Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-07-31
2004-08-24
Zalukaeva, Tatyana (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S274000, C528S275000, C528S278000, C528S280000, C528S281000, C525S437000, C525S451000, C525S048000, C521S048000
Reexamination Certificate
active
06780962
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to low-cost (meth)acrylic ester binders and such binder comprising compositions, the synthesis of such binders starting from polyesters such as polyethylene terephthalate (PET), and their application in reactive acrylic systems, particularly in adhesives, coatings and floorings.
(2) Description of the Related Art
The use of polyesters, in particular PET, in film and fiber applications has increased drastically in the past several years. According to the Sherwin-Williams patent U.S. Pat. No. 5,252,615, PET accounted for about 20% by volume of the world's solid waste in 1993. A large amount of scrap and waste materials is still resulting from the production and consumption of PET every year and therefore, processes which can make use of recycled PET are economically interesting. Taking into account that environmental care and ecological balance have a high priority for the chemical industry today, the conversion of PET waste and scraps into usable raw materials is a continuous challenge. Besides reducing waste, the use of recycled plastics contributes also to the ecological compatibility of commercial products.
Several methods have been developed for converting PET into aromatic polyester polyols, which are valuable, and low-cost raw materials for the production of adhesive, coating and flooring compositions.
Adhesives, coatings and floorings have to fulfill several requirements in order to be considered for industrial applications. Preferably, the compositions should combine a long open time with a fast curing speed. The cured systems should exhibit good mechanical and adhesive properties, besides high weather and chemical resistance. However, not only the technical requirements but also the economical aspects determine the choice of adhesives, coatings and floorings for industrial applications. The price of a composition depends mainly on the costs of its reactive components, therefore, it is important to reduce the costs of said reactive components as much as possible. Processes, which make use of inexpensive starting materials such as PET, allow the production of low-cost components for adhesives, coatings and flooring compositions.
For industrial applications of such compositions, high speed in curing, especially at room temperature, is advantageous, particularly in manufacturing operations where it is expensive to wait until the systems are fully cured. Consequently, compositions with a high curing speed and enough long open time to allow application are desired. One class of systems, which can be adapted more readily to fit these requirements, is the class of polymerizable acrylate based systems. Acrylic compositions that cure according to a free radical polymerization mechanism reach final strength within minutes at room temperature. This fast strength build-up confers acrylic compositions advantages in comparison to compositions based on epoxies and urethanes which need several hours to reach the same grade of strength.
Methyl methacrylate (MMA) is the most widely used monomer in radically curing acrylic systems. Despite the low cost and excellent properties of this monomer, its strong and disagreeable smell restricts to a great extent its use in adhesive, coating and flooring compositions. All other commercially available low-odor acrylic monomers are expensive, and for that reason novel low-odor/low-cost acrylic monomers, which can be used for acrylic systems, are needed.
Next to the fast curing, acrylic systems are also known for other advantages like high strength and high chemical resistance to acids and alkalines. A disadvantage of the standard acrylic systems is the relatively high shrinkage. Large shrinkage on curing leaves substantial residual stress, which can lead to delamination of a joint. The shrinkage is correlated to the molar mass of the used monomers. For high molar mass oligomers, the relation between the molar mass and the amount of reactive groups is higher, therefore, the shrinkage will be lower. U.S. Pat. No. 3,194,783 describes formulations with high mechanical properties and low shrinkage based on epoxy-acrylates. These oligomers are widely used in compositions for adhesives or floors. But the diacrylate of bisphenol-A diglycidylether is a very high viscous compound, which has to be diluted. The acrylates derived from ethoxylated bisphenol-A diglycidylether have a lower viscosity, but with increasing ethoxylation grade the tensile strength decreases. Moreover, the ethoxylation process is not a simple reaction procedure.
Acrylic compositions, containing cycloaliphatic compounds, with high strength and low shrinkage are described in DE 3 940 138 A1. These cycloaliphatic compounds are unsaturated esters of glycol monodicyclopentenyl ethers and have a low viscosity. But the reaction of dicyclopentadiene with glycols to form this intermediate is very difficult and time consuming.
PU-acrylates, polyurethane prepolymers, which are capped with ethylenically unsaturated end groups, are frequently used in acrylic systems and have a low shrinkage. The moderate-to-long chain prepolymers employed, comprise polyether-urethane or polyester-urethane derivatives formed by reacting a polyether or a polyester polyol with a diisocyanate. Polyether based PU-acrylates have low mechanical properties and temperature resistance. Polyester based PU-acrylates have a high viscosity or are crystalline at room temperature, and show poor compatibility to acrylic monomers.
It is also already known that acrylic ester monomers can be synthesized by direct esterification of (meth)acrylic acid with alcohols in the presence of an acid catalyst, a polymerization inhibitor, and an inert solvent to azeotrope the water formed during reaction. Several syntheses that use polyols as the alcohol component have also been reported. In general, all described processes for the synthesis of acrylic ester monomers from (meth)acrylic acid have the following limitations: 1. use of high cost raw materials and 2. production processes requiring expensive and time consuming reaction work up and product purification.
U.S. Pat. No. 3,645,984 reports the preparation of acrylic ester monomers by reacting a diol with (meth)acrylic acid or their anhydrides or acid chlorides. In EP 0 519 410 A2 aromatic polyether alcohols, prepared from aromatic alcohols and ethylene oxide or propylene oxide, are reacted with (meth)acrylic acid to yield novel acrylic ester monomers. In both patent documents, after the esterification has finished, the unreacted (meth)acrylic acid and catalyst are neutralized and the mixtures are washed several times with aqueous solutions. Then, the inert solvent is removed and the acrylic ester monomers are purified by extraction or distillation to separate them from side products and polymerization inhibitor. Besides being time consuming, the washing steps and (meth)acrylate purification cause considerable product loss decreasing the yield of the process.
EP 0 126 341 A2 and EP 0 921 168 A1 report processes for the synthesis of (meth)acrylic ester monomers by direct esterification of (meth)acrylic acid with polyester and/or polyether alcohols and polyols, and subsequent reaction with epoxies. According to these documents, the washing steps and purification of end products are avoided by reacting with epoxies the (meth)acrylic acid remaining in the mixture after esterification. For this purpose, after the esterification has finished, the inert solvent is removed and the esterification catalyst is neutralized. Then, an epoxy amount corresponding to the equivalent acid content of the mixture is added and the reaction is carried out at about 100° C. in the presence of a suitable catalyst. Though the end products can be obtained in high yields and can be further used without purification, the reaction with epoxies implies an additional process step. The high temperatures needed for the reaction could also lead to polymerization of the synthesized (meth)acrylates. For the reaction with epoxies, the reaction
De Cooman Ria
Meyer Werner
Moya Dally
Burns Doane Swecker & Mathis L.L.P.
Sika Schweiz AG
Zalukaeva Tatyana
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