US2235798A - Grease-proofing paper - Google Patents

Description

Patented Mar. 18, 1941 UNITED STATES PATENT OFFICE GREASE-PROOFING PAPER ration of Michigan No Drawing. Application May 19, 1939,

Serial No. 274,652

2 Claims. (01. 91-68) This invention relates to an improved grease prooied paper and to a method of producing the same.

It is an object of this invention to produce a 5 coated paper having a high resistance to grease,

fatty materials and the like.

It is a further object of'the invention to make a coated grease-proofed paper which retains its grease-proofing qualities on creasing.

10 Another object is the preparation of a tasteless, odorless paper suitable for the wrapp g of fatty foodstufis.

A further object is the preparation of a greaseproofed paper adaptable for wrapping frozen lo foodstufis.

Other objects are disclosed in the following complete description or our invention.

We attain these objects by coating a wrapping paper with a substantially continuous thin 2 layer comprising a water-soluble cellulose ether.

This layer may be applied to the wrapping paper trom an aqueous solution of the cellulose ether composition by means of a doctor blade, roller, or extrusion hopper in the ways well 25 known to the paper coating art. Alternatively,

we may bond a moistened preformed fi-lm comprising a water-soluble cellulose ether to a paper sheet.

We may use a solution of any water-soluble cellulose ether, but prefer to use a type of ether whose per cent aqueous solution has a viscosity above 70 centipoises because it can form a thinner unbroken, co-extensive film than does a low-- or viscosity type. Examples of suitable watersoluble others are methyl cellulose, sodium cellulose glyooll-ate, and hydroxy ethyl cellulose. With them may be incorporated water-soluble plasticizers, such as sorbitol, ethyl sorbitol, glyoerlne, 40 and the like, also pigments or other adjuvants,

101' they may be used in a completely unmodif ed 'Iorm.

The solution may be applied to any kind of wrapping paper, but we prefer to coat smooth 45 surfaced papers as a. continuous film is formed on such papers in lower thicknesses, and consequently with expenditure of less coating solution, than on uneven or rough surfaced papers. We have found glessine pap r. parchment paper, 50 market paper, and like smooth surfaced papers suitable for use in the practice of our invention. Some or these, in the uncoated form, possess a modemte degree of grease-prooiness and are commonly used img greasy foodstuiis, but 55 the grease-proofing properties of each of them are greatly enhanced by the treatment of the present invention.

Under favorable circmnstances, that is, when using a high viscosity type, water-soluble cellu lose ether and when applying it to smooth sur 5 faced paper, such as glassine, a continuous film of the ether may be of the order of only 0.0001 inch thick. 0n the other hand, when using a low viscosity type ether, or a rough surfaced paper, it may be necessary to apply a coating of thickness averaging about 0.002 inch or more in order that it be continuous.

All these coatings, including the thicker ones, are tough and flexible, remain unbroken after creasing and handling and consequently retain their grease impermeability after such treatment. Further, the coatings remain flexible on subjection to low temperatures, for example, those in the neighborhood of -40 C. The coated papers of this invention may therefore be used both for wrapping foodstuffs that are to be frozen, and for those which are handled at ordinary temperatures.

The new coated papers, for use in packaging foods or other articles which are both greasy and water wet, may be molsture-proofed with wax, or with any of the usual moisture-proofing compositions including wax-resin mixtures, and wax-resin cellulose derivative mixture. Again, the new coated papers may be bonded to transparent foil or they may be coated with a lacquer to give a wrappi g material having a moderate degree of moisture impermeability combined with attractive appearance and grease-proofness.

The following examples illustrate the practice of this invention:

Example 1 A sample of a paper known as "Market paper of basis weight of pounds per ream of 3000 40 square feet was coated with a 12 per cent aqueous solution of 80 centipoise type methyl cellulose using a doctor blade. Th coating, after dryring, had an average thickness of 0.0005 inch. The coated paper was tested in comparison with an uncoated sample of the market paper by a rapid test for grease-proofness as follows:

The sample to be tested was cut into four pieces 2% inches square and each was folded to form a box with inch high sides and 1 inch square base. The boxes were heldin shape by placing them in suitable supports. A piece of white writing paper was placed beneath each box and one cubic centimeter of peanut oil, coconut oil, corn oil and molten hydrogenated stearoleine was added respectively to the four boxes which were then placed in an oven at C. The white paper underneath each box was inspected peri odically for occurrence of a grease spot. When this appeared the sample under test was considered to have failed and the time taken for this failure was recorded. Grease resistance of a sample was reported as the average time of penetration for peanut oil, coconut oil, corn oil, and hydrogenated stearoleine.

The samples had grease resistance as follows:

Grease sample resistance Hours Unooated market paper 1 Market paper coated with 0.0005 inch methyl cellulose. 44

Example 2 Grease sample resistance Hours Methyl cellulose coated glassme paper 196 Uncoated glaasme paper 12 As stated, the invention has a particular application in the wrapping of greasy foodstuffs. Examples of such materials are butter, nut meats, potato chips, cheese, baked goods, meat and ice cream. Our product is also useful in the packaging of other classes of goods which tend to exude oily bodies on storage and which stain common wrapping papers. Among these are soaps, candles, and a number of pharmaceutical products.

We claim:

1. The method of preventing greasy and oily exudations from paper packages of products tending to give such exudates through paper, which comprises enclosing such products in paper bearing on at least one face thereof a substantially continuous superficial coating of a watersoluble cellulose ether of a type whose 5 per cent solution in water has a viscosity above 70 centipoises, the said coating being tough and flexible, even at sub-zero temperatures.

2. The method of preventing greasy and oily exudations from paper packages of products tending to give such exudates through paper, which comprises enclosing such products in paper bearing on at least one face thereof a substantially continuous superficial coating of a watersoluble methyl cellulose of a type whose 5 per cent solution in water has a viscosity above 70 centipoises, the said coating being tough and flexible, even at sub-zero temperatures.

WILLIAM R. COLLINGS. FLOYD C. PETERSON. HAROLD C. KELLY.