WO1998019852A1

WO1998019852A1 - Process for packaging large blocks of cold-formable pressure-sensitive adhesives and resultant products

Info

Publication number: WO1998019852A1
Application number: PCT/US1997/018294
Authority: WO
Inventors: Ali Berker; Jimmie L. Echols; Richard H. Johnson; Chung I. Young
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1996-11-05
Filing date: 1997-10-13
Publication date: 1998-05-14
Also published as: AU4898197A

Abstract

Enveloping a unitary block of a cold-formable, suspension polymerized, pressure-sensitive, acrylate adhesive weighing at least 5 kg within a melt-blendable thermoplastic film. The adhesive is packaged without heating the adhesive block, without actively cooling the thermoplastic film, and without contributing to the thermal or mechanical history of the adhesive. The film covered adhesive block is placed within a rigid container for controlling deformation of the adhesive block caused by the normal creep and cold flow associated with suspension polymerized pressure-sensitive acrylate adhesives under ambient conditions.

Description

PROCESS FOR PACKAGING LARGE BLOCKS

OF COLD-FORMABLE PRESSURE-SENSITIVE ADHESIVES

AND RESULTANT PRODUCTS

FIELD OF THE INVENTION

The invention relates to methods of packaging pressure-sensitive adhesives and the resultant packaged adhesive. More specifically, the invention relates to methods of packaging pressure-sensitive adhesives within a melt-blendable, nontacky, polymeric film.

BACKGROUND

Thermoplastic hot melt adhesives are commonly formed as pillow-shaped pieces which are packaged within bags, sacks or cartons for shipment. The pillows are frequently coated with a nontacky substance to prevent the pillows from adhering to each other. Such coatings have proven effective when used in connection with thermoplastic adhesives having a relatively high softening point (i.e., those having a softening point above about 150 °C as measured by ASTM E28-58T), but have demonstrated less than satisfactory performance when used in connection with low softening point thermoplastic adhesives (i.e., those having a softening point below about 120 °C as measured by ASTM E28-58T).

Hot melt adhesives are also commonly formed as large blocks which are cast directly into plastic bags or release treated containers. While generally effective for protectively housing such adhesives during transportation and storage, such packaging adds significant expense due to the specialty design of such release treated containers, and/or requires extrication of the tacky adhesive from the packaging material, to which it has adhered, prior to insertion of the adhesive into an adhesive coater.

Commercial applicability of this general packaging technique can be improved by encasing the adhesive in a material which is "compatible" with the adhesive composition. For example, German Patent No. 36 25 358 to Hausdorf discloses wrapping blocks of hot melt adhesive in a thermoplastic packaging material, specifically copolyamide films, having a melting point of about 120 °C to 150 °C, and then feeding both the adhesive and the copolyamide film into an adhesive coater. The copolyamide film is used to prevent the hot melt adhesive from sticking to the sides of the adhesive coater. However, due to the high melting point of the thermoplastic film materials disclosed by Hausdorf, this packaging technique mandates the use of temperatures well in excess of 120 °C when coating the adhesive and is therefore of limited use in various applications.

Hatfield et al. (United States Patent No. 5,373,682) discloses pumping a molten hot melt adhesive directly into a compatible cylindrical plastic tube which is in contact with a heat sink. While generally effective for producing a film-coated mass of hot melt adhesive, the need to continuously maintain the cylindrical plastic tube in contact with a heat sink until the temperature of the adhesive is reduced below the softening point of the packaging material significantly complicates the process, and increases costs.

Rouyer et al. (United States Patent No. 5,257,491) discloses packaging a plurality of hot melt adhesive pillows within a compatible plastic packaging material wherein the packaging material has a softening point of less than 120 °C. The packaging process disclosed by Rouyer et al. includes the steps of solidifying an independent and distinct portion of a thermoplastic adhesive composition, and surrounding the solidified adhesive portion with a compatible plastic packaging material.

Rouyer et al. mentions that a single larger portion of a hot melt adhesive can be packaged by this technique, although Rouyer et al. specifically references an upper size limit of 4kg, presumably due to the excessive time and effort required to cool larger masses to a temperature at which the adhesive mass can be placed within the low softening point plastic packaging material. Rouyer et al. also specifically references packaging the adhesive in thin plastic films of about 15 to lOOμm for purposes of minimizing the amount of packaging material blended in with the thermoplastic adhesive in order to avoid undesired changes in adhesive functionality. Due to both the extended cooling time requirement and the lack of any structural integrity provided by the thin plastic film within which the adhesive is encased, the packaging technique of Rouyer et al. is simply not generally applicable to the packaging of pressure-sensitive adhesives which are subject to excessive cold flow at those temperatures encountered during normal packaging, shipping, handling and storage of such adhesive compositions (i.e., up to about 50 °C). Efforts to package such adhesives using the technique of Rouyer et al. would result in the adhesive mass deforming prior to packaging while the adhesive is cooling below the melt temperature of the plastic film, and continuing to deform even after packaging, with the adhesive eventually creeping out of the packaging or rupturing the packaging unless specific measures have been taken to completely seal the adhesive within a sufficiently strong packaging film.

The packaging techniques disclosed by Hausdorf, Hatfield et al. and Rouyer et al. subject the hot melt adhesive to a significant thermal and/or mechanical history for purposes of packaging the adhesive. This is in contrast with the generally accepted industry practice of minimizing the thermal and mechanical history of hot melt adhesives in order to avoid or reduce various deleterious effects such as (i) a diminution in the adhesive properties and characteristics of the adhesive, (ii) an adverse impact upon the visual appearance of the adhesive, and (iii) the generation of an unappealing odor. It is widely accepted that even modest increases in the temperature and modest mechanical working of pressure sensitive adhesives can cause such deleterious effects, with excessive thermal and/or mechanical processing resulting in a commercially unacceptable product, particularly for medical applications.

Hence, a continuing need exists for a simple and inexpensive method of packaging pressure-sensitive adhesives which are subject to excessive cold flow under ambient conditions without significantly contributing to the thermal and/or mechanical history of the adhesive.

SUMMARY OF THE INVENTION

We have discovered a simple and inexpensive method of packaging large blocks of cold-formable, pressure-sensitive adhesives within a melt-blendable packaging material when the adhesive is subject to substantial cold flow at ambient conditions. The method involves enveloping a unitary block of a cold-formable, pressure-sensitive adhesive within a melt-blendable, nontacky plastic film. The block of pressure-sensitive adhesive can be enveloped within the plastic film immediately after being shaped without cooling of the shaped adhesive and/or cooling of the plastic film. The adhesive block can be shaped to substantially any desired size and shape and packaged in the melt-blendable plastic film without exposing the adhesive to any additional thermal or mechanical processing. The film coated block of cold-formable, cold-flowable, pressure-sensitive, adhesive is preferably at least 5 kg in size and placed within a rigid container for purposes of controlling cold-flow deformation of the packaged adhesive.

The entire combination of pressure-sensitive adhesive and plastic film can be removed from the rigid container and fed directly into an adhesive coater, where the plastic film is melt blended into the adhesive composition and coated onto a substrate along with the pressure sensitive adhesive. Since the plastic film is melt-blendable with the adhesive, incorporation of the film into the adhesive results in a minimal deleterious effect upon the adhesive properties and characteristics of the coated adhesive.

DETAILED DESCRIPTION OF THE INVENTION INCLUDING A BEST MODE

DEFINITIONS

As utilized herein, including the claims, the term "cold flow", is utilized in accordance with its standard industry meaning to indicate viscous deformation at ambient conditions. As utilized herein, "substantial cold flow " means cold flow of such a magnitude that a mass of the material cannot retain a three-dimensional shape (e.g., spherical, square, rectangular and cylindrical) under force of gravity under ambient conditions for several days, unless placed within a container or otherwise provided with external support.

As utilized herein, including the claims, the term "cold-formable ", when used to characterize an adhesive composition, references an adhesive composition capable of being readily masticated and shaped at temperatures of less than about 50 °C. As utilized herein, including the claims, the term "melt-blendable ", when used to characterize a thermoplastic film used to package a pressure-sensitive adhesive, references a material which, at modest concentrations of generally less than about 2 wt%, can be melt blended into the pressure-sensitive adhesive with minimal adverse effect upon the adhesive properties and characteristics of the resultant adhesive blend.

TESTING PROCEDURES

The test methods used to measure the peel adhesion and sheer strength reported herein are those standardized tests established by the American Society for Testing of Materials (ASTM) and described in Test Methods for Pressure-Sensitive Tapes, Eighth Edition, August 1985, Pressure- Sensitive Tape Council, Glenview, Illinois.

Peel Adhesion (ASTM P3330-78, PSTC-1 11/75)

Peel adhesion is the force required to remove an adhesive coated strip of a flexible sheet material from a test panel at a specific angle and rate of removal. This force is expressed in terms of Newtons per 100 mm width of the coated strip. A brief overview of this testing procedure is set forth below.

Step 1: A 12.5 mm wide adhesive-coated strip is applied to the horizontal surface of a clean glass test plate with a hard rubber roller. The strip is applied so that at least 12.7 lineal cm of the strip is in firm adhesive contact with the plate and one end of the strip remains free. Step 2: The free end of the strip is doubled back upon itself, so that the angle of removal will be 180°, and the free end attached to an adhesion tester scale.

Step 3: The glass test plate is clamped within the jaws of a tensile testing machine and the plate moved away from the scale by the machine at a constant rate of 2.3 meters per minute.

Step 4: The scale reading is recorded as the strip is peeled from the glass surface. The peel strength is reported as the average value of the range of numbers observed during the test in N/dm.

Shear Holding Strength (ASTM D3654-78, PSTC-7)

Shear strength is a measure of the cohesiveness or internal strength of an adhesive based upon the force required to pull an adhesive strip from a standard flat surface in a direction parallel to the surface to which it has been affixed with a definite pressure. Shear strength is measured in terms of the minutes required to pull a standard area of an adhesive coated sheet material from a stainless steel test panel when the sheet is subjected to a constant stress created by a standard load. A brief review of the testing procedure is set forth below.

Step 1: A 12.5 mm wide adhesive-coated strip is applied to the horizontal surface of a stainless steel panel. The strip is applied so that at least 12.5 lineal mm of the strip is in firm adhesive contact with the panel and one end of the strip remains free.

Step 2: The stainless steel panel is clamped to a rack and the free end of the strip doubled back upon itself, so that the angle of removal will be about 178°.

Step 3: A 1 kg weight is attached to the free end of the strip and allowed to hang freely under force of gravity.

Step 4: The time required in minutes for the strip to completely separate from the panel is recorded and reported as the shear strength.

METHOD OF MAKING

Pressure-Sensitive A dhesives

This invention can be usefully employed to package any of the various pressure-sensitive adhesives formed by any of the numerous well known techniques for producing such adhesives, including acrylate pressure-sensitive adhesives, block copolymer pressure-sensitive adhesives, natural rubber pressure-sensitive adhesives, and silicone pressure-sensitive adhesives. The invention is particularly suited for use in the packaging of cold-formable, suspension polymerized acrylate pressure-sensitive adhesives which are subject to substantial cold-flow. The technique allows such adhesives to be packaged without contributing to the mechanical and thermal history of such adhesives. For purposes of facilitating further discussion of the invention, the invention will periodically be described in connection with the packaging of a cold-formable, suspension polymerized, pressure-sensitive adhesive. However, it is to be expressly understood that the invention is applicable to the packaging of other pressure-sensitive adhesives and is not to be unduly restricted to the packaging of suspension polymerized pressure-sensitive adhesives only.

Cold-Formable, Suspension Polymerized, Pressure-Sensitive Adhesives

Various methods are known for producing pressure-sensitive adhesives using suspension, emulsion and other polymerization techniques. One type of suspension polymerized pressure-sensitive adhesive having a wide range of applications are the suspension polymerized, acrylate copolymer, pressure-sensitive adhesive beads such as those disclosed in United States Patents Nos. 4, 833, 179, 4,952,650 and 5,292,844 issued to Young et al. and United States Patent No. 5,382,451 issued to Johnson et al. Briefly, the method involves (i) forming a blended premix of an unsaturated acrylic acid ester of a Cι-ι₄ nontertiary alcohol, a polar monomer copolymerizable with the acrylic acid ester, a modifier moiety effective for stabilizing the resultant pressure-sensitive adhesive beads, a chain transfer agent, and a free-radical initiator, (ii) suspending the premix in a water phase containing a suspension agent, (iii) polymerizing the suspended premix while maintaining the suspension under constant agitation so as to form pressure-sensitive acrylate polymeric beads suspended within the water, (iv) separating the pressure-sensitive adhesive acrylate beads from the water by conventional means, and then (v) forming the pressure-sensitive adhesive acrylate beads into the desired size and shape for transportation, storage and use. For use in connection with the present invention, the pressure-sensitive adhesive is formed into blocks of from 2 to 50 kg, preferably 5 to 20 kg, and most preferably 5 to 10 kg..

When the pressure sensitive adhesive is a suspension polymerized acrylate pressure sensitive adhesive, the blocks may be formed by any of the well known mechanical separation techniques. By way of example, excess water may be removed from the suspension polymerized adhesive beads through the use of a mechanical press of the type described in "Perry's Chemical Engineers' Handbook", (6^th Ed., 1984) at Chapter 19, pp. 103-107. Specifically, a continuous-screw extrusion press, as described at pages 104 and 105 of Perry's, is particularly effective for separating the polymerized, acrylate, pressure-sensitive adhesive beads from the aqueous reaction medium. Such low temperature separation techniques permit the adhesive to be shaped as desired for packaging without subjecting the adhesive to an unnecessary thermal history (i.e., the adhesive is cold-formable).

Wrapped Block of Suspension Polymerized Pressure-sensitive Adhesives

The block of suspension polymerized pressure-sensitive adhesive is enveloped within a thin plastic film for purposes of providing a nontacky skin around the adhesive block. The suspension polymerized pressure-sensitive adhesive block may be wrapped immediately after it is shaped since such adhesives can be shaped at temperatures of less than 50 °C (i.e., cold-formable adhesives).

The plastic film is selected to be melt-blendable with the pressure-sensitive adhesive so that the entire wrapped block of adhesive can be fed into an adhesive coater and the plastic film melt blended and coated along with the pressure-sensitive adhesive.

Preferred plastic films also exhibit (i) a low melting point (i.e., less than about 120 °C) so as to minimize the thermal history of the adhesive, (ii) good handling characteristics and tear resistance at film thicknesses of between about 10 to 50 μm, and (iii) provide a surface feel and texture which is comfortable to handle (e.g., neither too slippery nor too abrasive).

A number of different plastics are well suited for use as the plastic film in connection with the present invention, including specifically, but not exclusively, polyethylene, ethylene vinyl acetate copolymers such as those containing 9% to 18% vinyl acetate available from AT Plastics Inc., ethylene methyl acrylate copolymers such as those available from Exxon Chemical under the trademark OPTEMA™, ethylene methyl acrylate / acrylic acid terpolymers such as those available from Exxon Chemical under the trademark ESCOR ATX™, polyethylene / acrylic acid copolymers such as those available from E.I. DuPont under the trademark SURYLN™, and blends of the various afore-mentioned polymers with styrene-butadiene-styrene and styrene-isoprene-styrene copolymers such as those available from Shell Oil Co. under the trademark KRATON™.

The plastic film preferably has a thickness of between about 10 to 100 μm. While the optimum thickness depends in large measure upon the actual plastic used and the size of the pressure-sensitive adhesive block, a thickness of about 10 - 50 μm, and more specifically about 25 μm, is generally effective for securely encasing the pressure- sensitive adhesive without adversely impacting the performance characteristics of the pressure-sensitive adhesive when the film is blended into the adhesive prior to coating. Viewed in another way, the thickness of the plastic film is preferably selected such that the plastic film constitutes less than 2 wt%, preferably less than 1 wt%, and most preferably less than about 0.1 wt% of the packaged block of pressure-sensitive adhesive. Due primarily to the large size of the pressure-sensitive adhesive blocks (i.e., greater than about 5 kg and up to about 50 kg) the wt% contributed by even fairly thick plastic films of around 200 μm will generally be less than 2 wt%, and will often be less than about 1 wt%.

The plastic film is wrapped around the block of suspension polymerized pressure-sensitive adhesive, as opposed to coating the plastic film over the adhesive or extruding molten adhesive into the plastic. Wrapping the plastic film around the adhesive provides a number of advantages including the ability to physically separate the adhesive processing and shaping equipment from the wrapping equipment, and the ability to package the adhesive without contributing to the thermal or mechanical history of the adhesive.

That portion of the film which directly contacts the surface of the pressure sensitive adhesive block will adhere to the surface of the adhesive. The edges and corners of the film which do not directly contact the pressure-sensitive adhesive can be secured in position against the adhesive block by any of a number of well known techniques, including thermoplastic tapes, heat sealing and pressure sealing. In addition, as described in further detail below, the film can be sized and shaped relative to the adhesive block and then wrapped in such a way that any loose edges and corners will be positioned between the adhesive block and the walls and/or base of a rigid container into which the wrapped adhesive is placed for shipment and storage. The thin plastic film does not provide any significant structural rigidity to the block of pressure-sensitive adhesive. Hence, in order to prevent a wrapped block of cold flowable, suspension polymerized, pressure-sensitive adhesive from deforming and creeping out of the wrapper, the wrapped adhesive block is placed within a rigid container having a size and shape which generally conforms to the size and shape of the wrapped adhesive block. In order to minimize deformation of the adhesive block prior to use and reduce the likelihood that the adhesive will flow outside the plastic film, the rigid container preferably defines a retention chamber which provides a maximum gap between the sides of the adhesive block and the walls of the container of about 2 to 10 mm before the adhesive begins to conform to the shape of the retention chamber. A cover for the container can be employed if desired.

A number of inexpensive materials are well suited for use as the rigid container, including specifically, but not exclusively: paper such as cardboard and pressboard; plastics such as polyethylene, polypropylene and polyethyleneterphthalate; foamed plastics such as expanded polystyrene; and reinforced composites such as fiberglass reinforced polyurethane and glass fiber reinforced polypropylene.

The containers are preferably nestible, stackable and reusable. Nestible containers facilitate storage of the containers before and after use. Stackable containers facilitate palletizing of the adhesive blocks for shipment and storage.. The containers are reusable because no adhesive residue is left behind in the container after removal of the packaged adhesive block.

METHOD OF USING

The wrapped block of cold-formable pressure-sensitive adhesive is conveniently used by simply removing the wrapped adhesive block from the rigid container and feeding the adhesive block, including the plastic wrapping, into a conventional adhesive coater. The plastic film can be melt blended into and coated along with the pressure- sensitive adhesive so long as the film is well blended into the pressure-sensitive adhesive within the adhesive coater before being coated onto a substrate.

The ability to provide the pressure-sensitive adhesive in blocks as large 5 to 50 kg reduces the tendency of the pressure-sensitive adhesive to bridge and/or block within conventional adhesive coating equipment.

Coating of the wrapped block of pressure-sensitive adhesive onto a substrate requires that the adhesive block be brought to the greater of (i) the melting point of the plastic film and (ii) the application temperature of the pressure-sensitive adhesive. Hence, by selecting a melt-blendable plastic film having a melting point below the application temperature of the packaged pressure-sensitive adhesive, (an option available for cold-formable adhesives) the thermal history of the adhesive can be minimized, with a corresponding increase in the ability to consistently provide a superior adhesive coating.

EXAMPLES

Example 1

(Formation of Suspension Polymerized Pressure Sensitive Adhesive)

Adhesive copolymers A and B, comprised of 96 parts by weight isooctyl acrylate and 4 parts by weight methacrylic acid were prepared in accordance with the procedure described below, wherein all parts by weight are based upon the weight of monomer base (i.e., weight of isooctyl acrylate and methacrylic acid). The Internal Viscosity of Adhesives A and B are 1.3 and 0.9, respectively, with Internal Viscosity measured by conventional means using a Cannon-Fenske #50 viscometer in a water bath controlled at 25° C and reported as the flow time for 10 ml of a polymer solution (0.2 g of polymer per deciliter ethyl acetate).

Into a reaction vessel was placed 150 parts by weight deionized water, 0.1 parts by weight ZnO and 0.15 parts by weight CAB-O-SIL® EH-5 hydrophilic silica, to form an aqueous mixture. The aqueous mixture was purged with N₂ and heated to 55 °C under constant agitation until the ZnO and silica were thoroughly dispersed within the aqueous mixture.

Into a separate mixing vessel was blended 96 parts by weight isooctyl acrylate and 4 parts by weight methacrylic acid to form the monomer base. To the monomer base was added 0.5 parts by weight VAZO™64 initiator purchased from DuPont, and 0.03 parts by weight (Adhesive A) and 0.06 parts by weight (Adhesive B) isooctyl thioglycolate, to form a reaction mixture. The reaction mixture was agitated until all components were thoroughly dispersed.

The reaction mixture was added to the aqueous mixture within the reaction vessel and subjected to vigorous agitation for 6 hours, with the vessel purged with N₂ gas throughout the reaction period. The reaction was monitored throughout and a cooling jacket employed as necessary to prevent the exothermic reaction from heating the reaction solution above 70 °C.

The resultant pressure-sensitive adhesive beads were separated from the aqueous reaction medium by a continuous-screw extrusion press, cut into 18 kg blocks and placed within release coated shipping containers for future packaging and testing. Example 2

(Packaging of Suspension Polymerized

Pressure-Sensitive Adhesive)

The suspension polymerized pressure-sensitive adhesives of Example 1 were removed from their shipping containers and cut at room temperature into approximately 4.5 kg. blocks using a water-misted 24-inch (61 cm) SPADONE™ bale cutter equipped with a pneumatic drive. The 4.5 kg blocks were hand-wrapped in 50 μm thick low-density polyethylene (LDPE) film, heat sealed, and placed inside 14" (35 cm) high by 16" (41 cm) wide by 29" (74 cm) long stackable and nestable reusable plastic containers purchased from Buckhorn Company (Container Model No.: 18- 702E). The blocks eventually conformed to the shape of the container during storage without leakage of adhesive outside the LDPE film.

Example 3

(Coating of Packaged Suspension Polymerized Pressure-Sensitive A dhesive)

The 4.5 kg LDPE film-wrapped blocks of adhesive A and adhesive B were separately fed through a continuous-screw extrusion press at room temperature without removing the LDPE film. The output was pumped via a gear pump into a coating extruder at 160°C and coated onto a [primed polyester] [0.125 mm polyethylene vinyl acetate] substrate at a thickness of approximately [38 μm] [25 μm] to produce adhesive coated tape. The procedure was repeated for additional 4.5 kg blocks of both adhesive A and adhesive B from which the LDPE film had been removed. There was no detectable difference in the peel adhesion or shear strength of the tapes made from the adhesive alone and that made from the film-wrapped adhesive blend. Example 4

(Adhesive Properties of Melt Blended Combination of Plastic Film and Suspension Polymerized Pressure-Sensitive Adhesive)

The film materials listed below in Table ONE were each converted to powder form in a cryogenic mill and then introduced into an aqueous suspension of Adhesive A and Adhesive B as described in Example 1.

The suspensions were then gravity-filtered and oven-dried to form "cakes" of suspension polymerized acrylate pressure sensitive adhesives containing 1 wt% particulate plastic film physically blended within the adhesive. The resulting cakes were fed into a coating extruder at 150°C and coated onto a primed polyester substrate at a coating thickness of 25 to 50 μm to produce adhesive test tapes.

Control tapes coated with unadulterated adhesives A and B (i.e., adhesive without added film material) were prepared in similar fashion for use as a control.

The test tapes and control tapes were subjected to shear and adhesion testing.

Test results for both the test tapes and the control tapes are reported in Table ONE for Adhesive A and Table Two for Adhesive B. As can be seen from the data reported in Tables ONE and Two, addition of the film materials to the suspension polymerized pressure-sensitive adhesives did not appreciably diminish the adhesive properties of the adhesives, and even resulted in an increase in certain adhesive properties.

TABLE ONE

(ADHESIVE A)

EVA = Ethylene Vinyl Acetate VA = Vinyl Acetate

TABLE Two

(ADHESIVE B)

LLDPE = Linear Low Density Polyethylene

Claims

We claim:

1. A pressure-sensitive adhesive block enveloped within a melt-blendable nontacky plastic film, comprising: (a) a shaped unitary block of a pressure-sensitive adhesive subject to substantial cold flow under ambient conditions;

(b) a conformable, nontacky, melt-blendable, plastic film wrapped completely around the block of pressure-sensitive adhesive, whereby the resultant film covered block of pressure-sensitive adhesive is provided with a nontacky surface; and

(c) a rigid container housing the film covered block of pressure-sensitive adhesive;

(d) wherein the film covered block of pressure-sensitive adhesive has deformed within the container to at least partially conform to the shape of the container without flowing outside of the plastic film.

2. The pressure-sensitive adhesive block of claim 1 wherein the block of pressure- sensitive adhesive weighs at least 5 kg.

3. The pressure-sensitive adhesive block of claim 1 wherein the block of pressure- sensitive adhesive weighs 5 to 50 kg.

4. The pressure-sensitive adhesive block of claim 1 wherein the block of pressure- sensitive adhesive weighs 10 to 20 kg.

5. The pressure-sensitive adhesive block of claim 1 wherein the pressure-sensitive adhesive is a cold-formable, suspension polymerized, pressure-sensitive adhesive.

6. The pressure-sensitive adhesive block of claim 5 wherein the cold-formable, suspension polymerized, pressure-sensitive adhesive is a cold-formable, suspension polymerized, pressure-sensitive, acrylate adhesive.

7. The pressure-sensitive adhesive block of claim 6 wherein the plastic film is polyethylene.

8. The pressure-sensitive adhesive block of claim 1 wherein the plastic film comprises less than about 1 wt% of the film covered block of pressure-sensitive adhesive.

9. The pressure-sensitive adhesive block of claim 1 wherein the plastic film comprises less than about 0.1 wt% of the film covered block of pressure- sensitive adhesive.

10. The pressure-sensitive adhesive block of claim 1 wherein the plastic film is at least 25 μm thick and comprises less than 1 wt% of the film covered block of pressure-sensitive adhesive.

11. The pressure-sensitive adhesive block of claim 1 wherein the plastic film is at least 25 μm thick and comprises less than 0 1 wt% of the film covered block of pressure-sensitive adhesive.

12. The pressure-sensitive adhesive block of claim 1 wherein the container is a nestible and stackable container.

13. A method of packaging a pressure-sensitive adhesive, comprising: (a) forming a shaped unitary block of a cold-formable, pressure-sensitive adhesive subject to substantial cold flow at ambient conditions without heating the adhesive; and

(b) enveloping the block of pressure-sensitive adhesive within a melt- blendable, nontacky, plastic film without heating the adhesive or actively cooling the film.

14. The method of claim 13 further comprising: (c) placing the film covered block of pressure-sensitive adhesive within a rigid container and allowing the block to at least partially conform to the shape of the container.

15. The method of claim 13 wherein forming a shaped unitary block of a pressure- sensitive adhesive comprises forming a block of the adhesive weighing at least 5 kg-

16. The method of claim 13 wherein forming a shaped unitary block of a pressure- sensitive adhesive comprises forming a block of the adhesive weighing at least 10 kg.

17. The method of claim 13 wherein enveloping the block of pressure-sensitive adhesive within a melt-blendable, nontacky, plastic film comprises enveloping the block of pressure-sensitive adhesive within a plastic film contributing less than about 1 wt% to the film enveloped block of pressure-sensitive adhesive.

18. The method of claim 13 wherein enveloping the block of pressure-sensitive adhesive within a melt-blendable, nontacky, plastic film comprises enveloping the block of pressure-sensitive adhesive within a plastic film having a thickness of at least 25 μm and constituting less than about 0.1 wt% of the film covered block of pressure-sensitive adhesive.

19. A method of packaging a pressure-sensitive adhesive, comprising: (a) forming a shaped unitary block of a cold-formable, pressure-sensitive adhesive subject to substantial cold flow at ambient conditions without contributing to the thermal history of the adhesive; and (b) enveloping the block of pressure-sensitive adhesive within a melt- blendable, nontacky plastic film without contributing to the thermal history of the adhesive.

20. The method of claim 19 further comprising: (c) placing the film covered block of pressure-sensitive adhesive within a rigid container and allowing the block to at least partially conform to the shape of the container.

21. The method of claim 19 wherein forming a shaped unitary block of a pressure- sensitive adhesive comprises forming a block of the adhesive weighing at least 5 kg.

22. The method of claim 19 wherein forming a shaped unitary block of a pressure- sensitive adhesive comprises forming a block of a suspension polymerized pressure-sensitive adhesive.

23. A method of packaging a pressure-sensitive adhesive, comprising: (a) forming a shaped unitary block of a cold-formable, pressure-sensitive adhesive subject to substantial cold flow at ambient conditions; and (b) enveloping the block of pressure-sensitive adhesive within a melt- blendable, nontacky plastic film without contributing to the mechanical history of the pressure-sensitive adhesive.

24. The method of claim 23 further comprising: (c) placing the film covered block of pressure-sensitive adhesive within a rigid container and allowing the block to at least partially conform to the shape of the container.

25. The method of claim 23 wherein forming a shaped unitary block of a pressure- sensitive adhesive comprises forming a block of the adhesive weighing at least 5 kg.

26. A method of packaging a pressure-sensitive adhesive without contributing to the thermal history of the adhesive, consisting of: (a) forming a shaped unitary block of a cold-formable, suspension polymerized, pressure-sensitive adhesive subject to substantial cold flow at ambient conditions and weighing at least 5 kg; and (b) enveloping the block of pressure-sensitive adhesive within a melt- blendable, nontacky plastic film.

27. The method of claim 26 wherein enveloping the block of pressure-sensitive adhesive within a melt-blendable, nontacky plastic film comprises enveloping the block of pressure-sensitive adhesive within a plastic film constituting less than about 0.1 wt% of the film covered block of pressure-sensitive adhesive.

28. The method of claim 26 wherein enveloping the block of pressure-sensitive adhesive within a melt-blendable, nontacky plastic film comprises enveloping the block of pressure-sensitive adhesive within a plastic film having a thickness of at least 25 μm and constituting less than about 1 wt% of the film covered block of pressure-sensitive adhesive.

29. A method of packaging a suspension polymerized pressure-sensitive adhesive, comprising:

(a) forming a shaped unitary block of a cold-formable, pressure-sensitive adhesive subject to substantial cold flow at ambient conditions and weighing at least 5 kg; and

(b) wrapping the block of pressure-sensitive adhesive within a melt- blendable, nontacky plastic film without heating the block of pressure- sensitive adhesive or actively cooling the plastic film.

30. The method of claim 29 wherein forming a shaped unitary block of a pressure- sensitive adhesive comprises forming a shaped unitary block of a cold-formable, suspension polymerized, acrylate, pressure-sensitive adhesive.

31. The method of claim 30 wherein wrapping the block of cold-formable, suspension polymerized, acrylate, pressure-sensitive adhesive within a melt- blendable, nontacky plastic film comprises wrapping the block of cold-formable, suspension polymerized, acrylate, pressure-sensitive adhesive within a polyethylene film.

32. The method of claim 29 wherein enveloping the block of pressure-sensitive adhesive within a melt-blendable, nontacky plastic film comprises enveloping the block of pressure-sensitive adhesive within a plastic film having a thickness of at least 25 μm and constituting less than about 0.1 wt% of the film covered block of pressure-sensitive adhesive.