Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-12-21
2003-11-04
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S013000, C525S014000, C525S017000, C525S027000, C252S186260, C252S186420
Reexamination Certificate
active
06642287
ABSTRACT:
The invention relates to formulations comprising methyl propyl ketone peroxide and the use of methyl propyl ketone peroxide-containing formulations in the process to cure unsaturated polyester resins.
Ketone peroxides and their use as curing agents for unsaturated polyester resins also have long been known. A ketone peroxide is a reaction product of a ketone and hydrogen peroxide and usually is a mixture of products with different structure types. The so-called type-3 and type-4 structures (see below) are most stable and are therefore predominantly present. Most of the ketone peroxides in pure form are hazardous and they need to be phlegmatized to a degree where they are safe to handle and transport, typically at ambient temperature, as mentioned in, for instance, U.S. Pat. No. 3,649,546. The degree of phlegmatization or, in other words, the amount of a phlegmatizer needed, is dependent on the type of ketone peroxide, type of phlegmatizer and the relative weight of the various ketone peroxide types. It has been tried to influence the ratio of the compounds in equilibrium in such a manner that a relatively safe mixture of compounds is formed, one that needs little phlegmatization. U.S. Pat. No. 3,560,395, for example, discloses how to make aqueous methyl ethyl ketone peroxide compositions containing just hydrogen peroxide, a ketone peroxide of formula:
(a so-called type-4 ketone peroxide), and water, which is safe at concentrations of more than 10% active oxygen and gives fast curing of water extended polyester resins. The production and the generic use of predominantly type-4 ethyl amyl ketone peroxide was disclosed in U.S. Pat. No. 3,151,170. This document does not disclose that other types of ketone peroxides solve many of the problems depicted above. U.S. Pat. No. 4,052,465 discloses the use of ketone peroxides consisting essentially of compounds of the formula:
(so-called type-3 ketone peroxides) for the curing of vinyl or vinylidene group-containing polyester resins.
JP-A-10087652 discloses the use of a ketone peroxide composition comprising 13-43% by weight of the type-3 product and 3-22% by weight of the type-4 product. When used to cure unsaturated polyester resins, the compounds are said to give a long gel time and slow cure. Safety properties of peroxides are not discussed. However, such formulations were found not to be safe and the cure of the UP was found to be too slow. Typically, the ketone peroxides exemplified are derived from methyl ethyl ketone and use is made of conventional accelerators, such as Co-octoate.
However, the methyl ethyl ketone peroxides disclosed in the examples of these references show insufficient performance in the curing of gel coats, being thin layers (up to 2 mm in thickness) of unsaturated polyester resin. More specifically, an undesired and very long gel time is observed, resulting in, inter alia, too high styrene emission. Gelation and cure speed can be increased by using higher amounts of peroxide and/or by introduction of cobalt salts, such as cobalt octoate. However, in the conventional systems this leads to unacceptable discoloration of the gel coats. Also, conventional fast curing systems tend to lead to foaming in vinylester resins, which is undesired. Slow cure is a disadvantage in most of the other applications of unsaturated polyester resins too. Moreover, some of the ketone peroxide formulations of the prior art that contain a large amount of type-3 ketone peroxide are not safe. Furthermore, the use of aqueous compositions, as proposed by the prior art, is unacceptable in many applications since i) conventional Co-based accelerators hydrolyze in such systems, leading to unsatisfactory cure characteristics, and ii) aqueous formulations tend to result in undesired foam formation. Hence, there is a clear need for improved ketone peroxide compositions which should give fast cure, do not lead to the hydrolysis of Co-based accelerators, give low discoloration, give no foaming of vinylester resins, and at the same time are safe during transport, storage, and handling, preferably at ambient temperatures.
Surprisingly, we have found that specific ketone peroxide formulations that are derived from methyl propyl ketone and comprise a high amount of type-4 ketone peroxide can be produced safely, especially when use is made of an effective amount of particular (co)solvents, and that the use of these products gives desirable fast curing rates of unsaturated polyester resins, especially in gel coat applications, and that a low level of residual monomer is obtained. Moreover, the products according to the invention can be stored and handled safely at ambient temperatures and solve most, if not all of the other problems.
Accordingly, we claim methyl propyl ketone peroxide formulations comprising: more than 60%, preferably more than 65, more preferably more than 67%, most preferably more than 70% by weight of type-4 methyl propyl ketone peroxide up to 100%, preferably 99, more preferably 98%, most preferably 95% by weight of type-4 methyl propyl ketone peroxide, and preferably comprising, less than 40%, preferably less than 35%, most preferably less than 30%, and preferably more than 1%, more preferably more than 2%, most preferably more than 5% by weight of type-3 methyl propyl ketone peroxide (calculated as the amount of active oxygen of the specified type ketone peroxide based on the total active oxygen of all methyl propyl ketone peroxides in the formulation) and a non-aqueous phlegmatizer in an amount such that the Self Accelerating Decomposition Test (SADT), Dutch Pressure Vessel Test (DPVT) and the Koenen test show safe handling and transport at temperatures of 0-50° C., preferably at temperatures of 10-45° C., most preferably at ambient temperatures of 20-40° C. More preferably, the amount of phlegmatizer is chosen such that the self accelerating decomposition temperature as determined by the SADT is 50° C. or higher, the limiting diameter as determined by the DPVT is <3.5 mm, and the limiting diameter as determined by the Koenen test is 1.0 mm. The tests are of the conventional type as mentioned in the UN Recommendations on the Transport of Dangerous Goods, 11
th
edition (ST/SG/AC.10/1/Rev.11)
Preferably, the final methyl propyl ketone peroxide formulation contains more than 10%, preferably more than 15%, more preferably more than 20, and most preferably more than 25% by weight of type-4 peroxide, based on the weight of the total formulation. Preferably, the amount of type-3 ketone peroxide in the formulations according to the invention is less than 13% by weight, based on the weight of the total formulation. It is noted that the amount of active oxygen associated with each of the peroxidic components is determined in the conventional way known in the art and that hydrogen peroxide is not a ketone peroxide. Furthermore it is noted that the term methyl propyl ketone peroxide includes peroxides derived from methyl isopropyl ketone and/or methyl n-propyl ketone. Preferred are the methyl isopropyl ketone-derived peroxide formulations.
The final methyl propyl ketone peroxide formulations may contain (residual) hydrogen peroxide. It was observed that in certain curing processes of unsaturated peroxides the speed of gelation was increased due to the presence of the H
2
O
2
. However, in some instances, such as when vinylester resins are cured, the presence of H
2
O
2
is undesirable as it gives foaming. Therefore, depending on the use of the formulations, it can be preferred to have from 0.001 to 5% by weight (% w/w) of hydrogen peroxide (based on the weight of the active oxygen of the hydrogen peroxide over the weight of the total active oxygen of the formulation) in the formulation.
Phlegmatizers that can be used in these formulations are of the conventional type and are preferably selected from alkanols, cycloalkanols, alkylene glycols, alkylene glycol monoalkyl ethers, cyclic ether substituted alcohols, cyclic amides, esters, ketones (preferably other than the ketone that is used to make the ketone peroxide being phlegmatized), a
Koers Frederik Willem Karel
Syed Ejaz Ahmed
Vries Bernhard
AKZO Nobel N.V.
Fennelly Richard P.
Short Patricia A.
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