Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
2000-08-30
2002-02-19
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyester
C525S031000, C525S041000, C525S043000, C525S044000, C525S168000, C525S438000, C525S445000, C524S424000, C524S442000
Reexamination Certificate
active
06348270
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to resin compositions for use in laminating applications.
BACKGROUND OF THE INVENTION
Polyetherester resins are a relatively new type of thermosetting resins being considered for use in a number of applications that have traditionally employed polyester and vinyl ester resins. Such applications include products for use in marine, transportation, and building industries, corrosion resistant products, as well as fiber or particulate reinforced products such as glass fiber reinforced laminate-type products.
Examples of processes for making polyetheresters are described in U.S. Pat. Nos. 5,319,006; 5,436,313; and 5,436,314. By adjusting the proportion of anhydride to polyol, the average polyether chain length between ester linkages and the crosslinkability of the polyester ether can be controlled. The viscosity and styrene content of a polyetherester resin are generally lower in comparison to conventional polyester resins containing isophthalic and terephthalic acids.
Notwithstanding any of the above efforts, physical properties of the polyetherester resins are typically not acceptable. Cured polyetherester thermoset resins often exhibit poor heat deflection temperatures under load (HDT), poor tensile and flex properties, and, more importantly, poor water resistance properties. Although not wishing to be bound by any theory, it is believed that these inferior properties are attributable to the fact that the polyetherester resins typically contain a high concentration of flexible and somewhat hydrophilic polyether linkages and a relatively low amount of rigid and hydrophobic aromatic ring structures on the polymer chain.
In view of the above, several attempts have been proposed to incorporate aromatic structures into the polyetheresters, typically by employing isophthalic acid. Examples of these attempts are described in U.S. Pat. Nos. 5,569,737; 5,610,205; 5,436,314; and 5,612,444. In spite of any potential benefits, there are several drawbacks to these processes. For example, it is often difficult to achieve a high reaction conversion. Moreover, it is difficult to obtain a resin having a low acid number (i.e., less than 30). A resin having a high acid number and a sizeable amount of carboxylic acid end groups can cause the cured resin to be excessively water sensitive and thus deteriorate quickly in aqueous or caustic conditions. It is believed that in order to potentially obtain a desirable balance of reactivity and physical properties, a relatively large amount of saturated aromatic esters should be incorporated in the polyetherester polymer chain. However, employing such aromatic groups often results in an increase in resin viscosity. Moreover, the tensile and flex properties and the heat distortion temperatures of the cured thermosets having aromatic groups are typically lower relative to a conventional polyester formed from isophthalic acid.
Attempts at reducing the acid number and improving the performance of the polyetherester resins have been proposed in U.S. Pat. Nos. 696,225 and 5,770,659. These patents generally propose methods of making polyetherester resins via chain extension of the polyetherester intermediate with a primary diol or an epoxy resin. These efforts, however, also suffer from potential drawbacks. For example, the molecular weight and thus the viscosity of the final resin typically increases dramatically as a result of the chain extension requiring higher levels of diluents to decrease such viscosities. These resins, and especially epoxy-modified polyetheresters, are thought to be particularly undesirable for VOC applications. Moreover, in order to reduce the resin acid number to below 30 and obtain adequate physical and chemical resistant properties, a relatively large quantity of epoxy is needed, typically more than 20 weight percent. Because such an epoxy is typically a very expensive raw material, this approach may not be attractive from a cost standpoint.
Other methods of forming modified polyetherester resins are proposed in U.S. Pat. Nos. 5,684,086 and 5,780,558. These references propose reacting dicyclopentadiene (DCPD) into the polymer backbone or blending DCPD with a polyetherester resin. This proposed technique is potentially a more cost effective technique at providing cured thermoset resins with improved strength properties. Nonetheless, these resins potentially display other inferior properties, particularly with respect to chemical resistance. The problems with these resins may be attributable to both DCPD and polyetherester resins exhibiting poor chemical resistance. Moreover, since a high level of DCPD resin is typically needed to provide adequate blend performance, an excess of DCPD may result in a thermoset resin that is very brittle.
In view of the above, there is a need in the art for a more cost-effective laminating resin that employs a reduced level of ethylenically unsaturated monomer (e.g., styrene) while displaying a desirable range of physical properties, particularly with respect to strength and chemical resistance.
SUMMARY OF THE INVENTION
In response to the above need and others, the present invention provides a polyetherester-based laminating resin composition. The composition comprises an unsaturated polyetherester resin and an epoxy acrylate oligomer. Advantageously, the composition comprises no greater than about 35 percent by weight of ethylenically unsaturated monomer while providing good physical properties particularly with respect to strength, toughness, and corrosion resistance.
The invention also provides an article of manufacture. The article of manufacture comprises the laminating resin composition and a fibrous substrate.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The invention will now be described in greater detail with respect to the preferred embodiments set forth herein below. It should be appreciated however that these embodiments are for illustrative purposes only, and that the scope of the invention is defined by the claims.
In one aspect, the invention relates to a polyetherester-based or—containing laminating resin composition. The laminating resin composition comprises an unsaturated polyetherester resin and an epoxy acrylate oligomer. The laminating resin comprises no greater than about 35 percent by weight of ethylenically unsaturated monomer. The laminating resin composition is thermosettable. The components of the laminating resin composition are preferably present in the form of a blend or mixture.
Any number of polyetherester resins may be used in the composition of the invention. Examples of unsaturated polyetherester resins and methods of making these materials are set forth in U.S. Pat. Nos. 5,696,225; 5,677,396; 5,436,313; and 5,319,006, the disclosures of which are incorporated herein by reference in their entirety. As an illustration, a polyetherester may be formed from a polyether reacting with an anhydride in the presence of a catalyst such as, for example, a protic acid or a metal salt of a protic acid, or a Lewis acid, in an amount suitable to promote insertion of the anhydride into the carbon-oxygen double bonds of the polyether to produce a polyetherester.
Polyethers suitable for use in the invention are preferably those derived from base or acid-catalyzed ring-opening polymerization of cyclic ethers such as epoxides, oxetanes, oxolanes, and the like. The polyethers have repeat units of oxyalkylene groups (—O—A—) in which A preferably has from 2 to 10 carbon atoms, more preferably 2 to 4 carbon atoms. The polyethers can have different end groups, depending upon how the polyethers are made or modified. For example, the polyether can have hydroxyl, ester, ether acid, olefinic, or amino end groups, or the like, or combinations of these. Mixtures of different types of polyethers can be used.
Preferred polyethers are polyether polyols. Examples of polyether polyols include, but are not limited to, polyoxypropylene polyols, polyoxyethylene polyols, ethylene oxide-propylene oxide copolymers, polytetramethylene ether glycols
Jin Lixin
Nava Hildeberto
Acquah Samuel A.
Myers Bigel & Sibley & Sajovec
Reichhold Inc.
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