US1981514A - Process for the production of press-molding masses by condensation of phenols with formaldehyde or substances that yield formaldehyde - Google Patents

Description

Patented Nov. 20, 1934 raocEss' r-oa 'rnn raonuo'rron. or

PRESS-MOLDING MASSES BY CONDENSA- TION OF PHENOLS WITH FORMALDE- HYDE on. SUBSTANCE-S- THAT YIELD FORMALDEHYDE many, assignor Max Koebner, Ludwigshafen-on:the-Rhine, Ger-,

of Germany to F. Rascln Ludwigshafen-on-the-Rhine, Germany, a firm G. in. b. H

No Drawing. Application February 24, 1933, 3511.1 No. 658,434. In Germany February 27,

-6Claims.

The subject matter of the invention is a process for the production of press-molding masses by condensation of phenols with formaldehyde or substances that yield formaldehyde.

Press-molding masses consisting of products of the condensation of phenols with formalde hyde have already been abundantly prepared, but

the masses, that have mostly been employed, of

resoles and filling agents had the disadvantage.

that the properties of the pressed bodies were unfavorably afiected by the filling agents-e. g., when using wood as filling agent, by attraction of water, and, in the caseof other filling agents, by deterioration of the external condition. Above all, it has been impossible to obtain glassclear products. 4 The employment of resoles without filling agents is impossible on account of their easy ,fusibility. i

It is true that it has already been propose to convert the resoles by hardening more or less completely into resitols and only to press this product. No faultless results, however, have hitherto been obtained. It is true that in certain circumstances glass-clearproducts could be obtained, but they had considerable defects.

A press-molding mass must fulfil the following requirements:

(1) Great velocity of hardening,

(2) Correctly proportioned fluidity which depends on the one hand on the viscosity and, on the other hand, on the velocity of hardening and is determinative of the ability to be pressed, especially for the correct filling out of the molds,

(3) Suflicient stability of shape of the finished pressed piece at 160-180 C.

Now it has been found that a press-molding mass, which fulfils all these requirements, can be obtained only on observing quite definite conditions in the manufacture, which, although they are partially known per se, have not hitherto been employed together in the correct manner.

In the first place, the initial material must have a definite .composition. It has been recognized that only such press-molding masses are usable, in which, to each molecule of phenol, a total of more than 1 preferably 2, molecules of formaldehyde or the corresponding quantity of agents that give methylene groups and split 01! formaldehyde are employed; It is immaterial whether,-in the production of the resins, one starts with phenol and combines this with the necessary quantity of formaldehyde, or whether tity of formaldehyde, or whether, novolaks arecombined with hexamethylene tetramine or with the necessary quantity of formaldehyde or with both together. It is only essential that-in the initial resin more than 1 preferably 2, molecules of methylene groups are employed to 1 molecule of phenol. The basis of this requirement lies in the knowledge that only in this way can pressed bodies be obtained which when hot possess the stability of shape that is necessary for the press technician, because press-molding= massesv which are made of formaldehyde and phenols in the proportion of less than about 1% .molecules of formaldehyde to 1 molecule of phenol and which are free from filling agents, give pressed bodies which are too soft.

Even on observing the proportions stated, a v usable press-molding mass could not be obtained.

For this purpose, the resin must be hardened to such a degree that, in the finely powdered condition, it does not sinter even at a tempera- ,ture of about '70 to 100 C., but it must not become too firm because it would then not possess the necessary fluidity.

' The hardening methods hitherto proposed are, especially in connection with a phenoplastthat hardens 'as rapidly as the present one such as it is essential for it to be for fulfilling'the require-' ment 3, quite inapplicable, because the hardening cannot be retained at the suitable condition.

To obtain the correct hardening, the fusible resin that is obtained by condensation of the initial substances in such a proportion that more than 1 molecules of methylene groups are employed to 1 molecule of phenol, must be hardened at a moderate temperature, with supervision of the progress of the hardening or of the diminution of the fluidity, until the solidified resin gives a powder that does not sinter at about to 100 C. The observation of the correct temperature during the hardening is advantageously effected by filling flat molds, whose thickness should not exceed about 10 cms., with the resin and warming them in a liquid bath, preferably in a water bath, at about 50-70? C. In the case of thickermolds, the

heat of reaction produced on hardening would not be capable of being carried away sufllciently rapidly and the resin would, at least in'the middle of the mold, very rapidly become quite hard and unusable. The same disadvantage would occur it higher temperatures than about 70 were chosen for the heat of the water bath. The employment of a water bath is to be preferred, because, in an air bath for example, which,

although it can act in a heating manner, cannot also act in a cooling manner, an undesirably rapid and uncontrollable hardening of the resin could easily occur.

With these precautionary measures, there is obtained a gradual hardening of the resin which extends over some days. In order that the limit of hardening that is favorable for the object in view shall not be exceeded,-the progress of the hardening must be constantly supervised. As a means for this purpose, a steel needle maybe used which, loaded by a weight, penetrates more slowly into the resin as it becomes harder. The

' hardening of the resin is stopped as soon as the 15 velocity of the penetration of the steel needle has fallen to a certain degree that is determined by experience.

Instead of the hardening, the decrease of the fluidity can be supervised, the determination of which is advantageously effected by Krahls method (Elektrotechnische Zeitschfift, 1931,

page 439).

By means of continuous supervision of the resin, one is in a position to determine exactly the point of time at which the resin has reached the high melting point that is necessary for the further treatment, while maintaining a fluidity that is sufiicient for the pressing. If hardening is carried on for a longer time, one would be in a position to ascertain with the same method the gradually occurring deterioration of the fluidity. In this manner one has an infallible means at hand of controlling the progress of the hardening process and of protecting oneself from defective results.

However, even such a resin would still be unusable for the object aimed at. The resin may, in accordance. with its method of manufacture, contain water, ammonia or both, and these would detrimentally affect its compressi bility as well as the appearance of the pressed bodies and their usefulness. The hardened resin is consequently pulverized and the powder is then freed from water, ammonia and other volatile substances, preferably by heating at temperatures between about 80 and 100 C. and in vacuo.

Example 1 A resole is prepared in a known manner from 940 parts of pure phenol, 1000 parts of 30% formaldehyde and 14 parts of hexamethylene tetramine, and a filtered solution of 230 parts of hexamethylene tetramine in 230 parts of water is then absorbed. This mixture is freed from water by vacuum distillation, the temperature gradually rising to C. The mass is kept in vacuo for three more hours at this tempera- I ture.

The yellow resin of the consistency of honey that is obtained in this manner is now poured into metallic molds which are 60-100 cms. deep, 15-20 cms. wide and 6 up to a maximumof 10 cms. thick. -The molds are suspended in a water bath at 60 C. It can be observed, on a thermometer whose mercury bulb is placed in the centre of the resin, that the temperature gradually rises to 70 C. on account of the reaction which occurs. The constantly progressing hardening is followed with an instrument which is constructed similarly to the known Vikat needle. It consists of a steel needle with a cross-sectional area of about 2 square millients and then examined as to its fluidity by the aforesaid Krahls method. Experiments have shown that a fluidity of 100 to 200 mms. at a pressure of 300 kgs. per sq. cm. corresponds, with an accuracy that is sufficient for'practical purposes, to the degree of hardness determined in the manner stated with the Vikat needle.

As soon as the resin shows the correct nature as determined in oneof the manners stated, the molds with the resin are transferred from the warm water baths into cold water baths. The cooled resin is converted into a fine powder and is kept for from 1 to 2 hours at a temperature of 70 to 100 C. in vacuo in a vacuum drier, so that the water and ammonia contained in the resin are evaporated. A powder prepared in this manner gives, on pressing at 160 to 180 C. pressed articles which can be pushed out of the mold without becoming deformed andare'yellow without further coloration and clearly transparent.

Example 2 Example 3 1000 parts of phenol, 1000 parts of formaldehyde and 230 parts of hexamethylene tetramine are heated for 2 hours at 60 C. It is also possible to use more formaldehyde and correspondingly less hexamethylene tetramine or vice versa. The water is then distilled off with a good vacuum and the resin is heated until it reaches a temperature of 60 C. Thereupon, the resin is kept for a further 2 to 3 hours at 60 C. and is then. worked up further as in Example 1.

Larger quantities of formaldehydeand agents which split off formaldehyde may be employed in the examples. Instead of phenol, suitable cresols or other phenols may be employed. If desired, the temperature in the hardening may be kept somewhat lower than 50 C. or somewhat higher than 70 C., the former giving a retardation and the latter an acceleration of the hardening process. Instead of the water bath there may be employed another liquid bath or, with careful working, an air bath. Instead of the Vikat needle and Krahls method, other supervising methods for the progressing hardening may be employed. The .freeing of the powdered resin from volatile substances may also be effected at a lower temperature and without vacuum.

There can be added to the resin, at any desired stage during the manufacture, l to. 5% of stearic acid and other flowing agents for the purpose of increasing the fluidity. There can also be added to the resins small quantities of salicylic acid or other carboxylic acids of the aromatic series which, in a quantity of up to 10%, have the property of rendering any too large a quantity of water, which may be present in the finished products and which, in certain circumstances, would produce a turbidity, harmless in this direction. Any desired quantities and kinds of organic and inorganic dyestuffs may also be added to the resins.

Without admixture of any kind, the pressmolding masses produced in the above manner, give, on being worked up under pressure and heat, pressed bodies which are clearly transparent and colorless or of a yellow color.

The above press-molding masses may be employed for the production of all kinds of pressed articles for electrotechnical, household, orna-'- mental and fancy purposes. Pressed bodies from masses according to the above process possess an excellent power of resistance to water.

I claim:--

1. A process for the production of press-moldingmasses by condensation of phenols with formaldehyde, comprising condensing the initial substances, in such proportions that more than 1 molecules of methylene groups are employed to 1 molecule of phenol, into a fusible resin, hardening said fusible resin in layers which do not exceed 10 centimeters in thickness at a temperature ranging from'about 50 to about 0., with supervision of the progress of the hardening until the solidified resin gives a powder that does not sinter at about '70 to 100 0., pulverizing the hardened resin, and freeing the powder from volatile substances.

2. A process for the production of press-mold-' ing masses by condensation of phenols with formaldehyde, comprising condensing the initial substances in such proportions that more than 1 molecules of methylene groups are employed to 1 molecule of phenol, into a fusible resin, hardening said fusible resin in layers which do not exceed 10 centimeters in thickness at a temperature ranging from about 50 to about 70 0., with supervision of the diminution of its fluidity, until the solidified resin gives a powder that does not sinter at about 70 to 100 C. pulverizing the hardened resin and freeing the powder from volatile substances. 3. A process for the production of press-mold ing masses by condensation of phenols with formaldehyde, comprising condensing the initial substances, in such proportions that more than 1 /2 molecules of methylene groups are employed to 1 molecule of phenol, into a fusible resin, hardening said fusible resin in layers which do not exceed 10 centimeters in thickness at a temperature ranging from about 50 to about 70 0., with supervision of the progress of the-hardening, until the solidified resin gives a powder that does not sinter at about 70 to 100 0., pulverizing the hardened resin, and freeing thepowder from volatile substances by heating at between about 80 and 100 C. and in vacuo.

4. A process for the production of press-molding masses by condensation of phenols with formaldehyde, comprising condensing the initial substances, in such proportions that more than 1 molecules of methylene groups are employed to 1 molecule of phenol, into a fusible resin, hardening said fusible resin in layers which do not exceed 10 centimeters in thickness by heating it at about .60 to 70 C. with supervision of the progress of the hardening, until the solidified resin gives a powder that does not sinter at about'70 to 100 0., pulverizing the hardened resin, and freeing the powder from volatile substances.

5. A process for the production of pressmolding masses by condensation of phenols with formaldehyde, comprising condensing the initial substances, in such proportions that more than 1 molecules of methylene groups are employed to 1 molecule of phenol, into a fusible resin, hardening said fusibleresinin layers which do not exceed 10 centimeters in thickness by heating it at about 60 to 70 0. in said form. of layers not exceeding 10 cm. in thickness, in a liquid bath, with supervision of the progress of the hardening, until the solidified. resin gives a powder that does not sinterfat about 70 'to 0., pulverizing the hardened resin and freeing the powder from volatile substances.

6. A process for the production of pressmolding masses by condensation of phenols with formaldehyde, comprising condensing the initial substances, in such proportionsthat more than 1 /2 molecules ofmethylene groups are employed to 1 molecule of phenol, into a fusible resin, hardening said fusible resin in layers which do not exceed 10 centimeters in thickness by heating it at about 60 to 70 0., with supervision of the diminution. of its fluidity, until the solidified resin gives a powder that does not sinter at about '70 to 100 0., pulverizing the hardened resin and freeing the, powder from volatile substances.

. MAX KOEBNER,