GB2063282A

GB2063282A - Process for the cationization of starch, cationic starches so prepared and their use

Info

Publication number: GB2063282A
Application number: GB7930306A
Authority: GB
Original assignee: Roquette Freres SA
Current assignee: Roquette Freres SA
Priority date: 1978-08-31
Filing date: 1979-08-31
Publication date: 1981-06-03
Also published as: IT1122927B; NL189135C; GB2063282B; IT7925410A0; FR2434821A1; FR2434821B1; BE878532A; NL189135B; NL7906515A; DE2935338C2; DE2935338A1

Abstract

A process for the cationization of starch consists in reacting in the dry state granular starch with a cationic reactant, the reaction being operated at a temperature of 20 to 90 DEG C, in the presence of an alkaline agent. The starches which are thus obtained are not cross-linked and have a high viscosity and have many applications, e.g. as thickeners and water retention agents. Particularly useful cationic reactants are of formula <IMAGE> in which R1, R2 and R3 are each methyl or ethyl with one of R1, R2 and R3 optionally being a hydrogen atom and X(-) representing Cl(-), Br(-) or I(-) or <IMAGE> where R1, R2, R3 and X(-) have the same meanings as above and X represents Cl, Br or I.

Description

SPECIFICATION Process for the cationization of starch, cationic starches so prepared and their use The invention relates to a process for the cationization of starch.

It also relates to the cationic starches obtained by the application of the abovesaid process.

Lastly, it relates to the applications of these cationic starches.

The cationization of starch which consists of introducing a cationic group on the starch is effected by condensing 3 cationic reactant, which bear a cationizable site on to a hydroxyl group of the starch molecule.

The process according to the invention consists of reacting in the dry state granular starch with a cationic reactant and is characterized by the fact that the reaction is applied at a temperature of 20 to 900 C, preferably from 60 to 800 C, in the precence of an alkaline agent, notably caustic soda.

According to a first advantageous embodiment, the abovesaid process is applied by resorting to a reactant of epoxy form corresponding to the formula:

in which the substituents R, R2 and R3 are preferably, identical and selected from among radicals methyl and ethyl, of which one can be a hydrogen atom, Xe representing Cl-, Br or 1-.

In a second advantageous embodiment, the abovesaid process is applied by resorting to a reactant selected from among those of the above-mentioned formula (I) and those corresponding to the formula:

in which the substituents R,, R2 and R3 have the significances indicated with regard to formula (I), X representing an atom of Cl, Br or I, the amount of reactant utilized being such that the nitrogen ratio of the cationic starch obtained is higher than 0.95 and at the most equal to 2.8.

In a third advantageous embodiment, the amount of alkaline agent applied is from 0.2 to 2%, preferably from 0.5 to 1% with respect to the treated starch when the cationic agent is that of formula (I), this amount being increased, when the cationic agent is that of formula (it), in a proportion corresponding to the neutralization of the agent of formula (II).

The cationic starches obtained by using the above-said process are not cross-linked and have a viscosity higher than 1000, preferably higher than 1500 and, more preferably again, than 2000 Brabender units (B.U.), measured at a concentration of 5%.

The applications according to the invention of the cationic starches obtained in accordance with the invention are numerous.

These cationic starches have in fact a very interesting group of properties. They can fulfill the role of a protective colloid; their thickening character may be sought by relying on their remarkable ability, notably for aqueous soiutions and this, especially for highiy substituted products. It is also possible to exploit their binding properties. They can serve as adhesive substances. The starches with a high ratio of nitrogen have a remarkable water retention capacity. The weakly to very strongly cationic character of these starches often offers a determining interest.

It is possible to envisage the use of the products of the invention in the paper industry, as a wetend product or surface-phasing product or entering in or forming part of the coating formulae. They can be used in the adhesive industry where, in addition to their adhesive character, all of their other properties are applied. Numerous other industries may resort to these products and their properties. It is possible to cite among the latter, the paint, varnish and ink industry, the plaster industry, glues for wallpapers, the ceramic industry, latices, detergents, printing pastes for textiles, vitrified enamels, liquid detergents soaps and cosmetic products, pencil leads, petroleum drilling muds, agriculture (water retention agent), the book binding industry, electrical cables, the warp sizing of textile fibers and glass fibers, and the gumming industry.

In particular, the invention relates to the appiication of the abovesaid starches: -as liquid retention agents, notably in the manufacture of babies diapers and plasters, -as starch thickeners, notably in the paint, ink and varnish industry and in textile printing, -as fine fiber and filler retention agents in the paper industry, -and as draining agents, notably in paper making.

The proportion of cationic starch in accordance with the invention which has to be applied in the principal applications varies according to the industry concerned; there will be found in this connection the numerical indications in the examples.

The invention will be well understood by means of the complement of description which follows and of the appended examples, said complement of the description and examples corresponding to advantageous embodiments.

Consequentiy in order to prepare, in accordance with the invention, cationic starches, procedure is as follows or in equivalent manner.

There are reacted in the dry state at a temperature of 20 to 900C, preferably from 60 to 800C, for example in a conventional mixing apparatus for powdered materials equipped with suitable heating means, for example with a double jacket functioning for example by means of water or steam, granular starch and the cationic reactant applied according to the invention, the reaction being conducted in the presence of an alkaline agent The starch used may be a cereal starch (corn, waxy maize, wheat and the like) or a native or previously modified tuber starch (potato starch, manioc and the like).

The alkaline agent is preferably constituted by caustic sods, avantageously applied in the form of powder, or possibly lime.

The cationic reactant applied preferably corresponds to that of the formula:

in which the substituents R1, R2 and R3 are, preferably, identical and selected from among methyl and ethyl, of which one can be a hydrogen atom, Xe representing Cl-, Bf or l.

It may also be that of the formula:

in which the substituents Rt, R2 and R3 have the significances indicated with respect to formula (I), X representing an atom of CI, Br or I, the amount of reactant applied being such that the nitrogen ratio of the cationic starch obtained is greater than 0.95 and at the most equal to 2.8.

The amount of cationic reactant applied can vary from 0.5 to 60% by weight with respect to the starch.

When, in formulae (i) and (it), one of the substituents Fl1, R2 and R3 is a hydrogen atom, the corresponding reactants are tertiray reactants; when all the substituents are alkyls, they are quaternary reactants.

The tertiary reactants of formulae (I) and (li) may be obtained by condensation of epihalohydrin with a secondary amine; the amine utilized is a tertiary amine in the case of the preparation of quaternary reactants.

The compounds of formula (I) are very reactant and in the presence of alkaline OH- ions, react with the hydroxyls of the starch. Those of formula (if), under the action of the OH- ions, are converted first into the glycidyl form (formula I) before the condensation on the starch. This transformation is produced in accordance with the following reaction:

with the formation of sodium chloride.

Account must therefore be taken of the alkalinity consumed for this conversion in the adjustment of the proportion of alkaline agent playing the role of catalyst; where it relates to caustic soda and without taking into account the amount necessary for the conversion of the cationic reactant when the latter corresponds to the formula (11), 0.2 to 2% is utilized, preferably 0.5 to 1% by weight of catalyst taking the starch into account.

Advantageous examples of tertiary reactants are: Wiethyiamino-2.3 epoxy propane hydrochloride of the formula:

below denoted by DEAEP, diethylamino-2-hydroxy, 3-chloropropane hydrochloride of the formula:

hereinafter denoted by DEACP.

Advantageous examples of quaternary reactants are: -2,3-epoxypropane-tri methyl ammonium hydrochloride of the formula:

denoted below by TMAEP.

--3-chloro, 2-hydroxypropane-trimethylammonium hydrochloride of the formula:

hereinafter denoted by TMACP.

By operating with the preferred range of 60 to 800C, the duration of the reaction is about 60 minutes.

The starch is generally introduced first and then the cationic reactant is added. After homogenization, there follows the introduction of the alkaline agent; the mixture is then heated to the necessary temperature, advantageously to 60--700C and maintained at this temperature for about one hour. In a modification, it is also possible to preheat the starch to the selected reaction temperature before adding the cationic reactant and the alkaline agent, When the reaction is terminated (the end of the reaction is detected by measurement of the nitrogen), the excess caustic soda is neutralized, for example with adipic acid. Then the powder is sifted if necessary after grinding before placing it in bags.

The determination of the nitrogen level on the final cationic starch is done by the Kjeldahl method.

The cationic starches thus-obtained are not cross-linked and have a high viscosity which exceeds 1000, preferably 1500 and more preferably 2000 Brabender units or B.U., measured at a concentration of 5% of dry matter; this viscosity may, in certain cases, exceed 4000 B.U.

This high viscosity may be obtained whatever the nitrogen ratio.

In addition, starches of viscosity higher than 1000 B.U., can be produced by lowering the amount of caustic soda below 1% by weight.

The yield of the cationization reaction is, in the process according to the invention, about 100%.

This yield is determined by measurement of the fixed nitrogen. This high viscosity can be obtained whatever the ratio of nitrogen is.

To illustrate the foregoing. there are indicated below a certain number of examples of the preparation of cationic starches according to the invention.

EXAMPLE I In a mixer of 200 liters capacity (Lodige" trademark) provided with a stirrer, 100 kg of potato starch having a humidity of 20% are introduced. The mixer is heated with a double jacket up to a temperature of 80CC. There are then added 38 kg of an aqueous solution with 50% of dry matter of TMACP. After a period of stirring of 15 minutes to make the powdered mixture homogeneous, 4792 g of powdered caustic soda are added. It is left to react for 1 hour, then neutralized with 1 368 g of powdered adipic acid. The cationic starch thus-obtained is denoted by the reference IA.

The second test was carried out identically, except as regards the caustic soda, of which 4342 g are added. The neutralization does not necessitate more, in this case, than 546 g of adipic acid. This starch is denoted by 18.

The characteristics (nitrogen ratio an Brabender viscosity) of these two starches are gathered in the following table.

TABLE I

I I Starch Starch IA IB Maximum Brabender viscosity These two cationic starches with high nitrogen ratio have been obtained with a reaction yield very close to 100%. They differ from one another in their viscosity, IB having been formed in the presence of an 0.30% excess of caustic soda instead of 0.75% for IA.

The Brabender viscosity is well known to the technician skilled in the art. It has been measured here on a suspension with 5% dry matter using a gradual rise in temperature of 1.50C per minute up to 920C. The value corresponding to the viscosity peak is then read.

EXAMPLE II As in Example I and in a first test, there is introduced into a mixer of the Lodge type provided with a stirrer and a double jacket, an amount of 100 kg of potato starch having a humidity of 20%. It is heated to 600C.

Then 20 kg of TMACP in 50% aqueous solution namely, 40 kg of solution are added. After being stirred for 1 5 minutes, 4355 g of powdered caustic potash are added and it is stirred for 2 hours. After which, it is neutralized with 544 g of adipic acid. This starch is denoted by ilA.

The same operation is repeated in the second test by using this time the reactant TMAEP of which 17 kg are added in the form of fine powder followed by 400 g of finely ground caustic soda. The neutralization is then effected with 730 g of adipic acid and the starch obtained is denoted by II B.

In a third test, 18 kg of DEAEP is used and added in the form of powder, followed by the addition of 700 g of finely ground caustic soda. The neutralization requires 1278 g of adipic acid and the starch thus-obtained is denoted by II C.

The characteristics of these three starches are gathered in the following table: TABLE II

Starch Starch Starch II A II B II C Nitrogen ratio ( ,% on dry matter) 1.87 2.01 1.92 Reaction yield (%) 97 99 99 Brabender viscosity 3700 3140 2600 It is also observed that the yield of the reaction is excellent and that at a neighbouring nitrogen ratio, the viscosity of the starch is a function of the excess of alkalinity present in the course of the reaction and which is respectively equal to 0.3--0.4 and 0.7% of caustic soda expressed on the starch. EXAMPLE Ill Three other cationic derivatives of starch are prepared by using equipment identical with that of the preceding examples. Three tests are carried out by utilizing each time 100 kg of commercial starch with 20% humidity.

In each test. heating is at 700C for 1 hour and 30 minutes.

In the first test, the reactant is TMACP. 20 kg of a solution with 50% of dry matter of this reactant are added to the starch. Then 2867 g of caustic soda are added. Once the reaction is terminated, it is neutralized with 1368 g of adipic acid. The cationic starch thus-obtained is denoted by lIlA.

In the second test, a solution with 50% of TMAEP, namely 22 kg is used. The reaction is catalysed in this case with 750 g of finely ground caustic soda and 1368 g of adipic acid is used for neutralization.

This starch is denoted by 1116.

In the third test. DEACP was used. 44 kg of a solution with 50% of dry matter is added, and then 4656 g of finely ground caustic soda. The neutralization requires 547 g of adipic acid. This starch is called 1INC.

The characteristics of these three starches are as follows: TABLE Ill

Starch Starch Starch Ill A III B Ill C Nitrogen Ratio (% on dry matter) 1 1.3 1.9 Reaction yield (%) 100 97 99 Brabenderviscosity 2000 1500 3600 The reactions are effected respectively with 0.75%,0.75% and 0.3% of excess alkalinity expressed as caustic soda.

The uses in accordance with the invention of the cationic starches obtained in accordance with the invention will be illustrated by the following examples.

EXAMPLE IV An amount of 400 kg of potato starch having a humidity of 20% is introduced into a mixer provided with a double jacketed-stirrer. It is heated to 650C and an amount of 7.8 kg of TMAEP in the form of fine powder is introduced. Then, 2000 g of powdered caustic soda are added. After a contact of 1 h 45 mn, it is neutralized with 5100 g of adipic acid. This starch is denoted by "Starch VI 1", and has the following characteristics: Nitrogen ratio (% on dry matter) 0,23% Reaction yield (%) 100 Brabender viscosity 1050 EXAMPLE V Use of cationic starches produced in accordance with the invention as liquid retention agents.

As already indicated, the cationic starches according to the invention have remarkable liquid retention properties.

Notably, they can be added, in any proportion, to cellulose suspensions which are used for the manufacture of diapers for infants, hygenic towels, surgical bandages, and other similar products.

The cationic starches in accordance with the invention have been tested as follows.

On the cellulosic pulp (the upper and lower non-woven sheets being included) a disk of 10 cm diameter was cut out. The cellulosic pulp of this disk alone is taken and cationic starch powder according to the invention was incorporated intimately therewith, the proportion of powder with respect to the cellulosic pulp being 10%. Numerous means can be used to ensure good distribution of the powder. It is possible, for example, to slightly moisten the pulp and to dry it after having glued the particles on to the cellulosic fibers.

After this operation, the disk of 10 cm diameter is reconstituted from the cellulosic pulp and it is replaced between the two non-woven parts.

The cellulosic disk is weighed before and after incorporation of the cationic starch powder.

In addition, 3 crystallizing dish of 40 cm diameter and of useful capacity of 500 cm3 is fiiled with saline water of the following composition: -urea 20.5 g/l -NaCI 8.4 g/l MgSO4,7H20 1.168gI1 HaCI2,2H20 0.655 g/l -K2S04 2.09 g/l -amaranth dyestuff 0.105 g/l -surface-active agent known under the trademark TFlITONX 100 0.105 g/l so that the crystallizing dish is filled to a height of 35 mm.

The cellulosic disk is completely immersed in the abovesaid solution for 2 minutes (the celulosic disk being placed on a sieve of rectangular format of 300 x 100 mm, and mesh width of 3 x 3 mm).

The sieve bearing the cellulosic disk is withdrawn from the solution and left to drain for 30 seconds in the horizontal position.

The cellulosic set is separated from the sieve and it is placed between two glass plates of 300 x 100 mm. A weight of 10 kg is placed on the upper plate and it is left under pressure for 2 minutes. This method is applied to 10 cellulosic disks treated in the same manner.

By measurement on a cellulosic disk containing no starch according to the invention, the absorbing power of the cellulose under the conditions of the test described is known. The absorbing power of the cationic starch according to the invention is determined by difference.

To show the superiority of the starches according to the invention, the retaining power measured above is compared with that of commercial infants diapers.

The results are gathered in Table IV.

TABLE IV

Amount of saline water in grams retalned per gram of diaper or of cellulosic pulp Absorbent Substrate treated with cationic starch Diaper based on starch acrylonitrile copolymer 24.76 g of American origin Cellulosic pulp treated 24.02 g with the product IA Cellulosic pulp treated 43.42 g with product IB Diaper based on acrylic 43.40 g polymer of American origin It is observed that with the cationic starches according to the invention, performances corresponding to those of commercial products are obtained.

EXAMPLE VI Application of cationic starches obtained in accordance with the invention simultaneously as thickening agents water retainers.

These starches can be used in the plaster industry and more precisely for the manufacture of plaster to be sprayed.

in fact, plasters of this type need a very particular rheology.

Plaster to be sprayed must, among other adjuvants, contain a thickening agent which permits, as shown in the accompanying drawing the rheology of the plaster to be modified, essentially in the hour which follows mixing. After 1 hour, the thickening action can be attenuated since the setting of the plaster is then sufficient. Moreover, the plaster to be sprayed must also contain a water retention agent.

This retention agent must enable the better retention of water so that it is possible to work the plaster under the best conditions for a suffieciently long period. This retention action must cease after a time generally estimated at 1 hour--l hour 30. The sweating (ressuage) which then occurs enables good smoothing (lissage) of the plaster.

Plaster to be sprayed contains, generally, in addition, one or several germination retarding agents (keratin, protein and the like), one or several development retarding agents (phosphates, lime, lime and phosphates associated. tartaric acid, gluconic acid and the like).

A gypsum of the Paris region contains, for example, 0.5 to 1% of lime, 0.3 to 1% of retarding agent according to whether it is phosphate or an amino- agent The retention agent is currently, in the present state of the art, a hydroxyethylcellulose or a methyl cellulose or any other product of this group.

The thickening agent is currently carboxymethylcellulose.

The cationic starches according to the invention can play, contrary to hydroxyethylceilulose or methylcellulose, the double role of thickening agent and water retention agent.

In the tests, a plaster of Paris containing notably 1 0/0 O of lime and 0.3 0/0 O of keratin and various other ingredients, except for thickening and water retention agents, was used.

A mixing is carried out, in the dry, as homogeneously as possible, with various proportions (0.25, then 0.5, then 1.0 and 1.5% by weight) of cationic starches according to the invention. By-way of control, a conventional formula with hydroxyethylcellulose (HEC) and with carboxymethylcellulose or CMC (total proportions 0.35% and 0.845% by weight), was taken. The various powders thus-obtained are mixed with water in the ratio plaster/water of 200/100.

The water is previously introduced in a perfectly clean capsure. The plaster containing the various adjuvants, is rapidly sprinkled in 1 5 seconds on to the surface of the water and then mixed with the ladle for 30 seconds. The paste is poured one minute after the start of the mixing into a ring (diameter: 55 mm, height: 55 m). The bottom of this ring is constituted by a superposition of paper filters of standardized quality. The filters, minus the upper filter, are weighed after a contact of 1 5 minutes with the paste. The weight of water absorbed constitutes the measurement of the water retention of the product. The retention will be ail the better as the weight is low at the lowest percentage of product applied.

The cationic starches used are those identified above by IIA, lIB, and IIC.

In the Table V, the results of this test are gathered.

TABLE V

Weight in grams of water retained for a proportion in % of cationic starch or of CMC + HEC mixture of Agent used 0.25 0.35 0.5 0.845 1 1.5 Product II A 3.60 1.85 0.31 0.09 Product II B 3.39 1.28 0.18 0.09 Product II C 2.86 1.87 = 0.41 0.16 HEC + CMC 1.78 0.09 These results show that, taking into account the cost of these various products, the cationic starches according to the invention are particularly interesting.

The samples of plaster supplemented with cationic starches according to the invention and of the mixture HEC + CMC have been subjected to a second test by resorting to a shaking table (standard NF B 12303).

The results are gathered in Table VI below.

TABLE VI

Diameter in mm of the spreading surfaces obtained with a proportion (in %) of cationic starch or of the mixture OMO + HEC of Agent used 0.25 0.35 0.5 0.845 1 1.5 Product lIA 150 150 ~ ~ 140 140 Product 118 160 i 160 150 150 Product IIC 140 150 140- 150 HEC+CMC 170 160 The plaster without thickening agent, nor retention product shows a water retention of 3.34 g and a spreading of 230 mm. If the figures are low and the results very appreciable as soon as 0.5% of one of the products according to the invention is introduced, it can be observed that the thickening power is considerable and that it is very little influenced by the ratio of incorporation, which leaves every latitude for adjusting the water retention.

EXAMPLE VII Application of cationic starches prepared according to the invention in the paper industry as retention agent for fine fibers and fillers.

It has been found that the starches according to the invention used alone or associated with traditional cationic products with a low nitrogen ratio and with a low viscosity less than 1000 B.U..

enables a further improved functioning of paper making machines. In fact, it is possible to retain four essential criteria: retention of the fine fibers retention of the fillers draining on a gauze-speed of the machine physical characteristics.

The cationic starches, subject matters of the invention, do not bring any additional improvement on the level of physical characteristics when they are compared with known cationic products. On the other hand, for the retention of the fine fibers and of the fillers, the improvement is very appreciable.

To exhibit this improvement, the preparation of circular paper sheets of weight of 70 g per m2 on a handsheet former ("formette") of LHOMARGY trademark was carried out. For this test a leafy wood pulp which has been treated with bisulphide and bleachet slightly and which has been refined at 200 Shopper (French standard Q 50-003) was used. This paste was filled with 10% of titanium oxide. It also contained 4% of alumina suiphate. Its concentration was 3 g per liter. In this way, the results explained below were obtained.

If it is assumed that the retention offered by a conventional cationic product with a low nitrogen ratio and a low viscosity based on potato starch is equal to 100, the cationic starches according to the invention enable for superior results to be recorded: Product IIIA: 114.7 Product 118: 119 Product IIC: 118.3 The improvement observed is about 1 5 to 20%. The material balance is hence very favorable. The operation of paste recovery agents is then found to be considerably improved and it is certain that the user would have a pollution balance sheet which is even more satisfactory. In the same way, the draining or elimination of water on the endless wire of the paper machine is considerably improved. This aspect has been established by the use of the measurement of the degree of refining (standard relative to the degree of draining or of refining NF Q 50-003) for which as a control there was used a leafy wood pulp refined at about 500 Shopper. In a second stage, the same measurement was carried out on the same pulp containing 0.5 or 1% of the various products concerned.

The following measurements were recorded, the control being constituted by the pulp alone and which had given 560 SR (SR = Shopper degree).

The results are gathered in Table VII.

TABLE VII

'SR for 0.5% 1 % Conventional cationic starch with a low degree of substitution (potato starch base) 42 36 Product lIlA 27.5 22 Product 1118 22 18.5 Product llB 22 20 Product 110 24.5 j 19 Product IIIC 20 20 The improvements are very considerable. On the paper making machine, the use of such products is manifested by a very substantial increase in the speed of the machine.In addition, the products of the invention enable the pulp to be refined even more, without loss of speed, more considerable refining being often synonymous with superior physical characteristics through the much more numerous interfibre linkages that it enables.

The improvements contributed to the fine fiber and filler retention and especially to the speed of water removal are so considerable that it is unnecessary to use obligatorily the cationic starch according to the invention alone. Notably to improve the draining, it would be very possible to contemplate, in any proportions, mixtures of the starches according to the invention with conventional cationic starches.

EXAMPLE VIII The cationic starches obtained according to the invention are soluble in water and their nitrogen ratio is such that their rheology is very special. In particular, the aqueous solutions of these starches (concentration of O to 40%) are stable. Such characteristics enable the use of the starches according to the invention in water paints or emulsion paints notably, but also in inks and scouring varnishes by selecting the solvent used judiciously. In particular, the easiest case is that of water paints for which it is possible for example, to propose the following formula: Product lIB 20 parts Ethyleneglycol 20 parts Aluminium powder 26 parts Dimethylolurea 2 parts Ammonium chloride 1 part Sodium laurylsulphonate 2 parts Water q.s.p.

The products of the invention thus advantageously replace both the polyvinylalcohol whose indispensable amounts are far greater than the cellulose ethers which are more expensive.

EXAMPLE IX Application of the cationic starches produced according to the invention as thickening agents for textile printing.

Their rheological properties and notably their very high stability and onctuosity enable the use of the cationic starches according to the invention for the printing of textiles. It can come into all formulae where the use of British gum. of starch ether or of various gums are generally required.

It is possible, for example, to cite a possible formula with basic dyes for cotton printing.

The typical formula could be: 10 g of basic dye 50 g of plasticizing agent for modifying the rheology such as Solutene C.l. (FMC) or Lyoprint G (Ciba) based on thiodiglycol 100 g of 40% acetid acid 170 9 of water 20 g of tartaric or gluconic acid.

The solution is poured into 280 g thickening agent corresponding to Product 118.

After cooling, 50 g of tannin are added. This amount can easily be brought to 20 g. In fact, the basic dyes do not have affinity for the cotton fiber and the tannins are necessary for the fixing of the dyes. The highly cationic character of the starches according to the invention facilitates the fixing and permits the reduction, even the elimination of the tannins. In addition. the starches according to the invention have a very high viscosity and, in the above-indicated formula, it is necessary to add generally about 600 g of conventional thickening agent. There is hence a substantial reduction in the amount of thickening agent.

EXAMPLE X Application of the cationic starches obtained according to the process in accordance with the invention but possessing a conventional nitrogen ratio, in the paper industry.

In example VII relating to paper industry, cationic products according to the invention and possessing a high nitrogen ratio have been taken into account. In this example, the same application is taken into consideration but with respect to far less substituted products. These products are, as in example VI1, compared to cationic products of conventional type, with a low viscosity, obtained in aqueous phase, the comparison criteria being still: retention of the filiers, of the fibers, draining (elimination of water on an endless wire) and the physical characteristics.In the same way as for the highly substituted products, the more weakly substituted products obtained by the process according to the invention do not possess better physical characteristics. (tensile strength, Mullet factor and tearing strength, bending and internal cohesion) than the traditional cationic products obtained from a milk.

On the contrary, for a same substitution degree, measures according to standard Q 50-003, applied as in example VII give the following values:

'SR for 0.5% 1 % Conventional product obtained from a milk phase 40 35 Product ill A Product 111 B 39 35 Product VI 1 35 30 The draining degree is not as good as for the highly substituted products, which appears to be logical, but, for a same substitution degree, the dry method enables to obtain products which are superior with respect to those obtained in milk phase.

Considering, as well, the retention test such as described in example VII, the measures are the following ones: Conventional cationic product obtained in aqueous phase 100 Product Ill A 108,4 Product Ill B 106 Product VI 1 109,9 In this field, a clear superiority of products obtained by the dry method is again noticed, as regards the products obtained by the milk phase, with the same degree of substitution. As a matter of fact, at ^e revei of the epuration plant. pollution is twice as low, from the above mentioned data.

If superiority is anyhow a little less high when the products are more weakly substituted, it still remains very obvious. The speed of the machine and the retention of fine fibers and fillers are essentially improved.

As a result of which and whatever the embodiment adopted, there are thus provided cationic starches with a high nitrogen ratio and a high viscosity and which have, with respect to those existing hitherto, numerous advantages including notably that of being involved in new applications.

As is self-evident and as emerges already from the foregoing, the invention is in no way limited to those types of application and embodiments which have been more especially contemplated; it encompasses, on the contrary, all modifications.

Claims

1. A process for the cationization of starch consisting of reacting in the dry state granular starch with a cationic reactant, the reaction being carried out at a temperature of 20 to 900C, in the presence of an alkaline agent.

2. A process according to claim 1, wherein the reaction is carried out at a temperature of 600C to 800 C.

3. A process according to claim 1 or claim 2, wherein the alkaline agent is caustic potash or lime.

4. A process as ciaimed in claim 1 or claim 2, wherein the alkaline agent is caustic soda.

5. A process according to any of claims 1 to 4 wherein the cationic reaction is an epoxy compound of the formula (1):

in which each substituent R,, R2 and R3 is a methyl or ethyl radical with one of R,, R2 and R3 optionally being a hydrogen atom and Xe represents CI-, Br I.

6. A process according to claim 5, wherein each substituent R1, R2, and R3 which is a methyl or ethyl radical is the same.

7. A process according to claim 5, wherein the cationic reactant is 2,3-epoxy propyl-diethyl ammonium chloride or 2, 3-epoxy propyl trimethyl ammonium chloride.

8. A process according to any of claims 1 to 4. wherein the cationic reactant has the formula (all):

where R,, R2 and R3 and Xe have the meanings given in claim 5 or claim 6 and X represents CI, Br or I.

9. A process according to claim 8, wherein the cationic reactant is 2-hydroxy-3-chloropropyl- diethyl ammonium chloride or 2-hydroxy-3-chloropropyl-trimethyl ammonium chloride.

10. A process according to any of claims 5 to 9, wherein the amount of cationic reactant used is such that the nitrogen ratio of the cationic starch obtained is higher than 0.95 and at the most equal to

2.8.

11. A process according to claim 10, wherein the amount of cationic reactant used is from 0.5 to 60% by weight based on the starch.

12. A process according to any one of claims 4 to 19, wherein the amount of alkaline agent used is from 0.2 to 2% by weight based on the starch when the cationic agent used is that of formula (I), the amount being increased, when the cationic agent is that of formula (II), by a proportion corresponding to that required for the neutralization of the agent of formula (II).

1 3. A process according to claim 12, wherien the amount of alkaline agent used is from 0.5 to 1% by weight based on the starch, when the cationic agent is that of formula (I).

14. A process according to claim 1 conducted substantially as described in any one of examples 1 to 11 herein.

1 5. Cationic starch whenever prepared by operating a process according to any one of claims 1 to 14.

1 6. The use of a starch according to claim 1 5 as a liquid retention agent.

1 7. The use of a starch according to claim 1 5 as a thickening agent.

1 8. The use of a cationic starch according to claim 1 5 as a fine fiber and filler retention agent in the paper industry.

19. The use of a cationic starch according to claim 15 as a draining agent.

20. The use according to claim 16, in the manufacture of babies' diapers.

21. The use according to claim 16, in the manufacture of plasters.

22. The use according to claim 17, in the paint, ink or varnish industry.

23. The use according to claim 17, in pastes used in textile printing.

24. The use according to claim 19, in the paper industry.

25. The use according to claim 16, substantially as described in either example V or VI herein.

26. The use according to claim 17, substantially as described in either example VI or IX herein.

27. The use according to claim 18 and 19 substantially as described in any of examples VII, yIll and X.