Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/50—Proteins

Definitions

• This invention relates to proteinaceous adhesives and more particularly to a process for peptizing such adhesives in an acid medium and to a mineral filled coating composition employing the same as a binder precipitated therein in the free state.
• Another problem in the art of coating relates more specifically to the disadvantages of calendering.
• the paper In order to accomplish any appreciable degree of smoothing of conventional coating surfaces by calendering without at the same time crushing the body stock, the paper must be dried in order to give the fibers in the body stock enough strength to withstand the pressure of the calender roll. In general, it is adequate to air-dry the paper (about 4% moisture) for this purpose, and when this is done a calender roll pressure of approximately 2,000 pounds per linear inch will smooth the coating surface adequately without crushing the body stock.
• calendering due to the extreme pressure required with conventional coating materials, calendering has previously always lowered the bulk, brightness and opacity of the paper, and otherwise given the paper a somewhat dingy appearance.
• I formulate a coating composition comprising conventional coating components in combination with a proteinaceous adhesive.
• casein or casein-like materials such as soy-bean protein
• a salt such as ammonium nitrate, sodium nitrate, or nitrates of other alkali metals.
• concentration of casein-to-water must be quite high; i.e. 2035%.
• concentration of salt must be comparatively high; i.e. 4l0%.
• casein is peptized or appears to dissolve in approximately 20 minutes.
• a small amount (below 10% based on casein) of water-soluble tallow-based soap assists the peptizing process and permits some lowering of these percentages.
• casein so peptized will help to form a basis for understanding the nature of the adhesive. If it is allowed to cool to room temperature, it rapidly gels to a thick mass. Reheating the mass, however, returns the casein to its former liquid state. On the other hand, if the liquid, peptized casein, at for instance F., is poured into an excess of water (no matter whether the water is hot or cold) instead of forming a thinner solution of peptized casein, the casein immediately precipitates and forms a conglomerate ropelike mass. Likewise if water is poured into such casein without agitation, the same sort of precipitation takes place, and even with agitation, precipitation seems to occur. The ropy cords are not formed, but the solution turns milky in appearance. In addition, since casein hy-;
• the resulting combination of salt peptized casein and clay has a number of interesting properties. In the first place, it has a surprisingly low viscosity which makes it an excellent binder for coatings employed with an air-knife smoothing mechanism. In addition, the Water retention of the fluidcoating composition prior to coating is very low and the rate of water absorption of the finished dried coating is high. Another characteristic of the comtogether they appear to be far more malleable than ordi- When this is done,.
• the coating may be smoothed by calender rolls without at the same time substantially reducing the bulk, brightness and/or capacity of the coated sheet.
• an extremely important characteristic relates to cast coating.
• the casein in my coating combination seems to be largely precipitated and, therefore, it is substantially water insoluble.
• water insoluble it is still in a condition which permits drum finishing by the cast coating process while at the same time strongly resistingany tendency to wash off when passed through a re-wetting bath at the casting nip during the casting operation.
• the foregoing mixture had a-pH- of about 5.0. After agitating the same for about 20 minutes during whichthe temperature gradually declined to about 140 F., the
• casein is substantially peptized.
• the salt employed to peptize the casein does not combine with-the casein to form a caseinate as do the alkalisnormally employed to disperse casein.
• Example No. 1 the same ingredients as Example No. 1 were employed, except that both the soap and the dicyandiamide were omitted. The result of this was to make it more diflicult to peptize the casein, but with continuous vigorous agitation, the casein did peptize in about 30 minutes.
• Example No-1 the same procedures as set' forth for Example No-1 were followed, except that the proportion of soap wasincreased to: approximately 1% This mix-' ture peptized slightly quicker, and after being combined with the clay slurry, it resulted in a coating which was particularly well suited for hot calendering under light pressure.
• casein Australian hydrochloric acid precipitated
• the salt should be a stable, soluble, neutral or acidic salt of an alkali metal or ammonium having a monovalent cation and a monovalent anion.
• the nitrates of ammonium and sodium are preferred.
• the pH of the salts which perform satisfactorily in our process have in a 5% aqueous solution a pH of 4.5 to 7.0. If salts which are more acidic are employed, they fail to peptize the casein and if they are more basic, they tend to yield a caseinate similar to the conventional alkaline casein dispersants.
• salt peptizing does not involve a chemical change of forming a caseinarte as do the conventional processes involving the use of bases to disperse the adhesive.
• a process for preparing a coating composition that yields a maleable coating on a paper web comprising: preparing a peptized aqueous solution of a protein selected from the group consisting of casein and soy protein by admixing at a temperature in the range of 140 to 212 F.
• said protein with a soluble salt of a monovalent anion and a cation selected from the group consisting of the alkali metal ions and the ammonium ion while maintaining the pH of the admixture between the iso-electro point of said protein and 7, said soluble salt in a 5 percent aqueous solution having a pH in the range of 4.5 to 7.0, said protein being in the range of 20 to 35 percent of said solution and said soluble salt being in the range of 4 to 10 percent thereof, thereafter forming a stiff slurry by admixing said aqueous solution with a cool slurry 6 of a paper-coating-grade mineral pigment, the amount of said slurry being suflicient to dilute the concentration of said salt in the resulting mixture to below about 4 percent where it no longer peptizes said protein, and agitating said stiff slurry to a homogeneous mixture of substantially lower viscosity.

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Priority Applications (6)

Applications Claiming Priority (1)

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Cited By (7)

Citations (8)

• 0
  • NL NL126853D patent/NL126853C/xx active
  • NL NL257662D patent/NL257662A/xx unknown
• 1959
  • 1959-11-09 US US851541A patent/US3081182A/en not_active Expired - Lifetime
• 1960
  • 1960-10-24 GB GB36439/60A patent/GB966225A/en not_active Expired
  • 1960-10-29 DE DEW28844A patent/DE1298406B/de active Pending
  • 1960-11-08 FR FR843372A patent/FR1273574A/fr not_active Expired

Patent Citations (8)

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