DE2053574C3 - Process for the production of vulcanizates - Google Patents

Description

R-O

R-O

where R is identical or different, straight-chain or branched alkyl, optionally substituted cycloalkyl or optionally substituted aryl groups, Z is zinc, cadmium, lead, antimony, a primary, secondary, tertiary or mixed, aliphatic mono-, di- or polyamine is cycloaliphatic, an optionally substituted aromatic or heterocyclic amine and χ is an integer corresponding to the bond strength of Z, and optionally customary additives, characterized in that a mixture of 0.2 to 1.0 parts by weight is used for vulcanization. Sulfur, 0.1 to 5.0 parts by weight. of the dithiophosphate and 0.1 to 2.0 parts by weight. a known vulcanization accelerator, each based on 100 parts by weight TL rubber used, and the molding composition is vulcanized at 100 to 250 ⁰ C.

Various vulcanizing processes are already available for sulfur-vulcanizable rubber compounds known. So the method in which the crosslinking using sulfur and z. B. a Sulfenamide accelerator is carried out. The vulcanizates obtained with these known sulfur processes are known to have disadvantages, particularly with regard to their heat aging process. Also the so-called »efficient process«, in which a lower sulfur content combined with a faster acting accelerator combination of z. B. a sulfenamide and a thiuram accelerator are used will result in vulcanizates which, in terms of their heat aging behavior, albeit with respect to the normal sulfur process improved, still not fully satisfactory. In addition, there is Using thiruam accelerators there is a risk that the vulcanizates will have blooming. Indeed also the use of so-called sulfur donors, in which the sulfur is split off by sulfur Compounds is replaced, did not lead to vulcanizates, their heat aging behavior in any case sufficient. In addition, the aforementioned crosslinking methods have the disadvantage that they all are relatively expensive.

The Russian publication, Soviet Rubber Technology, Vol. 24 (1965), No. 7, pages 8-13 describes on page 8, left column, a stabilizing effect for rubbers, caused by zinc diisopropyldithiophosphate, Zinc diisopropyldithiocarbamates, phenols and phenylenediamines, detailed below is that if the dithiophosphate with N-cyclohexyl-2-benzthiazylsulfenamide is combined, in a certain case an improved crosslinking density is achieved, namely only when dithiophosphate and the sulfenamide are added together. The dithiophosphate used alone is considered to be weaker Designated accelerator (page 8, right column above Fig-1) -

Based on the test results listed in the table, it is also determined that the dithiophosphate acts as a stabilizer for the sulfur crosslinking in the rubbers. The experiments carried out there had the following compound structure:

N-cyclohexyl-2-benzthiazyl-

sulfenamide 0.8 part by weight.

Sulfur 2.0 parts by weight. Dithiophosphate 2.2 parts by weight.

the actual stabilizer effect only occurs when, in addition, N-isopropyl-N'-phenyl-p-phenylenediamine or 2,2'-methylenebis (4-methyl-6-tert-butyl) -phenol (see Table 3) has been added

The sulfur dosage of 2 parts by weight. already indicates that the "efficient vulcanization process" has been used. The sulfur dosage is rather within the conventional framework.

The invention was therefore based on the object of specifying a crosslinking process that uses vulcanizates better heat aging process and is also cheaper than the known Networking process. In the case of a method for vulcanizing, this task is performed as mentioned at the beginning Art solved by using a combination of vulcanization accelerators, consisting from a diradicaldithiophosphate of the formula

"R O

R-O

where R is identical or different, straight-chain or branched alkyl, optionally substituted cycloalkyl or optionally substituted aryl groups, Z is zinc, cadmium, lead, antimony, a primary, secondary, tertiary or mixed, aliphatic mono-, di- or Polyamine, a cycloaliphatic, an optionally substituted aromatic or heterocyclic amine and χ is an integer corresponding to the bond strength of Z and at least one further vulcanization accelerator known per se.

The invention thus provides a process for the production of moldings by vulcanizing Molding compounds made from natural rubber, butadiene rubber, isoprene rubber or butadiene-styrene, butadiene

Acrylonitrile and isoprene-acrylonitrile copolymers, sulfur and / or sulfur donors, known Vulcanization accelerators, as well as dithiophosphates of the formula

"R-O S

R-O

where R is identical or different, straight-chain or branched alkyl, optionally substituted cycloalkyl or optionally substituted aryl groups, Z is zinc, cadmium, lead, antimony, a primary, secondary, tertiary or mixed, aliphatic mono-, di- or polyamine cycloaliphatic, an optionally substituted aromatic or heterocyclic amine and χ is an integer corresponding to the bond strength of Z and optionally customary additives, characterized in that a mixture of 0.2 to 1.0 wt. teaspoons of sulfur, 0.1 up to 5.0 parts by weight of the dithiophosphate and 0.1 to 2.0 parts by weight. of a known vulcanization accelerator, based in each case on 100 parts by weight. Rubber, is used and the molding compound is vulcanized ^{at 100 to 250 ° C.}

Accelerator combinations such as those made from zinc dialkyldithiophosphates and thiazole accelerators have been used for the vulcanization of EPDM rubbers used, but show the vulcanizates obtained therewith compared to those vulcanizates with the usual EPDM vulcanization accelerators, such as Thiurams or dithiocarbamates and thiazoles are obtained, a poorer heat aging behavior.

About the difference in the heat aging behavior of vulcanizates produced with conventional sulfur dosing in contrast to those made with low sulfur doses, a was shown Comparative experiment carried out

It was therefore surprising that such an accelerator combination when used in the listed rubbers other than EPDM to vulcanizates with an improved heat aging process leads

Vulcanizing agents are sulfur, sulfur donors such as dicaprolactam disulfide and dimorpholyl disulfide or mixtures of sulfur and sulfur donors can be used. The amounts of sulfur vary depending on the the rubber to be vulcanized advantageously 0.2-1 part by weight, preferably 0.5-1 part by weight on 100 parts by weight of rubber. When using sulfur donors, these are corresponding to your Dose higher content of removable sulfur. The dithiophosphates are advantageously used in amounts of 0.5 parts by weight and the additional accelerator known per se in amounts of 0.1-2.0 parts by weight, based on 100 parts by weight of rubber, depending on the accelerator and the rubber to be crosslinked.

As examples of those known per se which can be used in the vulcanization process according to the invention The following accelerators are mentioned:

Thiazole accelerators,

like 2-mercaptobenzothiazole,

Zinc-2-mercaptobenzothiazole,

2-2-dithiobisbenzothiazole and

N-CyclohexyIbenzothiazol-2-sulfenamide, Thiurams such as tetramethylthiuram monosulfide, Tetramethylthiuram disulfide,

Tetramethylthiuram trisulfide,
ι tetramethylthiuram tetrasulfide,

the corresponding

Ethyl, propyl and butyl compounds and Dipentamethylene thiuram tetrasulfide,

Dithiocarbamates,
ι ο like zinc dimethyldithiocarbamate,

Zinc diethyl dithiocarbamate, Zinc dibutyl dithiocarbamate or Zinc ethylphenyldithiocarbamate or

Guanidine accelerator,
ι> such as diphenylguanidine or

Diorthotolylguanidine.

The dithiophosphates of the above formula used according to the invention can, for example, be straight-chain

.'ο Alkyl radicals with 2-18 carbon atoms per alkyl group or branched ones with preferably 4-8 carbon atoms per alkyl group, which differ from primary, derive secondary or tertiary alcohols. The cycloalkyl groups preferably have 6 carbons atoms in the ring and can e.g. B. by alkyl groups may be substituted by 1-20 carbon atoms or halogen.

The aryl groups are preferably phenyl groups, the z. B. substituted by alkyl groups or halogen

can be in. Such dithiophosphates are preferred used, which have a labile phosphorus-oxygen bond.

For the amino-dithiophosphates according to the invention, propylamine, triethylamine, dicyclohexylamine,

r> aniline, morpholine, ethylenediamine and hexamethylenediamine in question. For example, if Z is one of the divalent cations zinc or cadmium means 2, for monoamines such as propylamine 1 and for diamines 2.

-in The invention vulcanization processes may in the usual vulcanization, ie, carried out at 100-250 ⁰ C. All vulcanization processes, such as press heating, heating with superheated steam, hot air, salt bath, ultra-high frequency, are

• n reversible.

The rubbers to be vulcanized by the process according to the invention can be all customary Additives, such as fillers, e.g. carbon blacks or active silica, mineral oils, plasticizers, tackifiers,

) () Accelerators, activators, such as stearic acid, waxes, Anti-aging agents, anti-ozone agents, propellants, dyes or pigments.

The vulcanization process according to the invention is illustrated in more detail by the following examples. the

v, specified mechanical-technological data were determined in accordance with the relevant DIN regulations.

example 1

«) To a rubber mixture prepared in the usual way with the following composition:

Parts by weight Light crepe 100 Zinc oleate 2 Barium sulfate 75 zinc oxide 10 2,6-di-tert-butyl-p-cresol 1.5

the following substances are added (in parts by weight)
Table 1

Mix No. 2 3 4th 5 6th 1 0.3 _ 0.5 0.5 0.5 sulfur 2.5 - 2.5 - - - r ^ N'-dicaprolactam disulfide - 3.0 0.75 - - - N-Cyclohexyl ^ -Benzothiazyl-Sulfenamide 0.75 - - 0.75 - - 2-mercaptobenzo-thiazole - - - 2.0 2.0 2.0 Zinc di-n-butyldithiophosphate - - - - - 0.75 Zinc N-diethyldithiocarbamate - 2.0 - - - - Tetramethylthiuram disulfide - - - - 0.75 - Diphenylguanidine -

The finished test mixtures were 20 samples at 150 ° C for 2 days at 100 ° C after the corresponding

between 10 and 30 min. vulcanized and mechanical-technological see of the vulcanizates obtained Data determined In order to achieve comparable results, the optimally vulcanized

DIN regulation has been aged in hot air. The tensile strength of the aged sample was then determined again as a measure of the heat aging behavior.
In detail, the following measured values resulted:

Table 2 Mix No. 2 10 3 15th 4th 15th 5 15th Parts by weight 6th 10 1 44 34 33 28 100 26th Vulcanization time (min) 10 65 56 56 51 2 48 Hardness (Shore A) 46 5 4th 4th 2 75 2 Elasticity (%) 68 14th 9 10 5 10 5 ί a 100 (kp / cm ² ) 7 60 22nd 27 17th 1.5 13th Stress values I σ 300 (kp / cm ² ) 15 144 186 161 111 101 I σ 500 (kp / cm ² ) 51 68 131 138 103 100 Tensile strength (kgf / cm ² ) 189 53 30th 14th 7th 1 Tensile strength after aging (kp / cm ² ) 23 610 900 810 860 910 A Z (%) 88 the following composition Elongation at break (%) 745 A comparison, especially the percentage change tion of the tensile strength by aging shows that the Natural rubber using the Vulkanisa according to the invention Zinc oleate The vulcanizates produced in the process are 4-6 den Barium sulfate Vulcanizates 1–3 are clearly superior. These zinc oxide Vulcanizates 1-3 were made using the Known Vulkanisationsverfah listed at the beginning ren received. 2,6-di-tert-butyl-p-K.resol

B e 1 s ρ 1 e 1 2

In a further series of tests, a rubber mixture was produced in the usual way

Table 3

j _ewe j | _The following substances (in parts by weight) are added (dithiophosphate was abbreviated as DTP).

Mix No.
7 8 9

10 11 12 13 14 15 16 17 18

Sulfur 2.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

N-Cyclohexyl-benzothiazyl- 0.75 -----------

2-sulfenamide

2-mercaDtobenzothiazole - 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75

continuation

Diethyl DTP ethylenediamine salt

Diisopropyl-DTP-propylamine salt

Diisopropyl-DTP-triethylamine salt

Diisopropyl DTP hexamethylene diamine salt

Diisopropyl DTP dicyclohexyiamine salt

Di-n-butyl-DTP-ethylenediamine salt

Di-n-butyl-DTP-dicyclo-hexylamine salt

Diisopropyl DTP ethylenediamine salt

Diphenyl-DTP-ethylenediamine salt

Dicresyl-DTP-ethylenediamine salt

Di- (methyl-cyclohexyl) -DTP-ethylenediamine salt

Mix No. - 9 10 Il 7 8 - _ - _ 2.0 2.0 - - - 2.0 - _ _ 2.0

13th

14th

lh

17th

2.0 -

2.0 -

2.0 2.0

2.0 2.0

The above test mixtures were vulcanized as described above and the mechanical-technological Values determined. The optimally vulcanized samples were aged for 24 hours at 100 C.

Table 4

Mix No. 7 8 9

10

13th

14th

15th

".δ

17th

Vulcanization time (min) 20 20 10 10 10

Hardness (Shore A) 45 33 32 27 27

Elasticity (%) 63 52 57 50 52

ί σ 100 (kp / cm ² ) 6 3 3 3 3

Stress values I σ 300 (kp / cm ² ) 15 8 6 6 6

[ a 500 (kgf / cm ² ) 44 22 19 20 16

Tensile strength (kp / cm ² ) 177 154 147 125 98

Tensile strength after aging 7 113 120 89 95

(kp / cm ² )

Δ Ζ (%) 96 27 18 29 3

Elongation at break (%)

710 830 830 820 810

The results in Table 4 show the advantageous Effectiveness of the vulcanization process according to the invention with a large number of different dithiophosphates (Mixtures 8-18). For comparison, the data of a vulcanizate produced with the welding process (Mix 7).

Example 3

The following mixtures were tested for comparison:

55

60

Mix 19

Parts by weight

65

Light crepe
Zinc oleate

100 2

10

32

60

18th

152

115

20th

28

50

15th

120

88

20th

35

58

23

20th
26th
50

1
5
17th

147 124
106 117

20th

25th

50

17th

124

101

Mix 19 Parts by weight Barium sulfate 75 zinc oxide 10 2,2-methylend-bis- 1.5 (4-methyl-6-tert-butyl) - phenol are mixed in sulfur 2.0 N-cyclohexyl-2-benzo- 0.8 thiazolesulfenamide Zinc diisopropyldithio 2.2 phosphate

24 27 28 6 19 24 860 850 780 860 920 810

Mix 20

üew.-Tle.

Light crepe 100

Zinc oleate 2

Barium sulfate 75

Zinc oxide 10

2,6-di-tert-butyl- 1.5 pK resol
are mixed in

Sulfur 1.0

N-Cyclohexyl-2-benzo-0.8 thiazole sulfenamide

Zinc diisopropyldithio-2,2 phosphate

The mixtures were each vulcanized at 150.degree. The following values were obtained:

10

10

19th

Hardness (Sh A)
Elasticity (%)
a 100 (kp / cm ² )
σ 300 (kp / cm ² )
σ 500 (kp / cm ² )
Tensile strength (kp / cm ² )
Elongation at break (%)
Tensile strength after aging
2 Tg / 100 C hot air
A Z (%)

48

67

18th

49

104

600

43

59

The comparison of the ΔΖ values shows that the mixture with the sulfur content according to the invention has a significantly more favorable heat aging value.

Claims (1)

Claim: A process for the production of moldings by curing molding compounds from natural ^r, rubber, butadiene rubber, isoprene or butadiene-styrene, butadiene-acrylonitrile and isoprene-acrylonitrile Mischpolyinerisaten, sulfur and / or sulfur donors, known vulcanization accelerators, and dithiophosphates of the ι ο formula