DE1696188A1 - Composition for covering paper - Google Patents

Description

Composition for overlaying paper

The invention relates to coating paper with a coating, and more particularly relates to a paper coating composition for making one coated Paper that has a matt surface.

A wide variety of types of coated papers are already being produced. Usually this will be Paper coated with a composition, which in some cases is also referred to as "coating color", and which essentially contains an adhesive or a binder and a pigment. A description of the components of paper cover ■ compositions and the method of applying such compositions on paper is found in Volume III, Chapter XIX of the second edition of the book by James P. Casey entitled "Pulp and Paper: Chemistry and Teohnology". The adhesive used can be, for example, starch or casein or a trading synthetic rubber latex; which adhesive is used in each case depends on fc.B. according to the printing process to be used? for example, must be used in the offset lithography process the adhesive will be insoluble in water. Generally acts

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. the pigment do clay as the main component aowieskiet-? υ ner amounts of e.g. less than 20 percent by weight of one or " several other components, e.g. from calcium carbonate, lithopone, barium sulfate, titanium pigments, talc or "satin white". The clays normally used to make coatings contain at least 70 percent by weight of particles with an equivalent spherical diameter of less than 0.002 mm, and although up to about 15 weight percent calcium carbenate - normally in the form of precipitated calcium carbonate - can be used to reduce the cost of the coating composition

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to reduce and to increase the absorption capacity for printing ink, the gloss is seldom after a light satin finish, e.g. after five passes at a pressure of about 45 kg / cm less than 30 gloss units according to Tappi. The coating composition is usually made by making the pigment and dispersing the adhesive separately in water and then mixing the two components. Then the coating composition is applied spread over the surface of the paper, dried and a subsequent treatment e.g. by calendering or satin finishing or finishing etc. subjected. The main properties of paper that can be achieved by applying a coating or painting are influenced are its smoothness, its capacity for printing ink and its glanas. For example, if a magazine has numerous Contains ads will usually have a strong shine as considered very desirable because it is a good one with halftone images Provides contrast and a pleasing appearance. In other cases, however, such as when the printed material is essentially is about writing, e.g. in school books, there is a A need for coated paper that is easy to print on, but has a matt surface »to reduce eye fatigue

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Decrease reading. In this connection it should be noted that the term "matte finish" means a coating that has a gloss of no more than 15 units according to Tapp!

It has now been found that there is a paper coating composition can produce with good printing properties and a matt surface by using a mixture as pigment, that has a coarse-grained tone and a whiting made of natural Contains chalk in certain proportions. More specifically, the invention provides a paper coating composition, which is a dispersion of a pigment in an aqueous medium which contains an adhesive, the pigment firstly containing a clay in which at least 50 percent by weight of the Particles have an equivalent spherical diameter of at most 0.002 mm, and secondly, a slurry of natural Chalk, this component making up at least 25 percent by weight of the pigment.

The phrase "natural chalk slurry" here refers to the material that is obtained by grinding a naturally occurring chalk, which is composed of the residues of coccoliths. Such a bloat made of natural chalk consists of calite crystals-irTJOrm of Particles that are essentially equivalent spherical diameter in the range of 0.001 to 0.005 mm and loose with each other such a suspension is of the precipitated Calcium carbonate as well as other sources of calcium carbonate such as ground limestone, marble or oyster shells. The calite crystals of natural chalk predominate a rounded shape so that in one use the chalk in a paper cover composite is a bigger one

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Part of the light falling on the coated paper is diffuse is reflected than when the Pigmeniyaie is more angled Calcium carbonate particles, which can be found e.g. when grinding of limestone ratfc, and which receives a greater proportion of the reflect incident light in a regular manner. Thus, the use of natural chalk according to the invention leads to a duller surface than when using the same amount of calcium carbonate. ■

For the invention it is essential that the The clay used in the coating composition is a coarse-grained kaolin, which consists of at least 50% by weight of particles having an equivalent spherical diameter of not less than 0.002 mm have. The clay or kaolin preferably contains 20 to 50 percent by weight of particles with an equivalent spherical diameter of less than 0.002 mm, 10 to 25 weight percent of particles with an equivalent spherical diameter of greater than 0.010 mm and no more than 0.03 weight percent of particles larger than the hole size of a No. 300 screen corresponds to the English standard.

The pigment expediently contains 50 to 75 percent by weight of natural chalk as a whitening agent, and the natural chalk becomes preferably ground so that they are 30 to 80 percent by weight Contains particles that have an equivalent spherical diameter of less than 0.002 mm.

In the case of the adhesive used in the coating composition according to the invention is used, it can be an adhesive of known type, e.g. starch, gelatin, casein or a synthetic rubber latex. Also know the coating composition Contains additive * of known type. The proportional amounts of the

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The adhesive and the pigment and the ratio of the refractive indices of the adhesive and the pigment affect the optical Properties of the coated paper, however, can determine the optimal amounts of glue and pigment to use are, if according to the invention a matt surface is to be achieved, easily by simple experiments and by hand of the following examples which illustrate the invention.

Examples 1 to 5

Sheets of paper were coated with various coating compositions according to the following Table I, wherein a high speed trailing doctor blade coater was used as in US Pat British Patent 1,032,536; this device operated at a paper speed of about 460 m / min and produced a coating weighing 13 »0 g / m. For each composition, 17 Parts by weight of starch based on the weight of the pigment used. After the coating was made, various properties of the coated paper were measured The results obtained are summarized in the following table I « .

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1 Tabel I. 3 . 4th 5 Example Mr. Coarser
Clay (1) > 2 50? Δ roughly.
Tone} $ 50
natural
chalk $ 25 roughly.
Volume; $ 75 =
natural
chalk Natural
chalk Pigment 58 759 & gross.
Volume; $ 25
natural
Chalk (2) 62 64 65 Total festival
s toffge
stop, fc (3) 19th 60 15th 12th 10 TAPPI
Shine
units 26th 17th 28 29 30th K & U Far-
record
able fo 33 27 83 107 137 IGT
Recording-
speed
m / min 43.0 68 50.7 76.0 79.7 micro-
contour-
Color check 45.2

(T) The coarse clay was 45% by weight of parts with an equivalent ball diameter of less than 2 Microns and 15 percent by weight of particles with a More than 10 microns in diameter.

(2.) The natural chalk contained 37 percent by weight of particles with an equivalent sphere diameter of less than 2 microns.

(3) Percent total solids =

Total weight of solids - * - * - r x. 10096

Total weight of solids + water weight ^

It can be seen that with an increase in the percentage natural chalk in the composition, the viscosity of the coating composition decreased, and that it therefore increased with a higher Solid content could be applied. It can also be seen that with an increase in the percentage of natural Chalk the glana of the paper »measured after a light Satin finishing with five passes in one. Druok of around 45 kg / cm at room temperature progressively decreased. Also took

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the capacity for printing ink progressively increases; even the bond strength, measured as the I.Gr.! - uptake speed, increased? this means that you can get by with a smaller amount of adhesive if a certain bond strength is to be achieved. The micro-contour printing ink test provides a measure of the smoothness of the paper; The higher the numbers in Table I are, the less smooth and the The paper is rougher, when it comes to the microcontour printing ink test is an excess of non-absorbent printing ink on the surface of the paper with the help of a rod-shaped work, applied stuff so that the surface is completely covered. The paper provided with the printing ink is then with wiped off with a soft cloth or cotton wool, leaving the printing ink in any surface indentations or Irregularities are left behind. By measuring the brightness of the colored sheet compared to a non-colored sheet, it is possible to obtain a numerical value for the roughness of the Of paper. Represent the results of the test the difference in brightness between the non-colored sheet, to which the value 100.0 is assigned, and the colored sheet Arc. ■

Examples 6 to 10 .. '■' · ■■

Sheets of paper would have different coating compositions Coated according to the following Table II, using the same high speed device with lagging Blade was used; the running speed of the paper was again about 460 m / min .. With each composition were used as an adhesive 10 parts by weight of starch 'fviecoeol · 310) and? Parts by weight des styrene-butadiene-lateÄ Nr ^ 636 (manufacturer Dow Chemical Co.

Ltd.) is used based on pigment weight. After this

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Applying a coating with a weight of 13.0 g / m .: v ^ urden various properties of the treated paper measured; the results of these tests are given in Table II below compiled.

Table II

Example Kr. Y ^6th t 7 t 8 I- 9 r ¹⁰ pigment Coarser
volume $ 75 roughly.
Sound ;, 257 "
natural
Circle de $ 50 roughly.
Volume; 50? Δ
ηatari.
chalk 25f " roughly.
Volume; 75 #
natural
chalk Natural
chalk Total festival
fabric
stop, $> 55 58 60 63 64 TAPPI
Glossy
units 25th 21st 14th 11 6th K & Ν color
recording-
able $> 19.1 21.4 23.8 26.0 28.4 I.GMD.
Recording-
speed
m / min 103 118 130 142 154 micro-
contour-
¥ check 49.5 55.6 61.8 , 67.7 73.2

With the coarse clay and the natural chalk it was are the same substances as those in Examples 1 to 5 used.

It can be seen that the results of the tests according to Table II show the same tendency as in Examples 1 to 5, but that the replacement of part of the starch adhesive by a styrene-butadiene latex affects the gloss values, the IGT uptake rates and the values of the microcontour color test increased while the K&N color receptivity compared

going back to the arches made using only starch as an adhesive became. 109847/140 1

Examples 11-15

Sheets of paper were made with different coating compositions coated according to the following Table III, the same high-speed trailing blade device was used j the speed of the paper and the weight of the coatings again corresponded to the information with respect to Examples 1 to 10.

Each composition was used as an adhesive 17 parts by weight Starch used based on pigment weight. After applying the coatings, various properties were found of the paper measured, the following Table III compiled results were achieved.

In these examples, the coarse tone had one Particle size distribution that 33 weight percent particles are present which had an equivalent spherical diameter of less than 0.002 mm and 15 weight percent particles with an equivalent ball diameter of more than 0.010 mm. The chalk contained 37 weight percent particles with an equivalent Ball diameter of less than 0.002 now.

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-ΙΟ-Table III

Ib9b188

Example no. \ ¹¹ \ ^12th l 13 14th |. 15th pigment Coarser
volume $ 75 roughly.
Volume; $ 25
natural
chalk 50 # coarse.
¹ Oa; 50 ^
natural
chalk 25? Δ roughly.
Volume; 75 #
natural
chalk NatUrl.
chalk Grave festival
fabric
stop, % 55 57 60 63 65 TAPPI
Shine
units 16 13th 11 10 10 K&E color
recording-
able . i> 27 29 30th 30th 30th IGT
Recording-
speed
m / min 40 68 92 117 137 micro-
contour ~
Color test 54.8 59.1 65.0 77.3 79.7

It can be seen that the effect of using a coarser Clay in connection with chalk consists in increasing the viscosity of the coating composition, so that it is necessary reduce the concentration of solids in order to ensure that that the composition is sufficiently fluid that it can be used for painting paper. In comparison to those obtained using a less coarse tone The results show an increase in the K&N color receptivity, the I. G.Tv recording speed and the with the help the roughness measured during the microcontour test while the gloss of the paper is reduced.

Claims i

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Claims (3)

Λ- - ¹¹ "1696488 PATENT RANKS 1 . Paper coating composition that is a dispersion of a Pigments: in an aqueous containing an adhesive Medium, characterized in that the pigment comprises firstly one. Comprises clay in which at least 50 percent by weight of the Particles have an equivalent spherical diameter of not less as 0.002 iBm, and secondly as a whiting one natural chalk that is at least 25 percent by weight of the Pigments. 2. paper liberation composition according to claim 1, characterized in that that the natural chalk to 30 to .80 percent by weight consists of particles that have an equivalent spherical diameter less than 0.002 mm. 3. Paper coating composition according to claim 1 or 2, characterized characterized in that the natural chalk is 50 to 75 percent by weight of the pigment. 4 * paper coating composition according to claim 1 or 2, characterized characterized in that the clay contains 20 to 50 percent by weight of particles having an equivalent spherical diameter of less than 0.002 mm, furthermore 10 to 25 percent by weight of particles with an equivalent spherical diameter of more than 0.010 mm and no more than 0.03 weight percent particles that are larger are than the hole size of a sieve No. 300 according to English Standard corresponds 109847/1401 The patent attorney