Aerosol Fan Sprayhead

Technical Field

This invention relates to aerosol sprayheads and, in particular, sprayheads utilized to dispense soluble elastomeric adhesive polymer solutions in a fan spray pattern.

Background Art

Small volume applications of elastomeric adhesive materials are most conveniently applied by aerosol spraying. In many applications, this convenience is enhanced if the adhesive is sprayed in an elliptical or "fan" spray pattern rather than a circular spray pattern, since the fan pattern produces more uniform coverage across the width of the pattern.

Dispersions of elastomeric polymers (e.g. , crosslinked nitrile rubbers, crosslinked butyl rubbers, and polychloroprene graft copolymers) have been sold in aerosol containers equipped with fan sprayheads. It is desirable, however, to be able to spray solutions of elastomeric polymers, as opposed to dispersions, because dispersions pose a settling problem which is not encountered with solutions, and because soluble polymers offer higher adhesion strengths and resist elevated temperatures better than crosslinked polymers.

Thus far, however, the aerosol industry has not been able to produce commercially acceptable aerosol containers filled with solutions of elastomeric adhesives because it has not been possible to obtain acceptable spray patterns from aerosols containing more than a few percent adhesive solids in solution. This is because the polymer structure of the elastomeric adhesive solutions has extensive chain entanglements, or in other words, a high solution viscosity. In general, if a polymer has a number

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average molecular weight above about 10,000 and generates a solution having non-Neutonian viscoelastic properties, it has been difficult to spray from an aerosol container. When, for example, a polychloroprene contact adhesive is dissolved in a solvent such as methylene chloride and loaded into an aerosol container pressurized with a propellant such as dimethyl ether and sprayed through an existing fan sprayhead, an unacceptably narrow, stream type of discharge, rather than a spray, is obtained at aerosol solids levels above about 4.4 percent by weight. A 4.4 percent solution of polychloroprene adhesive packaged in a standard 475 c ^ aerosol can would provide only about 22 grams of adhesive product, an amount sufficient to cover two surfaces of an area of only about 3.66 m ² . Such a small amount of product would be commercially unacceptable as a consumer would be paying primarily for the container and would quickly exhaust the contents. As a result, soluble adhesive polymers have never been successfully marketed in aerosol containers. Instead, where possible, they are crosslinked and sold as aerosol dispersions, or sold in containers such as cans, tubes or bottles which do not offer the convenience of an aerosol spray.

Industrial users of adhesives have been able to avail themselves of the benefits of soluble adhesive polymers through the use of airless spraygun equipment, which is too large and expensive to be used by individual consumers. Such airless spraygun equipment has employed sprayheads having an elongated nozzle opening recessed in a groove and restrictions in the flow path of the material upstream of the nozzle opening similar to those to be described herein. This structure has been desribed in U.S. Patent Nos. 2,621,078; 2,683,627; 3,000,576 _? 3,647,147 and 4,097,000. However, such airless spraygun equipment typically operates at pressures above 6.9 megapascals, as compared to typical aerosol container pressures of 0.17 megapascals, and the teachings of the above-enumerated patents do not indicate that the structure might have

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utility in sprayheads for aerosol containers filled with soluble adhesive polymers and operating at dramatically reduced pressures.

Disclosure of the Invention The present invention provides a sprayhead which produces a uniform fan spray pattern, when spraying elastomeric adhesive polymers in solution with a propellant, at adhesive solids levels more than two and one-half times the solids levels which may be sprayed by existing sprayheads.

The sprayhead of the invention includes an inlet stem inserted into an aerosol container which contains a solution of a soluble elastomeric adhesive polymer and a propellant at a relatively low pressure. The inlet stem includes an inlet passageway which communicates with a passageway of an outlet tube oriented at substantially 90 degrees to the inlet stem and which terminates in a groove which intersects the outlet tube passageway to form an elongate nozzle opening. The nozzle opening thus formed has a generally eliptical cross- section, is generally centered in the groove and has a major axis aligned with the groove which is substantially longer than the minor axis of the opening.

Located between the inlet stem and the nozzle opening is a restriction which enhances the uniformity of the spray pattern produced by the nozzle opening. In one embodiment, the restriction is formed as part of the sprayhead and defines an orifice communicating with the outlet tube. In another embodiment, the restriction defines a single orifice or a plurality of orifices located within the passageway of the outlet tube. In yet another embodiment of the restriction, a rectangular orifice located in the outlet tube is defined.

Brief Description of the Drawings

The present invention will be more thoroughly described with reference to the accompanying drawings wherein like numbers refer to like parts in the several views and wherein:

Figure 1 is an elevational view of a portion of an aerosol container equipped with a sprayhead assembly according to the present invention;

Figure 2 is an elevational view, partially in section, of the sprayhead assembly of Figure 1;

Figure 3 is an end view of an outlet tube portion of the sprayhead of Figure 1;

Figure 4 is a fragmentary sectional view taken generally along the line 4-4 of Figure2; Figure 5 is an elevational view, partially in section, of a second embodiment of a sprayhead assembly according to the present invention;

Figure 6 is an elevational view, partially in section, of a third embodiment of a sprayhead assembly according to the present invention which illustrates an orifice plate in solid lines and additional orifice plates in phantom lines;

Figure 7 is a sectional view taken generally along the line 7-7 of Figure 6; Figure 8 is an elevational view, partially in section, of a fourth embodiment of a sprayhead assembly according to the present invention;

Figure 9 is a sectional view taken generally along the line 9-9 of Figure 8 ; Figure 10 is a portion of a spray pattern, after such spray pattern has impacted a planar surface, produced by a sprayhead assembly not including any of the restrictions illustrated by Figures 2, 5, 6 or 8; and

Figure 11 is a portion of a spray pattern, after such spray pattern has impacted a planar surface, produced by a sprayhead assembly embodying a restriction illustrated by Figures 2, 5, 6 or 8.

Best Mode for Carrying Out the Invention

Referring now to Figures 1 and 2, there is shown a conventional aerosol container 1 which includes a neck portion 3 in which is mounted a valve 5 which may be one of many types well known in the art. The valve 5 includes a dip tube (not shown) which extends to the bottom of the container 1 in order that the entire contents of the container 1 may be used.

A sprayhead assembly 7 embodying the present invention is inserted into the container valve 5 and includes a sprayhead 9 and a nozzle outlet tube 11 having interconnected through-passageways terminating in an elongate nozzle opening 13 through which the contents of the container 1 may flow to form a spray 15. The sprayhead 9, best seen in Figure 2, includes an inlet stem 17 and an outlet- bore 19 oriented at an angle of approximately 100 degrees respect to the inlet stem 17. The inlet stem 17 has a cylindrical wall 21 which is cut in its lower region to form a metering slot 23. The inlet stem 17 serves to actuate the container valve 5 when the sprayhead 9 is depressed, and the metering slot 23 regulates the flow of the container 1 contents into the sprayhead 9. The contents of the container 1 flow through the metering slot 23 into a cylindrical inlet passageway 25 formed by the cylindrical wall 21 and the body 27 of the sprayhead 9. The passageway 25 terminates in a cylindrical chamber 29 which is intersected by and communicates with the outlet bore 19.

The foregoing structure is conventional and the most common industry construction. If desired, however, the inlet stem 17 may be incorporated into the container valve 5 and the sprayhead 9 provided with a female inlet. Either construction may be used in conjunction with the present invention. The sprayhead 9 may be either machined or molded from any suitable material including metal or plastic, but preferably is molded in plastic due to cost considerations

and the ability of plastic to resist chemical attack.

Figures 1-4 illustrate the preferred embodiment of the invention in which a restriction 41 defining an orifice 43 is incorporate between the cylindrical chamber 29 and the outlet bore 19. The restriction 41 is preferably molded as an integral part of the sprayhead body 27, but may be adhesively bonded or welded in place. The restriction 41 is formed as an annular ring defining the central orifice 43 which has a cross-sectional area less than either the inner cross-sectional area of the outlet tube 11 or the cross-sectional area of the inlet passageway 25 and which is approximately equal to the cross-sectional area of the nozzle opening 13-

The nozzle outlet tube 11 includes a cylindrical body portion 45 press fitted into the outlet bore 19 to contact the restriction 41 and a flattened tip portion 47 in which the nozzle opening 13 is formed. The outlet tube ^' 11 may be retained in the bore 19 by friction, and thus be removable, or may be adhesively bonded or welded in place. The nozzle opening 13 is formed by the intersection of a cylindrical passageway 49 extending centrally through the outlet tube 11 and a transverse tapered groove 51.

The preferred diametrical dimension of the orifice 43 has been empirically determined to be 1.0 mm when used in conjunction with an outlet tube passageway 49 having a diameter of 1.5 mm and an inlet stem passageway 25 having a diameter of between 1.5 and 3 mm. The preferred length of the outlet passageway 49 is approximately 14.7 mm. The outlet passageway 49 terminates in a conical taper 53 having an included angle of approximately 90 degrees, and the nozzle opening 13 is formed by transversely intersecting the outlet passageway taper 53 with the tapered groove 51 having sides 55 and 57 disposed at an included angle of approximately 90 degrees. The groove 51 intersects the outlet passageway taper 53 to a depth substantially equal to the length of the taper 53. The elongate opening 13 thus formed, and best seen in Figure 3,

corresponds to two skewed, intersecting parabolas and has a substantially longer dimension along the groove 51 than transverse to the groove 51. Preferred opening dimensions are 1.5 mm along the groove 51 and 0.8 mm transverse to the groove 51.

The groove sides 55 and 57 form a terminal surface for the outlet tube 11. Flanking the groove 51 are coplanar flat lands 59 and 61. The shape of the tip portion 47 of the outlet tube 11 away from the groove 51 does not influence the shape of the spray 15 exiting the nozzle opening 13 and is, therefore, not critical to tbe present invention. The lands 59 and 61 may be, for example, concave, convex, angled back from the groove 51 or may assume any configuration which does not interfere with the groove 51 or the spray 15. It is important, however, that the groove 51 extend at least a substantially longer distance than the length of the opening and preferably across the entire width of the tip 47, so that air can enter the groove 51 and merge with the spray 15 to facilitate dispersion of the sprayed material.

While the outlet passageway 49 preferably terminates in a conical taper 53 because such a shape is easy to form, the passageway 49 may terminate in a reduced section which is parabolic, hyperbolic or spherical in side-section. . It is thought that a reduced section which is parabolic in side-section and elliptical in cross-section in the manner described in U. S. Patent No. 4,097,000 might prove to be advantageous. However, these shapes are somewhat difficult to form, and very satisfactory results are obtained if the reduced section is conical in side-section, as illustrated.

Figure 5 illustrates a second embodiment of a sprayhead assembly 63 according to the present invention which includes a sprayhead 65 identical to the sprayhead 9 illustrated in Figure 2. An outlet tube 67 is modified to include an outlet chamber 69 which extends from the end 71 of the outlet tube 67 contacting a restriction 73, which

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defines an orifice 74, to an outlet passageway 75 which communicates between the outlet chamber 69 and a nozzle opening 77 which is the same size and shape as the nozzle opening 13 of Figure 2. An outlet chamber 69 having a diameter of 1.9 mm and a length of 12.7 mm used in conjunction with an outlet passageway 75 having a diameter and length of 1.5 mm and 2 mm, respectively, has been found to produce an acceptable fan spray pattern very nearly as uniform as that produced by the sprayhead assembly 7 of Figure 2.

Figure 6 illustrates yet another embodiment of a sprayhead assembly 79 according to the present invention which includes a sprayhead 81 which is generally the same as the sprayheads 9 and 65 described above, except that the sprayhead 81 has an annular shoulder 83 in place of the restriction 41 or 73, which serves merely to limit the travel of an outlet tube 85 as it is inserted into the sprayhead 81. The outlet tube 85 includes an outlet chamber 87, an outlet passageway 89 and a nozzle opening 91 which are identical in all respects to the outlet chamber 69, outlet passageway 75 and nozzle opening 77 of the sprayhead assembly 63 of Figure 5 except that the length of the outlet tube 85 is increased to accommodate an outlet chamber 87 22.1 mm in length. Centered along the length of the outlet chamber 87 is a restriction 93 formed as an annular plate which defines an orifice 95 coaxial with the outlet passageway 89 and the nozzle opening 91. The restriction plate 93 is preferably made of plastic, as is the outlet tube 85, and is secured within the outlet chamber 87 either by press fitting, adhesive bonding or welding. Suitable dimensions for the restriction plate 93 and the orifice 95 have been found to be 1 mm in width and 1.25 mm in diameter, respectively.

When spraying particularly viscous solutions, it has been found that spray pattern uniformity may be enhanced by providing more than one restriction plate 93 within the outlet chamber 87. In this instance, a

plurality of plates 93 (indicated in phantom lines) may be inserted into the outlet chamber 87 and spaced equally along the length of the outlet chamber 87. Although one and three plates 93 have been illustrated, two plates 93 produce acceptable results and is is contemplated that more than three plates 93 could be employed if located symmetrically within the chamber 87 and spaced equally along the length of the outlet chamber 87.

A final embodiment is illustrated by Figures 8 and 9 which show a sprayhead assembly 97 including an outlet tube 99 which has dimensions so as to provide an outlet chamber 101 having a diameter of 1.9 mm and a length of 22.1 mm. The tube 99 is crimped or molded to form a rectangular orifice 103, the longitudinal center of which is located 11 mm from the end of the outlet tube 99 inserted in a sprayhead 105. The orifice 103 is approximately 2 mm in length and, as best seen in Figure 9, is rectangular with rounded ends in cross-section and has a dimension between flat surfaces 107 and 109 of 0.75 mm. In this instance, the dimensions and shapes of the associated sprayhead 105, outlet passageway 111 and nozzle opening 113 are the same as the sprayhead 81, outlet passageway 89 and nozzle opening 91 of Figure 6. The embodiment of Figure 8 has been shown to produce an acceptable fan spray pattern and may additionally provide the advantage of reduced cost.

Figures 10 and 11 illustrate the efficacy of providing an orifice 43, 74, 95 or 103 located within the sprayhead assembly 7, 63, 79 or 97 between the container 1 and the nozzle opening 13, 77, 91 or 113. Figure 10 illustrates a portion of a fan spray pattern 115 produced by a sprayhead assembly similar to that of Figure 2, but not including the restriction 41, as it would appear when sprayed from above onto a horizontal surface from a container 1 held at approximately 45 degrees with the nozzle opening 13 approximately 150 mm from the surface.

The spray pattern 115 is distinguished by sharply defined and stringy margins or "tails" 117 on both ends,

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and areas of light coverage 119 toward the ends of the pattern 115. Also, the amount of material sprayed is found to be much heavier toward the top of the pattern 115 than toward the bottom. Figure 11 illustrates a fan spray pattern 121 produced under the same conditions by a sprayhead assembly 7, 63, 79 or 97 including any of the orifices 43, 74, 95 or 103 illustrated by Figures 2, 5, 6 or 8. The spray pattern 121 of Figure 11 is distinguished from the spray pattern 115 of Figure 10 by the absence of tails 117 and much less severe areas of light coverage 119. There is generally found to be one area of light coverage 123 located in the bottom half of the spray pattern 121, but this area 123 is found to contain more sprayed material than the areas of light coverage 119 in the spray pattern 115 of Figure 10.

In addition, the spray pattern 121 produced when an orifice 43, 74, 95 or 103 is used has been found to be more uniform end-to-end than the spray pattern 115 produced by a sprayhead assembly not containing an orifice 43, 74, 95 or 103.

The difference between the spray patterns 115 and 121 of Figures 10 and 11 are borne out by the following examples which offer comparisons between the fan spray patterns 121 produced by the various embodiments of the sprayhead assemblies 7, 63, 79 or 97 described herein and a fan spray pattern 115 produced by a sprayhead assembly similar to Figure 2, but containing no restriction 41. These examples are offered to aid understanding of the present invention and are not be be construed as limiting the scope thereof.

EXAMPLES 1-7 A solution of polychloroprene contact adhesive in methylene chloride was prepared using the ingredients and amounts shown below in TABLE I.

TABLE I Ingredient Weight ( grams ) 60 to 80 Mooney viscosity 6 . 8 polychloroprene copolymer^ t-Butyl phenolic resin 3 , . 4 Magnesium oxide 1. . 4 Water 0. . 07 Methylene chloride 68 , . 4

¹ "Neoprene AC", commercially available from E. I. du Pont de Nemours Co.

This formulation was placed in a 475 cm3 aerosol container 1 and capped with a conventional can valve 5. The container 1 was filled with 24 g of dimethyl ether through the valve 5, thereby providing an 11.1 percent adhesive solids level in the container 1. The pressure • inside the aerosol container 1 reached approximately 0.17 megapascals. The sprayhead assemblies 7, 63, 79 and 97 of Figures 2, 5, 6 and 8 and a sprayhead assembly similar to that of Figure 2, but not including the ^' restriction 41, were then sequentially placed on the container valve 5 and for each the container 1 was held at an angle of approximately 45° with the nozzle opening 13, 77, 91 or 113 approximately 150 mm above a foil sheet located on a horizontal surface. The above-identified solution was sprayed on the foil and allowed to dry, after which the spray pattern was cut into five equal widths, each comprising 20% of the pattern dimension transverse to the direction of sprayhead motion. Each width was weighed, the material removed with a solvent, and the widths then dried and re-weighed _. to obtain the amount of adhesive material originally on each width.

In this manner the uniformity of the spray pattern 121 produced by each of the embodiments of the present invention could be compared to each other and to a sprayhead assembly not including a restriction. The

results of those comparisons are set out below in TABLE II, which includes the example number, the sprayhead assembly 7, 63, 79 or 97 identified by Figure Number and the amount of material in one-fifth of the spray pattern expressed as a percentage of the total amount of material sprayed.

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TABLE II

Material in One-Fifth of Spray Pattern Width

Sprayhead Assembly (% of total)

Ex. No. (Figure No. ) Away from Container — -> Toward Container

1 2 18.3 11.9 23.9 22.0 23.9

2 5 22.6 23.8 23.8 10.7 19.0

3 6 23.8 22.6 25.0 10.7 17.9 (one orifice)

4 6 19.1 12.4 20.2 18.0 30.3 (two orifices)

5 6 11.0 11.0 15.1 39.7 23.3 (three orifices)

6 8 25.8 16.5 18.6 13.4 25.8

7 No Restriction 34.3 32.4 12.7 7.8 12.5

A perfect spray pattern would result in each one-fifth of the spray pattern containing exactly 20 percent of the total amount of material sprayed. While none of the sprayhead assemblies 7, 63, 79 or 97 reached this level of perfection, the examples show that a sprayhead assembly 7, 63, 79 or 97 containing any one of the embodiments of the orifice 43, 74, 95 or 103 described above produced a more uniform fan spray pattern than did the sprayhead assembly which contained no orifice. The particular nozzle opening 13, 77, 91 and 113 configuration described above produces by itself a commercially acceptable fan spray pattern when spraying soluble elastomeric adhesive polymers at low pressures, and, as has been demonstrated, the various embodiments of the restriction 41, 73, 93 and 103 enhance the uniformity of the spray pattern produced. This sprayhead structure permits polymeric adhesives in solution to be sprayed at typical aerosol container pressures of between approximately 0.14 and 0.69 megapascals, as opposed to the approximately 6.9 megapascals necessary when using airless spray gun equipment. It is thought that this ability to spray at low pressures and the dramatic difference in pressures is at least partially attributable to the fact that the propellant is in solution with the adhesive and that a portion of the propellant is sprayed along with the adhesive solution.

Propellants which have been used advantageously have included dimethyl ether, propane, isobutane, chlorofluorocarbons and combinations thereof. Other propellants typically used in aerosol applications such as carbon dioxide or nitrous oxide which do not enter into solution will produce an acceptable spray pattern at low adhesive solids levels, but not at the desirably high levels described herein. In addition to polychloroprene, other materials which have been successfully sprayed using the disclosed structure include noncrosslinked nitrile polymers, natural

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rubber, acrylic resin, butyl rubber, non-crosslinked SBR polymers, crosslinked SBR polymers, butadiene-styrene copolymers, aliphatic segmented polyester, urethane polymers and vinyl chloride-vinyl acetate copolymers. While the present invention has been described in connection with specific embodiments, it is to be understood that the invention is not to be limited to those embodiments. In particular, many preferred shapes and dimensions have been supplied for explanatory purposes only. The invention is intended to cover all alternatives and modifications falling within the spirit and scope set forth in the appended claims.