US3061493A - Adhesive composition and product - Google Patents

Description

United States Patent @fifice 3,061,493 Patented Oct. 30, 1962 3,061,493 ADHESIVE COMPOSITION AND PRODUCT Harlan V. Anderson, Edina, Minn., assignor to RAP Industries, Inc., a corporation of Minnesota No Drawing. Filed June 19, 1956, Ser. No. 592,241 15 Claims. (Cl. 154-50) This invention relates to new and useful adhesive composition and to products utilizing that composition. More particularly, this invention relates to a heat sealable composition for bonding reinforcing paper bands to transparent wrapping materials for bread and similar bakery products.

In recent years it has become common practice in the manufacture and distribution of bakery products, particularly of bread, to wrap each product in a transparent wrapping material, such as cellophane or the like. These transparent wrapping materials are non-porous and readily foldable, adapting them for easy wrapping of each loaf of bread, for example, and easy folding of the package ends into closing and sealing engagement to provide a 'highly sanitary wrapper. The transparency of the wrapper has great appeal, enabling the purchasing housewife to view the merchandise before buying. Because the transparent wrapper lacks the body and structural strength of waxed paper, it has been customary to reinforce and "strengthen the transparent wrapper by Wrapping a band of paper or like material around the bakery product along with the transparent wrapping materiaL'eithe'r on the inside or the outside, and then seal this reinforcing band into the seam at the bottom of the wrapper. The band customarily carries the indentification of the product and sometimes information as to the price, etc.

When the band is adheredto the inside of a bread wrapper only at the seam, difiiculty is encountered by the ultimate consumer, usually the housewife, when she attempts to reinsert slices of bread into the package after one-third to one-half of the loaf has been used. The band tends to collapse making reinsertion of slices diflicult. If the least bit of pressure is exerted in an attempt to realign the band, often the seam. opens and the package comes apart.

It has previously been proposed to overcome this objection to the use of reinforcing bands in transparent wrapped packages by adhering the banding material to the wrapping strip along its entire length, either-across the entire width of the band or at least along its edges. Considerable difficulty has been encountered in adopting these proposed solutions to the problem since waxed paper, which is usually used as the banding material, and cellophane, which is'usually used as the wrapping material, are somewhat incompatible and do not readily adhere to one another. When pressed together under the effects of heat and applied pressure the wax from the waxed paper bands tends to exude and then recoalesce in areas which vary from translucent to opaque and detract from the appearance and clarity of the labeling band. At the same time, the waxed band does not adhere well to the transparent wrapper.

The present invention is directed to an adhesive material which, when applied to a paper band, permits that band to be readily and securely bonded to a transparent wrapping strip, such as cellophane, while at the same time producing a firmly adhering transparent adhesive bond which detracts not at all from the attractiveness of the printed indicia on the labeling band.

It is a principal object of this invention to provide a heat sensitive adhesive material for bonding reinforcing bands to wrapping strips.

Otherobjectsof the invention will become apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various Ways in which the principles of the invention may be employed.

Broadly stated, the invention comprises a heat sealable adhesive composition made up of microcrystalline wax containing a minor proportion of at least one long straight chain fatty amide. The adhesive composition preferably contains high melting point parafiin wax as an extender for the microcrystalline Wax and a minor amount of polyethylene to impart additional scuff resistance, hardness and gloss to the adhesive coating. The invention includes not only the adhesive composition per se but also reinforcing bands coated with the waxy adhesive and transparent Wrappers and packages utilizing the coated bands.

In general, the adhesive composition of this invention may comprise from about 92 to 99.75 percent Wax, about 0.25 to 3.0 percent of fatty amides and from about 3 to 5 percent of polyethylene. The wax fraction of the composition may consist entirely of microcrystalline Wax, but, desirably it is extendedby the addition of a quantity of paraffin wax. Preferably, the Wax fraction is composed of from about to 75 percent of microcrystalline wax and from about 10 to 25 percent of paraffin wax, although as much as 50 percent of parafiin may be used.

When the wax fraction is composed entirely of microcrystalline wax it is preferred to use a mixture of micro crystalline waxes of different melting points. As an example, the wax fraction is composed of about 50 to 65 percent of 175 F. melting point microcrystalline wax and about 50 to 35 percent of F. melting point microcrystalline wax. When high melting point paraffin wax is used as an extender, then it is preferred to use a lower melting point (145 F.) microcrystalline wax as the tacky sealant. I

The addition of polyethylene is desirable because it imparts hardness, gloss and scuff resistance to the coating resulting from. the application of the adhesive composition to paper. The added polyethylene does not contribute to the sealing properties of the composition but it does not materially detract from them. Polyethylene behaves in somewhat the same manner as high melting point parafiin in improving the finish of the adhesive coating but from 3 to 5 percent of polyethylene has about the same effect as 50% of high melting point parafiin. A preferred polyethylene resin is that grade having an average molecular Weight of 19,000 although other polyethylene resins having molecular weights as low as 5,000 have been used successfully.

.Microcrystalline waxes are selected as sealants for adhering reinforcing bands to transparent wrappingmaterial because of the tackiness they possess when applied as thin coatings. This tackiness is not materially lessened by the addition of polyethylene and/ or high melting point paraflins in the ranges specified.

The result is that when microcrystalline wax coatings are applied in thin layers to paper stock in sheets or rolls and the paper is then stacked or rerolled the microcrystalline wax coatings tend to adhere to adjoining waxed surfaces producing the undesirable condition known as blocking. It has been discovered that blocking of waxed paper coated with the wax adhesives according to this invention can be effectively prevented by the addition of a small amount of at least one long straight chain fatty amide. The amides which have been found to be useful are the saturated and unsaturated long straight chain fatty amides having from 16 to 18 carbon atoms. The amides are added in amounts from as little as 0.25 percent of the total by weight to about 3 percent.

Pure isolated fatty amides are not readily obtainable so that for practical reasons it is preferred to use the proprietary mixtures of fatty amides which are readily available. One of these is composed predominantly of 9-octadecenamide with minor amounts of octadecanamide and 9-l2-octadecandienamide. Another is composed predominantly of octadecanamide with lesser amounts of hexadecanamide and 9-octadecenamide. Of these, the first is a preferred material, although mixtures of the two may be used. A typical mixture is made up of 4 parts of the former to one part of the latter.

The amount of anti-blocking fatty amide used is related to the tackiness of the microcrystalline wax. A lesser amount of fatty amide is used if the adhesive composition contains polyethylene, high melting point parafiin and/or less tacky higher melting point microcrystalline waxes. Greater amounts of fatty amide are used if the adhesive composition contains straight microcrystalline wax, particularly of the more tacky lower melting point microcrystalline waxes.

The ingredients of the composition are melted and admixed in any order. As a practical expedient the wax components are usually first melted and the fatty amide and polyethylene are added to the molten wax and agitated to uniformly distribute the additives through the wax. Although the wax adhesive may be applied to the paper stock by any conventional paper coating method, it is prefened to apply the adhesive coating by immersing the paper stock in a molten bath of the adhesive, squeezing off the excess by passing the paper between rollers and then immediately chilling in a water bath. The coated paper may then be rerolled at once for storage or shipment.

The identifying indicia and other informational or decorative matter are imprinted upon the paper stock before coating. The coating is applied in a thin layer so that it is transparent and in no way obscures or detracts from the printed matter on the paper bands. It is unnecessary to use white microcrystalline wax to maintain this transparency. The lighter yellow and amber microcrystalline waxes may be used as well. The adhesive layer is compatible with cellophane and similar transparent wrapping material and is readily adhered with heat and light pressure.

The adhesive coated reinforcing band is preferably applied to the transparent wrapping material on the wrapping machine itself. sure to produce a firmly adhering reinforcing and strengthening band on the transparent wrapper, which is fed to a conventional wrapping machine in the conventional manner to produce a wrapped package. An exemplary form of laminating device for applying the adhesive coated band of this invention to transparent wrapping material is described in United States application Serial No. 518,755, filed June 29, 1955, by Clarence N. Lithio, now Patent No. 2,790,480, issued August 30, 1957. It is to be understood, however, that this apparatus is merely exemplary of one form of handing apparatus which may be used.

To check the anti-blocking characteristics of the adhesive the coated paper is subjected to a standard blocking test designed to duplicate conditions which one might encounter in the field. The test includes storage at 100 F. for 24 hours under an applied pressure of three pounds per square inch. After this period of time none of the compositions of this invention showed any marring or sticking.

The invention is illustrated by the following examples:

Example I The adhesive composition was formed by admixing It is applied under heat and pres- 4 the following ingredients in the proportions specified in parts by weight:

Shellmax 500 (a F. melting point microcrystalline wax) 81.00 Sun 5512 (a F. melting point paralfin) 14.25 Polyethylene DYNH (polyethylene pellets) 3.75 Armid O (a proprietary mixture of fatty amides containing 91% 9-octadecenamide, 6% octadecanamide and 3% 9-l2-octadecadienamide)- 0.99 Tenamene-Zi (a proprietary antioxidant) 0.01

A 25 pounds opaque sulfite paper in rolls was used as the band stock. The band stock was first printed. The width of the paper is such that a plurality of rolls of bands are printed and coated simultaneously. The adhesive composition was maintained at 200-210" F. The printed paper was plasticized with moisture prior to immersion in the molten adhesive bath. The coated paper was passed through squeeze rollers as it left the molten bath to limit the thickness of the adhesive layer and then was passed through a water chilling bath and rerolled. The wax adhesive was applied at the rate of 10 to 13 pounds for a minimum of 2 /2 pounds per ream surface on the printed side.

The rolled coated band stock was cut into individual rolls of bands. One of these rolls was mounted on a conventional bread wrapping machine equipped with a banding device as described in application Serial No. 518,775. The banding apparatus was positioned to apply the band to the inside surface of the ultimate bread wrapper. With the heating roll set at about ZOO-220 F. the adhesive coated band was applied continuously to the center of a much wider strip of cellophane as it came off its supply roll. The banded cellophane wrapper passed immediately into the wrapping machine where is was formed into a bread wrapper, severed, sealed and finally emerged as a completed package enclosing a loaf of bread.

Example II Another typical adhesive composition is made up with the following ingredients.

Example III A similar composition omitting the polyethylene con tained the following:

Parts F. melting point microcrystalline wax 60.0 145 F. melting point microcrystalline Wax 38.0 Armid O 1.6 Armid HT 0.4

Example IV A composition containing ordinary paraffin had the following ingredients:

Parts 145 F. melting point microcrystalline wax 49.0 132 F. melting point paraflin 49.0 Armid O 1.6 Ar-rnid HT 0.4

Example V A composition having a minimal amount of anti-blocking agent had the following ingredients:

Parts 145 F. melting point microcrystalline wax 49.75 135-137 F. melting point parafiin wax 50.00 Armid O 0.25

This formulation did not block in the standard test.

Example VI An adhesive composition containing microcrystalline waxes of different melting points in equal amounts contained the following:

Parts 145 F. melting point microcrystalline wax 48.0 175 F. melting point microcrystalline wax 48.0 Polyethylene DYNH 3.0 Armi-d O 1.0

Example VII Another composition had the following ingredients:

Parts 145 F. melting point microcrystalline wax 65.0 155 F. melting point paraifin wax 30.0 Polyethylene 3.0 Armid O 1.6 Armid HT 0.4

The adhesive coating may be applied to one or both sides of the paper reinforcing band depending upon the coating method used. The band in turn may be bonded to either the inside or the outside surfaces of the transparent wrapper. When the band is applied to the inside of the wrapper the adhesive coating is necessarily present on the printed surface of the band. When the band is applied to the outside surface of the wrapper the adhesive must be on the reverse side of the band.

The Waxy adhesive coating is preferably applied in amounts so as to produce a coating of at least about 2 /2 pounds per ream surface of 3000 square feet on the side to be bonded. With a relatively porous paper stock and applying adhesive to both sides a total of from about to 13 pounds of adhesive material may be required to produce the desired surface.

it is apparent that many modifications and variations of this invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

What I claim is:

l. A vwrapper for bakery products comprising a transparent wrapping sheet, an elongated reinforcing and strengthening band of paper of substantially lesser width than said transparent wrapping sheet disposed longitudinally with respect to said transparent wrapping sheet and spaced approximately midway between the edges thereof and thermally bonded thereto under pressure, the bond between said paper band and said transparent wrapping sheet being in the form of a thin transparent coating continuous across the entire width of said paper band and consisting essentially of a predominant proportion of microcrystalline wax and a minor proportion of from about 1 to 3 percent of at least one amide of a long chain fatty acid having 16 to 18 carbon atoms.

2. A wrapper according to claim 1 further characterized in that the wax fraction of the bonding coating contains from about to 50 percent of paraffin.

3. -A wrapper according to claim 1 further characterized in that the fatty amide is selected from the class of long straight chain saturated and unsaturated fatty amides.

4. A wrapper according to claim 3 further characterized in that the fatty amide is predominantly 9-octad e a isla 5. A wrapper according to claim 1 further characterized in that the bonding coating contains from about 3 to 5 percent of polyethylene.

6. A band for strengthening and reinforcing and applying identifying indicia to transparent wrapping material which comprises an elongated printed paper strip coated on at least one side with a thin transparent continuous layer consisting essentially of a predominant proport-ion of microcrystalline wax and a minor proportion of from about 1 to 3 percent of at least one amide of a long chain fatty acid having 16 to 18 carbon atoms.

7. A band according to claim 6 further characterized in that the wax fraction of the coating contains from about 15 to percent of paraffin.

8. A band according to claim 6 further characterized in that the fatty amide is selected from the class consisting of long straight chain saturated and unsaturated fatty amides.

9. A band according to claim 8 further characterized in that the fatty amide is predominantly 9-octadecenamide.

10. A band according to claim 6 further characterized in that the coating contains from about 3 to 5 percent of polyethylene.

11. A heat and pressure scalable adhesive composition consisting essentially of a predominant portion of microcrystalline wax and a minor proportion of from about 1 to 3 percent of at least one amide of a long chain fatty acid having 16 to 18 carbon atoms.

12. A composition according to claim 11 further characterized in that the wax fraction of the adhesive contains from about 15 to 50 percent of paraifin.

13. A composition according to claim 11 further characterized in that the fatty amide is selected from the class consisting of saturated and unsaturated long straight chain fatty amides.

14. A composition according to claim 11 further characterized in that the adhesive contains from about 3 to 5 percent of polyethylene.

15. A heat and pressure scalable adhesive composition consisting essentially of a predominant wax fraction consisting of microcrystalline wax and from about 15 to 50 percent of paraffin, from about 3 to 5 percent of polyethylene and from about 1 to 3 percent of at least one fatty amide selected from the class consisting of amides of saturated and unsaturated long chain fatty acids having from 16 to 18 carbon atoms in the molecule.

References Cited in the file of this patent UNITED STATES PATENTS 1,849,774 Taylor Mar. 15, 1932 1,994,507 Farris Mar. 19, 1935 2,286,307 :Replogle June 16, 1942 2,299,306 Cornell Oct. 20, 1942 2,530,838 Orozco et al. Nov. 21, 1950 2,559,398 Capell July 3, 1951 2,582,037 Hyde Jan. 8, 1952 2,733,225 Smith Jan. 31, 1956 2,773,045 Simerl et al. Dec. 4, 1956 2,790,480 Lithio Apr. 30, 1957 2,803,612 Moyer Aug. 20, 1957 OTHER REFERENCES Tappi, Bulletin No. 8, March 29, 1943, page 3, pub. by Technical Association of the Pulp and Paper Industry.

Claims (1)

1. A WRAPPER FOR BAKERY PRODUCTS COMPRISING A TRANSPARENT WRAPPING SHEET, AN ELONGATED REINFORCING AND STRENGTHENING BAND OF PAPER OF SUBSTANTIALLY LESSER WIDTHH THAN SAID TRANSPARENT WRAPPING SHEET DISPOSED LONGITUDINALLY WITH RESPECT TO SAID TRANSPARENT WRAPPING SHEET AND SPACED APPROXIMATELY MIDWAY BETWEEN THE EDGES THEREOF AND THERMALLY BONDED THERETO UNDER PRESSURE, THE BOND BETWEEN SAID PAPER BAND AND SAID TRANSPARENT WRAPPING SHEET BEING IN THE FORM OF A THIN TRANSPARENT COATING CONTINUOUS ACROSS THE ENTIRE WIDTH OF SAID PAPER BAND AND CONSISTING ESSENTIALLY OF A PREDOMINANT PROPORTION OF MICROCRYSTALLINE WAX AND A MINOR PROPORTION OF FROM ABOUT 1 TO 3 PERCENT OF AT LEAST ONE AMIDE OF A LONF CHAIN FATTY ACID HAVING 16 TO 18 CARBON ATOMS.