WO2004096520A1 - ISOLATING MOULD MECHANICAL FUNCTIONS DURING IN-mOULD COATING OPERATION - Google Patents

Abstract

A method for coating a molded article (A) while isolating a mold mechanical function (70) such as an ejector pin assembly includes injecting a molten first composition into a mold cavity (16) defined by a pair of mold members (12,14); allowing the molten first composition to cool or harden in the mold cavity (16) so as to form a molded article (A) having a barrier (66) on a surface (62) thereof that is formed around a mold mechanical function assembly (70) of the pair of mold members (12,14); injecting a second composition into the mold cavity (16) and onto the surface (62) of the molded article (A); and allowing the second composition to flow across the surface (62) to Form a coating (C) on the molded article (A). The second composition is prevented from flowing to the mold mechanical function assembly (70) by the position of the barrier (66) around the mold mechanical function assembly (70).

Description

ISOLATING MOULD MECHANICAL FUNCTIONS DURING IN-MOULD COATING OPERATION

BACKGROUND INFORMATION [0001 ] The present invention relates to a method and apparatus for isolating a mold's mechanical functions during in-mold coating. More particularly, the present invention relates to a method and apparatus for in-mold coating a molded article with an in-mold coating (IMC) composition and preventing that composition from interfering with and/or contacting one or more mechanical functions of the mold used to form the molded article. The present invention finds particular application as a method and apparatus for isolating one or more ejector pins on a mold while coating an article formed in the mold.

[0002] Molded thermoplastic and thermoset articles, such as those made from polyolefins, polycarbonates, polyesters, polystyrenes and polyurethanes, are utilized in numerous applications including those for automotive, marine, recreation, construction, office products, and outdoor equipment industries. Often, application of a surface coating to a molded thermoplastic or thermoset article is desirable. For example, molded articles may be used as one part in multi-part assemblies; to match the finish of the other parts in such assemblies, the molded articles may require application of a surface coating that has the same finish properties as the other parts. Coatings may also be used to improve surface properties of the molded article such as uniformity of appearance, gloss, scratch resistance, chemical resistance, weatherability, and the like. Also, surface coatings may be used to facilitate adhesion between the molded article and a separate finish coat to be later applied thereto.

[0003] Numerous techniques to apply surface coatings to molded articles have been developed. Many of these involve applying a surface coating to articles after they are removed from their molds. These techniques are often multi-step processes involving surface preparation followed by spray-coating the prepared surface with paint or other finishes. In contrast, IMC provides a means of applying a surface coating to a molded article prior to its ejection from the mold.

[0004] Molds used with thermoplastics usually are of a "clam shell" design having mated halves that meet at a parting line. One of the mated halves typically remains stationary whereas the other half typically moves between a closed position and an open, retracted position. To form a molded article, the movable half is moved to its closed position and held under a clamping force, thereby forming a contained molding cavity. Molten material is injected into the cavity. The molded article is formed by thoroughly filling the cavity with the molten material and allowing the material to sufficiently cool and solidify. During the entire molding process, the movable mold half is maintained in its closed position. After molding, the mold halves can be opened and a finished, molded article ejected therefrom.

[0005] Owing to differences in mold design and molding conditions, processes where the mold is cracked or parted prior to injection of a coating composition generally are not used for the IMC of injection molded thermoplastics. When molding thermoplastics, it is generally necessary to maintain pressure on the movable mold half to keep the cavity closed and prevent material from escaping along the parting line. Further, maintaining pressure on the thermoplastic material during molding, which also requires keeping the cavity closed, often is necessary to assist in providing a more uniform crystalline or molecular structure in the molded article. Without such packing (i.e., pressure maintenance), physical properties of the molded thermoplastic article tend to be impaired.

[0006] Because injection molding does not permit the mold to be parted or cracked prior to injection of the IMC composition into the mold cavity, the IMC composition must be injected under sufficient pressure to compress the article in all areas that are to be coated. The compressibility of the molded article dictates how and where the IMC composition covers it. The process of coating an injection molded article with a liquid IMC composition is described in, for example, U.S. Patent No. 6,617,033 and U.S. Patent Publication Nos. 2002/0039656 A1 and 2003/0082344 A1.

[0007] A method and apparatus used to physically inject liquid IMC composition into the molding cavity of an injection molding machine during the molding process, also referred to herein as a dispense-and-control method and apparatus, is described in commonly owned Int'l Appl. No. PCT/US2003/O33186 (WO ) the teachings of which relating to that method and apparatus are incorporated herein by reference. The dispense and control apparatus provides a delivery system for injecting an IMC composition into the cavity of a pair of mold halves on an injection molding machine and a means for controlling the delivery system.

[0008] As the IMC composition is injected into the mold cavity and onto the molded article, the flow of the IMC composition can be controlled such that only desired surfaces or portions of surfaces of the article are coated and that those surfaces are optimally coated. Further, the flow of the IIMC composition can be controlled so as to limit it from escaping through the parting line or entering the area near the resin injection orifice.

[0009] For example, one method for selectively controlling flow of IMC composition flow is described in US 2003/0082344 A expressly incorporated herein by reference, which teaches methods for controlling the flow and thickness of an IMC composition as it is injected into a mold cavity and onto a molded article. Generally, by controlling the thickness or depth of various areas or sections of the molded article, desired areas of the article can be preferentially coated. Specifically, when a molded article is provided with an area of increased relative thickness at or near the location of the IMC composition injection, flow of the IMC composition is promoted. When the molded article is provided with a runner section or preferred flow channel, IMC composition flow over the surface of the molded article is promoted. Additionally, when the molded article is provided with a containment flange, the flange acts as a barrier and prevents the IMC composition from leaking or seeping off a desired surface and/or out of the mold cavity.

[0010] Another method for selectively controlling in-mold coating flow is described in US 2003/0077426 A, expressly incorporated herein by reference, which teaches the use of "flow zones" near the IMC composition injection inlet area to promote the flow of IMC composition from the injection inlet area. Still another method for selectively controlling IMC composition flow is described in US 2003/0099809 A, expressly incorporated herein by reference, which discloses a containment flange functioning like the containment flange described in the US 2003/0077426 A publication but with the added feature of being configured to be removable from the coated thermoplastic article. The removable flange is able to be easily removed. Yet another method for selectively controlling IMC composition flow is described in US 2003/0077425 A publication, expressly incorporated herein by reference, which discloses the use of a mold structure formed as part of the molded article that provides a barrier preventing IMC composition flow into the resin injector orifice, gate pin assembly, or the like.

[0011 ] Although the above-discussed references generally teach how to control flow of an IMC composition as it is injected onto a molded article, further improvements in such flow control are considered desirable.

[0012] One problem not specifically addressed by these references is that of an IMC composition flowing along the surface of a molded article that is to be engaged by a mold ejector pin. Movable mold ejector pins often require a clearance between the pin and the mold half within which the pin moves. In conventional mold arrangements, the clearance between the ejector pin and the walls of the mold half around the ejector pin is 0.05 mm (about 0.002 in.). Many IMC compositions are able to flow into gaps that are greater than 0.025 mm (about 0.001 in.) and, as a result, when coating a molded article surface adjacent an ejector pin, the IMC composition is able to flow into the clearance gap. When an IMC composition flows into the clearance area between the pin and the surface of the mold half around the pin, movement of the pin may be hindered or entirely restricted, thereby preventing the pin from properly ejecting a molded part.

[0013] Thus, there is a need to control the flow of an IMC composition on a surface to be coated that is adjacent an ejector pin for the purposes of isolating the ejector pin and preventing IMC composition from interfering with the functionality of the ejector pin. Similarly, there is a need to isolate other mechanical function parts that may be incorporated into the mold halves adjacent a surface to be coated. For example, the mold halves may include, without limitation, cores, core pins, slides, gate pins and the like. If clearance gaps exist between these components and the mold halves within which they are seated are greater than about 0.025 mm (0.001 in.), flow control around these components is needed for purposes of isolating these components from the IMC composition.

SUMMARY OF THE INVENTION [0014] In one aspect, the present invention provides a method for coating a molded article while isolating a mold mechanical function. The method includes injecting a molten first composition into a mold cavity defined by a pair of mold members; allowing the molten first composition to cool or harden in the mold cavity so as to form a molded article having a barrier on a surface thereof that is formed around a mold mechanical function assembly of the pair of mold members; injecting a second composition into the mold cavity and onto the surface of the molded article; and allowing the second composition to flow across the surface to form a coating on the molded article while preventing the second composition from flowing to the mold mechanical function assembly by the position of the barrier therearound.

[0015] In another aspect, the present invention provides an apparatus for injection molding an article and coating the same. The apparatus includes a mold defining a mold cavity. The mold includes at least one depression formed around at least one mold mechanical function assembly. A first composition injector is fluidly connected to the mold cavity for injecting a first composition into the mold cavity to form a molded article therein. The molded article includes at least one barrier formed from at least one depression. A second composition injector also is fluidly connected to the mold cavity for introducing a second composition to coat a surface of the molded article in the mold cavity. The one or more barriers are positioned to prevent coating of a portion of the surface surrounded by the barrier(s) and adjacent the at least one mold mechanical function assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention.

[0017] Fig. 1 is a side view of one embodiment of a molding apparatus having a first, movable mold half and a second, stationary mold half. [0018] Fig. 2 is a partial cross-sectional view of the molding apparatus of

Fig. 1 showing a mold cavity surrounded by ejector pins provided in the mold halves.

[0019] Fig. 3 is a cross-sectional view of one of the ejector pins having a depression formed in a mold surface adjacent thereto. [0020] Fig. 4 is a partial cross-sectional view of the molding apparatus of

Fig. 1 showing a molded article formed in the mold cavity between the mold halves. [0021 ] Fig. 5 is a partial cross-sectional view of the molding apparatus of Fig. 1 showing an IMC composition injected into the mold cavity and onto the molded article.

[0022] Fig. 6 is a cross-sectional view of alternate depressions for use adjacent a mold's mechanical functions.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0023] Referring now to the drawings wherein the showings are for purposes of illustrating one or more preferred embodiments of the invention only and not for purposes of limiting the same, Fig. 1 shows a molding apparatus or injection molding machine 10 including a first mold half 12 and a second mold half 14. First mold half 12 preferably remains in a stationary or fixed position relative to second movable mold half 14. In Fig. 1 , movable mold half 14 is shown in an open position, although it is movable to a closed position wherein first and second mold halves 12,14 mate with one another to form a plurality of contained mold cavities 16 therebetween. More specifically, mold halves 12,14 mate along surfaces 18 and 20 when movable mold half 14 is in its closed position forming a parting line 22 (Fig. 2) therebetween and around part cavities 16.

[0024] Movable mold half 14 reciprocates along a generally horizontal axis relative to mold half 12 by action of clamping mechanism 24 with clamp actuator 26 such as through a hydraulic, pneumatic or mechanical actuator as known in the art. Preferably, the clamping pressure exerted by clamping mechanism 24 is capable of generating an operating pressure in excess of the pressures generated or exerted by either one of first composition injector 30 and second composition injector 32. For example, pressure exerted by clamping mechanism 24 can range from 14 MPa (about 2,000 psi) to 105 MPa (about 15,000 psi), preferably from 25 MPa (about 4,000 psi) to 85 MPa (about 12,000 psi), and more preferably from 40 MPa (about 6,000 psi) to 70 MPa (about 10,000 psi) of the mold surface.

[0025] With additional reference to Fig. 2, mold halves 12,14 are shown in a closed position abutting or mating with one another along parting line 22 to form mold cavity 16 having a finite and/or substantially fixed volume. The design of cavity 16 can vary greatly in size and shape according to the desired end product or article to be molded. Mold cavity 16 generally has a first surface 34 on second mold half 14, upon which a show surface of an article is formed and a corresponding or opposite second surface 36 on first mold half 12. First mold half 12 defines a first orifice 38 connecting to cavity 16 that allows the first composition injector 30 to inject its composition into cavity 16. Similarly, second mold half 14 defines a second orifice 40, also connecting to cavity 16, that allows the second composition injector 32 (Figure 1) to inject its composition into cavity 16.

[0026] First composition injector 30 is that of a typical injection molding apparatus known to the ordinarily skilled artisan. More specifically, first composition injector 30 is generally capable of injecting a thermoplastic or thermosetting composition, generally a resin or polymer, into mold cavity 16 to form a molded article. Owing to space constraints, first injector 30 is positioned to inject material from fixed half 12 of the mold, although first composition injector 30 could be reversed and placed in movable mold half 14. Second composition injector 32 is generally capable of injecting an IMC composition into mold cavity 16 to coat the molded article formed therein. In the illustrated embodiment, second injector 32 is shown positioned in movable mold half 14, although it could be positioned in stationary mold half 12.

[0027] In Fig. 1 , first composition injector 30 is shown in a "backed off" position but can be moved horizontally so that a nozzle or resin outlet 42 of first injector 30 mates with mold half 12. In the mated position, injector 30 is capable of injecting its contents into mold cavity 16. For purposes of illustration only, first injector 30 is shown as a reciprocating-screw machine wherein a first composition can be placed in a hopper 44 and a rotating screw 46 can then move the first composition through a heated extruder barrel 48, where the first composition is heated above its melting point. As heated material collects near the end of barrel 48, screw 46 acts as an injection ram and forces the material through nozzle 42 and into mold cavity 16. Nozzle 42 optionally has a valve (not shown) at the open end thereof and screw 46 generally has a non-return valve (not shown) to prevent backflow of material thereinto. [0028] First composition injector 30 is not meant to be limited to the embodiment shown in Fig. 1 but can be any apparatus capable of injecting a thermoplastic composition into mold cavity 16. For example, the injection molding machine can have a mold half movable in a vertical direction, such as in a stack mold with center injection. Other suitable injection molding machines include many of those available from Cincinnati-Milacron, Inc. (Cincinnati, Ohio), Battenfeld Injection Molding Technology (Meinlerzhagen, Germany), Engel Machinery Inc. (York, Pennsylvania), Husky Injection Molding Systems Ltd. (Bolton, Canada), BOY Machines Inc. (Exton, Pennsylvania) and others.

[0029] Second composition injector 32 is generally capable of injecting an IMC composition into mold cavity 16 to coat the molded article formed therein. More specifically, second composition injector 32 includes a nozzle 50 that extends through movable mold half 14 and communicates with cavity 16. Nozzle 50 includes a nozzle passageway 52 for injecting the second composition into cavity 16 and a nozzle pin 54 for controlling fluid communication therethrough. Pin 54 normally is urged toward a closed position wherein fluid communication between passageway 52 and cavity 16 is prevented and pin 54 is selectively movable to an open position wherein fluid communication is permitted between passageway 52 and cavity 16.

[0030] A dispense and control apparatus (not shown) is capable of being connected to molding apparatus 10 and, specifically, second injector 32 for providing IMC capabilities and controls. One suitable dispense and control apparatus is taught and described in the above-referenced int'l appl. no. PCT/US203/033186. A suitable IMC composition is disclosed in U.S. Pat. No. 5,777,053.

[0031 ] Mold halves 12,14 include one or more mold function assemblies including, in the illustrated embodiment, ejector pin assemblies for ejecting molded articles from mold halves 12,14. More specifically, first mold half 12 has ejector pin assemblies 60 that each include a bore hole 62 formed in the surface 36 and an ejector pin 64 received in bore holes 62. Bore holes 62 communicate with cavity 16 and extend into mold half 12. Ejector pins 64 each are movable from a first retracted position (the position shown in Fig. 2) to a second extended position. In the retracted position, ends 66 of pins 64 are flush with surface 36. In the extended position, pins 64 extend from holes 62 and ends 66 protrude from surface 36 into mold cavity 16.

[0032] Second mold half 14 also has ejector pin assemblies 70 that are similar to the ejector pin assemblies 60 of first mold half 12. Assemblies 70 each include a bore hole 72 formed in surface 34 and an ejector pin 74 received in bore hole 72. Bore holes 72 communicate with cavity 16 and extend into mold half 14. Pins 74 each are movable from a first retracted position (the position shown in Fig. 2) to a second extended position. In the retracted position, ends 76 of pins 74 are flush with surface 34 and, in the extended position, pins 74 extend from th holes 72 and ends 76 protrude from surface 34 into mold cavity 16.

[0033] Between pins 64,74 and respective surfaces defining bore holes 62,72, an annular clearance gap is provided to allow pins 64,74 to move generally with ease between their retracted and extended positions. The width of the clearance gap is often 0.05 mm (about 0.002 in.), which is small enough that most thermoplastic compositions injected into cavity 16 are unable to enter the gap.

[0034] Surrounding ejector pin assemblies 70 of the first surface, containment depressions or indents 80 are provided in mold half 14 for purposes of preventing IMC compositions injected through nozzle 50 from entering the clearance gaps of ejector pin assemblies 70. IMC compositions are often capable of entering gaps larger than 0.025 mm (about 0.001 in.) and thus need to be prevented from accessing the clearance gaps around pins 74. If an IMC composition were permitted to enter the clearance gaps, it could obstruct the functioning or movement of ejector pin assemblies 70. [0035] In one embodiment, depressions 80 are generally annular grooves or rings that surround each of pin assemblies 70. Depressions 80 can be formed by machining into mold half 14 or, alternatively, by casting mold half 14 with depressions 80 therein. The annular shape allows depressions 80 to completely surround pin assemblies 60,70 and generally form a complementary shape relative to the pin assemblies 60,70. Other shapes are possible, e.g., rectangular, triangle, etc., and all shapes are to be considered within the scope of the present invention.

[0036] Referring to Fig. 3, in one preferred embodiment, depressions 80 have a generally rectangular cross-section including a depth dimension 82 and a width dimension 84. When cavity 16 is filled with a first composition from first composition injector 30, depressions 80 are filled with the first composition. Thus, the first composition will form a flange, projection or raised or standing rim around the entire perimeter of pin assemblies 60,70 that is formed integrally with a molded article formed in cavity 16. As is described in more detail below, depressions 80 and the first composition filled therein will together form a barrier that will block or prohibit IMC composition from passing thereby. Because depressions 80 completely surround pin assemblies 60,70, the IMC composition is blocked or prevented from reaching pin assemblies 60,70. The barriers, i.e., the depressions and the first composition filled therein, use the compressibility of the first composition, or relative lack thereof, to prevent an IMC composition from reaching pin assemblies 60,70.

[0037] To make a coated article, with reference to Fig. 1 , a thermoplastic first composition is placed in hopper 44 of molding apparatus 10. Any suitable thermoplastic composition that can be injection molded is suitable for use with or in the present invention. Examples of suitable thermoplastic materials include, but are not limited to, polyesters such as polyethylene terephthalate (PET), nylon, acrylonitrile butadiene styrene (ABS), polystyrene, polyacrylate, polyphenylene sulfide, polysulfone, polyurethane, styrene-acrylonitrile, polycarbonate, acrylic, acetal, polyolefins such as polyethylene and polyethylene, polypropylene, and polyvinyl chloride (PVC). In addition, the thermoplastic material may be fiber- reinforced plastic and/or a glass-filled polymer. The foregoing list is not meant to be exhaustive but only illustrative of the various thermoplastic materials useful in the practice of the invention. [0038] Prior to injecting the first composition mold halves 12,14 are closed by clamp mechanism 24 to create contained molding part cavities 34,36. In the closed position, clamping mechanism 24 maintains a clamping pressure sufficient to maintain mold halves 12,14 in closed relation even when the first and second compositions are injected under pressure into part cavities 34,36. Also prior to injecting first composition, first injector 30 is moved into nesting or mating relation with first mold half 12.

[0039] Through conventional means, i.e., using heated extruder barrel 48 and rotating screw 46, first injector 30 heats the first composition above its melting point and directs the heated first composition toward nozzle 42 of first injector 30. If nozzle 42 is equipped with a nozzle valve, it is moved to an open position for a predetermined amount of time to allow a corresponding quantity of the first composition to fill molding cavity 16. Screw 46 provides an injection pressure or force that urges the first composition into mold cavity 16 until the nozzle valve is returned to its closed position. The first composition is urged into mold cavity 16 until it is filled and packed. This includes filling and packing depressions 80 with the first composition. With additional reference to Figure 4, once cavity 16 is filled and packed, the molded first composition is allowed to cool thereby forming a molded article A in cavity 16.

[0040] The molded article or substrate A formed in mold cavity 16 from the first composition has at least a show surface or front side 62 adjacent first surface 34 and an opposite surface or back side 64 adjacent second surface 36. Show surface 62 is the preferred viewing surface of the substrate. Additionally, article A has annular barrier rims 66 formed by depressions 80. Fig. 4 also illustrates an injection sprue 68 formed from the first composition and attached to article A. Injection sprue 68 is generally removed after article A has been ejected or removed from mold halves 12,14 as described in more detail below.

[0041 ] After the first composition has been injected into mold cavity 16 to form article A and the intended surface or surfaces of article A to be coated have cooled below the melt point or otherwise reached a temperature or modulus sufficient to accept or support an IMC composition, a predetermined amount of an IMC composition is ready to be injected into moid cavity 16 and onto molded article A from nozzle 50 of second composition injector 32. If the IMC composition is cured by heat then it would be desirably injected before the surfaces of the molded articles have cooled too much such that curing would be inhibited. To inject the coating composition, with additional reference to Fig. 5, nozzle pin 54 of nozzle 50 is moved to an open position allowing fluid communication between a fluid reservoir (not shown) of second injector 32 and mold cavity 16 and an IMC composition C is injected through nozzle 50 into mold cavity 16 and onto show surface 62.

[0042] IMC composition C flows radially outward onto show surface 62 and coats a predetermined portion thereof at least by compressing the substrate. More specifically, as the IMC composition C flows or spreads across show surface 62, IMC composition C encounters barrier rims 66 of article A. IMC composition C will attempt to flow up the height of barrier rims 66 by compressing the width thereof. However, the widths of each of barrier rims 66 are relatively thin and thus are sufficient to prevent the IMC composition from flowing into ejector pin assemblies 70 at least because the rim width is relatively incompressible and forms a seal or barrier to coating flow. That is, the IMC composition will not flow from a substrate or article area having a greater thickness or depth to an area of relatively less thickness if a sufficient ratio of compression differential is maintained. [0043] The barrier rim surrounding each ejector pin assembly 70 may alternatively have both varying heights and/or widths and thus may have very different shapes or designs other than barrier rims 66 shown and described herein. In the illustrated embodiment, barrier rims 66 each have two substantially equal height walls formed at substantially perpendicular angles relative to show surface 62 and a substantially constant width. Other shapes are possible by altering the shapes of depression 80 in mold half 14. In Fig. 6, several depressions in mold halves are shown, each having a varying shape. Depression 180 shows an alternative barrier design having a tapered rim with one wall substantially perpendicular to the mold surface and a slanted wall at about a 45° angle relative thereto. The upper, thinnest portion of a rim formed in depression 180 will be substantially incompressible by the IMC composition, and thus the IMC composition substantially cannot flow into ejector pin assemblies surrounded by depression 180. Similarly, depression 280 shows an alternative barrier design having a reversed taper. Depression 380 shows an alternative barrier design having a double taper. The specific design of the barrier rim is only limited to mold cavity constraints wherein it is desirable to allow the molded article with barrier to be easily removed from the mold cavity after molding and coating.

[0044] Immediately or very shortly after the IMC composition is fully injected into mold cavity 16, valve 54 of second injector 32 is allowed to return to its closed position (shown in Fig. 4), thereby preventing further injection of IMC composition into mold cavity 16. The mold is not opened or undamped before the IMC composition is applied. That is, mold halves 12,14 maintain parting line 22 and generally remain substantially fixed relative to each other while both the first and second compositions are injected into mold cavity 16. Thus, the substantially fixed volume of mold cavity 16 is constant and maintained throughout the molding and coating steps. After article A has been coated with IMC composition C and the coating has cured, molded article A can be ejected from mold halves 12,14. The cure is optionally heat activated, from sources including the articles themselves or mold halves 12,14 which are at or above the curing temperature of the IMC composition. Cure temperature will vary depending on the specific IMC composition utilized. To eject the coated article from mold halves 12,14, movable mold half 14 is moved to the open position and ejector pins 64,74 are moved to their extended positions forcing article A from mold cavity surfaces 34,36.

[0045] Although the present invention has generally been shown and described for use with one or more ejector pins, it is contemplated that the invention could be used in other applications where isolation of a mechanical mold part from an injected IMC composition is desirable. Isolation may be particularly desirable when a mechanical mold assembly or component has a gap into which the IMC could seep. For example, the barrier design of the present invention could be used to isolate a mold's core pins, slides, gate pins, etc.

Claims

CLAIMSThat which is claimed is:

1. A method for coating a molded article (A) while isolating a mold mechanical function assembly (70), comprising: a) injecting a molten first composition into a mold cavity (16) defined by a pair of mold members (12,14); b) allowing said molten first composition to cool or harden in said mold cavity (16) to form a molded article (A) having a barrier (66) on a surface (62) thereof that is formed around a mold mechanical function assembly (70) of said pair of mold members (12,14); c) injecting a second composition into said mold cavity (16) and onto said surface (62) of said molded article (A); d) allowing said second composition to flow across said surface (62) to form a coating (C) on said molded article (A) while preventing said second composition from flowing to said mold mechanical function assembly (70) by the position of said barrier (66) therearound.

2. The method of claim 1 further comprising ejecting said molded article (A) with said coating (C) from said pair of mold members (12,14) by actuating said mold mechanical function assembly (70).

3. The method of one of claims 1 and 2 wherein the volume of said mold cavity (16) remains substantially constant throughout steps a) to d).

4. The method of any of claims 1 to 3 wherein said mold members

(12,14) remain a substantially fixed distance relative to one another during steps a) to d).

5. The method of any of claims 1 to 4 wherein said mold members (12,14) are not opened or undamped in or between steps a) to d).

6. An apparatus for injection molding an article and coating the same, comprising: a mold (12,14) defining a mold cavity (16), said mold (12,14) including at least one depression (80) formed around at least one mold mechanical function assembly (70); a first composition injector (30) fluidly connected to said mold cavity (16) for injecting a first composition into the mold cavity (16) to form a molded article (A) therein, said molded article (A) including at least one barrier (66) formed from said at least one depression (80); and a second composition injector (32) fluidly connected to said mold cavity (16) for introducing a second composition to coat a surface (62) of said molded article (A) in said mold cavity (16), said at least one barrier (66) positioned to prevent coating of a portion of said surface (62) surrounded by said at least one barrier (66) and adjacent said at least one mold mechanical function assembly (70).

7. The molding apparatus of claim 6 wherein said barrier (66) is an annular rim surrounding said at least one mold mechanical function assembly (70).

8. The molding apparatus of one of claims 6 and 7 wherein said at least one mold mechanical function assembly (70) comprises at least one ejector pin assembly.

9. The molding apparatus of any of claims 6 to 8 wherein said af least one barrier (66) is of a rectangular, a triangular, or a trapezoidal cross-section.

10. The molding apparatus of any of claims 6 to 9 wherein said mold cavity (16) has a volume that remains fixed when said first composition injector (30) injection molds said molded article (A) and when said second composition injector (32) introduces a second composition to coat said molded article (A).