Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-08-28
2004-12-28
Berman, Susan (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S099000, C522S100000, C522S090000, C522S114000, C522S135000, C522S173000, C522S179000, C522S182000
Reexamination Certificate
active
06835759
ABSTRACT:
BACKGROUND OF THE INVENTION
(1.) Field of the Invention
The invention relates to coating compositions that are curable upon exposure to both electromagnetic radiation and heat energy as well as methods of using such dual cure coating compositions. More particularly, the invention relates to methods of making coated porous substrates that are substantially free of surface defects caused by vaporous emissions from the substrate.
(2.) Background Art
Porous materials are used in a wide variety of applications. Porous as used herein refers to materials or substrates having one or more microporous surfaces with pore diameters of from 10 to 1500 nm. Examples of porous materials include wood, glass, leather, plastics, metals, mineral substances, fiber materials, and fiber reinforced materials.
Porous materials which are especially useful in the production of shaped and/or molded articles or components are plastics; mineral substances such as fired and unfired clay, ceramics, natural and artificial stone or cement; fiber materials especially glass fibers, ceramic fibers, carbon fibers, textile fibers, metal fibers, and composites thereof; fiber reinforced materials, especially plastic composites reinforced with one or more of the aforementioned fibers; and mixtures thereof Examples of preferred porous materials for the production of shaped and/or molded articles are reinforced reaction injection molded compound (RRIM), structural reaction injection molded compound (SRIM), nylon composites, fiber reinforced sheet molded compounds (SMC) and fiber reinforced bulk molded compounds (BMC). SMC and BMC are most preferred porous substrates.
SMC and BMC have been found to be especially useful in the production of shaped articles having challenging contours and/or configurations. Compared to steel and thermoplastics, composites offer numerous advantages. They provide a favorable weight to strength ratio, consolidate multiple piece components, reduce tooling costs, provide improved dent and corrosion resistance, moderate process cycle times, reduced cost of design changes, as well as moderate material cost. SMC and BMC have been used in the manufacture of domestic appliances, automotive components, structural components and the like.
In many instances, it is desirable to apply one or more coating compositions to the surface of the shaped porous article. Coatings may be designed to provide effects which are visual, protective, or both. However, the production of coated shaped porous articles, especially articles of SMC or BMC, continues to present challenges.
Many shaped articles made of SMC or BMC have one or more sections in which it is more difficult to obtain a fully cured film. For example, some shaped articles contain areas of greater thickness that can function as heat sinks. This can result in lower effective surface temperatures that impede the cure of thermally curable coatings applied in that area.
Efforts to use coatings curable solely with the use of actinic radiation have encountered other problems. Actinic radiation as used herein refers to electromagnetic radiation such as UV radiation or X-rays, as well as to corpuscular radiation such as electron beams. The unique contours and configurations of many shaped porous articles result in three-dimensional articles having ‘shadow’ zones or areas that are obscured from direct irradiance from the chosen energy source. Thus, the use of coatings cured via actinic energy sources can result in uncured or partially cured coating films in those shadow areas not visible to one or more of the energy sources. Alternatively, increased expense may be incurred due to the procurement of additional actinic energy sources in an effort to ‘reach’ all shadow areas. It will be appreciated that in many instances, manufacturing constraints will limit the number and/or location of actinic energy sources. Also, in many cases the overspray does not cure due to oxygen inhibition caused by the large surface area ratio of the particle and any dispersed oxygen within the particle.
Another significant problem encountered in the coating of porous substrates is the persistent appearance of surface defects, especially those resulting from outgassing or vaporous emissions from the substrate. Often referred to as porosity, popping or blistering, such defects significantly reduce first run capability, capacity and quality while increasing process and operational costs. Porosity is apparent after the primer or topcoating process. It may appear in the topcoat without any visible defects in the primer. It can be extremely sporadic and unpredictable. The root cause of porosity is generally accepted to be the evolution of gases from the substrate during the curing process. The elevated temperatures cause entrapped gases and by-products to expand through the paint films. As these gases escape, they cause eruptions or bubbles in the paint film. The final defect appears as a full dome or the residue from a deflated bubble. Unfortunately, the presence of even a few such porosity defects can result in the rejection of the coated article. Thus, manufacturers of coated porous surfaces have long sought methods capable of consistently producing high quantities of defect-free coated surfaces having optimum smoothness. Methods capable of substantially eliminating porosity defects are especially desired.
In addition, applied coatings must have good adhesion to the underlying porous substrate and be overcoatable with one or more subsequently applied coatings. The failure of an applied, cured film to either the underlying substrate and/or to one or more subsequently applied coatings is referred to herein as an intercoat adhesion (ICA) failure. Coatings vulnerable to adhesion failures are commercially unacceptable, especially to the automotive industry.
Adhesion can be particularly challenging when a coated plastic substrate becomes part of an article that is subsequently subjected to the electrocoat process. In some manufacturing facilities, it is desirable for coated porous shaped articles of SMC/BMC to be affixed to metal structure prior to their submersion in an e-coat bath. After exiting from the bath, the entire structure is subjected to conditions sufficient to effect complete crosslinking of the electrodeposition coating where present. Although the coated shaped article of SMC/BMC will generally not be coated during this process, it is desirable that the electrodeposition bake not affect the overcoatability of any coatings applied prior to the electrodeposition bake. In particular, any coatings applied to the substrate before the electrodeposition bake must continue to exhibit desirable adhesion with regards to subsequently applied primers, basecoats, and/or clearcoats.
In addition to optimum adhesion, coatings intended to correct porosity defects must also exhibit desirable weatherability, durability, humidity resistance, smoothness, and the like. In particular, coatings intended to eliminate outgassing defects must continue to exhibit optimum adhesion in thermal shock tests, cold gravel tests and after weathering tests such as Florida exposure, QUV, WOM or field use.
Although the prior art has attempted to address these issues, deficiencies remain.
German Patent Application DE 199 20 799 provides a coating composition curable both thermally and with actinic radiation. The composition comprises at least one constituent (a1) containing at least two functional groups (a11) which serve for crosslinking with actinic radiation and if desired, at least two functional groups (a12), which are able to undergo thermal crosslinking reactions with a complementary functional group (a22) in component (a2). Examples of functional groups (all) and (a12) are respectively acrylate groups and hydroxyl groups. The composition further comprises at least one component (a2) containing at least two functional groups (a21) which serve for crosslinking with actinic radiation, and at least one functional group (a22) which is able to undergo thermal crosslinking reactions with complementary functional group (
Bradford Christopher J.
Caillouette Lyle
O'Donnell Ryan F.
Rischke Jennifer A.
Zimmer Marcy
BASF Corporation
Berman Susan
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