DK143945B - APPLICATION OF Aqueous SOLUTION OF DICALIUM CYCNAMIDE FOR WATER SOLUBILITY OF STARCH MILK - Google Patents

Description

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PATENT AND TRADEMARKET DIRECTORATE

(21) Application No. 5082/77 (51) | nt.CI.3 C 09 J 3/06 (22) Filing Day 7 · Jul. 1977 (24) Race day 7 · Jul. 1977 (41) Aim. available Jan 10 1978 (44) Submitted Nov. 2. 1981 (86) International application no. "(86) International filing day" (85) Transfer day "(62) Master application no."

(30) Priority 9- Jul. 1976, 7621140, FR

(71) Applicant ROQUETTE FRERES, 62156 LeBtrem, FR.

(72) Inventor Guy Fleche, FR: Michel Huohette, FR.

(74) Clerk of International Patent Bureau · (54) Use of an aqueous solution of dicalluracy oil for water dissolution = solubilization of starch adhesives.

The invention relates to water insolubilization of starch adhesives, especially such for use in the manufacture of corrugated board.

It is well known to use resins, especially urea or melamine and formaldehyde resins, derivatives thereof, and salts thereof, and polymers thereof, as agents suitable for making starch adhesive moisture resistant or even water resistant or to give it a high wet strength.

X) ^ To make starch adhesives water resistant, it is also known simultaneously to use, in an alkaline medium, formaldehyde - or ^ a derivative or polymer thereof - and calcium cyanamide which reacts with the starch and with the formaldehyde which imparts the glue its moisture resistance.

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In fact, only technical calcium cyanamide, whose purity is less than 65%, has been truly tested and used.

Indeed, the content of impurities in technical calcium cyanamide - in particular carbon, chalk and calcium carbide - is sufficiently low in terms of the volume of the treated adhesive to not substantially affect the moisture resistance properties of the adhesive assemblies. Accordingly, the technical calcium cyanamide provided fully satisfactory properties from an insolubility point of view of the starch adhesive.

On the other hand, the use of technical calcium cyanamide causes copious deposits in the tubes of the machines used in the manufacture of moisture resistant starch adhesives, which deposits require frequent cleaning and consequently stoppages of these machines.

U.S. Patent No. 3,019,120 discloses the insolubilization of starch adhesives by means of calcium cyanamide and states that other alkaline salts of cyanamide are also considered for this purpose.

Not only calcium cyanamide, but also e.g. disodium cyanamide, however, causes certain changes in the properties of the starch adhesive, which complicates its use, as will be further explained below.

However, it has surprisingly been found that dipotassium cyanamide substantially reduces such undesirable changes in the properties of the adhesive, so the present invention relates to the use of an aqueous solution of dicalcium cyanamide having a solids content of at least 30% for water insolubilization of starch adhesive consisting of a mixture of starch milk and gelled starch containing formaldehyde or a derivative or polymer thereof, wherein the solution is used in an amount equal to 0.1-20% by weight of dicalcium cyanamide based on the starch-containing material.

The use of such a solution as just defined for the insolubilization of starch adhesive gives surprising and unpredictable the possibility that in a given apparatus for making corrugated board it is possible to use and, as needed, one and the same adhesive without any adjustment of the basic composition.

Thus, in practicing the invention, it is possible in an apparatus for making corrugated board to provide this apparatus with a standard non-moisture-resistant corrugated board, the usual standard adhesive, the composition of which depends on the nature of the intended fabrication, i.e. whether For example, if the production is changed to produce moisture-resistant corrugated cardboard, continue to use the same adhesive only while admixing the dipotassium cyanamide solution of the present invention with the addition of formaldehyde.

This will not be possible using calcium cyanamide nor with certain other alkali metal salts of cyanamide. When the cyanamide is not added as the dipotassium salt, the composition of the adhesive and the working characteristics of the corrugated board manufacturing apparatus must be adapted before moisture-resistant corrugated board can be manufactured.

The particular advantage which is obtained from the use according to the invention is, inter alia, that the use practically does not affect the gelling point of the starch present in the glue. Furthermore, adding the aqueous solution used according to the invention causes virtually no change in the viscosity of the adhesive and the resulting adhesive is storage resistant.

The difference between the results obtained in the application of the invention and the results obtained with calcium cyanamide and disodium cyanamide is shown in the following test results which illustrate the changes as regards gelling point, stability and viscosity: The following solutions were compared: a 27.2% calcium cyanamide solution corresponding to 13.6 wt.% CN2 ions (hereinafter referred to as CC) a 31.4 wt.% disodium cyanamide solution, corresponding to 14.6 wt.% CN2 ions (hereinafter referred to as CS) a 38.6 wt% of dicalcium cyanamide solution (corresponding to 13.1 wt% CN2 ions) (hereinafter referred to as CP).

The glue used was prepared by heating 50 kg of standard starch in 450 liters of water to 50 ° C and adding 9 kg of sodium hydroxide in 20 liters of water followed by stirring for 10 minutes and subsequent addition of a mixture produced by stirring 250 kg of standard starch and 6 kg. borax in 750 liters of water for 10 minutes.

The amount of cyanamide solution used was 10 kg and a further 9 liters of 30% formaldehyde solution was added.

To determine the gelling point, a portion of this corrugated cardboard paste was transferred into a Brabender mixer and the temperature was raised at 1.5 ° C / min. The temperature at which the viscosity suddenly rises sharply is called the gelling point.

Furthermore, in adhesives having a composition approximately as described above, the temporal change of Lorry viscosity (Hecher-Ford) at 30 ° C over 17 hours, Brookfield viscosity at 30 ° C over 17 hours has been measured. and the Brabender viscosity at 35 ° C for 1 hour.

The results are given in the tables below.

Table 1

Gelling Point

Control CC CS CP

(no cyanamide) _

Temp ° C 49.5 54 44 48

It is clear that the calcium and sodium salts affect the gelling point of a classically prepared glue: for CC: ΔΤ = 4.5, i.e. 9% for CS: ΔΤ = -5.5, i.e. -12% In contrast, using the potassium salt results in only a minimal temperature difference, (ΔΤ = -1.5 ° C), which corresponds to a change less than 3%.

Table 2

Lorry viscosity

Control CC CS CP

0 hours 19 23.5 19.5 16.5 0 hours 30 min. 21 27.5 27 26 1 hour 21 35 32 28 2 hours 21 37 35 4 hours 41 50 34 17 hours 90 63

The viscosity is given in seconds. It appears that with the potassium salt, a slower viscosity increase is obtained than with the other salts.

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Table 3

Brookfield viscosity

Control CC CS CP

0 hours 260 280 270 230 0 hours 30 min. 260 300 310 300 1 hour 260 340 340 310 2 hours 260 340 350 4 hours 370 430 17 hours 600 460

These results show the same trend as the results in Table 2.

Table 4

Brabender viscosity

Control CC CS CP

Initial viscosity 240 260 210 160

Final viscosity 270 380 570 230

Viscosity change 30 120 360 70% 12.5 46 170 44

In particular, it is noted the sharp increase in viscosity caused by the sodium salt.

Thus, the use of the invention provides significant advantages over the insolubilization previously used with other cyanamides.

For the preparation of the dipotassium cyanamide salt from technical calcium cyanamide in suspension in an alkaline aqueous medium, moles of pure calcium cyanamide, partly an amount of technical KOH containing 0.8 to 3.0 moles of pure KOH, and an amount of potassium carbonate of 0.4 to 1.5 moles; the reaction is carried out in the presence of potassium carbonate at a pH of at least 12, or the dicalcium cyanamide salt is prepared from hydrogen cyanamide using 2 moles of pure KOH per day. moles of hydrogen cyanamide at a pH of at least 12.

The invention will be explained in greater detail by means of the following description and the accompanying examples which indicate preferred embodiments of the invention.

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To make a starch adhesive moisture resistant, ie. making it water-insoluble is the procedure as follows or similar.

It should first be remembered that starch adhesives, as used in the industry, especially for the manufacture of corrugated board, are composed of a first fraction consisting of a suspension of starch or starch milk and a second fraction of gelatinized starch (under the influence of alkali, especially sodium hydroxide) or "carrier" in which the starch milk is dispersed.

These types of adhesives generally have approx. 20% dry matter content.

To make them water resistant, formaldehyde or a derivative or polymer thereof is added to the adhesive together with an aqueous solution of the dicalcium cyanamide salt.

The dicalium salt of cyanamide is preferred over the monocalcium salt and over the mixture of monocalcium and of the potassium salt because of its greater stability and better performance, especially in the manufacture of the single corrugated cardboard glue (to which, in contrast to double corrugated board with two plates sides of the "medium" (corrugated board), a glue with a higher breaking point is used).

The amount of dipotassium cyanamide salt added to the starch adhesive, as well as the amounts of formaldehyde, vary in a wide range: 0.1 to 20% with respect to the starch depending on the desired water resistance, the paper used, the adhesive deposits and the passage rate over the machine.

Generally, as used, the dicalcium salt solutions have concentrations of 400 to 500 g / ml. liter.

It is believed that the dicalcium salt of the cyanamide reacts with the starch to form a substituted pseudourea, especially starch iminocarbonate; this compound could react with the formaldehyde, especially at the time of drying (high temperature) to form crosslinked compounds after passing through an intermediate form such as starch methyloliminocarbonate. The extended crosslinking could be the cause of the glue's water resistance. This crosslinking could take place with the cellulose substrate in the cardboard or paper, which would explain the notable performance.

For the preparation of the dipotassium salt of the cyanamide it is possible to proceed as follows.

The preparation is carried out either from technical calcium cyanamide or from hydrogen cyanamide by reacting this starting material with potassium hydroxide with or without the presence of potassium carbonate to improve the filterability in the first case.

When technical calcium cyanamide is used as the starting material, it is suspended in an aqueous KOH solution (pH at least 12) by stirring; it is all heated to 50 ° C for a sufficient time for the reaction to take place; in practice, this period usually does not exceed 30 minutes. Then, by filtration, a separation of the insoluble products consisting of chalk, carbon, calcium carbide, calcium carbonate, unreacted calcium cyanamide and insoluble nitrogen products is carried out.

A cake that is colored black is obtained due to the presence of carbon.

The filtrate contains the potassium salt of cyanamide, sometimes excess of KOH or urea resulting from light decomposition. It has a greater or less pronounced yellow color and it has a high pH - of the order of 12 - due to the hydrolysis of its salts, the hydrogen cyanamide being a weak acid.

To ensure that the filtrate contains only the dipotassium salt, an amount of KOH which is at least sufficient to satisfy the stoichiometric conditions may be added. Generally, at least 2 moles of KOH per day are used. moles of hydrogen cyanamide or 2.5 moles of KOH per

moles of calcium cyanamide. One modification consists of adding at least * 1.25 moles of KOH followed by 1.25 moles of potassium carbonate per liter. moles of calcium cyanamide.

When hydrogen cyanamide is used as the starting material, the latter is neutralized with KOH. In order to avoid the occurrence of a pH in an area that facilitates the formation of dicyanamide (pH 6-10) and cyanuric acid (pH 10-12) during the neutralization process, the hydrogen cyanamide is poured into an aqueous solution of KOH (at pH 12), with stirring, and under cooling to avoid bringing the product to a temperature above 30 ° C, which would result in decomposition for cyanuric, urea, ammonia and other substances.

The dipotassium salt thus obtained can be presented in dry form, in a pure state or on a carrier or in solution. It is used in the form of an aqueous solution.

Its stability at elevated temperatures is a function of the dry matter content.

An undesirable decomposition in the product occurs, especially for cyanurea, dicyanamide, urea, potassium carbonate, etc., both as the temperature rises and when the solids content of the solution decreases.

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To examine the stability, the number of molecules of dicalcium salt remaining after different time periods was determined by testing samples of dicalcium salt with increasing solids content and kept at different temperatures.

The following tables indicate the number of molecules remaining after each measurement for 100 molecules of starting salt.

Table I Table II

(30 ° C) (40 ° C) 1 0 2 3 6 10 Jld 1012367 10 days_ days__ 5 DM + 100 83 61 54 5 DM 100 80 75 69 52 50 44 20 DM 100 84 82 80 20 DM 100 80 78 81 30 DM 100 91 89 87 30 DM 100 89 89 89 38 DM 100 100 100 99 99 38 DM 100 100 99 98 DM + = dry matter content in S.

Therefore, the dicalium salt is used with a dry matter content of at least 30%. In the dry state (the drying can be carried out, for example, by resorting to a conventional crystallization from a supersaturated solution), the salt is stored very easily without decomposition.

To show the superiority of the dicalcium salt over the monocalcium salt, the same experiments were performed with the latter, and the results are reproduced in the following tables.

Table III Table IV

(30 ° C) (40 ° C)

Time in 0, Time in Λ, 0,, _ days 0 2 3 6 days 0 1 2 3 6 7 5 DM + 100 66 56 5 DM 100 65 59 54 41 40 30 DM 100 73 68 30 DM 100 73 68 DM * = dry matter content in%.

The following examples relate to the preparation of the dipotassium salt of cyanamide, as well as the use of the invention to render starch adhesives water insoluble.

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Example 1

Preparation of the dipotassium salt from calcium cyanamide and from a mixture of KOH and potassium carbonate.

To a 2000 liter tank equipped with a stirrer with a heat hose for the water supply pipe and the technical KOH as well as a measuring base, 1080 liters of water, 800 kg of 50% technical KOH and 324 kg of potassium carbonate are successively introduced and the contents are stirred and heated to 50 ° C for approx. For 30 minutes, 600 kg of calcium cyanamide with a purity of 50% is added, the contents are allowed to react for 1 hour and then filtered. 660 liters of filtrate was obtained with 285 g of pure dipotassium salt per liter. which also contained small amounts of decomposition products, especially dicyanamide, cyanurea, etc.

Example 2

Preparation of the dicalcium salt from hydrogen cyanamide.

To a 2000 liter tank equipped with a stirrer, with water inlet pipe, technical KOH, hydrogen cyanamide in solution and a cooling hose, successively add 1040 kg of 50% technical KOH and 400 kg 50% aqueous solution of hydrogen cyanamide. The temperature is kept below 25 ° C for 1 hour. 1.4 tons of dicalcium cyanamide is obtained at 500 g / ml. liters containing the same traces of impurities as given in the examples of Example 1.

Example 3 In the laboratory, starch glue is made insoluble as follows.

For a starch glue obtained from a carrier of the following composition: 3 300 cm water, 33 g maize starch and 5 g pure caustic soda (diluted before the addition), and a starch milk of the following composition: 3 500 cm water, 167 g maize starch and 47 g borax, 10 g of a solution of dipotassium cyanamide prepared as indicated in Example 2 is introduced as well as of 6 g of technical formaldehyde solution.

Instead of introducing the dipotassium cyanamide salt into the glue, it can be introduced into one of its constituents, the carrier or the milk. Samples are taken immediately after the provision of the insolubilized adhesive, then 2 hours and 4 1/2 hours thereafter. From these tests, a double bonding is made by applying the corrugated material to single corrugated cardboard on a plate on which a thin film of adhesive had already been applied, whereby the adhesive is applied to the corrugated peaks. With gentle pressure for a few seconds, the corrugated tops of the corrugated material were applied to a sheet of kraft paper placed on a hot plate heated for example. to 12 ° C. The cardboard thus produced is then cut and tested according to Method No. 9 of F.E.F.C.0 (European Federation of Corrugated Cardboard Manufacturers), by which moisture resistance is measured.

The three samples have a moisture resistance of 100%.

Accordingly, the crosslinking reaction that makes the starch adhesive moisture resistant is practically instantaneous.

Furthermore, the adhesive, which is insoluble, stays ready for use in 1 to 2 switching teams (with a switching time being 8 hours).

Similar experiments have been carried out with potato starch instead of corn starch as the starch base, or with waxy corn starch, tapioca and derivatives thereof hydrolyzed with acid, oxidized with sodium hypochlorite, esterified or etherified.

Example 4 On an industrial scale, a corn starch glue was rendered insoluble as follows.

For a starch glue obtained in a carrier of the composition: 900 liters of water 100 kg of corn starch 15 kg of pure NaOH introduced in the form of a technical solution with 45% dry matter to disperse a starch of the following composition: 1500 liters of water 500 kg of corn starch 14 kg Borax was introduced under stirring at ambient temperature: 20 kg of a solution of the cyanamide dipotassium salt with 38% dry matter after dilution in 30 liters of water and 18 liters of 33% technical formaldehyde.

In this way 3000 liters of moisture resistant starch glue were obtained.

This glue was used in a corrugated cardboard machine.

After using all the glue, an inspection of the machine showed