US2446414A - Method of applying heat-sealable labels - Google Patents

Description

Aug. 3, 1948. R. A. FARRr-:LL ET Al. 2,446,434

METHOD OF APPLYING HEAT-SEALABLE LABELS Filed sept. so, 1944 2 sheets-sheet 1 J,H/@mz UTS @5c/" Wfegg. Qd Magg/Zal. @new Patented Aug. 3, 1948 2,446,414 METHOD oF APPLYING HEAT-SEALABLE LABELS Robert A. Farrell and Charley L. Wagner, Me-

nasha, Wis.,

assignors to tion, Rothschild, Wis.,

consin Marathon Corporaa corporation oi Wis- Application September 30, 1944, Serial No. 556,620

Claims. (21S-62) This invention relates to heat-sealable labels which do not have any, exposed coating material on their outer surfaces. More speciiically, this invention relates to heat-scalable labels having an adhesive composition provided internally of the label which is not normally exposed, but which is activated Aand brought to thev surface thereof to provide an adhesive nlm when it is desired to amx the label to any desired surface by application of heat and pressure thereto.

Further details and Iadvantages of the invention will be apparent from the following speciflcation and drawings wherein:

Figure 1 is a perspective view of `a rectangular heat-sealable label partly broken away to show the components thereof,

Figure 2 is an enlarged sectional view taken on lines 2 2 of Figure 1,

Figure.3 is an enlarged sectional view of the label afxed to a base by application of heat and pressure to the label, i

Figure 4 is a perspective view of a package Wrapped in Cellophane to which a label is amxed,

Figure 5 is a perspective view of a sealing label having indicia printed thereon, and

Figure 6 is a perspective view of a roll of the label shown in Figure 5 in continuous strip form.

Heat-scalable labels have been provided previously with a surf-ace coating of suitable compositions which are activated or softened by action of heat when the label is to be sealed to a suitable surface. In the label printing and die cutting operation the sheet is repeatedly subjected to drastic mechanical pressures. Any exposed coatings produced on such equipment tend to separate and accumulate on the dies and contacting machine parts, progressively build up accumulations which would interfere with the operation the equipment. By use of our sheet materials t ese diificulties are entirely eliminated as no coating is exposed in our sheet. The stock sheet materials from which we make our labels is readily convertible into labels by means of ordinary label making equipment. Furthermore labels having exposed coatings 4are difficult to handle prior to use due to pressure-sensitive properties of some thermoplastic compositions. When such labels are stacked or rolled up the outer coating composition has a tendency to cause blocking or sticking together of the contacting labels. Furthermore, such prior external coatings cause difilculty when the labels are handled by machinery as the coating may adhere to machine parts or scrape on and accumulate on moving parts and thus prevent efcient operation. There are also many sticky and soft types of heat-scalable compositions that could not be possibly used as exposed external coatings that can now be used in our heat-scalable labels made in accordance with our invention as the sealing composition of our label is not exposed normally and will not cause blacking or cause adhesion of any contacting materials These disadvantages and difculties have been effectively overcome by our invention as we produce an eicient heat-sealable label made of superposed plies of sheet materials without having any external or exposed coating thereon of any kind. According to our invention, our composite labels indicated generally by numeral lo in the drawings are made from a stock sheet material, indicated by numeral 3 in Figures 1 and 2, formed of a relatively impermeable base sheet, provided' with a smooth, continuous, uniform thermoplastic coating film 2 thereon and having a. normally non-removable relatively porous cover sheet I adhered to and covering the adhesive film. The cover sheet l is relatively porous and permeable as compared with the base sheet 3 in regard to the adhesive lm 2 when in softened or molten condition, so that when the label is subjected to heat and pressure, the adhesive film 2 will migrate, pass or strike through the relatively porous cover sheet to provide a sealing adhesive film 4 as indicated in Figure 3 on the surface of the porous sheet in sumcient amount to form a strong seal to a supporting surface i2 to which the label is applied.

In practical production of the stock material from which our composite labels are made We apply the homogeneous thermoplastic heat-sealing adhesive composition 2 as a smooth continuous exible coating of suitable uniform thickness and of a predetermined basis weight on the base sheet by any suitable means and apply the cover sheet to the adhesive layer under suitable controlled conditions as to prevent penetration of the adhesive therethrough and formation of a surface film on the exposed face of the cover sheet. We may apply our molten adhesive composition for example between the base sheet and cover sheet by means of suitable rotating rolls adjusted so as to provide a controlled and predetermined thickness of nhn between the sheets. The combined sheets may be chilled to control the degree of penetration of the adhesive therethrough. The viscosity and physical characteristics of theadhesive composition may also be suitably controlled to prevent migration of the composition through the cover sheet when the sheets are combined with the adhesive. Instead of applying the adhesive as a continuous film we may apply the composition only in certain predetermined areas and of any suitable contour. The composition, for example, may be applied in the form of bands or stripes at the margins or other portions between the sheets so that the sheets are heat-scalable only in such areas. The adhesive composition may also be applied by means of knurled or specially contoured rollers so as to apply the adhesive in suitably spaced areas or in the form of discrete particles or spots instead of in a continuous film form. In such application a sufficient quantity of the adhesive is applied so that it will migrate through the porous sheet to form a seal or bond.

Any suitable relatively impermeable base sheet material 3 is selected depending upon the particular usage of the final product, such as paper, paper board, regenerated cellulose, glassine, parchment paper, rubber hydrochloride, cellulose acetate, ethyl cellulose, vinyl resins, any suitable synthetic resin foils, metal foils and the like.l The base sheet material may be treated so as to impart any desired additional characteristics thereto such as greater imperviousness to the adhesive used, wet-strength, greaseproofness and iiexibilityl In the case of paper, it may be suitably coated and supercalendered for printing purposes.

The cover sheet I is selected so as to be relatively porous as compared with the relatively impermeable base sheet, 3, and of such structure as to permit migration of the molten or softened adhesive coating layer 2 to the surface `of the porous sheet, through the material of the sheet itself or through any interstices, pores, channels, openings or perforations present in the sheet l. In other words, the cover sheet I is selected so as to have suitable physical or structural characteristics so as to permit the molten or softened adhesive layer 2 to migrate or pass outwardly Ato the exposed surface of the porous sheet. Depending upon the type of porous sheet selected, the molten adhesive will migrate either through the substance of which' the sheet may be made or through any interstices, pores, channels, slits or openings existing in the sheet. Light-weight paper tissue, for example, has a porous structure formed by interlacing of cellulosic fibers which permits the molten or softened adhesive to pass through the sheet readily.

We may use any suitable type of porous, woven or reticulated sheets, such as woven and knitted fabrics, netting and the like. We may also use comparatively dense or impervious sheets, such as parchment paper, glassine, regenerated cellulose, and even metal foils, by providing slits, holes, or openings of suitable dimensions and suitably distributed throughout such sheet materials or in selected and predetermined areas so as to permit the molten or softened adhesive layer 2 to pass through such openings. Instead of using a prefabricated porous cover sheet we may apply pulp, cotton, wool and similar fibers, to the molten thermoplastic adhesive film 2 immediately after it hasbeen applied to the base sheet and before it has congealed to form in situ the equivalent of a separately applied cover sheet. The expression porous sheet or cover sheet" is intended to include any of the previously described sheets which permit the softened or molten adhesive layer 2 to migrate to the surface thereof in sumcient amount to provide an adhesive sealing ilm on the outer surface of the porous sheet. We prefer to use a porous sheet made of lightweight paper tissue relatively lighter in weight than the base sheet, for example, less than 20 lbs. (basis weight 480 sheets 24 x 36 in.) paper sulphite tissue. Such tissue sheet is comparatively porous with respect to the base sheet so as to permit the adhesive layer to migrate differentially in greater amount by weight per unit weight of sheet through the porous sheet rather than the relatively impermeable base sheet so as to generate an' adhesive film on the outer surface of the relatively porous cover sheet. The porous paper cover sheet may be treated if desired with ureaformaldehyde resins, or melamine resins, in small amounts. say 1 to 5% by weight, to increase its wet-strength withoutrhowever affecting its porosity and other original physical characteristics. Both the base sheet and porous paper sheethmay be wax-sized or dry-waxed to increase their` waterproofness, moldproofness, machine workability, etc.

In any particular combination of relatively impermeable base sheet and relatively porous cover sheet the adhesive layer is of such character that upon application of heat and pressure to a label made of such combined sheet the intermediate layer upon melting or softening will be driven or migrate differentially through the cover sheet and penetrate to the surface thereof, rather than tend to migrate through the base sheet which resists the migration of the adhesive therethrough as it, is relatively more impervious and/or dense than the porous sheet. The adhesive, in other words, will take the path of least resistance and will penetrate through the relatively porous cover sheet and only partially, if at all, through th'e relatively denser base sheet to generate an adhesive sealing iihn on the surface of theporous sheet.

The cover sheet i may be treated so as to permit migration of the adhesive only at certain prede termined areas. This may be accomplished, for example, by lacquering a porous paper sulphite tissue sheet in certain predetermined areas so th'at the adhesive will not migrate through the sheet at such treated areas. A dense type of sheet may also be provided with suitable openings, slits or pinholes at certain predetermined areas through which the adhesive may migrate, but not elsewhere.

We nd it advantageous to provide an adhesive nlm of a basis weight of at least about 11/2 to 2 times or preferably more than the basis weight of the porous cover sheet when using, for example, a paper base sheet of 17 lb. sulphite and 9 lb. porous sulphite paper sheet (basis weight 480 sheets 24 x 36 in.) When such amount of intermediate nim is provided there will be suicient adhesive composition to bond the sh'eets together, and also upon application of heat and pressure, the adhesive composition will penetrate and saturate the cover sheet to such extent as to migrate to the surface to provide a suitable bonding film at the outer surface thereof.

Suitable thermoplastic intermediate adhesive coatings which we may use are made of selected or blended microcrystalline waxes; microcrystalline waxes having one or more added viscosityincreasing ingredients such as various elastomers, resins, gums, rubber, synthetic rubber, isobutylene and butylene polymers, metallic soaps such as aluminum soaps of the higher fatty acids as aluminum stearate, oleate or palmitate in amounts from 1 to 30% by weight; paraiiln wax containing any of the previously mentioned ingredients added thereto and in about the same amounts; cellulose derivative compositions; synthetic resins, such as phenol-formaldehyde resins, urea-formaldehyde resins, vinyl resins; asphalts; natural gums; protein-containing composition such as zein; and casein. These compositions are utilized for combining the base sheet and the cover sheet in any known manner, as previously explained, so as to control selectively the degree of penetration of the composition into the base and relatively porous sheet. When using thermoplastic hot-melt compositions having wax as the base ingredient, we may chill the combined sheets at the point of combining so as to control penetration or migration vof lthe composition through both combined sheets. The ingredients of the composition used may be suitably selected and compounded so as to have a suitable predetermined viscosity so as to be nonpenetrating with respect to the sheets to be combined. The use of viscosity-increasing ingredients serves (1) to bring up the viscosity to a point where a greater weight of adhesive can be applied successfully with the present types of available coating equipment, (2) to make the adhesive of such viscosity that it will penetrate less into the base sheet using, for example, open type of sheets such as board or heavy weight sulphite paper, and yet permit of suilicient penetration through the cover sheet to eilect the seal when heat and pressure are applied, (3) to bring up the adhesiveness of certain hot melt materials such as paramn wax, in order to make them usable for the purpose of this invention. The conditions under which the sheets are combined, such as speed of uniting, temperature of application of the adhesive, chilling of the combined sheets also can be controlled in any known m-anner to prevent penetration. In this way vwe obtain a stock sheet from which our heat-sealable labels are made which has a continuous iiexible uniform layer of the intermediate sealing composition Without any of the composition being present on the outer exposed surfaces of the sheet. We may retain the original unimpaired physical surface characteristics of the sheet materials used so that they can be printed with any suitable indicia Il for labels and the like, as illustrated in Figure 5, without disturbing the intermediate layer which is activated and provides a sealing means only upon application of heat and pressure to the label.

The following are typical specific examples of the stock sheet materia from which our heatsealable labels are made, he numerals preceding each component being the same as in the drawings, weights being given per ream (480--24 x 36) COMPONENT Example 1 Pounds weight per ream Example 3 1. Porous sulphite tissue paper 9.0 2. 3% aluminum stearate, 5% ester gum, and 92% mlcrocrystalline wax M. P. 145 F.,

1. Porous dry waxed sulphite tissue paper 11.0 2. 3% aluminum stcarate, 5% ester gum, and

92% microcrystalline wax M. P. 145 F.,

by Wt 25.0 3. Regenerated cellulose l 20.0

Total -56.0 E :rample 5 i l. Porous sulphite tissue paper 9.()` 2. 3% aluminum stearate, 5% ester gum, and 92% microcrystalline Wax M. P. 145 F., by Wt 25.0 3. Highly plasticized glassine 30.0

Total 64.0

Example 6 1. Porous sulphite tissue paper 9.0 2. 97% by wt. microcrystalline Wax M. P. 14S-7 F. and 3% by wt. aluminum stearato 19.0 3. Highly hydrated greaseproof sulphite g paper 17.0

Total 45.0

O ur labels can be formed of any suitable predetermined contour either as individual labels as illustrated in Figure 5 or in continuous strip form as illustrated in Figure (i so that they may bey wound up in a roll I8. The strip may be severed along lines i6 by any suitable equipment prior to heat-sealing the labels to any desired surface.

The exposed face of the dense or relatively impermeable base sheet 3 of our labels may be printed if desired with any suitable indicia Il as illustrated in Figure 5. Our labels are particularly suitable for application by heat and pressure to packages wrapped in Cellophane (regenerated cellulose) as illustrated in Figure 4. The individual labels are heat-sealed to a sheet of Cellophane or other suitable wrapping material While in flat condition prior to the wrapping operation so that when a package is wrapped it will have the appearance as shown, for example, in Figure 4,

the label l0 being aflxed to the exposed surface of the Wrapper 2 I.

Our labels are also adapted for the sealing of ends of wrapped packages. It is also obvious that labels in the form of elongated stripes, bands and the like may be similarly applied to any part of the body of the package. Our labels can be readily heat-sealed to any types of wrapping and sheet materials such as ordinary paper, parchment, glassine, Cellophane, cellulose acetate, Plioiilm (rubber hydrochloride) waxed papers, lacquered papers, coated papers of all kinds, heat-sealable coated Cellophane, metal foils, woven and knitted textile fabrics made of cotton, rayon, nylon, wool, and the like.

The sealing composition we use is heat sensitive upon application of heat thereto and is adapted to merge or coalesce with ordinary wax or. other types of coatings upon usual wrapping 7. materials used for packaging purposes. Our labels are adapted particularly to be used upon any type of shellacked or coated papers which are difficult to seal by the use of glues or similar adhesives which are available on the market today. Our labels are adapted also for sealing to cardboard, glass and metal surfaces, leather and Wood. Our labels can be sealed to almost any desired surface or object by application of suitable heat and pressure thereto. i

Numerous changes and modiiicationsmay be made in the specific embodiments of our invention utilizing the essential and significant features Vof our invention as fully disclosed herein. It is intended to include such modifications Within the scope of the appended claims.

We claim:

l. A method of labeling which comprises providing a label comprising in adhered relation a base sheet material and a relatively porous sheet material adhered to said base sheet by an intermediate thermoplastic adhesive, said adhesive being confined to the inner surface of said porous sheet and the outer exposed surface of said porous sheet being lsubstantially unchanged from its original characteristics, positioning said labe1 on a supporting surface with said porous sheet in face contact with said supporting surface, applying heat and pressure to the exposed surface of rather than through said base sheet material and in amount to generate an adhesive sealing film on the outer surface of said porous sheet to afllx the label to a supporting surface.

2. A method of labeling which comprises providing a label comprising in adhered relation a base sheet material of cellulosic material having a relatively dense structure and a. relatively porous cellulosic sheet material adhered to said base sheet by an intermediate thermoplastic adhesive, said adhesive being confined to the inner surface of said porouslsheet and the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, positioning said label on a supporting surface with said porous sheet in face contact with said supporting surface, applying heat and pressure to the-exposed surface of said base sheet for acti- -vating said adhesive to migrate differentially through said porous sheet rather than through said base sheet material and in amount to generate an adhesive sealing film on the outer surface of said porous sheet' to aiiix the label to a supporting surface.

3. A method of aflixing labels to a supporting surface which comprises providing a label comprising in adhered relation a base sheet material and a relatively porous sheet material adhered to said base sheet by an intermediate thermoplasltic adhesive comprising microcrystalline Wax,

said adhesive being confined to the inner surface of said porous sheet and the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, positioning said label on a supporting surface with said porous sheet in face contact with said supporting surface, Aapplying heat and pressure to the exposed surface of said base sheet for activating said adhesive to migrate differentially through said porous sheet rather than through said base sheet material and in amount to generate an adhesive sealing film on the outer surface of said porous sheet to affix the label to a supporting surface.

4. A method of aflixing labels toa supporting surface which comprises providing a. label comprising in adhered relation a base sheet material and a relatively porous sheet material adhered to said base sheet by an intermediate thermoplastic adhesive comprising microcrystalline wax and aluminum stearate, said adhesive being'confined to the inner surface of said porous sheet and the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, positioning said label on a supporting surface with said porous sheet in face contact with said supporting surface, applying heat and pressure to the exposed surface of said basesheet for activating said adhesive to migrate differentially through said porous sheet rather than through said base sheet material and in amount to generate an adhesive sealing film on the outer surface of said porous sheet to ailix the label to a supporting surface.

5. A method of aixing labels toa supporting surface which comprises providing a label comprising in adhered relation a base sheet material and a relatively poroussheet material adhered to said base sheet by an intermediate thermoplastic adhesive comprising wax and an elastomer, said adhesive being confined to the inner surface of said porous sheet and the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics,I positioning said label on a supporting surface with said porous sheet in face contact with said supporting surface, applying heat and pressure to the exposed surface of said base sheet for activating said adhesive to migrate differentially through said porous sheet rather than through said base sheet material and in amount to generate an adhesive sealing film on the outer surface of said porous sheet to aiilx the label to a supporting surface.

ROBERT A, FARRELL. CHARLEY L. WAGNER.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,217,819 Peterson Feb. 27, 1917 1,759,124 MacLaurin May 2.0, 1930 2,054,870 Stelkens Sept. 22, 1936 2,142,039 Abrams et al Dec. 27, 1938 2,184,139 Cunnington Dec. 19, 1939

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