Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-02-19
2001-02-27
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C528S094000, C528S112000
Reexamination Certificate
active
06194490
ABSTRACT:
The present invention relates to a curable composition comprising at least two different epoxy resins, a hardener, curing accelerator and filler, to the crosslinked products obtainable therefrom and to the use of these compositions as encapsulating material for electrical or electronic components.
In recent years, investigations were increasingly carried out with the objective to replace the conventional epoxy resins based on glycidyl ethers, glycidyl esters and cycloaliphatic epoxides at least in part by the inexpensive and ecologically and toxicologically safe epoxidised natural oils. However, the low curing rate and concomitant long gel time of such systems are insufficient for certain applications. The mechanical properties and, in particular, the low glass transition temperatures of the cured products are to date also unsatisfactory.
DE-A-2247617 describes epoxy resin compositions comprising mixtures of epoxidised natural oils and glycidyl ether resins which are cured with acid anhydrides and quaternary phosphonium salts as catalysts. These resin mixtures have high storage stability at room temperature and can be used as coating varnish for low voltage and high voltage insulators.
U.S. Pat. No. 4,040,994 discloses epoxy resin systems comprising a bisphenol A resin, a mixture consisting of least two epoxidised fatty acid esters, an anhydride hardener and a curing accelerator, for example a tertiary amine, which are distinguished by high thermal shock resistance and which can be used as adhesives, coatings, laminating resins and as electrical insulating materials.
However, the curing of these compositions proceeds only incompletely at the temperatures and curing times conventionally used for curing anhydrides, which is reflected in the relatively low glass transition temperatures of the cured products.
It is the object of this invention to provide curable compositions based on epoxidised natural oils which afford equally good or only slightly less good results with respect to mechanical properties and glass transition temperature as the conventionally used epoxy resins based on bisphenol diglycidyl ethers.
It has now been found that it is possible to fully cure within a short time epoxy resin mixtures comprising an epoxidised natural oil and a glycidyl compound or a cycloaliphatic epoxide using a combination of an anhydride hardener and a specific imidazole, amidine or amino-pyridine accelerator to products having good fracture-mechanical properties and a high glass temperature.
This invention relates to a composition, which comprises
(a) a compound containing at least one epoxy group in inner position per molecule, obtained by epoxidation of a natural unsaturated oil or of its derivative;
(b) an epoxy compound selected from the group consisting of glycidyl ethers, glycidyl esters and cycloaliphatic epoxides;
(c) a polycarboxylic acid anhydride;
(d) a compound of formula I, II, III or IV or an acid adduct of a compound of formula I, I, II or IV
wherein R
1
to R
4
are each independently of one another hydrogen; C
1
-C
18
alkyl which is unsubstituted or substituted by one or more than one hydroxyl group, amino group, halogen atom, cyano group, C
1
-C
6
alkoxy group or C
1
-C
6
cyanoalkoxy group; C
5
-C
14
aryl, C
6
-C
24
aralkyl, C
3
-C
14
heteroaryl or C
4
-C
14
heteroaralkyl which are unsubstituted or substituted by one or more than one C
1
-C
6
alkyl group, C
1
-C
6
alkoxy group or halogen atom,
n is an integer from 1 to 3, and
R
5
and R
6
are each independently of the other C
1
-C
6
alkyl or, together with the nitrogen atom, are a five- or six-membered ring, and
(e) 20-90% by weight, based on the entire composition, of a filler, the average diameter of the filler particles being from 0.1 &mgr;m to 5.0 mm.
Component (a) in the novel compositions may be epoxidation products of unsaturated fatty acid esters. It is preferred to use epoxy-containing compounds which are derived from mono- and polyfatty acids containing 12 to 22 carbon atoms and having a iodine value from 30 to 400, for example lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, ricinolic acid, linolic acid, linolenic acid, elaidic acid, likanic acid, arachidonic acid and clupanodonic acid.
Preferred components (a) are epoxidation products of triglycerides of formula IX
wherein R′, R″ and R′″ are each independently of one another saturated or unsaturated fatty acid radicals containing 12 to 25 carbon atoms, at least one of R′, R″ and R′″ being an unsaturated fatty acid radical.
Suitable epoxidation products are, for example, those of soybean oil, linseed oil, perilla oil, tung oil, oiticia oil, safflower oil, poppy oil, hemp oil, cottonseed oil, sunflower oil, rapeseed oil, high-oleic triglycerides, triglycerides of euphorbia plants, peanut oil, olive oil, olive kernel oil, almond oil, kapok oil, hazelnut oil, apricot kernel oil, beechnut oil, lupine oil, maize oil, sesame oil, grapeseed oil, lallemantia oil, castor oil, herring oil, sardine oil, menhaden oil, whale oil, tall oil and derivatives therefrom.
Also suitable are higher unsaturated derivatives which can be obtained by subsequent dehydration reactions of these oil.
The olefinic double bonds of the unsaturated fatty acid radicals of the above compounds can be epoxidised by known methods, for example by reaction with hydrogen peroxide, where required in the presence of a catalyst, an alkylhydroperoxide or a peracid, such as performic acid or peracetic acid.
Within the scope of this invention, component (a) may be both the completely epoxidised oils as well as the partially epoxidised derivatives yet having free double bonds.
Particularly preferred components (a) are epoxidised soybean oil and epoxidised linseed oil.
The properties of the cured products prepared from the novel compositions can be varied within a wide range. In particular the use of a mixture consisting of at least two different epoxy resins having different epoxy values as component (a) allows the specific adjustment of desired properties of the cured materials, for example an optimum balance between electrical and mechanical properties.
Another embodiment of this invention therefore relates to a composition, wherein component (a) is a mixture of two or more compounds having different epoxy values, in particular a mixture of epoxidised soybean oil and epoxidised linseed oil.
Suitable components (b) of the novel compositions are all types of epoxides containing a glycidyl or &bgr;-methylglycidyl group or a cycloalkylene oxide radical.
Examples of suitable epoxy resins are polyglycidyl ethers and poly(&bgr;-methylglycidyl)ethers, which are obtainable by reacting a compound, containing at least two free alcoholic and/or phenolic hydroxyl groups per molecule, with epichlorohydrin or &bgr;-methylepichlorohydrin under alkaline conditions or in the presence of an acid catalyst with subsequent treatment with alkali.
Suitable starting compounds for the preparation of such glycidyl or &bgr;-methylglycidyl ethers are, for example, acyclic alcohols, such as ethylene glycol, diethylene glycol and higher poly-(oxyethylene)glycols, propane-1,2-diol and poly(oxypropylene)glycols, propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene)glycols, pentane-1,5-diol, hexane-1,6-diol, hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane, pentaerythritol or sorbitol, cycloaliphatic alcohols, such as resorcitol, quinitol, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4-hydroxycyclohexyl)propane and 1,1-bis(hydroxymethyl)-cyclohexene-3, and alcohols containing aromatic nuclei, such as N,N-bis(2-hydroxyethyl)aniline and p,p′-bis-(2-hydroxyethylamino)diphenylmethane.
Other dihydroxy compounds suitable for the preparation of glycidyl or &bgr;-methylglycidyl ethers are mononuclear phenols, such as resorcinol and hydroquinone, polynuclear phenols, such as bis(4-hydroxyphenyl)methane, 4,4-dihydroxydiphenyl, bis(4-hydroxyphenyl)sulfone, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)prop
Malherbe Roger
Roth Martin
Schoenenberger Catherine
Tang Qian
Aylward D.
Dawson Robert
Kovaleski Michele A.
Vantico Inc.
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