IL92921A - Dispensing container for multi-component curable materials and multi-component curable composition - Google Patents

Description

DISPENSING CONTAINER FOR MULTI-COMPONENT CURABLE MATERIALS AND MULTI-COMPONENT CURABLE COMPOSITION.

FIELD OF THE INVENTION The present Invention relates, In general, to multi-component coating, sealing, casting and gluing materials which may be hardened by the mixing of reactive components thereof and, in particular, to a system for storing, mixing and dispensing such materials.

BACKGROUND OF THE INVENTION Multi-component coating, sealing casting and gluing materials which are cured by the mixing of reactive components thereof are well known and, in many cases, are superior to their one component equivalents. An example of a two component material is an 'epoxy' adhesive, having base and hardener components. When these two components are mixed together, they react to form a high quality adhesive that may be superior in quality to an alternative one component adhesive that hardens by drying and curing in the air. It will be appreciated that many other types of multi-component materials are also known.

A disadvantage of conventionally available multi-component materials is that each reactive component thereof is supplied in its own packaging, and that a user is thus required to mix each reactive component according to predetermined proportions, as specified by the manufacturer. As a result, ready-to-use one component materials are often used in preference to superior multi-component alternatives, as it is far more convenient and quicker to use such materials supplied in a dispenser, such as a tube having a nozzle, than to mix two or more separately supplied components that are required to be mixed in predetermined proportions and thereafter placed in a dispenser prior to use.

On a larger, industrial scale, spraying and dispensing equipment for multi-component curable materials is known. Such equipment is, however, generally expensive and complex and, particularly on a small scale, is inconvenient to use.

SUMMARY OF THE INVENTION The present invention seeks to provide a system for storing all the components of a multi-component material, such as an adhesive or a sealant, in a single container, and for mixing the components within and dispensing the resulting mixture from the container, thereby overcoming disadvantages of known art.

There is provided, therefore, in accordance with an embodiment of the invention, a system for storing, initiating curing of and dispensing a multi-component curable material having two or more components which interreact chemically when mixed together, the system including a single container for storing the interreactive components; outlet apparatus, associated with the container, and through which the multi-component curable material may be dispensed; apparatus for preventing chemically reactive contact between each of the components; and apparatus for permitting chemically reactive contact between the components so as to initiate curing thereof prior to dispensing thereof through the outlet apparatus.

Additionally in accordance with an embodiment of the invention, the container defines an internal space in which the interreactive components are dispersed, · and the apparatus for preventing includes apparatus for enclosing discrete portions of at least one of the components so as to chemically separate that component from the other components, and the apparatus for permitting includes apparatus for causing release of the enclosed discrete portions prior to the dispensing thereof through the outlet apparatus, so as to permit chemically reactive contact to occur between the components.

The present invention moreover provides a curable composition which comprises at least two interreactive components and which is capable of self-cure when said at least two components react together, the composition being characterized by the facts that at least one of the interreactive components is in discrete form in which substantially each discrete unit thereof is surrounded by a layer of material, which material under normal conditions of storage does not react with any one of the interreactive components and that the layer may be fractured by application of mechanical stress thereto. It is to be understood that there is no restriction on the nature of the components other than that they are capable of self-cure when mixed together, that is to say, no further ingredient is necessary for cure to be effected. Thus in general, the components may be selected as appropriate from e.g. curable monomers, oligomers, and polymers, and from initiators, promoters, accelerators and catalysts.

The curable composition may comprise also a solvent medium for at least one of the interreactive components, provided that the solvent medium does not dissolve a significant amount of the layer under normal conditions of storage.

Persons skilled in the art will be aware that the curable compositions may contain optional non-reactive components such as fillers, colorants, plasticizers and so forth.

The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which: Fig. 1 is a schematic cut-away side view of a dispensing container for a multi-component curable material, constructed and operative in accordance with an embodiment of the invention; Fig. 2 is an enlarged cut away view of the screen element shown in Fig. 1, and illustrating mixing of two reactive components of the curable material downstream of the screen element; Fig. 3 is a schematic cut-away side view of a dispensing container for a multi-component curable material, constructed and operative in accordance with an alternative embodiment of the invention; Fig. 4 is an enlarged cut away view of a multiple screen arrangement shown in Fig. 3. and illustrating mixing of two reactive components of the curable material downstream of the screen arrangement; Fig. 3 shows on nltornnbive configuration of the multiple screen assembly depicted in Fig. 4; Fig. 6 is a schematic cut-away side view of a dispensing container for a multi-component curable material, constructed and operative in accordance with an additional embodiment of the invention; Fig. 7 is a schematic cut-away side view of a dispensing container for a multi-component curable material, constructed and operative in accordance with yet a further embodiment of the invention; Figs. 8A and 8B show a crushable dispensing container for a multicomponent curable material constructed and operative in accordance with an embodiment of the invention; Figs. 9A and 9B show a dispensing container employing a pair of rollers to provide mixing of reactive components of a multi-component curable material; Fig. 10 shows an embodiment similar to that of Figs. A and 9B, but wherein the rollers also define generally radially extending surface protrusions; Fig. 11 ■ shows a split storage, mixing and dispensing system for multi-component curable materials, constructed in accordance with the present invention; Fig. 12 is an enlarged cut-away view of the mixing unit shown in Fig. 11; Fig..13 shows a dispensing container similar to that of Fig. 1, but also including mechanical agitating apparatus according to a further embodiment of the invention; and Fig. Ik shows a dispensing container constructed according to a further embodiment of the invention. 92921/2 DETAILED DESCRIPTION OF THE INVENTION Reference is now made to Fig. 1, in which is shown a dispensing container, referenced 10, for generally any sort of multi-component curable coating, sealing, casting, potting and gluing materials which are cured by mixing two or more reactive components thereof. As described above in the 'Background of the Invention' although multi-component materials are superior to their one component equivalents, the one component materials are conventionally much easier to use, as no on-site mixing is necessary.

The present invention seeks, to provide, therefore, a system for storing, mixing and dispensing a multi-component curable material from a single container. According to the invention, two or more inter-reactive components of a multi-component curable material can be stored together inside the container in nonreactive contact, and the material can, when desired, be mixed inside the container and dispensed therefrom.

Container 10 which, typically, although not necessarily, is a disposable container, defines an interior storage space 12. Storage space 12 is bounded at one end by a movable plunger 14, or the like. Storage space 12 is bounded at the other end by a screen element 20. In the present embodiment, the reactive components of, typically, a two component curable material are stored in the space 12 in a nonreactive dispersion. This is facilitated by isolating one of the reactive components in discrete form, e.g. in powder, granular, globule, pellet or capsule form in a surrounding layer of a neutral material, i.e. a materi- 92921/2 al that is nonreactive with each of the reactive components. Examples of different materials are brought hereinbelow. The other of the reactive components, in this particular embodiment, preferably is a liquid medium 15 in which the globules are suspended.

The liquid medium 15 may be a liquid or paste and may have a viscosity in the range of approximately 20,000 centipoise to 250,000 centipoise.

In other embodiments of the invention, however, both or all reactive components may be provided in discrete form. In these cases, the liquid medium is not one of the reactive components.

As shown in Fig. 1, a two component dispersion of globules suspended in the liquid medium 15, as described above, is contained within a storage space 12. Screen element 20, which may be attached to dispensing container 10, is provided transversely across the storage space, i.e. across the direction of flow of the material when it is dispensed, and defines apertures 22 that, while permitting flow of the reactive component in liquid form, are sufficiently small so as to confine the relatively large globules or capsules, referenced 24, to a space between the screen element and the plunger 14. Generally, the globules may have a diameter of between 0.5 mm and 10 mm, although more preferably of about 2 to 3 mm.

Referring now also to Fig. 2, when plunger 14 (Fig. 1) is displaced towards the outlet nozzle end of the container, as shown, the curable material inside the storage space 12 is pres- 92921/2 surized. In response to this pressurization, the liquid medium 15 passes through screen element 20 to a mixing chamber 21 defined between the screen element 20 and the outlet nozzle 18. The globules or capsules 24 are initially prevented from moving into the mixing chamber by the screen element, as the apertures of the screen element are smaller than the globules.

The viscosity of the liquid medium 15 and the size of the apertures 22 of screen element 20 are such that the applied pressure in storage space 12 reaches a predetermined minimum pressure. When the predetermined minimum pressure is reached, the respective neutral layers 30 of those globules 24 engaged by the screen element are broken by being pressed against edges 26 of the solid, relatively rigid portions 28 of the screen element so as to release the hitherto confined mass of reactive component 32 into the other, non-confined component. The now released component 32 is carried downstream of the screen element into the mixing chamber, in which it mixes with the other reactive component so as to initiate the reactive curing or hardening of the curable material as it is extruded or dispensed through outlet nozzle 18.

It will thus be appreciated by persons skilled in the art that, while preventing chemically reactive contact between the reactive components of a multi-component curable material prior to mixing, the present invention also provides a dispensing container that is operative to initiate curing of the material in response to pressure applied thereto by displacement of the plunger, which displacement is operative to pass the reactive components through the built-in screen, thereby causing the reactive components to become mixed immediately before the multi-component material is dispensed. A further advantage of the present invention is that it makes obsolete the use of expensive and complex multi-component spraying equipment, as known in the art.

Referring briefly to Fig. 13, a dispensing container 110 is shown. Container 110 is similar to container 10, as shown and described above in conjunction with Fig. 1, but also includes agitating apparatus 112 for mechanically agitating the partially mixed material downstream of screen 20. Although apparatus 112 is shown, in the present example, to be a pair of overlapping impellers, which typically are rotated about respective axes 114 and 116 by the flow of the curable material, apparatus 112 may alternatively be any other suitable apparatus known in the art.

It will also be appreciated that agitating apparatus 112 is shown in conjunction with a single screen solely by way of example, and agitating apparatus may alternatively be provided in conjunction with any of the other embodiments of the present invention.

Reference is now made briefly to Fig. 3, in which is shown a dispensing container 40. Container 40 is generally similar to container 10 as shown and described above, and similar components are denoted, therefore, by similar reference numerals. However, whereas container 10 includes only a single screen element 20, container 40 includes a multiple screen arrangement 42, comprising a plurality of screen elements 20. As shown, the screen elements are arranged such that their apertures are not aligned along straight lines. As shown in Fig. 4, this non-alignment forces the reactive components to flow along generally sinusoidal paths 45 and greatly increases, therefore, the mixing experienced by the components as they pass through the multiple screen arrangement.

Reference is now made to Fig. 5, in which is shown a multiple screen arrangement 46 that is generally similar to the screen assembly 42 shown in Fig. 4, except that the present screen assembly 46 includes, in addition to a number of generally plaiiar screen elements 20, a number of non-planar screen elements- 48 having generally convex protrusions 50, which enhance the mixing of the components of the curable material as they flow therepast.

Referring now briefly to Fig. 14, there is shown a dispensing container 150 with a removable outlet unit 152. Container 150 is generally similar to container 40 (Fig. 3) as described above, and similar components are denoted, therefore, by similar reference numerals. However, whereas container 40 may not be reusable after it has been used once, due to residual cured material located in the generally integrally formed nozzle portion clogging the nozzle portion, as the removable outlet unit 152 of the present embodiment includes both screen arrangement 42 and the nozzle 18, a clogged nozzle unit may simply be removed and replaced by a new outlet unit prior to reuse.

Reference is now made to Fig. 6, in which there is shown a dispensing container 60, containing a two component dispersion of globules 24 suspended in a liquid medium 15, as described above in conjunction with Figs. 1 - 5. The container has a movable plunger 61 at one end, and an outlet nozzle 62 at the other end. A plurality of mixing elements 63, such as polyethylene spheres, are retained in a mixing chamber 64 defined between respective rear and front screen elements 65 and 66. The mixing elements are operative to provide thorough mixing of the reactive components As plunger 61 is displaced towards the outlet nozzle end of the container 60, as with previous embodiments of the invention, the curable material inside the container is pressurized. In response to this pressurization, the liquid medium 15 is able to pass through rear screen element 65 into mixing chamber 64. The globules or capsules 24 are initially prevented from moving into the mixing chamber by the rear screen element 65, as the apertures of the screen element are smaller than the globules.

When, however, the applied pressure reaches a predetermined minimum pressure, the respective neutral layers 30 (Fig. 2) of those globules 24 engaged by the rear screen element are broken by being pressed thereagainst so as to release the hitherto confined mass of reactive component 32 into the other, non-confined component. The now released component 32 is carried downstream of the rear screen element into the mixing chamber. As both the reactive components flow along generally sinusoidal flow paths, between mixing elements 63, the components . become thoroughly mixed together as they pass through the mixing chamber so as to initiate the reactive curing or hardening of the curable material as it is extruded or dispensed through outlet nozzle 62. a 12 92921/2 Reference is now made to Fig. 7, in which there is shown a further dispensing container 70, containing a two component dispersion of globules 24 suspended in a liquid medium 15, as described above in conjunction with Figs. 1 - 6. The container has a movable plunger 71 at one end, and an outlet nozzle 72 at the other end. Respective first and second pluralities of mixing elements 73 and 74, for example, such as polyethylene spheres, are retained in respective first and second mixing chambers 75 and 76, defined between respective rear, intermediate and front screen elements 77, 78 and 79. The mixing elements are operative to provide thorough mixing of the reactive components As plunger 71 is displaced towards the outlet nozzle end of the container 70, as with previous embodiments of the invention, the curable material inside the container is pressurized. In response to this pressurization, the liquid medium 15 is able to pass through rear screen element 77 into first mixing chamber 75. The globules or capsules 24 are initially prevented from moving into the mixing chamber by the rear screen element, as the apertures of the screen element are smaller than the globules.

When, however, the applied pressure reaches a predetermined minimum pressure, the respective neutral layers 30 (Fig. 2) of those globules 24 engaged by the rear screen element 77 are broken by being pressed thereagainst so as to release the hitherto confined mass of reactive component 32 into the other, non-confined component. The now released component 32 is carried downstream of the rear screen element 77 into the first mixing 92921/2 chamber 75, and through intermediate screen element 78 into second mixing chamber 76. As both the reactive components flow along generally sinusoidal flow paths, through the various mixing elements, the components become thoroughly mixed together as they pass through the mixing chambers so as to initiate the reactive curing or hardening of the curable material as it is extruded or dispensed through outlet nozzle 72.

Reference is now made briefly to Figs. 8A and 8B, in which there is shown a dispensing container 100 which, although generally similar to container 10 of Fig. 1, is a tubelike container, such as is conventionally used, inter alia, for premixed adhesives. Container 100 defines an internal space 102, an outlet nozzle 104 and a screen element 106. A mixing chamber 108 is defined between screen element 106 and outlet nozzle 104. A dispersed mass of a two component curable material is provided within the container in predetermined proportions. Mixing and dispensing of the curable material is achieved by crushing the container, such as by rolling up its closed end, as shown in Fig. 8B. As the container is crushed, the material is forced through the screen element, causing the contents of the globules to be mixed in mixing chamber 108 with the unconfined component and the material is thereafter extruded though nozzle 104 in initial stages of curing.

Reference is now made briefly to Figs. 9A and 9B, in which there are shown a pair of rollers 82 and 83, which, according to the present embodiment, are mounted in place of or in addition to the various screen arrangements shown and 92921/2 described hereinabove. Rollers 82 and 83 are mounted for rotation about respective substantially parallel axes 84 and 86, so as to define a narrow gap 88. This gap is analogous to the apertures of the above-described screen elements and is small relative to the globules in which reactive component 32 is contained.

As the curable material dispersion is urged towards outlet nozzle 18, as described above in conjunction with the embodiments of Figs. 1 and 2, viscous forces associated with the flow of the liquid medium through the gap 88 causes the rollers 82 and 83 to rotate, such that globules engaged thereby are-crushed, thereby breaking the respective neutral layer of each globule so as to release the reactive component contained thereby into reactive contact with the other reactive component. The dispersion, now in initial stages of curing, is passed through the gap 88 between the rollers and is finally dispensed through outlet nozzle 18.

Reference is now made to Fig. 10, in which are illustrated a pair of rollers 90, in an arrangement generally similar to that shown in Figs. 9A and 9B. Rollers 90, however, define on their exterior surfaces 92, generally radially extending ridges 94, appearing as teeth-like projections in side view, which provide not only improved engagement of the globules as they are urged towards the rollers, but also ensure more efficient crushing or breaking open of the globules.

In the present embodiment, all the reactive components are in globular form, a first component being shown by small globules 96, a second component being shown by intermediate 92921/2 globules 98 and a third component being shown by large globules 99. Provision of each of the reactive components in the form of globules with generally solid outer layers provides for convenient handling of the material, and the provision of rollers with ridges or teeth is particularly suitable for ensuring that each globule is broken open efficiently when engaged by the rollers.

Reference is now made to Fig. 11, in which there is shown a split storage, mixing and dispensing system for multi-component curable materials, constructed in accordance with the present invention. The split system, referenced generally 120, is-similar in principle to the previous embodiments of the present invention, except that whereas the previous embodiments refer to self-contained dispensing containers, the present system is characterized particularly by having a mixing and dispensing head, referenced generally 122, at a location remote from a storage container 124.

As will be appreciated by persons skilled in the art, whereas the dispensing containers described hereinabove may be particularly useful on a small scale, the present split system is suited particularly to large scale, continuous operations.

As shown, therefore, split system 120 has a refillable storage container 124, which may be used for storing a multi-component curable material as described above, for example, a two component material as described in conjunction with the embodiment of Fig. 1, wherein one reactive component is globularized and is dispersed in the other reactive component.

The mixing and dispensing head 122 has a spray head 92921/2 126, from which the curing material is dispensed. Referring now also to Fig. 12, just upstream of the spray head is a mixing unit 128, defining an inlet 130 and an outlet 132 which communicates with the spray head 126. The mixing unit 128 has respective upstream and downstream screen elements 134 and 136, between which is defined a mixing chamber 138, housing a plurality of mixing spheres 140, similar to those employed in the respective dispensing containers 60 and 70 of Figs. 6 and 7. It will be appreciated that in place of the shown structure, any other suitable structure, such as shown and described in conjunction" with any of Figs. 1 - 7, 9, 10, 13 and 14, may be used.

In operation, a pump 142, which may be any suitable pump known to one skilled in the art, may be used for pumping the neutral two-component dispersion along a conduit or line 144, which is typically a flexible hose, towards mixing and dispensing head 122. The curable material is pumped into mixing unit 128 via its inlet 130, and through upstream screen element 134.

Globules 24 suspended in the dispersion are punctured by engagement with the upstream screen element and their contents are thus released for mixing and chemical reaction with the other reactive component. The multi-component material, in its initial stages of curing, subsequently flows through outlet 132 so as to be dispensed via the spray head 126. An exemplary use of split system 120 is in the application of coatings.

As shown, a flush connection, shown at 146, (Fig. 12) may also be provided, so as to permit cleaning of the mixing chamber 138 and spray head 126 by use of an appropriate solvent. 92921/2 Exemplary multi-component curable materials that may be usefully employed with the present invention may have as base materials, inter alia, epoxides, polyurethanes, polyesters, acrylics, polysulfides, and silicones, all of which cure after initial contact with appropriate reactants and/or catalysts.

Detailed examples of multi-component materials useful in the present invention are as follows: EXAMPLE I An adduct composition of 41.5 % trimethylhexamethylenediamine, · 37 % benzyl alcohol, 5 % salicylic acid, and 16.5 % of epoxy resin (Equiv. Wt 190) is gradually cooled to -17 eC. Before complete solidification, 3 mm globules or pellets of the adduct are formed by any known method, for example, as per the formation of tablets by tablet compressing machines that are widely used in the pharmaceutical industry. The globules are placed in a coating pan and agitated", while melted paraffin wax is sprayed on until they are completely coated by the wax. 1000 grams of epoxy resin (Equiv. Wt 190) and 300 grams of titanium dioxide are passed on a three roll mill and mixed with 580 grams of the coated globules of the above adduct. The mixture is placed into the interior space of a dispensing container (Figs. 1, 3, 6, 7, 8A, 8B, 13 and 14) or storage container (Fig. 11) of the invention.

The mixture is then pressed '.through 2.2 -2.5 mm apertures of a screen element of the container, passing into a mixing chamber thereof filled with polyethylene spheres (*) wherein the adduct of the globules mixes with the carrying epoxy resin mixture so as to initiate curing of the sealant. This mixture is thus ready for direct application to a work piece, or it may subsequently be fed to a spray nozzle (**). (*) e.g. in the embodiments of Figs. 6 and 7. (**) e.g. in the split system of Fig. 12.

EXAMPLE II - POLYSULFIDE SEALANT 500 grams of manganese dioxide, 490 grams of chlorinated paraffin (40% chlorine) and 10 grams of sulfur powder are thoroughly mixed and then passed three times on a three roll mill.

The mixture is cooled to solidification and formed into spheres of about 3 mm in diameter. The cold, solid spheres are placed in a coating pan and exposed to a spray of melted synthetic wax until completely coated.

A mixture consisting of 1000 grams of polysulfide polymer LP32, 500 grams of precipitated CaCO , 300 grams of 3 Santicizer 261 (manufactured by Monsanto Chemical Co., U.S.A.) and 50 grams of Aerosil 200, is mixed with 150 grams of the coated manganese dioxide spheres and placed in a container of the invention. Application of pressure causes the curable mixture to be passed through screen apparatus, rollers or the like and, thereafter, through an outlet, as a sealant in its initial stages of curing.

EXAMPLE III - POLYURETHANE JOINT SEALANT 1000 grams of 3, 3-dimethyl-4, 4-diaminodicyclohexyl methane is mixed with 100 grams of Levepox K10 (accelerator) and the mixture is cooled to below its solidification point and formed into 3 mm diameter globules. As described above, the globules are coated with wax. 1000 grams of urethane polymer Desmophen 11 and 80 grams of Aerosil are mixed together and 65 grams of the prepared globules are dispersed in the mixture.

The dispersion is then placed in a container of the invention and activated in a manner similar to that used to activate the polysulfide sealant (EXAMPLE II). 21 92921/? In general, multi-component materials used by divers may also be produced by encapsulating two or more components of the materials and by mixing the capsules of each component in desired proportions. The capsules can be mixed dry or, alternatively, suspended in a liquid medium which may either be any one of the other components or a neutral liquid or paste. The capsules are crushed as per any of the embodiments above, by rollers or screens, so as to release the contents of the capsules. Contact of the released capsule contents with the liquid medium is operative to initiate curing of the multi-component curable material. A plurality of plastic, glass, ceramic or metal spheres may also be present in the mixing chamber so as to permit their dispersion in the multi-component material, and the material may then be dispensed for immediate use.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been specifically shown and described hereinabove. The scope of the invention is limited, rather, solely by the claims, which follow: 92921/3

Claims (28)

1. A system for storing, initiating curing of and dispensing a multi-component curable material having at least two components which interreact when mixed together, said system comprising: a single container for storing the at least two components; outlet means, associated with said container, and through which the multi-component curable material may be dispensed; means for preventing chemically reactive contact between each of the at least two components; and means for permitting chemically reactive contact between the at least two components so as to initiate curing thereof prior to dispensing thereof through said outlet means.

2. A system according to claim 1, and also including means for applying at least a minimum pressure to the curable material so as to displace it towards said outlet means, said means for permitting also being operative to cause at least partial mixing of the at least two components in response to the application thereto of at least said minimum pressure.

3. A system according to either of claims 1 or 2, and wherein said container defines an internal space in which the at least two components are dispersed, and said means for preventing comprises means for enclosing discrete portions of at least one of the components so as to chemically separate that component from the at least one other component, and said means 92921/3 for permitting comprises means for causing release of the enclosed discrete portions prior to the dispensing thereof through said outlet means, so as to permit chemically reactive contact to occur between the at least two components.

4. A system according to claim 3, and wherein said means for preventing comprises means for separately enclosing all but one of the at least two components.

5. A system according to claim 4, and wherein said means, for preventing comprises means for separately enclosing discrete portions of each of the at least two components.

6. A system according to any claims 3 to 5, and wherein each of the discrete portions is suspended in a globule and said means for enclosing comprises a continuous layer of a substance that is nonreactive with any of the at least two components, said means for permitting being operative, when subject to said at least minimum pressure, to puncture said continuous layer so as to release the portion of the component contained thereby so as to permit chemically reactive contact thereof with each of the other of the at least two components.

7. A system according to any of claims 4 to 6, and wherein said means for permitting comprises a screen element operative to at least partially confine said globules in a predetermined space within said container, and defining a plurality of apertures configured to prevent passage therethrough of whole globules, said screen element being operative to break said continuous 92921/3 layer of each globule when it is pressed thereagainst under at least said minimum pressure, thereby releasing the discrete portion of the component contained by the globule so as to permit flow thereof through said apertures towards said outlet means.

8. A system according to claim 7, and also comprising means, arranged between said screen element and said outlet means, for imparting a generally sinusoidal flow characteristic to portions of the curable material downstream of said screen element so as to increase the mixing of the at least two reactive-components of the curable material.

9. A system according to either of claims 7 or 8, and comprising at least three screen elements arranged such that said plurality of apertures defined by one of said screen elements is in nonlinear alignment with said plurality of apertures of at least an adjacent one of said screen elements, thereby causing a nonlinear flow of the curable material passed through said screen element.

10. A system according to claim 9, and wherein at least one of said screen elements is configured to impart a generally sinusoidal flow characteristic to portions of the flow of said curable material.

11. A system according to claim 6, and wherein said means for permitting comprises means for engaging and crushing globules pressed thereagainst so as to release the contents of said 92921/3 globules when the curable material is subjected to at least said minimum pressure, said means for crushing also being operative to pass the released globule contents and the at least one other component towards said outlet means.

12. A system according to claim 11, and wherein said means for crushing comprises at least a pair of rollers rotating in opposite directions along parallel axes and defining a gap narrower than the globules so as to prevent passage of whole globules and to permit passage of the contents of said globules only after said globules have been crushed.

13. A system according to claim 12, and wherein at least one of said rollers has a generally cylindrical exterior surface defining a plurality of surface protrusions operative" to puncture said continuous layer on each globule passing between said pair of rollers.

14. A system according to any of the preceding claims, and wherein said outlet means comprises spray head means communicating with said container via conduit means defining a flow path for the multi-component curable material.

15. A system according to any of claims 1 - 13, and wherein said outlet means and said means for permitting are integrally formed as an outlet unit mounted onto said container.

16. A system according to claim 15, and wherein said outlet unit is removably mounted onto said container.

17. A system according to any of the preceding means and also including means, arranged between said means for permitting and said outlet means, for agitating the curable material so as to provide a thorough mixing of the at least two reactive components thereof.

18. "~ A system substantially as shown and described" hereinabove.

19. A system substantially as shown in any of the drawings.

20. A curable composition which comprises at least two interreactlve components and which is capable of self-cure when said at least two components react together, said composition being characterized by the facts that at least one of said interreactlve components is in discrete form in which substantially each discrete unit thereof is surrounded by a layer of material, which material under normal conditions of storage does not react with any one of said interreactive components and that said layer may be fractured by application of mechanical stress thereto.

21. A composition according to claim 20 which comprises also a solvent medium for at least one of said interreactive components, provided that said solvent medium does not dissolve a significant amount of said layer under normal conditions of storage.

22. A composition according to either claim 20 or claim 21 wherein said at least one of said interreactive components in discrete form is in the form of at least one member selected from the group consisting of powders, granules, globules, pellets and capsules.

23. A composition according to any of claims 20 to 22, which is a curable epoxide composition.

24. A composition according to any of claims 20 to 22, which is a curable polysulfide composition.

25. A composition according to any of claims 20 to 22, which is a curable polyurethane composition.

26. A composition according to any of claims 20 to 22, which is a curable polyester composition.

27. A composition according to any of claims 20 to 22, which is a curable acrylic composition.

28. A composition according to any of claims 20 to 22, which is a curable silicone composition. For the Applicant,