DE1147383B - Process for the preparation of novolak type condensation products - Google Patents

Description

Process for the preparation of novolak-type condensation products It has long been known that heterocyclic aldehydes, such as furfural, with phenols Form resinous condensation products. The condensation can be basic or acidic substances are catalyzed. In practice, however, only basic ones have been used so far Substances such as sodium hydroxide are used.

Acid catalysts always resulted in considerable polymerization. It is believed that this is due to the activation of the double bonds which are present in the molecule when the condensation with the phenol takes place. It therefore proved extremely difficult to obtain novolak-type resins from phenols and to produce heterocyclic aldehydes.

It is possible to produce condensation products from phenols and formaldehyde to produce the novolak type, in which the substituent groups predominantly in the o-position to the phenolic hydroxyl groups. These condensation products have a higher rate of hardening than the usual novolak-type products. They were made using oxides and salts of certain electropositive metals produced as catalysts.

The invention relates to a process for the preparation of condensation products of the novolak type by condensation of a monohydric or dihydric phenol in which at least two of the o or p positions to the phenol group are unsubstituted, or a mixture of these phenols with an aldehyde in general formula in which X is an oxygen or sulfur atom and Y is a hydrogen atom or an alkyl or alkylol radical with up to 4 carbon atoms, which is characterized in that not more than 1 mole of aldehyde per mole of phenol under practically anhydrous conditions in the presence of an electropositive metal bivalent state with an acid which has a dissociation constant k of 1.7-10-2 to 1.0 10-6 at 25 ° C, is heated. In this way, products with exceptionally interesting and valuable properties are obtained.

Given the differences between formaldehyde and furfuraldehyde it is surprising that a reaction that was previously so difficult to carry out is so smooth can take place.

For the preparation of the resinous condensation products according to the invention phenol, alkyl-substituted phenols, alkenyl-substituted phenols and are suitable dihydric phenols. The substituted phenols can be divided into two different groups be subdivided. The first group includes the phenols that are present in either or both m-positions to the phenol group contain a substituent whose three o- and p-positions are therefore unsubstituted in this group. The second group consists of the phenols, one substituent in one of the o- and p-positions to the phenolic hydroxyl group in which only two of these positions are unsubstituted. Examples for phenols belonging to the first group are m-cresol, 3, 6-xylenol, m-ethylphenol, m-isopropylphenol, cardanol, hydrocardanol and urushiol. Examples of phenols of the second group are o- and p-cresol, o- and p-ethylphenol, 2, 3- and 2, 5-xylenol, o- and p-isopropylphenol, o- and p-isopropenylphenol and p-tert-butylphenol. Even In the dihydric phenols, at least two of the o- and p-positions should be relative to the phenolic hydroxyl groups be unsubstituted. Can be used either those dihydric phenols in which two phenolic hydroxyl groups in one single aromatic Core are present, e.g. B. resorcinol, or those in which two monohydric phenol nuclei are replaced by an aliphatic hydrocarbon radical are connected, e.g. B. the Diphenylolmethane and the Diphenylolpropanes. Mixtures too of phenols of the type mentioned above can be used, in particular Mixtures of isomeric phenols with 7 or 8 carbon atoms, such as, for example can be obtained from coal tar fractions.

Suitable aldehydes for the process according to the invention are furfural, a-thiophenaldehyde and its a-substituted homologues which contain an alkyl or alkylol radical containing 1 to 4 carbon atoms, e.g. B. α-methylfurfural and α-hydroxymethylfurfural.

The salts are used as catalysts in the process according to the invention of electropositive metals in the divalent state with an acid that is a Dissociation constant k from 1.7-10-2 to 1.0-10-6 at 25 ° C is used. If the acid contains more than one ionizable hydrogen atom, the dissociation constant becomes of the first hydrogen atom. Of the inorganic acids, whose Salts that can be used include sulphurous acid and boric acid.

The organic acids whose salts are suitable are the aliphatic, aromatic and heterocyclic carboxylic acids. These acids can be in the aliphatic Chain or substituted in the heterocyclic nucleus. Of the substituted acids mention may be made of those having one or more halogen substituents or hydroxyl groups contained in the aliphatic chain, as well as those having a halogen or hydroxyl substituent contained in a position to the carboxyl group in the aromatic or heterocyclic nucleus. Examples of acids whose salts are suitable are formic acid, acetic acid, propionic acid, Butyric acid, isobutyric acid, monochloroacetic acid, a-chloropropionic acid, lactic acid, Benzoic acid, o-chlorobenzoic acid, salicylic acid and pyromucinic acid. Preferably be the salts of acids used, the dissociation constant k from 2.0-10-3 to 1, 0 10-6 have.

The metals whose salts are used as catalysts are all electropositive metals that form normal salts in the divalent state.

These include magnesium and the metals of group II B of the periodic Systems as well as the metals with ordinal numbers from 24 to 28, tin and lead. Preferred are cobalt, lead, magnesium, manganese, zinc and cadmium.

The amount of catalyst used can be within wide limits, however, amounts greater than 10 percent by weight based on the phenol or Phenolic mixture, no benefit with it.

Quantities below 0.5 percent by weight, based on the phenol or phenol mixture, usually give a sluggish response. Preferably from 1 to 5 percent by weight second hand. It is advisable to have a sluggish reaction at the temperatures used to avoid, otherwise the polymerization can become the predominant reaction.

The condensation products of the novolak type can according to the process be prepared according to the invention as follows: The phenol or

The phenol mixture, the aldehyde and the catalyst are placed in a reaction vessel introduced that with one or more coolers and preferably with an azeotropic Separator is equipped.

The catalyst can either be used as a finely divided solid in aqueous Solution or suspension introduced or formed in situ. The by heating the reaction taking place is inhibited by the presence of substantial amounts of water, so that work must be carried out under practically anhydrous conditions. The one in question Coming aldehydes, especially furfural, form azeotropic mixtures with water. The condensation takes place with the elimination of water. It is very convenient remove the water as quickly as it is formed, thus causing the condensation reaction can take place as quickly as possible. A certain excess of aldehyde is preferred about the amount to be condensed with the phenol used as a certain part is always lost when the water is removed from the system. How much is the excess depends on the effectiveness of the separation of the water from the aldehyde in the condenser and separator. If the reaction vessel is fitted with a condenser, through which a hot liquid kept at 95 to 109 ° C flows, this is how a large part of the aldehyde condenses. This part can be returned directly to the vessel while the non-condensed vapors are fed to a second cooler, which is kept practically at room temperature.

The organic phase of the condensate obtained in the second cooler can then separated from the aqueous phase and returned to the reaction vessel. It is also possible to condense the whole distillate in a reflux condenser, collect the condensate in an azeotropic separator and the organic phase to be returned to the reaction vessel. Another option can be a sufficient Excess aldehyde be present and the water-aldehyde mixture that passes over condenses, but cannot be returned to the reaction vessel. However, one of the two will first alternatives are preferred, since here the excess of aldehyde over that to be condensed Amount need not be more than 5 to 10 per cent.

When the reaction mixture is heated, distillation begins usually between 110 and 170 ° C.

The temperature at which reflux occurs tends to decrease when the water released is not removed. While the water from the reaction mixture is distilled off, the reflux temperature rises as condensation progresses gradually on. An exothermic reaction often sets in at which the temperature and the distillation can begin without external heating.

If this occurs, the supply of heat must be resumed, when the exothermic reaction subsides.

The condensation product according to the invention is very reactive, and there is a risk of gel formation if you change the temperature of the reaction mixture increases too much. It is therefore best to conduct experiments on a small scale, to determine the maximum temperature a batch can be heated to.

The lower the reactivity of the phenol and the lower it is The ratio of aldehyde to phenol, the higher the maximum temperature that the Batch can be suspended. For example, phenols are common in all o and p positions to the phenolic hydroxyl group or to the phenolic Hydroxyl groups are free of substituents, higher reactivity than phenols, which contain a substituent in one of these positions. The first group must reacted with a lower molar amount of aldehyde and / or to a lower one Maximum temperature can be heated during the condensation. For example, it is phenol implemented with a 0.7 molar proportion of furfural, the maximum temperature should be Do not exceed 190 ° C, while when using p-tert.-butylphenol with 0, 8 moles of furfural a maximum temperature of 210 ° C is permissible without the danger premature gel formation. When reached the maximum allowable temperature volatile substances present in the reaction mixture can be removed by gradually lowering the pressure while maintaining the temperature below 190 ° C.

The viscosity increases as the molar ratio of aldehyde to phenol increases of the formed resinous condensation product is higher. If you leave the viscosity rise too much, there is a risk of gel formation. The maximum amount of aldehyde that can be condensed with the phenol differs depending on the phenol. When phenol is condensed with furfural, the maximum amount of the latter is, which can be implemented, about 70 mole percent. When using a mixed xylenol fraction, which goes to 80% between 216 and 223 ° C, you can practically 100 mole percent Let furfural react with it.

When using the liquid from the peels of the fruits of the kidney tree, which has a molecular weight of about 300, the maximum amount of furfural is about 70 mol percent, when using p-tert-butylphenol practically 100 mol percent. The amount of aldehyde fed to the reactor can, as already mentioned, be greater, as stated above, as part of the removal of the water from the reaction mixture get lost.

By following the viscosity increase it can be determined when the aldehyde excess under reduced pressure, which is preferably 10 to 100 mm Hg absolute, must be removed. Conversely, there can also be enough additional Phenol are added, which react with the excess aldehyde present can. In all cases, at least 50 mol percent of the aldehyde must be reacted with the phenol.

The properties of the condensation products according to the invention are available in relation to the number of reactive positions present in the phenol used or the average number of these positions if a mixture is used, and the proportion of the aldehyde that has been reacted with it. By heating, in particular in the presence of suitable catalysts, all products can be cured. Products made from phenols or mixtures of phenols, on average in more than two o- and p-positions relative to the hydroxyl group or unsubstituted relative to the hydroxyl groups can easily be converted into the insoluble state if they are with an aldehyde or a substance that acts as a source of aldehyde, such as hexamethylenetetramine, or which contains methylol groups, such as a phenol-formaldehyde or phenol-furfural resole resin. or with a polymethylolurea or polymethylolmelamine. One Conversion into the insoluble state is also possible by heating with polyamides, such as dicyandiamide and melamine, with strong organic bases such as piperidine, with Friedel-Crafts catalysts or acid catalysts, such as sulfuric acid, p-toluenesulphonic acid, Ethyl hydrogen sulfate, and acid salts of sulfuric acid, such as potassium bisulfate.

They can also be converted into the infusible state Heating with organic and inorganic peroxides and persalts, e.g. B. the aroyl peroxides and the alkali and ammonium persulfates. You can in this form in powder form and used as binding resins for brake and clutch linings.

Condensation products of phenols that have a tertiary alkyl substituent or one or more alkyl or alkenyl substituents with a total of 10 to 20 Carbon atoms contained in the molecule are highly desiccating and semi-drying Compatible with oils and can be used for the production of paints, varnishes and enamels will.

Many of the condensation products are natural and synthetic Rubbers compatible and can after admixture to these and heating of the mixtures are also vulcanized.

The quantities given in the following examples relate to the Weight.

Example I 940 parts of phenol and 672 parts of furfural (molar ratio 0, 7) were introduced into a reaction vessel together with 20 parts of zinc peroxide. The peroxide slowly oxidizes the furfural in situ to pyromucinic acid and forms with it the zinc salt.

After heating to a reflux temperature of 164 ° C, the vapors were partly in a reflux condenser, through the jacket of which water at 98 to 100 ° C flowed, condensed. The condensate was immediately returned to the reaction vessel. The vapors emanating from the head of the jacketed condenser were separated into one condensed further cooler and passed into an azeotropic separator, in which the organic phase was separated and returned to the system, while the aqueous phase was discarded.

The reflux temperature gradually rose from 164 in 11 hours 194 ° C. Up to then 135 parts of a practically aqueous distillate had been separated off been. The pressure was carefully lowered to 30 mm Hg. After 30 minutes it was Temperature dropped to 130 ° C. 20 parts of a non-aqueous distillate were obtained, which consisted of a mixture of unreacted furfural and phenol.

As a product, 1250 parts of a novolak type resin were obtained, its softening point was 80 ° C., determined by the ring-and-ball method. The resin has been in a variety of solvents including the lower aliphatic Alcohols and ketones. Cyclohexanone and dioxane, soluble.

In another experiment the same amounts of phenol and furfural were used used together with 38 parts by weight of zinc acetate. The reaction was similar however, was completed in 3 hours. The product was similar.

When the product obtained using zinc acetate as a catalyst was ground with admixture of 10% by weight of hexamethylenetetramine, gelation occurred at 150 ° C. in 3 minutes. When this product was heated to 140 ° C with the catalysts listed below, gel formation occurred after the following times: Time Additive amount m hours o / o to Gel formation Without additives .................. - 3.5 15th 0- Sulfur 15 t 1, 25 Mercaptobenzothiazole .......... 2 J Piperidine 2 0.75 10 0, 25 Benzoyl peroxide 2 1.75 Aluminum chloride 2 1, 75 I) 2 1, 25 10 1, 25 Boron trifluoride-phenol complex ... 2 0, 25 p-Toluenesulfonic acid 2 0.25 Ammonium persulfate .......... 2 2, 0 Example 2 2200 parts of resorcinol and 1152 parts of furfural (molar ratio 0.6) were introduced into a reaction vessel together with 120 parts of lead acetate dissolved in 200 parts of water. The mixture was slowly heated to a temperature of 75 ° C. with stirring. After the constant-boiling mixture consisting of furfural and water had been distilled off, the heat supply was switched off and the reaction continued exothermically until a temperature of 125 ° C. with an initial boiling point of 110 ° C. was reached after 3/4 hours. The condensed distillate was passed into an azeotropic separator, from which the furfural layer was returned to the reaction vessel and the aqueous phase was discarded. 15 minutes after reaching 125 ° C, the temperature of the mass had fallen to 120 ° C. Heat was supplied again and the distillation together with the azeotropic separation started again at a temperature of 115 to 120.degree.

After a further 2 hours, the distillation had practically stopped. 1/2 hour later the resin was removed. It had a softening point of 80 ° C, determined by the ring-and-ball method, and an iodine number of 200 (determined according to the Wijs method).

Example 3 1330 parts of a commercially available xylenol fraction, which came from the coal tar distillation, passed to 80% between 216 and 223 ° C and about 35% of a mixture of 3,5-xylenol and m-ethylphenol and about 65 o / o consisted of other xylenol and ethylphenol isomers, together with 960 Parts of furfural and 38 parts of cadmium formate are placed in a reaction vessel and taken under Stirring heated to a reflux temperature of 162 ° C. The vessel was fitted with a reflux condenser provided, through which water at 98 to 100 ° C was passed. At the exit of this Another cooler was connected to the cooler to softening water vapor and to condense entrained furfural. The condensate was as in Example I in out an azeotropic separator.

4 hours after the start of reflux was the temperature of the batch increased to 220 ° C. Until then, 192 parts by weight of one was essentially aqueous Distillate has been collected. The pressure was now carefully reduced, and after a further 30 minutes, during which the temperature dropped to 180 ° C., became a resin with obtained a softening point of 107 ° C.

This resin had excellent compatibility with natural rubber. When used in conjunction with 10 weight percent hexamethylenetetramine, it had very good properties as a plasticizer and processing aid.

Example 4 1080 parts mixed cresols consisting of 40 to 42% from the m-isomer, to 2 to 3% from the o-isomer, remainder essentially p-isomer, were together with 960 parts of furfural (molar ratio 1) and 48 parts of manganese lactate into one with dephlegmator and azeotropic separator, similar to the examples 1 and 3, provided reaction vessel. The mixture was heated with stirring.

At 154 ° C., reflux began. After refluxing for 3 hours the batch temperature had risen to 212 ° C. Until then, 190 parts were one aqueous distillate has been collected. The pressure was carefully reduced.

After a further 11/4 hours the temperature of the batch was 145 ° C please. A resin with a softening point of 103 ° C. was obtained.

When a sample of the resin with 10 weight percent hexamethylenetetramine mixed and heated to 150 ° C, gelation occurred in 250 seconds.

Example 5 3000 parts of liquid from the peel of the fruits of the Kidneybaums, 768 parts of furfural (molar ratio 0.8) and 60 parts of manganese salicylate and 0.01 ouzo of an anti-foaming agent were used in that described in Example 1 Given the reaction vessel and heated to a temperature of 128 ° C. with stirring.

A slightly exothermic reaction was noted at this point. After the heat was stopped for 10 minutes, this reaction was heard on. Then the heating continued. After an additional 11/2 hours there was 150 parts of one aqueous distillate was collected while the temperature of the batch rose to 210 ° C was. After cooling, a rubber-like resin was obtained which when heated again quickly gelled to a temperature of 210 ° C.

Example 6 940 parts by weight of phenol, 660 parts of 5-methylfurfurol and 60 parts of zinc acetate were placed in a reaction vessel equipped with a stirrer and dephlegmator given, its jacket with the help of steam, the pressure of which is essentially 1 atmosphere was kept at a temperature of 120 ° C.

The vessel was heated so that the contents after one hour Reached a temperature of 180 ° C.

This temperature was maintained for a period of 5 hours. The vapors emitted from the dephlegmator during this time were condensed, passed to a separator for the azeotropic mixture and allowed to settle. the lower layer was continuously returned to the reaction vessel and the The upper layer consisting essentially of water is discarded. Towards the end of this Heating season, the evaporation was much less and stopped the formation of Water on.

The pressure was then lowered to 100 mm Hg while the temperature the insert was maintained and the temperature of the jacket was increased to 130 ° C, to remove unreacted portions. These conditions were observed for 30 minutes, whereupon the contents of the reaction vessel are emptied into a bowl and allowed to cool was left standing. It was found that the resin formed by heating with hardeners containing aldehyde groups including hexamethylenetetramine and p-formaldehyde or with the polymerization catalysts mentioned in Example I. has been hardened.

Claims (6)

PATENT CLAIMS: 1. Process for the preparation of condensation products of the novolak type by condensation of a monohydric or dihydric phenol in which at least two of the o- or p-positions to the phenol group are unsubstituted, or a mixture of these phenols with an aldehyde of the general formula in which X is an oxygen or sulfur atom and Y is a hydrogen atom or an alkyl or alkylol radical with up to 4 carbon atoms, characterized in that not more than 1 mole of the aldehyde per mole of phenol under practically anhydrous conditions in the presence of a salt of an electropositive metal in the divalent state with an acid which has a dissociation constant k from 1.7-10-2 to 1.010-6, preferably from 2-10-3 to 110-6 at 25 ° C. 2. The method according to claim 1, characterized in that the salt used in an amount of 1 to 5 percent by weight, based on phenol or phenols will. 3. The method according to claim I and 2, characterized in that as electropositive metal cobalt, lead, magnesium, manganese, zinc or cadmium is used will. 4. The method according to claim 1 to 3, characterized in that as Aldehyde furfural is used. 5. The method according to claim 1 to 4, characterized in that a Monohydric phenol in the o- and p-positions to the phenolic hydroxyl group is free of substituents is used and the amount of aldehyde 0.7 moles per mole Does not significantly exceed phenol. 6. The method according to claim I to 5, characterized in that a Monohydric phenol in one of the o and p positions to the phenolic hydroxyl group carries a substituent is used and the amount of aldehyde 0.8 to 1.0 mol per mole of phenol. Publications considered: German Patent No. 1,022,005; Austrian patent specification No. 86 764.