WO2004048068A1

WO2004048068A1 - Method for retrofitting existing molds for use with an in-mold coating system

Info

Publication number: WO2004048068A1
Application number: PCT/US2003/036289
Authority: WO
Inventors: Douglas Mcbain; Elliott Straus; John Thompson
Original assignee: Omnova Solutions Inc.
Priority date: 2002-11-22
Filing date: 2003-11-13
Publication date: 2004-06-10
Also published as: WO2004048068B1; AU2003290839A1

Abstract

A method of modifying an existing mold allows the mold to produce an article having at least one coated surface. The method including evaluating the mold to determine its existing characteristics, the optimal flow of the coating composition to be used, and the optimal location of the coating composition injector and modifying the mold based on the evaluation. The mold can be modified further to control the flow of the in-mold coating composition used to provide the coating.

Description

METHOD FOR MODIFYING EXISTING MOLDS FOR USE WITH AN IN-MOLD COATING SYSTEM

BACKGROUND OF THE INVENTION

The present invention relates to injection molding systems and the use of an in-mold coating (IMC) in these systems; more particularly, to a method for modifying an existing mold to allow it to be used in a system having an IMC apparatus so that an article produced can be coated while in the mold.

Molded thermoplastic or thermoset articles, such as those made from polyolefins, polycarbonate, polyester, polyethylene, polypropylene, polystyrene and polyurethanes, are utilized in numerous applications including those for the automotive, marine, recreation, construction, office products, and outdoor equip- ment industries. Automotive industry applications include, e.g., body panels, wheel covers, bumpers, head and tail lamps, fenders, hoods, and dashboards.

When the surface quality of molded articles does not meet required standards such as those for durability, chemical resistance, and weather resistance, or to facilitate paint adhesion, such articles must be coated. Molds used in connection with injection molding machines are used to produce thermoplastic or thermoset articles. The machine allows a substrate- forming material (typically. a peljetized, granular or powdered plastic material fed from a hopper) to be heated to a temperature above its melting or softening point and, using a filling pressure, injected into a closed mold maintained under a clamping pressure until the mold is substantially full; then, using a packing pressure, the mold is completely filled with the substrate-forming material to form a workpiece. The machine then maintains, under a mold or clamp pressure, the workpiece as it cools until it can be removed from the mold without distortion. (The mold typically is opened and closed either mechanically or hydraulically, usually using a predetermined timing cycle.) Such injection molding probably is the most widely used method of producing plastic parts.

These molds generally have two parts, one of which is stationary and the other movable. The mold cavity formed by these halves generally has a first surface on one mold half upon which a show or finished surface of the molded article will be formed and a corresponding second surface on the other mold half. The stationary half typically houses the cavity section of the mold and is mounted on a stationary platen in contact with the injection section of the cylinder of the injection machine. The movable mold half typically holds the core and ejector mechanism. Injection of substrate-forming material occurs under pressure when the mold is in a closed position. The clamping pressure, i.e., the pressure used to keep the mold closed during injection of the substrate-forming material, must be greater than the pressure used to inject that material.

SUMMARY OF THE INVENTION

Briefly, the present invention provides a method for modifying an existing mold used in connection with an injection molding system to allow the mold to accept an IMC composition without the expense of making a new mold. The modified mold can accept introduction of an IMC composition into its mold cavity, and the IMC composition spreads onto at least one surface of the article formed in the mold cavity. (The mold cavity is defined by first and second mold sections when such sections are in closed relation to one another, and the mold is operable with a molding machine such that the machine actuates one of the first and second mold sections relative to the other between an opened and a closed condition. The mold cavity has an inner surface corresponding with the at least one surface to be coated.) The mold includes at least_ ne nozzle for directing a substrate-forming material into the mold cavity to produce an article having at least one surface to be coated. The method includes the step of determining a point where the coating composition desirably can be contacted with the surface(s) of the article while the article is in the mold cavity and the step of creating in the mold an access hole to accept a nozzle capable of directing coating composition into the mold cavity and onto the surface(s) while the mold sections are in a closed relation. If indicated by the determining step, multiple access holes can be created in the mold so as to accept multiple nozzles capable of injecting coating composition.

The subject method can include many optional variations. The mold can be further modified to counteract heat produced as the coating composition is introduced into the mold cavity and spreads across the surface(s) of the article. Also, the mold can be modified to include means for cooling and/or heating so to assist in the control of flow and/or cure of the coating composition. Additionally, the mold and/or article design can be modified so as to include flow enhancers (to promote) or flow restrictors (to inhibit) flow of the composition across the surface(s) of the article. Other such variations are discussed in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are only for purposes of illustrating certain embodiments of, and are not to be construed as limiting, the invention. FIG. 1 is a side view of a molding apparatus suitable for practicing the method of the present invention.

FIG. 2 is a cross section through a vertical elevation of a mold cavity.

FIG. 3 is a top view of a molded substrate prior to being coated. The substrate is shown having an area of increased thickness to promote and/or channel flow of coating composition;

FIG. 4 and FIG. 5 are, respectively, front and back views of the substrate shown in FIG. 3.

FIG. 6 is a side view of a molded door panel. The door panel is provided with areas of varying depth to channel flow of coating composition. FIG. 7 is the substrate of FIG.4 coated on a show surface thereof.

FIG. 8 is the substrate of FIG. 4 having a coating located. substantially. _ only in a runner section of the show surface.

FIG. 9 is a front elevation view of a substantially flat molded plaque with a substantially flat show surface. FIG. 10 is a front view of a molded substrate with areas of varying thickness illustrated.

FIG. 11 is a plan view of a substrate having a removable, flexible containment flange.

FIG. 12 is a cross section of FIG. 11 through 12-12 illustrating a removable containment flange.

FIGS. 13A through 13D are cross sectional illustrations of molded substrates having removable containment flanges of various configurations. FIG. 14 is a plan view of a substrate having a removable containment flange extending completely around the perimeter of the substrate show surface.

FIG. 15A is a plan view of a substrate having a removable containment flange on the show surface of as well as on the perimeter so as to contain the coating to a predetermined area of the show surface, while FIG. 15B is a cross sectional view of a FIG. 15A through 15B-15B.

FIG. 16 is a cross section of a hypothetical first or stationary mold half of the type shown in FIG. 1.

FIG. 17 A is a front view of a molded substrate containing a readily compressible area at the location where a coating composition is to be injected onto the surface of the substrate, while FIG. 17 B is a cross-sectional side view of FIG. 17A through lines 17B - 17B and illustrates a compressible area below the point of coating composition injection and FIG. 17 C is a front view of the molded substrate of FIG. 17A wherein the substrate has been coated. FIG. 18A is a front view of a molded substrate containing a readily compressible area at the location wherein a coating composition is to be injected onto the surface of the substrate; FIG. 18B is a cross-sectional side view of the plaque shown in FIG. 18A while the molded substrate is still in a mold cavity and a coating composition has been applied to the show surface of the substrate, and FIG. 18C is the front view of the coated article shown in FIG. 18B.

FIG. 19 is a partial schematic view of a molding apparatus capable of in- mold coating a molded substrate. The molding apparatus incorporates a mold runner.

FIG. 20 is a schematic view of a mold cavity having a mold runner and an IMC composition inlet.

FIG. 21 is a schematic view of the mold cavity as shown in FIG. 20 wherein the mold cavity has been filled with a substrate-forming composition and an IMC has been applied thereto. The mold runner having a containment shroud prevents coating composition from entering the injector for the substrate-forming material.

FIG. 22 is a schematic view of a mold runner in a mold half while FIG. 22(a) is a close up view of the containment shroud illustrated in FIG. 22. FIG. 23 and FIG. 24 are schematic views of other mold runners containing a containment shroud.

FIG. 25 is a cross section through a mold half at a vertical section where a mold runner containment shroud is present. FIG. 26 is a partial elevational view of a mold half having a barrier around a gate pin apparatus for preventing an IMC composition from entering a substrate injection device through the gate pin.

FIG. 27 is a partial elevational view of a coated substrate having a barrier which prevents IMC composition from entering the orifice of the injector for the substrate-forming material.

FIGS. 28A-C are partial cross-sectional views through a mold illustrating a gate pin and a barrier for coating composition flow.

FIG. 29 is a partial cross-sectional view through a mold illustrating a coated substrate having a barrier which prevents IMC composition from entering the orifice of the injector for the substrate-forming material.

FIGS. 30A-C are partial cross-sectional views through a coated substrate having barrier rims of varying configurations; and,

FIG 31A-D are flow diagrams showing the flow of IMC composition over a

"show" surface of a molded article.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to the drawings where like numerals indicate like or corresponding parts throughout the several figures, FIG. 1 shows a molding machine 10 which includes a first mold half 20 that preferably remains in a stationary or fixed position relative to a second moveable mold half 30. As can be appreciated, the method of the present invention can be practiced on a wide variety of mold types and styles. Stationary mold half 20 is mounted to a platen 21 of molding machine 10. Moveable mold half 30 is mounted to platen 31 which is mounted to a clamping mechanism 70 of molding machine 10. FIG. 1 shows the mold halves in an open position. Mold halves 20 and 30 can mate, thereby forming a mold cavity 40 therebetween as shown in at least FIG. 2. Mold halves 20 and 30 mate along mold faces or surfaces 24 and 34, respectively, when the molding apparatus is in the closed position, forming a parting line 42. The moveable mold half 30 reciprocates generally along a horizontal axis relative to the first or fixed mold half 20 by action of clamping mechanism 70 with a clamp actuator 72 such as through a hydraulic, mechanical, or electrical actuator as known in the art. The clamping pressure exerted by the clamping mechanism 70 should have an operating pressure in excess of the pressures generated or exerted by the first composition injector and the second composition or IMC injector which will be discussed in greater detail below. For example, pressure exerted by clamping mechanism 70 can range generally from 14 MPa (about 2,000 psi) to 103 MPa (about 15,000 psi), preferably from 27 MPa (about 4,000 psi) to 83 MPa (about 12,000 psi), and more preferably from 41 MPa (about 6,000 psi) to 69 MPa (about 10,000 psi) of the mold surface.

In FIG. 2, mold halves 20 and 30 are shown in a closed position, abutted or mated along parting line 42. As illustrated, mold cavity 40 is shown in cross section, although the design of the cavity can vary greatly in size and shape according to the end product to be molded. Mold cavity 40 generally has a first surface 44 on the first mold half, upon which a show surface of an article will be formed, and a corresponding back side or opposite second surface 46 on the second mold half. The mold cavity is modified to contain separate orifices to allow the substrate-forming composition and the IMC composition to be injected independently therein. The location of the injectors and injection orifices can vary from apparatus to apparatus, and from part to part, and can be based oη_ factors such as efficiency, functionality, workpiece geometry, etc.

As also shown in FIG. 1 , the first (substrate-forming) composition injector 50 is a typical injection molding apparatus which is any one of the types known in the art and is capable of injecting a thermoplastic or thermoset material, generally a molten resin, into the mold cavity. First injector 50 is shown in a "backed-off position, but the same can be moved to a horizontal direction so that nozzle or resin outlet 58 mates with mold half 20 and can inject into mold cavity 40. For purposes of illustration, first injector 50 is shown as a reciprocating- screw machine wherein a first composition is placed in hopper 52 and rotating screw 56 moves the composition through heated extruder barrel 54, wherein the material is heated above its melting point. As the heated material collects near the end of barrel 54, screw 56 acts as an injection ram and forces the material through nozzle 58 and into mold cavity 40. Nozzle 58 generally has a non-return valve at the nozzle or screw tip to prevent the back flow of material into screw 56. In some instances because of the size and/or complexity of the part being formed, extrudate may be injected into the mold from more than one location. To control the flow of the extrudate through a manifold, it may be necessary to heat the extrudate. These manifold passages may be referred to as hot runners or manifold systems and are shown in detail in FIG 16. In operation, a predetermined quantity of a substrate-forming material is injected into mold cavity 40 from first injector 50, forming a substrate or work- piece. Substrate formed in the mold cavity has at least a show surface 82 and an opposite surface 84.

Suitable thermoplastic substrates include but are not limited to nylon, polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), acrylic, polystyrene, polycarbonate, acetal, polyolefins such as polyethylene and polyethylene, polypropylene, and polyvinyl chloride (PVC). This list is not exhaustive, only illustrative.

The present method modifies an existing mold to allow a second, IMC composition to be introduced into mold cavity 40 from a second injector 60. Injection of IMC composition begins after the substrate-forming. material has. developed sufficient modulus to receive a coating or when the mold cavity pressure or temperature is within a desired range. These conditions are described in more detail below. In FIG. 2, second injector 60 is connected to a second nozzle 62 which is located in the mold half not containing the first injector 50. More specifically, first composition injection 50 is shown as located in fixed mold half 20 and second composition injector 60 is located in movable mold half 30. However, the position or number of second nozzle 62 is based on the portion of the workpiece to be coated. As shown in FIG. 2, the IMC composition 90 is injected through second nozzle 62 into mold cavity 40. The mold is not opened or undamped before the IMC is applied. That is, the mold halves maintain a parting line and remain in a closed position during the injection of both compositions. IMC composition 90 spreads out and coats a predetermined portion or area of show surface 82.

FIG. 16 depicts a hypothetical first or stationary mold half of the general design shown in FIG. 1. The drawing depicts a typical runner system inside the mold used for the delivery of the substrate-forming material into the mold cavity and is illustrative of two types of gates, namely hot tip as indicated by 160 and valve gate system as indicated by 170. In FIG. 16, 100 is a mold half. The polymer being fabricated is delivered from the injection unit through the bushing 112. Cavity plate 110 is the portion of the mold adjacent the part to be formed. A nozzle tip insulator, the function of which is to prevent the cavity plate from acting as a heat sink, is indicated by 114. Nozzle heater 115 is also part of the system to maintain the correct temperature of the molten material being injected.

The manifold heater 118 functions to keep the manifold hot. Sprue insulator 120 functions as part of the temperature maintenance system. Nozzle tip 122 is the actual point of delivery into the mold of the molten material and is located in nozzle housing 124. Lines through which water or oil are circulated to heat or cool, as is required by the polymer being used, are indicated by 126 and 128. Manifold heater 130, nozzle insulator 132 and air gap 134 all are part of the temperature maintenance system. Locating ring 136 is used to locate the mold relative to the injection nozzle. Sprue heater 138 is located on sprue bushing 142. The manifold 140 generally is the basis or foundation for the whole molding system. Valve gate 144 is part of the delivery system for nozzle tip 122 and is actuated by air open conduit 150 and air close conduit 148. Pressure transducer 180 measures the pressure in the mold; more than one such transducer generally is used. A temperature transducer 182 is used to determine the temperature in the mold; more than one such transducer generally is used.

Injection of the material used to form the substrate can be viewed as a three-stage process. The first stage is usually referred to as injection high. The optimum pressure used to inject the material from the injection machine into the mold can be determined by experimentation, but it preferably is sufficiently great so that the mold is filled to at least about 85 to 95% of its capacity. The pressure time, plastic mold size, and configuration are all determining factors. Generally, the pressure is increased until flash is noticed at the parting line of the mold, at which point pressure is slightly decreased.

The second stage of injection is referred to as injection pack. It too can be determined by a series of experiments and preferably is of a magnitude such that, at its completion, the mold cavity is filled to at least 99% of its capacity.

After injection pack, injection pressure is reduced to keep the workpiece from distorting. This begins the third stage, referred to as injection hold. As with the others, it can be determined by experimentation.

In modifying a mold, determining the ultimate machine conditions of the system in connection with a specific mold, a specific substrate material and a specific IMC composition can be important. In setting up the modified mold, a large number of variables must be interrelated to produce acceptable parts in a commercially acceptable amount of time. Pressures, times and other settings of the injection machine vary with the shape of the part being manufactured and/or the polymeric material being used.

To optimize these and the other critical operating parameters of the injection process, a series of experiments can be run with the mold and a specific substrate-forming material. The volume of any given mold may be calculated. Based on this calculation and the density of the substrate-forming material, the size of the charge can be determined. Differing machine variables can be tried until an optimum, complete filling of the mold in a minimum time, is determined. Preferably in these experiments, the mold is fitted with transducers/sensors which measure pressure and/or temperature while various machine variables (e.g., injection speeds and pressures) are altered. It is also possible to perform flow modeling based on the mold to optimize the operating parameters.

Variations in the amount of resin injected are tolerable in an amount of 0.5% of the total weight of the charge. Such variations occur in part because the resin is compressible and acceptable parts are produced within this range. Determination of the optimum operating variables in the injection molding of a new part basically is an iterative (i.e., trial-and-error) technique. While an experienced technician may have some idea as to what is required, he nonetheless will generate a certain amount of scrap with any new configuration. Choices are made for certain variables such as, e.g., barrel temperature, mold temperature, injection high pressure limit, injection hold pressure, injection speed, fill time, and holding time. Extreme adjustments are made in an effort to bracket operable conditions which then may be fine tuned, and this is referred to herein as a bracketing procedure.

To exemplify this process, a series of experiments were run using a modified 771 Mg (850 ton) CINCINNATI MILACRON™ hydraulic clamp injection molding machine and a modified mold to determine the optimum machine settings in respect of a number of substrate materials. The machine settings found to yield optimum results are set out in Table I below. These settings were arrived at using a bracketing procedure. The mold used in this procedure resembles a valve cover for an automobile engine essentially having the shape of an open box with turned down sides.

These results might not necessarily be applicable to another molding machine. Rather, a new series of tests might be necessary based on the system to be modified. This is also true in the case of a different mold or resin. In such a case, similar tests would need to be run to find optimum operating parameters. The examples used the following resins as the substrate-forming material: Example 1 : IMPET™ EKX215 glass-filled polyester (Ticona) Example 2: IMPET™ EKX230 glass-filled polyester (Ticona) Example 3: FORTRON™ 4184L6 polyphenylene sulfide (Ticona)

Example 4: a PC/PBT alloy (GE Plastics; Pittsfield, Massachusetts) Example 5: a polystyrene (Nova Chemicals Corp.; Calgary, Alberta).

Table I (cont.)

n/a = not applicable

Having determined the operating parameters for production of the substrate, one must then determine, by reference to appropriate tables or by measurement, the melt temperature of the substrate-forming material so that the IMC composition may be injected at the proper time. By use of transducers or sensors referred to above with respect to FIG. 16, it is possible to determine when the temperature of the substrate has cooled below the melt temperature of its constituent material(s). Alternatively, the melt temperature can be determined indirectly by observing pressure. When a molded part reaches its melt temperature, it starts to contract somewhat, thus reducing the pressure. If transducers are not used, the time when the melt temperature is reached and injection of IMC composition commences can be determined and then used to control the operation. In other words, the length of time between the mold closing and the substrate reaching its melt temperature can be determined and used to control the start of injection of IMC composition. A series of experiments using a modified machine and IMPET™ 430 resin and STYLECOAT™ X primer (OMNOVA Solutions Inc.; Fairlawn, Ohio) as the IMC composition were run. By temperature measurements, the substrate resin was determined to have cooled sufficiently below its melt point 50 seconds after the mold had closed. Three parts were run using a 90-second cure time for the IMC. These parts showed good coverage and curing.

A further 33 parts were run to confirm these machine settings and all of the parts were acceptable, i.e., good appearance and adhesion. A further sample was run injecting the IMC only 30 seconds after the mold closed and using a cure time of only 60 seconds. This part was unacceptable because some portions were only lightly coated. This confirmed the correctness of previous machine settings.

Another series of parts were made using VANDAR™ 9114 PBT-polyester alloy as a substrate resin. The substrate resin had cooled below its melt temperature 30 seconds after the mold closed. These parts all demonstrated good appearance, i.e., even coverage and good adhesion.

To illustrate more clearly the necessity of injecting the IMC composition at the proper time (i.e., immediately after the surface of the substrate resin cools to its melt temperature) contrasted with an injection that occurs too early or too late, a series of experiments was run on a modified TOSHIBA™ 950 injection molding machine using a hydraulic clamp, VANDAR™ 700 resin, and STYLECOAT™ primer as IMC composition. The machine settings were determined as described above and were identical except for the time at which the IMC composition was injected, i.e. the Interval in seconds between the closing of the mold and the commencement of the injection of the IMC. The results of these experiments are set forth in Table II below.

TABLE II

The above examples clearly demonstrate the desirability of determining and setting the system so that the IMC composition is injected at the time when the surface temperature of the substrate just falls below its melt temperature. Therefore, the present method can include determining and setting the operating parameters including optimal time to inject the IMC composition.

As stated above, a substrate can be selectively coated in predetermined - areas. In addition, the selective coating can be further controlled by modifying the molds to control or modify the thickness or depth of the substrate. In this respect, the thickness or depth is defined as a distance, girth, or dimension from one surface to the opposite surface of the substrate. The modification to the mold for increasing the IMC composition flow is generally concerned with the depth between two surfaces, the first being a surface to which an IMC composition is selectively directed or applied, commonly referred to as a show or appearance surface, and the back surface that is substantially opposite. The IMC may but does not necessarily cover the entire show surface. For example in FIG. 3 thickness refers to the distance from show surface 82 to the backside or opposite surface 84. As shown in FIG. 3, the thickness between the show surface and back side of the substrate can vary. Each substrate inherently has a compressibility factor or percentage, i.e., at a given temperature, a given substrate is compressible to a specific, calculable percentage. Therefore, even though a molded article or substrate has a single compressibility ratio, a first area of a substrate which is thicker than a second area can compress a greater thickness or distance. For example, a given substrate might have a compressibility ratio of 20% at a certain temperature. Therefore, a portion of that substrate which has a thickness of 2.0 cm can compress 0.4 cm whereas another portion which has a thickness of 1.0 cm can only compress 0.2 cm at the same temperature. This compressibility can be utilized to selectively coat predetermined areas of a substrate by modifying the mold accordingly. Substrate compressibility can also be utilized to effectively direct the flow of an IMC into certain areas or pathways of a substrate.

As stated above, IMCs can be applied to a substrate in numerous, well known ways. Referring to FIG. 2, shown is an IMC (or second) composition injector 60 having a nozzle 62 on the molding apparatus in a suitable location such as on mold half 30. A first quantity of the first composition is injected into a mold cavity to a desired predetermined level, forming a substrate, work piece, or article, such as plaque 100 shown in the views of FIGS. 3-5. As shown in FIG. 3, the substrate has at least a show surface 82 and back side 84. An IMC composition 90 is then injected into the mold cavity, from injector 60 through at least one nozzle 62 onto the show surface side of the substrate at a location such as 104 on tab 103 as shown in FIG. 4.

The mold is not opened or undamped before and/or during injection and curing of the IMC composition, that is, the mold halves maintain a parting line and generally remain a substantially fixed distance from each other while both the first and second compositions are injected into the mold cavity.

The liquid IMC composition disperses or radiates onto show surface 82 from the point of injection 104, the location of which depends on where the IMC composition injector and nozzle thereof is positioned in the modified molding apparatus. Accordingly, the point where the IMC composition is injected can be substantially anywhere on show surface 82 and is not limited to the locations shown in the drawings. The IMC composition cures on the substrate so as to form a coating. The cure is optionally heat activated from sources including, but not limited to, the molded substrate, the mold itself, or by temperature controlled water flowing through the mold. Modification of the mold can include directing or channeling the flow of an

IMC composition on the substrate. As stated above, through the control of variables of the molding process, an amount of material that will produce a desired substrate can be determined experimentally or by flow modeling. After the first composition has been injected into the mold cavity and has cooled below the melt point or otherwise reached a temperature sufficient to accept or support an IMC, a predetermined amount of IMC composition is injected from injector 60 onto an injection point of the substrate, preferably on a show surface thereof. The coating composition is injected at a pressure that ranges generally from about 3.5 to about 35 MPa (500 to 5000 psi) and typically from about 7 to about 30 MPa (1000 to 4500 psi) so as to promote the spread of the IMC composition away from the nozzle between a mold surface and a surface of the substrate. Flow of the IMC is controlled by modifying the mold to vary the thickness or depth of the resin of the substrate below the surface to be coated which directs the IMC to preferred areas of the substrate. For example, if a mold cavity is designed so that a substrate has a constant thickness under an area to be coated, the IMC composition will spread from the location of injection in a substantially radial, even, constant manner. Under the same relative conditions, if a substrate is formed having areas which vary in thickness under the surface area to be coated, the IMC composition can be channeled to flow in area(s) of greater relative thickness. Thus, the depth of the coating also can vary on the coated surface. The compressibility of the substrate allows a substrate area having a greater depth relation to a second area to compress more and better accommodate IMC flow and promote migration thereof. Substrate temperature also is a factor in compressibility and, therefore, a factor affecting flow. In another potential modification to the mold, a substrate is provided with an area of increased thickness around the point where the IMC composition is injected onto the substrate. By increased thickness is meant that the thickness of the substrate around the IMC composition injection location is greater than the thickness of at least one other area or section of the substrate. As shown in FIG. 5, plaque 100 is shown with a tab area 103 at a location of IMC injection. The thickness of tab area 103 can be varied to enhance channeling of the IMC composition. Tab section 104 in FIG. 4 includes a thin section or containment tab flange 102 which prevents the IMC composition from flowing out of the mold cavity. The containment flange will be further discussed below. The relatively thick tab area promotes coating composition flow from the IMC nozzle onto show surface 82 of the substrate as the IMC composition tends to avoid substrate sections of minimal or lesser thickness such as the tab. In yet a further modification to the mold, a substrate is provided with at least one "runner" section, preferential flow channel, or area to promote IMC flow on a substrate. A runner is an area which is relatively thicker than another area adjacent thereto, wherein the IMC composition can be routed to flow preferentially. Advantageously, runner sections can be provided on substrates of complex design or otherwise difficult to coat. A runner section generally is located in an area on the substrate beginning in the region of the point of injection of the IMC composition and extending away therefrom to a predetermined point or terminus on the substrate. For example, FIG. 5 has a runner section 106 extending from and including tab area 103 to substantially the bottom end 107 of the plaque; FIG. 6 shows a door panel having three runner sections 109. Depending on the amount of IMC composition injected into a mold cavity, the show surface having a runner section can be completely coated or coated only in certain areas such as the runner sections. The amount of coating applied and thickness thereof can vary from part to part. The depth of the runner section can vary depending on the substrate to be coated and design specifications. A substrate can have a runner section extending from an area of IMC composition injection which is so relatively thick that all of the IMC application to the substrate surface remains substantially in the runner section. Therefore, as can be imagined, many unique effects can be created by modifying the molding system to utilize runner sections. For example, a runner section can be utilized to channel coating composition to a distal part of a substrate surface. The runner section thickness can be gradually decreased in a direction away from the point of injection as needed, or even separated or divided into more than one runner section, to accomplish a desired coating effect.

In yet a further modification to the mold, a molded substrate or article is provided with a containment flange 98. As shown in at least FIG. 4, containment flange 98 can extend completely around the perimeter of a substrate, specifically plaque 100. Flange 98 can be used as a barrier to prevent the IMC composition from leaking out of the mold cavity and potentially blowing out of the parting line. As shown in at least FIG. 3, flange 98 is generally offset or formed in a plane below that of show surface 82. Thus, show surface 82 has an edge or border 83 which transitions into flange 98. Show surface edge 83 drops off into a wall at an angle of about 90° relative to the show surface. Substrate wall 86 terminates at flange portion 98, wherein flange portion extends at an angle of about 90° in relation to wall 86. The relatively sharp angles between show surface 82 and flange 98 as well as the relative incompressibility of the thin flange act are believed to act as a substantial barrier to flow of coating composition. Flange 98 generally has a thickness less than the thinnest portion or area of the substrate. As shown in FIG. 3, flange 98 is thinner than section 96, the relatively thinnest section of the substrate. Flange 98 encompasses substantially the entire perimeter of a substrate surface to be coated and generally has a width of about 0.57 to about 0.45 cm (0.225 to 0.176 in.), desirably about 0.44 to about 0.19 cm (0.175 to about 0.076 in.), and preferably about 0.19 to about 0.11 cm (0.075 to _. about 0.045 in.).

As shown in FIG. 7, IMC 90 covers the entire show surface of the molded substrate. Due to the configuration of the molded substrate as well as other molding variables, coating 90 does not cover flange 98, although it can. Due to the design of flange 98, generally less than about 10%, desirably less than 5%, and preferably less than 1% by weight of the IMC covers flange 98. Flange 98 is free of any other substrate material on the distal edge thereof. There is no other substrate material or outer edge between the flange and the parting line. The mold can also be modified to include a breakable, removable flash edge or containment flange. Molded articles, parts, or substrates most often are constructed to conform to certain predetermined, definite tolerances. Frequently, the articles are designed to fit exactly or substantially exactly into an assembly or working arrangement of parts. Articles provided with an additional containment flange to contain a coating often are larger than specified manufacturing tolerances. Furthermore, often the containment flange show surface is not coated with an IMC, leaving the article with an undesirable appearance. Keeping a liquid, uncured IMC composition confined to an intended substrate target surface area is extremely difficult. Frequently, the composition flows or leaks onto surrounding mold surfaces, such as around the parting line; non-show surfaces of the article which are not to be coated; and even out of the mold itself. Another problem associated with coating leakage is that the coating composition may not become properly packed in the mold resulting in coated parts having dull appearances, parts not having an even film build or adequate coating thickness, or parts not exhibiting the desired or required texture. Coating seepage onto ejector pins can cause binding and unworkability of the molding apparatus. Such overflow is unacceptable as parts can be ruined, and mold surfaces must be cleaned to remove coating buildup.

A mold modified according to the present method prevents the aforementioned problems by making changes to the mold so that the molded article or workpiece has an IMC containment flange or flash edge which is flexible and thus easily removable, e.g., by hand after the article has been coated and the coating cured. The coated article with the removable containment edge removed can be used as-is in an assembly. One advantage of the removable containment flange, which may only be partly coated and possibly unsightly, is that it can be easily removed and discarded. Moreover, a fully coated part of desired dimensions and exact standards can be produced. Labor and monetary savings are other advantages as coating containment is achieved, and waste is minimized. The removable containment flange potentially eliminates part painting operations, secondary handling, and shipping costs between a part molder and a painter.

Referring to FIG. 11- 15B, molded articles or substrates having removable flexible containment flanges are shown. Shown in FIG. 11 is an article 200. The main or show surface 210 is coated. Due to the presence of the removable containment flange 220, the IMC composition is prevented from leaving the surface of the substrate and contaminating other mold surfaces or the back side of the molded article.

FIG. 11 also illustrates substrate injection area 230 wherein the substrate-forming material was injected into the mold. IMC composition injection area 240 shows the ingress point of the IMC composition which has spread across the show surface therefrom. Removable flange 220 extends completely around the periphery of the show surface to inhibit flow off of the main surface, excepting the area around the injection area 240 which already includes a feature for containment. Removable flange 220 is shown as extending around the entire periphery of the show surface, although it could extend around only a portion if the workpiece includes flow restricting geometry. FIG. 14 shows a removable flange 220 extending completely around the periphery of the main surface of a substrate 200. IMC composition injection inlet area 240 is also shown. Again, the removable flange can extend less than the complete distance around the perimeter of the substrate main portion if some other containment feature is present or substantially no leakage occurs in the specific area.

The removable flange is located or formed on a substrate surface in an area or plane between the show surface edge or perimeter and a backside edge or perimeter of the part. No matter which flange is utilized, each flange has a width and a depth or height. As shown in FIG. 12, the width A can be defined as the greatest distance the flange extends outward or away from the substrate main body C at a location between a show surface D to be coated and the non- show surface E opposite therefrom. Depth B can be considered a depth or thickness measurement, which can vary along the width of the flange, with the greatest depth generally existing at the outermost portion of the flange. The flange is designed to have a very thin section located adjacent to, or in the vicinity of, the substrate which is readily breakable. Removing the flange is as simple as, for example, flexing it back and forth to break the leading edge thereof away from the edge of the part main surface. Although not necessary, the flange also can be removed with tools such as a cutting edge, hot edge tools, water jet, buffer, sander, router, and the like.

The removable flange can have numerous configurations. FIG. 12 shows a cross section through FIG. 11 wherein the flange 220 is formed as a wedge having a depth greater at its outer end portion than where the same contacts and removably connects to the substrate main body. The removable containment flange can be formed only on one side of the parting line 205. The angle between the vertical side surface of the substrate main body and the containment flange top surface can vary from about 10 to about 90° and is preferably from about 15 to about 30°. FIG. 13A shows a cross section of a coated substrate 220 with IMC 216 on substrate 215 and triangular flange 221. A rectangular flange 222 is shown in the configuration of FIG. 13B. Circular and semicircular flanges can also be utilized as shown in FIGS. 13C and 13D respectively. The flange can be almost any geometric shape or design such as an ellipse, teardrop, or taper, etc.

For the flange be easily removable, its point of attachment to the substrate main portion should be sufficiently thin to be easily separated or broken away from the substrate. The thickness of the flange is dependent on the substrate-forming composition. Accordingly, the thickness of the flange at the point of attachment immediately adjacent to the substrate is less than about 0.7, 0.6 or 0.5 mm, and preferably is from about 0.1 to about 0.4 mm. The thickness of the flange in a direction away from the point of attachment to the substrate main portion can increase to any desirable thickness, which is generally greater than the thickness at the point of attachment. The width of the flange from the substrate main portion to the peripheral edge thereof is generally less than about 10 mm, desirably from about 2.5 to about 8 mm, and preferably from about 3 to about 6 mm.

The mold can be modified so that the removable containment flange is formed into either or both of the mold halves described above as by machining, milling operation, or the like as known in the art. Typically, the flange is formed along one or both sides of parting line 205 as shown in at least FIG. 12. Due to the design of the containment flange and the substantial incompressibility of the containment flange at the thin or narrow point of attachment to the substrate main portion, the IMC composition predominately stops at the attachment point between the substrate main body and containment flange as shown in FIGS. 13A-13D. That is, a compression gradient is formed and the IMC is able to flow across the relatively thick, compressible substrate main portion but cannot substantially flow across the relatively thin incompressible containment flange edge attached to the substrate main portion.

The mold can be further modified so that the removable containment flange extends onto a surface of a substrate to prevent flow of IMC composition onto predetermined areas of the show or other surface. FIG. 15A illustrates a substrate 300 having a removable containment flange 320 extending across a portion of show surface D as well as around a portion of the perimeter of the substrate to contain IMC 316 to a predetermined area of show surface D.

FIG. 15B is a cross sectional view through 15B-15B of FIG. 15A. This view shows that IMC 316 is contained in a predetermined portion of show surface D by removable containment flange 320.

Accordingly, the removable IMC containment flange can be utilized in any area(s) or location(s) on any surface of a substrate to preferentially coat predetermined portions thereof. Crisply defined coating boundaries or areas on a substrate can be created when a removable containment flange is utilized on a substrate, especially a show surface thereof. Many different surface aesthetic effects can be created utilizing containment flanges, especially removable ones. Obviously, the modification to the mold can include any number of containment flanges. The containment flange can be utilized to create any type of pattern, design, logo, lettering, insignia, etc. Different colored coatings can be incorporated on different areas of a substrate which have containment flange boundaries, thus allowing for shading, contrasting colors, special effects, etc. Removable containment flanges also can be used on a substrate at an edge opening adjacent to a moveable mold section such as a slide or core which are known in the art. The removable flange will prevent or block IMC composition from leaking into the moveable core area and possibly binding the same.

Referring to Figs. 17A-18C, shown is yet another mold modification. In this respect, IMC composition can be injected on a center portion of a substrate surface at 310 of substrate 325 as shown in FIG. 17 A, or a corner of a substrate surface at 410 of substrate 400 as shown in FIG. 18A. Typically, the IMC composition is injected at a location on a molded substrate that is inconspicuous when the article is used. Alternatively, the IMC composition can be injected onto a portion of the substrate that later can be removed or cut away from the remainder of the substrate. For example, if desired, the IMC composition injection area at tab 103 of FIGS. 4 can be cut away where it connects to the main portion of the molded substrate, leaving a substantially square coated article.

As stated above, IMC composition flow can be promoted or enhanced by creating an area of increased relative thickness or a compressible zone on the substrate at the location of IMC injection. FIGS. 17A through 17C illustrate a molded substrate 325 including a compression differential to promote flow on a substrate. FIG. 17 A is a front view of substrate 325 wherein a containment flange 330 can be utilized to confine the IMC to the show surface 302 of the substrate. The IMC composition can be injected onto the injection inlet area 310 of the substrate during a molding cycle. Area of substrate injection 312 is also illustrated in phantom as the substrate has been injected from the back side 304 opposite of show surface 302 to hide any flow lines or undesirable edges which may be present after a sprue is removed.

The area of increased thickness 308 forms a "flow zone" which is selectively used to control the flow of the coating composition and thus the thickness and surface area of the resultant coating. For example, for an area of increased relative thickness that has a corresponding increased compressibility, the flow zone promotes flow of the IMC composition to the contiguous surface of the substrate for the area adjacent thereto which has a relatively thinner cross section. This flow zone is also adjacent the injection site for the coating and is distinct from other complex cross sections having increased thickness as may occur from reinforcing struts or similar structural details insofar as the flow zone is designed for selectively controlling the flow of the coating by providing a channel of increased (or decreased) compressibility. It is to be understood, however, that these areas of increased (or decreased) thickness may also serve as flow zones. Likewise, the flow zone may comprise an area of decreased compressibility such as occurs for a thinner cross section area like a peripheral flange. In this case, the flow zone acts as containment zone for the coating. Further, in this case, the flow zone does not need to be adjacent to, and in fact probably will be remote from, the injection site. FIG. 17B shows a cross-sectional side view through 17B-17B of the molded substrate of FIG. 17A. Show surface 302 and back surface 304 have a variable distance or thickness therebetween. Sprue 314 is formed during the substrate injection molding step. The area behind injection inlet area 310 is provided with area 308 that has a greater thickness than substrate regions 306 to promote IMC composition flow. Area 308 has a thicker section or greatest depth at its central portion where the IMC composition is injected onto show surface 302. The thickness of the substrate tapers from injection inlet area 310 and reaches a relatively constant depth in substrate section 306. The relative depth or thickness provided by area 308 provides a readily compressible area for the IMC composition and promotes flow to other desired areas of show surface 302. As shown in FIG. 17C, the IMC 320 completely covers show surface 302. Alternatively, if desired, substrate 325 can contain other compression differential zones such as a mold runner described above and can be coated in pre-selected areas utilizing substrate compressibility.

Referring to FIGS. 18A-18C, another use of substrate compressibility to create a compression differential which promotes IMC composition flow at an injection inlet area is shown. FIG. 18A shows molded substrate 400 with show surface 402 and containment flange 430. The IMC composition is injected at inlet area 410. Substrate-forming material is injected at a location behind area 412. FIG. 18B is a partial cross section of plaque 400 situated in a mold cavity 440 between mold halves 442 and 444. The molded substrate has been coated with IMC composition 420 from injection device 422 through inlet channel 424 via a nozzle at inlet area 410. The mold parting line 460 is also illustrated. The IMC composition is injected onto the substrate at area 408 which has an increased thickness when compared to other portions of the substrate including area 406. The IMC composition can more easily compress the substrate in area 408 as compared to area 406 due to the increased thickness thereof. FIG. 18C illustrates the front view of show surface 401 of coated substrate 400. The substrate has a thickness ratio at the location of IMC injection (such as 310 in FIG. 17A) when compared to another portion of the substrate intended to be coated of from about 1.1 :1 to about 10:1, desirably from about 1.25:1 to about 2:1 , and preferably from about 1.3:1 to about 1.5:1. To promote smooth, even flow of IMC composition across the show surface, a smooth or substantially constant transition is made from the location of IMC composition injection to the other substrate areas as shown in FIGS. 17B and 18B. The transition zone can be considered as a taper or ramp. Of course, as stated herein other features such as runner sections and coating containment flanges also can be incorporated to control or promote IMC composition flow. In addition, controlling the substrate and/or mold temperatures can affect this flow. Referring to FIGS. 19-25, shown is a mold runner 22. Referring to FIG. 20, first composition injector 50 is shown contacting mold half 20 so that nozzle or resin outlet 58 mates with mold half 20 and can inject into mold cavity 40 through mold runner 22. Mold runner 22 provides a passageway in the mold half for transferring a substrate composition from injector 50 into mold cavity 40. The mold runner may also be referred to as a sprue bushing, mold runner drop, etc. FIG. 22 shows a schematic view of one type of mold runner 22 which has a body member that can be separate from or integral with a mold half 20 or platen 21 , i.e., the mold runner can be a separate, removable, and distinct member inserted in and attached to a mold half or can be formed or shaped into a mold half itself. Mold runner 22 has a first and second ends, 23 and 25, and extends therebetween. First end 23 receives melted material from the injection molding machine and second end 25 discharges the material into the mold cavity 40, with the material subsequently forming a substrate in the mold cavity which can be coated. Mold runner 22, except in the region of the containment shroud, is cylindrical in cross section to avoid placing stress, strain, and shear forces on the substrate during injection; other suitable shapes, include but are not limited to, conical, helical, and tapered, etc. As shown in at least FIG. 20, the nozzle 58 is positioned or seated at first end 23 for a molding operation. Mold runner 22 includes containment shroud 27 which prevents IMC composition from flowing or terminates such flow through passageway 26 and into the molding apparatus 50. The containment shroud is generally a recess or void which extends around the entire perimeter or circumference of at least one portion of the mold runner passageway between the first and second ends. In other words, the containment shroud is generally a cavity, formed in the mold runner about a peripheral segment of the passageway generally on a plane substantially perpendicular to the passageway axis. Each containment shroud has a base portion and a terminal or end portion as at least shown in FIG. 22(a) as 28 and 29 respectively. The base portion 28 has a predetermined width along an axial length of the passageway. The containment shroud also has a height and extends for a distance generally radially outward from the passageway perimeter.

As noted above, the containment shroud has a design or structure effective to prevent or terminate an IMC composition from passing therearound or therethrough from the passageway egress to the passageway substrate- forming material entrance. After the substrate-forming composition has been injected into the mold cavity, the mold runner and containment shroud are also filled therewith. The filled shroud utilizes the relative incompressibility of the substrate in this thin area as a barrier to prevent IMC composition flow.

In another example of a runner, the base portion has a width or thickness greater than or equal to the terminal portion, such as shown in FIGS. 23 and 24, to allow substantially easy removal of the partially coated substrate sprue including a projection formed in the containment shroud. The width of the base portion can vary but generally ranges from about 0.025 to about 6.4 mm and preferably from about 0.06 to about 0.4 mm. Accordingly, the terminal or radially outward portions of the containment shroud often have a width less than the base portion. The height of the containment shroud between the base portion and the terminal portion can vary but is generally from about 0.1 to about 2 mm, desirably from about 0.2 to about 0.65 mm, and preferably from about 0.25 to about 0.4 mm. The containment shroud can be located anywhere along the mold runner passageway between first and second ends 23 and 25, respectively. Preferably the containment shroud is located toward the second end where the IMC composition can enter the mold runner. The containment shroud can be located as close as about 0.25 mm to the second end. The shroud design and location is dependant on numerous factors such as the diameter of the runner, the substrate composition and the need to remove the molded workpiece from the mold.

Yet another example is shown in FIG. 22 wherein the containment shroud 27A is shown as an annular ring having a plane perpendicular to the axis formed by the passageway between first and second ends 23 and 25, respectively. The annular ring has squared-off corners at the end portion thereof. FIG. 23 shows containment shroud 27B which is set at an angle so that the sprue formed by the substrate which fills the passageway and containment shroud can be easily removed from the mold runner after a molding and coating operation is performed and the coated part is removed from the mold. Containment shroud 27B is generally set at an angle 0 measured from an axis formed by the passageway and height measured from the base portion to the terminal portion. The angle 0 may vary from about 1° to about 90°, desirably from about 25° to about 65°, and preferably from about 40° to about 55°.

The passageway in FIG. 23, between the containment shroud and second end 25, is also shown to have a diameter greater than that of the passageway between the containment shroud and first end 23. This configuration makes the sprue easier to remove. Thus, when the sprue is pulled out of the mold in the direction of the mold cavity, the containment shroud is flexible or bendable and conforms to the diametrical space provided in the passageway nearest the second end. The containment shroud can also have a taper or wedge 27C as shown in FIG. 24. The containment shroud is not meant to be limited to the ones specifically illustrated in the drawings and one of ordinary skill in the art would understand that modifications and variations are possible.

FIG. 25 illustrates a cross section through a vertical axis of a mold half at a location where the containment shroud is present such as in FIG. 22. As can be seen therein, containment shroud 27 extends completely around the perimeter of passageway 26 to prevent IMC composition from flowing through the mold runner. The mold runner in this example is of a cylindrical shape and therefore the containment shroud extends radially around the passageway perimeter.

To understand how the mold runner functions, the following description of an coating process is described, with reference made to FIGS 19-25, a substrate-forming material is introduced into an injection molding apparatus wherein the material is heated above its melting point. The substrate-forming material is moved through the apparatus utilizing rotating screw 56 and deposited at the end of the barrel. During a molding cycle, the mold halves 20 and 30 are brought together in a closed position as shown in FIG. 19 and the molten substrate-forming material is injected from nozzle 58 of the injection molding apparatus through mold runner 22 into the mold cavity 40. Generally, an amount of substrate material is injected into the mold cavity so that a final product desirably fills the mold cavity. As shown in FIG. 19, the substrate- forming material takes the shape of the mold cavity and also includes a sprue portion 53 which resides in mold runner 22, generally conforming to the shape thereof and completely filling the same. Once the substrate-forming material has been injected, it begins to cool and solidify until it reaches a point where an IMC composition can be applied thereto. An IMC composition then is injected into mold cavity 40 onto a show surface of the substrate material. As shown in FIG. 20, injector 60 injects an IMC composition onto show surface 44. Through pressure, the IMC composition spreads from inlet 62 across show surface 44. Inasmuch as the IMC is injected onto the same side of the substrate material as sprue 53 and mold runner 22, the IMC composition will flow along sprue 53 toward the injection apparatus 50.

FIG. 21 illustrates a coated substrate in a mold cavity wherein a containment shroud has been utilized to prevent the IMC composition from flowing through a mold runner. The uncured IMC composition spreads out across the surface of the substrate and also enters second.end 25 of the mold runner 22. The coating composition travels up the sprue from the second end 25 toward the first end 23 of the mold runner due to the compressibility of the sprue material. Once the IMC composition encounters the containment shroud 27, it is prevented from any further spreading due to the relative incompressibility of the substrate composition in the containment shroud. Thus, the IMC composition is prevented from reaching first end 23 and entering injection apparatus 50 and contaminating the substrate-forming material therein.

After the IMC composition has been injected into the mold cavity, it cures and adheres to the substrate and forms a coating. Thereafter, the fixed mold halves are parted and the coated article removed along with sprue 53, which contains a rim or projection formed by the mold runner containment shroud. The sprue is easily removable from the mold runner as the projection formed in the containment shroud is generally flexible. Further coated articles can be produced because the IMC composition has not contaminated the injection apparatus. In addition, no deposits of the IMC composition remain in the runner system. FIGS 26-29 show yet another mold modification to control IMC flow. In this respect, substrate 740 includes barrier 743 that includes a barrier rim of substrate material 742, a substrate injection inlet area 744 and an IMC composition injection area 746. A containment flange 748 as described above is also shown. Again, while flange 748 is shown to completely surround the area of the substrate which has been coated with coating 741 , the flange may only partially surround the area to be coated based on the configuration of the workpiece and the flow characteristics of the mold. Furthermore, the substrate injection inlet area 744 is free of the IMC due to the presence of barrier 743.

As shown in FIG. 27, barrier rim 742 extends around the perimeter of substrate injection inlet area 744. Barrier rim 742 contains a protrusion which is raised or elevated when compared to the surface of the substrate adjacent thereto, outside of the barrier rim perimeter. Typical substrate injection orifices are generally round or cylindrical; accordingly, barrier rim 742 is also formed as a complementary shape around the orifice and can be an annulus, ring, etc., but generally can be any shape such as, e.g., square, triangular, etc.

The height of the barrier rim and other portions of the substrate can be measured from one side of the substrate to the other, such as from the show surface to the back or opposite surface, i.e., between the corresponding mold halves, as described above. The rim height or thickness refers to a maximum height unless specifically stated. The elevation or height of the barrier rim can also be measured from the show surface to the distal end of the rim. The character Y in FIG. 28B illustrates the height of the barrier rim 742 which is substantially the same throughout its width which is designated Z. The barrier rim height Y in conjunction with width Z is designed to substantially prevent IMC composition 741 from flowing into the substrate injection inlet area 744 as shown in at least FIG. 28C. After the IMC composition is injected onto substrate 740 surface at injection inlet area 746 in FIG. 27, the coating spreads across the surface between a mold cavity surface and the substrate surface by compressing the substrate. Eventually, IMC composition 741 reaches the base of barrier rim 742 as shown in FIG. 28C and will attempt to flow up the height of the barrier rim 742 by compressing the width Z of the rim. Width Z is relatively thin and thus is sufficient to prevent IMC composition 741 from flowing into substrate injection inlet area 744 as shown in FIG. 28C at least because the rim width is relatively incompressible and forms an IMC seal or barrier to coating flow.

Width Z can be made sufficiently thin so that IMC composition does not flow onto the rim itself, much less the substrate injection inlet area. Accordingly, the ratio of the barrier rim width Z to the thickness X of the substrate (as shown in FIG. 30A) adjacent to the barrier (measured from the substrate front surface to the back surface) ranges generally from about 0.1 :1 to about 2:1 , desirably from about 0.25:1 to about 1 :1 , and preferably from about 0.3:1 to about 0.8:1. The required compression differential can vary depending on substrate composition, mold temperature, and workpiece design, etc., and can be readily determined through limited experimentation.

The differences in the height ratio between the barrier rim height Y (742 in FIG. 27) and the substrate thickness X are also sufficient to prevent IMC composition from breaching the substrate injection area or orifice, and ranges generally from about 0.1 :1 to about 5:1 , desirably from about 0.5:1 to about 2:1 , and is preferably about 1 :1.

FIGS. 28A-C illustrate a process for forming the substrate injection orifice barrier and show a cross-sectional view through a portion of a mold assembly similar to the apparatus shown in at least FIG. 1 and described above. FIG. 28A shows a partial view of a mold cavity 40 interposed between first and second mold halves 710 and 712 respectively. In FIG. 28A, the mold cavity is also shown having barrier forming relief 721 including rim 722. A substrate-forming material is injected into mold cavity 40 at substrate injection inlet area 724 when gate pin 720 is backed away from the entrance as shown in FIG. 28B. As described above, the gate pin is merely one example of a substrate inlet control. During a typical molding cycle, gate pin 720 is backed away from inlet 724 as shown in FIG. 28B, allowing a substrate-forming material 740 to flow into mold cavity 40 to a predetermined level. Barrier 743 including barrier rim 742 is also formed with the substrate material. After a sufficient amount of the substrate material has been injected, gate pin 720 is moved into a closed position as shown in FIG. 28C to stop the flow of substrate-forming material and for cosmetic purposes to leave a clean shut-off on the surface of the molded article.

After the substrate has cooled, achieves a suitable modulus, or otherwise is capable of accepting a liquid on its surface, the coating composition is injected into the mold cavity. Upon injection, IMC composition 741 flows across the surface of the substrate until it encounters barrier 743. Upon reaching barrier rim 742, the IMC composition compresses the rim width against the mold cavity and ceases to flow into the substrate inlet area or substrate injection orifice at least because the relative compressibility of the substrate barrier rim width along the height thereof. Thus, as shown in FIG. 28C, IMC composition 741 is prevented from reaching or flowing to gate pin 720 and passing between it and surrounding clearances.

FIG. 29 illustrates a barrier for a substrate injection apparatus without a gate pin. Accordingly, modifying the mold as described above provides a barrier for substrate injection orifices even though a gate pin might not be utilized. IMC composition cannot access the substrate injection inlet area due to the presence of the barrier.

As stated above, barrier rim 742 may have both varying heights and or widths and thus may have many different shapes or designs other than the barrier rim shown in FIGS. 28B, 28C, and 29 which has two substantially equal height walls formed at substantially perpendicular 90° angle to the substrate main surface and a substantially constant width. FIG. 30A illustrates an alternative barrier design having tapered rim 742 with varying height Y and width Z. The main portion of substrate 740 has a thickness or depth X. Rim 742 has one wall substantially perpendicular to the substrate main surface and a slanted wall at about a 45° angle. The upper, thinnest portion of the rim is substantially incompressible, and thus the IMC composition substantially cannot flow into substrate injection inlet area 744. FIGS. 30B-C illustrate other possible variations for barrier rim design, showing a different tapered rim and a partially rounded rim. Design of the barrier rim is limited only by mold cavity constraints wherein it is desirable to allow the substrate with barrier to be easily removed from the mold cavity after molding and coating.

Referring to FIG. 9., a mold for producing a plaque 200 is shown which has been modified for accepting an IMC composition is shown. The mold cavity width is 30.5 cm, and its length is 52 cm. The mold has a hydraulic mold gate located in the center of the cavity for injection of a substrate and a tapered tab for the introduction of IMC composition onto the part surface. The tab is located at the edge portion of the mold. The thicknesses of tab and Section A are 0.003 mm, Section B is 0.0025 mm, Section C is 0.002 mm, and Section D is 0.0015 mm. The plaque has four panels in a horizontal plane on the left side of the part and four panels in a vertical plane on the right side of the part. The panels on the horizontal plane on the right side of the part measure 15 cm long and 13 cm wide. The panels on the vertical plane measure 3.8 cm wide and 52 cm long. The plaque does not have an IMC containment flange. The mold was placed in a modified 771 Mg (850 ton) CINCINNATI MILACRON™ VISTA™ injection molding machine. ABS resin heated to a temperature of 249°C was injected into the mold cavity thus producing the plaque shown in FIG. 9 having sections A-D with the above described dimensions and thicknesses. The front of the plaque had a smooth surface and, thus, the backside of the plaque shows the various thickness contour variations. After a delay or hold time of approximately 120 seconds, a STYLECOAT™ coating composition was injected through the tab portion of the plaque onto the front surface thereof. The chart below details how the coating composition flowed onto the different sections of the plaque.

It was determined, from the part surface area to be coated and the desired coating thickness, that an IMC amount of 1.97 cm³ would produce a full IMC shot and cover the entire plaque. As can be seen from the chart, upon IMC injection onto the plaque surface, the top left panel and the inside vertical panel (runner section A) were preferentially coated when 25% of a full shot was utilized. Thus, this example shows that Section A is an effective runner section whereby the coating prefers to flow down the plaque along Section A and out to the side thereof before flowing into thinner sections B, C, and D. When 50% of a full IMC shot was utilized, the IMC began to flow from Section A and B into Section C.

The plaque shown in FIG. 9 did not contain a containment flange. When coating levels above 50% of a full shot were utilized, the same leaked out of the mold cavity through the parting line. Thus, it was determined that a containment flange was needed to keep the IMC composition on the desired substrate surface.

Referring to FIG. 10, a thermoplastic article 300 with a variety of substrate thicknesses is shown. The example parts were generated using a 45 Mg (50 ton) injection molding machine and 15 cm square steel mold, both of which were modified as described above. The substrate-forming material was a PET thermoplastic and the IMC was STYLECOAT™ primer. The mold temperature was 121°C with a 30 second delay time prior to IMC composition injection.

Sections E (0.29 cm thick), F (0.22 cm thick), and G (0.15 cm thick) are representations of varying part thickness as shown by the chart below. Section H (0.15 cm thick) represents the tab design utilizing a thicker middle section which facilitates a flow channel at the nozzle tip site. Section I (0.06 cm thick) represents the thin-sectioned containment flange. An objective in designing and modifying a mold with thin and thick sections is to help channel flow of the IMC composition in a desirable fashion. This can be manifested in several ways which can include:

1. Channeling of the IMC composition flow at the tab site (Section H) which preferentially deposits the IMC composition inside the mold parting line onto the surface of the part. 2. Channeling of the IMC composition flow to more critical areas

(Sections E, F, and G). 3. Restriction of IMC composition flow along the periphery of the mold and/or other portions of the mold to contain the IMC composition on the desired surface of the part and within the parting line (Section I).

The observed IMC coverage for the mold is as follows:

The foregoing show that this enhanced flow mechanism has advantages which include preferential flow and deposition to selected regions on a part as a result of varying thickness and containing IMC composition on the part surface within the parting line resulting from a thin-sectioned containment flange. The present method relates to modifying an existing mold to allow it to be utilized in connection with an injection molding machine so that the mold can be used to produce coated articles. The injection molding machine can be any of the known injection molding machines which has at least one injection apparatus to inject a molten material. The molding machine either can include a separate apparatus for injecting IMC composition or can include an integral system.

In one embodiment, an existing mold is evaluated in its preexisting state. In this respect, the mold, before modifications are made, is reviewed to obtain a complete understanding of optimal parameters including operating temperatures, pressures, the type of resin the mold is designed to receive, the mold temperature based on the resin used, and the fill patterns of the mold.

Another part of the analysis can include a determination of the type of tool steel used for the mold. Different types of tool steels have different properties which affect the machinability and performance of the steel.

Yet another part of the analysis can include a determination of the condition of the mold cavity surfaces which influence the molding process in many ways. First, the surface of the workpiece is a reflection of the condition of the surface of the mold cavity. A rough mold surface produces a workpiece with a dull or rough surface. While this may be desirable for better adhesion for a subsequent out-of-mold coating operation, the surface finish or quality of an IMC will be affected. Second, the surface finish impacts the release of the workpiece after the molding process is completed; a highly polished mold cavity releases a coated workpiece better than a non-polished cavity. Third, if the mold cavity is chromed, the manner in which the mold is modified must be adjusted. (A chrome mold cavity provides excellent surface appearance, mold release and mold life; however, the chrome finish is relatively thin. Therefore, mold cavity changes which necessitate material removal must take into consideration the chrome surface finish.)

The mold can be modified to counteract heat produced by a mold runner if it interferes with the flow if IMC on the show surface. Due to the flow of substrate-forming material through the substrate injector and injector heaters, the mold temperature around the runner is hotter than other portions of the mold. As is stated above, IMC composition flow is influenced by the compressibility of the substrate. Therefore, if the runner system is near the show surface to be coated, the mold likely will need to be modified to address the temperature issue. These modifications can include but are not limited changing the location of the runner, providing additional mold cooling near the runner, or additional mold heating near other portions of the show surface.

The present method can include modifying the mold to utilize mold cooling and/or heating to help control IMC flow. Mold cooling and/or heating can be used to help solidify the resin and/or to control the resin flow. Mold cooling can be used to reduce the time necessary to solidify the resin of the workpiece and to maintain a desired mold temperature, while mold heating can be used to prevent the resin from solidifying before the entire mold cavity is filled. This is especially important in larger workpieces and/or workpieces with intricate configurations. The typical injection molding facility has chilled plant water used for mold cooling. A first type normally used for mold cooling is cooled by a cooling tower and produces water with a temperature between 10 and 21 °C. A second type utilizes evaporative coolers which produce cooling water between 21 and 32°C, although these may be elevated if the ambient temperature is above 32°C. A third type of water is heated water wherein the injection molding facility includes capabilities of heating water and supplying the heated water to the molding operation. The molding facility can also have oil heaters for heating oil which can be used to further control mold temperature. The mold can be modified to utilize one or more of these three types of temperature controlled water and/or oil to control the flow of IMC composition. The actual modifications to the mold can include adding cooling or heating lines to the mold halves to allow for the desired flow of heated and/or cooled fluid. Furthermore, the molding system may need to be modified to accept one or more of the types of heated and/or cooled fluid. As stated above, IMC composition flow is based on the compressibility of the substrate which, in turn, is a function of substrate temperature. As the substrate cools, it begins to solidify, and solidified substrate is not as compressible as is molten resin. Cooled or chilled water can be used to reduce mold temperatures in areas of the mold which are too hot, such as the portions of the mold near the runners. Hot spots in the mold will result in areas of the substrate which are more compressible than other areas which are cooler. As a result, the IMC composition, which takes the path of least resistance, flows to the more compressible hot spot. The hot spot can be addressed by adding cooling capabilities or utilizing cooler water. The opposite is true for areas of the show surface which are last to be coated. The resin in these areas may become too solidified before the coating composition has had a chance to completely coat the surface. Since these areas of the substrate have reduced compressibility, the IMC composition may stop flowing before reaching the end of the show surface. Mold heating can slow the solidification of the substrate. By modifying the mold so that heated water and/or oil is pumped through these areas, the substrate remains in a more molten state and flow of the IMC composition is enhanced.

The mold can be modified to utilize one or more of these types of temperature controlled water and/or oil to help cure the IMC. As is stated above, the IMC is cured based on heat and, more particularly, on the heat of the substrate. Therefore, modifying the mold to include heating and/or cooling lines in the mold portion adjacent the show surface can promote curing of the IMC by optimizing the mold temperature based on the resin and IMC used. A flow modeling or analysis can be performed on the mold to determine the optimal modifications which can be made thereto. These modifications relate to obtaining a desired flow pattern of the IMC composition including obtaining complete coverage of the show surface, minimizing flow lines (especially with metallic coatings), and minimizing undesired flow of the IMC. The flow analysis determines the optimal location or placement of the IMC nozzle by breaking the show surface into grids and can utilize computer technology (e.g., flow modeling software) to determine the IMC composition flow based on the characteristics of the mold as it exists prior to modification along with modifications contemplated to introduce the IMC composition. The flow analysis can also determine if more than one IMC composition nozzle is necessary or desirable. The flow analysis also can be performed after the modifications to verify effectiveness.

The present method can involve modifying the cooling and/or heating lines or changing the location of the IMC composition injector if one or more of the lines interferes with the preferred location of the injector. If that location interferes with a cooling and/or heating line, either the line(s) or the nozzle must be moved. In view of the fact that nozzle location is very important to achieve the desired flow, modifying the line may be required. However, just eliminating the line is not always an option in that it may produce a hot or cold spot in a show surface of the mold cavity. As a result, it must be determined whether relocation of the IMC composition nozzle or modification of the cooling or heating water and/or oil line(s) is preferable. This can be done by additional flow analysis or modeling by running simulated test(s) based on both a nozzle relocation, a cooling line modification, or both. If it is determined that the best solution is to modify the cooling line, known methods can be used to remove a section of the cooling line and/or relocate the cooling line. Bubblers or fountains can be utilized if a section of the cooling is removed. While the flow is reduced using bubblers, this area of the mold still receives some flow of cooled or heated fluid, thereby reducing the severity of the hot or cold spot in the mold. This allows the optimum nozzle location to be utilized even though it interferes with a cooling and/or heating line.

The present method also can include modifying the mold to include flow enhancers to promote IMC composition flow. If the show surface includes ribs, bosses (internal openings), or intricate surfaces, the IMC composition might not flow as desired. The modification can include addition of a mold runner which can direct and/or promote flow. By creating areas of increased part thickness, flow can be enhanced by the increased compressibility of the substrate. In general, changes to the mold can be made which increase the compressibility of the substrate to promote or direct IMC composition flow.

Alternatively, the method can include modifying the mold to include flow restricters to limit IMC composition flow. If the show surface is near a parting line, a core, a slide, a shutoff, an internal parting line or an ejector pin, it may need to be modified to restrict IMC flow. As is stated above, the IMC composition is introduced into the mold cavity under significant pressure and will follow the path of least resistance. Therefore, if the show surface includes any one of these mold components, the IMC composition can exit the show surface through these components which prevents the IMC from fully coating the show surface and can affect the function of the mold. Therefore, the mold must be evaluated to determine if the IMC composition will flow into these mold components or locations. The IMC which is applied under pressure will enter any opening which is greater than about .025 mm. Ejector or core pins, for example, typically have a clearance of .05 or .075 mm and, therefore, if the show surface includes an ejector or core pin, the IMC composition can enter the ejector or core pin cavity and eventually prevent operation of the ejector or core pin. The same is true for parting lines, cores, slides, shutoffs, and internal parting lines. Next, the part configuration must be evaluated to determine if, based on its natural configuration without modification, the part is designed such that the flow of IMC composition into or out of these areas is prevented. For example, if a given molded article naturally includes a flange around the show surface which coincides with the parting line, no modification may be necessary. The naturally present flange can act as a flow restricter. However, if the natural configuration of the article does not include such a feature, the mold can be modified to incorporate flow restricting features that prevent unwanted flow of the IMC.

The method can include a modification to the part design to help enhance or limit the flow of the IMC as set forth above. The method also can include the addition of at least one IMC composition injector. Based on the flow analysis or modeling of the mold, the optimum position of the IMC injector is determined, and the mold is modified to include the nozzle. The IMC nozzle preferably is near the perimeter of the mold itself and on an edge of the show surface.

With respect to the position relative to the mold, the IMC composition nozzle is a replaceable component of the mold and, therefore, access to the nozzle helps with the maintenance of the mold. If the nozzle is buried in the middle of the tool, servicing the nozzle will be difficult. Turning to the position relative to the show surface, an IMC nozzle on the edge of the show surface can minimize the visual imperfections associated with the molding process. Flow analysis also can be used to determine whether more than one IMC composition injector is needed and to determine the optimal location of the multiple injectors. More particularly, the IMC is directed into the mold cavity in such a way that all portions of the show surface are evenly coated without the appearance of flow lines. The flow analysis determines the optimal placement of the IMC composition injector(s) to obtain the desired flow. Laminar flow across the show surface is preferred. Further, the nozzle placement can be evaluated in connection with flow enhancers or restricters described above to determine the optimal nozzle arrangement.

Referring to FIGs. 31 A-D, four different styles of nozzle arrangements are shown. FIG. 31 A depicts a smaller, less complicated part 530 wherein a single nozzle 62 is sufficient to coat the entire show surface 532. In this example, the nozzle is placed in the center of the show surface and produces laminar flow 534 about nozzle 62 in all directions. FIGs. 31 B-D depict a larger and/or more intricate part 536 with a show surface 538 where a single nozzle is not sufficient to produce the level of flow necessary to completely coat the show surface. In FIG 31 B, two nozzles 62a and 62b are shown on either side of show surface 538. The result is the creation of two separate IMC flows 540 and 542 which flow toward each other and meet at the middle of the show surface at a knit line 544. Furthermore, as the separate flows reach each other, pockets 546 and 548 are formed. The result is that the knit line is visible in the completed workpiece and pockets 546 and 548 are not coated. FIG. 31 C shows a two nozzle arrangement preferred over the one shown in FIG. 31 B. In this respect, nozzles 62c and 62d are spaced apart on the same side of the show surface. As a result, a unified single laminar flow 550 is produced by the two nozzles. In this arrangement, flow begins on one side of the show surface and flows together to the opposite side wherein no knit line is produced and air pockets are minimized.

Furthermore, if air pockets are produced, they are adjacent the edge of the show surface which may be acceptable. Referring to FIG. 31 D, if more flow is necessary, the mold can be modified to include a three nozzle arrangement 62e, 62f and 62g; however, the three nozzles preferably are still positioned so that a single laminar flow is produced. If necessary, the flow of the individual nozzles 62e-g, can be varied to provide a desired flow. In this respect, nozzle 62f can receive 75% of the flow while nozzles 62e and 62g receive together only 25%. While it has been found that the use of three nozzles has been sufficient to obtain the desired flow, more nozzles could be utilized. In addition, flow enhancers described above including mold heating and/or cooling could be used in connection with the multiple nozzle arrangements to achieve desired flow.

The size and configuration of the actual nozzle is based on the volume of the IMC composition necessary to coat the show surface. Larger surfaces necessitate the use of nozzles with larger inner diameters. The nozzle is mounted to the mold so that it can be removed for cleaning and/or replacement. The tip of the nozzle is configured to correspond with the shape of the cavity wall.

The method also can include an evaluation of and modifications to the resin injector(s) to ensure that IMC composition does not enter the resin nozzle and contaminate the resin. The location of the resin nozzle in relation to the show surface is the primary consideration. If the substrate nozzle is not within or sufficiently near the show surface, no modifications should be needed. If the nozzle is within the range of flow of the IMC, the design of the nozzle preferably is evaluated to ensure that IMC composition does not enter the resin nozzle. If it is determined that the IMC can enter the resin nozzle, the mold can be modified to incorporate one of the several discussed containment flanges to prevent IMC composition from entering the resin injector. In addition, the mold can be modified to include cooling enhancements to reduce the elevated mold temperature which may be present near the nozzle.

In modifying a mold, determining the ultimate machine conditions for the use in a given modified machine using a specific molds, substrate materials and IMC compositions is desirable. In setting up the modified mold, a large number of variables must be controlled relative to one another to produce acceptable parts based on predetermined objectives such as a minimized cycle time for the machine. More particularly, pressures, times and other variables of the modified injection machine vary with the configuration of the mold, i.e., shape of the part being manufactured and the polymeric material being used. Accordingly, the mold modification can include running a series of experiments and/or performing a flow analysis with the modified mold and a specific polymeric material to optimize the process. The volume of any given mold may be calculated. Based on this calculation and the density of the substrate-forming mateiral, the size of the charge can be determined. Differing machine variables are tried until an optimum, complete filling of the mold in a minimum time, is determined. In these experiments, the mold preferably is fitted with transducers which measure pressure and/or temperature, as various machine variables (e.g., injection speeds and pressures) are altered. In summary, an existing mold can be modified so that an IMC can be applied to at least one surface of a substrate. This modification can include one or any number of the above described modifications based on the needs of the particular mold and/or the outcome desired by the mold owner. While emphasis has been placed on the described embodiments, many changes and variation can be made without departing from the principles of the invention.

Claims

We claim:

1. A method of modifying a mold that comprises first and second mold sections which together define a mold cavity in which articles are molded, said mold (i) not accommodating introduction of a coating composition into said mold cavity when said mold sections are in a closed relation, (ii) being operable with a molding machine such that machine actuates one of said first and second mold sections relative to the other between an opened and a closed condition, and (iii) comprising at least one nozzle for directing a substrate-forming material into said mold cavity when said mold sections are in a closed relation to produce an article having at least one surface to be coated, said mold cavity having an inner surface corresponding with the at least one surface to be coated, said method comprising: a) determining a point where said coating composition desirably can be contacted with said at least one surface of said article while said article is in said mold cavity; b) creating in said mold an access hole to accept a second nozzle, said second nozzle being capable of directing said coating composition into said mold cavity and onto said at least one surface of said article while said mold sections are in a closed relation.

2. The method of claim 1 wherein the creation of said access hole does not substantially modify said inner mold surface.

3. The method of any of claims 1 to 2 further comprising at least one of the following steps: before creating said access hole, evaluating the operating conditions of said mold utilizing bracketing procedures, and determining one of a mold temperature and an article surface temperature at which injection of said coating composition produces an optimal flow thereof.

4. The method of any of claims 1 to 3 further comprising the step of performing a flow simulation of said mold before creating said access hole so as to evaluate the flow of at least one of said substrate-forming material and said coating composition.

5. The method of claim 4 wherein said flow simulation determines said desired point for said second nozzle.

6. The method of any of claims 1 to 5 further comprising using the results of step (a) to determine whether at least one of a flow enhancer and a flow restricter is needed to produce a desired flow of said coating composition on said at least one surface and, if such determination is positive, modifying said mold cavity so as to include at least one of said flow enhancer and said flow restricter.

7. The method of claim 6 wherein said coating flow enhancer includes a mold runner or a means for adjusting the temperature of a portion of said mold cavity.

8. The method of claim 7 further comprising the steps of evaluating the type and position of said mold runner and modifying said mold to account for heat produced by said mold runner and to maintain the desired flow of coating composition.

9. The method of any of claims 1 to 8 further comprising modifying said mold so as to include at least one of the following: at least one sensor for measuring variables in at least one of the machine and the mold, and at least one sensor for measuring mold temperatures.

10. The method of any of claims 1 to 9 further comprising modifying said mold so as to incorporate means for at least one of cooling and heating said mold, such modification assisting in the control of at least one of the flow of coating composition in said mold cavity and the temperature of said at least one surface of said article so as to enhance coating flow thereover.

11. The method of any of claims 1 to 10 further including the step of evaluating said article in relation to said at least one surface to be coated including sub steps of (i) evaluating relative positioning of parting lines and ejector pins and (ii) evaluating at least one of relative positioning of cores, slides, shutoffs, internal parting lines, and first nozzles.

12. The method of any of claims 1 to 11 wherein multiple access holes are created in said mold so as to accept multiple second nozzles.

13. The method of claim 12 further comprising positioning said multiple second nozzles such that flow of coating composition from said second nozzles is laminar across said at least one surface to be coated.

14. The method of any of claims 1 to 13 further comprising at least one of the following steps: determining optimal parameters for at least one of (i) volume of said coating composition to be injected into said mold cavity, (ii) time at which to inject said coating composition into said mold cavity, and (iii) pressure at which to inject said coating composition into said mold cavity; and modifying said mold cavity such that it is capable of molding an article having a thickened portion which can enhance flow of coating composition thereacross.

15. The method of any of claims 1 to 14 further comprising modifying said mold cavity so as to utilize substrate compressibility to direct said coating composition across said at least one surface.