Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1996-01-25
1998-01-13
Gulakowski, Randy
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528 93, 528112, 528113, 525504, 525523, 525533, C08G 5900, C08G 6508
Patent
active
057081204
DESCRIPTION:
BRIEF SUMMARY
This invention relates to gelled, uncured epoxy resin based compositions. That is compositions where the reactive ingredients they have been made from have reacted to at least the level where they can no longer be effectively melted but contain some unreacted epoxy groups and hardener groups to react further.
The invention is concerned with the compositions themselves, the method of making them and their use when cured alone or in contact with other reactive resin systems particularly epoxy resins, but also with polyester, acrylic and isocyanate based materials.
Little attention has been given to gelled uncured epoxy resin compositions in the past as the lack of flow under heat and relatively poor mechanical properties have made them unsuitable for most standard processing methods and end use requirements.
Surprisingly we have found that these compositions have advantages in respect of (a) their inability to melt and wet surfaces they are in contact with, (b) their ability to be ground, pulverised, cut or powdered more easily compared to their fully cured counterparts, (c) their ability to be shaped and then be heat cured to full reaction, without flowing, (d) their ability to react at or near their outer surfaces with other reactive materials, giving strong and chemical resistant bona, and (e) their ability to be further cured by heating without sintering together.
This combination of features allows the easy manufacture of gelled compositions and cured products with a wide range of interesting properties that can be usefully employed in a variety of ways.
The gelled compositions provided by this invention are made by reacting, or allowing to react, epoxy resins with hardeners until they have reached the gel or non flowing stage and stopping the reaction or allowing it to stop itself. Stopping the reaction is usually achieved by lowering the temperature to the point where the reaction slows greatly or when the resin and hardener system itself reacts to the point where it is solid enough to be slowed greatly or when them are two or more hardener systems present some of which react to give a gel and the remainder do not react much until heated further.
Usually the resins and hardeners are mixed together and reacted or allowed to react in containers which if the correct conditions are selected will result in gelled, non fully cured masses. The gelled materials provided by this invention may be physically changed in shape by warming them to above their softening temperature and applying a mechanical load. Depending on the actual composition selected the temperature needed to do this forming will usually be much lower than if the composition was fully cured, and this temperature differential can be as high as 200.degree. C.
If the heated changed shape is cooled under constraint it will maintain this shape until warmed unconstrained near to its softening temperature when the original shape will be largely restored. The ability to do this applies to some extent to most thermoset materials, but this invention provides a major difference in that, provided the hardener system has been carefully selected, continued heating after thermal forming will result in full cure occuring in the new shape which then becomes permanent despite unconstrained heating close to the softening temperature.
As the compositions are already gelled before forming they will not melt and stick to the surfaces in contact with them during this forming operation and for the same reason can be cut, sawn, drilled and machined both before or after final curing without wetting or in general sticking to the tools. They may also be produced in any form by pregelation treatment and then gelled. Ungelled, gellable compositions of this invention may either be allowed to gel at room temperature or heated to achieve gelation at temperatures which do not significantly initiate the reaction of the optional hardener system (c) as hereinafter described.
Heat curable, gelled, resin compositions of the present invention may be broken, cut, ground, or powdered
REFERENCES:
patent: 3538039 (1970-11-01), Lantz et al.
patent: 3996186 (1976-12-01), Schreiber et al.
patent: 5214098 (1993-05-01), Setiabudi et al.
patent: 5312651 (1994-05-01), Takada et al.
patent: 5480957 (1996-01-01), Murio et al.
Lee et al, Handbook of Epox Resins, pp. 7-1 through 7-14, McGraw Hill, 1982.
Ciba Specialty Chemicals Corporation
Crichton David R.
Gulakowski Randy
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