US3410392A - Composite side wall and resealable sealed package containing corrosion preventive means - Google Patents

Description

Nov. 12, 1968 w. A. HERMANSON 3,410,392

COMPOSITE SIDE WALL AND RESEALABLE SEALED PACKAGE CONTAINING CORROSION PREVENTIVE MEANS Filed Aug. 21, 1964 //VVE/VTUR WILLIAM A. HERMANSON ATTORNEYS United States Patent COMPOSITE SIDE WALL AND RESEALABLE SEALED PACKAGE CONTAINING COR- ROSION PREVENTIVE MEANS William A. Hermanson, 1284 Beacon St., Brookline, Mass. 02146 Filed Aug. 21, 1964, Ser. No. 391,099

12 Claims. (Cl. 206-46) ABSTRACT OF THE DISCLOSURE A composite side wall for use in forming heat sealed and heat resealable packages is provided with the side wall comprising a paper web having a surface coating of substantially uniformly distributed polyethylene particles mixed with corrosion inhibitor granules in a dry film of a non-heat scalable binder. The polyethylene particles havea particle size of at least 8 microns. Preferably the side wall is used to form a package with similar side wall material to enclose metal parts and protect them against corrosion.

The present invention relates to novel and improved heat sealed packages and more particularly to packaging materials and resulting packages which are useful to protect metal parts against corrosion and which can be resealed after opening.

Heat sealed packages for storing and protecting metal parts such as hardware items and machine parts are known. Often such packages contain a heat sealed bonding layer carrying well known vapor phase inhibitors or vapor phase corrosion inhibitors known by the abbreviations V.P.I. and V.C.I. which are capable of imparting corrosion protective atmospheres about metal parts in sealed packages and which will be referred to hereinafter as corrosion inhibitors. These corrosion inhibitors normally volatilize above their normal vapor pressures at room temperature (23 C.) of about 0.00016 mm. of mercury. They are also highly reactive and particularly sensitive to heat.

Prior art heat sealed packages have often used an acrylic or other high temperature drying binder film in which the corrosion inhibitors are mixed and spread over the surface of a packaging material to be heat sealed. In a later step, acrylic films are often dried and/or heat sealed at temperatures which tend to rapidly volatilize the corrosion inhibitors mixed therewith, thus, tending to shorten the corrosion protective life of the corrosion inhibitors in a sealed package. In some cases, the binder carrying the corrosion inhibitors tends to react with the corrosion inhibitors, thus tending to shorten useful life of heat sealed packages.

Many known corrosion resistant packages are nonsealable after initial opening since heat curing or thermosetting binders or adhesives are used to form the heat sealed portions of the packages. This feature can be a distinct disadvantage as in the case where a plurality of items such as ball bearings are packaged in a single package, and only one item is to be used while the others are to be maintained corrosion free for a period of time. Once such packages are opened to remove a single component, all other components are exposed to the atmosphere.

An important object of this invention is to provide a relatively inexpensive, resealable, heat sealed package.

Another important object of this invention is to provide a heat sealed package in accordance with the preceding object which prevents corrosion of metal components sealed therein for long periods of time.

Another object of this invention is to provide a heat sealed package in accordance with the preceding objects ice which has high bond strength at sealed edges and can be easily manufactured at high production rates.

According to the invention, a heat sealed bond is formed in a heat sealed package by the use of discrete particles of a thermoplastic polyethylene lying on a first surface of a web to be sealed. The polyethylene particles are heat sealed to a second similar web having polyethylene particles thereon or to a sheet having a polyethylene surface layer. In the preferred embodiment of this invention, the heat sealed corrosion resistant, resealable package has a first side wall of a web of a cellulose fiber containing material having discrete polyethylene particles commingled with granules of a corrosion inhibitor and bound together by a non-heat scalable, film forming binder forming a surface layer over one face of the Web. A second side wall is a composite sheet made up of a plastic polyester outer layer and a polyethylene inner layer and is bonded to the first web along marginal overlapped portions of the web and sheet by a heat sealed joint. Metallic parts are incorporated into the package so formed prior to closing the package by heat sealing and are protected by the corrosion inhibitor.

In still another embodiment of the invention, the first web is bonded to a second identical web with the polyethylene particle layer of each web in facing relationship to form a heat sealed, resealable corrosion resistant package.

These and other features, objects and] advantages of this invention will be better understood and appreciated from the following detailed description of one embodiment thereof selected for purposes of illustration and shown in the accompanying drawings in which:

FIG. 1 is a perspective view of a preferred embodiment of a package of this invention taken through a plane half-way between the ends thereof;

FIG. 2 is a perspective view of a side wall thereof;

FIG. 3 is a perspective view of a second side wall thereof; and

FIG. 4 is a cross sectional view through a heat sealed seam of an alternate embodiment of this invention.

With reference now to the drawings and particularly FIG. 1, a resealable, heat sealed package 10 of this invention is shown containing a plurality of metallic components such as steel ball bearings 15' with the package preventing corrosion thereof. Only one half of the package 10 is illustrated in order to simplify the drawings, however, the half not shown is identical to the half shown. The package 10 has a first substantially non-self supporting, rectangular, moisture resistant composite side wall 16 heat sealed at .a continuous, rectangular marginal edge seam 21 to a second substantially non-self supporting, transparent, composite sheet, plastic side wall 17. A pouch 20 is provided preferably centrally located in the package 10 and carries a corrosion inhibiting atmosphere for the ball bearings 15 or other metal parts.

The composite side wall 16 preferably has a first thin outer web or layer 11 which is substantially vapor resistant and not reactive with the polyethylene or the corrosion inhibitors used. The web 11 is preferably a paper or cellulose fiber containing material such as a 65 lb. neutral kraft paper web which is treated so that its pH remains neutral over long time periods. Other papers such as stretchable paper including creped or Clu-Pak paper treated with moisture penetration resistant materials can also be used. The particular thickness of the paper web 11 may vary considerably but preferably lies within the range of from 0.002 to 0.010 inch.

As best seen in FIG. 2, the side of the paper web 11 which is heat sealed carries a thin coating 12 comprising a mixture of polyethylene particles and corrosion inhibitor granules in a binder. The binder may be any nonheat scalable film former which does not react with the polyethylene or the volatile corrosion inhibitor granules. Hydroxyethylcellulose is particularly useful as a binder since it efliciently acts as a vehicle to disperse the par ticles uniformly over the surface of the paper Web and will dry and leave a binder film over the paper web at temperatures well below those which cause undesired volatilization of the volatile corrosion inhibitors. Other nonheat sealable film forming, non-corrosive binders useful in this invention include but are not limited to methyl- .cellulose, starch, natural gums, lattices, such as natural rubber latex, or mixtures of the above.

-The polyethylene particles are preferably in discrete, generally spherical or irregular non-elongated ground forms having particle sizes passing through screens down to 120 mesh corresponding to particle sizes of from 8 to 125 microns. While larger particles may be used, it is preferred to use particles within the stated range to achieve uniformity of distribution of the particles and provide large particle surface areas for bonding. Preferably the melting point of the polyethylene particles used lies within the range of from about 220F. to 300F. It has been found that the bond strength of the heat sealed seam at the marginal edge seam 21 can be varied by using mixtures of different melting point polyethylene particles in the layer 12. For example, when the polyethylene particles of the coating layer 12 all have a melting point of approximately 280F., a particular bond strength results. When the polyethylene particles all have a melting point of 220F., a lower bond strength results. By using a mix ture of 50% by weight polyethylene particles having a melting point of 220F. and 50% by weight of the mixture of polyethylene particles having a melting point of 280F. a bonding strength will result approximately intermediate the bonding strength of the two examples pointed out above. This feature is important in providing preselected bond strengths in resealable packages in accordance with this invention. By using polyethylene particles having a selected melting point or by using mixtures of polyethylene particles of different melting points, a bonded joint formed can be pulled apart by hand without destroying the Web 11 and such joints can be rescaled repeatedly by reapplication of heat and pressure as will be described. The non-thermoplastic volatile corrosion inhibitor granules useful in the process of this invention may be any of the well known vapor phase corrosion inhibitors which include for example, volatile amine carboxylates such as cyclohexylammonium benzoate, di-isopropylammonium benzoate, monoethanolamine benzoate, Z-butylamine benzoate, diisopropylammonium succinate; organic amine nitrite salts and mixtures thereof such as dicyclohexylamine nitrite, morpholine nitrite, and numerous other organic amine nitrates and mixtures thereof, and mixtures thereof with stabilizing agents and the like. Other useful corrosion inhibitors include nitro-thiophene compounds such as 2-nitr0-thi0phene and 2,5-di-nitrothiopene. Mixtures of organic amides with inorganic metal nitrites such as urea and sodium nitrites may also be used. Such materials are disclosed in US. Patent No. 2,829,080.

Polyethylene particles are preferably from 10% to 50% by weight of the corrosion inhibitor granules. The mixture of polyethylene particles and corosion inhibitor granules is in sufficient quantity in the binder to provide a dry coated Weight on the paper web of corrosion inhibitor granules of at least one gram per square foot. Preferably the binder acts as a coating vehicle and is present in sufficient amount to provide a desired coating viscosity to a mixture of particles and granules depending on the conditions of manufacture of the side Wall 16. Preferably the mixture of binder, polyethylene particles and corrosion inhibitor granules are sprayed or otherwise coated on the dry paper web 11 and the side wall 16 thus formed is calendered. The corrosion inhibitor granules are generally friable and thus often break down during calendering so that their initial size is not critical.

The second side Wall 17 of the package 10 is preferably a generally rectangular composite sheet preferably having the same outer peripheral configuration as the side wall 16. A first outer layer of the composite sheet 17 is preferably a non-self supporting thin sheet 14 of a polyester preferably having a thickness of from 0.001 to 0.005 inch. The second or inner layer of a composite sheet 17 is preferably a non-self supporting thin extruded or calendered polyethylene sheet 13 bonded tothe underlying polyester sheet.

The polyester sheet 14 provides vapor penetration resistance as well as mechanical strength to the package 10 as it resists tearing of the completed package. Other high mechanical strength or tear resistant materials can be used for the polyester material including, but not limited to metal foils and other plastics. The polyethylene sheet 13 provides a bonding layer for sealing to the coated layer 12 and also acts as a vapor barrier. The thickness of polyethylene layer 13 is preferably between 0.001 and 0.005 inch.

The'package 10 of this invention can be formed by conventional heat sealing techniques preferably in automatic filling and heat sealing machines. Preferably elongated strips of the side walls 17 and 16 are fed into a conventional Stokes and Smith heat sealing and filling machine with layers 12 and 13 facing each other. Individual packages 10 are formed successively at high production rates with filling of the packages with ball bearings 15 or other metal components prior to the final heat sealing of the continuous edge seam 21. The continuous seam 21 is preferably heat sealed at temperatures of from 275 to 375 preferably applied over time periods of from 0.5 to 60 seconds at pressure of from 40 to psi. The heat sealing operation forms a strong, resealable bond at seam 21 sealing the package 10 about its peripheral flanged edges and encloses a pouch or space 20 within which the ball bearings or other metal parts are held in a corrosion resistant atmosphere. The heat sealing temperature is not applied for a sufiiciently long enough time to cause deleterious breakdown of the vapor phase corrosion inhibitor granules. The ranges of time, tempera ture and pressure are interrelated and may vary considerably depending on the particular package formed.

.In still another embodiment of this invention, as best illustrated in FIG, 4, the package 10 may comprise two side walls of the type shown at 16. In this case the layers 12 are placed in face to face contact with their peripheral edges overlapping and are heat sealed together as previously described. Here again, a resealable corrosion resistant package is formed. In a modification of the package of FIG. 4 one of the sidewalls can comprise a composite paper web 11 having a coating layer such as 12 but without corrosion inhibitor granules. Thus, the coating layer 12, made up of polyethylene particles and the binder film acts to form a bond during the heat sealing of the package.

In a specific embodiment of the package of FIG. 1, paper web 11 is a 65 lb. neutral kraft paper having a thickness of 0.005 inch, layer 12 has a thickness of approximately .004 inch and comprises a 50% mixture of polyethylene particles having a particle size of microns and a melting point of 260280 F., and 50% polyethylene particles having a particle size of microns and a melting point of 220240 F. The polyethylene particles are mixed with 50% by weight of dicyclohexylammonium nitrate which has a vapor pressure at 24 C. of about 0.00016 mm. of mercury. A hydroxyethyl-cellulose film binder is present in sufficient amount to provide a dry coated weight of the nitrite of 1 gram per square foot of paper Web 11. The side wall 17 comprises a 0.003 inch thick Mylar polyester sheet 14 and polyethylene sheet 13 has a thickness of 0.003 inch. The sheets 16 and 17 are each 3" by 4" in size and 6 small steel bearings are sealed within the sheets as shown in FIG. 1 by applying a temperature of 375 F. for 5 seconds about a marginal seam bonding edge 21 having a width of approximately inch. The resultant package prevented corrosion of the steel ball bearings even in moist atmospheres for long periods of time. Composite sheet 17 was transparent so that the condition of the steel ball bearings could be visibly examined. The resultant package 10 was reopened by prying apart the side walls 16 and 17 with a finger nail and then reclosed by sealing as previously described. Even after a second and third heat sealing step, the package continued to keep the enclosed steel ball bearings in good condition and prevented corrosion.

While specific embodiments of this invention have been shown and described, many variations thereof are possible. For example, the specific configuration of the package 10 and the pouch 20 can vary considerably. Circular, irregular, oval or other outer peripheral configurations can be used for the side walls. The size and weight of the enclosed metal parts can vary considerably. It is a feature of this invention that the heat sealed bond formed between the side walls can be varied to provide sufficiently strong bonds for any particular metal parts. For example, if heavy metal parts are used, preferably higher melting point polyethylene particles are used to increase the bond strength. The particular width of the seam 21 can Vary with wider seams providing increased seam strength. In some cases, the heat sealed seam 21 or portions thereof may be spaced slightly inwardly of the extreme outer edge of the side walls to form tabs of the extreme outer side wall edges. Such tabs are useful in opening the package 10 by manually pulling apart the side walls 16 and 17 at one or more points.

Therefore, this invention is to be limited only by the spirit and scope of the appended claims.

What is claimed is:

1. A composite side wall for use in forming heat sealed, resealable packages, said side wall comprising:

a paper web having bound thereto a Surface coating of substantially uniformly distributed polyethylene particles mixed with corrosion inhibitor granules in a dry film of a non-heat scalable binder,

said polyethylene particles having a particle size in the range of from about 8 to about 125 microns.

2. A composite side wall in accordance with claim 1 wherein said polyethylene particles comprise from about 10 to 50% by weight of said corrosion inhibitor granules.

3. A composite side wall in accordance with claim 1 wherein said polyethylene particles comprise a mixture of polyethylene particles having at least two different melting points and said coating has a weight of at least 1 gram per square foot.

4. A composite side wall for use in forming heat sealed, resealable packages in accordance with claim 1 wherein said binder is selected from the group consisting of hydroxyethylcellulose, methylcellulose, starch, natural gums and rubber latex.

5. A filled resealable heat sealed package comprising a first side wall and a second side wall:

said first side wall comprising a cellulose fiber web,

said web having bound thereto an inner face comprising a mixture of polyethylene particles having a particle size of at least 8 microns and corrosion inhibitor granules dispersed in a dry film of a nonheat scalable binder,

ti said web being bonded to said second side wall by a heat sealed joint formed from said polyethylene particles.

6. A filled resealable package in accordance with claim 5 wherein said polyethylene particles comprise a mixture of polyethylene particles having at least two different melting points.

7. A filled resealable package in. accordance with claim 5 wherein said polyethylene particles comprise from about 10% to by weight of said corrosion inhibitor granules.

8. A resealable, corrosion resistant, heat sealed package for metal materials, comprising a first side wall and a second sidewall:

said first and second side walls each comprising paper webs,

said webs each having bound thereto an inner face comprising a mixture of polyethylene particles having a particle size of at least 8 microns and corrosion inhibitor granules disperse-d in a film of a nonheat sealable binder,

said webs being bonded together at heat sealed seams formed by adjacent portions of said inner faces.

9. A resealable, corrosion resistant, heat sealed package in accordance with claim 8 wherein said polyethylene particles comprise a mixture of polyethylene particles having different melting points in the range of from 220 F. to 300 F.

10. A resealable, corrosion resistant, heat sealed package for metal materials, comprising:

a first side wall and a second side wall,

said first side wall comprising a paper web having bound thereto an inner face comprising a mixture of polyethylene particles having a particle size of at least 8 microns and corrosion inhibitor granules dispersed in a film of a non-heat scalable binder,

said second side wall comprising a composite sheet having an outer reinforcing layer and an inner polyethylene layer forming an inner face of said second side wall,

said first and second side walls being heat sealed together with portions of said inner faces in contact with each other to define a space for said metal material between said side walls.

11. A resealable, corrosion resistant, heat sealed package in accordance with claim 10 wherein outer reinforcing layer is a polyester plastic material.

12. A resealable, corrosion resistant, heat sealed package in accordance with claim 10 wherein said polyethylene particles comprise a mixture of different polyethylene particles having different melting points in the range of from 220 F. to 300 F. and said inner face has a weight of at least 1 gram per square foot.

References Cited UNITED STATES PATENTS 2,582,037 1/1952 Hyde 26028.5 2,686,744 8/1954 Cornwell l61--26-0 2,829,080 4/ 1958 Fessler et al 161-l6-5 2,895,270 7/1959 Blaess 53-21 MORRIS O. WOLK, Primary Examiner. F. T. RUDIAK, Assistant Examiner.

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