DD291902A7 - METHOD FOR PRODUCING AGING-RESISTANT RUBBER MATERIALS BASED ON NATURAL AND / OR SYNTHESIS RUBBER - Google Patents

Abstract

The invention relates to a process for the production of heat-aging, ozone and weather-resistant non-contact stiffening rubber materials based on natural, styrene-butadiene, acrylonitrile-butadiene and chloroprene rubber, which contain as aging inhibitors cyclic condensation products of polyhydric phenols with carbonyl compounds which have a high Long-lasting antioxidant activity, with protection against fatigue and ozone attack as well as against rubber toxins and the "crazing" effect. Their action is synergistically enhanced by mercaptobenzimidazoles. Rubber; Anti-aging agents; Antioxidant; Calixarenpolyole; Thermooxidationsbestaendigkeit; antiozonant; Riszbildungswiderstand; Wetterbestaendigkeit; Kontaktverfaerbung; "Crazing" effect}

Description

R ³

HO

OH

With

R ^{1 is} -H, alkyl, aryl

R ² = H alkyl

R ³ = H, 0H.alkyl, aryl, aminoalkyl

3. The method according to claim 1, characterized in that a calix / 4 / arenpolyol in combination with a non-discoloring and / or discoloring anti-aging agent, preferably with a mercaptobenzimidazole and / or substituted p-phenylenediamine, is added.

Field of application of the invention

The invention relates to a process for the production of heat aging, weather and ozone resistant rubber materials based on natural and / or synthetic rubbers, which contain the usual ingredients in the rubber processing industry. The products made from the respective rubber compounds can be used where ambient and / or fluid temperatures above ambient temperature prevail and atmospheric ozone is applied or where no contact discoloration is allowed to occur.

Characteristic of the known technical solutions

For the production of heat-aging, weather and ozone-resistant rubber materials based on natural and / or synthetic rubber, it is preferred to add aminic aging inhibitors to the elasto mixtures during the mixing process. According to H. Fries (Gum, Asbestos, Kunststoffe 40 [1987] pp. 239-252), however, these substances cause a discoloration of the gum or of other materials in contact with it, from brown to black, in the practical use of the gum products in question. The disadvantage is, in particular, the ability to be washed out, especially of the most active representatives of the class, the substituted p-phenylenediamino, which has relatively high thermal volatility, especially in the case of .alpha.,. Alpha .'-dialkyl and N, N'-aralkyl derivatives of the p-phenylenediamino group. Phenylendiamina and substituted naphthylamines, the more or less pronounced influence on the scorching time of crude rubber mixtures and the carcinogenic effect of ß-naphthylamine as an impurity of the anti-aging agent phenyl-ß-naphthylamine.

Sterically hindered mono- and bisphenols as anti-aging agents, on the other hand, do not cause any contact discoloration and no or only little yellowing of the vulcanizates exposed to light. According to L. Ruetz: The anti-aging agents of the bisphenol class (Technical Information Sheets No. 2.15, Sept. 1985, pp 1-12) is the antioxidant activity of the monofunctional phenolic compounds, however, due to their volatility in the vulcanization process of the rubber blanks and / or at high use temperatures of the rubber article due strongly decreasing concentrate.

A high efficiency is achieved by bifunctional phenolic products. However, these are correspondingly more expensive and cost-effective. It is also known (see L. Ruetz) that the fatigue cracking effect is less pronounced and that these products do not provide protection against ozone cracking under static and / or dynamic mechanical conditions. They show slight discoloration in the light to yellow, pink or brownish. Of considerable disadvantage is their easy extractability by numerous solvents, in particular hydrocarbons. As well as many amines in rubber, they are subject to a wash-out process by water and extraction by fuels, alkalis and aqueous solutions of basic salts. A Lang'eitwirkung of these products is therefore not available. Otherwise, in the case of thermally stressed rubber articles, expensive specialty skins, such as eg. As ethylene-propylene terpolymers, epichlorohydrin, silicone or hydrogenated acrylonitrile-butadiene rubber are used, which require special crosslinking systems for vulcanization bf.

Object of the invention

The object of the invention is to provide a process for the production of aging-resistant rubber materials, which overcomes the disadvantages of known processes, in particular to rubber materials which do not discolor, which do not cause contact discoloration, can be used even at elevated room or fluid temperatures Atmospheric ozone, whose aging protection agent can not be extracted by liquid media and which are inexpensive to manufacture.

Explanation of the essence of the invention

The invention is based on the object of creating such conditions in the production process of rubber materials that materials are produced in a technically simple manner, the aging resistance of which is substantially improved compared with the prior art.

The object is achieved according to the invention by soldering cyclic condensation products of polyhydric phenols with carbonyl compounds to the components known per se in the process of producing rubber materials. Particularly suitable are calix / 4 / arene polyols. These substances can be prepared in a manner known per se from polyhydric phenols and aldehydes (J. Am. Chem. Soc., 62, 2512 [1940]). These compounds are used in place of mono- and bisphenols, substituted naphthylamines and substituted dihydroquinolines in rubber blends based on natural and / or synthetic rubber and the usual ingredients in the rubber industry. There is an increase in the thermal oxidation resistance of the rubber materials, even at elevated temperatures, while improving their weatherability and maintaining good protection against the destructive effects of dynamic mechanical forces and certain heavy metal compounds acting as so-called rubber toxins in the presence of oxygen

 Calixarene / 4 / polyols are metacyclophanes of general structure I.

HO

OH

HO

With

R ¹ -H ₇ alkyl, aryl

R ² = H alkyl

R ³ = H ₁ OH, alkyl, aryl; aminoalkyl

They are distinguished by their high molecular weight, high antioxidant activity, non-volatility and heavy extractability of water, alcohols and nonpolar hydrocarbons. According to the invention as antioxidants for diene rubbers in particular the compounds with

R '= CH ₃ , R ² = H, R ³ = HR ¹ = CH ₃ , R ² = H, R ¹ = OH R ¹ = CH ₃ , R ² = H, R ³ = CH ₂ N (C ₂ Hs ) ₂ R '= CH ₃ , R ² = H, R ³ = CH ₂ NC ₂ Hi ₀ R ¹ = CH ₃ , R ² = H, R ³ = CH ₂ NC ₄ H ₈ O

and with and with and with and with suitable.

It has been found that the improvement of the properties of natural and / or synthetic rubber based rubber vulcanizates can be achieved after thermo-oxidative and dynamic mechanical stress and the reduction of static ozone disruption and outdoor airing when 0.05 to 10 wt. Parts, preferably 0.5 to 4.0 parts by mass, of a calix / 4 / arene polyol to 100 parts by mass of elastomer are added to the rubber mixture,

The characteristic values obtained by the novel process of the vulcanizates, such 'as tensile strength and elongation at break after heat aging at 7O ⁰ C and 100 ⁰ C, the initial elongation, number of cracks and crack depth .: ns. an outdoor ventilation or artificial ozone aging and the average cracking resistance after an upset bending test are more favorable than with the vulcanizates which contain a mono- or bifunctional phenolic aging inhibitor at the same concentration. Particularly noteworthy is that the tetramethylcalix / 4 / arenpolyole in the presence of 2-mercaptobenzimidazole reduce the harmful effect of heat and oxygen more than any substance by itself at the same concentration of anti-aging agents, ie a synergistic effect is present. In combination with substituted p-phenylenediamines, calix / 4 / arene polyols provide enhanced ozone aging and weatherability of rubber vulcanizates. The following examples are intended to illustrate the procedure according to the invention without restricting it.

embodiments

The rubber compounds were prepared in a laboratory internal mixer of the type GK4 N according to a uniform mixing procedure.

example 1

Formulation of a beige rubber based on natural butadiene-styrene rubber base of Shore hardness A60 ± 5

not inventive 2 fiction, 4 contemporary Ma. parts contemporary Ma. parts mixtures 51.00 mixtures 51.00 1 49,00 3 49,00 components Ma. parts 9.20 Ma. parts 9.20 natural rubber 51.00 11,80 51.00 11,80 ölverstreckterButadien-styrene rubber 49,00 29,60 49,00 29,60 high molecular weight butadiene-styrene plasticizer 9.20 28,90 9.20 28,90 zinc oxide 11,80 37.50 11,80 37.50 kaolin 29,60 4.90 29,60 4.90 precipitated silica 28,90 2.30 28,90 2.30 Zinc sulfide / barium sulfate filler 37.50 5.30 37.50 5.30 Fact is 4.90 4.90 4.90 4.90 stearic acid 2.30 0.00 2.30 0.00 rosin 5.30 2.00 5.30 0.00 Ozone protection wax 4.90 0.00 4.90 0.00 2,6-di-t-butyl-4-methylphenol 2.00 0.00 0.00 2.00 2,2'-Mthylen-bis-4-methyl-6-t-butyl-phenol 0.00 0.20 0.00 0.20 Tetramethyl-calix / 4 / arenoctol 0.00 0.72 2.00 0.72 Tetramethyl-calix / 4 / a / endodecaol 0.00 0.85 0.00 00.85 diphenylguanidine 0.20 2.60 0.20 2.60 tetramethylthiuram 0.72 240.77 0.72 240.77 mercaptobenzothiazole 0.85 0.85 sulfur 2.60 2.60 240.77 240.77

Vulcanization of the elastomer raw mixtures: 10 minutes at 150 ⁰ C characteristics of the vulcanizates

A: heat aging behavior

Percent loss of tensile strength _Δσ Β / _σ Β x 100 in% and elongation at break _Δε Β / _ε Β x 100 in% after heat aging for 7 days at 7O ⁰ C or 7 days at 100 ⁰ C determined in accordance with TGL 14366 or 14367 to Ring specimens of 6mm thickness

Material of mixture

property

Aa _B / _B o -100nach7d / 70 ° C _B -100nach7d Ae / 70 ° C Ao _B / _B o -100nach7d / 100 ^o C _B Ae / e _B -100nach7d / 100X

21 -15 -12 -12 35 -28 -22 -20 44 -37 -35 -34 63 -59 -54 -53

B: Ozone aging reserves

Initial elongation (rißfreierr strain range) D ₁ in%, number of cracks A and crack depth T in the elongation zone Z2 in the range of 11 to 20% elongation after an ozone aging at an ozone concentration of 50 ppm, a temperature of 4O ⁰ C and a Prufdauer of 72Stdn., Calculated according to TGL 24418 to 0 to 50% continuously stretched hollow cylindrical specimens of 3mm thickness.

Explanation of terms:

Initial strain D | in% is the static strain at which the first crack occurs. A D, value of 30% means that the stretch area lying between 29% and 29% remains crack-free. Crack number A and crack depth T are classified as follows:

AO no cracks TO no cracks

• A1 Ibis 5Risse T1 Surface Cracksca.0,1 toO, 5mmtief

A2 6bis 40Risse T2Risseca. 1 mmtiof

A3 41 to 120 cracks T3 Cracks over 1 mm deep

A4 over 120 cracks T 4 piercedor specimen

Material of mixture 2 3 -> NJ CO 4 Eigenschaii 1 14 3-4 1 O CM T- CM Initial elongation Di in% Number of cracks A Crack depth T 10 4 1

C: Bewettmungsverhalten

Initial elongation D ₁ in%, number of cracks A and depth of cut T in the zone of elongation Z5 after a soaking period of 29 days under the following medium-altitude European meteorological conditions:

mean ozone concentration 29 pg / m ³

average air temperature 8.5 ° C

average daily sunshine duration 4.7 hours

average daily rainfall 1.6 mm

determined according to TGL16890 on the sun and shade side at 0 to 50% continuously stretched hollow cylinder prufeköfpern of 3 mm thickness.

Material of mixture 2 I 3 4 property 1 Sunny side of the specimen 40 45 46 Initial strain D ₁ in% 30 2 2 2 Number of cracks A 3 2 2 2 Crack depth T 2-3 Shadow side of the specimens 33 41 42 Initial strain D ₁ in% 28 2-3 2 2 RißanzahlA 3 2 2 2 Crack depth T 2

D: fatigue behavior

Mean cracking resistance RBW alb decadic logarithm of the kilocycles to reach the mean cracking level C after a compression deflection test according to De Mattia (TGL 14378) determined on strip specimens of 6.3 g thickness.

Material of mixture 3 4 property 1 2 0.93 0.95 RBW 0.58 0.89

ü: contact discoloration

Lacquer discoloration of white alkyd resin paint to factory standard GKTS 802-3 / 01 on specimens of

Dimensions 200mm x 20mm x 2mm.

property

Material of mixture 1 2

Discoloration after 21 Tjgen exposure in the Freion (subjacent meteorological conditions: mean air temperature = 9.8 ⁰ C mean daily sunshine duration = 3.1 hours mean daily rainfall = 7.9 mm)

none

none

none

none

Q: "crazing" - Effect after a sunshine duration of 470 hours: • O 4 Material of mixture unavailable unavailable 1 2 Intensity of the effect "Crazing" - medium - not moderately available

Example 2

Formulation of a carbon black-filled butadiene-acrylonitrile rubber-based rubber of Shore hardness A65 ± 5

not him invention 7 8th Contraption mixture Ma. parts Ma. parts contemporary 100.00 100.00 mixture 0.93 0.93 5 6 1.43 1.43 components Ma.-Teilö Ma. parts 0.00 0.00 Butadiene-acrylonitrile rubber 100.00 100.00 0.00 0.00 phthalic anhydride 0.93 0.93 1.43 0.00 N-isopropyl-N'-phenyl-p-phenylenediamine 1.43 1.43 0.00 1.43 Phenyl-beta-naphthylamine 1.43 0.00 6.43 6.43 Tetramethylcalix / 4 / arenoctol 0.00 1.43 2.50 2.50 N, N-diethylaminomethylene-tetramethylcalixAt / arenoctol 0.00 0.00 15.71 15.71 Piperidinomethylen-tetramethylcalixAl / arenoctol 0.00 0.00 62.86 62.86 zinc oxide 6.43 6.43 6.43 6.43 stearic acid 2.50 2.50 6.43 6.43 chalk 15.71 15.71 12.50 12.50 soot 62.86 62.86 2.38 2.38 microcrystalline ozone protection wax 6.43 6.43 1.07 1.07 Triphe; ylphosphat 6.43 6.43 220.10 220.10 dibutyl phthalate 12.50 12.50 Shwefel 2.38 2.38 N-cyclohexyl-2-benzothiazylsulfenamide 1.07 1.07 220.10 220.10

Vulcanization in a steam-heated press: 40 minutes at 150 ° C

The characteristic values of the vulcanizates were determined by the TGL indicated in Example 1 and on test specimens described there

averages. An exception is the determination of the heat aging behavior, which was done on 2 mm thick rod specimens.

Material of mixture

property

A: Heat aging behavior Relative change in elongation at break Δε _Β / ε _Β (%) after 3d / 100 ° C

Relative change in the elongation at break Δε _Β / ε ₈ (%) after storage for 3 days in the carburetor fuel at 20 ° C and subsequent heat aging of 3 d / 10ü ⁰ C.

-28

-34

-34

-14

Material of mixture 6 7 8th property 5 34 OO 33 O O 27 1 1 26 1-2 1 23 2 1 21 2 1 B: Ozone aging behavior Initial elongation Di (%) Crack number A (strain zone Z 3) Cracking depth T (strain zone Z3) after ozone aging at 50 pphm / 40 ° C / 42 h. Initial elongation Di (%) Number of cracks A (expansion zone Z 3) Cracking depth T (expansion zone Z 3) after ozone aging at 100 pphm / 50 ° C / 96 h. to to - · IO O _ »IO -». 44 1-2 • 2 CM OO τ- CO CM 27 2-3 3 C: Weathering behavior Initial elongation Di (%) Number of cracks A (expansion zone Z 5) Cracking depth T (expansion zone Z 5) 2 3

on the test specimen sun side after aeration of 100 days under the following central European meteorological standard conditions:

av. Ozonkonz. 29 ugrrT ³ ave. Air Temp. 8,5 ⁰ C

av. t3gl. Sunshine duration 4.7 hours

av. daily precipitation 1.6mm.

D: fatigue behavior

Medium cracking resistance RBW

1.78

1.78

1.93

Example 3

Formulation of silicic acid filled NR / SBR material with different age protection agents for the detection of

synergistic effect

mixtures

components

10

11

2-Mt rcaptobenzimidazole tetramethyl-calix / 4 / arenoctol 2,6-di-t-butyl-4-methylphenol 2,2'-methylenebis / 4-methyl-6-t-butylphenol / tetramethyl calix / 4 / arendodecaol Other components as in mixtures 1 to 4 of Example 1.

2.00 0.00 1.00 0.00 2.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Vulcanization of elastomer blends: 10 minutes at 150 ° C

The characteristic values of the vulcanizates were determined by the TGL indicated in Example 1 and on specimens described there

determined.

Material of mixture

property

10

11

A: heat aging behavior

Relative change of elongation at break

AE ₈ / e _B -100 (%) after 7d at 70 ^o C -26 -22 -17

Ae _B / e _B -100 (%) after 7d at 100 ° C -57 -54 -43

B: fatigue behavior Mean Cracking Resistance RBW 0.95 1.16 1.49 RBWafter heat aging at 7d / 70 ° C 0.64 0.70 1.07

Claims (2)

-1- 291 9C2 Claims: 1. ancestors for the production of aging-resistant rubber materials based on natural and / or synthetic rubber, the usual fillers and plasticizers in the rubber industry, organic accelerators and sulfur as vulcanizing agents, protective waxes and other necessary mixing components that are resistant to heat aging, ozone and weather , characterized in that in the mixing process of the rubber mixture cyclic condensation products of polyhydric phenols with carbonyl compounds in a dosage of 0.05 to 10 parts by mass, preferably 0.5 to 4.0 parts by mass, based on 100 parts by mass of elastomer, as an antioxidant be added. 2. The method according to claim 1, characterized in that are used as the cyclic condensation product substituted calix / 4 / arenpolyole of the general formula I.