WO2009140499A2

WO2009140499A2 - Coating application thermal stabilization system

Info

Publication number: WO2009140499A2
Application number: PCT/US2009/043960
Authority: WO
Inventors: Michael R. Bonner
Original assignee: Bonner Michael R
Priority date: 2008-05-14
Filing date: 2009-05-14
Publication date: 2009-11-19
Also published as: WO2009140499A3

Abstract

The Coating Application Thermal Stabilization (CATS) System is a complete approach to stabilizing the substrate and the coating material temperatures involved in coating application processes. It involves the combination of point of use temperature control of the coating material being applied and a substrate thermal measurement/correction system located directly before the coating station or booth to assure accurate temperature of the part or substrate entering the coating process.

Description

COATING APPLICATION THERMAL STABILIZATION SYSTEM

BACKGROUND

[0001] This invention pertains to coating systems. More particularly, this invention pertains to methods and systems for dispensing coating material(s) onto a substrate.

[0002] It is well understood by industrial processors who apply coatings (paints, sealers, adhesives, etc.) to "substrates" (items made from wood, metal, plastic, composite, etc.) that variation in temperature will affect characteristics of the coating material being applied. Among the temperature- dependant characteristics are physical characteristics such as viscosity.

[0003] Variations in coating material viscosity will affect the quality of the application with regard to attributes such as at least one of film build, color match, surface finish, gloss, orange peel, adhesion/blistering, solvent pop, etc. There are many systems available to accomplish material temperature control including heat-only, cool-only, and heat/cool types. Some of these can be configured to work with either recirculating or dead-end systems. It is also well understood that variations in ambient air temperature and humidity, can have an impact on the coating performance. For this reason it is common to have temperature and humidity control on the make-up air system for the coating booth or area. Substrate temperature is rarely, if ever, taken into account or actively managed.

[0004] The parts to be coated may be obtained from a chemical pre-treatment process, or a prior curing stage, or they may be coming from storage at any given ambient temperature depending on geographical location, season, time of day, etc. This variation in the surface temperature of the part to which the coating material is being applied will also have a significant impact on the performance of the coating and the final result of the coating process.

[0005] Thus, it would be desirable to provide a method and/or system that would provide for coating application that permits successful application of coating material to a variety of substrates at varying substrate temperature. Other objects and features will be come apparent upon review of the present disclosure.

SUMMARY

[0006] The Coating Application Thermal Stabilization (CATS) System involves the combination of point of use temperature control of the coating material being applied and a substrate thermal measurement/correction system located directly before the in-line coating station or booth to ascertain accurate temperature of the part or substrate entering the coating process and provide accurate substrate- material thermal correlation. The apparatus set forth herein includes at least one temperature adjustment device configured to accomplish temperature change in the region of the part proximate to at least one surface region; at least one temperature sensor positioned proximate the temperature adjustment device, the temperature sensor configured to measure the temperature of the substrate. The apparatus also includes at least one coating application device in electronic communication with the temperature sensor, the coating apparatus capable of delivering temperature controlled coating material into contact with the surface region of the substrate.

BRIEF DESCRIPTION OF THE DRAWING

[0007] In order to more fully understand the present invention, the following drawing is presented in which like reference numbers are use throughout the various drawing figures and in which::

[0008] Figure 1 is a side view of an embodiment of the coating process line with a thermal pre- treatment booth inserted before and directly adjacent to the coating booth as disclosed herein;

[0009] Figure 2 is an end view of a an embodiment of a rectangular thermal pre -treatment booth configuration;

[0010] Figure 3 is an end view of an embodiment of a hexagonal thermal pre-treatment booth configuration; and

[0011] Figure 4 is an end view of an embodiment of an oval thermal pre-treatment booth configuration.

DETAILED DESCRIPTION

[0012] Disclosed herein is a coating system herein referred to as the Coating Application

Thermal Stabilization (CATS) System. This method and system is directed to an integrated approach to stabilizing both the substrate and the coating material temperatures involved in in-line, repetitive coating application processes. The method comprises application of at least one point of use temperature control of the coating material being applied and a substrate thermal measurement/correction system located directly before the coating delivery device such as the coating station or booth to assure accurate temperature of the part or substrate region entering the coating process.

[0013] The Coating Application Thermal Stabilization (CATS) System is an integrated approach to stabilizing the substrate and the coating material temperatures involved in in-line, repetitive coating application processes. It involves the combination of point of use temperature control of the coating material being applied and a substrate thermal measurement/correction system, herein referred to as a thermal pre-treatment booth, positioned directly before the coating delivery device such as the coating station or booth to assure accurate temperature of the part or substrate entering the coating process.

[0014] This process can be scaled to temperature stabilize any repetitive coating process irrespective of part size, geometry, composition or coating material. It is especially useful where highly accurate coating and curing is required such as in adhesive or sealing applications, or wet-on-wet coating processes often associated with paint and ink application with multiple colors and/or protective top coats.

[0015] In critical finishing and deposition operations, temperature variations during application can have significant impact on the performance of the applied coating material. Variations in coating material temperature will result in variation in viscosity that will result in changes in deposition thickness (both wet and dry film) which can result in issues with adhesion, color match, gloss, etc. Often, in the past, these variations in viscosity are addressed by adding solvent to the coating material, primarily when the viscosity is higher than desired. This addition of solvent negatively impacts the curing profile of the coating material and can result in solvent pop, blistering, "orange peel", and other finish/curing related defects. In addition, the added solvent must all be removed in the curing process, thus adding unnecessary cost and increasing emissions which have a negative impact on the environment. Any defects incurred in this process will result in additional rework or scrap costs to the operation.

[0016] In order to create a stable, repetitive process in which the coating material application attains a first pass yield approaching 100%, factors such as booth air temperature and humidity are often controlled as a function of the make-up air system. Even in operations where this is not controlled, the two primary temperature variables in the coating process are the coating material temperature and the temperature of the substrate to which it is being applied. The inventors have found that control and reconciliation of the substrate and coating material temperature relative to one another can minimize undesirable outcomes such poor coating performance and the like. The Coating Application Thermal Stabilization (CATS) System addresses both of these and the method disclosed herein provides a strategy for addressing these process variables directly.

[0017] In the method disclosed herein, the first step is directed to the temperature adjustment of the substrate surface in a suitable thermal environment. It is to be understood that temperature adjustment can involve either temperature elevation or decrease. In many applications, it is contemplated that the temperature adjustment will involve elevation of the temperature surface. In the embodiment of the apparatus depicted herein, it is contemplated that temperature adjustment will involve temperature elevation of the substrate and that the apparatus will include at least one heater bank including at least one radient heater, IR heater resistance heater, air knife, or the like. It is also contemplated that the apparatus can include suitable temperature reduction means of which an air knife is one example.

[0018] One embodiment of the CATS System is the Thermal Measurement/Pre -Treatment Booth is shown in Figure 1. The pre-treatment booth 1 is placed in series with, and directly before and adjacent to the entrance of a suitable coating application device such as the coating booth so depicted. In the embodiment depicted in the drawing figure, the material is conveyed through the device by as suitable conveying means such as a part conveyor 2 that carries the part 3 to be coated through the process. Though this is shown as a belt type conveyor in the illustration, this could also be a hanging type conveyor with the parts being suspended from above, if desired or required.

[0019] The booth 1 can be divided into suitable temperature adjustment zones. In the embodiment depicted, the booth as shown is divided into two temperature adjustment zones, however any number of zones could be created, as required, to assure that the part(s) exit the thermal pre-treatment booth 1 at the proper temperature. It is contemplated that the temperature of the substrate as it traverses each zone will be monitored and suitable temperature data will be relayed to any suitable processor and/or controller (not shown) as desired or required. In the embodiment depicted in the drawing figure 1 , the substrate temperature can be monitored by a suitable device such as a temperature sensor or an IR thermometer 4. In the embodiment depicted, the temperature monitoring device is positioned in the thermal pre-treatment booth 1 at the end of one or more thermal zones. It is also contemplated that the temperature read can be determined at one or more locations on the substrate surface at ascertain an accurate measurement of the substrate surface temperature where desired or required. Thus, the temperature monitor can include suitable temperature probes and the like.

[0020] In the embodiment depicted in Fig. 1 , the IR thermometer 4 is configured and directed to read the temperature of the part 3 in a designated location as it travels through the thermal pretreatment booth 1. The temperature information collected is fed to a control loop that determines the output of the thermal devices 5 located upstream of thermometer 4. It is contemplated that the temperature adjustment device can be configured such that the final reading in the last zone is taken just as the part 3 leaves the thermal pre-treatment booth. The part spacing shown is nominal and the control loop can be configured as desired or required. It is contemplated that non-limiting examples of suitable control loop configurations and devices can be suitable proportional-integral-derivative (PID) type devices or other types as necessary to adjust to the varying loads, different part geometries, substrate materials, feed rates, and the like. [0021] The shape of the thermal pretreatment booth 1 can be any geometry suitable to achieve the desired temperature adjustment. It is contemplated that the geometry of the booth can vary according to the geometry of the substrate(s) to be coated. Three non-limiting examples of booth profiles are shown in Figures 2 - 4, though it is understood that the actual implementation is not limited to these selections. Figure 2 shows a rectangular booth profile 1 with four temperature control planes 5. Figure 3 shows a hexagonal booth profile 1 with three temperature control planes 5. And Figure 4 shows an oval booth profile 1 also with three temperature control planes 5.

[0022] In an implementation designed for elevating substrate temperature, it is contemplated that the thermal devices can be infrared heating elements, the type, number and location of these strategically placed to assure even heating of the part(s) to be coated based on factors including but not limited to part geometries, substrate material composition, feed rate and the like.

[0023] In yet another implementation, the thermal devices could be air knife type jets with temperature controlled air being moved past the part 3 at high velocity to modify its temperature. It is also contemplated that this approach can be advantageously employed where it may be necessary to cool the substrate prior to coating, i.e. - near ambient substrate temperature targets. In some implementations, the source of the air employed in devices such as an air knife may be derived from, the make-up air system to assure that the part is brought to the coating process at the same temperature as the booth air. In addition to the thermal correction function, if properly implemented, the air knife type system can also provide a "blow-off function to assure that there is no "dirt" or moisture on the surface of the substrate when it is moved to the coating booth, thus reducing contamination defects which are often the most prevalent in the coating operation.

[0024] The apparatus disclosed herein also includes a suitable coating application device such as a coating booth or the like such as coating booth 10. In the coating application device, the temperature of the coating material being applied can be measured and adjusted with an automatic temperature control system to the specific target temperature designated as optimal to assure best performance of the coating material and application process parameters. In coating processes where the material application system is "dead-end" (where material flow starts and stops with each triggering of an applicator gun), the temperature control system can be of a type and configuration that can control the temperature of the coating material from coating reservoir all the way to the dispensing point. It is contemplated that such systems could be advantageously employed in processes involving the application of adhesives, sealants, etc. In systems where the coating material is circulated continuously, an in-line temperature control system in the recirculation loop may be utilized. [0025] The temperature control system employed will be one that assures that the temperature of the coating material being applied is tightly controlled at the point of application. In most cases, this will call for a dedicated temperature control loop for each dispensing point, especially in situations where multiple coating materials are being applied at one time.

[0026] The active adjustment of both substrate and coating material temperature permits the stabilization of the process and exploitation of specific coating material formulation options. This can bring a number of benefits. In the case of wet-on-wet application processes cited above for instance, the formulation of a first coat applied can incorporate "faster" solvents that will typically evaporate shortly after application while the second coat may be formulated with "slower" solvents to allow curing of the layers in order of application without top-layer surface degradation. The temperature adjustment of the coating material(s) and substrate exploit the vapor pressure and flash-off rates of these formulations to assure desired performance. For instance, the substrate and first coat temperatures may be elevated to "drive -off ' the bulk of the solvents in the interim after application of the first coat but prior to the application of the second coat. The temperature of the second coat may also be adjusted independently to assure that it facilitates proper curing of the first coat. In this fashion, the effect of solvent passing through the top layer(s) and associated defects such as orange peel, blistering, solvent pop, reduced gloss, etc. can be minimized or eliminated. Though described here for a two coat wet-on-wet process, additional coatings may also be added to achieve 3 or 4 or more layers with the coating material formulation and process parameters of each layer and associated temperatures being controlled to facilitate desired performance. It is contemplated that the process disclosed herein can eliminate intermediate curing stages between coating layers and the associated costs related to equipment purchase and installation, plant footprint, energy use, operation and maintenance, etc in at least some applications.

[0027] It is also contemplated that the apparatus and the method disclosed herein can address problems of seasonal or regional performance variations. When the temperatures in the coating process i.e. the substrate temperature and/or the application temperature of any coating material(s), are under active control, seasonal variations can be reduced or eliminated. In certain materials, it is common practice to add solvents to the coating material to compensate for changes in viscosity related to ambient temperature variation. Clearly, this changes the formulation and the curing profile of the coating material and creates instability in the coating process. In addition, these additional solvents add cost and must be removed and dealt with during the curing process. When additional added solvents are removed during the curing process, often an oven, they increase the solvent build-up rates in the process. This will require additional make-up air in the process to assure that the fuel-to-air mixture does not reach the "Lower Explosive Limit" (LEL) for the system. This additional air often must be heated (thus increasing the energy used and the cost incurred) and must also be remediated to remove the solvents prior to release to the atmosphere. This remediation is often performed in a "Regenerative Thermal Oxidizer" (RTO). If the solvent input into the system can be reduced through process and formulation control, the oven and RTO size and operating costs can be significantly reduced.

[0028] In addition to reducing the system specification, footprint, purchase, installation and operation costs; by eliminating the coating process changes associated with temperature variations, system repeatability and first pass yield can be significantly increased. This results in reduced rework and scrap costs and increases coating system utilization and throughput.

[0029] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.

ADDITIONAL CLAUSES [0030] A. A method for applying a coating material to a substrate comprising the steps of: introducing a coating material to at least a portion of a substrate surface, the substrate temperature having a first temperature, wherein the coating material has a second application temperature, the second coating application temperature adjusted to coordinate with the first measured temperature of the substrate surface.

[0031] B. The method of clause A further comprising the step of exposing the substrate to at least one temperature adjustment process prior to the coating introduction step.

[0032] C. The method of clause B wherein the substrate temperature is measured and factored into at least one of adjustment of the second coating application temperature and adjustment of the substrate temperature.

[0033] D. The method of claims B or C wherein the heating step includes introducing the substrate to at least two temperature adjustment steps.

[0034] E. The method of clause B throuth D wherein the heating step includes at least one temperature measurement step. [0035] F. The method of clause C, D, or E wherein at least one temperature adjustment is heating.

[0036] G. The method of clause B, C, D, or E wherein the temperature adjustment step includes variable application of heat over different regions of the substrate.

[0037] H. The method of clause B further comprising the step of introducing at least one additional coating material to a portion of the substrate.

[0038] I. The method of clause H wherein the at least one additional coating material is introduced in overlying relationship with at least a portion of the first coating material.

[0039] J. A device configured to accomplish the method of clause A-I comprising at least one substrate temperature adjustment zone, at least one temperature measurement device positioned at a exit of said temperature adjustment zone, the temperature measurement device configured to measure the temperature of the substrate and at least one coating application device adapted to receive input from the temperature measurement device.

[0040] K. The device of clause J wherein the temperature adjustment zone comprises at least one heater.

[0041] L. The device of clause J or K wherein the temperature adjustment zone further comprises at least one heater bank, the heater bank including at least one of a radiant heater and IR heater, a resistance heater and an air knife.

[0042] M. The device of clause J further comprising at least control loop device communicating between the temperature measurement device of the heating zone and at least one temperature controller associated with the coating application device.

[0043] N. The device of clause M wherein the control device is at least one PID.

Claims

What is Claimed:

1. An apparatus for applying temperature controlled coating material to a substrate comprising: at least one substrate temperature adjustment device; at least one temperature sensor positioned proximate to said temperature adjustment device, the temperature measurement sensor configured to measure the temperature of the substrate; and at least one coating delivery device in electronic communication with the temperature sensor, the coating delivery device configured to deliver coating material 1 to the substrate surface at a coating temperature wherein said coating temperature is adjusted to coordinate with the substrate temperature measured by the temperature measurement sensor..

2. The apparatus of claim 1 wherein the temperature adjustment device comprises at least one heater.

3. The apparatus of claim 1 or 2 wherein the temperature adjustment device includes at least one heater bank, the heater bank including at least one of a radiant heater, an IR heater, a resistance heater, and an air knife.

4. The apparatus of claim 1 wherein the coating delivery device includes at least one temperature controller further comprising at least control loop device communicating between the temperature sensor of the temperature adjustment device and at least one temperature controller associated with the coating delivery device.

5. The apparatus of claim 4 wherein the control device is at least one proportional-integral- derivative controller.

6. The apparatus of claim 1, 2, 4, or 5 wherein the temperature adjustment device includes means for reducing temperature of the substrate.

7. The apparatus of claim 1 further comprising a conveyor device extending through the substrate temperature device and the coating delivery device.

8. The apparatus of claim 1 or 3 or 7 wherein the temperature adjustment device comprises a plurality of heater banks disposed at various angles relative to the substrate.

9. The apparatus of claim 8 wherein the temperature adjustment device comprises a plurality of temperature adjustment zones.

10. A method for applying a coating material to a substrate comprising the steps of: introducing a coating material to at least a portion of a substrate surface, the substrate temperature having a first temperature, wherein the coating material has a second application temperature, the second coating application temperature adjusted to coordinate with the first measured temperature of the substrate surface.

11. The method of claim 10 further comprising the step of exposing the substrate to at least one temperature adjustment process prior to the coating introduction step.

12. The method of claim 10 or 11 wherein the substrate temperature is measured and factored into at least one of adjustment of the second coating application temperature and adjustment of the substrate temperature.

13. The method of claim 10 or 11 wherein the heating step includes introducing the substrate to at least two temperature adjustment steps.

14. The method of claim 10 or 11 wherein the heating step includes at least one temperature measurement step.

15. The method of claim 12 wherein at least one temperature adjustment is heating.

16. The method of claim 12 wherein the temperature adjustment step includes variable application of heat over different regions of the substrate.

17. The method of claim 10 further comprising the step of introducing at least one additional coating material to a portion of the substrate.

18. The method of claim 17 wherein the at least one additional coating material is introduced in overlying relationship with at least a portion of the first coating material.