NO152564B - STARCH MILK WHICH IS SENSITIVE ABOUT PRINT COLORS - Google Patents

Description

The present invention relates to a starch adhesive which is insensitive to printing inks, suitable for the production of corrugated board, comprising a starch component and washing water from flexography installations.

Starch glue is generally provided by using one of three known methods where the first, namely the Stein-Hall method, uses a mixture of a suspension in water of gelatine (called "primary") and a starch milk (called "secondary"), where the gelatinized starch in the suspension serves as a "carrier" for the starch grains in the milk.

According to the second method, a starchy milk is used in which the grains are subjected to a partial gelatinization and which therefore makes the use of a carrier redundant; these adhesives are usually referred to as "non-bearing".

According to the third method, a simple dispersion in water of the product is used which is ready for use and these products include at least a part which is soluble in cold water (which for example consists of a starch product, carboxymethyl cellulose or polyvinyl alcohol) , one part granular starch and one part an alkaline agent.

Flexography is a printing method that is usually used to print corrugated cardboard and where printing inks are used whose composition is complicated, where the main ingredients are dyes, solvents, surfactants and

in others.

Furthermore, the washing water from washing the installations (vessels and press) for flexographic printing and which use flexographic inks, raises serious problems from a pollution point of view and which cannot be regulated without another form of process.

The use of a purification station does not seem to be appropriate with the volume and the concentration in the water to be treated (concentration in the order of 1 to 3%). It is, on the other hand, clear that even if the company

> had a cleaning station, this would not be effective in most cases when it came to washing water from printing machines that had used flexographic inks, since these are very different from each other and it is very difficult to predict re-

the actions on the wash water at the treatment station.

Because of these factors, it has already been proposed to add the wash water containing flexographic colors to the glues to be used for the production of corrugated board, it can be recycled after the flexographic printing and this possibility will in this respect depend on the color parameter.

It has been shown that even if a relatively large percentage of the printing inks are compatible with starch glue for corrugated board, a part of them will have properties which lead to a large degree of incompatibility and they will act in an unfavorable way with regard to the gelatinization and consequently on the viscosity of the glue.

To illustrate these disadvantages, glue has been produced for corrugated cardboard with a double surface. This designation "glue for double surface" is used for a special glue for gluing another layer or paper on a system consisting of grooved coverings that have been narrowed in advance.

These adhesives are produced according to the Stein-Hall method

which consists of preparing a "carrier" by gelatinizing a part of starch with soda and then adding water, raw starch and borax.

In practice, you mix 450 l of water and 50 kg of corn starch, which you heat to a temperature of 45°C before adding 9 kg of soda, where this amount makes it possible to gelatinize the starch.

The mixture is stirred for 15 minutes, after which the following is added:

water 700 litres

starch 250 kg

borax 6 kg

The mixture is stirred for 15 minutes, after which 35 kg of flexographic ink is added, which corresponds to 5% water in the second part.

For standardization purposes, the printing ink has previously been brought to a viscosity of 20 seconds measured at Ford cut no. 4.

For the different preparations with different far-

we measure:

- The Lory viscosity (flow length viscosity with an apparatus from Braive Instruments) - Brookfield viscosity (shear viscosity measured with a Brookfield RVF viscometer - the gelatinization point determined with a Brabender viscograph, where the last measurement consisted of heating the preparation in the viscograph and measuring the temperature where the raw starch in the second part is gelatinized, where this leads to a rapid increase in viscosity.

The results with eleven flexography colors are reproduced in Table I.

It appears from the table that all the printing inks have a very bad effect on the gelatinization point. They disturb it several times significantly and always in the direction of an increase.

Several printing colors have an impact on the viscosity. However, because the wash water with printing colors is a mixture, in practice at least one color will always be unfavorable for viscosity.

Because of these disadvantages, the users of flexographic inks have in practice abandoned the attempt to use the wash water in the starch glue.

In order to overcome the aforementioned difficulties, it has already been proposed, before using the wash water in the adhesives, to remove the harmful constituents in the printing inks by decanting with subsequent removal by filtration.

Such methods are difficult and require substantial use of material, which has led to such attempts being only partially carried out by the users.

The purpose of the invention is to avoid these disadvantages

and providing starch adhesives which are insensitive to printing inks and which make it possible to use washing water from flexographic machines in glue for corrugated board without this causing annoying changes in the gelatinization point and viscosity of the adhesive provided.

It has now been found that this goal can be achieved

by using an agent from the group that includes salts and oxides of Ca, Mg, Mn, Ni, Co, Cr, Fe +, and likewise silico-aluminateT , activated carbon, cements and silicates, used under normal pH conditions for the glue.

In accordance with this, the present invention comprises a starch adhesive which is insensitive to printing inks, suitable for the production of corrugated board, comprising a starch component and washing water from flexography installations, and this adhesive is characterized by the fact that it contains at least one additive selected from salts and oxides of Ca, Mg, Mn, Ni, Co, Cr, Fe^+, silicoaluminates, activated carbon, cements and silicates, the amount of additive when it is not a silicate is from 0.01 to 10 and preferably 0.05 to 5% by weight in relation to the sum of the amount of starch and additive, and the amount of additive when it is silicate is between 0.01 and 49, preferably between 0.05 and 20% by weight in relation to the sum of the amount of starch and silicate, and optionally an alkali metal hydroxide.

The process for the production of starch glue for corrugated board using washing water from flexography installations comprises adding either to the products to be used for the production of the glue and in particular starch, or to the washing water from the flexography installations, or to the carrier or starch milk to be mixed with the carrier before the wash water is added under the normal pH conditions for the glue to be produced, on the one hand at least one of the agents from the group defined above and, on the other hand,

in possibly an alkali metal hydroxide, where the amount of agent and alkali metal hydroxide is chosen so as to avoid the disadvantages mentioned above.

The invention shall be explained in more detail in the following description and in the examples relating to particular preferred embodiments.

in

The amount of additive varies as a function of the nature of the agents and the content of color in the wash water from the flexographic machines.

In relation to the amount of starch used for the production of the glue, the agent, apart from the silicates, constitutes

in

0.01 to 10% by weight and preferably between 0.05 and 5% by weight.

When it comes to the silicate, they make up 0.01 to 49%, and preferably 0.05 to 20%, and more specifically 0.1 to 6% by weight calculated from the sum of the amount of starch and silicate used.

)

In those cases where it is necessary to use an alkali metal hydroxide at the same time as the additive, the amount of alkali metal hydroxide is selected sufficient to correct the deviation in gelatinization point; it is necessary to correct for the deviation when it occurs because it can change the properties of the glue

is and the speed in the manufacturing machines for corrugated board that use the glue.

It should be pointed out that when it concerns an additive in the form of sodium; potassium or calcium silicates, it is not necessary to add alkali metal hydroxides. Furthermore, the upper limit for the amount of silicates used is not critical and an excess of silicates is not unfavorable.

The additives are added to the components for the production of the glue, in particular to the starch (milk or carrier) or to the washing water which is circulated in the form of a liquid or in the form of solids.

The sodium, potassium and/or calcium silicate can be used in the form of powders or in the form of a liquid.

It can thus be added to the starch or to the "carrier" or to the "secondary material" in one of the two forms. The silicates can also be added to the starch in advance either by pulverization with liquid silicates or by simple mixing in a dry state, when it concerns powders. The powder silicates do not contain free alkali, which can affect the storage of the mixed product.

Silicates with all "moduli" (the ratio silicon/oxide of sodium, potassium and/or calcium can be used. For example, one can benefit from using the most common silicates (with a modulus between 2 and 2.4 for sodium silicates and between 3 and 3.5 for potassium silicates).

The results obtained with the silicate are so good that the washing waters from the printing machines can be used not only in the carrier or starch milk for the production of glue according to the Stein-Hall method, but also in starch glue "without carrier" or "non-carrier" for continuous production and especially with gelatinization of the primary part at high temperature.

A particularly interesting industrial product consists of a mixture of starch for the production of glue for corrugated board with the necessary amount of silicate to allow the use of washing water from printing machines and this amount is between 0.01 and 49, preferably between 0.05 and 20 and preferably between 0.1 and 6% by weight in relation to the sum of the quantity

. starch and silicate.

EXAMPLE 1

An adhesive of the type used is produced

on double surfaces (to be used for the production of

double surface corrugated board). To do this, a starch milk is prepared from 450 liters of water and 50 kg of starch.

This milk is heated to 45°C.

Furthermore, 9 kg of soda is dissolved in 20 liters of water. This solution is added to the starch milk to provide

gelatinization and to prepare the "carrier" or primary part

. after sufficiently intense stirring for 15 minutes. You add 700 liters of water, then 250 kg of starch, then 6 kg of borax which makes up the starch milk or "secondary material".

After 15 minutes of stirring, a Lory viscosity of 19 seconds, a Brookfield viscosity of 290 cP and a gelatinization point of 54°C are obtained.

In another experiment, the secondary water is replaced by a water containing 4% flexographic ink consisting of Chrome Yellow No. 1. The Lory viscosity is no longer measurable and the Brookfield viscosity rises to 29,000 cP; the gelatinization point is 58°C.

The behavior of the glue is thus strongly influenced by using water that contains a flexography ink.

A third experiment uses the flexographic ink from the second experiment and replaces the secondary starch with a dry mixture of 99.4% starch and 0.6% anhydrous calcium sulphate. The "shock" in the second experiment does not occur. The Lory viscosity is 18 seconds, the Brookfield viscosity is 250 cP. In contrast, the gelatinization point is 60°C and soda is then added. Consequently, calcium sulphate and soda will offset the adverse effect of the flexography.

The quantity of soda in the present case is 10.8 kg.

EXAMPLE 2

You proceed in the same way as in example 1

in fact:

- in a first experiment (1): normal preparation - in another experiment (2): the secondary water is replaced by water containing 4% flexo-graph icolour, chrome yellow no. 3 and - a third experiment (3): The starch is replaced of a mixture of 99.5% starch and 0.5% anhydrous calcium sulphate.

The measurement results are reproduced in table II.

The conclusions are identical to those from example 1. It is appropriate to add a further amount of soda (order of magnitude 1.7 kg). Calcium sulfate is permitted under the present circumstances and counteracts the adverse action of chrome yellow No. 3.

EXAMPLE 3

The samples are similar to those from example 1, but in experiment (3) the mixture of 99.4% starch and 0.6% calcium sulphate is replaced by a mixture of 99% starch and 1% calcium oxalate.

In this experiment (3) is the Lory viscosity

20 seconds, Brookfield viscosity 280 cP oq qelatinerinqs point 59.5<Q>C.

The effect of calcium oxalate is thus not equivalent to the effect of calcium sulphate: it is necessary to

add some soda (about 1.6 kg) to correct any effect of the colour.

EXAMPLE 4

The samples are similar to those reproduced in example 1, but in experiment (3) the mixture of 99.4% starch and 0.6% calcium sulphate is replaced by a mixture of 98.25% starch and 1.75% magnesium sulphate. '

In this experiment (3) the Lory viscosity is 22 seconds, the Brookfield viscosity 41o cP oq qelatinerinas point 61°C. The viscosity condition is acceptable,

but it is necessary to add soda to correct the gelatinization point (of the order of 1.39 kg).

EXAMPLE 5

The samples are similar to those given in Example 1, but in experiment (2), chrome yellow No. 1 is replaced by orange (which is commercially available under the designation '"Orange 802") r) and is even more unfavorable to glue than chrome yellow.

In experiment (3) a mixture of 95% starch and

5% ferrous sulfate.

The results are reproduced in table III.

The texture is somewhat short, but the glue is usable.

In contrast, the gelatinization point is greatly elevated. It is necessary to correct with a large amount of soda, which in the practical case makes iron sulphate less interesting for this printing ink.

EXAMPLE 6

The samples are similar to those reproduced in example 5, but in experiment (3) the mixture of starch and iron sulphate is replaced by a mixture of 99% starch and 1% sodium silicate (powder with modulus 2.06). The Lory viscosity is 18 seconds, the Brookfield viscosity is 260 cP and the melting point is nearly normal at 65°C.

One notices that sodium silicate seems to be particularly beneficial in that it simultaneously corrects the viscosity and the gelatinization point.

EXAMPLE 7

The conditions are similar to those given in example 6, but 2% of the same sodium silicate is used instead of 1%.

The Lory viscosity is 16 seconds, if the Brookfield viscosity is 230 cP and the melting point is 55°C.

The values are very close to those obtained in example 6. An excess of sodium silicate therefore has no adverse effect on the adhesive.

EXAMPLE 8

The conditions are similar to those given in example 7, but orange color is not added.

The Lory viscosity is 19 seconds, the Brookfield viscosity is 250 cP and the gel point is 54°C.

The preparation is thus absolutely not affected by sodium silicate. The use of this silicate can therefore generally be added whether or not you use washing water from pressure machines.

EXAMPLE 9

In this example, it is assumed that washing water from flexography machines is used both in the production of the primary part or in the carrier part and in the production of the secondary part of a preparation of the double surface type according to the Stein-Hall method.

Consequently, a carrier or a primary material is prepared starting from a water containing 4% orange-fauve and a mixture of 98% starch and 2% sodium silicate,

and the other conditions correspond to those given in Example 7.

In other words, this "carrier" consists of:

- 450 liters of the washing water,

- 50 kg of the starch-silicate mixture,

9 kg of pure soda and

under the conditions set out in example 1, the secondary material consists of:

- 7 00 liters of the washing water,

- 250 kg of the starch-silicate mixture,

6 kg of borax.

The Lory viscosity of the glue is 19 seconds. The Brookfield viscosity is 460 cP and the gelatinization point is 58 C. The latter thus deviates only slightly. At this limit, you can correct with soda (approx. 1 kg). In practice, this will not be necessary since the conditions are very strict and industrially the wash water will be less unfavorable so that it is not necessary to correct the gelatinization point.

EXAMPLE 10

An adhesive of the "non-supportive" type without "support" is used here.

To produce this glue, a milk of starch and a solution of soda are prepared, where the two preparations are mixed in such a way that the mixture is 39°C and that the proportion of soda in the present case is 3.56% in relation to the commercial starch .

The starch milk is provided from 225 kg of starch and 705 liters of water.

In a first experiment, the product prepared with tap water is subjected to soda ash for a period of time "x" sufficient for the viscosity of

a Brabender viscograph is 300 Brabender units. This is measured at time point "x".

In another experiment, the glue is produced from a milk using starch and water containing 4% flexographic ink of the type "Orange 802". Time "x" is measured.

In a third experiment, the milk used to make the glue is prepared from a powder mixture

97% starch and 3% sodium silicate with modulus 2.06, and

a water containing 4% flexographic ink. Soda is added to this milk. One measures once until time "x".

A fourth experiment is carried out in the same way as in the third experiment, except that the water does not contain flexographic ink.

Time "x" is measured.

The values for "x" are reproduced in Table IV.

Examination of these results shows that the sensitivity to soda in the first or second case is very close to each other. In other words, you get a good viscosity at about the same time.

Sodium silicate makes it possible to correct the very unfavorable effect on printing ink which in the second experiment prevents any swelling.

On the other hand, in the fourth experiment it can be demonstrated that sodium silicate in the absence of printing ink practically does not interfere with the effect of the product.

The measurements are repeated on a preparation that corresponds to that used in industry.

This preparation is provided in the quantities and under the conditions set out below: - 225 kg of starch in 705 liters of water, all kept at 36 C,

8 kg of soda in 215 liters of water, the solution is kept

at 54°C,

- the two aforementioned solutions are mixed so that the temperature is approx. 39°C.

With the help of these base amounts, proceed in the same way as before and record the reaction time "x" as 20 minutes with 3.56% soda; and at this point 4.5 kg of boric acid is added. The Lory and Brookfield viscosities are measured, as well as the gelatinization point of the glue provided.

The results are reproduced in table V.

An examination of the results in table V shows that sodium silicate to a certain extent reduces the swelling in the presence of soda, but the final viscosity is somewhat increased when there is no printing ink (experiment 4).

In the presence of printing ink (Experiment 3), the Brookfield viscosity is favorable. The texture of the glue is somewhat short. The gelatinization point is very high, but the swelling temperature is stabilized which is remarkable.

EXAMPLE 11

You proceed in the same way as in example 1,

i.e. :

- in the first experiment (1): Normal preparation,

- in another experiment (2): The secondary water is replaced with water containing 4% flexographic ink of the type red 8 24 and - a third experiment (3): Starch is replaced with a mixture of 98% starch and 2% Portland cement.

The results and measurements are reproduced in table VI.

The cement seems to be less active, but the printing ink mixtures in the washing water are less unfavorable than the printing inks mentioned above and consequently the use in practice will be sufficient to neutralize the effect of industrial washing water.

EXAMPLE 12

One proceeds as in the samples under example 1, i.e.: - in a first experiment (1): normal preparation, - in another experiment (2): the secondary water is replaced by a water containing 4% flexography colors of the type red 824 and - a third experiment (3): the starch is replaced with a mixture of 99% starch and 1% activated charcoal

The results are reproduced in Table VII

The conclusion is similar to those given for cement. However, the effect is less pronounced in terms of gelatinization point where it may be necessary under normal industrial conditions to correct the gelatinization point by adding a smaller amount of alkali.

Depending on the design you use, you can get an adhesive for corrugated board where you use the wash water from the pressure installations with significant advantages compared to what you have had before.

Claims (3)

1. Starch adhesives which are insensitive to Lrykkfarver, suitable for the production of corrugated board, comprising a starch component and washing water from flexography installations, characterized in that it contains at least one additive selected from salts and oxides of Ca, Mg, Mn, Ni, Co, Cr, Fe^+, silicoaluminates, activated carbon, cements and silicates, the amount of additive when it is not a silicate is from 0.01 to 10 and preferably 0.05 to 5% by weight in relation to the sum of the amount of starch and additive, and the amount of additive when it is silicate is between 0.01 and 49, preferably between 0.05 and 20% by weight in relation to the sum of the amount of starch and silicate, and optionally an alkali metal hydroxide. 2. Glue according to claim 1, characterized in that the additive consists of silicate. 3. Glue according to claim 2, characterized in that the amount of silicate is between 0.1 and 6% by weight in relation to the sum of the amount of starch and silicate.