Patent Application
20110118387
The present invention relates to a sealer for use in vehicle production. More particularly, the present invention relates to a heat curable PVC-free material having a relatively long shelf life for use in sealing vehicles including, automobiles, buses, trucks and other applications requiring excellent adhesion to e-coated substrates, high exterior weather resistance, abrasion resistance and chip resistance.
The use of PVC-based bulk materials and components in the construction of vehicles is well known. Polyvinyl chloride resins, suspension, dispersion or emulsion grades are commonly dispersed in liquid plasticizers (with other additives) to form a plastisol. The plastisol composition is thermoplastic and requires heat and time for fusion. Materials which use PVC have proven cost effective in production and resilient in use.
However, for all of their recognized advantages, the production and use of PVC-based materials also carry noteworthy disadvantages. For example, current PVC plastisols have a shelf life of between 60 and 90 days due to their inherent gelling mechanism. This is because PVC plastisols are formed through the fusion of PVC and the plasticizer, an event that occurs rapidly at an elevated temperature but nevertheless proceeds more slowly at room temperature. Furthermore, PVC-based plastisols are alleged to present challenges to our environment and health. Environmental concern starts with the production of PVC, wherein the precursor monomer, vinyl chloride, a volatile, toxic gas is released to the atmosphere and also concerns have risen regarding the recycling or incineration of PVC-based materials. During incineration, toxic hydrochloric acid is released, resulting in acid rain and smog. Another component of PVC plastisols that is a concern for the environment is the plasticizer component. Some common plasticizers used in PVC plastisols are being banned globally due to their ability to mimic hormones in the human body, especially young children.
Certain steps have been taken to overcome the deficiencies of PVC-based components and bulk materials by replacing them with products having similar cost and performance characteristics but which do not rely upon PVC as a component. Such efforts include the use of acrylic chemistry with urethane or polyamide adhesion promoters. The use of prepolymers of urethanes and epoxy resins is also known. However, such materials are too high in viscosity to process in paint shop materials. Accordingly, it is desirable to produce a PVC-free composition having application in many areas of vehicle production, particularly in the areas of vehicle sealing and damping.
According to one embodiment of the present invention, there is provided a composition adapted for use as a sealer comprising a urethane component. The composition further comprises an epoxy component. Additionally, the composition comprises a curing agent component and a catalyst component.
According to a second embodiment of the present invention, there is provided a composition adapted for use as a sealer comprising a blocked urethane component in the range of between about 11% and about 22% by weight. The composition further comprises an epoxy component in the range of between about 5% and about 15% by weight. A powdered acrylic component is provided in the range of between about 5% and about 25% by weight. The composition further comprises a powdered amine component in the range of between about 0.1% and about 5% by weight.
The present invention provides a PVC-free sealer that finds broad and versatile application as a sealer. The invention is particularly useful in the automotive sector. Preferably, the sealer is a one-component, PVC-free plastisol embodied in a hybrid epoxy-urethane composition. Alternatively, the sealer may be embodied in a hybrid epoxy-urethane-acrylic composition. Sealer application could include most, if not all paint shop and body shop applications. Nevertheless, the present compositions are particularly useful in high temperature baking applications such as those employed in automotive paint shop conditions. Given the versatility of the present compositions, application could be had in many areas of vehicle production, generally in the areas of vehicle sealing and damping. More particular applications would be in the form of paint shop seam sealers, underbody coatings, anti-chip coatings, roof ditch sealer and body shop sealers.
The composition of the present invention preferably comprises a urethane component, an epoxy component, a curing agent and a catalyst. Additionally, the composition preferably comprises a plasticizer and a solvent. Various fillers and additives may also be used.
The preferred composition includes blocked urethane prepolymers. The urethane prepolymer including polyester and polyether polyols and isocyanates (including toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI)) may be selected for the present composition. Curing agents including amines in powder form are preferred. Catalysts may be used and would preferably include any suitable catalyst in powder form. Such preferred catalyst include urea adducts. Preferred plasticizers include any of the phthalate ester types. Fillers may also be used to improve strength and resiliency. Where the composition includes an acrylic to improve physical properties, such acrylic is preferably in the form of powder.
In general, the epoxy-urethane or epoxy-urethane-acrylic compositions of the present invention demonstrate improved mechanical properties such as better lap shear strength, elongation, low temperature flexibility, and improved adhesion. Use of the compositions of the present invention lower production cost and virtually eliminates environmental impact issues. Both of these considerable advantages can be achieved while effecting high performance.
The compositions of the present invention also demonstrate greater mechanical and physical property design flexibility through use of urethane backbone. Compared with known urethane-acrylic technology, the overall improvement of the present invention over known compositions is illustrated by better general material performance and superior adhesion to a great variety of substrates. Improvements also recognized include improved low-temperature performance such as improved flexibility. Accordingly, the composition of the present invention reduces the need for an additional adhesion promoter in the formula compared to known technology.
According to the present invention, two compositions are preferred, a urethane-epoxy hybrid, and a urethane-epoxy-acrylic hybrid. In each preferred composition, an amine in powder form is utilized as a curing agent.
Thus, the compositions may be based on either a urethane-epoxy system or on a urethane-epoxy-acrylic powder system. Amines are used to cure the liquid or solid epoxy resin and urethane mixture. The reactive components (the epoxy and the urethane) cross link into one molecular network at an elevated temperature. Conversely, known PVC-based plastisols only fuse when heated.
The principle composition elements are set forth hereinafter.
A variety of blocked urethane prepolymers may be used in the present composition, including urethane prepolymer prepared from polyester or polyether polyols and isocynates such as TDI, MDI, HDI, or IPDI and blocking agents including methylethylketoxime (MEKO) or others known to those skilled in the art. The blocked urethane prepolymer is preferably provided in an approximate amount of between about 10% and about 40% by weight. More preferably, the blocked urethane prepolymer is provided in an approximate amount of between about 11% and about 22% by weight.
The particular epoxy is preferably selected from solid epoxy powders or liquids including reaction products of bisphenol-A and epichlorohydrin-based epoxy resins having a degree of polymerization of N=1 or greater. As a further alternative, aliphatic epoxy resins may also be used, however, such resins are generally more expensive and result in a less desirable hydrophilic system.
Suitable epoxies include DER 354, DER 331 and DER 662, all commercially available from The Dow Chemical Company.
The epoxy is preferably provided in an approximate amount of between about 5% and about 25% by weight. More preferably, the epoxy is provided in an approximate amount of between about 5% and about 15% by weight
A variety of curing agents in powder form may be used. It is preferred that the curing agents comprise amines. Suitable curing agents include Dicyandiamide (dicy), Adipic Dihyrazide (ADH), ANCAMINE 2014AS, ANCAMINE 2014FG, ANCAMINE 2337S, ANCAMINE 2441 and ANCAMINE 2442 may be used. Ancamine products are commercially available from Air Products and Chemicals, Inc. It is preferred that curing agents in powder form are used. Liquid curing agents such as liquid amines tend to be highly reactive at room temperature and less useful in the present invention. The curing agent is preferably provided in an approximate amount of between about 0.1% and about 10% by weight.
Any suitable catalyst may be used. Again, catalysts in powder form are preferred. Catalysts such as urea adducts of the type used in one-component epoxy resin systems are preferred. The catalyst is preferably provided in an approximate amount of between about 0.1% and about 5% by weight.
It will be appreciated that certain compounds may act as both a catalyst and a curing agent as set forth in the examples below.
The plasticizer may be of any of the phthalate ester types such as Di-Isononylphthlate (DINP), Di-Isodecylphthlate (DIDP) or Palatinol® from BASF Corporation and may be of any type known to those skilled in the art of polyurethane elastomer formulations. The plasticizer is preferably provided in an approximate amount of between about 16% and about 50% by weight and more preferably, in an approximate amount of between about 16% and about 30% by weight.
Fillers are used, inter alia, to control rheology and to improve tensile strength, modulus strength, and sheer strength. In addition, fillers are used to improve abrasion resistance and to lower cost. Preferably, the fillers may be drawn from the group comprising of low cost calcium carbonated (treated PCC or ground), mica, talc, dolomite, clay, and carbon black. Other suitable cost lowering and rheology-controlling fillers can be used. The filler is preferably provided in an approximate amount of between about 25% and about 60% by weight. More preferably, the filler is provided in an approximate amount of between about 28% and about 40% by weight.
Optional additives such as acrylic powders may be used in the present composition to provide known advantages. Acrylic powders are preferred and may be selected to provide physical strength. The acrylic powder, when used, is preferably provided in an approximate amount between about 5% and about 25% by weight. Other suitable additives may be used and, more preferably, in an approximate amount of between about 15% and about 20% by weight.
Suitable solvents may be used within the scope of the present invention. Preferably, odorless mineral spirits (OMS) is used as the solvent. Solvents may be present in an approximate amount of between about 1% and about 10% by weight and most preferably in an approximate amount of between about 4% and about 5% by weight.
The process of the present invention is illustrated by the following practical examples and comparative testing. All parts and percentages are by weight unless otherwise specified.
The table below shows both the composition elements for a urethane-epoxy composition according to the present invention. The described composition is directed to use preferably as a roof ditch sealer for paint shop. The composition utilizes a liquid epoxy.
The press flow is an indication of the viscosity of the fluid. The press flow is the amount of time needed to press 20 g of material through an orifice. The pressure is processing parameters for the gun bar. Model RVT, Brookfield Viscometer is used to measure the material viscosity at low shear in the present invention. RVT numbers are parameters for material reology control.
The following procedure illustrates the steps for forming the roof ditch sealer set forth above according to the present invention. The procedure utilizes the components and weight percentages specified above in the above Practical Example. Each step of the processing procedure is carried out at ambient temperature.
The table below shows both the composition elements as well as comparative test results for a urethane-acrylic-epoxy composition according to the present invention. The described composition is directed to use preferably as a roof ditch sealer. The composition utilizes a liquid epoxy.
This sample was mixed and cured as set forth above in connection with the first sample. The lapshear strength was tested until there was a failure. The failure indicated was coheshion failure and not adhesion failure.
Practical Example And Comparative Testing—Seam Sealer—Solid Epoxy (Urethane-Epoxy-Acrylic)
The table below shows both the composition elements as well as comparative test results for a urethane-acrylic-epoxy composition according to the present invention. The described composition is directed to use preferably as a seam sealer. The composition utilizes a solid epoxy.
This sample was mixed and cured as set forth above in connection with the first sample. The lapshear strength was tested until there was a failure. The failure indicated was coheshion failure and not adhesion failure.
Additionally, the composition was aged for 10 days at 35 ° C. The RVT and press flow of the initial and aged samples are shown.
The table below shows both the composition elements as well as comparative test results for a urethane-acrylic-epoxy composition according to the present invention. The described composition is directed to use preferably as a seam sealer. The composition utilizes a liquid epoxy.
This sample was mixed and cured as set forth above in connection with the first sample. The lapshear strength was tested until there was a failure. The failure indicated was cohesion failure and not adhesion failure.
Additionally, the composition was aged for 10 days at 35° C. The RVT and press flow of the initial and aged samples are shown.
General test results of the PVC-free plastisols of the present invention demonstrate excellent physical performance after curing in conventional bake ovens. These good characteristics include improved physical strength, elongation, sealing/bridging, and storage stability. Additional positive characteristics include improved adhesion to e-coated substrates and good compatibility with primer and top coatings.
The compositions of the present invention also demonstrate improved rheological properties when compared with the prior art. Specifically, the rheological properties of compositions formed according to the teachings of the present invention are more consistent over the shelf life of the product and, accordingly, application of the product will be more consistent over the shelf life of the product. Because the epoxy-urethane hybrid of the present invention requires a relatively high activation temperature (>250° F.) to initiate curing the compositions of the present invention are not limited to the 60 to 90 day shelf life of known compositions.
It is understood that the above are merely preferred embodiments and that various changes and alterations can be made without departing from the spirit and broader aspects of the invention.
This application is a continuation of U.S. application Ser. No. 11/138,541 filed May 26, 2005, the entire contents of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11138541 | May 2005 | US |
| Child | 13014586 | US |
