US2064387A - Manufacture of casein products - Google Patents

Description

' dustries.

Patented Dec. 15, 1936 MANUFACTURE or CASEIN raonuors Charles Schwartz, Pittsburgh, Pa., asslgnor to Hall Laboratories, Inc., Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application September 28, 1934, Serial No. 745.854

9 Claims. (Cl. 134-20) This invention relates generally to the manufacture of casein products useful in the paper, paint, glue and other industries, and more particularly to casein products containing, in addi- 5 tion to the usual'ingredients an alkali-metal metaphosphate such, for example, as sodium metaphosphate.

Casein has in recent years made an increasingly important place for itself in several in- Especially noteworthy are its uses in the paper, paint and glue industries. In all of these fields certain properties of the casein containing mixtures have been serious hindrances to the far more widespread adoption and use of this material. I have found that the admixture of an alkali-metal metaphosphate with such casein products overcomes to a great extent all of the previous disadvantages of such mixtures.

The alkali-metal metaphosphate which I prefer to use in the preparation of casein products is the soluble sodium metaphosphate sometimes called Graham's salt" which may or may not have'mixed with it a small amount oLsodium pyrophosphate to counteract the slight acidity of the sodium metaphosphate. There may also be mixed with the sodium metaphosphate or'the mixture of sodium metaphosphate and -pyro-.

phosphate, small quantities of alkalis such, for example, as sodium carbonate, sodium bicarbonate, borax, tri-sodium phosphate and sodium metasilicate, these alkalis also being added for the purpose of counteracting the slight acidity of the sodium metaphosphate. Grahams salt is believed to consist principally of sodium hexa- ,metaphosphate and may be prepared by strongly heating monosodlum dihydrogen orthophosphate, and rapidly cooling the molten mass.

In the paper industry casein products are used either as coating compositions, by which is meant compositions which are applied to the paper to give the desired finish thereto, or as sizing compositions, by which is meant compositions which are applied to the fibers or pulp for 5 the purpose of acting as a binding agent for the fibers. Casein compositions are also used in the finishing or sizing of textiles and in the sizing of porous surfaces, roofing compositions and the like. My invention will be described 50 herein as applied particularly to the coating of paper, it being understood, however, that the invention is not restricted to this particular use, but may be used for other purposes for which casein products are fitted.

55 The method now generally used for preparing coating mixtures for paper is to soak the dry casein in water for a suflicient length of time to moisten each particle thoroughly before adding the solubilizing agent. After the casein is soaked an alkali is added thereto. This is gen- 5 erally done by dissolving the alkali in a small amount of water and pouring the solution into the vessel which contains the casein.- Various alkali solubilizing agents have been used, among which may be mentioned sodium silicate, sodium 10 aluminate, sodium phosphate, sodium carbon,- ate, sodium borate, caustic soda and ammonium hydroxide. The corresponding potassium salts may also be used, but their expense makes their use infeasible. In general, selection of the s01- 15 vent depends upon the type of paper being made. Slaked lime has not proved desirable as a solubilizing agent for casein paper coatingcompositions, although it has been used with considerable success in the manufacture of casein glues. Lime, when used in casein paper coatings, has the objection that it reduces the'working life of the coating and seems to increase greatly the foaming properties of the coating.

There are certain disadvantages common to 25 all types of casein paper coatings whether or not such coatings contain lime, among which are:

1. It is very difficult to control the fluidity of the casein mixture so as to obtain the proper 30 results in the coating operation.

2. There is a great tendency for particles of the casein to remain undissolved, which particles collect in the brushes used in applying the coating and from which they drop off onto the paper,. 35 forming lumps thereon.

3. The property of foaming is pronounced in all paper casein coatings and is especially evident in those coatings containing lime.

I have found that the addition of an alkali- 40 metal metaphosphate to such coatings whether or not they contain lime greatly decreases or completely overcomes the objections to such coatings as are now in use.

In describing my invention I will confine myself to the use of the preferred alkali-metal metaphosphate, namely, sodium, metaphosphate, but it is to be understood that other alkali-metal metaphosphates such, for example, as potassium metaphosphate, lithium metaphosphate, and ammonium metaphosphate may be used. All of these metaphosphates are preferably used in the soluble form commonly known as hexametaphosphate.

In the preparation of lime-containing casein containing compounds.

Casein 100 Lime 20-30 Sodium metaphosphate 20-125 The working life of the coating is roughly proportional to the amount of sodium metaphosphate added. By working life is meant the period of time during which the coating may be worked. It is the period of time from the time at which the coating was made to the time at which it solidifies or sets or becomes so viscous that it is unsuitable for the intended purpose. If there are added, let us say, 20 parts of sodium metaphosphate, the working life of the coating may be only six hours, whereas if 100 parts are added the working life of the coating is extended to as much as 72 hours. In making the coating the casein is soaked for about an hour in about three times its weight of water, which water contains the desired amount of sodium metaphosphate, the mixture being stirred. Then while stirring the casein metaphosphate solution, the lime dissolved in 100 parts of water is added. The stirring is continued thereafter for about one-half hour and the desired mineral matter is added. The mineral matter may be white clay, precipitated chalk, or other suitable material. The amount of each of these minerals to be added varies from about 5 to 20 parts per 100 parts of casein and depends largely upon the type of coating desired.

I have found that the addition of metaphosphate to casein paper coating is very effective in solving the chief difficulty involved in the use 'of these coatings, that is, keeping the viscosity of the mixture at such a point that it may be easily applied by the brushes. It likewise reduces the amount of foaming encountered in mixtures of this type.

Although due to the complicated nature of the material involved, the exact reasons .for the improvement obtained by employing the sodium "metaphosphate are not definitely known, it is believed that the improvements are due to twofactors. The first of these is the effect of sodium metaphosphate upon certain metallic ions such as calcium and magnesium. It is known that metallic salts of casein such as calcium cascinate and magnesium caseinate are highly insoluble and are formed very rapidly whenever casein is mixed with calcium or magnesium- Sodium metaphosphate reduces considerably. the concentration of such metal ions when it is mixed with them in solution. It is believed that the action of the sodium metaphosphate is to sequester or look up the calcium or magnesium in a but extremely slightly ionized condition in a soluble sodiumcalcium-metaphosphate complex molecule or the corresponding sodium magnesium metaphos phate complex molecule. The action of the metaphosphate prevents the rapid formation of the insoluble casein salts of calcium and magnesium, thus keeping the casein mixture for comparatively lengthy periods of time from getting so thick that it cannot be worked easily.

There is, however, another effect of the sodium metaphosphate which appears to be entirely apart from its action upon calcium and magnesium. This efl'ect is the solubilizing action of the sodium metaphosphate on casein and is illustrated by the following example.

Example I Two mixtures were made, the first containing one gram of casein in mls. of a 2% solution of sodium chloride and the second containing one gram of casein in a 2% solution of sodium metaphosphate. The. pH values of each of the mixtures was the same, about 5.8. Upon shaking each solution the one containing sodium metaphosphate yielded a stable foam, whereas the one containing sodium chloride did not, thus demonstrating that the sodium metaphosphate solution had a specific solubilizing effect upon the casein which could not be attributed either to salt concentration or pH, which were the same in both cases. Each solution was then filtered. To 25 mls. of each of the filtrates were added 25 mls. of a special oil known to the trade as Olive Elaine, this oil being a purified oleic acid and the mixtures were shaken. The sodium chloride-casein-oil mixture formed no emulsion whatever. Immediate separation of the original light yellow-colored oil took place. In the case of the sodium metaphosphate-caseinoil mixture an emulsion was formed which, after a few moments, separated into two layers, neither one of which looked like the layers of the sodium chloride-casein-oil mixture. The upper layer of the sodium metaphosphatecasein-oil mixture'was very white and opaque and was probably a concentrated water and oil emulsion. Although the lower layer of this mixture was not as opalescent as the upper layer, it was considerably more opalescent than the lower layer in the sodium chloride-casein-oil mixture. In the case of the sodium chloridecasein-oil mixture the upper layer was, as far as could be ascertained visually, pure oil with no sign of an emulsion.

Since in making the two mixtures pure salts were used, the pH of the mixtures were very close to that of distilled water, and the emulsion obtained with the metaphosphate-casein-oil mixture was undoubtedly due to a specific solubilizing effect of the sodium metaphosphate upon the casein. After a period of 24 hours the appearance of the metaphosphate-casein-oil emulsion was the same. In other words, a stable emulsion had been formed and there was no further separation in 24 hours.

Example II mls. of 10% sodium chloride solution and the mixture shaken and then filtered. To 25 mls. of this filtrate were added 25 mls. of the abovementioned Olive Elaine, the mixture was shaken vigorously, and 25 mls. of the mixture was put into a 25 ml. graduate. casein-oil mixture broke immediately into two layers of which the volume of the upper creamy layer was 16 mls. and the lower water layer 9 mls. In the case of the sodium metaphosphatecasein-oil mixture there was no breaking up of the emulsion. In six hours the sodium chloride- The sodium chloridecasein-oil emulsion had broken down completely 76 into 13 mls. of oil and 12 mls. of water, while in the same length of time the sodium metaphosphate-casein-oil mixture contained 16 mls. of a creamy emulsion and 8 /2 mls. of water. Twenty-four hours later the sodium chloridecasein-oil mixture was clearly divided into. the original mixture of 50% oil and 50% water, while the sodium metaphosphate-casein-oil mixture divided into l6 parts of a creamy emulsion and 9 parts of water. About 5 hours after this observation it was noted that the creamy emulsion of the sodium metaphosphate-casein-oil mixture had solidified.

This example shows definitely that sodium 'metaphosphate has some peculiar effect upon casein which cannot be attributed purely to salt effect. The mixture of casein and sodium chloride prepared as above described had very little power toward the emulsiflcation of the oil. The mixture of sodium metaphosphate and casein, on the other hand, made a very stable emulsion; in fact, a solid emulsion under exactly the same conditions. Since the mixture of casein and sodium chloride did not emulsify the oil, and since it is known that sodium metaphosphate by itself does not have pronounced emulsifying properties on oil, it follows that there can be only one explanation of the very stable emulsion which the sodium metaphosphate and casein formed with the oil, and that explanation is that the sodium metaphosphate and casein mixture exhibits entirely different properties when used for emulsifying oil or other oleaginous material than either the sodium metaphosphate or the casein exhibit separately. It is believed that due to the solubilizing eifect of the sodium metaphosphate on the casein a solution is formed which acts as an emulsifying agent for the oil.

Example III In this example four mixtures were made as follows. The first sample or mixture contained 100 grams of casein. The second mixture contained 100 grams of casein and 25 grams of sodium chloride. The-third mixture contained 100 grams of casein and 25 grams of sodium metaphosphate. The fourth mixture contained 100 grams of casein and 25 grams of fadjusted sodium metaphosphate. The adjusted sodium metaphosphatereferred to in mixture four consisted of sodium metaphosphate containing about 10% sodium pyrophosphate, about 4% of soda ash and 2% of sodium bicarbonate, these last named ingredients being used for the purpose of adjusting or increasing slightly the al- .kalinity of the sodium metaphosphate.

To each of the four mixtures were added 500 mls. of water, the water being added in five portions of 100 mls. each. Each of the mixtures was stirred vigorously and let stand for one-half hour in bottles of the same diameter and height.

At the end of that time the percentage of settling' out of the casein was calculated by dividing the height of the clear top liquor by the total height of the mixture. The results were as follows: Neither mixture three nor mixture four showed any settling out of the casein whatsoever. These were the two mixtures containing, respectively, casein and sodium metaphosphate, and casein and adjusted" sodium metaphosphate. Mixture two, which contained casein and sodium chloride, showed 22% settling; and mixture one, which consisted of casein only and water showed 28% of settling.

short.

Although there was no settling in either ofthe mixtures three or four, mixture four, containing the adjusted" sodium metaphosphate, was very viscous and stiff. This wasundoubtedly due to the factthat the pH of this particular mixture was a little higher than the pH of the other mixtures, which were about 5.5. Mixture three,

containing the ordinary or unadjusted? sodium ,Case'in paints My invention is applicable to the production of casein paints. Casein paints as now generally produced are made by mixing casein and an alkali such, for example, as lime, together with whiting, clay, or other paint pigments, and a preservative such as borax. In general, the amount of casein used is approximatelyv 15%, the amount of lime, if that is the alkali which is employed, is about 15%, and the remainder of the composition is made up by the other paint pigments, fillers and coloring pigments. It will be understood that these percentages vary greatly according to the particular type of paint. 'The working life of such casein paints is extremely Calcium caseinate is formed almost immediately upon mixing with water and the resulting paint becomes so. thick that it cannot I be used.

I have found that by adding sodium metaphosphate to casein paint in approximately the same proportions as were mentioned in connection with the preparation of casein paper coatis that it enables one to add water at any time during the working life of the paint to allow for such evaporation as has taken place. This is a decided advantage as it is recognized that casein paints heretofore known cannot be diluted after they .have once been prepared. The amount of sodium metaphosphate or other alkali-metal metaphosphate added depends largely upon .the length of working life desired for the paint. The amount of sodium metaphosphate added may vary from a very small quantity which will not have a pronounced effect upon the length of the working life of the paint to a considerable amount which will have a very marked eilectthereon.

Casein glues My invention is applicable also to the production of casein glues and other adhesives. The excellent properties of casein glues have been known for a long time. Casein glues containing lime have been used for many years in the preparation of water-proof joints since calcium caseinate is a highly insoluble salt. .A serious failing of this type of glue is, however, that its' Another advantage in theversely the adhesive properties of the glue. A glue may be prepared, for example, as follows:

Eicample IV v Example V In this example the same mixture as given in Example IV was prepared and there was added to that mixture, with stirring, copper sulphate in the amount of five grams dissolved in 50 mls. of water. The resulting glue had a working life of about 80 hours. The copper sulphate was added for the purpose of increasing the water resistance of the glue. Heavy metal salts of casein .such as copper caseinate are very insoluble and increase markedly the water-proof properties of the glue. Other heavy metal salts such as soluble salts of zinc, lead, tin, etc., may be used in place of the copper sulphate if desired. Heretofore after the addition of such a salt to .a casein glue, it was necessary to use the glue up i'mmediatelysince hardening took place very rapidly. By using sodium metaphosphate I have been able to make casein glues having very high resistance to water and with a working life 0175 to 100 hours. The working life ofthe glue depends largely upon the amount of alkali-metal metaphosphate added.

The alkali-metal metaphosphate employed in accordance with the present invention in the production of casein products is effective in improving'not only such products as contain lime and magnesium, but also such products as do not contain them. The alkali-metal metaphosphate is particularly effective in casein products containing lime or magnesium for the reason, it is believed, that in addition to the specific solubilizing efiect of the metaphosphate on the casein, there is the additional effect of the metaphosphate on the lime or magnesium by which they are sequestered'or locked up in a but extremely slightly ionized condition in a soluble sodium calcium metaphosphate complex molecule or a soluble sodium magnesium metaphosphatecomplex molecule.

Other alkalies than lime may be used as the solubilizing agent for the casein whether the product is to be used as a coating or sizing agent, paint. glue or other composition. For example, caustic soda or other alkali may be used in place of lime where heavy metal salts are employed in the manufacture of casein glue.

I have described in detail, certain preferred procedures and have given certain specific examples. It will be understood, however, that the invention is not limited to the examples or procedure described, but may be otherwise embodied or practiced within the scope of the following claims.

.I claim:

l. A plastic setting mass adapted for use as coating and sizing compositions, paints, glues and the like, containing casein, an alkaline earth metal, and an alkali-metal metaphosphate.

2. A pastic setting mass adapted for use as coating and sizing compositions, paints, glues and the like, containing casein, an alkaline earth metal, an alkali-metal metaphosphate and mineral matter.

3. A plastic setting mass adapted for use as coating and sizing compositions, paints, glues and the like, containing casein, lime, an alkalimetal metaphosphate and mineral matter.

4. The process of emulsifying casein-water- 'oleaginous mixtures, which comprises mixing therewith an alkali-metal metaphosphate.

5. The process of emulsifying caseinwateroleaginous mixtures, which comprises mixing therewith sodium metaphosphate.

6. A plastic setting mass adapted for use as coating and sizing compositions, paints, glues and the like containing casein, a solubilizing agent for casein, and an alkali-metal metaphos- CHARLES SCHWARTZ.