DEC0012081MA - - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

Registration date: November 10, 1955. Advertised on December 20, 1956

GERMAN PATENT OFFICE

To increase the heat resistance of bonds made by means of rubber adhesives, in particular are made by means of adhesives based on chloroprene rubber, is used in known Way of adding phenolic resins. Among these there are those based on the so-called Alkylphenols well established because they can noticeably increase heat resistance. The decisive factor for this is probably the formation of high-melting, but nonetheless soluble products from the phenolic resin and the inorganic incorporated into the adhesives for other reasons Additions such as zinc oxide, magnesium oxide and the like. »Alkylphenols« · are phenols, which are used in ortho- or para-position to the phenolic hydroxyl group a larger, usually from at least Have 4 carbon atoms existing substituents. This ensures a very good solubility of the Phenols and the resins made from them in organic solvents, especially in hydrocarbons, causes, while the phenolic resins made from phenol and cresol, on the other hand, normally are not soluble in hydrocarbons. Another characteristic of the alkylphenols is that by the Incorporation of the substituent a reactive point in the phenol nucleus is omitted, so that only 2 reactive

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C 12081 IVa / 22ί

ready nuclear hydrogen atoms are available. For this reason there is the possibility of resinification the alkylphenol resins are severely restricted, which in turn benefits the formation of readily soluble resins comes. The good solubility of the alkylphenol resins is one of the most important factors in their use for rubber adhesives, since aromatic and preferred solvents in these aliphatic hydrocarbons, chlorinated hydrocarbons and esters can be used.

The most common alkylphenols include p-tert-butylphenol, p-tert-amylphenol and p-diisobutylphenol. In addition to phenols with pronounced alkyl substituents, one counts among the »alkyl« - phenols, however, also include those phenols which are in the ortho or para position to the phenolic hydroxyl group

'have an aryl, aralkyl or cycloalkyl radical, for example o- and p-phenylphenol, benzylphenol or cyclohexylphenol. These phenols are in aliphatic However, hydrocarbons are no longer as indefinitely soluble as z. B. p-tert-butyl or p-tert-amylphenol. The same applies to the formaldehyde condensation products made from them.

Not all resins made on the basis of alkylphenols provide an increase in heat resistance equally good when bonding with rubber adhesives. This is how nian finds it Products that are unsatisfactory in terms of their heat resistance-increasing effect, while other alkylphenol resins behave relatively well. The melting point, which varies from case to case In any case, such resins are not decisive, since lower-melting resins are often better ones Heat resistance cause higher melting products.

It was all the more surprising when, on the other hand, it was now found that something in itself was something less readily soluble resins made from phenols, which have a position parallel to the phenolic hydroxyl group have cyclic substituents, especially those from p-phenylphenol and cyclohexylphenol, The higher their melting point, the higher the heat resistance of the rubber adhesives is. Through the use of relatively high-melting p-phenylphenol or p-cyclohexylphenol-formaldehyde resins As has been found in accordance with the invention, surprisingly unusually high heat strengths can be achieved in the case of rubber adhesives Achieve, as they - with the usual alkylphenol resins cannot be achieved. The strength of the bonds often even extends still to temperatures above 100 ° C.

For the resins produced from p-phenylphenol or cyclohexylphenol to work well, it is important that they have a melting point as high as possible, at least 90 to 100 ° C., preferably above 120 ° C., determined by the capillary method. These resins are obtained by e.g. B. prepares methylol compounds of p-phenylphenol or cyclohexylphenol in a known manner and condenses these ^{further at temperatures above 130 0} up to the desired high melting point. The formaldehyde content of the methylol compounds should be at least about 1.5 mol per phenolic hydroxyl group. According to the invention, however, methylol compounds which are richer in formaldehyde can also be used, for example p-phenylphenol dialcohol or p-cyclohexylphenyl dialcohol, alone or together with minor amounts. Condense phenylphenol or cyclohexylphenol as such or from other alkylphenols. By adding the phenols as such, the technical execution of the 'condensation to high-melting resins can be facilitated, since the condensation z. B. of p-phenylphenol dialcohol by itself at high temperatures, especially above 150 ⁰ , leads to very tough resins which can have a melting point of over 170 ⁰ . As much as it is precisely these products that can achieve particularly high heat strengths in the adhesives according to the invention, modifications are favorable in the interests of technically simple production or easier solubility of the resins, such as those that are found in the joint condensation with other alkylphenols, e.g. B. p-tert-butyl or amylphenol or with methylol compounds prepared from these or non-phenolic, resinous, modifying additives such as. B. rosin or resins made therefrom or polymerized rosin, coumarone resin, terpene phenol resins or others result. The condensation itself can, if desired, take place in a stirred vessel, a drying cabinet, a heatable mixer or the like. Under certain circumstances, it can also be in solution, e.g. B. in toluene can be made, it is useful to use a water separator.

The resins used according to the invention can also be prepared in such a way that p-phenylphenol or cyclohexylphenol with formaldehyde in the presence of ammonia or hexamethylenetetramine can be converted directly to a high-melting resin, i.e. in a particularly simple way of working. In this case, too, the condensation can be carried out by adding an inert solvent and by ' Working with a water separator will be favored.

The resins described can be used in adhesives based on natural rubber, cyclized rubber or synthetic rubber types, with the latter often being the Polymers of chlorobutadiene are preferred.

Because of the high effectiveness of the resins according to the invention, they do not need to be used in quantities to be too high, which in turn promotes the elasticity of the bond. For example, have 40 to 50% resin, based on rubber, has proven itself well. The addition of others for rubber adhesives eligible components, e.g. B. inorganic fillers, anti-aging agents. Like. Is not affected by the use of the resins.

Because of the limited solubility of the p-phenylphenol resins in aliphatic hydrocarbons it is advisable to reduce the proportion of these solvents to keep the adhesives low and the use of other, better-dissolving solvents to be preferred, or to use from the outset those resins that are subordinate by condensation Amounts of soluble phenols, e.g. B. from

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p-tert-butylphenol or its methylol compounds, also have a solubility in gasoline hydrocarbons.

The excellent action of the high-melting resins made from phenols with cyclic substituents to be used according to the invention in rubber adhesives is expressed in the following examples. These are comparative examples, all of which were carried out according to the same scheme. In general, even higher heat strengths can be achieved with optimally adjusted proportions between rubber and resin. In the present examples were each 4O ° / ₀ phenolic resin, calculated on the rubber content, the Klebst produced from the rubber and other slamming off in the form of a 5o ° / ₀ toluene solution added solution. This had the following composition:

100 parts of chloroprene rubber were mixed with 4 parts of magnesium oxide and 5 parts of zinc oxide for 10 minutes rolled. 54 parts of this mass were then added to a mixture of 45 parts of toluene and 75 parts of ethyl acetate and 60 parts of methylene chloride dissolved.

The adhesive tests were carried out in such a way that 2 cm wide strips of sole rubber were bonded with a ι cm wide overlap and the shear strength of the bonded strips, expressed in kg / cm ² , after at least 24 hours of storage at room temperature and then 3minute heating in a drying cabinet to 50 or respectively 80 ° was measured. Tearing speed 160 mm / min.

example 1

The adhesive solution contains a ⁰ at 134 melting phenolic resin which has been obtained by heating p-Cyclohexylphenoldialkohol to about 200 °. The viscosity of 5o ° / ₀ toluene solution prepared from this resin is 500 cp at 20 ^0th

- The shear strength of the bond made with the resin is after 4 days of aging Room temperature

at 50 ⁰ 10.1 kg / cm ²

at 80 ° 3.0 kg / cm ²

Example 2

The adhesive solution contains a very viscous, melting at about 165 ° resin which is obtained by gradually heating of p-Phenylphenoldialkohol to about 170 ^0th

Shear strength of the bonds after 7 days

at 50 ° 11.7 kg / cm ²

at 80 ° 3.4 kg / cm ²

Example 3

The resin added to the adhesive solution is produced by heating together 100 parts of p-phenylphenol dialcohol with 10 parts of p-phenylphenol to a temperature of 180 °. It melts at i66 °. The prepared from it 5o ° / ₀ toluene solution has a viscosity of 2000 cp at 20 °.

The shear strength of the bond achieved after 2 days is

at 50 ⁰ 10.6 kg / cm ²

at 80 ° 3.2 kg / cm ²

Example 4

For the adhesive solution, a resin is used which is obtained by heating together 40 parts of p-Phenylphenoldialkohol with 5 parts of p-tert-Butylphenoldialkohol to 180 ° and whose melting point is over 170 ^0th

The shear strength achieved in this way is after 7 days

at 50 ⁰ 11.6 kg / cm ²

at 80 ° 3.3 kg / cm ²

Example 5

A ratio of 1 mole of p-phenylphenol to 1.8 moles of formaldehyde in the usual way in an alkaline solution obtained condensate obtained after acidification, washing and heating up to 200 ⁰ a resin whose melting point is at 143 ⁰ and its 5o ° / ₀ solution has a viscosity of 430 cp at 20 ⁰ in toluene.

This resin is used to produce an adhesive with the following shear strength after 7 days exhibit:

at 50 ⁰ 11.8 kg / cm ² 9 <>

at 80 ° 4.0 kg / cm ²

Example 6

168 parts of p-phenylphenol, 70 parts of p-tert-butylphenol, 90 parts of 3O ° / ₀ aqueous formaldehyde solution, 14 parts of hexamethylenetetramine and 200 parts of toluene are heated under a water separator as long until no more water separated. The behind consistent upon evaporation of the toluene yellow resin melts at 139 ^{0 and} 5o ° / ₀ toluene solution has a viscosity of 350 cp.

An adhesive solution is produced from this resin, the following shear strength after 7 days results in:

at 50 ⁰ 10.1 kg / cm ²

at 80 ° 2.3 kg / cm ²

Example 7

By heating together 50 parts of p-Phenylphenoldialkohol and 10 parts of melting at 130 ° rosin polymer up to 170 ⁰ at 134 ⁰ a melting resin is obtained. The adhesive produced with it brings a shear strength after 7 days

at 50 ⁰ of 9.7 kg / cm ²

at 80 ° of 2.4 kg / cm ²

Claims (3)

PATENT CLAIMS: i. Adhesives based on natural or synthetic rubber mixed with high-melting, soluble phenolic resins, thereby characterized in that they are soluble formaldehyde condensates of phenols with cyclic phenolic resins Containing substituents in the para position, using at least about 1.5 moles 609 737/330 C 12081 IVa / 22 ί Are produced formaldehyde to phenol mole ι according to known processes and as far condensed at temperatures above 120 °, that its melting point is above 90 to 100 °, preferably over 120 ^0, is located. 2. Adhesives according to claim 1, characterized in that they contain phenolic resins which from phenols with cyclic substituents with the use of minor amounts of one Alkylphenol, preferably p-tert-butylphenol, p-tert-amylphenol or p-diisobutylphenol are. 3. Adhesives according to claim 1 or 2, characterized in that they contain phenolic resins which not from phenols with cyclic substituents with the use of minor amounts phenolic, resinous, modifying additives are made.