Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1985-04-11
1988-11-15
Schain, Howard E.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
525480, 525504, 528140, 528147, 528153, 528158, 26433112, 26433122, 524389, C08G 1410, C08G 1406, C08L 6134
Patent
active
047850736
DESCRIPTION:
BRIEF SUMMARY
This invention relates to moulding compositions, and is especially concerned with the provision of a novel series of easily handleable, low temperature and low-pressure curable resins which may be used for moulding, casting, in the preparation of bulk (dough) and sheet moulding compositions, resin injection, in gel coats, and in the manufacture of what are known in the art as "pre-pregs", both with and without the addition of fillers.
It is well known that phenols and substituted phenols can be reacted with aldehydes, e.g. formaldehyde, to give a range of thermosetting resins which are normally referred to as "phenolics". These resins are produced by partially condensing a mixture of the phenol and the aldehyde, suitably with the assistance of an alkali catalyst, to the stage at which a so-called "resole" resin, or A-stage resin, is formed. This resin is then shaped, e.g. in a mould to produce a moulded object or a surface coating or lamination, and its cure is completed by heating and/or catalytic effect. The manufacture and use of such resins are exhaustively described in the literature.
It is also known for various additives to be included in the resole, or indeed in the reactive mixture which produces the resole, before curing and such additives include, for example, fillers, pigments and plasticisers.
These phenol-aldehyde resins have achieved wide success in many fields of application, but suffer from certain disadvantages. For example, although neutral curing is possible, it is uneconomic since it takes a long time and requires high temperatures (e.g. 125.degree.-165.degree. C.) and elevated pressures (e.g. 300-1000 p.s.i.). For practical purposes, therefore, the resins must be acid-cured. The presence of an acid catalyst in the resin system places limitations on the choice of filler and reinforcements which may be used, since the acid will attack, for example, glass fibre, pigments and fire-retarding additives. The acid present may also attack and corrode the equipment being used, and can constitute a hazard to the operators. Furthermore, acid may leach out of the final moulded product, e.g. due to the action of water thereon, and this may attack, for example metals, concrete and other materials in contact with, or in the proximity of, the moulded or foamed product.
A further disadvantage of known phenol-aldehyde resins is their lack of colour stability. This is an inherent characteristic of commercial phenolics, and in any event discolouration of phenolics is greatly accelerated by the presence of acidity in the moulding.
Resins are also widely known and used which are made by a similar reaction to that described above, but involving an amino compound and aldehydes, for example melamine and/or urea and formaldehyde. Such resins are known in the art as "aminoplasts", and are widely used in high pressure moulding compounds. Conventional aminoplasts tend to be very brittle, however, are usually high melting point powders, and are not very reactive at pH 7.0 or above. Thus, in commercial use the aminoplast moulding composition must necessarily contain a high proportion of reinforcing filler, high temperatures and pressures must be used to provide flow and fast cure and prevent gassing; and acid or latent acid catalysts are often used for curing, with the attendant difficulties mentioned above in connection with phenolics.
Both phenolics and aminoplasts may be formed into foamed products, and UF foams are especially to be noted. Such foams also prevent problems, however. Thus, a high proportion of water is necessary in the resole to produce flow of the resin and thus cure. The resins tend to be brittle. The products tend to shrink, due to polymerisation and loss of water, added or formed. Acid or latent acid catalysts are normally used for the cure (see above), and the final products are weak and not chemically resistant.
It is an object of the present invention to provide a novel series of thermosetting resinous materials, suitable as moulding compositions, which do not suffer from the drawbacks of th
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Farkas Robert
Hohmann Lothar M.
Polymer Tectonics Limited
Schain Howard E.
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