1. A reactive resin composition, which is a fusible, solid optionally foamable, heat curable, epoxy functional reaction prouct with a Kofler Heat Bank melting point of not less than 55.degree. C., formed by mixing together PA1 (A) epoxy resins of epoxy group containing compounds PA1 (B) an amine solidifying system present in insufficient quantities to cause gelation after all the amino hydrogen atoms are consumed by epoxy groups, under the reaction conditions chosen for (A) and (B), and which yields a product with a Kofler Heat Bank melting point of greater than 55.degree. C. and less than 120.degree. C. and melting point stability of at least six months normal workshop temperatures, PA1 (C) a hardener system for (A) and the reaction product of (A) and (B) which is different from (B) and remains substantially unreacted under the conditions of reaction chosen for (A) and (B) with (A) and (B) and which is of low reactivity at normal workshop temperatures in the final solid epoxy formulation, optionally, PA1 (D) an expanding agent which is of low reactivity under the conditions of reaction chosen for (A) and (B) and which is of low reactivity at normal workshop temperatures in the final solid epoxy formulation, and optionally PA1 (E) other additives that may be required to modify the physical properties of the cured or uncured composition.

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. 
(a) Powder Flow 
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. 
(b) Shelf Life 
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. 
(c) Homogeneity 
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. 
(d) Application Melt Viscosity 
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. 
(e) Curing Temperatures 
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 needed to obtain speed of 
production and in these cases cure temperatures in the range of 
180.degree. C. to 260.degree. C. are more useful. 
(f) Curing Speed 
All curing times must be economically short but a realistic range falls 
between 4 hours for powders capable of cure at the lowest end of the 
range, e.g. 80.degree. C. and a few seconds for those designed for rapid 
production lines at 180.degree. C. to 260.degree. C. 
(g) Temperature Resistance 
Requirements will depend on the actual application and the other properties 
needed but powders capable of giving a glass transition temperature Tg, as 
high as 180.degree. C. or more as measured by Differential Scanning 
Calorimetry are valuable in many areas. 
(h) Other Properties 
Many requirements need to be met to satisfy all applications, but important 
among those are toughness, flame and smoke suppression, chemical 
resistance and adhesion. 
Hitherto, various methods have been proposed for the manufacture of epoxy 
powders and they fall principally within the following generalised 
techniques. However, none of these are capable of providing a range of 
powders which can meet the full spread of properties listed under (a) to 
(h) above. 
(1) Hot Melt Mixing 
This process is one of blending solid epoxy resins, hardeners and other 
additives as required above the melting point of the resins, then cooling, 
grinding and sieving to obtain the required particle size range. This is 
an effective and widely used technique but because the resin Kofler Heat 
Bank melting point should preferably be not less than 65.degree. C. it is 
necessary for the mixing to be carried out in excess of 100.degree. C. 
This method largely excludes hardeners that can be used for lower 
temperature curing. It also gives difficulties where very high melt 
viscosity systems are required due to the need to achieve sufficiently low 
viscosity for mixing. 
(2) Blending of Powders 
It has been proposed that solid powdered resins, solid powdered hardeners 
and other additives can be simply mixed together to give useful curable 
powders. GB Patents 1,147,370; 1,164,049; 1,361,909; 1,362,455; 1,371,967; 
1,379,928; 1,446,870; 1,568,914. U.S. Pat. Nos. 4,113,684; 4,120,913. Even 
if carried out over long periods of time and in very fine particle size 
this normally leads to blends liable to serious separation on storage or 
application due to differences in particle size, shape or density. 
To improve the homogeneity and reduce the separation potential of these 
blends it has been proposed that they are warm sintered and then reground 
and sieved. This is time consuming and expensive and may cause unwanted 
reaction to occur particularly as this technique is usually proposed for 
highly reactive systems. 
Sintering and regrinding cannot totally prevent resin and hardener 
separation as it will always result in a heterogeneous composition unless 
the particles are extremely fine so approaching intimate mixing when 
potential unwanted reaction problems become even more likely. If the 
system is not of high reactivity then the Hot Melt Mixing method is more 
satisfactory. 
The resins and hardeners used in Powder Blending may be themselves the 
solid reaction products of excess resin or hardener with corresponding 
hardener or resin. 
(3) Production of B-Stage Compounds 
The term B-stage is used to denote a stage of reaction between resins and 
hardeners which is intermediate between the A-stage, completely unreacted, 
and the C-stage gelled or cured, where all the reactable ingredients have 
reacted to the point where the mixture has become solid enough to 
significantly slow further reaction. 
In this approach blends are made of resins and hardeners which all react 
together under the chosen conditions until the reaction products have the 
desired melting point, as exemplified by GB Patent 871,350; 1,019,925; 
1,403,922; 1,529,588. U.S. Pat. No. 4,120,913. The reaction temperature 
may be room temperature or above. At this point most of the molecules 
present have partially reacted to form a mixture of various oligomers. At 
this extent of reaction further reaction becomes very slow at room 
temperature and may be slow enough to allow the product to be powdered and 
have some useful shelf life. As the powder is heated in its final 
application, so the reaction starts again, and as the hardeners are 
effectively bound into the high molecular weight reaction products the 
melt viscosity is always high and there is rarely sufficient time for such 
products to flow readily and usefully in the absence of external pressure 
before they reach the gelation point and stop flowing at all. 
This approach has been studied extensively and often used in the production 
of moulding compounds. However, typical hardeners used in this way such as 
4,4'-diaminodiphenyl methane. 1,3 diamino benzene and various tolylene 
diamines usually only give shelf lives of a few days to weeks at normal 
shop floor temperatures before gelation. 
(4) Differential Reactivity Products 
It has been suggested that useful powders can be made by employing two 
types of hardener for liquid epoxy resins (Japanese Patent 51037152) in 
which one hardener type is capable of curing efficiently at least 
20.degree. C. below the second hardener type. In the case of the lower 
temperature curing hardener type it is polyfunctional and it is proposed 
that 40% to 70% of the quantity normally used to fully cure the resin be 
used with the remaining unreacted epoxy groups being available for cure 
after flow by the second higher temperature curing hardener type. The 
disadvantage of this approach is that the use of such a high percentage of 
the lower temperature curing polyfunctional hardener which is necessary to 
obtain non-sintering powders is close to or above the amount capable of 
giving gelation and results in the solid composition gelling very rapidly 
on heating and hence of little value as a normal epoxy powder for coatings 
and does not form part of this invention. In the latter case the 
disadvantages are very much the same as in the case of B-staged materials 
as exemplified by very high viscosities and very short flow times. 
These methods, for similar reasons, also restrict the range and type of 
acceptable foamable epoxy powders designed to cure in the range of 
80.degree. to 180.degree. C. especially when they contain ingredients 
which are very sensitive to temperature and this make the Hot Melt 
technique particularly unsuitable. 
Similar problems are encountered in the case of Powder Blending when the 
foaming agents are melt incorporated into the resin, the hardener, or both 
simultaneously. Where the foaming agents are simply blended into the 
system the resulting product is likely to suffer from inconsistencies due 
to separation on shipment, storage and shop floor use. 
B-staging generally gives little time for good foaming to occur before 
rapid gelation. 
Until now there has been no general method of producing heat curable epoxy 
functional powders with sufficient tolerance and flexibility to achieve 
the full range of desirable physical properties to satisfy the extremes of 
the application and cured product requirements. So it has been very 
important to find a method to make such powders which have a wide range of 
properties, excellent stability and can be manufactured reliably. 
We have now discovered a surprisingly simple type of composition which 
permits the safe manufacture of heat curable, powderable, solid epoxy 
resin systems under extremely mild processing conditions and also allows 
all the physical requirements listed under (a), (b) and (c) above to be 
satisfied as well as the application and property extremes under (d), (e), 
(f), (g) and (h). This consists of making an epoxy formulation which is 
liquid at 120.degree. C. or below, more usually at normal shop floor 
temperatures, and adding to it a chemical solidifying system which reacts 
very slowly at these temperatures with the epoxy materials present. 
Accordingly, the present invention provides a one component heat curable 
epoxy functional powderable materials comprising: 
(A) epoxy resin s or epoxy containing compounds, 
(B) a solidifying amine system which will react with (A) to give a product 
with a Kofler Heat Bank melting point of between 55.degree. and 
120.degree. C., but which is not present in sufficient quantities to allow 
or cause chemical gelation under the reaction conditions chosen for (A) 
and (B) and which essentially stops solidifying before or when all its 
active epoxy additive hydrogen groups are consumed by the epoxy groups, 
(C) a hardener system for (A) and the reaction product of (A) and (B) which 
is different from (B) and which remains substantially unreacted under the 
conditions of reaction chosen for (A) and (B) with (A) and (B), and 
optionally, 
(D) an expanding agent which is of low reactivity under the condition of 
reaction chosen for (A) and (B) and which is of low reactivity at normal 
workshop temperatures in the final solid epoxy formulation and optionally, 
(E) Other additives that may be required to modify the physical properties 
of the cured or uncured composition. 
The solidifying system must be picked to give very little reaction during 
the time it is in mixing with the epoxy resin and hardeners, by whatever 
method this is done, so that there is very little viscosity rise or 
temperature rise during the blending operation and hence making the 
filling of large or small simple or complicated containers a relatively 
easy task. Alternatively mixing may take place in the final container if 
required. 
The solidifying reaction must be a simple amine addition reaction with the 
epoxy groups and must stop when the addition reaction stops. No tertiary 
amines may be present in the initial mixture or generated during the 
reaction which could significantly react under the conditions chosen for 
the solidification reaction. Such reactions severly compromise safety 
during bulk mixing, solidification once mixed and the softening point 
stability and shelf life of the resultant product. The solidifying system 
must be picked to satisfy these criteria. 
This general composition also allows, either complete homogeneity of all 
the reactive ingredients or effective encapsulation of those not soluble 
in the original blend and also allows a wide range of viscosities and gel 
times to be designed into the product. 
The solidifiable epoxy resin composition is made by blending (A), (B), (C), 
(D) and (E) together by any convenient batch or continuous operation but 
in such a way that at least (A) and (B) become homogeneous. The reaction 
between (A) and (B) may be carried out at any suitable temperature and 
condition provided that neither it, nor the enothermic heat generated from 
it causes (C) or (D) to substantially react whilst it is taking place. 
By adopting the technique of this invention it becomes a relatively simple 
matter to produce optionally foamable powderable solid epoxy resin 
compositions which avoid the problems or difficulties or extreme 
conditions used with most current and other proposed methods for making 
powderable solid epoxy resin formulations. 
It now becomes possible to avoid: 
(i) The Hot Melt Mixing of solid epoxy resins with hardeners and other 
ingredients at relatively high temperatures. This invention allows the use 
of liquid resins or low temperature melting resins or blends. 
(ii) The Blending of Powders together and the consequent chances of 
physical separation inhomogeneity and variable physical properties. This 
invention overcomes these disadvantages as it allows for liquid or soluble 
hardeners which will normally result in homogeneous compounds or 
alternatively for solid hardeners which can be finely ground and 
thoroughly dispersed in the resin or other components before final mixing, 
so that the resultant powder is effectively homogeneous and the fine 
hardener particles basically encapsulated in the solid resin. 
(iii) The Production of B-stage Compounds of all types with their 
associated problems of high viscosity for processing and frequently very 
short shelf life. This invention specially sets out to avoid B-staging by 
creating the solid resin "in-situ" under mild conditions thus leaving the 
ultimate hardener effectively unreacted. This permits much greater case of 
wetting and flow of the molten powder before gelation when required. 
It now becomes possible to obtain: 
Powders with either low or high melt viscosities as required through the 
careful selection of (A) and (B). 
Powders curing in 2 hours at 100.degree. C. or less or a few seconds at 
180.degree. C. to 260.degree. C. by the careful selection of (C). 
A wide range of desired mechanical and thermal properties by the careful 
selection of (A), (B) and (C). 
Ready modification of physical and mechanical properties may also be 
achieved by the introduction of additives. (E) including those heat 
sensitive in nature. 
All of the above advantages and desired properties complemented by the long 
workshop temperature shelf life desirable for simple storage 
transportation and use. 
The epoxy resins or epoxy group containing compounds (A) employed in this 
invention may be glycidyl ethers, glycidyl amines, glycidyl esters or 
cycloaliphatic compound or combinations of these including halogenated 
versions where required. Preferred epoxy resins and blends are those which 
are suitable liquids for ready mixing with the other ingredients at 
suitable temperatures which will usually be below 120.degree. C. Epoxy 
resins or epoxy containing compounds or blends of them which are liquid at 
room temperatures are the most convenient. 
The preferred solidifying systems (B) used to convert the liquid resins are 
principally compounds or mixtures of compounds whose most reactive groups 
relative to the epoxy materials employed are primary or secondary amines. 
Epoxy reactive tertiary amines under the conditions of reaction chosen for 
(A) and (B) are not acceptable for this invention. 
Of particular usefulness in this process are aromatic and cycloaliphatic 
primary and secondary amines and blends of these. The major advantage of 
these amines, particularly the aromatic amines, is the low rate of 
reactivity coupled with the extremely long life at normal ambient 
temperatures of their reaction products with the resins. With the majority 
of compounds from these classes of amines the life of the reaction product 
with the resins greatly exceeds that of the life of the resins with their 
primary hardeners (C). Some alicyclic, heterocyclic and aliphatic amines 
are also effective as advancing agents and those which comply with 
cessation of reaction once their amino hydrogen atoms have been consumed 
by the epoxy resins and considered as part of this invention. In all cases 
it is essential that the tertiary amines generated during the 
solidification reaction have very low reactivity with epoxy groups under 
the conditions of reaction chosen for (A) and (B) and afterwards during 
storage. The solidifying amines are usually and mostly difunctional and/or 
polyfunctional with respect to the epoxy compounds (A) although 
monofunctional amines can be used to some extent if of value to a 
particular composition. 
Difunctional maines may be used at any desired ratio with difunctional 
epoxy resins but greater than difunctional amines only to levels where 
gelation does not occur. The solidifying systems may contain a variety of 
other groups but these should only be of very low or no reactivity towards 
the epoxy groups involved under the reaction of (A) and (B). 
Most useful are those solidifying systems which react gradually to 
substantial completion at room temperatures over a period of around 2-14 
days. These permit the safe manufacture of batches in excess of 100 litres 
in a realistic mixing time with little temperature rise in the mixing 
vessel or during discharge and smooth reaction to the required physical 
state in most practical containers, however mixed over a practical 
timescale. Under these conditions the heat of reaction generated by the 
solidification process is evenly dissipated by conduction and radiation 
and results in no more than acceptable temperature rises at any stage in 
the process. 
The primary controlling factor being that the mixture reaction temperature 
rise whether in the mixing vessel or the containers shall be below that 
required to cause significant reaction between (A), (C) or (D). 
Should it be desirable to speed the solidification in the final container 
this can be achieved by heating provided the temperature used does not 
cause significant reaction of (C) with (A) or the reaction product of (A) 
and (B) either by direct heat or that evolved by completing the reaction 
between (A) and (B) or by the addition of accelerators such as carboxylic 
acids which do not adversely affect the softening point stability. 
The solidifying systems must be present in such quantities that when their 
amino hydrogen atoms are all substantially reacted with the epoxy 
materials (A) under the conditions set for reaction (A) and (B) the 
product is not chemically gelled and has a melting point which is greater 
than 55.degree. C. and lower than 120.degree. C. and is essentially stable 
for greater than 6 months at 22.degree. C. The resultant product is a 
brittle solid at 22.degree. C. which could be cast into various physical 
forms such as sticks or pellets, but is essentially useful for grinding 
into powders. 
The selection and quantity of the solidifying agent will also influence a 
variety of properties such as melt viscosity, strength, toughness and heat 
resistance and by careful choice advantages may be designed into the 
uncured or cured products resulting from the use of the process. 
The hardener systems, (C) for the epoxy compounds (A) and the reaction 
products between (A) and (B) can be selected from the wide variety of 
those well known in the field of epoxy chemistry other than acid 
anhydrides which react preferentially with the advancing agents (B). 
Typical but not exclusive examples of useful hardeners are aromatic amines 
such as diaminodiphenyl sulphones, boron trifluoride amine complexes, 
latent imidazoles, carboxylic acids, biguanides, hydrazides, 
dicyandiamide, latent epoxy amine adducts and substituted ureas. As 
explained a main requirement of the hardener is that it should not 
substantially react whilst (A) and (B) are being reacted to form the epoxy 
composition which has a melting point greater than 55.degree. C. There may 
be one or several hardeners used together, some of which may accelerate 
the curing rates of the other provided they comply with the requirement 
immediately above. 
The expanding agents (D) may be of any type which does not adversely 
interfere with the production of the solid epoxy composition nor its 
ability to cure satisfactorily. The expansion obtained may result from 
chemical or physical reactions or both. An important feature is that the 
foaming agent should not cause substantial foaming during the process for 
the production of the solid epoxy compositions, nor on storage of it in 
any form at normal workshop temperatures or below. All significant 
expansion should take place during the actual curing cycles. 
Examples of suitable expanding agents include 
Azodicarbonamide, Azodiisobutyronitrile, Benzene sulphonhydrazide, 
Dinitroso pentamethylene tetramine, Oxybis benzene sulphonhydrazide, p 
toluene sulphonyl hydrazide and Expandable plastic such as those sold 
under the Trade Name Expancel. 
These are largely spherical shells of varying composition such as 
polyvinylidene chloride and or polyacrylonitrile plus other copolymerised 
additives, and the inside contains isopentane.+-.air. 
Other additives, (E) which can be used to modify the physical properties of 
the cured or uncured compositions include but are not limited to 
thixotropes, toughening agents, wetting agents, surfactants, fibrous 
materials, dyes, pigments, fillers, flame retardants, smoke suppressants, 
coupling agents, hollow microspheres, flow assisting materials, fusible 
glasses and stabilisers.

The following Examples demonstrate some of the wide range of compositions 
which may be successfully used according to this invention. 
EXAMPLE 1 
A liquid Bisphenol A epoxy resin (EPIKOTE 828 - SHELL CHEMICAL CO.) with an 
epoxy content of approximately 5.3 gram equivalents of epoxy oxygen per 
kilogram was blended with amino benzene and dicyandiamide as follows: 
______________________________________ 
EPIKOTE 828 100 parts by weight 
amino cyclohexane 18 parts by weight 
dicyandiamide 4 parts by weight 
______________________________________ 
This mixture was thoroughly dispersed at 22.degree. C. After five days the 
mixture was brittle and easily powdered and had a Kofler Heat Bank melting 
point of 65.degree. C. 3 years later this melting point was 68.degree. C. 
A portion was heated for two hours at 80.degree. C. and on cooling the 
blend could easily be powdered and had a Kofler Heat Bank melting point of 
approximately 72.degree. C. and remained unsintered for a least 3 years 
when stored at 22.degree. C. On heating to 180.degree. C. the powder 
melted to a free flowing liquid, then gelled and after 60 minutes was a 
strong, tough, thermoset, plastic compounds. 
EXAMPLE 2 
A crystalline Bisphenol F resin (PY 306 - Ciba-Geigy) with an epoxy content 
of approximately 6.2 gram equivalent of epoxy oxygen per kilogram was 
blended well with 4 aminotoluene and 4,4' diaminodiphenyl sulphone as 
follows: 
______________________________________ 
PY 306 100 parts by weight 
4aminotoluene 26 parts by weight 
44' diaminodiphenyl sulphone 10 parts by weight 
______________________________________ 
The 44' diaminodiphenyl sulphone was sieved through a B.S. 300 mesh sieve 
to obtain a fine powder free from lumps and this was dispersed thoroughly 
in 50 parts of liquid PY 306 at 22.degree. C. obtained by warming the 
crystalline resin to 100.degree. C. and allowing it to cool. The 
4aminotoluene was warmed with the remaining 50 parts of liquid PY 306 at 
55.degree. C. until it melted and dissolved. 
The two parts were then mixed together and allowed to stand at 22.degree. 
C. for two days. They were then heated to 60.degree. C. for five hours. 
The resulting solid was easily powdered and had a Kofler Heat Bank melting 
point of around 65.degree. C. When cured for two hours at 180.degree. C. 
it was a tough solid with a glass transition point of around 120.degree. 
C. After six months at 22.degree. C. the melting point had increased by 
only 5.degree. C. and the powder was free flowing. 
EXAMPLE 3 
The following mixture was prepared: 
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EPIKOTE 828 90.0 parts by weight 
butane diol diglycidyl ether 10.0 parts by weight 
4,4' diamino 3,3' dimethyl dicyclohexylmethane 8.5 parts by weight 
aminobenzene 9.6 parts by weight 
dicyandiamide 4.0 parts by weight 
______________________________________ 
The finely powdered dicyandiamide was thoroughly mixed into the low 
viscosity blend of the other ingredients and the dispersion was placed 
inside a polythene bag. After 4 days at 22.degree. C. it was a brittle 
solid. The solid was then heated for 3 hours at 70.degree. C. It was 
powdered and had a Kofler Heat Bank melting point of around 65.degree. C. 
Three months later it still poured readily. On heating for 1 hour at 
180.degree. C. the mixture first melted, then flowed readily, gelled and 
became a tough solid. 
A further mixture of this composition was prepared and left for 7 days at 
22.degree. C. After this time it was a brittle solid with a Kofler Heat 
Bank melting point of 61.degree. C. Six months later it poured readily and 
the melting point had increased by 4.degree. C. 
EXAMPLE 4 
The following mixture was prepared: 
______________________________________ 
DER 332 100.0 parts by weight 
4,4' diamino 3,3' dimethyl dicyclohexyl methane 5.8 parts by weight 
aminobenzene 9.3 parts by weight 
4,4' diaminodiphenyl sulphone 16.4 parts by weight 
______________________________________ 
DER 332 is a nearly pure Bisphenol A diglycidyl ether solid by DOW Chemical 
Co. The DER 332 was warmed to 50.degree. C. to melt it and after cooling 
was mixed with the 4,4' diaminodiphenyl sulphone powder. This blend was 
run through a triple roll mill to obtain a good dispersion. The remaining 
amines were added and the resultant blend was covered with a polythene 
film and allowed to solidify at 22.degree. C. for 4 days. The mixture was 
then heated for two hours at 60.degree. C. and cooled. It was a brittle 
solid with a Kofler Heat Bank melting point of around 70.degree. C. It was 
powdered and six months later had increased in melting point by 
approximately 2.degree. C. 
The powder was heated in a released container for 2 hours at 100.degree. C. 
4 hours at 150.degree. C. and then post cured for 4 hours at 200.degree. 
C. The resultant polymer possessed a TG of 182.degree. C. as measured by 
the D.S.C. method. 
EXAMPLE 5 
The following mixture was prepared: 
______________________________________ 
DEN 438 20 parts by weight 
DER 331 80 parts by weight 
aminobenzene 20 parts by weight 
Anchor 1040 3 parts by weight 
______________________________________ 
DEN 438 is a semi solid epoxy novolak resin sold by DOW Chemical Co with an 
epoxy content of about 5.6 gram equivalents of epoxy oxygen per kilogram. 
DER 331 is a liquid Bisphenol A epoxy resin sold by DOW Chemical Co with an 
epoxy content of about 5.2 gram equivalents of epoxy oxygen per kilogram. 
Anchor 1040 is a coordination complex of boron trifluoride marketed by 
ANCHOR Chemical Co. 
The two resins were warmed and mixed together and allowed to cool to 
22.degree. C. The remaining ingredients were added with stirring to give 
an homogeneous blend. After three days the mixture was heated at 
55.degree. C. On cooling it was a brittle solid which was easily powdered. 
It had a Kofler Heat Bank melting point of around 65.degree. C. On heating 
to 180.degree. C. for 60 minutes it melted, gelled and cured to give a 
hard thermoset plastic. 
After six months the powder flowed readily and melted at around 70.degree. 
C. 
EXAMPLE 6 
The following mixture was prepared: 
______________________________________ 
EPIKOTE 828 100.0 parts by weight 
4,4' diamino diphenyl methane 8.8 parts by weight 
aminobenzene 6.1 parts by weight 
dicyandiamide 3.5 parts by weight 
3(4 chorophenyl) 1.1 dimethyl urea 2.7 parts by weight 
fumed silica 3.5 parts by weight 
carbon black 1.0 parts by weight 
______________________________________ 
The carbon black, dicyandiamide and substituted urea were mixed with 50 
parts of the liquid resin and triple roll milled to obtain a good 
dispersion. This was then blended with a solution of the 4,4' diamino 
diphenyl methane in the remaining resin and the other ingredients. The 
whole mixture was placed in a container and after 7 days at 22.degree. C. 
the blend was a brittle solid. It was heated for 2 hours at 60.degree. C. 
then cooled and powdered. It had a melting point of around 60.degree. C. 
This powder remained free flowing for at least 6 months at 22.degree. C. 
and showed no increase in melting point. The powder was applied to clean 
steel rods, heated to 180.degree. C. by fluidised bed techniques and gave 
a smooth black coating which adhered well and was very tough after a cure 
of 180 minutes at 100.degree. C. 
EXAMPLE 7 
The misture in Example 1 was poured into a tray and heated for 5 hours at 
80.degree. C. On cooling it was a brittle, powderable solid with a melting 
point of 80.degree. C. After 9 months at 22.degree. C. this powder flowed 
freely and retained the same melting point. On heating to 180.degree. C. 
for 1 hour it cured to form a tough, thermoset product. 
EXAMPLE 8 
A liquid Bisphenol A epoxy resin (EPIKOTE 828 - SHELL CHEMICAL CO.) with an 
epoxy content of approximately 5.3 gram equivalents of epoxy oxygen per 
kilogram was blended with aminobenzene. 44' diamino diphenyl sulphone, 44' 
oxybis benzene sulphonylhydrazide and a fumed silica. 
All the powders were passed through a B.S. 300 mesh sieve to remove any 
agglomerates and were then thoroughly dispersed by passing a triple roll 
mill with 50 parts of the liquid resin. 
The composition employed was: 
______________________________________ 
EPIKOTE 828 100.0 parts by weight 
aminobenzene 19.7 parts by weight 
44' diamino diphenyl sulphone 6.6 parts by weight 
44' oxybis benzene sulphonylhydrazide 1.0 parts by weight 
fumed silica 2.0 parts by weight 
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All the components were mixed together and placed in a released tray. After 
five days the solid blend was heated for two hours at 60.degree. C. On 
cooling to 22.degree. C. the blend could easily be powdered. The powder 
had a Kofler Heat Bank melting point of approximately 70.degree. C. After 
storing at ambient temperature for six months the softening point was 
approximately 73.degree. C. and no sintering had occured. On heating to 
180.degree. C. the powder melted, rapidly increased in viscosity, foamed 
and cured. After 60 minutes a strong tough, thermoset foam was obtained. 
EXAMPLE 9 
The following mixture was produced: 
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EPIKOTE 828 100.0 parts by weight 
44' diamino 33' dimethyl dicyclohexyl methane 10.6 parts by weight 
benzylamine 7.1 parts by weight 
azodiisobutyronitrile 3.0 parts by weight 
dicyandiamide 3.5 parts by weight 
3(4chlorophenyl) 1,1 dimethylurea 2.9 parts by weight 
fumed silica 8.0 parts by weight 
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All the solids with the exception of the fumed silica were sieved and 
milled with 10 parts of liquid resin as per EXAMPLE 8. The fumed silica 
was added as the last ingredient to the mixture, which then became very 
thixotropic. The mixture was placed in a tray and was covered with a 
polythene film. After five days the mixture was a brittle solid. On 
powdering the Kofler Heat Bank melting temperature was 65.degree. C. When 
tested after storage at normal ambient temperature for 850 days the 
softening temperature had increased by 13.degree. C. to 80.degree. C. and 
the powder flowed freely with no sign of sintering. 
After initial powdering the coarser and finer particle fractions were 
removed leaving a particle size range between 250 and 2500 microns. The 
powder was placed into a tube of 0.65 centimetre diameter, closed at one 
end to the point where the tube was full of powder. The filled tube was 
then put into an oven and heated for 1 hour at 120.degree. C. At the end 
of this time the tube was filled with a strong cured foam which was still 
of approximately the same volume as the tube. On careful examination of 
the physical curing process it became clear that the composition particles 
melted but did not flow and then expanded to fill the voids between them 
to give the final foam filled tube. The density of this foam was 0.6 grams 
per cubic centimetre. It will be apparent to workers in this field that 
the powder of this example could be used as a lower density gap filling 
adhesive if the tube was clean and receptive to bonding or as a low 
density moulding or casting material if the tube was release treated to 
prevent adhesion. 
EXAMPLE 10 
The following mixture was produced: 
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EPIKOTE 828 100.0 parts by weight 
44' diamino 33' dimethyl dicyclohexyl methane 10.0 parts by weight 
aminocyclohexane 6.6 parts by weight 
phenolic microbaloons 10.0 parts by weight 
Expancel 550 DU 3.0 parts by weight 
dicyandiamide 3.5 parts by weight 
3(4chlorophenyl) 1,1 dimethylurea 2.9 parts by weight 
fumed silica 2.0 parts by weight 
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Expancel 550 DU is a type of very small diameter expandable plastic bead. 
Phenolic microballoons are very low density hollow phenolic spheres. The 
mixture was thoroughly blended with the Expancel being added as the last 
ingredient and then placed in a tray. It was covered with a film of 
polythene and stored at 25.degree. C. for 4 days. After this period it was 
powdered and possessed a Kofler Heat Bank melting point of approximately 
65.degree. C. After 700 days storage at normal ambient temperature the 
melting point had increased to 80.degree. C. and no sintering had 
occurred. 
A similar experiment with a tube filled with the powder was carried out as 
an in Example 9. In this case the powder melted and flowed somewhat during 
the heating cycle, but then expanded and overfilled the tube when fully 
cured after 60 minutes at 120.degree. C. The initial powder had a volume 
filling density of 0.4 grams per cubic centimetre and the well structured 
cured foam a density of 0.3 grams per cubic centimetre. 
EXAMPLE 11 
The following mixture was produced: 
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diglycidylether of Bisphenol-F 
50.0 parts by weight 
diglycidylether of tetrabromobisphenol-A 50.0 parts by weight 
aminobenzene 5.4 parts by weight 
44' diamino diphenyl methane 7.7 parts by weight 
Anchor 1040 3.0 parts by weight 
44' oxybis benzene sulphonylhydrazide 1.0 parts by weight 
fumed silica 6.4 parts by weight 
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Anchor 1040 is a coordination complex of boron trifluoride marketed by 
ANCHOR Chemical Co. 
The Bisphenol-F and tetrabromobisphenol-A resins were melted together at 
100.degree. C., and when mixed, the 44' diamino diphenyl methane was added 
with rapid stirring until dissolved and the whole blend then quickly 
cooled to 22.degree. C. The remaining liquids and solids were added with 
thorough stirring and the mixture was placed in a released tray. After 
five days the blend was heated to 40.degree. C. for four hours and was 
then broken and powdered. It possessed a Kofler Heat Bank softening 
temperature of around 60.degree. C. After six months the softening point 
increased to 74.degree. C. On heating to 180.degree. C. the powder 
coalesced and foamed and yielded a strong thermoset product after curing 
for two hours at 180.degree. C. 
EXAMPLE 12 
A composition identical to Example 9 was prepared, other then the fumed 
silica level was reduced to 4.5 parts per hundred parts of resin by 
weight. This product was powdered and sieved to a particle size range 
between 200 and 800 microns. 
This product was applied to clean steel rods, heated to 120.degree. C. by 
the fluidised bed technique. The powder melted and adhered to the rods and 
after curing for 30 minutes at 120.degree. C. gave a smooth, strong foamed 
coating. A similar experiment carried out with the rods heated to 
200.degree. C. gave a coating which was foamed and adhered without any 
extra curing. 
As may be seen from the foregoing examples, this chemical approach to the 
production of curable optionally foamable epoxy powders employs conditions 
much less rigorous than the method of Hot Melt Mixing solid resins with 
hardeners, which require mix temperatures of around 100.degree. C. or 
frequently above. 
With the current invention, in many cases, the epoxy resin blends are 
liquid at 22.degree. C. and the solidifying reaction takes place at the 
same temperature. 
If further heating is required to obtain a stable pourable powder at 
22.degree. C. or thereabouts it rarely needs to be above 
50.degree.-60.degree. C. 
The simplicity and mildness of the approach to making these epoxy powders 
enables the incorporation of a wider variety of heat sensitive additives 
including hardeners and accelerators than is possible with the Hot Melt 
method and yields powders with outstandingly long shop floor temperature 
storage times. 
The use of temperatures above 60.degree. C. to obtain suitable solids and 
powders is only necessary to increase speed or throughput in production. 
It will be clear from the examples that most of the compositions of matter 
disclosed here could be cast into specific shapes rather then ground into 
powder if required, or that the powders could be melted or sintered into 
specific shapes as well. It will also be clear that the cured products 
could find use as adhesives, encapsulants, insulating materials and 
mouldings as well.