Moulding materials

An amino-formaldehyde moulding composition is made by compounding together PA0 an aqueous amino-formaldehyde resin solution to provide 0 to 90 percent by weight of the resin component of the composition, filler to make up 20 to 60 percent by weight of the moulding composition and PA0 UF resin which had a low degree of condensation, is solid at room temperature, contains a modifier and makes up 4 to 80 percent by weight of the moulding composition. The moulding compositions themselves are also claimed.

This invention relates to moulding materials made from amino-formaldehyde 
resins, and particularly but not exclusively to such materials made from 
urea-formaldehyde resins. 
Moulding materials made from urea-formaldehyde resins are well-known and 
have been in widespread use for many years. However, it has proved 
difficult to prepare materials which are suited to injection-moulding, 
especially when using urea-formaldehyde resins. 
It has also been proposed in UK Pat. No. 1,390,370 to manufacture solid, 
low softening point resins by reacting together, in the absence of 
solvent, urea, paraformaldehyde and hexamethylene tetramine to produce an 
amorphous solid resin with a softening point within the range 60.degree. 
C. to 100.degree. C. and to use such solid resins to manufacture moulding 
materials. The drawback with this proposal is that the solventless 
reaction is difficult to control so that the product is not reproducible 
with the consistency needed for commercial use. The resin produced has a 
very irregular molecular distribution, containing substantial fractions of 
highly condensed materials, and subsequently unreacted products. 
We have now found a method of making amino-formaldehyde moulding 
compositions incorporating urea-formaldehyde resins which have a 
beneficial effect upon the moulding materials produced, and do not require 
resins to be made from hexamethylene tetramine and paraformaldehyde. 
Thus, according to the present invention there is provided a method for the 
manufacture of an amino-formaldehyde resin and filler in which the resin 
and filler are compounded together under such conditions as to leave the 
resin in a state in which it will flow and cure under heat and pressure 
and wherein the components of the composition which are compounded 
together comprise 
(a) an aqueous amino-formaldehyde resin solution which is used in an amount 
such as to provide curable amino-formaldehyde resin to make up 0 to 90 
percent by weight of the resin component of moulding composition 
(b) at least one filler in an amount such as to make up 20 to 60 percent by 
weight of the moulding composition and 
(c) a urea-formaldehyde resin which is solid at room temperature and which 
has a low degree of condensation and a softening point in the range 
50.degree. C. to 90.degree. C. and/or which is a product of reaction of at 
least, urea-formaldehyde and a modifier selected from the group consisting 
of organic amides, amino-triazines, reactive organic hydroxyl and reaction 
products of these compounds with formaldehyde, the solid resin making up 4 
to 80 percent by weight of the moulding composition. 
The aqueous amino-formaldehyde resin is preferably of the kind suitable for 
manufacture of moulding materials by the wet process. It is preferably a 
urea-formaldehyde resin, although other amino-resins may be used, and it 
may be a urea-formaldehyde resin into which another monomer has been 
reacted. The molar ratio of urea to formaldehyde is preferably in the 
range 1:1.1 to 1:1.7. 
The aqueous resin is used in the form of a solution or syrup to which the 
other ingredients may be added, and such a syrup preferably has a dry 
solids content in the range 50% to 75%. 
The filler which is used may be a mixture of fillers, and may be fibrous or 
particulate or a mixture of the two. Preferably the filler includes a 
cellulose filler, as is commonly used in amino-formaldehyde moulding 
powders. A particulate filler which is suitable is a precipitated cured 
melamine or urea-formaldehyde material such as those described in UK Pat. 
Nos. 1,422,158 and 1,529,053. 
The solid urea-formaldehyde resin is made by reaction of urea and aqueous 
formaldehyde with subsequent removal of water, for example as described in 
UK Patent Application No. 84 04758, and has a low degree of condensation 
in order that it may remain suitable for plasticization and moulding after 
being compounded into the moulding material. By the expression low degree 
of consideration we mean a degree of condensation less than 45%, degree of 
condensation being: 
##EQU1## 
where (1) is determined by acid hydrolysis with phosphoric acid followed 
by sulphite determination of liberated formaldehyde and 
(2) is determined by the ACC sulphite method. 
The degree of condensation of the solid resin may be as low as 25% but the 
preferred range is 30 to 43 percent. 
The compounding of the ingredients may be accomplished in one of several 
ways. For instance the filler may be added to the aqueous resin in the 
usual manner utilised in the wet process for making moulding powders, and 
the solid resin may be added along with the filler. Alternatively the 
aqueous resin may be used to impregnate the filler, and the mixture dried 
and ground, only then adding the solid resin. If no aqueous resin is being 
used the filler and the solid resin may be compounded dry by conventional 
means. 
In each case the usual additives such as pigments, curing agents, 
stabilisers, etc, may be included in the composition and compounded 
therein in conventional manner. 
Thus the present invention provides also a moulding composition comprising 
a curable amino-formaldehyde resin and filler in which at least some of 
the curable amino-formaldehyde resin is incorporated into the composition 
as a curable solid urea-formaldehyde resin having a degree of condensation 
which is in the range 25 to 45 percent. 
The solid urea-formaldehyde resin may contain as modifier a reactive 
organic hydroxyl compound, an organic amide or an amino-triazine compound 
such as melamine and/or the reaction products of these compounds with 
formaldehyde. The principal purpose of the modifier is to assist in the 
formation of a solid resin but compounds can be used for this purpose 
which also have useful effects on moulding compositions produced using the 
resin. Such compounds include p-toluene sulphonamide, sulphanilamide, 
acetamide and malonamide. 
Other compounds which are effective modifiers include succinamide, 
dicyandiamide, phenol, ethylene glycol, o-cresol and melamine-formaldehyde 
resins. Mixtures of modifiers may also be used. 
The total amount of modifier used is preferably such that units derived 
thereform will comprise not more than 4 percent by weight of the resin, 
more preferably not more than 2.0 percent. It is to be noted, however that 
when the modifier is an amino-triazine such as melamine, or a reaction 
product of such a compound with formaldehyde the amount of modifier used 
can be substantially greater eg up to 20 percent by weight of the resin, 
if desired although this is not normally preferred. If such greater 
amounts of these modifiers are used the amount will not usually exceed 10 
percent by weight of the resin. 
The solid urea-formaldehyde resin preferably has a molar ratio of urea to 
formaldehyde which is in the range 1:1.2 up to 1:2.0 and more preferably 
in the range 1:1.3 up to 1:1.6. 
In addition to the aqueous resin and solid resin mentioned above, other 
resins may be added to the moulding compositions of this invention in an 
amount of up to 20 percent by weight of the total resin in the 
composition. Resins which may be included must be compatible with the 
resins already mentioned and two particularly useful additive resins are 
polyester alkyd resins, often used with amino-formaldehyde resins in 
coating systems, and spray-dried melamine-formaldehyde resins which blend 
readily with the solid urea-formaldehyde resin. The latter are a 
particularly useful addition and will normally have a softening point in 
the range 70.degree. to 120.degree. C.