US 2915410 A
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nited States Patent DRY SIZE AND METHOD OF MAKING THE SAME Alfred Schneider, Konolfingen-Dorf, Bern, Switzerland, assiguor to A. Schneider G.m.b.H., Konolfingen, Bern, Switzerland No Drawing. Application February 3, 1958 Serial No. 712,661
Claims priority, application Switzerland February 4, 1957 7 Claims. '(Cl. 106-439) This invention relates to sizes, and more particularly to a dry size for paper and the like, and methods of making the same.
In order to render the paper capable of being written on, the paper is sized. The surface of the paper web may be sized with animalglue, casein etc., but in the majority of cases, pulp sizing is resorted towhere the size is di rectly added to the paper pulp prior to the formation of the paper webtherefrom. The preferred size for use in this bulk or pulp sizing method is rosin, saponified by means of an aqueous solution of soda or soda lye, i.e. converted into the sodium rosinate in accordance with the following equations:
If the soda or the sodium hydroxide are used in theoretical amounts, a so called fully saponified rosin size is obtained; if the substances are used in amounts less than those of theory, so called free rosin sizes result wherein a certain amount of non-saponified rosin forms, with the saponified constituents, an emulsion, the saponified constituent, the sodium rosinate, acting as emulsifier.
The sizes thus prepared are made in emulsions of about 30-50%, in which form they are either marketed or utilized. Following the addition of the size emulsion to the paper pulp, aluminum sulfate is added to precipitate the rosinate, in accordance with the following equations:
for 1 kg. of fully saponified rosin size, to about 1 /2 kg., while for 1 kg. of free rosin size the amount of aluminum required is, of course, somewhat smaller ,.i.e. about 1 kg. r'
While in the past, the rosin size was manufactured by the paper mills, the modern trend is toward a manufacture of the rosin size on the outside. As a rule, fully saponified rosin sizes are supplied in the form of 30% emulsions, and free rosin emulsions in the form of 50% aqueous emulsions, to be shipped inbarrels, containers or tank cars. The high water content of these sizes, however, render such shipment expensive; moreover, during the cold season these high water content sizes are in constant danger of freezing. In view of these various disadvantages, a very real demand has been developed in this art for a dry rosin size.
' It is known to prepare dry rosin size by drying fully saponified rosin size, at times with an addition of water repellent substances, by a spray drying process or on roller driers. These drying methods, however, render the dry sizes very expensive; besides, the dry sizes thus obsaponified sizes.
-pulp, must receive additional water.
2,915,410 Patented Dec. 1, 1959 tain'ed are more or less highly sensitive to atmospheric humidity. Moreover, for reasons well known to every worker in this field, these methods are not susceptible of utilizing free rosin sizes which, however, are preferred in the paper making art as they consume much less aluminum sulfate for precipitation purposes than the fully For these several reasons, the dry sizes available heretofore have not been able to meet the demandin the art-noted above.
On the other hand, liquid rosin sizes are known which in addition to rosin, contain substantial amounts of hydrocarbons in emulsified form. There has been no suggestion in the prior art, however, that hydrocarbons might be incorporated in dry sizes.
It is an object of the present invention to provide dry rosin sizes for use in paper sizing which have all the advantages of a dry size, yet none of the disadvantages of dry sizes known so far, and which therefore are susceptible of meeting the demand in this art for a dry size thoroughly adapted for the paper making requirements.
during or following the mixing, water may be added to ybe evaporated subsequently. The properties of the products obtained vary somewhat corresponding to the several variations of the method of preparation. As the liquid hydrocarbon, kerosene is preferred, but it must not be present in substantially more than 5% by weight calculated on the weight of the rosin, because of its odour.
'The sodium aluminate is preferably used in an amount of 25% by weight calculated on the weight of the rosin.
If mixing takes place in the cold and in the absence of water, for example by milling the components, continuously or in batches, in a ball or bar mill, a somewhat hygroscopic powder is obtained. This powder represents a very cheap, yet useful dry size with a fine sizing action. which prior to use, i.e. before it is added to the paper The powder constitutes a physical mixture. In the presence of moisture,
however, reactions occurbetween the sodium aluminate "and the rosin which are undesirable.
A better stability with respect to humidity is obtained if the size powder is fritted at about C. and the clinker-like product thus obtained, subsequently is milled again. This procedure, apparently, has the result that the particles of sodium aluminate are coated by the rosin.
A dry size of equivalent quality is obtained by melting rosin and kerosene, stirring sodium aluminate into this melt, and comminuting the melt once it has solidified.
The addition of water during or following the mixing has the result that not only a physical mixture is obtained, but that moreover chemical reactions occur also. It is presumed that a conglomerate composed of a small portion of sodium rosinate and a larger portion of colloidal aluminum rosinate is formed, the sodium rosinate acting as a protective colloid. Dry rosin sizes thus prepared can be added to the paper pulp in the dry state and thus, do not require any addition of water prior to use.
The same reactions which take place in the preparation of dry rosin sizes involving an addition of water, occur also with the product prepared in the absence of water, if the water is added prior to its use; in either case, at the time the product is added to the paper pulp, at least a part of the rosin is present in the form of aluminum rosinate and some sodium rosinate. Because of the preponderance of aluminum rosinate, the size is precipitated to the point of 100%, on the paper fiber even in an alkaline medium. Consequently, an addition of aluminum sulfate such as was required by all the known sizing methods, is not required by the present process. It is, however, recommended to add some aluminum sulfate during sizing, for purposes of correcting the processing water, as well as of neutralizing the fiber mixture, as free alkali injures the paper, which noxious effect is eliminated by an addition of aluminum sulfate which is known to be strongly acid in aqueous solution due to hydrolytic decomposition; moreover, the addition of aluminum sulfate results in the formation of a material quantity of aluminum hydroxide which is like- 1y to act as carrier for the size particles, distributing the same in a state of extremely fine subdivision on the fibers so as to materially assist and enhance the sizing process.
In addition to the approximately 50% saving of precipitant (aluminum sulfate) afforded by the rosin size according to the invention, the invention makes an additional saving in that the size can be used more economically than any of the known sizes, Calculated on the dry substance, the saving obtained from the use of the present sizes, compared with a conventional highest grade rosin size, amounts to at least 30%. The rosin'size according to the invention is bare, for all practical purposes, of any sensitivity to the salts causing the hardness of water, atmospheric moisture and high drying temperatures. The present sizes are thoroughly soluble in cold water. They are quickly and completely distributed throughout the paper pulp, and precipitate in a neutral medium.
The invention may be illustrated by the following examples.
Example 1 In an open melting vessel having a steam jacket and agitator, of conventional construction, 100 kg. rosin are molten with 2-3 liters kerosene and heated to a temperature not exceeding 95 C. To this melt, 25 kg. dry, filltly ground sodium aluminate are added in portions. Following further agitation for a period of about 15 minutes, the melt obtained is drained. Dependent on the type of rosin used, the melt solidifies completely at about 45-50 C. forming a brittle clinker. This prod uct is finely ground in a hammer mill, sifted and packed in paper bags.
When it is to be used, the dry size is dissolved, before it is added to the paper pulp, in cold water, 70 parts of water being used for 30 parts of the dry size. A suitable colloidal solution is obtained which has an extraordinarily high sizing action. About 300-500 g. aluminum sulfate are used per 1 kg. dry size.
Example 2 100 kg. rosin in the form of small lumps are mixed with 2 liters kerosene and ground with 25 kg. sodium aluminate in a ball mill, the powder obtained is sifted and packed.
As far as its application and the sizing action is concerned, this dry size is equivalent to the size made in accordance with Example 1. The powder, however, is somewhat more hygroscopic.
Example 3 100 kg. rosin are mixed with 2 kg. kerosene and 25 kg. sodium aluminate. The size powder obtained is sub- 2,91a,41o H 4 sequently fritted at about C. On cooling, a clinker is obtained which is finely ground.
The finished dry size product has the same properties as the product according to Example 1.
Example 4 100 kg. rosin are finely ground with 2 kg. kerosene and 25 kg. sodium aluminate, and kneaded in a kneader with 30 liters water. The dough thus formed is dried at about 80 C. and milled.
The dry size thus produced is somewhat more expensive than the products according to the preceding examples, because of the drying process. It ha however the advantage that it is not required to be dissolved prior to use in the paper mill but may be added to the paper pulp in the dry state. The sizing action is the same as with the products of the preceding examples.
Example 5 100 kg. rosin are most finely ground and together with 2 liters kerosene and 25 kg. sodium aluminate, dissolved in 250 liters cold water in a vessel provided with an agitator. A dispersion is obtained which is dried on a roller drier or in a spray drier, to be subsequently milled. This dry size also can be added to the paper pulp in the dry state, i.e. without requiring any previous dissolution. This procedure, however, though simple, is even more costly than that of Example 4, because of the large quantity of water to be evaporated.
I wish it to be understood that I do not desire to be limited to the exact details of procedure or composition described above for illustration purposes only, as numerous modifications of these details which involve no departure from the spirit of the invention nor any sacrifice of the advantages thereof, are likely to occur to workers in this field.
1. The method of making a dry rosin size, particularly adapted for use in paper sizing, comprising mixing rosin with about 0.5 to 5 percent by Weight, calculated on the weight of the rosin, of kerosene, and about 15 to 30 percent by weight, calculated on the weight of the rosin, of sodium aluminate.
2. The method according to claim 1, wherein the mixing takes place at a temperature not substantially exceeding C.
3. The method according to claim 1, wherein the mixture is subsequently fritted at about 80 C.
4. The method according to claim 1, wherein the mixture is subsequently kneaded with a small quantity of water, and thereafter dried.
5. The method according to claim 1, wherein the mixing takes place in the presence of enough water that a dispersion is formed, and the dispersion thus obtained is subsequently dried.
6. The method according to claim 1, wherein kerosene is used in an amount of 2 percent by weight, calculated on the weight of the rosin, and sodium aluminate in an amount of 25 percent by Weight, calculated on the weight of the rosin.
7. A dry rosin size particularly adapted for use in paper sizing obtained by the method of claim 1.
18,716 Great Britain Oct. 19, 1889