SE524281C2 - Surface treatment composition, including starch particles, method of making paper or paperboard, paper or board and use of a surface treatment composition - Google Patents

Abstract

Surface treating composition for paper or paperboard, in the form of an aqueous composition. According to the invention, the composition comprises, at room temperature and counted on the solid content of the composition, starch particles in an amount of more than 65 %, the starch for the starch particles being constituted by cross-linked starch and at least 10 % of the starch content of the composition being constituted by starch particles in teh entire temperature range 20 - 50 DEG C. The invention also relates to a method in the manufacturing of paper and paperboard with use of this composition and to paper or paperboard that comprises a composition according to the invention. Finally, the invention relates to the use of a surface treating composition.

Description

20 25 30 35 524 281 2 P1647 | n; . f: o - s: In v: the batter also contains a binder which may consist of dissolved starch and / or a synthetic binder. Examples of commonly used synthetic binders are styrene-butadiene latex and acrylate latex.

The application of starch solution or coating batter can be done in different ways. A common method is to apply the starch solution or coating batter to two pieces of rollers which form a nip in which the paper web passes by means of grooved rods. The one on the rollers of the fourth starch or batter is then transferred to the paper web in the nip.

Another way is to transfer the starch or batter from a roller or in direct contact with a fountain to the paper web to even out the elm formed on the paper web with a blade in the next step. In this surface application method, which is called sheet coating, one side of the paper is usually treated first, after which this side is dried before the next side is treated in the same way.

Another surface treatment method has recently been developed. This method is described in a number of patent applications, e.g. WO 97/13035 and WO 97/13036 and in short means that the starch solution or coating is applied to the running paper web by spraying. This contactless application offers many advantages and the technology is expected to be used to an increasing extent in the future.

Just before the finished paper is rolled up at the end of the paper machine, the paper web passes one or fl your roller nips in the so-called machine ease in order to reduce the surface roughness. The surface roughness is measured in the unit "ml / min Bendtsen" and the lower this value, the greater the surface smoothness of the paper. The surface roughness decreases with increased line pressure, which is positive for e.g. the printing properties of the paper. However, the bulk also decreases with increased line pressure, which, however, is not desirable.

Another important property of the paper or board is its opacity, which is a measure of the opacity of the paper. Due to an increased opacity, the basis weight of the paper (weight expressed in grams for 1 m2 of paper) can be reduced with large financial savings as a result. Increased opacity for a copy paper or an offset printing paper also allows both sides of the paper to be better used for printing or copying without the pressure on one side being disturbed by the pressure on the opposite side. For a paper intended for e.g. envelopes, the importance of good opacity is great. 10 15 20 25 30 35 Pl647 524 281 ß. =. . 1 ~: ~ a nu Another optical property of weight is the whiteness of the paper or board. A high whiteness is achieved by choosing raw materials with high brightness and with the help of optical brightener.

Efficient utilization of optical brightener requires that this be combined with the surface treatment composition. The term "carrier" has been introduced here, meaning that one of the components of the surface treatment composition must be a good carrier of optical brightener in order for the whiteness to be developed effectively.

Another important property is the thickness of the paper. On the one hand, the thickness has a value in itself, e.g. gives a thicker printed matter a more lavish impression, and the stiffness of the paper increases with the thickness (the stiffness is a function of the E-module times the thickness in cubic meters). An increased thickness (reduced density) of the paper can also be used to reduce the basis weight.

Paper makers often use the term “bulk” which is the inverted value of density. Thus, as high a bulk as possible is sought. The light transmittance of the paper is also an important property. A relatively low value is sought here, i.e. a high lu fi resistance, in order to e.g. avoid double feeding in suction-fed printing presses and through-pressure when flexpressing. A high lu. Resistance is also necessary when using machines for automatic loading in envelopes. Too low lu. Resistance also causes double feeding and problems when opening. envelopes fl ik.

In addition to paper, paper and cardboard also contain calcium carbonate or clay. The content of these inorganic materials, called "fillers", is usually between 15 and 25%.

The most common filler in the production of printing and copying paper is now PCC, which is an abbreviation of the English word Precipitated Calcium Carbonate. Although PCC gives a relatively high bulk, this filler lowers the lu ansen resistance to in many cases unacceptable levels.

Another important property of the paper, which is affected by the surface treatment, is its printability properties. In addition to the already mentioned properties, such as higher and smoother ink absorption and a better image reproduction, which has hitherto applied to, above all, oily printing, more and more work has been done to achieve better printability properties when using so-called ink jet (ink jet) printer. A paper which has good printability properties for ink jet printers is mainly characterized by the following: 10 15 20 25 30 35 P1647 524 281 4 o o r u: o .å _ ¿_ - f - | of o Minimal or insignificant ink output outside the printed object so that the object does not get uneven and scattered edges. Objects, e.g. letters if it is text that is printed, are perceived as unclear and blurred if this property is not fulfilled.

The ink output is measured by visual methods or by means of an image analysis instrument. ø High optical density. The property is usually measured with an optical densitometer. 0 Minimal throughput. This is not achieved if excessive penetration of the ink pigment or dyes into the paper results in the color appearing on the back of the paper. A high throughput often results in low optical density. The penetration is measured visually or with an optical densitometer. 0 Low or inconvenient so-called bleeding. If ink is applied to a surface where ink of another color has already been applied, one color may surface in the other. This problem, which is caused by too slow penetration into the paper, is called bleeding and is measured visually or with the help of image analysis.

In order to provide a paper with good printability properties for ink jet printers, the prior art has only offered very expensive special pigments and when using cheaper pigments such as calcium carbonate or clay, these printability properties have not been appreciably affected.

In summary, a surface-glued paper has good physical properties such as low density and high rigidity that provide good runnability in printing presses, copiers, printers and conversion machines, for example. envelope manufacturing machines but show poorer print quality when using ink jet printers and various printing presses. A pigmented or coated paper provides significantly better print quality but has poor stiffness due to its low thickness and is often perceived as "slippery". However, in order to achieve good quality at more demanding inks with the help of ink jet printers, expensive special pigments have hitherto been required in papermaking.

The patent literature describes the use of crosslinked starch in connection with papermaking, whereby, however, the crosslinked starch is not used in surface treatment compositions. Such patents are, for example, US 4,810,785, US 5,122,231, US 5.3 68,690, US 5,523,339. 10 15 20 25 30 35 P1647 524 281 S -,. From U.S. Pat. The other part of the content of solid particles consists of calcium carbonate.

U.S. Pat.

From DE 26 05 575 it is known to use 0.5 - 10 parts of ungelatinized starch particles in a latex coating specially developed for banknotes to meet the very special requirements for banknotes.

SE 421 638 shows an embossable and printable wallpaper that can have paper or cardboard as a base material. The wallpaper is coated with a coating that consists of unpaved starch in 10 - 100% by weight.

DISCLOSURE OF THE INVENTION The object of the invention is to offer a surface treatment composition, by means of which the above-mentioned problems are eliminated or limited and / or large economic gains are obtained. The invention can be advantageously used for paper of various types, such as paper for inkjet printers, envelope paper, paper for copying, paper for laser printers or other types of paper or cardboard.

A main object of the invention is thus to provide a new and improved surface treatment composition which can be used in the manufacture of paper.

Another object of the invention is to provide a new surface treatment composition which gives the paper better printability properties when using ink jet printers and printing presses in a much more cost effective manner than for known compositions.

Another object of the invention is to provide a new and improved surface treatment composition which gives the paper higher bulk.

Another aim of the invention is to provide a new and improved surface treatment composition which gives the paper higher air resistance. 10 15 20 25 30 35 P1647 524 281 6 »n u n ou n G,,. . »N ~ e.

Another object of the invention is to provide a new and improved surface treatment composition which gives the paper higher opacity.

Another object of the invention is to provide a new and improved surface treatment composition which gives the paper higher brightness and / or can reduce the need for optical brightener.

Another object is to provide an improved papermaking process.

Another purpose of the invention is to provide paper with improved properties.

According to the invention, these and other objects are achieved by the provision of a surface treatment composition which comprises at least one crosslinked starch which has not at all or only partially dissolved and which is also present in the form of solid starch particles (pigments) in an amount of more than 65% at room temperature and calculated on the solids content of the composition. Furthermore, at least 10% of the starch content of the composition in the entire temperature range 20 f 50 ° C consists of solid particles.

According to one aspect of the invention, the proportion of starch particles constitutes more than 70%, preferably more than 75% and even more preferably at least 80% at room temperature and calculated on the solids content of the composition.

It is preferred that the limits just stated for the proportion of starch particles in the composition also apply at 50 ° C.

Crosslinked (also called crosslinked) starch is obtained by reaction with bi- or polyfunctional reagents. These react with hydrox your hydroxyl groups in the starch and thereby give rise to bridging between the starch molecules. With an increased degree of crosslinking, the starch coma becomes more and more resistant to sticking.

The crosslinked starch used in this invention may include starch treated with one or more of the compounds described in “Starch Derivatives; Production and Uses ”by Morton W. Rutenberg and D. Solarek and“ Starch; Chemistry and Technology fi Chapter X, pp. 324 - 332. 1984 and in the patents referred to above. 10 15 20 25 30 35 P1647 524 2817 v | v n or n t: '_ _. «- ø i.

Such crosslinking compounds may consist of methylamine compounds, polyvalent (flervalent) acids, polyvalent acid esters, polyvalent acid halides, polyvalent acid anhydrides, polyaldehydes, polyepoxides, polyisocyanates, divinyl compounds, phosphoryl chloride, polyamine polyhydric phyllide; and di- and triprotonic acids, sodium hypochlorite, phosphorus oxytrichloride.

With no or low degree of crosslinking, the starch dissolves if a starch slurry is heated. With an increased degree of crosslinking, the tendency of the starch to change into a loose form decreases. The starch used in the invention can have very different degrees of crosslinking. From a relatively low degree of crosslinking where about 10% of the starch is present as solid particles at a temperature of about 20 to 50 ° C, and the rest of the starch is a binder in loose form, to a high degree of crosslinking where about 100% of the starch present as solid particles at the above-mentioned temperature range. It is preferred that at least 15%, preferably at least 20% of the starch content of the composition at about 20 to 50 ° C be constituted by starch particles according to the invention. It should be noted that what has just been said does not contradict the provision that more than 65% of the solids content must consist of starch particles, provided that the solid pigments of the composition consist essentially only of these starch particles or only to a very small extent comprise other types of pigments. Regardless of the degree of crosslinking, the composition may also contain another type of soluble starch or some synthetic polymer to obtain a sufficient amount of binder and further improved printing properties. Examples of such polymers are styrene-acrylate, styrene-maleic anhydride, polyvinyl alcohol, polyvinylpyrrolidone, polyvinylformamide.

To achieve some of the paper properties previously mentioned, such as good printability properties when using inkjet printers, the starch should be further modified. The starch can be modified to appear cationic, anionic, amphoteric or hydrophobic.

In the preparation of cationic starches, the starch is substituted with cationic groups, most often using ammonium compounds which are, preferably, quaternary, but which may also be primary or tertiary. Such a cationization process of starch is well known and is described i.a. in U.S. Pat.

This procedure is well described in the literature, i.a. in the above-mentioned writings by Morton 10 15 20 25 30 35 P 1647 524 281 8 o n in -Ho W. Rutenberg and D. Solarek resp. STARCH: Chemistry and Technology by Roy L.

Whistler, James N. Bemiller and Eugene F. Paschall. In the production of amphoteric starch, the starch is substituted with both cationic and anionic groups.

Preferably the starch has a degree of substitution of 0.01-0.30 and even more preferably 0.02-0.20. However, uncharged starch can also increase according to the invention.

In the preparation of hydrophobic starches, your reagents can be used, of which benzyl chloride, styrene oxide, phenyl isocyanate and butyl glycidyl ether can be mentioned.

By reacting the starch with, for example, the chlorohydrin of a quaternary ammonium compound, cationic hydrophobic groups are introduced into the starch molecule.

In order to obtain a suitable particle size of the starch, a mechanical processing, such as extrusion or grinding, may be necessary. A preferred particle size is 1-50 μm and even more preferably 1-25 μm.

According to one aspect of the invention, the surface treatment composition may also comprise a minor amount of other pigments in the form of solid particles. Such pigments may, for example, consist of calcium carbonate, clay, silica and / or alumina. However, it is also conceivable, and in many cases preferred, that the content of solid particles in the composition essentially consists only of the inventive starch particles.

It has surprisingly been found that with the above-mentioned composition one obtains effects which considerably reduce or eliminate many of the shortcomings which can be connected with the prior art. Among other things, the paper's printability properties, brightness, opacity, bulk, surface smoothness and lu fl resistance are improved. More specifically, the printability properties of the paper are improved when using ink jet printers, whereby the ink output decreases, the optical density increases, the throughput decreases and the bleeding decreases or is eliminated. Furthermore, the printability properties of the paper are improved when using printing presses based on offset or flexo technology. When color copying is improved e.g. image quality. Double feeding with suction-fed printing presses is avoided and envelopes made with paper which have been surface-treated with the said composition are excellent in automatic document loading machines.

One theory is that the positive, surprising effects of the invention are due to the fact that the particles of the surface treatment composition are amorphous and thus have a significantly higher 10 15 20 25 30 35 524 2819 P1647 s n n «nu -. n - u e | - | | Q | n n v v. n sn speciñk surface than conventional pigments have. The high specific surface area of the filler composition is probably also the reason for the improved printing properties of the paper when using ink jet printers as the paper absorption of the ink is improved due to increased number of capillaries with smaller radius. This large surface area also absorbs inks in offset printing in an advantageous manner. It has further been observed that even though the starch particles are ungelatinized, they exhibit an advantageously sticky surface.

When printing using the otek exotechnology, the denser surface may be the explanation for the improved printing result when the fl exo ink stays in the surface of the paper. At the same time, the large surface area of the starch pigments prevents slow drying due to its good absorbency.

The plastic nature of the particles makes them easily calendered, whereby only a relatively low line pressure needs to be used in the machine light to obtain the desired surface smoothness.

This low line pressure together with it, compared to calcium carbonate and clay, considerably lower density of the starch particles, can explain the high bulk obtained compared to conventional surface glued or coated paper. The opacity of the starch particles increases the opacity of the paper compared to the effect of the transparent starch solution used in surface gluing.

EXAMPLE.

In a pilot experiment, a non-surface-treated paper with a basis weight of 80 g / m 2 was coated with a composition consisting only of cross-linked (cross-linked) starch in water at room temperature. The starch was delivered by Emsland-Stärke Gmbh. with the trade name F 6270. The starch was cationic with a nitrogen content of 0.35%. The average particle size had been reduced to about 10 μm by mechanical processing. About 15% of the starch went into solution and thus about 85% of the starch appeared as solid particles. The spread was calculated at 1.5 grams per square meter and side. The application on the paper surface was done with a SymSizer from Metso Oy. This paper is called A.

As a reference, a paper glued in a conventional manner with starch solution, i.e. all starch was in loose form. The spread on this paper was also calculated at 1.5 grams per square meter and side and the nitrogen content was 0.15%.

This paper is called B.

The physical paper properties are reported in Table 1. 10 15 20 524 281 10 _ Pl647 Table 1 Law Paper A Paper B Surface weight 84 gr / m2 84 grams / m2 Air resistance (Gurley) 29 seconds 14 seconds Opacity 93.4% 91.1% Bulk 1.42 cm3 / gram 1.34 cmz / gram Whiteness 159% CIE 152% CIE Surface roughness 192 ml / min Bendtsen 208 ml / min Bendtsen The optical density was measured when printing with a Hewlett Packard 950 C inkjet printer and the color bleeding was measured when printing with an inkjet printer. of the type Epson 980 C. These printers are very common and are excellent tools for evaluating the print quality of various papers. The measured optical densities are reported in Table 2.

Table 2 __ M Property Paper A Paper B Density- black 1.50 1.48 Density - cyan 1.39 1.32 'Density - magenta 1.29 1.20 Density - yellow 1.14 1.08 Bleeding 2.0 2.0 In the visual assessment of throughput, paper A showed significantly less penetration into the paper compared to paper B. Both papers showed minimal ink output.

When printed with other ink jet printers, the same improvement of, in particular, the optical density was achieved. The difference between papers A and B was perceived as very clear during visual assessment (blind test) of samples printed with inkjet printers.

The invention is not limited to the described embodiments but can be varied within the scope of the claims.

Claims (1)

1. 0 15 20 25 30 35 524 281 11 P1647 now CLAIMS 1. Surface treatment composition for paper or board, in the form of an aqueous composition, characterized in that at room temperature and calculated on the solids content of the composition it comprises starch particles in an amount of more than 65 %, wherein the starch for the starch particles consists of crosslinked starch and wherein at least 10% of the starch content of the composition in the entire temperature range 20 - 50 ° C consists of starch particles. Surface treatment composition according to claim 1, characterized in that the proportion of starch particles constitutes more than 70%, preferably more than 75% and even more preferably at least 80% at room temperature and calculated on the solids content of the composition. . Surface treatment composition according to claim 1 or 2, characterized in that at least 15%, preferably at least 20% of the starch content of the composition consists of said starch particles, at room temperature. The surface treatment composition according to any one of the preceding claims, characterized in that a part of the starch is present in dissolved form in the composition at room temperature, the dissolved starch constituting a binder in the composition. Surface treatment composition according to any one of claims 1-3, characterized in that substantially all of the starch is present in the form of starch particles at room temperature. Surface treatment composition according to any one of the preceding claims, characterized in that the starch of said starch particles is crosslinked by one or more compounds selected from the group consisting of methylamine compounds, polyvalent (flvalent) acids, polyvalent acid esters, polyvalent acid halides, polyhydric acid halides, polyvalent acid halides , polyisocyanates, divinyl compounds, phosphoryl chloride, polyamine polyepoxide resin, 1,4-butane diol diglycidyl ether, epichlorohydrin, trimetaphosphates, mixture of anhydrides of acetic acid and di- and triprotonic acids, sodium hypochlorite, or mixtures thereof. Surface treatment composition according to any one of the preceding claims, characterized in that the starch for said starch particles is based on potatoes, corn, wheat, waxy maize, rice or tapioca. 10 15 20 25 30 35 10. 11. 12. 13. 14. 15. 16. 17. 524 281 12 -. n f no __ __ P1647 Surface treatment composition according to any one of the preceding claims, characterized in that said starch particles have a particle size of 1-50 μm, preferably 1-25 μm, in said amount. Surface treatment composition according to any one of the preceding claims, characterized in that it also comprises a binder, preferably dissolved starch or a synthetic polymer. Surface treatment composition according to one of the preceding claims, characterized in that the starch for the starch particles is derivatized by chemical, physical and / or enzymatic means. Surface treatment composition according to any one of the preceding claims, characterized in that the starch for the starch particles is cationic, anionic or amphoteric. Surface treatment composition according to any one of the preceding claims, characterized in that the starch of the starch particles has a degree of substitution of 0.01-0.30, preferably 0.02-0.20. Surface treatment composition according to any one of the preceding claims, characterized in that the starch of the starch particles is hydrophobic. Surface treatment composition according to any one of claims 1-12, characterized in that the starch for the starch particles is hydro fi l. Method in the production of paper or board, characterized in that a surface treatment composition according to any one of claims 1-14 is applied to the paper or board, preferably on a web of the same which is dried there. Method according to claim 15, characterized in that the surface treatment composition is applied to the paper or board web by spraying or by sheet coating or by means of rollers. Method according to claim 15 or 16, characterized in that the surface treatment composition is applied to the paper or board web to form a surface layer of 1-10 g / m 2 per side, preferably 1-5 g / m 2 per side, dry-think. »4» f en 524 281 13 .. .. .. P16 ”ø ~ | | o a ø | f u | ø »o 18. Paper or paperboard, characterized in that it has a surface layer of a surface treatment composition according to any one of claims 1-14. Use of a surface treatment composition for paper or board, in the form of an aqueous composition, which at room temperature and based on the solids content of the composition comprises starch particles in an amount of more than 65%, for surface treatment of paper for ink jet printers.