Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-02-06
2004-07-27
Wyrozebski, Katarzyna (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S495000, C525S049000, C525S048000, C525S935000
Reexamination Certificate
active
06767950
ABSTRACT:
TECHNICAL FIELD
This invention relates to pigmented molding compositions. In a more specific aspect, this invention relates to pigmented molding compositions which have good weatherability. This invention also relates to a process for the manufacture of these compositions.
BACKGROUND OF THE INVENTION
Molding compositions have been manufactured and used for many years in forming various articles. Examples of these compositions include sheet molding compounds (SMC) and bulk molding compounds (BMC).
In many instances, pigments are added to molding compositions to achieve particular effects. These pigments are commonly added in either pure form or in the form of a dispersion (also referred to as a pigment paste). A typical pigment paste comprises pigment particles dispersed in a suitable carrier resin. Examples of suitable carrier resins are unsaturated polyesters having a low viscosity, such as described in U.S. Pat. No. 4,009,225, and polystyrene resins having oxazoline groups, such as described in European Patent Publication No. 272,127.
Pigment pastes are frequently used because of the difficulty under normal manufacturing conditions of dispersing pigment particles in a uniform manner into other substances, such as directly into molding compositions.
The prior art in this industry contains many disclosures of molding compositions and the improvements obtained with these compositions. For example, U.S. Pat. No. 5,326,516 describes a method of preparing a cured pigmented thermosetting polymer molding composition which exhibits improved color value and reduced haze. Styrene is described as an effective monomer, and the pigment is mixed into a thermoplastic polymer that has a similar refractive index to the thermosetting polymer.
U.S. Pat. No. 5,443,775 describes a process for preparing thermoplastic polymer compositions and low shrinking thermosetting resin molding compositions.
European Patent Publication No. 0 572 851 describes formulations for sheet molding compounds in which the resin component contains an unsaturated polyester resin, a thermoplastic polymer (such as polyethylene) and an acrylic monomer. Calcium carbonate is disclosed as a filler. However, these formulations are made with beads or powder extruded from a melt containing both the unsaturated polyester resin and a polyethylene-based low profile additive.
European Patent Publication No. 0 783 026 describes the use of an end-capped unsaturated polyester resin in monomer-free sheet and bulk molding compounds. Thermoplastic polymers may be present in these compositions.
U.S. Pat. No. 5,747,553 describes low pressure acrylic molding compositions reinforced with fibers. This patent discloses resins with acrylic backbones for dental applications. Silica, feldspar and quartz are disclosed as fillers.
U.S. Pat. No. 5,948,849 describes top-coat weatherable systems for stained composite thermosetting or thermoplastic surface building products.
One problem which is continually encountered by the prior art pigmented molding compositions is that of weatherability. (The term “weatherability” as used in this application refers to the stability of a molded article to environmental factors, such as humidity, ultraviolet radiation, temperature, etc.) As will be recognized by those having skill in this art, the pigmented molded articles with good weatherability have distinct advantages over equivalent articles but which lack good weatherability.
For various reasons, the prior art pigmented molding compositions fail to provide articles having the weatherability which is desired and even essential for many uses. Thus, there is a need in the industry for pigmented molding compositions which have good weatherability.
SUMMARY OF THE INVENTION
Briefly described, the present invention provides pigmented, weatherable molding compositions for sheet and bulk molded articles. The present invention also provides a process for the manufacture of these compositions.
As will be seen in greater detail below, the pigmented molding compositions of this invention provide articles with good weatherability. These articles do not need to be clear-coated or painted to achieve good weatherability.
Accordingly, an object of this invention is to provide a pigmented molding composition for sheet molding applications.
Another object of this invention is to provide a pigmented molding composition for bulk molding applications.
Another object of this invention is to provide a pigmented, weatherable molding composition for sheet molding applications.
Another object of this invention is to provide a pigmented, weatherable molding composition for bulk molding applications.
Still another object of this invention is to provide a pigmented, weatherable molded sheet having improved gloss and color retention when exposed to environmental conditions such as humidity, ultraviolet radiation and temperature.
Still another object of this invention is to provide a pigmented, weatherable molded bulk part having improved gloss and color retention when exposed to environmental conditions such as humidity, ultraviolet radiation and temperature.
Yet still another object of this invention is to provide a process for the manufacture of a pigmented molding composition having good weatherability.
Yet still another object of this invention is to provide a process for the manufacture of a pigmented molding composition having good weatherability and which is useful in sheet molding and bulk molding applications.
These and other objects, features and advantages of this invention will become apparent from the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a pigmented, weatherable molding composition comprising a resin component which comprises an unsaturated polyester, a monomer which will react with the polyester and a non-aromatic, thermoplastic polymer; an ultraviolet light absorbing material and/or a hindered amine light stabilizing material; a pigment; and a reinforcing agent.
The present invention also relates to a process for the manufacture of a pigmented, weatherable molding composition, wherein process comprises the steps of mixing a resin component which comprises an unsaturated polyester, a monomer which will react with the polyester and a non-aromatic, thermoplastic polymer; an ultraviolet light absorbing material and/or a hindered amine light stabilizing material; a pigment; and a reinforcing agent.
The molding compositions of this invention can be molded into various articles, including sheets and bulk parts, such as automotive bumpers, truck beds, fenders, etc.
The molding compositions of this invention have good weatherability because they resist the damaging effects of humidity, ultraviolet radiation and temperature. By having good weatherability, the molding compositions of this invention are prime candidates for various molded-in-color applications.
For purpose of this application, good weatherability (which may also be referred to as environmental stability) is determined by gloss and color retention. Gloss readings are taken at 20, 60 and 85 degrees and averaged from about 5 readings. In this industry, the gloss at the 60 degree reading is generally reported in weather testing. As a direct result of having good weatherability, the articles made from the molding compositions of this invention are not required to be clear-coated and/or painted, which are common practices in this industry.
The molding compositions of this invention have good weatherability due to the careful selection of the components which are contained in these compositions. The unsaturated part of the resin component does not contain a significant amount of any aromatic compounds such as orthophthalic acid, isophthalic acid, terephthalic acid, etc. which are well known to cause yellowing when exposed to sunlight for long periods of time. Preferably, the resin component does not contain any aromatic compounds.
As noted above, the molding compositions of this invention contain a resin component which comprises an unsaturated polyester, a monomer
Folda Thomas J.
Harber Mark S.
Steinhäusler Thomas
Walrath Robert M.
Young John J.
AOC, L.L.C.
Baker Donelson Bearman Caldwell & Berkowitz
Wyrozebski Katarzyna
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