US2430459A

US2430459A - Laminated sheet heat-sealable container

Info

Publication number: US2430459A
Application number: US519392A
Authority: US
Inventors: Robert A Farrell; Charley L Wagner
Original assignee: Marathon Corp
Current assignee: Marathon Corp
Priority date: 1944-01-22
Filing date: 1944-01-22
Publication date: 1947-11-11
Anticipated expiration: 1964-11-11

Description

Nov. ll, 1947. R. A. FARRELL Erm.

LAMINATED SHEETv HEAT-SEALABLE.' CONTAINER Filed Jan. 22. 1944 2 Sheets-Sheet 1 L k/yner m diz@ Nov. 11, 1947. R. A. FARRELL Erm. 2,430,459A

LMINATED SHEET HEAT-SEALBLE CONTAINER 'I Filed Jan. 22. 1944 2 Sheets-Sheet 2 n"""` Wmv' 111111111111111 lilla/111 11,1111 l vated and brought ?atented Nov. 1l, 1947 2,430,459 marmeren sneer naar-Smm commen Robert A. Farrell and Charley L. Wagner,

Menasha, Wis.,

assignors to Marathon Gomration, a corporation ot Wisconsin application January 2z, 1944, serial Nq.

7 Claims. (Cl. 229-55) This invention relates to packages and containers formed from heat-scalable sheet materials'not havingany exposed coating material on its outer surfaces. More specically, this invention relates to packages and containers made of heat-scalable sheet material having a composition provided internally of the-sheet material that is not normally exposed, but which is actito thesurface to provide an adhesive nlm which, forms a seal upon application of heat and pressure edarea desired to be sealed.

Further details and advantages of the invention will be apparent from the following specication and drawings wherein: v

Figure 1 is a perspective view of the heat-sealable sheet material partly broken away' to show the components thereof thatis used for making packages and containers,

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

Figure 3 is a plan view of a bag made of the heat-scalable sheet material illustrated in Figure l,

Figure 4 is an enlarged fragmental sectional view taken on lines I-l of Figure 3,

Figure 5 is an enlarged fragmental sectional view of the upper portion of Figure 4,

Figure 6 is an enlarged sectional view lines 6-6 of Figure 3, i

Figure 'l is a perspective view of a package wrapped and sealed in the heat-sealable sheet of Figure 1,

Figure 8 is an enlarged fragmental sectional view taken on lines B-S of Figure '1,

Figure 9 is an enlarged fragmental sectional view of the seam portion A' shown in Figure 8,

Figure 10 is an enlarged fragmental sectional view taken on lines lt--ill oi Figure 7, and

Figure 11 is an enlarged fragmental sectional view of the seam portion B' shown in Figure 10.

Hitherto available heat-scalable sheet materials for packaging purposes and for making containers have been provided with a surface coat- ,ng of suitable compositions which are activated or softened by action of heat when a seal or seam is to be formed. Such sheet materials are dimcult to handle prior to use due to their pressurev sensitive propertiesv when they are stacked or rolled up as the outer coating composition has a tendency to cause blocking or sticking together of the contacting sheets or layers. Furthermore, such prior external coatings cause difficulty when the sheet materials are handled by wrapping machinery as the coating may adhere to taken on to any suitably selectcause blocking or cause effectively overcome lize an efiicient heat-scalable sheet made of susheet 3, as shown in machine parts or scrape oi! and accumulate on moving parts and thus prevent eiiicient operation. There are also many sticky and soft types of heat-scalable compositions that could not be possibly used as external coatings that can now be used in heat-scalable sheets made in accordance with our invention as the composition in our sheet is not exposed and will not adhesion of any contacting materials.

These disadvantages and by our invention as we utiperposed' plies of sheet materials `without having any esternal coating thereon of any kind. The sheets are united by an intermediate continuous nlm formed of a A suitable ,thickness on "basis weight (pounds per 480 sheets size 24 x 36 in.) so that upon application of heat and pressure to any selected area thereof an adhesive film will be generated on the outer surface of one of the shee According to one embodiment of our invention we utilize a combined sheet material, comprising a base 1 and 2, and a-relatively porous sheet material I, these sheets being united by an intermediate continuous flexible smooth uniform thermoplastic tllm 2 of a suitable composition. An important characteristic of sheet I is that it is relatively porous and permeable as compared with the base sheet 3 in regard to the intermediate layer 2 when in softened or molten condition. When the combined sheet is subjected to heat and pressure, the illm 2 will migrate, pass or strikethrough the porous sheet to provide a sealing adhesive film on the surface of the porous sheet insufficient amount to form a strong seal, seam or bond at any area where desired. The porous sheet net only permits the adhesive nlm to migrate to the surface of the sheet, but it adhesive iilm thereby preserving when the sheet is creased, folded or seamed. The

continuity of the intermediate film is thus not broken or impaired by handling, use, .or when the sheet is converted into containers and receptacles, or during any packaging operations', thereby tending to retain the initial vapor and moistureproof and other protective properties of the combined sheet.

Such sheet material is used to form bags, receptacles, container receptacles, tubes and construction which are generally referred to as a container in the appended claims. For exdiiliculties have been suitable composition and of= also serves to reinforce the its continuity,

cartons, packages, linings for the like of any suitable The sheet is folded so that the dense sheet 3 is 5 by neat sealing the sheet to itself as illustrated in Figure 6 or by use of any suitable external l0 adhesive. The bottom seam 3| is then formed by applying heat and pressure to the bottom edge 'I'lle seam is shown in larger then the upper seam 3l is formed by applying heat and pressure to the area A. As shown in superposed areas of the porous sheets are brought in faceto face relationand the 111m 2 at these zo areas is driven through to the inter faces between e contacting areas of the sheet I so as to form a very strong and tight seam.

Many other types of packages may be made form a bond at the overlapped portions to form "aseamasillustratedinliguresiland If tween the overlapped portions instead of using heat and pressure. The ends of the sheet material are then folded over in any suitable desired folds as shown, for example, in Figure 7. Heat and pressure may then be applied to the ends over 40 we may apply the composition only in certain predetermined areas and of any suitablecon'tr. 'I'he composition, for example, may be applied ln 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 application a. sumclent quantity of theadhesive is applied so that it lwill migrate through'the porous sheet to form a seal or bond.

Any suitable base Asheet 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. 'Ihe sheet material may be treated so as to impart any desired additional ousness to the adhesive used, wet-strength, greaseproofness and flexibility. In the case of paper, it may be suitably coated and supercalendered for printing purposes.

The sheet I is selected so as to be relatively porous as compared with the base sheet 3, and of such structure as to permit migration of the molten or softened intermediate 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 I. In other words, the 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 to 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 ilbers which permits the molten or softened adhesive to pass through the sheet readily.

Our invention, however, is not restricted to the use of paper tissue sheets. 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 film on the outer surface of the porous sheet. The porous paper sheet may be treated if desired with urea-formaldehyde resins, or melamine resins, in small amounts, say 1 to 5% by weight, to increase its wet-strength without however affecting its porosity and other original physical characteristics. Both the base sheet and porous paper sheet may be wax-sized or dry-waxed to increase their waterproofness, moldproofness, wrapping machine workability, etc.

combining so as to control penetration or migration of the composition through both combined sheets. The ingredients of the composition used may be suitably selected and compounded so as to have suitable viscosity so' as to be non-penetrating with respect to the sheets to be united during the uniting operation. The conditions A under which the sheets are combined, such as speed of uniting, temperature of application of the In any particular combination of base sheet..

and porous sheet the intermediate adhesive layer is of such character that upon application of heat and pressure to the combined sheet the intermediate layer upon melting or softening will be driven or migrate differentially through the porous 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 porous sheet and only partially, if at all, through the relatively denser base sheet to generate an adhesive sealing film on the surface of the porous sheet.

'I'he sheet i may be treated so as to permit migration of the adhesive only at certain predetermined areas. This may be accomplished, for example, by lacquerin'g a porous paper sulphite tissue sheet in certain predetermined areas so that 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 find it advantageous to form the intermediate adhesive iilm so as to have a basis weight of at least about 1% to 2 times or preferablyl more than the basis Weight of the porous sheet when using, for example, a paper base sheet of 17 lb. sulphite and 9 lb. porous sulphite paper sheet. When such thickness of the intermediate film is provided there will be suicient adhesive composition to bond the sheets together, and also upon application of heat and pressure, the intermediate composition will penetrate and saturate the porous sheet to such extent as to migrate to the surface and form a suitable bonding illm at the outer surface thereof.

Suitable thermoplastic intermediate adhesive layers which we may use are selected or blended microcrystalline waxes; microcrystalline waxes having one or more added ingredients such as various elastomers, resins, gums, rubber, synthetic rubber, isobutylene and butylene polymers,

higher fatty acids as aluminum stearate, oleate or palmitate in amounts from 1 to 30% by weight; parailin 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, ureaformaldehyde resins, vinyl resins; asphalts; natural gums; protein-containing compositions such as zein; and casein. These compositions are utilized for combining and adhering the base sheet to the porous 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 adhesive, chilling of the combined sheets also can be controlled in any known .manner to prevent penetration. In this way we obtain a heatsealable sheet which has a continuous flexible 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, coated, glued or treated in any desired manner without disturbing the intermediate layer which is activated and provides a sealing means only upon application of heat and pressure to selected areas of the combinedsheet.

The following are typical specific examples of our sheet material, the numerals preceding each component being the same as in the drawings,

weights being given per ream (480-24 x 36) CouroNrNr Example 1 Pounds weight per ream 1. Porous dry-waxed sulphite tissue paper-- 13.2

2. Microcrystalline wax M. P. 1409a160 F.-- 19.3 3. High wet strength bleached kraft paper-- 33.5

' Total 66.0

Example 2 1. Porous sulphite tissue paper 9.0 2. 3% aluminum stearate, 5% ester gum, and 92% microcrystalline wax M. P. 145 F., by wt 422.0 3. One side clay coated paper 40.0

Total.A r11.0

4 u Example 3 A1. Porous sulphite .tissue paper 9.0

2. 3% aluminum stearate, 5% ester gum, and 92% microcrystalline wax M.-P. F., by wt 20.0 3. Supercalendered sulphite paper 17.0

Total 46.0

Example 4 Total e 56.0

Example 5 Porous sulphite tissue paper- 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

' heat-sealable containers Example 6 i. Porous sulphite tissue paper 9.0 2. 97% by wt. microcrystalline wax M. P. 14S-7 F. and 3% by wt. .aluminum stearate l-- 19.0 3. Highly hydrated greaseprooi sulphite paper 17.0

Total 45.0

Example 7 v 1. Porous sulphite tissue paper 9.0

2. 3% aluminum stearate, 5% ester gum, and 92% microcrystalline wax M. P. 145 F., by wt 30.0 3. 0.016 in. machine calendered paper board 200.0

'rom 239.()

Our sheet materials are suitable for making and for packaging or wrapping any desired articles. Overlapped portions of the container or wrapper can be sealed by applying heat and pressure thereto as previously explained to form a very strong and tight seal. Inasmuch as our intermediate lm is not exposed, any materials packaged in our sheet material will not come into direct contact with the sealing fllm. In the previous types of externally coated heat-scalable sheet materials there was a tendency for these coatings to peel and crumble,

particularly at low temperatures prevailing for packaging and storing frozen foods, thereby contaminating the packaged foods. Our inner film is protected against damage, puncture, abrasion, adhesion of foreign substances, dirt, etc. by being covered by the porous sheet. Our sheets will not block or stick together since they` have no external coatings to cause adhesion. Both outer sides of some of our laminated sheets may be printed if desired. Usually only the exposed face of the base sheet is printed for packaging purposes.

Our combined sheet material acteristics which make it highly suitable as a container or wrapper for foodstuffs. It is highly moistureproof in both flat condition as well as after folding or scoring as the adhesive layer is supported by the porous sheet and is highly flexible, water and moistureproof. Our composite sheet is very pliable, flexible and easily folded. It has a little spring-back as compared with ordinary sheets when folds are made during packaging operations, in both manual and automatic packaging operations. When our sheet material is folded it tends to remain in the folded condition and does not resist bonding when seams are formed. Thus a minimum of heat is required for forming seals at the overlapped portions and the packaged contents are thus less likely to be deteriorated by the heat applied. Some materials such as yeast, for example, are very sensitive even to slight heat. Our sheet materials provide very eifective heat-sealable wrappers for yeast. Such yeast packages have excellent keeping qualities and longer shelf life than prior packages. On account of the flexibility and continuity of our illm our sheet material produces square and well formed packages. No disruption of the intermediate film will occur at the corners of the folds when packages are made as the porous sheet serves to reinforce and protect the intermediate film in those areas where the previous types of exposed coatings are liable to has many "char- 8 crack and peel during folding and creasing operations. losing their protective qualities.

Numerous modifications and other combinations of laminated sheet materials may be made ut the essential features of our invention. For example, instead of using a single base sheet we may utilize a suitable base sheet made of two or more plies of sheet materials selected so as to have any desired characteristics. The 4base sheet may also be provided with a continuous thermoplastic 111m on both faces to which a relatively porous sheet is united so that such triple-ply sheet will be heat-sealable on either face.

Our sheet materials are suitable for forming heat-sealable bags, receptacles, containers, cartons. tapes, labels, tags, pouches, envelopes. tubes, gaskets, caps. bottle closures and the like. In making bags, cartons and receptacles of any kind the base sheet can constitute the exposed surface of the package, while the porous sheet provides the inner surface of the container which contacts the materials packaged therein. After packaging the materials the open ends can be readily sealed by application of heat and pressure, either contacting superposed portions of the porous sheet in face to face contact or by sealing overlapped portions in the same manner.

tion utilizing the essential and signiicant features of our invention as fully disclosed herein. It is intended to include such modifications within the scope of the appended claims.

We claim:

1. A laminated container having wall portions thereof formed of a heat-scalable sheet comprising in adhered condition a relatively dense base sheet material, an intercalated continuous flexible thermoplastic film and a thin relatively p`orous tissue sheet adhered to said film, said film not substantially penetrating said sheet materials and being of a predetermined basis weight and confined to the inner surface of the porous sheet, the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, selected portions of said sheet being overlapped and having at least one porous tissue surface at the interfaces of the overlapped area and adhered together by an adhesive film generated at the interfaces of said overlapped portions byapplication of heat and pressure to said selected portions and migration of said intercalated film through said porous sheet to the surface area thereof.

2. A laminated container having wall portions thereof formed of a heat-sealable sheet comprising in adhered condition a base sheet material of cellulosic material having a relatively dense structure, an intercalated continuous flexible thermoplastic lm and a thin relatively porous tissue sheet adhered to said film, said film not substantially penetrating said sheet materials and being of a predetermined basis weight and confined to the inner surface of the porous sheet, the outer exposed surface of said porous sheet being substantiallyunchanged from its original 3. A laminated container having wall portions thereof formed of a heat-sealable sheet comprising in adhered condition a base sheet material of metal foil, an intercalated continuous flexible thermoplastic film and a thin relatively porous tissue sheet adhered to said film, said film not substantially penetrating said sheet materials and being of a predetermined basis weight and confined to the inner surface of the porous sheet, the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, selected `portions of said sheet being overlapped and having atleast one porous tissue surface at the interfaces of the overlapped area and adhered together by an adhesive film generated at the interfaces of said overlapped portions by application of heat and pressure to said selected portions and migration of said intercalated film through said porous sheet to the surface area thereof.

4. A laminated container having wall portions thereof formed of a heat-scalable sheet comprising in adhered condition a relatively dense base sheet material, an intercalated continuous flexible thermoplastic film comprising microcrystalline wax and a thin relatively porous tissue sheet adhered to said film, said film not substantially penetrating said sheet materials and being of a predetermined basis weight and confined to the inner surface of the porous sheet, the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, selected portions of said sheet being overlapped and having at least one porous tissue surface at the interfaces of the overlapped area and adhered together by an adhesive film. generated at the interfaces of said overlapped portions by application of heat and pressurelto said selected portions and migration of said intercalated film through said porous sheet to the surface area thereof.

5. A laminated container having wall portions thereof formed of a heat-scalable sheet comprisingin adhered condition a relatively dense base sheet material, an intercalated continuous flexible thermoplastic film comprising a Wax and an elastomer and a thin relatively porous tissue sheet adhered to said film, said lm not substantially penetrating said sheet materials and being of a predetermined basis weight and confined to the inner surface of the porous sheet, the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, selected portions of said sheet being overlapped and having at least one porous tissue surface at the interfaces of the overlapped area and adhered together by an adhesive film generated at the interfaces of said overlapped portions by application of heat and pressure to said selected portions and migration of said inter- 10 calated film through said porous sheet to the said surface area thereof.

6. A laminated container having wall portions thereof formed of a heat-sealable sheet comprising in adhered condition a relatively dense base sheet material, an intercalated continuous flexible thermoplastic film comprising a wax and rubber 1 to 30% by Weight and a thin relatively porous tissue sheet adhered to said film, said film not substantially penetrating said sheet materials and being of a predetermined basis weight and confined to the inner surface of the porous sheet, the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, selected portions of said sheet being overlapped and having lat least one porous tissue surface at the interfaces of the overlapped area and adhered together by an adhesive film generated at the interfaces of said overlapped portions by application of heat and pressure to said selected portions and migration of said intercalated film through said porous sheet to the surface area thereof.

'7. In a container formed of a heat-scalable sheet material having in adhered condition a relatively impermeable base sheet material, an intercalated continuous fiexible thermoplastic film and a thin relatively porous tissue sheet adhered to said film, said film being of predetermined basis weight and not substantially penetrating said sheet materials, and being confined tc the inner surface of the porous sheet, the outer exposed surface of said porous sheet being substantially unchanged from its original characteristics, a seam formed of selected portions of said sheet material positioned in overlapped relation to bring portions of said porous sheet. in face to face contact and adhered together by an adhesive film generated at the interfaces of said overlapped portions by application of heat and pressure to said selected portions and migration of said intercalated film through said porous sheet to the surface area thereof.

ROBERT A. FARRELL. CHARLEY L. WAGNER.

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

UNITED STATES PATENTS Number Name Date 2,048,123 Howard July 21,1936 2,154,083 Bergstein Apr. 11,V 1939 2,184,139 Cunnington Dec. 19, 1939 2,371,314 Rhodes et al. Mar. 13, 1945 2,333,330 Moore Nov. 2, 1943 2,054,116 Abrams et al. Sept. 15,1936 1,937,518 Henderson et al. Dec. 5, 1933