EP0409836A1

EP0409836A1 - Method for fabricating paper for bottle labels

Info

Publication number: EP0409836A1
Application number: EP89901257A
Authority: EP
Inventors: Daniel Defrenne
Original assignee: INTERMILLS INTERNATIONAL SA; Intermills Industrie Pont-de-Warche SA
Current assignee: INTERMILLS INTERNATIONAL S.A.
Priority date: 1989-01-18
Filing date: 1989-01-18
Publication date: 1991-01-30
Also published as: US5209982A; WO1990008223A1

Abstract

Un papier couché pour étiquettes spécialement adapté aux condition d'utilisation dans les brasseries est fabriqué en appliquant sur la face verso du support fibreux une sauce hydrophile ayant une réaction rapide à l'eau de manière à accélérer l'absorption d'eau. Le contrôle rigoureux du taux d'humidité du papier au cours du processus de fabrication assure une stabilité dimensionnelle remarquable et un maintien de planéité excellent sur une plage d'humidité relative étendue.A coated label paper specially adapted to the conditions of use in breweries is produced by applying a hydrophilic sauce with a rapid reaction to water on the reverse side of the fibrous support so as to accelerate the absorption of water. Rigorous control of the moisture content of the paper during the manufacturing process ensures remarkable dimensional stability and excellent flatness maintenance over a wide range of relative humidity.

Description

Method for manufacturing label paper for bottles

Description

Prior art

The present invention relates to the manufacture of coated paper and relates in particular to improvements aimed at improving the properties of coated paper intended for making labels for bottles.

The labels for bottles used to contain drinks must meet a number of criteria which can be briefly summarized as follows:

1. The label supports must ensure perfect labeling, that is to say have perfect adhesion to the bottles. Suitability for labeling is defined by the loss of stiffness of the paper in the wet state, which is linked to the speed of absorption of water.

2. The label supports must be dimensionally stable over a wide range of relative humidity levels so as to remain perfectly flat during the manipulations to which they are subjected.

3. Printed inks and surface varnishes must develop maximum gloss: the penetration of inks and varnishes in the support must be as low as possible. 4. Labels must resist flaking.

In addition, for the protection of the natural environment, the label support must be made as least polluting as possible and, for this purpose, the labels must have a high resistance to chemical agents (caustic soda) so as not to not pollute the washing baths and they must contain the lowest possible free formaldehyde content because free formaldehyde inconveniences people handling the labels and it deposits traces on the bottles which destroy the yeasts of the drinks.

The label paper is made up of a fibrous support, the front side of which carries a layer of material provided for printing and the back side of which is covered with a sauce intended to ensure the qualities of labeling. According to the prior art, the qualities of labeling are obtained by using, to cover the back side, a sauce relatively waterproof. The amount of water absorbed by the paper is then usually of the order of 12 to 15 grams per square meter.

The performance of the label papers produced according to the prior art can be summarized as follows:

Suitability for labeling

Loss of stiffness in the wet state 45 to 50%

Flatness area

Maintaining the flatness of 45 to 80% relative humidity. Attaching inks and varnishes

Material loss after soaking in caustic soda solution 12 to 15 g / m ²

Level of formaldehyde released during handling 35 to 60 mg / m ²

It turns out that the characteristics of the papers currently on the market for making labels are hardly entirely adapted to the severe conditions of use in the brewing and limona¬ diere industry.

Statement of the invention

The subject of the invention is a technique for manufacturing coated paper which remarkably improves the labeling performance and qualities of coated paper for labels.

The subject of the invention is also a technique for manufacturing coated paper which very substantially reduces the pollution of washing baths, while moving in the direction of the evolution of European standards in the matter.

Finally, the invention relates to a new generation of coated label paper which meets the requirements of breweries.

More particularly, the invention relates to improvements in the manufacture of coated paper, which develop essentially along three axes: 1) the composition of the sauce applied to the back side of the paper so as to improve the labeling ability,

2) the composition of the layer applied to the front side of the paper so as to improve the adhesion of the inks and reduce the pollution of the washing baths;

3) the papermaking process to give labels the desired dimensional stability.

The features of the technique according to the invention are defined in the claims.

Description of the drawings

FIG. 1 is a simplified general diagram of an exemplary paper manufacturing installation using the method according to the invention.

FIG. 2 is a diagram showing a typical water absorption curve for a paper produced according to the invention and, by way of comparison, a typical water absorption curve for paper according to the invention. prior art. Description of an exemplary embodiment

The fibrous pulps intended to serve as a support for the paper are mixed in a mixing tank to which are also added the usual fillers (kaolin, talc, titanium) and the bonding agents and any wet strength agents. The fibrous composition is for example:

Support - long bleached fibers 55.00% - short bleached fibers 37.00%

0.90% titanium di-oxide

Talc 0.90%

Kaolin 0.90%

Optical brightener 0.02% Adhesive agents sufficient quantity

Example of acid bonding:

Sodium aluminate 0.09%

Alumina sulfate 2.50%

0.25% urea formalin 0.25% melamine formalin

Additives can also be added to the mixture continuously, respecting the minimum contact times recommended upstream of the machine headbox.

After refining the mixture in order to promote the bonding of the fibers, the dough is poured into the headbox 1. Referring to FIG. 1, the headbox is shown in 1. The dough then passes over a table of draining 2 to remove the water and under pressure rollers 3, then the support F passes through a first dryer 4. The support then contains 0.5 to 8% water. The dryer is a known device which can be produced in various embodiments.

At the outlet of the dryer 4, the support passes under a friction cylinder 5 which finishes preparing the support for coating the front and back sides. The support then passes into a coating station 6 in which the coating of the back and front sides is carried out using sauces. The coating device can be any known device (blade device, rotary doctor blade and / or roller for example). The coating station is advantageously arranged to simultaneously coat the back and front sides. The coating may possibly be carried out successively on each of the faces with an intermediate drying.

The composition is selected sauces soigneuse¬ ment according ^τ invention to optimize these performan¬ paper. According to a first aspect of the invention, the composition of the sauce applied to the back side is selected to improve the labeling ability. This improvement is obtained by accelerating the reaction of the sauce with water so as to produce rapid water absorption. The quality of a labeling is indeed linked to the loss of rigidity of the support in the wet state which represents the speed of absorption of water by the back sauce. While the back sauce according to the prior art is commonly made less absorbent in water, the composition of the back sauce according to the invention is produced in such a way that the sauce is hydrophilic. This result is obtained by choosing, for the binder which normally enters into the composition of the back sauce, a mixture of starch and latex containing a very active wetting agent, for example a latex type DL 636 from the Dow Chemical brand. An exemplary composition for the back sauce according to the invention is given below:

Kaolin English 80.0%

Starch 9.5%

Dow Chemical Latex type DL 636 - 9.5% Urea-formalin 0.5% Melamine-formalin 0.5%

The diagram in FIG. 2 shows the speed of water absorption speed of a paper according to the invention (curve A) compared to a speed curve of water absorption typical of a paper according to prior art (curve B). The abscissa axis carries the scale ^'of the time and the ordinate is shown the rate of water penetration to the back of the paper facing the front side. Curve A shows that the absorption of water by the paper produced according to the invention is greatly accelerated. This rapid, almost immediate reaction to water not only ensures excellent adhesion of the label to a bottle but also prevents the edges of the label affixed to the bottle from coming off.

A second aspect of the invention relates to the composition of the front layer which is selected to increase the adhesion of inks and varnishes compared to the prior art while reducing the pollution of washing baths during recycling of bottles with labels. To get this result, the invention chooses for the binder a combination of crosslinkable latex and soft latex with the addition of an insolubilizing agent which fixes all the free bonds of the crosslinkable latex. For the pigmentation charge, a mixture of kaolin and calcium carbonate with very fine particles is chosen. ^* An exemplary composition for the front layer is given below t

Kaolin 57% Calcium carbonate 24%

Rohm & Haas hard latex type E581 7%

Dow Chemical soft latex type DL 570 10%

Insolubilizing agent 2%

The particle size of the calcium carbonate has a distribution of 98% of particles smaller than 2 microns and 80% of particles smaller than 1 micron.

After the coating operation on the back and front sides, the paper passes through a second dryer 7 in order to dry the coated back and front sides, then between straightening cylinders 8, before being conveyed to a rewetting oste 9 consisting of a spray bar. The rewetted paper then passes into another dryer 10. At the exit from the latter, the paper again passes under a last rewetting ramp 11 before being wound on a winder 12.

In accordance with another aspect of the invention, the paper is subjected to successive controlled drying-rewetting cycles which have the effect of providing the paper with remarkable dimensional stability regardless of the humidity and thus guaranteeing the labels. an exceptional dish. To carry out the drying-rewetting cycles, the invention provides a rigorous control of the humidity of the paper as soon as the felt is ready for coating. Referring to Figure 1, have been shown three devices denoted 13 Î the first upstream of the coating station 6, the second downstream of the dryer 7 and the third downstream of the dryer 10. These devices are humidity measurement which can be of any known type, for example an Accuray brand humidity measurement device. These measurement devices are mounted so as to scan the surface of the paper and produce a measurement signal showing the humidity level. The measurement signals of the three devices 13 in FIG. 1 are denoted H1, H2 and H3. The number of measuring devices 13 is obviously not limited to three.

The measurement signals are received in a control station where each measurement signal is compared with a predetermined setpoint signal: the signal Hl is compared with the setpoint signal Cl, the signal H2 with the setpoint signal C2 and the signal H3 to the setpoint signal C3. The setpoint signals are generated and stored in a control processor 15. The con¬ signs are chosen according to the characteristics of the paper to be produced. The setpoint and measurement signals are compared in a comparison device 14 organized to respectively produce a control signal S1, S2, S3 representing the difference between each measurement signal and the corresponding setpoint signal. The control signal Si is used to adjust the heating power of the dryer 4 in order to reduce to zero the difference between the measured humidity represented by the signal H1 and the corresponding setpoint represented by the signal Cl. The signal S2 serves to adjust the heating power of the dryer 7 in order to reduce zero the difference between the measured humidity represented by the signal H2 and the corresponding setpoint represented by the signal C2. The signal S3 is used to adjust the heating power of the dryer 10 in order to reduce to zero the difference between the measured humidity represented by the signal H3 and the corresponding setpoint represented by the signal C3. In an exemplary implementation for manufacturing coated label paper having 50% relative humidity, the absolute humidity is adjusted by the instructions C1, C2 and C3 to a value of 5.5%.

The method according to the invention thus makes it possible to obtain coated paper for labels having performances significantly improved compared to those of paper for labels produced according to the prior art. The performances obtained according to the invention can be summarized as follows:

1. Suitability for labeling

Loss of stiffness in the wet state ^ 70%

2. Flatness area

Maintaining the flatness of 15 to 90% relative humidity

3. Attachment of inks and varnishes Loss of material after soaking in a caustic soda solution ^ 1 g / m ²

4. Level of formaldehyde released during handling - 20 mg / m ²

These performances, compared to those of known label papers, illustrate the remarkable progress provided by the invention in the field of art. The performances obtained thanks to the manufacturing technique according to the invention are perfectly suited to all the conditions of use in breweries and to the requirements of printers and metallizers. The invention provides these remarkable performance with a back face covered with a sauce which the weight can advantageously be reduced to 1, ^* 5 g / m ² and even up to 0.5 g and with a front layer whose weight can be much less than 15 g / m ² . It should also be noted that the sharp reduction in pollution from washing baths is in line with European standards and that the reduction in the level of formaldehyde released during handling improves working conditions and reduces the risk of contamination. drinks.

The embodiment of the invention described in the foregoing is an example given by way of illustration and the invention is in no way limited to this example. Any modification, any variant and any equivalent arrangement must be considered to be within the scope of the invention.

Claims

1. A method of manufacturing coated paper for éti¬ quettes, characterized in that on the reverse side of the fibrous medium is applied a hydrophilic sauce having a fast reaction with water so as to speed up the water uptake ^c .

2. Method according to claim 1, characterized in that the sauce applied to the back side of the fibrous support contains a latex containing an active wetting agent.

3. Method according to claim 1 or 2, characterized in that the composition of the hydrophilic sauce is selected so as to have a high water absorption speed for a predetermined period of time.

4. Method according to claim 1, 2 or 3, characterized in that on the front face of the fibrous support is applied a layer whose composition contains as binder a mixture of crosslinkable latex and latex m "or.

5. Method according to * claim 4, characterized in that to the mixture of crosslinkable latex and soft latex is added an insolubilizing agent fixing all the free bonds of the crosslinkable latex.

6. Method according to claim 3, 4 or 5, characterized in that the layer applied to the front face of the fibrous support also contains a mixture of kaolin and calcium carbonate or of an equivalent compound, with very large particles. fine.

7. Method according to claim 6, characterized in that the calcium carbonate or the equivalent compound is added with a particle size distribution of which is about 98% of particles less than about 2 microns and about 80% of particles infer ¬ less than 1 micron.

8. A method of manufacturing coated paper for labels, characterized in that a layer of material is applied to the front face of the fibrous support, the composition of which contains a mixture of reti¬ culable latex and soft latex.

9. Method according to claim 8, characterized in that to the mixture of crosslinkable latex and soft latex is added an insolubilizing agent fixing all the free bonds of the crosslinkable latex.

10. The method of claim 8 or 9, characterized in that the layer of material applied to the front face of the fibrous support further contains a mixture of kaolin and calcium carbonate or an equivalent compound, with very fine particles.

11. The method of claim 10, characterized in that the calcium carbonate or the slow equiva¬ compound is added with a particle size whose distribution is about 98% of particles less than about 2 microns and about 80 % of particles smaller than 1 micron.

12. Method according to any one of the preceding claims, characterized in that after the application of the layers of material on the back and front sides of the fibrous support, the sheet of paper is subjected to minus a drying-rewetting cycle controlled so as to adjust the humidity of the paper to a predetermined set value, adjusted according to the characteristics of the paper.

13. Method according to claim 12, characterized in that each controlled drying-rewetting cycle consists in measuring the moisture content of the paper after a drying step and producing a measurement signal (Hl, H2, H3) representing the rate humidity, and to compare the measurement signal (Hl, H2, H3) to a predetermined memorized setpoint (Cl, C2, C3) so as to produce a proportional control signal (SI, S2, S3) away from the measurement signal and the corresponding setpoint, said control signal being used to adjust the heating power used in the above-mentioned drying step.

14. A method of manufacturing coated paper for labels, characterized in that after the application of the layers of material on the back and front sides of the fibrous support, the sheet of paper is subjected to at least one drying cycle. rewetting controlled so as to adjust the humidity of the paper to a predetermined set value, adjusted according to the characteristics of the paper.

15. The method of claim 14, characterized in that each controlled drying-rewetting cycle consists in measuring the moisture content of the paper after a drying step and producing a measurement signal (Hl, H2, H3) representing the rate humidity, and compare the measurement signal (Hl, H2, H3) to a predetermined memorized setting (C1, C2, C3) so as to produce a control signal (SI, S2, S3) propor- tional to the difference between the measurement signal and the corresponding setpoint, said control signal being used to adjust the heating power used in the above-mentioned drying step.

16. Coated paper for labels intended to be used on bottles, manufactured according to the process as described in the preceding claims.