US2364792A - Production of zein coating - Google Patents

Description

Patented Dec. 12,1944

PRODUCTION OF ZEIN CQATING Albert L. James, 'Ienafly, N. 1., as'slgnor to Corn- Products Refining Company, New York, N. Y., a

corporation of New Jersey No Drawing. Application January Serial No. 429,136

6 Claims. (01. roe-15a) This invention relates to the production of zein coatings and the like, and the primary objects of the invention are to increase the water resistance of such coatings and also to shorten the curing time, that is, the time required for bringing the coating to a state in which it is relatively hard and water resistant.

A specific object of the invention is to provide an aqueous zein dispersion which may be used, as an adhesive, in the place of casein adhesives. in the clay coating of paper for lithographing purposes, whereby the coating operation is simplified and the cost of the same reduced, the-water resistance of the coating improved and, more particularly, the curing time is very substantially shortened. The shortened curing time is important in clay coating for lithography as it is often desirable to lithograph paper within a short time after it has been coated; and, usually, the

coated paper is wetted with water before being subjected to the lithographing procedure, and, therefore, must be water-resistant at that time.

The following specific examples give instances of the reduction to practice of the invention, in certain preferred embodiments. It will be understood, however, that the specific examples are purely typical and illustrative. The invention is notlimited tothe particular operating data given therein. It is the intention to cover allequivalents and also all modifications within the scope of the hereto appended claims. In the examples, ranges are given in parentheses. These ranges are practical, not critical, unless particularly so specified. In the examples the proportions are given in parts by weight, unless otherwise specified.

Example 1. 382 parts of zein (commercial zein containing the usual amount of water) is mixed with 1400 parts of water (1300 or over). To this is added first '75 parts (25 to 150 parts) of 85% sulfonated castor oil, containing, that is, of water, and then 215 parts (150 to 350 parts) of water. The paper is coated with this clay slurry and the sheets airdried or dried at a suitable elevated temperature such as 150" F. This process will give a tenacious coating which'wlll become in a high degree, and almost immediately, V

water resistant.

Example 2.-The following ingredients are mixed together according to the procedures indicated in Example 1, viz.: zein 1'? parts, water 60 parts parts to 60 parts), sulfonated talloil containing about 37% of water 3.4 parts (2 parts to 10 parts), caustic potash 0.8 part (0.51-part to 1.2 parts), lead acetate 0.85 part (0.35 part to 3.0 parts), clay 100 parts (50 parts to 200 parts).

In place of lead acetate it is possible to use any water soluble salt of a weak acid, such as acetic or formic acid. Examples are the acecaustic soda.

,tates and formates of aluminum, barium, calcium, magnesium, tin, zinc and copper. Metal salts of strong acids should not be used, since they tend to precipitate the rein to such an extent that it is not readily redissolved by the excess of It is the lead acetate or its equivalent which appears to give the coating the capacity to develop a. high degree ofwater resistance in a short period of time.

In the zein dispersion of the present invention, the primary dispersing agent is caustic soda;

The -'sulionated oil appears to be a secondary zein dispersing agent which brings about a more thorough dispersion in the water of the alkali disi solved zein. Furthermore, alkali solutions 01' zein are unstable tending to jell within a short. time. The sulionated oil acts to stabilize the alkali-zein solution or dispersion until such time I as it may be used.

of a caustic soda solution consisting of 15 parts of sodium hydroxide dissolved in 200 parts of water. At this stage the zein is completely dissolved, or at least forms a dispersion which closely approximates a solution. dispersion is added, slowly and with rapid agitation, a lead acetate solution made up of 20 parts 61 lead acetate (5to'40 parts) and 200 parts 0! water.

The dispersion or solution made as above and To this solution or.

consisting of approximately-2092 parts. is mixed with2250 parts (1800 114500 partsloi' clay, or

it! equivalent, and parts (1300 #05000 M)" Any sulionated oil which is capable of dispersing the zein and which is of such character that it win not be precipitated by the lead acehate in the presence of the excess'of caustic soda, may be used in place of the sulfonated castor oil or talloil which latter, however, are preferred, especially the sulfonated talloil. In fact, any of the zein dispersing agents disclosed in application of Albert Luther James, Serial No. 351,214, filed August 3, 1940, may be used in place of the ,sulionated oils provided such zein dispersants have the property of not being precipitated by the presence ofthe lead acetate, or its equivalent. This excludes rosin size for the reason that rosin size, being a'sodium soap or rosin, interacts with a metal salt, such as lead acetate, to iorm'a metal .rosin soap, for example, lead rosin soap; which is highly insoluble'and would, therefore, bring: about ml; precipitation or thefrom the solution. Q For similar reasons soaps of a the fatty acids cannot be used eflectively as secondary zein dispersants in accordance with the present invention. p

In place of caustic soda (sodium hydroxide) any alkali may be used which is capable of dispersing zein in water. Examples arev potassium hydroxide, and compounds of ammonium hydroxide with caustic aikalies, and trisodium phosfrom aqueous zeinv dispersions in which an'alkali and a sulfonatedvege'table oil are used as dispersing agents: the improvement which comprises incorporating in the dispersion lead acetate in. or-

der to increase the water resistance of the coating and reduce the time required for bringing the coating to a water-resistant state.

2. In the formation of coatings from aqueous zein dispersions in which an alkali and a sulfonated vegetable oil .are used as dispersing agents: the improvement which comprises incor- V porating in the dispersion a substance to increasethe water resistance of the coating and reduce the curing time thereof, of the group of substances consisting'of the acetates and formates of aluminum, barium; calcium. magnesium, tin. zinc. copper and lead.

.3. In the formation of coatings from aqueous zein dispersions in which an alkali and; a sul- 5 fonatedv vegetable oil are used as dispersing agents: the improvement which comprises incur-- porating in the dispersion a soluble salt of a weak acid to, increase the water resistance of the coating and reduce the time required forbringing 10 the coating to a water-resistant state.

4. A coating composition which comprises: zein dispersed in water by ltd-alkali and'sui- I fonated talloil, said dispersion containing also 4 lead acetate to enablea coating. produced from 5 said composition to develop a high degree of water resistance in' a short period of time.

5. A coating composition which comprises zein dispersed in water by analkali and a sulfonated vegetable oil, said dispersion containing also. to

20 increase the water resistance of the coating formed from such composition and reduce: the v curing time thereof, a substance selected from the group of substances consisting of the acetates and formates of aluminum; barium, calcium,

25 magnesium, tin', zinc, copper and lead. a

6. A coating composition which comprises zein dispersed in water by an alkali and a sulfonated vegetable oil said dispersion containing also, to

increase thewater resistance of the coating so formed from such composition and reduce the curing time thereof, a soluble salt of a weak acid. I

Y L; JAMES.