EP0070721A2

EP0070721A2 - Package for highly viscous tacky materials

Info

Publication number: EP0070721A2
Application number: EP82303771A
Authority: EP
Inventors: Michael Frank English; Alto Nelson Stuckey, Jr.
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1981-07-20
Filing date: 1982-07-19
Publication date: 1983-01-26
Also published as: EP0070721A3

Abstract

A packaging container for viscous material (such as polyisobutylene) is featured by a scored blank having substantially no adhesion for said material, folded into a seamless tray disposed in an external sleeve and a covered box- like outer container.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in the construction and method of making a package for highly viscous tacky materials. More particularly, it relates to a container for such materials which utilizes a seamless laminated tray with good release characteristics disposed within a box.

2. Description of the Prior Art

Most highly viscous tacky polymers such as low molecular weight polyisobutylene are mixed and packaged "hot", e.g., greater than 125⁰C, so that the material will flow to some extent or at least be pourable. Containers for these types of materials must be able to withstand the hot packaging temperatures of approximately 150⁰C to 235⁰C and at the same time, permit the contents to be readily removed for final use.
These materials are presently packaged in expensive metal containers which are of much lighter weight than is desired for product protection and durability since the container must be peeled from the product in order to use the product. These containers are generally coated with a release coat which must be manually applied after the can is manufactured and is therefore generally of poor quality.
One approach to packaging such materials is shown in U.S. Patent 3,648,882 which teaches that low molecular weight tacky polymers may be readily removed from their containers by providing the container with a removable release agent-coated inner liner having a readily detachable bottom member.
Another approach to packaging these viscous tacky polymers according to U.S. Patent 3,837,375 is by hot filling an open-ended container having a liner comprising (1) heat stabilized nylon'coated with a silicone release agent; (2) an uncoated cellophane film; (3) a mineral pigment coated kraft paper overcoated with a silicone release agent; or (4) kraft paper coated with finely divided mica. This liner provides for ready release of the material from the container after warehouse storage and/or shipment to the processor of said viscous tacky material.
In these prior art structures that disclose the use of cylindrical drums which have bag type inner liner structures or cyclindrical liner sleeves which are supported within the cylindrical drum, the liners have release agents on their inner surfaces to permit the liners to be peeled away from the viscous material after it has cooled. With a bag type liner, it is not possible to peel the liner away from the cooled tacky viscous material to place the liner in a substantially flattened configuration to leave the viscous material free standing on the liner; rather, it is necessary to rip, tear or cut the lines in order to peel it away from the cooled viscous material. This can create problems in easily and completely freeing the viscous material from the liner. In this regard, if the bag structure were constructed from a substantially flat sheet of material which had a release coating thereon, it would be most difficult to seal the edges to provide a substantially leak-proof container as a result of the release coating on the surface of the sheet material. In other words, seams would be necessary and there is difficulty in adequate sealing of the seamed edges of a material when a release coating has been placed thereon. Furthermore, with cylindrical tube structures which have been used as liners, a seam must be provided between the tubular structure and a bottom which in turn can present problems of leakage or flow of the tacky viscous material when it is hot and poured into the liner. Furthermore, it is difficult to place a release coating on bags which have already been sealed, i.e., to coat the inside of a formed bag or tube structure with a release agent. Thus, it will be appreciated that with the prior art arrangements for packaging structures either seams were provided which might present problems with leakage control, or alternatively, if the liner structures were adequately sealed, there would be problems in adequately coating the inner surface of the liner to provide a release coating for facilitating removal of the liner after the viscous material has cooled.
It is an object of this invention to improve the packaging of highly viscous tacky materials which tend to cold flow at room temperatures.
It is a further object of this invention to provide a package for highly viscous tacky materials which is Ijaakproof and readily separated from the packaged material.

BRIEF DESCRIPTION OF DRAWING

The various objectives and features of the invention will be fully understood by reference to the accompanying drawings, which show a preferred embodiment thereof.

Figure 1 is a perspective view of a scored and unfolded blank;
Figure 2 is a perspective view of the scored blank, folded into a seamless tray;
Figure 3 is an exploded view of a preferred embodiment of the uncovered package of the invention showing a folded seamless tray, a support sleeve and an outer box;
Figure 4 is a partial cross-sectional representation taken along line 4-4 of Figure 5; and,
Figure 5 is a pictorial representation of the container of the invention.

SUMMARY OF THE INVENTION

It has been discovered that a scored blank, preferably a scored paper sheet (optimally kraft paper laminated to a corrugated board or fiber board) which has been surface treated with a release agent for tacky viscous material can be folded into a seamless tray which provides said release properties (Kiel release of less than 10 grams and preferably less than 5 grams), is suitable for disposition into a tray supporting member, e.g., a box or sleeve, is capable of leakproof retention of said material and provides freedom from contamination of the viscous material. One or more trays may be placed in supporting member which has suitable stacking strength, crush strength, and puncture resistance for storage and/or shipment. Preferably, the supporting member comprises a sleeve and a box with a cooperating cover, said sleeve disposed contiguous with the outer surface of the tray and the inner surface of the box.
Thus, the invention can be described as a packaging container for viscous material whish comprises a blank folded into a seamless tray, the inner surface of said tray having a Kiel release of less than 10 grams for the material to be packaged within said tray, a tray supporting member disposed about said tray and a cover for said tray whereby viscous material is contained within said tray. The scored blank usefully is a composite of a polymeric film adhered to a scored corrugated board. Preferably, the tray supporting member comprises an open ended member and an outer box, said open ended member adapted to be positioned external and contiguous with the outer surface of said tray and the inner surface of said box. To avoid contamination of the packaged viscous material, it is preferred further that the tray has shoulders adapted to cooperate the tray supporting member whereby said shoulders prevent any contained viscous material contact exposure to said tray supporting member.
As seen from the foregoing, the unique feature of the packaging container derives from the use of a substantially flat blank of material having a release coating en one side thereof. The blank of material is folded to provide a tray member having an integral bottom and upstanding sidewalls defining an open top end, the nature of the folding of the blank being such that the tray member is substantially free of seams through which tacky viscous material could flow when the tray member is filled. The folded tray member is adapted to be placed within a suitable support structure, such as a corrugated sleeve and/or an outer box structure for supporting the bottom and sidewalls of the tray member so that it will maintain its integrity when filled with tacky viscous material.
The use of such a substantially flat sheet material which is folded into a tray member is advantageous in a number of respects over prior art packaging structures for tacky viscous material. For instance, the outer peripheral margins of the flat sheet can be folded upwardly in a manner to define the upstanding sidewalls of the tray member so as not to provide any seams through which the tacky viscous material may leak or flow when poured into the tray member. Additionally, since the tray member is constructed from a substantially flat sheet, after the tacky viscous material has cooled and the tray member is removed from its supporting structure, the upstanding sidewalls of the tray member may simply be unfolded and placed in a substantially flat configuration to easily facilitate removal of the viscous material. That is, as the initial configuration of the blank of material was substantially flat, and was simply folded to define the tray member, when it is desired to use the viscous material the sidewalls of the tray member may simply be pulled away from the side of the viscous material and placed in a substantially flattened configuration with the cooled viscous material lying on top of the flattened blank of material. This capability facilitates easy removal of the viscous material when it is desired to use same.

DETAILED DESCRIPTION OF THE INVENTION

The container of this invention is suitable for use for such tacky polymers as polyisobutylene having a Staudinger molecular weight of 8,000 to 12,000,polybutenes having Staudinger molecular weights of about 3,000 to 6,000, low molecular weight butyl rubbers and halogenated butyl rubbers, low softening point hydrocarbon resins, adhesives, sealants and the like compounds which are normally not pourable at room temperature, but exhibit cold flow at room temperature and are sufficiently tacky to be removed from conventional containers only with difficulty.
The substantially flat blank should be capable of withstanding hot packaging conditions without degradation or softening to the point of adhering to the polymer being packaged. Various polymeric films have been found to be useful for this purpose. Typical of the types of the film which may be used are polyester films and heat stabilized nylon. Preferable, the polymeric film has a thickness of about 0.5 to about 5 mils; more preferably about 1 to about 3 mils.
A particularly suitable polyester film is the reaction product of ethylene glycol and terephthalic acid which is known to the trade by the duPont trademark "Mylar".
The term "nylon" as used herein in the specification and claims is used in its generic sense to mean long chain synthetic polyamides which have recurring amine groups. Illustrative examples of nylons suitable for use in the practice of this invention are Nylon 4 prepared from pyrrolidone; Nylon 66 prepared from condensation of hexamethylenediamine with adipic acid; Nylon 610 obtained from the condensation of hexamethylenediamine with sebacic acid; Nylon 6 obtained by polycondensation of caprolactam; etc. Aromatic polyamides are particularly well suited for use in the practice of this invention due to their excellent thermal properties.
Though any nylon film may be used in conjunction with the scored blanks, it is preferable that where packaging is carried out at elevated temperatures, e.g. 150-235⁰C, the nylon be a heat stabilized nylon illustrated by Nylon 6 which has the following physical properties: at 22⁰C, tensile strength of 12,000-15,000 psi, yield strength of 5,000-8,000 psi, tear strength of 70-100 gms., elongation of 400-600 percent, negligible solubility in water, crystalline melting point of 218°-220°C; at 150°C, tensile strength of 5,000-7,000 psi, yield strength of 1,500 - 2,700 psi, and elongation of 400-500 percent.
In the practice of this invention, it is preferred, due to economics, to use kraft paper, e.g. 50-100 pound grade which corresponds to a thickness of from 0.5 to 5 mils,as the scored blank; optimally heat laminated to a corrugated backing (usefully a single wall construction) with any suitable combination of flute design and liner board construction. Alternately, and also preferable is a construction wherein the tray is folded from a scored blank consisting of a release liner laminated to fiber board of suitable thickness (typically 0.033 inches) as by gluing with a phenol-formaldehyde resin.
The scored blank is surface coated with a release agent. Various release agents may be used in the practice of this invention. Preferably, the release agents are silicone fluids having a viscosity of about 10 to about 30,000 centistokes at 25⁰C, more preferably about 50-1,000 centistokes, most preferably 100 to 500 centistokes. The materials are well known to the art having carbon to silicon linkages such as disclosed in U.S. Patent Nos. 2,448,756, 2,484,595 and 2,541,137 which are incorporated herein by reference.
The silicone fluid is cured after application to a surface of the scored blank. Illustrative of a suitable silicone for the scored kraft paper blank is Akrosil NS-62-UBL-5-1 sold by Akrosil Corporation. The silicone fluids useful for the polymeric films are illustrated by Union Carbide and Carbon's L-45 series fluids and General Electric Co.'s SF 96 series fluids with both being available in a wide range of viscosities up to about 100,000 cs at 25°C, e.g., Union Carbide and Carbon's L-31 is a silicone fluid having a viscosity of about 35 cs. at 25°C.
It has been found that the thickness of the release agent coating is not critical. However, it is essential that the coating be continuous. For example, a.continuous coating whose thickness is in the Angstrom range will suffice, whereas a discontinuous coating of several mils will not release properly.
It is essential, however, that the release coating provide a release value of 2 to 10, preferably 5, grams as measured by a Kiel release tester.
In the practice of this invention, a simple flat sheet of kraft paper which has been surface treated with a suitable release agent such as a cured silicone is laminated to the surface of a scored corrugated board or fiber board. The corrugated or fiber board has been appropriately scored in such a way that as its ends are folded, a tray is formed which has the unique nature of containing no seams, joints, butts or other areas in which the tacky viscous material can leak out. The folded flaps may be held in place by means of a fastener such as a staple or yet folded into the outer box or support sleeve. This folded tray is then placed in a suitable outer corrugated box of such a construction as to impart the required stacking strength, crush strength, puncture resistance, etc. The folded tray may also be placed in a corrugated support sleeve both of which are placed into a simple outer box. Once the package is filled with said material, the outer box top is sealed by conventional means. One or more trays may be placed in an outer box as described below. Note that the tray overlaps the outer corrugated sleeve to prevent fiber contamination of the tray contents.
The outer box may be of any suitable design. However, it is preferred that the box lid completely extend over the entire box top so that paper fiber contamination of the product be minimized.
The kraft paper release agent need not be laminated to corrugated board. It itself may be adequate as an inner liner supported by itself or laminated to a fiber board. It may also simply comprise the inner surface of a suitable outer box.
This box is not restricted to polyisobutylene type resins for it is suitable as a package for hydrocarbon resins, atactic polypropylene, hot melt adhesives and the like.
In a preferred embodiment of this invention as shown in the drawings, the inner blank 10 of Figure 1 has a series of scored lines a-j, b-e, f-i, k-j-i-g, k-n, p-o, b-j-o-q, q-t, e-i-v-t, v-u, n-o-v-w, and g-w, which are folded along the scorings as follows: first fold along scored lines b-j-o-q and e-i-v-t; secondly, fold along scored lines k-j-i-g and n-o-v-w; thirdly, fold along scored lines a-j, f-i, u-v and o-p; fourthly, fold along scored lines k-n and g-w; and finally, each of the four folded sections defined by efgi, vtwu, abjk and npoq are positioned in overlapping fashion against each end of the seamless tray as indicated in Figure 2.
Looking further at Figure 2, the seamless tray 11 has opposing sides 12 and 13, ends 14 and 15 and bottom 16. By appropriately folding the scored blank, no seams exist at any of the corners of the tray. Further, the blank is preferably cut to provide areas defined by cdeb, klmn, qrst and ghxw so that shoulders 17, 18, 19, 20 are formed overlap the sleeve member and thereby prevent contamination of the viscous material by exposure to the end of the supporting sleeve 21 (as seen in Figure 3). Shoulder 20 has been further folded to provide the lip 22, which is the optimal configuration for all shoulders, thus achieving maximum protection from supporting sleeve contamination.
In Figure 3, the exploded representation of the uncovered package or container of the invention shows the seamless tray 11 with its lipped 22 shoulders 17 and 20 positioned above support sleeve 21 (usefully of corrugated paper) and cooperating outer box 23 having sides 24, 25, 26 and 27 with bottom 28.
Referring now to Figure 5, the cooperating outer box 23 has a cover 24, which thereby fully contains the viscous material. Although in use the seamless tray is never filled fully with viscous material, it is desirable to coat the inner surface of the cover 24 with a release coating to avoid any tendency of the viscous material to adhere to said cover in the event that it is exposed thereto.
Figure 4 shows in partial cross-section the covered container of Figure 5 along dotted lines 4-4.
Cover 24, which extends over the side of box 23, is seen to lie directly in contact with shoulder 20 of the seamless tray 11, more particularly the shoulder 20 of end wall 15 of said tray 11. The sleeve member 21 is positioned at its upper end between the lip 22 of shoulder 20 and tray portions 29 and 30 which are represented by those liner areas fig and fei of Figure 1, respectively.
In view of the foregoing, the preferred structure of the packaging container of this invention for viscous materials comprises an outer support member having means defining a closed bottom and upstanding sidewalls and an open top end, and further including means for closing the open top end thereof; and an inner tray member placed within said outer support member to be supported thereby, said inner tray member having a bottom wall and integral upstanding sidewalls, and an open top end into which viscous materials may be placed, said bottom and integral sidewalls of said tray member having a release agent on the interior walls thereof so as to be peelable away from said viscous material after said viscous material has been placed in said tray member, said bottom and integral sidewalls of said tray member being folded from a substantially flat blank of material in a manner so as to be free of seams through which viscous material may flow when placed therein, and folded so that said sidewalls may be peeled away from said viscous material after said tray member has been removed from said outer support structure by unfolding said blank of material into a substantially flattened configuration to facilitate easy removal of said viscous material.
Thus the invention is practiced by a method of packaging viscous materials which comprises the steps of:

(a) providing a substantially flat blank of material having a release coating on one side thereof;
(b) folding said substantially flat blank of material into a tray member having a bottom and integral upstanding sidewalls defining an open top end, said substantially flat blank being folded so as to be free of seams through which viscous material may leak when placed in said tray member, and so that said release coating is on the interior surfaces of said tray member;
(c) placing said tray member in a supporting structure to support said bottom and sidewalls of said tray member; and
(d) filling said tray member through said open end with viscous material at a hot packaging temperature whereby said tray member may be removed from said supporting structure after said viscous material has cooled and said upstanding sidewalls of said tray member may be peeled away from said cooled viscous material by unfolding said tray member into a substantially flat configuration to thereby facilitate easy removal of said viscous material.

The package and the method recite the preferred feature that the inner tray or liner member is constructed from a substantially flat blank of material by folding of same so as to be free of seams through which the tacky material may leak and yet which may be peeled away from the viscous material after cooling by unfolding the sidewalls into a substantially flat configuration so that the cooled viscous material will simply lie on the substantially flattened blank and may then be easily removed therefrom and used as desired. As no seams are provided during the folding operation, the viscous material will not leak from the tray member. At the same time, when it is desired to remove the viscous material and use same, it is only necessary to remove the tray member from its supporting structure and then unfold the sidewalls and place same in a substantially flat configuration. This latter step of unpeeling is of a much simpler nature than prior art methods which require ripping, tearing or cutting of the liner.
A further advantage resulting from use of the substantially flat sheet which is folded into a tray member is the fact that it permits easy automation of the equipment for constructing the packages for the viscous material and for filling of same. For instance, in the preferred embodiment of the present invention in which the release coating is applied to a corrugated cardboard or fiberboard, the blank may be easily folded in a manner to have an integral bottom and upstanding sidewall and which has sufficient rigidity to maintain its shape so that it may thereafter be easily placed within a supporting structure having the same general configuration as the folded constructed tray member. Such folding operations of a blank of material having the release coating thereon may be performed with conventional automated equipment. Likewise, the placement of the constructed tray member within a suitable supporting structure may be performed with automated equipment since the constructed tray member may simply slide or drop into the supporting structure. Further, li^p portions on the upper end of the tray may be provided to overlie the edges of the supporting structure to prevent contamination. Likewise, the filling of the tray member after placement within the supporting structure may be accomplished with automated equipment as well as the placement of a suitable cover thereover. With the prior art arrangements, the construction of the bag or cylindrical liners and the placement of same within the cylindrical drum with the upper edge of the liner folded over the upper edges of the cylindrical drum could not easily be accomplished with automated equipment.
' A still further advantage in accordance with the present invention relates to the fact that kraft paper having a release coating thereon may be utilized for the liner structure which is less expensive than conventionally used nylon liners which are release coated. While kraft paper having a release coating thereon has been utilized or proposed in the prior art, such prior art structures, as noted above, are of a cylindrical nature and thus present a problem of seaming of same so as to prevent any leakage. While this undoubtedly could be accomplished, it could only be accomplished at a relatively substantial expense in comparison to simple folding of a substantially flat blank into a tray member having a bottom and integral upstanding sidewalls. Thus, the present invention allows for a reduction in cost.
The invention in its broader aspect is not limited to the specific details shown and descibed and departures may be made from such details without departing from the principles of the invention and without sacrificing it chief advantages.

Claims

1. A packaging container for viscous tacky polymers or other materials which have a tendency to cold flow at ambient conditions, with or without added pressure, comprising:

(a) a seamless inner tray composed of a scored liner which has been surface treated with a release agent for tacky viscous material;

(b) a single or multiwall corrugated support sleeve into which the inner tray is inserted;

(c) an outer box which serves as a container for the tray and support sleeve.

2. The packaging container of claim 1 made free of fiber contamination by the inner release tray folding over the top edges of the support sleeve and locking between the sleeve and the outer box.

3. The packaging container of claim 1 wherein the scored liner is a sheet of paper, either laminated to a corrugated board or to a fiber board and which has been treated with a suitable release agent.

4. The packaging container of claim 1 wherein one or more trays are placed in the outer box (c) which has suitable strength, crush strength and puncture resistance for storage and/or shipping.

5. The packaging container of claim 1 wherein the laminate for the scored liner is a silicone treated (and cured) kraft paper having a Kiel release of less than 10 grams.

6. The packaging container of claim 1 wherein the laminate for the scored liner is a polymeric film such as a polyester or heat stabilized nylon, and the polymer is treated with a suitable cured release agent having a Kiel release of less than 10 grams.

7. The packaging container of claim 1 wherein the cover for the outer box extends completely over the entire outer box top to minimize paper fiber contamination of the product contained therein.