Subject of this invention is method for manufacturing melamine resins and plastics, the melamine resins and plastics so manufactured. State of Technique Many curable melamine derivatives are known in the art, however most of them are produced in form of aqueous solution, for example impregnetive formaldehyde-melamine resins, or dissolved in organic solvents for example esterified coating -type resins. Other curable melamine derivatives, although they can occur in solvent-less form as for example hexamethoxymethylmelamine, their manufacturing process is complex, uneconomical and ecologically disadvantageous. To produce hexamethoxymethylmelamine three-fold excess of formaldehyde in form of formaline has to be used with respect to the melamine, or 18 ol of formaldehyde per mol melamine (see irpsza, Brzezinski "Aminoplasty", WNT, Warszawa 1970 p.95) Two thirds of the formaldehyde is discharged unused to sewage. On the other hand, to produce

hexamethoxymethylmelamine from hexahydroxymethyl- melamine almost two fold excess of methanol over the stoichiometric ratio has to be used where again about 60 % of the methanol is discharged unused to sewage (ibid, Aminoplasty, sht 342) . It has been extremely desirable to find a simple and cost-effective method for manufacturing liquid, water-less and solvent-less reactive derivatives of melamine and of melamine resins, readily processable into melamine plastics. Unexpectelly, it was found that products of reaction of formaldehyde with chemical compounds containing active aliphatic C-H bounds, are solvents for melamine. Disclosing an Invention

The essential feature of this invention lies in the fact that in 100 parts by weight of reactive solvent containing water not more than 30 % by weight, being a compound or mixture of compounds of molecular mass not above 500, containing hydroxymethyl groups, their ether derivatives, semiformalε or formals, at reaction temperature within 60°C to 180°C, 10 to 200 parts by weight of melamine is dissolved, and the reaction mixture thus formed is held in the reaction temperature

until the desired uniformity, viscosity, softening point or crosslining is achieved, the said reactive solvents include products of reaction with formaldehyde of compounds containing of bonds C-H and sensitizing them groups located in the position alfa, preferably ketones, aldehydes, nitrocompounds and erivatives thereof. Auxiliary- agents may be admixed to the resin prior to crosslinking and them bringing the mixture to the desired degree of crosslinking.

The said auxiliary agents may include catalysts or initiators, antistick additives, fillers, foamers and other agents. Melamine resins manufactured to the invection may contain diverse groups bound via aliphatic carbon atom, including the following: active hydroxymethyl groups, their ether derivatives, semi-formals and/or formals, all activated by functional group containing unsaturated bond(ε) proferably carbonyl groups located in the position alfa, and one or more hydrogen atoms in melamine amine groups substituted by a sequence of at least two aliphatic carbon compounds, preferably bound to the unsaturated-bond containg group, preferably the carbonyl group.

Melamine plastics manufactured to the invention feature at least two hydrogen atoms in melamine molecule amine group substituted with sequences of

75 at least two aliphatic carbon atoms, alternatively bound to the unsaturated-bond containing group, preferably the carbonyl group.

Melamine resins manufactured to the invention can be modified with reactive-group compounds, capable

80 of reacting with melamine-containing reaction mixture. Through modification of melamine resin with compound carrying at least one such group and double-unsaturated bond, preferably acrylamide, modified melamine resins are produced, curable by

85 polymerization preferably radical-type polymeri¬ zation. By modification of melamine resin, to the invention, with a compound or compounds containing at least one, preferably two reactive groups and aliphatic chain, preferably polyether chain,

90 melamine resins and plastics of improved flexibility can be produced. By foaming followed by solidification of the said reaction mixture of melamine with reactive solvent foamed plastics can be produced.

95 Solubility of melamine in reactive solvents is low at room temperatures, butit rises appreciably only

above 60°C and generally the higher temperature, the higher the solubility is.

The higher temperature is, the faster the

100 reactions and polyreactions in the reaction mixture proceed. At elevated temperature polyreactions proceed also in the reactive solvent itself, but the process is accompanied by decreasing melamine solubility in it. Usually it

105 is preferable to preheat the mixture rapidly to as high temperature as possible, to obtain melamine solution, or melamine derivative solution, of as high as possible concentration, followed by cooling, if desired. A limiting factor on the

110 maximum, acceptable heat temperature is rate of the polyreaction at elevated temperature, possibly accompanied by decomposition of the polymer formed. The polyreaction can be retarded or terminated at any chosen stage, by cooling the reaction mixture.

115 Reactive solvents may contain volabile components, e.g. some water or other more or less volabile compounds. Volatile compounds may also be formed during polyreaction and in decomposition of polyhydroxy compounds in presence of melamine at

120 elevated temperature. All the volatile components

can be distilled off (vaporized) in the melamine dissolution operation carried out at temperatures above their boiling points under these conditions. Even if such components are initially present or

125 are formed during melamine dissolution, finally at the elevated temperature 100-140°C waterless solution is obtained, free of volatile compounds, consisting practically of polymer-forming substances. Initially these polymer-forming

130 substances are in liquid state at the reaction temperature, but their viscosity is gradually rising with time until the body of the mixture solidifies at a rate depending on temperature, i.e. the higher the temperature is the faster the

135 viscosity increases and the resin solidifies eventually.

To speed up the polyreaction or curing process speed-up agents (catalysts, particularly acid-type) or initiating agents (particularly

140 radical-type) may be admixed into melamine solution, or into reaction mixture containing melamine and/or its derivatives. The modifier additives optionally admixed into melamine solution or melamine-containing reaction

145 mixture, contain reactive groups preferably

carbamate, amide or hydroxyl groups able to promote reacting the substances with reaction mixture. The modifier additives, containing functional

150 groups reactive with respect to the reaction mixture, and unsaturated bonds, preferably acrylamide, are used at proportions within 3 to 30 weight parts per 100 weight parts of reaction mixture.

155 Liquid sulution of melamine or melamine-containing reaction mixture can be formed in any convenient way to form product shape then to effect solidification thereof, preferably by curing. The major advantages of the method to this invention

160 include:

- readiness and quickness of preparation of solutions of melamine, its reactive derivatives, resins and plastics in practically water-less and solvent-less way,

165 - production of liquid semiproducts of polymer- forming substance content 100 % or close to 100 % by weight, which is advantageous processing point of view as well as economical andecologically acceptable,

170 - optional modification of the final product

properties manufactured to the invention through the use of others reactive additives or substances, - reactive solvents of melamine to the invention are in liquid state ^' and stable at room

175 temperature, and are relatively not expensive as the starting materials for their manufacture are generally cost-effective and their manufacturing process is relatively simple. Executies of Invention

180 The method to the invention is presented on examples of its embadiments, without limiting the potential extent of its applications.

Example I

100 g anhydrous liquid trihydroxymethylacetone,

185 pH 7.8, is rapidly preheated to 100°C and 46,5 g powdered melamine is added to it while vigorously stirring. The melamine dissolves to form clear yellow-orange viscous solution of pH 8.2. This solution is stable for over 24 hours at room

190 temperature, and cures at elevated temperatures within 100 minutes at 65°C, within 10 minutes at 120°C or within 3,5 minute at 150°C to form insoluble non-melting solid product. For comparison, in glycerine 7,7 g melamine can be

195 dissolved at 100°C but neither the dissolved material nor the solution do harden.

Example II

100 g trihydroxymethylacetone batches of various pH, are rapidly heated to 100, 125 and 150°C 200 respectively and 46,5 g powdered melamine is added to each while vigorously stirring.

The melamine dissolves to form clear viscous solution.

Gelation time of the particular solutions, 205 differing in pH, at various temperatures are given in the table herebelow:

210

215

220 Example III

100 g anhydrous, i.e. dehydrated by vacuum distillation, mixture of di-and trihydroxymethyl- acetones of pH 6.5 is preheated within 10 minutes to 100°C and 26,7 g powdered melamine is added to

225 it while vigorously stirring. The melamine dissolves to form clear viscous solution. This solution is stable for over 24 hours at room temperature, and cures in 3 minutes at 100°C, at pH 7.8.

230 Example IV

100 g liquid anhydrous mixture of di- and trihydroxymethylcetones of pH 8.5 is preheated within 10 minutes to 100°C and 46g powdered melamine is added while vigorously stirring. Upon having dissolved the melamine to form clear liquid

235 the solution is cooled to 30°C and diluted by addition of 100 g ethylether, while vigorously stirring. The mixture separated to form two different liquid phases. The bottom phase was drained and residual ethylether is removed from it by distillation, (vaporization) to obtain 130 g

240 reactive melamine derivative.

The top phase upon distilling-off the residual ethyether, yielded 16 g of aqueous solution of unreacted hydroxymethylacetones. The recovered hydromethylacetones can be re-used in dissolving

245 of melamine. Example V

30 g melamine is dissolved in 100 g tetrahydroxymethylacetone preheated to 150°C, while vigorously stirring. Immediately upon melamine dissolution the solution

250 is placed into mould at 150°C wherein the mixture cures and solidifies to form solid product within few minutes. Example VI 100 g trihydroxymethylacetone is mixed with 80 g

255 melamine in open vessel while vigorously stirring, and is rapidly heated within 12 minutes from 20°C to 140°, to form homogenous clear liquid mass

which upon immediate cooling to room temperature solidifies to form hard, brittle thermoset

260 product.During the heating total 18 g volatile components evaporated from the solution. The reaction product cures in 1-2 minutes at 150°C. The product contains about 50 % melamine.

265 Example VII

100 g trihydroxymethylacetone is mixed with 35 g powdered melamine and preheated, while stirring, to 120°C; then upon cooling down to 100°C 30 g acrylamide is added and dissolves while stirring,

270 followed by cooling down to 85°C, adding 0.3 g benzoil peroxide, while stirring. The resultant product has anaerobic properties, remains liquid at 100°C as long it is vigorously stirred in presence of air, and when stirring

275 stopped, it immediately solidifies with crosslinking. Example VIII

100 g of a mixture of di and tri-hydroxymethyl acetone is mixed with 30 g acrylamide and

280 heated while stirring until complete dissolution at 60°C; with undisrupted stirring the solution is heated in presence of air to 100°C, 35 g melamine added and heated on to 130°C until the melamine

285 dissolves. The resultant clear solution is cooled down to 85°C and 0.2 g benzoil peroxide added and dissolved by stirring. Upon heating on to 120°C the mixture cures immediately to form hard non-meltable insoluble product.

290 Example IX

30 g powdered melamine is added to lOOg trihydroxymethylacetaldehyde and is heated within 3 minutes to 145°C while vigorously stirring, to form clear solution which cures at that

295 temperature within 3 minutes. Example X

35 g melamine is added to 100 g trihydroxymethylacetaldehyde monosemiformal of pH 9 (determined colorimetrically) , and heated to

300 160°C while vigorously stirring. At 145°C the mixture became clear and at 160°C it cured. Example XI

25 g powdered melamine is added to 100 g trihydroxymethylnitromethane, and while vigorously

305 stirring the mixture is heated to 120°C at which temperature the melamine dissolved. On further heating to 125°C the mixture undergoes foaming and curing to form tan rigid solid foamed product of density 100 kg/m .

310 Example XII

30 g powdered melamine is added to 100 g 80 % aqueous solution of trihydroxymethylnitromethane, and while vigorously stirring the mixture is heated to 125°C. The melamine dissolved to form

315 clear homogenouse solution; total 35 g volatile components has distilled off (vaporized) during the heating; 95 g resinuous foamy product is obtained, which cured within 2 minutes to form tan rigid solid foamed product of density 80 kg/m .

320 Example XIII

110 g melamine is added to 100 g 90 % aqueous solution of tetrahydroxymethylcyclohexanone and while vigorously stirring the mixture is rapidly heated to 140°C to form clear solution,- Total

325 20 g volatile components distilled off (vaporized) during the heating, and melamine content in the resultant resin is 60 % wt. When heated on to 150°C the resin cured within 1 minute. Example XIV

330 70 g powdered melamine is added to 100 g tetrahydroxymethylcyclohexanone and while vigorously stirring the mixture is rapidly preheated to 120°C to form clear solution; on further heating the solution gelates at 150°C

335 within 2 minutes; upon alcalization with 0.15 g solution NaOH it gelates within 1 minute and upon acidification with 0.1 g paratoluenesulphonic acid - within 12 seconds. To illustrate the melamine resin to the invention

340 a possible route of one many possible reactions resulting in formation of the said resin, based on the use of melamine and trihydroxymethylacetone as substrate, is presented schematically herebelow.

NH.

NH.

N ✓ ^C \

-H 0