FI84184B - CALCIUM CARBONATE, SAERSKILT NATURLIG CALCIUM CARBONATE OCH DESS ANVAENDING. - Google Patents

Description

! 84184

FIELD OF THE INVENTION

10 The spread papers are coated with a pulp containing essentially a binder and a pigment in the form of a mineral filler. The components of paper coatings and their use are described, for example, in James P. Casey, Pulp and Paper Chemistry and Technology, Chapter XIX, Part 15 III (1.961).

Essentially, three different methods are known in the printing technique, namely letterpress, offset and gravure.

20 Letterpress printing is the so-called high-pressure method. As with the stamp, the heavy surfaces are elevated in the printing mold. Elevated image surfaces are stained with a roller. This printing method also uses brushed paper containing kaolin or cesium carbonate.

25

Offset printing is the so-called 1aweight printing method, i.e. the heavy and non-heavy parts are in the same plane. They differ in that the heavy parts take in and release fat (i.e., ink) but still repel water, while the non-heavy parts retain water but repel fat (color). The rotating printing cylinder passes first a roller carrying water and then a roller carrying water. However, it does not press directly on the paper, but on the rubber cloth tensioned over the cylinder11 e. Both kaolin and calcium carbonate are used as coating pigments in this process.

In gravure printing, the heavy parts of the cylinder are below the polished surface 40. The cylinder first passes through a bath filled with liquid 2,848,184 and then past Rachel, a steel ruler that removes excess color when the ink to be printed is held in contact until the press on the paper rotates over it 5 and then absorbs the color.

In gravure printing, in practice, only kaolin is used almost exclusively as a chaste pigment. However, calcium carbonate has already been described in the literature (DE-OS 31 32 841 and DE-OS 29 43 653) in connection with intaglio printing-10 families. In reality, however, hardly any calcium carbonate has been used in gravure printing, especially since the professional population has hitherto believed that kaolin has substantially better properties in brushed gravure printing grades.

Moreover, the literature even explicitly advises a person skilled in the art to avoid using calcium carbonate as a coating pigment in gravure papers on the grounds that poor printing results are obtained. The following are two such literature passages as examples: 1. "ECC International", Haus-Zeitschrift, 1981, "How developments in coating pigments affect paper printabi1ity", 25 books Dr. Ken Beazley, Research and Development, pages 1 and 2: It is explicitly mentioned in this publication that one of the "facts of life" was due to the fact that ground calcium carbonate-30 ti is a worse coating pigment for gravure papers than kaolin. Page 2 again refers to the fact that calcium carbonate gives poorer printability.

2. Tappi Coatings Proceedings 1979: "Possibilities and 35 Limitations of High Solids Colors", page 39:

Section 4 "Summary" No. 3 states that the use of powdered calcium carbonate has a poorer print quality than the use of kaolin when the dry matter concentration is 40 or higher.

3 84184

However, the use of kaolin as a pigment for gravure papers has a number of disadvantages, in particular - Poor Theological Behavior; for this reason, it is not possible to brush with a high dry matter content, which causes high energy costs during drying.

- High need for binder.

- Uneconomical because of the high cost.

It is therefore an object of the present invention to obviate these disadvantages and in particular to provide a gravure pigment for gravure papers which can be applied at a high dry matter concentration with a low amount of binder, which saves energy and translucent values as prior art smear pigments.

Surprisingly, it has now been found, after years of extensive testing, that, contrary to the opinion of the person skilled in the art, the above-mentioned object can still be achieved with calcium carbonate, and in particular when it has the characteristics given in claim 1.

The invention is thus characterized by a fully defined combination of three features, according to which 50-70% of the particles are smaller than one μm, less than 10% (especially between 1 and 10%) of the particles are smaller than 0.2 μm and the BET specific surface area is less than 8 m 2 / g. The upper limit of the particle size of the products according to the invention is preferably 3-10.

All alkaline earth carbonates and their mixtures, such as dolomite, can be successfully used within the scope of the invention. The set target is achieved with very well precipitated calcium carbonate.

Particularly good are natural cesium carbonates, limestone, chalk and marble and their mixtures.

Preferred embodiments of the invention are set out in claims 40 to 4. All percentages are by weight. Particle size values given in micrometers denote the corresponding pa 11oha1 user in each case.

The calcium carbonate prepared according to the invention can advantageously be used in a suspension with a dry matter content of 65 to 85% by weight for LWC gravure papers. The following Examples 1-3 illustrate this use by way of example.

Other features and advantages of the invention will be apparent from the following descriptions of embodiments:

Example 1

Preparation of test products:

Natural cesium carbonate was first ground dry in a manner known per se. Fine grinding was performed wet in Sandmy11y. The grinding conditions were then chosen so that the number of particles smaller than 1 μm and smaller than 0.2 μm, as well as the specific surface area, could be varied over a large range.

The grain size distribution was measured by sedimentation analysis and the specific surface area by the BET method.

25

As described above, three products were prepared with different amounts of particles less than 1 μm to demonstrate the effect of this amount on the chalk color of the paper.

30 Those products were examined in gravure paper for gravure printing.

Brush recipe: (Atro = absolutely dry)

Binder (acrylic acid ester 35 copolymer) 4.5 GT (Atro)

Dispersant (polycarboxylic acid

Na salt) 0.6 GT (Atro)

Potassium stearate 0.8 GT

Cationic polyethyleneimine 0.12 GT

40 Anionic acrylate thickener 0.3 GT

Brush pigment 100.0 GT

5 84184

The dry matter content of the paint was adjusted to 65%. Conditions of the paint: 5 Raw paper of the paint: 36-37 g = m2, woody Number of cleansing: OS = 7 g / m2 SS = 8 g / m2

Brush Unit: Combi-Blade-Coater; working speed 1000 m / min.

Drying: Air Foils 250oC

10 Transduction: Supercalender; working speed 200 m / min., line weight 250 Kp / cm and roller temperature 70oC.

OS = top SS = wire side 15 Test conditions:

Gloss: pin method, inlet angle and outlet angle 75o

Guide: according to DIN 53 146 20 Weight printing laboratory:

Printing equipment: an intaglio printing equipment made for experimental use

Printing cylinder: engraved

Printing speed: 5 m / s Color: rotogravure ink (black) 25

Press i1 to

Gloss was measured by the pin method at an inlet and outlet angle of 75 ° over the entire surface of the gravure laboratory apparatus.

30 Puncture and translucency: Use gravure printing 1 laboratory.

Measure the recovery rate of the coated unprinted paper 35 (= R) and the recovery rate of the back side of the printed surface (= Rfr).

λq The formula __ is used in the calculation. 100

R

6 84184

Printing machine in practice:

Printing press: Wifag Rotomaster

Printing cylinder: engraved 5 Cylinder speed / h: 15,000 Color order: yellow, magenta, cyan, black

All papers were printed without static printing aids.

10 The results of the practical weight test were evaluated visually. The order of precedence was used.

Characteristics: VP 50 VP 60 VP 70

Number of particles less than 1 pm 53% 62% 70% 15 Number of particles less than 0.2 pm 7% 9% 12%

Specific surface area 8.0 m 2 / g 9.1 m 2 / g 10.2 m 2 / g

Test results:

Gloss 46% 50% 48% 20 Print gloss 72% 74% 72%

Opacity 90.8% 92.2% 91.4% Breakthrough + translucency 13.1 10.6 11.9 Intaglio print result of a practical printing test (order of values) 2 13 25

The product VP 60, with a particle number of less than 1 μm, was 62%, giving the best results in terms of gloss, weight gain, opacity, breakthrough + translucency and practical test. Next came the products VP 70 and VP 50, where the number of particles less than 30 1 μm was 70% and 53%, respectively. According to the invention, the optimal amount of particles below 1 μm is between 50 and 70%, preferably 60%.

Example 2 35

As described in Example 1, two products were prepared which contained equal amounts of less than 1 μm particles but more and less less than 0.2 μm particles and a correspondingly larger and lower specific surface area to show the total amount of the compound of the invention. 84184 between calcium carbonate and a calcium carbonate which does not achieve the object of the invention.

These products were tested in the 5 gravure colors of gravure paper.

Brush recipe: Acrylic acid ester copolymer 3.5 GT (Atro)

Dispersant (10 Na salt of polycarboxylic acid) 0.6 GT (Atro)

Potassium stearate 0.8 GT

Cationic polyethyleneimine 0.12 GT

Anionic acrylate thickener 0.3 GT

Chastity pigment 100.0 GT

15

The dry matter content of the brush paint was adjusted to 65%. Sively conditions:

Raw paper: 37 g / m 2, wood-containing 20 Amount of sand: OS = 8 g / m 2 = SS 9 g / m 2

Brush Unit: Combi-Blade-Coater; working speed 1000 m / min.

Drying: Air Foils 250oC

Transmission: Supercalender; working speed 200 m / min.

25 line weight 250 Kp / cm and roller

temperature 70oC

Under the experimental conditions described in Example 1, the following 30 Characteristics were obtained: VP 5 VP 14

Particle size less than 1 pm 59% 60%

Number of particles less than 0.2 pm 5% 14%

Specific surface area 8.9 m ^ / g 12.1 m ^ / g 35 Test results:

Gloss 55% 47%

Print gloss 82% 72%

Opacity 91.4% 90.8% Breakthrough + translucency 11.8% 12.6% 40 Gravure printing in 1 laboratory equipment 1 2 (order of precedence) 8 84184

Although the product VP 5 according to the invention achieves the set objectives, the product VP 15 does not obtain satisfactory results, which is otherwise surprising also because VP 5 contains coarser calcium carbonate than VP 14.

5

Example 3

As described in Example 1, a product was prepared having values of less than 10 for particles, less than 0.2 for particles and a specific surface area according to the preferred embodiment.

This product was tested in an intaglio paper coating color compared to the kaolin otherwise used in practice, i.e. the prior art product.

Brush color recipe: VP 60/6 K a o 1 hm

Binder (acrylic acid ester-containing copolymer) 3.5 GT (Atro) 4.5 GT (Atro) 20

Dispersant 0.6 GT (Atro) 0.3 GT (Atro)

Calcium stearate 0.8 GT 0.8 GT

25 Cationic polyethylene

imine 0.12 GT 0.12 GT

Anionic acrylate

thickener 0.3 GT 0.3 GT

30

Chastity pigment 100.0 GT 100.0 GT

The dry matter content of the paint was adjusted from 65% to 56% 35

Sivelvoiosuhteet:

Sively raw material: 36 g / m 2, woody

Amount of smear: OS = 8 g / m ^ SS = 9 g / m ^

Brush Unit: Combi-Blade-Coater; working speed 40 1000 m / min.

Drying: Air Foils 250oC

Calendering: Supercalender; working speed 200 m / min.

line weight 250 Kp / cm, roller temperature 70oC.

9 84184

Under the experimental conditions described in Example 1, the following are obtained

Characteristics: VP 60/6 Brushed kaolin / light weight 5 Particle content less than 1 μι 60% 49%

Number of particles less than 0.2 pm 6% 17%

Specific surface area 7.8 m 2 / g 13.0 m 2 / g

Test results: 10 Gloss 63% 64%

Print gloss 85% 85%

Opacity 92.6% 90.0% Breakthrough + translucency 10.7 13.5

Gravure printing in a laboratory (order of precedence) 1 2 Practical gravure test (order of precedence) 1 1 With the calcium-20 carbonate VP 60/6 according to the invention used in this example, which has 60% less than 1 μm particles and 6% less than 0.2 μm particles and with a specific surface area of 7.8 m 2 / g, the same gloss and gloss values are obtained when comparing 1-choline 11a. VP 60/6 gives better results than comparator 1-choline 11a in terms of opacity for both penetration and translucency and in laboratory weight .

In practical printing tests, both products are evaluated as equally good.

These results show that the calcium carbonate 1a corresponding to VP 60/6 can of course be used to produce a gravure ink for gravure paper, resulting in a coated paper which is as good and in part better than gravure papers normally made using kaolin.

35

It is clear from the brush color recipes of Example 3 that equally good and partially better properties can be obtained by using about 20% less binder in the case of calcium carbonate. Reducing the amount of binder marks-40 see the paper manufacturer with significant cost savings.

10 841 84

Good Theological Behavior of Calcium Carbonate High Solids Coating, which is not possible with kaolin, allows the production of High Solids Coating. In this way, drying the brush product saves energy, which is also a significant cost saving for the paper manufacturer.

Claims (5)

11 84184 Calcium carbonate, in particular natural calcium carbonate, prepared by grinding and / or grading according to particle size, characterized in that a) 50-70% of the particles are smaller than 1, b) less than 10% of the particles are smaller than 0, 2, and c) the BET specific surface area is less than 8 m 2 / g. 10 Calcium carbonate according to Claim 1, characterized in that 55 to 65% of the particles are smaller than 1 μm. Calcium carbonate according to Claim 1 or 2, characterized in that 60% of the particles are smaller than 1 μm. Calcium carbonate according to Claim 3, characterized in that 4 to 6% by weight of the particles are smaller than 0.2 μm. Use of calcium carbonate according to one of Claims 1 to 4, with a dry matter content of 65 to 85% by weight, in a suspension for high-density LWC (High Solid Coatings) papers. 12 841 84 Pat entkrav