Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-05-18
2000-09-19
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
521135, C08L 6300
Patent
active
061213489
DESCRIPTION:
BRIEF SUMMARY
This invention relates to heat curable, solid epoxy resin compositions which are especially suitable for use in powder form but are also useful in other configurations such as pellets, tablets, rods and sticks for example and in general have a Kofler Heat Bank melting point greater than 55.degree. C. The compositions can also be foamable.
Solid, curable epoxy resin compositions are well known and find many useful commercial applications. These include for instance, protective and decorative coatings, electrical insulation, encapsulants, moulding compounds, adhesives and matrix resins for fibre reinforced composites.
Solid heat curable epoxy resin compositions are eventually used by a hot melt process whether it is by application in the already molten state or applied to an already heated surface and melts on contact or applied by techniques such as electrostatic spraying or placing in a mould and then melted and cured on heating.
For solid epoxy resin compositions to be useful in powder form they need to have a melting point as determined by the Kofler Heat Bank method of at least 55.degree. C. and preferably 65.degree. C. Powders with lower melting points rapidly sinter together when stored at normal workshop temperatures (15.degree.-30.degree. C.) and become unpourable. Low melting powders can be cold stored but this is expensive and gives rise to moisture condensation when exposed to normal workshop conditions making them less suitable for many applications.
Little attention has been given to these materials in the form of foamable powders although they can give significant advantages in terms of low density, low thermal conductivity, gap filling, accurate mould filling and lower costs, and some or all of these properties can be used to advantage in the end applications listed above.
Epoxy resin powders should find even more widespread use if they could be produced with a broader range of application and cured physical properties.
Desirable properties in such powders include a long usable life at normal workshop temperatures, a range of curing temperatures from 80.degree. to 260.degree. C. preferably from 90.degree. C. to 220.degree. C. within practical cure times, a wide band of melt viscosities and a variety of cured mechanical and thermal properties to suit particular uses. These desirable properties apply just the same for foamable powders which will normally be used by melting on contact with a heated surface or applied by techniques such as electrostatic spraying or placing in a mould or cavity and then melted and cured on heating.
The following list expands and helps to describe the properties which can be required from such epoxy powders.
The powder should flow and pour freely with no tendency to sinter or agglomerate over the whole period of its usable life at normal workshop temperatures. To achieve this property the powder should have a melting point of at least 55.degree. C. and preferably 65.degree. C. as determined by the Kofler Heat Bank method.
This should be at least three months at workshop temperatures and preferably in excess of 6 months. During this period the melting point should not increase to the point where the application properties or the cured product performance shows significant change.
It is very important that little or no separation of active ingredients occurs during storage or application as this can give rise to serious variation of properties in the final cured product.
Low melt viscosities are very valuable in obtaining smooth well adhered films when the powders are essentially used for coating purposes, whereas much higher viscosities may be needed for pressurised applications such as moulding powders or composite laminate manufacture.
There are a number of applications where temperatures as low as 100.degree. C. or even lower, are desirable for curing, especially when in contact with heat sensitive materials such as some plastics, or when differential expansion stresses should be small. There are also many coating applications where very rapid flow and cure is ne
REFERENCES:
patent: 5708120 (1998-01-01), White
patent: 5908901 (1999-06-01), White
Derwent Abstract No. 90-309077
Derwent Abstract No. 79-26941B
Cain Edward J.
Ciba Specialty Chemicals Corp.
Crichton David R.
Kovaleski Michele A.
LandOfFree
Powderable reactive resin compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Powderable reactive resin compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Powderable reactive resin compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1073945