66 25.37 1.26 1.44 81.5 % < 2 m Mean diameter 1.43

(36) TABLE-US-00004 TABLE 3a (after 3 hours of running) % (volume) between m) 100.00 0.48 3.80 99.86 0.55 3.31 97.89 0.63 2.88 92.18 0.72 2.51 75.72 0.83 1.90 48.62 1.10 1.66 25.43 1.26 1.44 12.82 1.30 1.41 87.8 % < 2 m Mean diameter 1.41

(37) TABLE-US-00005 TABLE 3b (after 5 hours of running) % (volume) between (m) 100.00 0.55 3.31 98.77 0.63 2.88 93.39 0.72 2.51 76.74 0.83 1.90 49.46 1.10 1.66 25.89 1.26 1.44 88.3 % < 2 m Mean diameter 1.42

(38) Not only is the consistency of the manufactured emulsions in terms of granulometric characteristics demonstrated, but also it is clearly demonstrated afterward that the particle size distributions are monodisperse.