CA1228703A - Use of serpentinite as an additive - Google Patents

Abstract

THE USE OF SERPENTINITE AS AN ADDITIVE

ABSTRACT

The invention relates to the use of finely powdered serpentinite, the effective ingredient whereof is serpentine {(OH)4Mg3 (Si2O5)}, as an additive in paper industry. According to the invention, serpentinite is suited to be used as a filler in paper or board or as a remover of pitches, resins, extractives and other so-called stickies and as a collector of fines.

Description

THE USE OF SERPENTINITE AS AN ADDITIVE

The present invention relates to the use of finely powdered serpentinite as an additive in paper industry, either as an additive or filler in paper or board, as a remover of pitches, resins, e~tractives and other so-called stickles, or as a no-trainer of flour both in paper industry processes-and in payer industry process waters. Serpentinite can be used for these purposes either as such or blended with a suitable material, for instance talcum.

In paper industry fillers are primarily used in order to replace part of the expensive wood fiber ingredients by cheaper mineral ingredients, but fillers also affect many properties of paper and board, either improving or weakening the quality.

Fillers improve several characteristics of paper and board, par-titularly optical qualities and qualities relating to printabi-lily. Apart from saving wood fibers, the main purpose for using fillers is to improve opacity, brightness, printing ink adsorb-lion, the smoothness of the surface, the evenness of the imprint, porosity and the feel of the paper, as well as the friction, stiffness and flatness ox paper and board. Other effects are increased density, improved dimensional stability and smoothing of the look-through.

Remarkable porosity is generally also required of the filler, mainly due to printability reasons. Printing ink penetrates best into porous material with a large specific surface. Fillers improve the refractory qualities of paper and board. If the filler-fiber network is as dense and strong as possible, the refractory properties are good.

Fillers generally weaken the strength qualities and sizing dune-ability of paper and board. Large filler additions may cause tinting in the drying section of the paper machine, on the cutter and in the calenders. The reason for tinting is the weakening of picking resistance, which is caused by fillers, and it can be prevented for instance by starch additions or by top sizing.

2. 3 The most important paper and board fillers in current use are bolls, talcum, gypsum, chalk, calcium carbonate, barium sulfate, siliceous earth, titanium dioxide, zonk sulfide, aluminum hydroxide, montmorillonite and synthetic silicates.

The greatest disadvantage with fillers is their weak adhesion to the fiber network. The main reason for this so-called weak no-tension of the fillers is the fact that the z-potential of most fillers, as well as that of most fibers, is negative. Therefore the most important factor affecting the retention is the filter effect created when the fiber network retains the filler particles.
The filter effect itself is determined by the thickness of the pulp web conveyed on the wire, the density of the fiber net and the strength of the suction imposed on the web.

On the other hand, also the physical properties of the filler particles affect the retention. Large particles are filtered better than small particles, which easily penetrate the filtering layer. In this respect an elongate or fiber-shaped particle is preferable to a ball-shaped particle. Heavy particles are not filtered as easily as light particles.

A number of problems in paper industry arise when pitch, resin - and extractives enter the process, and particularly when various stickles attached to recirculated material, i.e. recirculated fibers, enter the process. These stickles consist of various hot-melt glues, waxes, adhesive tapes, bitumic impurities and pitch. All of these stickles cause several drawbacks both in the machine and the product. They stick into the pores of the felt located on the wire and thus gradually prevent the water from filtering through the felt. As a result too much water tends to remain in the pulp. During operation the stickles stick onto the rolls of the machine when the temperature in the aquaria ~ri~e~s^~ma~x. -130C). The sticking kiwi ye seen as bun zones in the drying cylinder. As a result both the appearance and the durability of the final product are disadvantageously affected.

In order to remove the stickles, several chemicals are used in the prior art, for instance albumen, sulfuric acid, resin glues, ~2~7~3 . -3-slimicides, urea-based substances, substances containing phosphate or nitrate, ammonia salts, crystal and talcum.
An example of the use of crystal is the SW inventor's certificate 579,367, which also mentions the use of serpentinite and breast as additives in crystal in order to increase the z-potential. At present talcum is probably the most popular remover chemical for pitch and stickles. The difficulties in removing the stickles are caused, among other things, by the fact that the stickles are often peeled off the surfaces of the recirculated fibers in comparatively large, plate-like fractions.
Talcum, which is used for removing extractives, is not as effective in removing large particles of stickles.
Unlike stickles, extractives~are dispersed in small drops-which can be bound by mineral ingredients. the sticky particles have a very light specific weight density 0.8-0.9 g/cm3, lighter than the fiber), therefore they are not removed in top separators. In order to remove the stickles, the mineral ingredients should cover the sticky particle on each side so well that its specific weight would increase. In that case the sticky particle could be removed from the process in a top separator.
If the sticky particles are only partly covered by the mineral ingredients, they are more easily melted as the temperatures rises along with the process.
,, According to the present invention, serpentinite can be used successfully in paper industry both as a filler in paper or board, as a remover of pitch, resin, extractives and stokes, and as a retainer of flour.
In accordance with the invention, there is provided a paper making process wherein a paper product is produced from pulp and in which serpentinite is incorporated in the pulp in an amount of 0.5 to 50%, by weight, based on the weight of the pulp, the serpentinite being in finely divided form.

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-pa-In particular the serpentinite is incorporated in an amount of at least 1.5%.
In the case where the serpentinite is incorporated in the pulp to remove pitch, resin, extractives and stickles, it is suitably incorporated in an amount of 1.5 to 20%, by weight, of the pulp.
In the case where the serpentinite is incorporated as filler it is suitably employed in an amount of 35~40%, by weight.
At a pure stage serpentinite is in the form of a moo-clinical, cryptomerous magnesium silicate, serpentine [(Omegas)]. The lattice often contains iron and aluminum. The metal- content-and particularly the iron -content often determines the color of the serpentinite, and consequently its brightness, too. Serpentine belongs to the so-called network silicates and is generally found as an opaque, soft and fine-flaky compound. Some types of serpentinite are softer than talcum. The serpentine network is formed of one silicon tetrahedron layer, the negative charge whereof is neutralized by a breast layer. Per each magnesium ion, talcum has two hydroxyl ions less, and thus the breast layer receives an extra positive charge, which is neutralized 7~3 by means of another hexagonal layer of silicon tetrahedron.
when serpen-tini-te is crushed and ground, positive charges are created on the serpentine surfaces. On the other hand, talcum stays almost neutral or looses its charge in the sludge and can easily remain hydra-phobic. The extremely high slipperiness of talcum is caused by two possible slip-planes. Serpentine is less slippery because it has only one slip-plane. Slipperiness is an advantage if the paper is glazed, but in many cases it can also be a disadvantage, if the paper is used for manufacturing cc~plicated products, such as various packing pro-ducts. Due to its softness, serpentinite does not damage or scratch the machines neither during calendering nor in the drying cylinder.
The paper pulp fires have a negative z-potential, whereas the z-potential of serpentine is positive (> -I 10 my). This feature is very important as regards the use of fillers, the removal of stokes and the collection of fines, because serpentine is easily attached to the fiber network. In this case serpentine also binds the fines. Thus the filter effect of the fiber network, which retains the filler part-ales, looses its importance with respect to retention. Serpentine also has a crystalline fox which is advantageous with respect to retention. Nina used as a filler, serpentinite does not need additional chemicals in order to stick onto the fiber surface.
I've sticking of serpentinite on the fiber surface is enhanced by the exceptionally large specific surface of serpentinite, which varies between 50,000 - 500,000 crying depending on the case, and by the great porosity of serpentinite. The high melting point (around 1400C) of serpentinite, and the fact that it gradually melts into liquid while the crystal water is evaporated, render good refractory properties for a paper which is filled or covered with serpentinite. The porosity of of serpentinite also allows the use of heat-consuming additives.
Among the advantages of serpentinite can be mentioned its hydra-fullest, which leads to easy disintegrability, which again helps the treatment of mineral ingredients. Moreover, the softness of serpentinite makes it possible to use a grain size I

larger than generally with fillers; the large grain size of serpentinite increases stiffness and thus reduces curling for example in envelope papers.
As regards the removal of stickles and fresh pitch, serpentinite has many advantageous characteristics: it has a positive z-potential, which leads to good adhesion on the surface of the sticky particles, it is easily disintegrable (hydrophilic), and it has a large specific surface and high porosity.
Consequently serpentinite can be used in paper industry for removing fresh pitch and extractives from lumber, particularly in the pro-diction of grounded pulp and thermal mechanical pulp, as well as for removing stickles attached to recirculated fibers. According to the conditions in each factory, serpentinite is added for instance in the slushes, in the refiners, in a suitable pulp chest near the head box of the machine, in the suction side of the white water pump, or in the pulper, when recirculated fibers are in question. The sticky particles can be coated with serpentinite so completely that they can either be removed from the process before the filter presses and the diver section cylinders for instance by means of cleansers, or the sticky particles can be made so completely insert by serpentinite, that they can pass through the machine without disturbing the process.
Modern paper factories have closed white water systems, and the fresh pitch and stickles entering the process are concentrated in the white water. From time to Tory the so-called closing limit becomes acute.
Serpentinite can also be used in these white waters in order to separate pitch and stickles. When serpentinite is adsorbed on the surface of the sticky particle, it can easily be removed from the water for instance by means of flotation or sedimentation.
In the removal of stickles the grain size of serpentinite is very important, because finely ground serpentinite coats the sticky particles better than a coarsely ground material, so that the coated particles in the paper machine remain unmelted longer than such particles which do not have this protective coating.

It has been empirically proved -that serpentinite increases the friction of paper but does not wizen its tensile strength like most other fillers. This is due to the positive potential of serpentinite, which leads to a solid join-t between the serpentinite particle and the negatively charged fiber. Serpentinite has good friction and strength qualities, and therefore it is a preferable filler for example in building paper, industrial wrapping, test liner, corrugated fiberboard and paper core board.
The color of serpentini-te sets certain limits to its use in paper industry as a filler and remover of sticlcies. Generally the color of serpentinite is grew. If the paper in question has high quality requirements as regards color, light-coloured serpentinite can be used as a filler. Another possibility is to blend serpentinite with talcum in a required proportion, for instance in connection with double-lamination. If part of the pulp is made of recirculated fiber, the removal of stickles is essential. In that case talcum can be totally replaced by serpentinite, which has a larger specific surface and a better adsorption capacity In those branches of paper industry which use recirculated fiber, for instance in bag industry, the friction increase caused by serpentinite is an essential advantage.
Apart from removing sticky particles and making them inert, serpentinite can be used in removing color particles and printing ink leftovers in connection with the drinking of the pulp.
Roy filler proportion in paper and board varies remarkably depending on the type of paper in question. With offset paper the filler pro portion is 0-10% of the total amount ox pulp, whereas with LWC-paper the filler proportion is 35-40% and with same wallpaper bases as high as 50%. As was already mentioned, in same cases the filler can be pure serpentinite, and in other cases the serpentinite can be blended with for instance talcum.
Compared to the total volume of pulp, -the proportion of the agent meant for removing stickles is relatively small, generally between 1.5-20%. On the other hand, serpentinite has better qualities for removing pitch, extractives and sticks than the convent tonally used removers. Thus the prior art removers can 7. Z 3 either totally or at least in major part be replace by serpent finite. The blending agent can be for instance talcum suited for this purpose.

Example 1 (comparison example) This comparison example uses ordinary brown pine sulfite pulp which was prepared for producing raft sack paper. The qualities of the pulp are described by the following indexes: surface weight 108, porosity Gurney s/100 ml 90, tensile index 75, stretch 6,7%, tear index 12,0, ashes 0,4, internal bond strength 30Z J/m2, lo Taber-rub 10,7 mg/1000g/~5 cycles; sheet: density 746 kf/m3, and friction coefficient on the glossy side 0,39 and on the coarse side 0,39.

Example 2 Paper friction (cf. example 1) Paper friction increases remarkably when serpentinite is used as filler. With a 10% serpentinite addition, the friction on the coarse side of the paper reached the reading 0,50. On the glossy side the friction reached the reading 0,42. In both cases the paper friction was undoubtedly increased.

Example 3 Paper stiffness Paper stiffness was clearly increased after serpentinite add-lion. The softness, grain shape and adhesion of serpentinite ; to the fibers allowed the use of larger grain sizes, for instance -10 m 40% and -20 m 100% compared to conventional fillers, for example talcum and bonus, -10 m OWE.

example 4 Paper strength qualities (cf. example 1) The following measured indexes prove that the paper strength qualities remained essentially similar irrespective of the add-Zion ox s~p-e~tinite, which was used as the filler. Thy specific surface of serpentinite was very large i.e. 46 mug With a 10% serpentinite addition, paper ashes were increased to OWE.

a) tensile index When the serpentinite addition was OWE of the fiber amount, there was no essential change in the tensile index, which no-mined in 74. With a 10% addition there was a change which 7~3 could be expressed digitally, the reading of the tensile index now be-in 68. In -the case of grounded pulp containing recirculated fibers, a 15~ serpen-tinite addition is required before -there is a noticeable change in -the tensile index.
b) stretch Helen -the serpentinite addition was 10% of the fiber amount, the stretch ox -the paper remained the same as with a 5% addition, i.e. 5.8. In general -the stretch was slightly decreased, and it is obvious that a -Ire, addition did not ye-t have a negative effect on the starch.
c) -tear strength When the serpentinite addition was 10% of the fiber amount, the tear strength of the paper remained the same as with a 5% addition, i.e., 12.4. Thus -the tear strength remained practically unchanged. The 10 addition did no-t weaken the tear strength.
d) bursting strength When -the serpentinite addition was 10% of the fiber amount, -the burst-in strength of the paper remained -the same as with a 5% addition, i.e. the bursting strength also remained unchanged. The 10% addition did not weaken the bursting strength.
Example 5 Removal of pitches, resins, extractives and other stickles (all of which are later referred -to as sticky particles) I-t was observed that serpentinite was adsorbed on the surfaces of the sticky particles.
The adsorption was detected by means of a scanning electron microscope (SUM), and a microanalyser was used in analyzing the serpentinite adsorbed on the surfaces of the sticky particles, so that the line analysis of for instance silicon (So) was run over -the sticky particles. I-t was observed -that the silicon (So) intensity increased remarkably when meeting the sticky particles.
Serpentine was adsorbed on the surfaces of the sticky particles owning -to its exceptional surface qualities, i.e. large specific surface and hydrophilici-ty, and therefore -the adhesion of the said particles onto -the pressing felts on the paper machine wire was reduced. This means an elongation in tile operation age of the pressing felts, which directly lowers the operation costs.

- Moreover, the adsorption of the sticky particles onto the various members of the paper machine, for instance onto the drying Solon dons, was reduced, because the sticky particles were coated by the adsorbed serpentinite.

Example 6 Removal of pitches, resins, extractives and other stickles (all of which are later referred to as sticky particles) by means of floating in the process waters The ability of serpentinite to be adsorbed on the surfaces of the sticky particles makes it possible to remove the sticky par-tides from the process waters by means of floating the serpent finite which is adsorbed on the surfaces of the said particles.
It is generally known that serpentinite is easily floated in a wide pharaoh, but even more easily in an almost neutral area moreover, in order to be floated serpentinite does not need any special collector but only a slight amount of flotation oil. In experimental flotations it was observed that the major part of the sticky particles was removed along with the floated serpent finite. Those sticky particles that remained in the process waterer attached to the equipment used in the experiment. Experiments which were cordite by means of sedimentation without flotation gave similar results.
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Claims (26)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a paper making process wherein a paper product is produced from pulp, the improvement con-sisting in incorporating with said pulp from 0.5 to 50%, by weight, of said pulp of finely divided serpentinite.

2. The process of claim l, wherein talc is also incorporated in said pulp.

3. The process of claim l, wherein said serpentinite is incorporated as a filler for paper or board.

4. The process of claim 3, wherein said serpentinite is incorporated in an amount up to 10%, by weight.

5. The process of claim 3, wherein said serpentinite is incorporated in an amount between 35 to 40% by weight.

6. The process of claim 1, wherein said serpentinite is incorporated in an amount ranging from 1.5 to 20%, by weight, of said pulp to remove pitch, resin, extractives and stickies.

7. The process of claim l, 2 or 3, wherein said pulp is wood pulp.

8. The process of claim 4, 5 or 6, wherein said pulp is wood pulp.

9. The process of claim 1, 2 or 3, wherein said serpentine is incorporated in an amount of at least 1.5% by weight, of said pulp.

10. The process for removing pitches, resins and other adhesive particles from paper making process waters in a paper making process employing pulp com-prising:
incorporating in said waters divided serpentinite in an amount of 1.5 to 50%, by weight, of said pulp;
contacting said particles with said divided serpentinite to cause adsorption of said serpentinite on the surfaces of said particles, and separating said serpentinite with said particles from said waters.

11. The process of claim 10, wherein said separating is effected in a substantially neutral media by floatation.

12. The process of claim 10, wherein said separating is effected by sedimentation.

13. The process of claim 1, 2 or 3, wherein said serpentinite is incorporated in an amount of at least 1.5%, by weight.

14. The process of claim 10, 11 or 12, wherein the amount of serpentinite incorporated ranges from 5 to 15%, by weight, of said pulp, whereby fraction stiffness and tensile strength of the resulting paper are increased.

15. The process of claim 10, 11 or 12, wherein said pulp is wood pulp.

16. The process of claim 10, 11 or 12, wherein the amount of serpentinite incorporated ranges from 5 to 15%, by weight, of said pulp, whereby friction stiffness and tensile strength of the resulting paper are increased, and said pulp is a wood pulp.

17. A composition for producing a paper product comprising a wood pulp in an aqueous vehicle and from 0.5 to 50%, by weight, of said pulp, of finely divided serpentinite

18. A composition according to claim 17, wherein said pulp comprises wood fibre.

19. A composition according to claim 17 or 187 containing at least 1.5% by weight, of said serpentinite

20. A composition according to claim 17 or 18, containing 1.5 to 20%, by weight, of said serpentinite.

21. A composition according to claim 17 or 18, containing 35 to 40% by weight, of said serpentinite.

22. A method of treating a fibre pulp composition which comprises adding to said composition finely divided serpentinite in an amount of 0.5 to 50% by weight, of the pulp in said composition.

23. A method according to claim 22, wherein said fibre pulp composition comprises pulp in an aqueous vehicle.

24. A method according to claim 23, including contacting adhesive particles in said aqueous vehicle with said serpentinite to cause adsorption of said serpentinite on surfaces of the particles, and separating said serpentinite with said particles from said waters.

25. A method according to claim 22, 23 or 24, wherein said pulp is wood pulp.

26. A method according to claim 22, 23 or 24, wherein said serpentinite is added in an amount of at least 1.5%, by weight.