CS226310B1 - Method of stabilizing synthetic rubber,especially improving antidegradation resistance of vucanizates - Google Patents

Abstract

The present invention relates to a method for stabilizing synthetic rubbers or to increasing antidegradation the resistance of vulcanizates from natural and / or synthetic rubbers to the tris mixture substituted phenyl phosphites and alkyl aromatics in the form of an aqueous emulsion or solution in a suitable manner carrier. Natural rubber, obtained by coagulation of latex flowing from trees Hevea brasiliensis it contains certain non-rubber substances that protect it from exposure to oxygen, i. j. before oxidation and provides the rubber with the necessary stability during storage prior to processing in rubber factories. Substances of similar effect, so-called. stabilizers that I retard! respectively. to inhibit unwanted oxidative phenomena, should be added deliberately to the synthetic rubber latex. Under the influence of oxygen, catalysed by the simultaneous effect of elevated temperature, sunlight and mechanical stress, there is a sharp increase in the non-stabilized synthetic rubber viscosity and will not deteriorate completely. Today there is already a relatively wide range of substances that are known to have antioxidant effects and which are used as synthetic rubber stabilizers. One of these groups they form a relatively small group of phosphite derivatives that are commonly used as stabilizers synthetic rubbers and / or as antidegradants in latex and dry blends of e.g. native and synthetic rubbers. By way of example, trisinonylphenyl) phosphite, or tri s (phenylethylphenyl) phosphite. These substances have good protective properties, but their disadvantage is that they are prepared from relatively valuable raw materials such as phenol and especially olefins. Another disadvantage is that prior to application to the rubber compositions, their viscosity is adjusted to an appropriate value by addition a suitable diluent such as kerosene, petroleum and the like.

Description

The present invention relates to a process for stabilizing synthetic rubbers or increasing the anti-degradation resistance of vulcanizates from natural and / or synthetic rubbers with a mixture of tris-substituted phenylphosphites and alkylaromates in the form of an aqueous emulsion or solution in a suitable carrier.

The natural rubber obtained by coagulation of the latex flowing from the trees of Hevea brasiliensis contains certain non-rubbery substances which protect it from the action of oxygen, i. j. before oxidation and provides the rubber with the necessary stability during storage prior to its processing in rubber plants. Substances of similar effect stabilizers that retard! respectively. inhibit unwanted oxidative phenomena, need to be intentionally added to the latex of synthetic rubbers. Due to the oxygen catalysed by simultaneous exposure to elevated temperature, sunlight and mechanical stress, unstabilised synthetic rubber leads to a sharp increase in viscosity and does not cause it to deteriorate completely.

A relatively wide range of substances which are known to have an antioxidant effect and which are used as stabilizers for synthetic rubbers is now known. One group of these substances is a relatively small group of phosphite derivatives, which are commonly used as stabilizers for synthetic rubbers and / or as antidegradants in latex and dry mixtures of natural and synthetic rubbers. Examples include trisinonylphenyl) phosphite or tri (phenylethylphenyl) phosphite.

These substances have good protective properties, but their disadvantage is that they are prepared from relatively valuable raw materials such as phenol and in particular olefins. A further disadvantage is that the viscosity is adjusted to a suitable value by the addition of a suitable diluent, such as petroleum kerosene, petroleum, and the like, before being applied to the rubber composition.

Said drawbacks can be substantially eliminated according to the invention by stabilizing the synthetic rubbers or by increasing the anti-degradation resistance of the natural and / or synthetic rubbers by organic phosphites. It consists in adding 0.5 to 5.0% by weight, preferably 0.8 to 3.0% by weight, of a mixture of phosphites of the formula I to the rubber or rubber mixture.

wherein R ¹ is alpha, alpha-dimethylbenzyl, consisting of 50-99.8% tris (p-alpha, alpha-dimethylbenzylphenyl) phosphite, 0-30% tris (o-alpha, alpha-dimethylbenzylphenyl) phosphite, and 0.2% % to 20% of alkylaromates having a relative molecular weight of 236.

The preferred liquid form of the phosphite mixture allows for the preparation of an aqueous emulsion or solution in a suitable carrier as required for the stabilizer to be broken into the latex of the synthetic rubber. In order to facilitate the preparation of the required emulsion, the required emulsifier can already be added to the phosphite stabilizer, which thus becomes self-emulsifiable, i. j. it is only converted into the emulsion by adding the necessary amount of suitable treated water.

If necessary, e.g. j. if the amount of alkylaromates present in the stabilizer is insufficient, its viscosity may be lowered by the addition of a diluent such as petroleum, aviation kerosene and the like. This treatment is only necessary in cases where the pitch from which the stabilizer is prepared has an unusually low proportion of alkylaromates having a relative molecular weight of 236.

The final form of the liquid stabilizer can also be adjusted by adsorbing it onto an inert solid carrier, such as SiO ₂ or silicates, to provide a powdered product 8 of limited air permeability, suitable for easier weighing and dosing into dry mixtures of natural and synthetic rubbers.

In contrast to the known methods used to protect the rubbers of the aforementioned compounds, the method according to the invention is particularly advantageous in that it uses substantially cheaper compounds as stabilizers, since they are made of pitch, which is lost in the production of phenol from cumene. A further advantage is that the mixture of tris (alpha, alpha-dimethylbenzylphenyl) phosphites is accompanied by alkylaromates which virtually automatically detect the viscosity of the phosphite mixture suitable for use in rubber.

Examples of practical use of the method of the invention as well as the stabilizing effect achieved are given below.

EXAMPLE

Phosphites prepared from 82% 4- (alpha, alpha-dimethylbenzyl) phenol, 10% alkylaromates and 8% 2- (alpha, alpha-dimethylbenzyl) phenol - AO-A, 99.8% 4- (alpha, alpha-dimethylbenzyl) of phenol and 0.2% alkylaromates - AO-B as a 20% aqueous emulsion was conventionally dosed at a concentration of 1.5% per dry weight into the butadiene-styrene latex cream type 1500 used to produce Kralex 010.402. After the coagulation and drying of the obtained rubber, the stabilizing activity of the subject antidegradant was monitored by thermo-oxidative stressing of the raw rubber to 130 ° C for 0 to 8 hours and 70 ° C for 0 to 4 days. A measure of the stabilization efficiency is always the change in the viscosity of Mooney ML-1-4 / 100 ° C rubber, which occurs relatively quickly due to oxidation at elevated temperatures.

and

Table 1

Stabilizing effect of the subject antidegradant in Kralex 010.402; temperature 130, resp. 70 ° C

0 2 Mooney Viscosity, ML 4 1-4 / 100 6 ° C Mon 8 hours delta AO-A 44.0 46.0 46.0 45.5 45.0 + 1.0 AO-B 42.0 45.5 44.0 45.0 46.0 + 4.0 - 45.0 92.0 97.0 100.0 103.0 +58.0 0 1 Mooney Viscosity, ML 2 1-4 / 100 3 ° C Mon 4 days delta AO-A 44.0 52.0 54.0 54.0 59.0 +15 AO-B 42.0 49.0 52.5 55.0 59.0 +17 - 45.0 92.0 102.0 103.0 ⁺ )

⁺ ) skdDoor body destroyed

Example 2

The phosphite AO-A of Example 1 was dosed at a concentration of 1 and 2 parts per hundred parts by weight of rubber to a masterbatch of butadiene styrene rubber containing a mineral filler and a sulfur (tetramethylthiuram disulfide) diphenylguanidine vulcanization system; the elasticity of the mixture used to make the floor coverings is 30%.

The crude mixtures and the respective vulcanizates reached the following values:

Without antide- antioxidant AO-A gradantu 1,0 dsk 2,0 dsk

Vulk. Mooney characteristics,, 40 ° C,

- ie, min 24.5 23.0 22.5 - ^min 8.4 8.3 8.3 fyzikálnemechanické vulcanizate properties, 20 mins / 145 ° C: - tensile strength, MPa 6.2 7.8 7.5 after aging 3 d / 90 ° C 5.8 7.5 7.1 elongation,% 120 120 120 after aging 3d / 90 ° G 100 120 120 - hardness, ° Sh 90 90 89 - after aging 3d / 90 ° C 9 9 ' 90

The degree of coloring of the vulcanizate exposed to UV light exposure to a silicon lamp for 8 hours does not differ from the unprotected vulcanizate, i. j. vulcanizate not containing the subject antidegradant.

Claims (1)

SUMMARY OF THE INVENTION A method of stabilizing synthetic rubbers or enhancing the anti-degradation resistance of vulcanizates from natural and / or synthetic rubbers, respectively. mixtures thereof with organic phosphites, characterized in that 0.5 to 5.0% by weight, preferably 0.8 to 3.0% by weight of the mixture of phosphites of the formula I "OO - P (I) is added to the rubber or rubber mixture. wherein R 1 is alpha-alpha-dimethylbenzyl formed from 50 to 99.8% tris (p-alpha, alpha-dimethylbenzylphenyl) phosphite, from 0 to 30% tris (o-alpha, alpha-dimethylbenzylphenyl) phosphite and 0, 2-20% alkylaromates having a relative molecular weight of 236. Severografia, np, MOST Price 2,40 Kčs