WO2001061320A1

WO2001061320A1 - Plural component coating analysis

Info

Publication number: WO2001061320A1
Application number: PCT/US2001/005037
Authority: WO
Inventors: Craig R. Kowalski; Bruce R. Kowalski
Original assignee: Kowalski Craig R; Kowalski Bruce R
Priority date: 2000-02-15
Filing date: 2001-02-14
Publication date: 2001-08-23
Also published as: WO2001061320A9; AU2001238393A1

Abstract

A method for analyzing a surface coating in which a plural component coating is applied to a surface and at least a portion of the infrared spectrum of the applied coating is measured. The measured infrared spectrum provides information that allows the determination of the ratio of the plural components, and the method includes the step of determining whether the ratio of plural components is within predetermined limits to provide a surface coating meeting desired specifications.

Description

FIELD METHOD AND DEVICE FOR ANALYZING A PLURAL- COMPONENT COATING

Field of the Invention The present invention relates to a field method and device for analyzing a plural-component coating by infrared spectral and imaging technology.

Background of the Invention Plural-component coatings advantageously have each component of the coating in a particular amount relative the coating's other component or components. To achieve in-specifϊcation reactivity for onsite manufactured coatings, the components of a plural-component coating should be within specified amounts relative to each other. A method for determining the proper ratios of plural components to determine whether the applied plural-component coating has the requisite composition would ensure greater efficiency and effectiveness. Spectroscopic methods, including infrared and Raman spectroscopy in their various forms, have long been used to determine the identity and concentration of individual chemical components in a wide variety of samples. In general, all or part of an infrared or Raman spectrum can be acquired by placing the sample to be analyzed in a spectrometer, contacting the sample with a probe connected to a spectrometer, or alternatively, by one of the noncontact methods of analysis (e.g., specular reflectance, passive emission, or attenuated total reflectance). These methods are most commonly employed by transporting samples to a laboratory for analysis. Currently, the technology to monitor the reactivity of plural components in coating applications is not available to the coating industry. Accordingly, there exists a need for a method for onsite analysis of plural-component coatings. The present invention seeks to fulfill this need and provides further related advantages. Summary of the Invention

In one aspect, the present invention provides a method for analyzing a surface coating. In one embodiment, the invention provides a method for analyzing a plural- component coating that is formed by applying two or more components to a surface. The method includes determining whether the ratio of components is within predetermined limits to provide a surface coating meeting desired specifications. In another embodiment, the method includes applying two or more components to a surface to provide a plural-component coating having a ratio of components, and determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications. In these methods, determining whether the ratio is within predetermined limits includes measuring at least a portion of the infrared spectrum of the coating, which provides spectral data that allows for the determination of ratio of the components.

In a further embodiment, the invention provides a method for analyzing a plural-component coating formed by applying two or more components to a surface. The method includes measuring at least a portion of the infrared spectrum of the coating to obtain spectral data, which provides information that allows for the determination of the ratio; and determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications. In another embodiment, the method includes applying two or more components to a surface to provide a plural-component coating having a ratio of components; measuring at least a portion of the infrared spectrum of the coating to obtain spectral data, which provides information that allows for the determination of the ratio; and determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications. In another aspect of the invention, a device for analyzing a surface coating in accordance with the methods noted above is provided.

In a further aspect, the invention provides a method for determining the homogeneity of a surface coating. In one embodiment, the method includes obtaining spectral data for a surface coating at a first location on the coating; obtaining spectral data for the surface coating at a second, different location on the coating, comparing the spectral data obtained from the first and second locations to determine whether the coating is homogeneous within predetermined limits to provide a surface coating meeting desired specifications. The spectral data comprises at least a portion of the infrared spectrum of the coating. The coating can include a single component or can be a plural-component coating.

In other aspects, the invention provides methods for testing equipment for applying a surface coating, and for setting standards for plural-component coatings.

Brief Description of the Drawings The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a flowchart illustrating a representative method for analyzing a plural-component coating in accordance with the present invention; FIGURE 2 shows infrared spectra of a representative plural-component coating (two-component commercial urethane coating) as a function of time;

FIGURE 3 shows infrared spectra of three representative urethane coatings, the spectrum labeled A illustrates a coating having a proper ratio of components, the spectrum labeled B illustrates a coating that includes an excessive amount of isocyanate-containing component, and the spectrum labeled C illustrates a coating having an excessive amount of resin component;

FIGURE 4 is an infrared spectrum of a representative polyurethane coating; FIGURE 5 is an infrared spectrum of a representative polyurea coating; .FIGURE 6 is an infrared spectrum of a representative epoxy coating; and FIGURE 7 is a schematic diagram of a representative device for performing the method for analyzing a plural-component coating in accordance with the present invention.

Detailed Description of the Preferred Embodiment In one aspect, the present invention provides a method for analyzing a surface coating. In one embodiment, the invention provides a method for analyzing a plural- component coating that is formed by applying two or more components to a surface. The method includes determining whether the ratio of components is within predetermined limits to provide a surface coating meeting desired specifications. In another embodiment, the method includes applying two or more components to a surface to provide a plural-component coating having a ratio of components, and determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications. In these methods, determining whether the ratio is within predetermined limits includes measuring at least a portion of the infrared spectrum of the coating, which provides spectral data that allows for the determination of ratio of the components.

As noted above, the invention provides a method for analyzing a plural- component coating. As used herein, the term "plural-component coating" refers to a coating that results from two or more coating components applied to a surface. The method includes the use of infrared or Raman spectral and imaging techniques to monitor individual coating components to ascertain the proper ratios of the coating's plural components.

The method of the present invention takes advantage of the fact that it is possible to perform infrared or Raman analysis of films or coatings that have been sprayed or otherwise applied to a surface. High-quality infrared spectra can be obtained from coatings (e.g., polymeric coatings) over the course of time beginning at application of the coating's components and continuing through the period of curing or setting of the coating.

The infrared spectra of a representative plural-component coating as a function of time is illustrated in FIGURE 2. FIGURE 2 shows infrared spectra acquired over time during the reaction of a two-component commercial urethane coating. The noted bands are identified by wavenumber (units of reciprocal centimeters) assignment in the figure and are associated with chemical changes during the reaction (curing process). Bands identifying functional groups associated with the curing reaction that are increase in intensity during reaction include bands at 1137 (C-O-C), 1230 (N-C=O, amide), 1514 (amide), 1730 (urethane carbonyl amide), and 3390 (NH stretching.) Bands that are relatively static in intensity and that shift in wavelength during reaction include bands at 1692 (total carbonyl) and 2800-3100 (CH stretching). Two bands that decrease in intensity during the reaction, as is consistent with urethane polymer chemistry, include the bands at 2271 (N=C=O, isocyanate) and 3529 (OH stretching). Accordingly, such spectral information obtained from a plural-component coating by an infrared or Raman spectrometer or filter-based instrument allows for the monitoring of the coating's curing process from beginning to end. The spectral information permits the determination of whether the ratio of plural components is proper for a particular coating. The infrared spectra of three urethane coatings is illustrated in FIGURE 3. Referring to FIGURE 3, the spectrum labeled A illustrates a coating having a proper ratio of components, the spectrum labeled B illustrates a coating that includes an excessive amount of isocyanate-containing component, and the spectrum labeled C illustrates a coating having an excessive amount of resin component. These spectra show that the coatings are distinguishable at the molecular level and that by focusing on select infrared absorbance bands, it is possible to detect improper component ratios. The detection then permits correction of the off-ratio application.

An example of an infrared analysis by the method of the invention is illustrative. For a polyurethane coating, the isocyanate functional group spectral band can be monitored. An on-ratio coating has the isocyanate functional group spectral band at a minimum when the coating is cured. For an off-ratio coating (a coating with an improper ratio of plural components), the isocyanate band would remain as a prominent peak in the infrared spectrum. The coatings technician knows that the coating components are in proper ratio when the isocyanate band has diminished intensity and matches the band intensity size in the calibration spectrum of a properly manufactured coating as found in the stored library.

The spectra illustrated in FIGURES 2 and 3 show dramatic differences in changes over time of cure between a coating prepared from in-specification application of the plural components (i.e., proper ratio) and a coating obtained from the application of plural components with improper ratios (e.g., outside the specifications supplied by the manufacturer).

The method of the invention can utilize a variety of infrared or Raman monitoring techniques to monitor the progress of the reaction of plural components in a wide variety of coatings in situ (i.e., in the field of application or in a manufacturing or OEM application). With this information, corrections to the ratios of the plural components can be made during the application process to ensure that the final product will be within the manufacturer's specifications to provide the desired optimum coating. Through the method of the invention, plural-component coatings can be applied to a surface at a correct ratio, thereby eliminating the waste and expense involved with removing and disposing of coatings that result from off- ratio application of components.

As noted above, in the method of the invention, a form of infrared spectroscopy is used to analyze the surface coating. Applicable forms of infrared spectroscopy include, but are not limited to, short wavelength near infrared; near infrared; mid infrared; and far infrared regions. The analysis can be made utilizing transmission, reflectance, and emission infrared spectroscopic techniques. All forms of Raman spectroscopy can also be used to analyze the surface coating.

The method of the invention has wide applicability. For example, the method can be used to analyze the coating applied to a potable water tank. When the inside of a potable water tank is coated, quite often the final coated product may appear satisfactory even though the correct ratio of components was not achieved. When such a tank is put into use, the improperly cured coating can release harmful components into the water supply. Through the use of the method of the invention, the correct ratio of components can be assured and the problem of improperly applied coating avoided.

The method of the invention can be applied to all plural-component coatings in which the final product and/or one or more of the components have distinctive infrared spectra. The method is applicable to, but is not limited to, all isocyanate- based two-component coatings including, for example, polyurethane-containing coatings (see FIGURE 4 for a representative spectrum) and polyurea-containing coatings (See FIGURE 5 for a representative spectrum). These coatings generally include use isocyanate as one component (a hardener) with the other component being a resin material that contains various chemical formulations that determines the coating's physical properties. The method is also applicable to other plural component coatings including, for example, epoxy-containing coatings (see FIGURE 6 for an absorbance spectrum acquired with an ATR sampling device on a cured two-component epoxy coating), vinyl ester-containing coatings, and polyurethane-containing foam insulation, among others. The method of the invention is applicable to the analysis of field spray plural-component coatings. A list of representative coatings that can be analyzed by the method of the invention is shown in Table 1. Table 1. Representative Plural-Component Coating Types.

Manufacturer Product Name Type

Anna Coatings Anna Coatings Polyurea

Coatings International Polyarmor (aliphatic) Polyurea

Coatings International Polyarmor (aromatic) Polyurea

Fibre Glass Dev. Corp. 1110-B Vinyl Ester

Futura Coatings Geothane Hybrid

Futura Coatings Geothane 5020 Urethane Manufacturer Product Name Type

Futura Coatings Futura-thane 535-528 Urethane

Futura Coatings Protec II PW Urethane

Futura Coatings Ultra-liner 371-373 Epoxy

Futura Coatings PROTEC Epoxy

Futura Coatings Pipe Mate Epoxy

Futura Coatings Futura-thane 527 Polyurea

Futura Coatings Ura-Shield Polyurea

Futura Coatings Futura-Clad Polyurea

Futura Coatings Futura-Thane 532 Polyurea

Innovative Coatings Corp. Innovative Coatings Corp. Polyurea

Interplastics Corp. Chemi-Cote 3000G Vinyl Ester

Interplastics Corp. VE8300 Vinyl Ester

Line-X Advanced Composite Technology Line-X Polyurea

Optiflex Coating Technologies Inc. Optiflex pc520 Polyurea

Polibrid Coatings Polibrid 705 Polyurea

Raven Lining systems Raven 800 series Polyurea

SPI Polyshield SS-100 Polyurea

The method of the invention for analyzing a surface coating includes the following steps of applying a plural-component coating to a surface; measuring at least a portion of the infrared spectrum of the applied coating, the measured infrared spectrum providing information that allows for the determination of ratio of the plural components; and determining whether the ratio of the plural components is within the predetermined limits.

If the applied components are in proper ratio, the coating applications continues to provide a surface coating having the desired properties (e.g., the coating meets the manufacturers suggested specifications). If the applied components are not in proper ratio, the application of the components is adjusted by the application technician until the proper ratio is achieved as determined by the method. Adjustment by the application technician can include making necessary changes to the application equipment and/or the applied components.

The method can be performed using a device that can obtain the infrared data. In one embodiment, the device also compares the acquired infrared data for the coating with a calibration standard and indicates whether a proper ratio of components has been achieved. In a representative coating application, the device (e.g., an infrared or Raman spectrometer or equivalent) is prepared for the coating application by positioning the device and setting for the coating type. The application of the plural components to a surface then begins. After application of a plural-component coating, infrared spectral data is acquired and the data compared to in-specification data bank for the coating type. If the comparison indicates that amounts of components are in the proper ratio, application of the components is continued. If the comparison indicates an incorrect ratio, the component ratio is adjusted as necessary, a new coating applied, and the spectral data for the new coating acquired. Adjustment can be made by the application technician until the proper ratio is achieved as determined by the method. Adjustment by the application technician can include making necessary changes to the application equipment and/or the applied components. After initial comparison and continued application, the comparison is again made as necessary until coating is complete. The method provides a complete data file to indicate in- specification of the final coating product. Additional data acquisition can be determined as required for particular coating types.

A representative method for applying a plural-component coating with analysis of the plural-component coating in accordance with the invention is illustrated in FIGURE 1. Referring to FIGURE 1 , the representative method includes the steps of setting up the device for measuring the infrared spectrum of the coating. In operation, the device is connected to an appropriate electrical power source, powered on, and allowed to warm to operating temperature. The device is then calibrated using a sample that has been approved as to its quality (e.g., component ratio and homogeneity) and of the same type as to be applied and analyzed. The next step is to apply the coating components to a surface (e.g., spraying the components onto the actual surface to be coated or a sample surface referred to as a coupon), allowing the applied components to dry (drying times vary among coatings), and then analyzing the coated surface by infrared measurement. The coated surface is analyzed by a suitable device. Depending on the type of device, the coated surface can be held in place on the device mechanically, or a sensing probe can be used to interrogate the coated surface. The device then measures the infrared spectrum of the coated surface and compares the obtained spectral information with the calibration data. If the spectral data indicates that the ratio of applied components is within specification (i.e., on-ratio), surface coating continues. If the spectral data indicates that the ratio of applied components is outside of the specification, (i.e., off-ratio), the amount of an applied component is adjusted, a subsequent surface coated, and the resulting coating analyzed as noted above. Adjustment by the application technician can include making necessary changes to the application equipment and/or the applied components. This method of testing is repeated as necessary until analysis indicates a surface coating having a proper component ratio (i.e., on-ratio). Once an on-ratio coating is obtained, the surface coating application proceeds. As the coating continues, additional test surfaces (e.g., sample coupons) can be sprayed and analyzed as outlined above. The frequency of the collection of test coatings can be determined by the specifications set by the individual project, material manufacturer, standards organization, and/or trade organization.

The method can provide a complete data file to indicate in-specification of the final coating product. The device can transmit the spectral data to a personal digital assistant (PDA) device (e.g., PALM PILOT) or personal computer, which can create a coating project data file. Such a file can include parameters such as the time, date, weather conditions, project name, measured spectral data, and other information the operator may desire to record.

In another aspect, the invention provides a device for performing the analysis of a plural-component coating. Suitable devices include any device that can obtain at least a portion of an infrared spectrum of a coated surface. In one embodiment, the device is a Fourier transform infrared (FTIR) spectrometer with an attenuated total reflectance (ATR) attachment capable of acquiring the entire infrared spectrum. In other embodiments, the device can include other instruments and attachments including wavelength and/or energy dispersive spectrometers that can employ a wide variety of cells, probes, and sampling devices. In other embodiments, the device can be a spatial/spectral imaging and/or imaging spectrometer as these instruments provide the necessary spectral information over the surface and/or into the depth of the coating. In another embodiment, the device is a filter-based infrared spectrometer in which the filter or filters are selected to match the specific spectral regions where the composition of one or more of the plural components in the coating being applied can be measured (e.g., the isocyanate band for a polyurethane).

The device and/or its associated computer can include a library of calibration spectra for reference manufactured coatings.

Representative sampling (sample-to-measuring device connection) methods that can be used for analyzing surface coatings in accordance with the invention include non-contact and contact methods for analyzing the plural component coating applied to the actual surface being coated. Alternatively, sampling can include sampling of a surrogate surface (also referred to herein as a "coupon"), that is, a sample surface to which the plural-components are applied prior to actual application of the components to the surface to be coated. The use of such a coupon allows the method of the invention to utilize currently available, inexpensive filter-based devices. One suitable filter-based device useful in analyzing a surface coating in accordance with the present invention is the INFRACAL infrared filtrometer commercially available from Wilks Enterprises Inc., (Norwalk, Connecticut). An optical schematic of the device is illustrated in FIGURE 7. The filtometer can include flat mounted AMTIR - 1 Fresnel prisms mounted in optical cards as coupons. In such an instrument, the coating's components can be applied to a coupon that is then placed on the INFRACAL instrument that includes two or more wavelength filters selected to determine the ratio of the plural components. After coating and analysis, the coupon can be cleaned and reused or discarded and a new one used. The process of coating the coupon and then measuring the ratio of the applied plural components can be continued until the proper ratio of the coating's plural components is achieved and determined. Once the correct ratio is obtained, actual coating of the surface of interest can be commenced.

Referring to FIGURE 7, the portion of representative device 10 includes an infrared source 12, detector 14, and optionally one or more filters 16. In this device, coated surface 20 is analyzed by attenuated total reflectance using an internal reflectance element (IRE) 18. In the figure, the infrared light path is illustrated by the arrowed lines emanating from source 12, interrogating sample 20, and entering detector 14. In another aspect, the invention provides a method for testing a piece of equipment used in the coating process. In the method, the piece or pieces of equipment are tested by using the equipment and applying a plural component coating to a surface, and then analyzing the coating to see if a proper coating is achieved. By such a method, it is possible to test or compare some or all of the equipment used in a coating application. For example, two spray guns can be compared by applying the same plural component coating under identical conditions and then comparing the spectral data or instrument readings obtained from the coatings from both spray guns.

In a further aspect of the invention, a method for setting standards for plural- component coatings with desirable properties is provided. For example, a coating with desirable physical properties (e.g., elasticity and/or durability) can be formed and analyzed by the method of the invention described above and the resulting data stored in as a member in a library of standards. Then, for field operations, only those coatings having spectral data equal to (or comparable and within set tolerances or variances) those of the established standard would be acceptable.

Another aspect of the invention provides a method for determining the homogeneity of a surface coating. In the method, the method described above is used to sample a surface coating at various points on the surface. Through measurement of the infrared spectrum, the degree of homogeneity, or conversely, heterogeneity, of a coating over a given area can be determined. The method for determining homogeneity of a coated surface is effective in determining the homogeneity of single and/or plural-component coatings, including those noted above.

In one embodiment, the method for determining the homogeneity of a surface coating includes obtaining spectral data for a surface coating at a first location on the coating; obtaining spectral data for the surface coating at a second, different location on the coating, comparing the spectral data obtained from the first and second locations to determine whether the coating is homogeneous within predetermined limits to provide a surface coating meeting desired specifications. The spectral data comprises at least a portion of the infrared spectrum of the coating. The coating can include a single component or can be a plural-component coating.

While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for analyzing a plural-component coating formed by applying two or more components to a surface, the coating having a ratio of components, the method comprising determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications.

2. A method for analyzing a surface coating, comprising: applying two or more components to a surface to provide a plural-component coating having a ratio of components; and determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications.

3. The methods of Claims 1 or 2, wherein determining whether the ratio is within predetermined limits comprises measuring at least a portion of the infrared spectrum of the coating.

4. The method of Claim 3, wherein the infrared spectrum provides spectral data that allows for the determination of ratio of the components.

5. The methods of Claims 1 or 2, wherein the surface is a surface to be coated by a plural-component coating.

6. The methods of Claims 1 or 2, wherein the surface is a surrogate surface.

7. The method of Claim 6, wherein the surrogate surface is a coupon.

8. The methods of Claims 1 or 2, wherein the components comprise at least one of a polyurethane component, polyurea component, vinyl ester component, and epoxy component.

9. The method of Claim 4, wherein the spectral data is acquired by a filter-based infrared spectrometer.

10. The method of Claim 4, wherein the spectral data includes data for the isocyanate band.

11. A device for performing the methods of any one of Claims 1 - 10.

12. The device of Claim 1 1, wherein the device is a filter-based infrared spectrometer.

13. A method for testing equipment for use in surface coating, comprising the method of Claim 2.

14. A method for analyzing a plural-component coating formed by applying two or more components to a surface, the coating having a ratio of components, the method comprising: measuring at least a portion of the infrared spectrum of the coating to obtain spectral data, wherein the spectral data provides information that allows for the determination of the ratio; and determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications.

15. A method for analyzing a surface coating, comprising: applying two or more components to a surface to provide a plural-component coating having a ratio of components; measuring at least a portion of the infrared spectrum of the coating to obtain spectral data, wherein the spectral data provides information that allows for the determination of the ratio; and determining whether the ratio is within predetermined limits to provide a surface coating meeting desired specifications.

16. The methods of Claims 14 or 15, wherein the surface is a surface to be coated by a plural-component coating.

17. The methods of Claims 14 or 15, wherein the surface is a surrogate surface.

18. The method of Claim 11, wherein the surrogate surface is a coupon.

19. The methods of Claims 14 or 15, wherein the components comprise at least one of a polyurethane component, polyurea component, vinyl ester component, and epoxy component.

20. The methods of Claims 14 or 15, wherein the spectral data is acquired by an infrared spectrometer.

21. The methods of Claims 14 or 15, wherein the spectral data is acquired by an infrared spectrometer equipped with an attenuated total reflectance attachment.

22. The methods of Claims 14 or 15, wherein the spectral data is acquired by a filter-based infrared spectrometer.

23. The methods of Claims 14 or 15, wherein the spectral data includes data for the isocyanate band.

24. A device for performing the methods of any one of Claims 14 - 23.

25. The device of Claim 24, wherein the device is a filter-based infrared spectrometer.

26. A method for testing equipment for use in surface coating, comprising the method of Claim 14.

27. A method for determining the homogeneity of a surface coating, comprising: obtaining spectral data for a surface coating at a first location on the coating; obtaining spectral data for the surface coating at a second location on the coating, wherein the first and second locations are different locations, and wherein the spectral data comprises at least a portion of the infrared spectrum of the coating; and comparing the spectral data obtained from the first and second locations to determine whether the coating is homogeneous within predetermined limits to provide a surface coating meeting desired specifications.

28. The method of Claim 27, wherein the coating comprises a single component.

29. The method of Claim 27, wherein the coating comprises two or more components.

30. The methods of Claims 28 or 29, wherein the components comprise at least on of a polyurethane component, polyurea component, vinyl ester component, and epoxy component.

31. The method of Claim 27, wherein the spectral data is acquired by an infrared spectrometer.

32. The method of Claim 27, wherein the spectral data is acquired by an infrared spectrometer equipped with an attenuated total reflectance attachment.

33. The method of Claim 27, wherein the spectral data is acquired by a filter-based infrared spectrometer.

34. The method of Claim 27, wherein the spectral data includes data for the isocyanate band.

35. A device for performing the method of Claim 27.

36. The device of Claim 35, wherein the device is a filter-based infrared spectrometer.

37. The methods of any of Claims 1, 2, 13, 14, 15, 26, or 27, wherein the method is an on-site method.