US2282375A - Wax sealing composition - Google Patents

Description

Patented May 12, 1942 WAX SEALING COMPOSITION Frederick Warde Padgett, Jackson Heights, N. 2., assignor to Moore & Munger, Piainfleld, N. J., a firm composed of George T. Kea'ting, Edward P. Snyder, and Murray Rushmore No Drawing.

Claims.

This invention relates to a new and improved waxed paper, to be used for wrapping foods and other products.

One of the objects of the invention is to coat or impregnate paper with a wax of improved sealing strength.

Application October 27, 1939, Serial N0. 301,615

Another object of the invention is to provide paper which has been coated or impregnated with improved petroleum wax.

Other objects of my invention will be set to: th

-in the following description which-illustrates preferred embodiments thereof, it being understood that the above statements of the objects of my invention is intended generally to ,explain the same without limiting it in any manner.

Petroleum wax has a high resistance to water vapor, and paper which has been coated or impregnated with such wax, is highly effective in excluding or retaining moisture from or in the product being wrapped. A good example is waxed bread wrapper, consisting of a sulphite sheet of 20 to 25 lbs. weight to the ream which has been waxed up to 33 to 37 lbs. to the ream. In the manufacture, part of the. wax soaks into the paper and part remains on the surface. Hence this sheet is typical. of what is known as the'wet waxed sheet and it possesses self-sealing properties under the application of heat which melts or softens the wax, and subsequent cooling which solidifies the wax.

The self-sealing is carried out in well-known continuous machines, when the paper is used for wrapping loaves of bread.

The sealing effectiveness, even for the petrole-- um waxes having a tensile strength of four hundred pounds to the square inch, never has been entirely satisfactory, especially for such paper as is used for wrapping soft products. Hence it is important that the sealing strength be increased above that of the fully refined petroleum wax or waxes.

I have found that the incorporation of small amounts of selected I. G." waxes and other .hard, polar substances into the usual fully refined petroleum wax or waxes increases both the tensile and sealing strength, but the latter in much greater percentage than the former. In addition to this improvement in self-sealing, the tendency of the waxed sheets to .stick together, known as blocking is decreased.

The "I. G." wax which I- prefer to use has a melting point of 176181 F., an acid value of 15-20, an ester value of -155, and a light yellow color. It contains only about'8-10% of unsaponifiable matter. It is readily saponified by dissolving soap and either caustic soda or caustic potash jointly in water, and adding the melted "I. G. wax to the boiling solution, with vigorous stirring. Said I. G. wax can be melted in a solution of soap and caustic alkali in water, and additional boiling water can be added slowly. Smooth emulsions can thus be formed. The method of making the I. G. types of wax is disclosed in British Patent No. 368,425. The I. G. waxes which I prefer 'to use are known in the market as I. G. Wax E and I. G. Wax B and they are described in Bulletin G-47-1 issued by General- Dyestufi Corporation of 230 5th Avenue, New York, N. Y. In said Bulletin the E wax is stated to have an acid value of 15-20, and an ester value of 140-155; the B wax is stated to have an acid value of 10-60 and an ester value of 125-150.

Other I. G. waxes are not useful for increasing the sealing power of the wax composition. Some I. G. waxes are unsuitable because they cannot be incorporated uniformly into petroleum wax, while the preferred I. G. waxes can be thus uniformly incorporated. When the improved composition is melted and rapidly cooled in the operation of coating the paper, the preferred "1. G. waxes do not separate from the petroleum wax or waxes. The composition is either a true and uniform and stable solution of the I. G. wax in the petroleum wax, or auniform and stable dispersion. The I. G. Wax

E and I. G. Wax B when used in'percentage's less than 1%, impart a slight odor to the wax, but the odor is not detectable in the final waxed paper. The I. G. Wax S can also be incorporated uniformly into paraffin wax so as to form a heat-stable solution or dispersion which is uniform, but it has too much odor for some purposes. Said 8" wax has a melting point of -183 F., an acid value of 142-152, an ester value of 25-35, and a very pale yellow color.

These products are used preferably in combination with the fully-refined petroleum wax.

The I. G. waxes which may be used for improved self-sealing, and for decreasing blocking. in addition to I. G. Wax E and I. G. Wax B, are I. G. Wax S (melting-point 180-183 F.), I. G. Wax V (melting-point 122 F.). However, the type which is preferred is the I. G. Wax

E- The B wax has a melting point of 167 F.-

Other I. G. waxes which have been found effective in increasing sealing strength of paraffin wax are I. G. Wax F. P. and I. G. Wax

K. P. These products have melting points of 175-180 F., acid numbers to 35, ester numbers 100 to 125, saponiiication numbers 130-155, unsaponiflable matter 10- 14%, specific gravities 1.0 to 1.03 at 70 F.

In incorporating the I. G-" wax with the usual petroleum wax, the latter is melted in a tank with steam heat to a temperature of 150 to 180 F. The I. G." wax is melted in a separate container and it is added slowly to the molten petroleum wax while the latter is stirred'mechanically or while it is stirred by being blown with air. .The I. G." wax goes into uniform solution or into such a state of uniform dispersion that it does not settle out upon standing and solidifying. The mixture is maintained molten at 150 F.-180 F. while said solution or dispersion is being made. Petroleum wax which is used forwaxing paper and the like has a range, of melting point between 120, F. and 180 F. The difference in melting point depends upon the proccess of manufacture and the particular raw material which is used. It is well known that petroleum wax is made commercially from different fractions of crude petroleum. It is also well known in the trade that the petroleum wax which is used for waxing bread wrappers has a range of melting point between 125 F. and 140 F- The addition of a small percentage of I. G." wax, not more than about 2%, to the petroleum wax, does not materially increase the melting point of the petroleum wax.

Specific examples may be given as follows: The petroleum wax used was a fully refined product having a melting point of 132 F. (English) and a tensile strength of 252 pounds to the square inch at 70F. About 0.5% I. G. Wax E dissolved in the petroleum wax, increased the tensile strength to 320 pounds, or about 27%, while the sealing strength, as tested by the methad to be described below, increased 68%. About 0.3% of the I. G. Wax E" increased the sealing strength 39%, while 1.0% of the I. G. Wax E increased the sealing strength 92%. These pro- "portions of the I. G. Wax E" are by weight. The percentage of I. G. wax should be small,

not exceeding substantially 2.0%.

The method of making the sealing strength tests were as follows: Sections of a uniform sulphite sheet were waxed respectively with the petroleum wax alone and with the various mixtures above stated, so that each section had the same amount of wax per unit of area. Then strips of said sections one inch in width were doubled and each doubled strip was pressed against a beaker containing hot water at a temperature of 190 F. At this temperature, the coating of each doubled strip melted, and the two halves of each strip adhered to each other by means of the coating. Then the doubled strips were removed from the surface of the beaker and permitted to cool in the air. After ageing at room temperature. of '77 F. for two hours, the doubled strips were tested as follows: The ends of each strip were separated for an inch, one of the separated ends was then'inserted into a clamp and the other separated end was attached to a thread which extended horizontally over a metal bar and then vertically to a small cup to which the thread was attached. Bird shot was then poured into the cup slowly until the connected parts of the strip started to separate or peel apart at a slow rate. The weight of the cup and its contents which was necessary to separate the sealed parts of the strips, was recorded as the sealing strength.

Another example of the effect of the I. G. Wax E on the sealing strength of petroleum wax is as follows: The petroleum wax had a tensile strength of 377 pounds to the square inch at 70 F., and a sealing strength of 11.4 gms. When 0.5% of I. G. Wax E" was incorporated in solution with the petroleum wax, the tensile strength was 460 pounds, an increase of 22%, while the sealing strength was 19 gms., an increase of 66%.

In a wax paper plant, paper was waxed on the large machines, first using straight petroleum wax, then using a mixture consisting of 99.5% petroleum wax and 0.5% I. G. Wax E." The rolls of paper were then taken to a bakery where loaves of bread were wrapped and sealed on the commercial machines, using both the paper waxed with the straight petroleum wax and that waxed with said mixture of petroleum wax and I. G. Wax E." Comparing the two products, it was plainly evident that the mixture containing the I. G. Wax E was muchstronger than the straight wax.

A'mi'xture of 0.3% wax E," 0.5% amorphous petroleum wax (whose melting point was 160 F.-165 F. by the drop method) and of, fully refined paraffin wax (petroleum wax) having a 'melting point of 132 F. by the English method,

' composition in the proportion of 0.1% to 10% Whenever I specify a minimum proportion as substantially, I can use less or more than said minimum proportion. a

In some cases it is desirable to soften the fully refined wax for special sheets, in which case-the incorporation of 0.1% to 10% amorphous wax has the desired effect. i

Instead of using amorphous petroleum wax or amorphous paraflin'wax for any of the purposes specified, I can use from 0.1% to 5% of the product known as Vistanex" instead of using from 0.1% to 10% of said amorphous wax. Said *Vistanex is described in certain patents and publications as follows:

French Patent No. 740,407; U. S. Patent No. 2,054,115; Rubber Age (New York edition) vol. 41, p. 102 (1937). It is prepared by polymerizing iso-olefines, and particularly isobutylene. The molecular weight of Vistanex variesQdepending upon the method of preparation.

The non-amorphous paraflin wax or petroleum wax is melted and kept at a temperature of about 200 F., while the Vistanex" is added in small pieces with vigorous stirring, until the Vistanex has been uniformly dissolved in or dispersed in the molten wax. The composition is then allowed to cool and solidify. It is applied-in the molten condition to the paper, at a temperature of -200 F. It is well known practice to maintain the temperature of the wax composition above its minimum melting point, when the paper is coated. This is done to render the composition more fluid and to increase the penetration of the composition into the paper. I therefore use a minimum temperature of 150 F., even though the composition may have a lower melting point than 150 F. This is well known com-' montanic acid with alcohols. These alcohols may be higher alcohols, such as montanyl alcohol. However, said British Patent No. 368,425 discloses the use of lower alcohols, such as anhydrous ethyl alcohol. They can be prepared so as to simulate beeswax and other waxes in certain physical properties. They are described in vol. 2, pp. 690 and 691 of the Supplement to Thorpes Dictionary of Applied Chemistry, published in 1935, (which refers to various technical publications which describe said I. G. waxes), and also in vol. 1, p. 668 of said supplement.

The glycerol ester of montan wax or of montanic acid also is effective in increasing the sealing strength of ordinary wax when present in small percentages 0.1% to 2.0%.

When I refer to petroleum wax, I include said material if derived from sources other than petreloum, and analogous waxes.

Likewise, said Britsh Patent No. 368,425 and the other patents referred to therein, disclose products made from carnauba wax and other waxes, which are equivalent to those made from montan wax. Hence, whenever I refer to montan wax in the claims, I do not exclude equivalent products.

The improved self-sealing coating is substantially free from liquid ingredients, so that it is self-sealing when heated and subsequently cooled, and its ingredients do not separate during th self-sealing.

Besides the esters of montan wax or montanic acid as described above, other polar substances, such as commercial montanic acid itself, carnauba wax and candelilla wax, are effective in increasing sealing strength when present in small percentages, substantially 0.1% to 2.0%. Montanic acid itself, however, is not as effective as the esters thereof. Therefore the designation polar wax includes esterified montanic acid, commercial montanic acid itself and other polar waxes, preferably those which have at least the polarity of candelilla wax. Likewise, esterifled montanic acid and montanic acid itself are equivalents for the purposes of this invention. The sealing effect is much more pronounced in the presence of small percentages of amorphous wax, polymerized isobutylene, ester gum or other resin which is soluble or dispersible in the molten wax.

This application is a continuation in part of my application Serial No. 186,978, filed on January 26th, 1938.

A polar substance is understood to be one which contains special structural groups, known as polar groups. When the substance is in molten condition or in solution, the polar groups orient themselves toward the surface or interface while the hydrocarbon part of the molecule remains buried in the liquid. It is thought that these oriented molecules attach themselves to the cellulose fibers forming crystal nuclei from which crystals and enhancing the reinforcing effect of y strength. The polar waxes which I use have at least substantially the polarity of candelilla wax.

Carnauba wax is more polar than candelilla wax.

The polarity of the wax is tested by the increase in sealing strength. I

The polymerized isobutylene, and the amor- -phous wax, probably act to some extent as crystal modifiers, in effect increasing the number of the polar waxes.

The preferred ester of montanic acid is the glycerol ester.

The composition could also include ester gum, or other resin which is soluble or dispersible in the molten petroleum wax, and in the proportion of .5% to 5%.

The montanic acid is a polar compound. Therefore, the montanic acid and the polar waxes, which include carnauba wax or candelilla wax, are utilized in the composition in the proportion of substantially .1% to 2%, amorphous wax can be used in the proportion of substantially .1% to 10%, the amorphous wax can be replaced by the polymerized isobutylene in the proportion of .1% to 5%, and the ester gum or other compatible resin can be used in the proportion of .5% to 5%. These proportions may be based upon the weight of the entire composition or upon the weight of the non-amorphous petroleum wax. The polar substances which are used are relatively hard and their melting points are higher than F. They are soluble or dispersible in the petroleum wax at a temperature of F. or above. The other materials above mentioned, such as the polymerized isobutylene and the amorphous wax, are softer than the polar substances. Said relatively soft materials are also soluble or dispersible in the petroleum wax at temperatures above 160 F.

I claim:

1. A solid meltable wax coating composition useful in making waxed paper and having a melting point substantially between 120 F. and F., said composition being substantially free from liquid ingredients and being self-sealing when heated and subsequently cooled, said composition including a major proportion of petroleum wax and a minor proportion of a fusible polar wax-like substance selected from the group crystals of the polar substance grow throughout and according to the theory developed above, should not be effective in increasing sealing consisting of montan wax, montanic acid, carnauba wax and candelilla wax, the proportion of the fusible polar wax-like substance being at least substantially 0.1 per cent. of the petroleum wax and not exceeding substantially 2 per cent. of the petroleum wax, said fusible polar wax-like substance and the petroleum wax constituting a compatible mixture which remains stable during said self-sealing.

2. A composition according to claim 1 in which the fusible polar wax-like substance has a melting point which is higher than the melting point of the petroleum wax.

3. A composition according to claim 1 in which the fusible polar wax-like substance has an acid value substantially between 10-152 and an ester value which is substantially between 25-155.

4. A composition according to claim 1 in which the melting point of the fusible polar wax-like substance is substantially between 167 F.-183 F.

5. A composition according to claim 1 in which the fusible polar wax-like substance has a melting pointof 167 F.-183 F., an acid value of 10- 152 and an ester value of 25-155.

FREDERICK WARDE PADGE'IT.