DE1470881B - Process for vulcanizing blends of natural rubber and cis-1,4-polybutadiene - Google Patents

Description

The invention relates to a method for vulcanizing blends of natural rubber and eis-1,4-polybutadiene, which contain carbon black, extender oil, adhesive resin, Zinc oxide, stearic acid, dibenzothiazyl disulfide, tetramethylthiuram disulfide, other anti-aging agents and optionally contain up to 1 part by weight of sulfur, based on the weight of the rubber blends, under pressure and heat.

Research has shown that elemental sulfur is detrimental to cis-1,4-polybutadiene acts and thereby the conversion from the cisin to the trans form is favored, a process that does not occur with natural rubber. Just 1.5 parts of elemental sulfur are enough to introduce this Change. On the other hand, this sulfur content is the smallest possible for a normal accelerator system the same amount as contained in the mixtures for good physical results have to be.

Vulcanizates made from blends of natural rubber and ice-1,4-polybutadiene are already known, their mixtures 0.5 to 1.5 parts by weight of sulfur, based on the total amount of rubber blended, contain. The vulcanization is carried out with a conventional vulcanization system. Mixtures of this type require extremely long heating times if the properties of standard vulcanizates to be achieved, their mixtures with the same vulcanization system and the same accelerator types contain higher amounts of sulfur. Are generated from known non-standard mixtures Vulcanizates processed into vehicle tires, then heat generation and hysteresis in them too high values, which must lead to the immediate wear of the tire in operation.

The invention is based on the task of developing a new vulcanization system with which which is latent through the new cis-1,4-polybutadiene given possibilities can be activated more fully. The current knowledge to manufacture of mixtures of ice 1,4-polybutadiene and of Vulcanizates of the same are based on test results carried out with natural rubber. Will the course followed the development of the vulcanizing agent systems, the surprising finding emerges that that this is behind the development of new polymers, e.g. B. the cis-1,4-polybutadiene and the others Additives that are lagging behind. Accordingly, it has been used up to now for natural rubber and so far known synthetic rubbers use the same VuI-Kanisiermittel. The consequence is that the properties the vulcanizates of the new polymers do not quite meet the requirements that z. B. in Field of technical rubber articles, such as vehicle tires, pulley linings and the like.

The task was therefore to find a vulcanization system with a minimum amount works on elemental sulfur or only with sulfur-releasing substances and thereby one Prevents isomerization of the cis-1,4-polybutadiene.

If the configuration of the polymer changes from the beginning due to isomerization, these additives can do not improve aging. The aging values probably show with the various Vulcanizates have the same degradation, but the chemical degradation mechanism during aging is different and depending on various factors. The criterion for practical use is good Vulcanizing agent systems are good physical properties of the VuI-Kanisate before and after aging.

It has now been found that aging-resistant vulcanizates with good physical properties be achieved when vulcanizing mixtures that also contain mercaptobenzothiazole, p, p'-dibenzoylquinone dioxime as well as mercaptobenzimidazole.

It was also found that an addition of 4,4'-dithiodimorpholine instead of elemental sulfur brings further advantages.

The accelerators built into the vulcanization system according to the invention are on the others Mixture components matched so that the polar and radical system during vulcanization is taken into account and a stable vulcanizate is created.

The following results of the mixing examples A to H with the vulcanizing agent system according to the invention leave the advantages compared to the test results of vulcanizates presented below known mixtures V 01 and V 02 (from cis-l ^ -Polybutadiene- natural rubber blends recognize well.

Recipes mixes

Natural rubber

cis-1,4-polybutadiene

Very highly abrasion-resistant furnace soot ...

Zinc oxide

Stearic acid

N-phenyl-N'-isopropyl-p-phenylene-

diamine

Phenyl-a-naphthylamine

Mercaptobenzimidazole

Adhesive resin

Plasticizers

4,4'-dithiomorpholine

oleosulfur-0.2

40.0

60.0

70.0

3.0

2.0

1.5
1.0
1.0
5.0
18.0
0.6

40.0

60.0

70.0

3.0

2.0

1.5
1.0
1.0
5.0
18.0

0.55

40.0

60.0

60.0

3.0

2.0

1.5
1.0
1.0
5.0
12.0
0.6

40.0

60.0

60.0

3.0

2.0

1.5
1.0
1.0
5.0
12.0

0.55

continuation

Mercaptobenzothiazole

Tetramethylthiuramdisulnd ..

Dibenzothiazyl disulfide

ρ, ρ'-dibenzoyl-quinonedioxime

0.5 0.1 2.0 1.5

B. C. D. 0.5 " 0.5 0.5 0.1 0.1 0.1 2.0 2.0 2.0 1.5 1.5 1.5 Mixtures

Test results

Heating at 143 ° C

45 '

60 '

45 '

60 '

45 '

60 '

45 '

Modulus at 300% (kg / cm ² ). Modulus at 500% (kg / cm ² ). Tensile strength (kg / cm ² ) .....

Elongation at break (%)

Shore hardness ( ⁰ A)

Elasticity (%)

Notch toughness (kg / cm)

Pull-out strength (kg / cm) ... Mooney vulcanization (i ₅ )

66

120

125

520

65

25th

31

69

68

124

128

525

66

26th

35

81

98-

156
460

71

27

31

91

62

120

142

595

63

28

40

83

121

150

615

65

30th

36

77

98

172

172

'505

68

30th

29 ^:

75

10 '

29 '

Aging for 3 days at 100 ° C

Module at 300% (kg / cm ² ) .. module at 500% (kg / cm ² ) ..

Tensile strength (kg / cm ² )

Elongation at break (%)

Shore hardness (° A)

Elasticity (%)

Notch toughness (kg / cm)

Pull-out strength (kg / cm) ....

86

132 132 455 465 66 60 23 ' 23 30th 26th 84 69

122

170
375
72
27
18th
66

81

140

152

550

64

28

33

70

134

138

520

Recipes

130

150 350 72 31 15 52

Mixtures

Natural rubber

cis-1,4-polybutadiene

Very highly abrasion-resistant furnace soot ....

Highly abrasion-resistant furnace soot

Zinc oxide

Stearic acid

N-phenyl-N'-isopropyl-p-phenylene-

diamine

Phenyl-o-naphthylamine

Mercaptobenzimidazole

Adhesive resin

Plasticizers

4,4'-dithiomorpholine

oleosulfur-0.2

Mercaptobenzothiazole

Tetramethylthiuram disulfide

Dibenzothiazyl disulfide

ρ, ρ'-dibenzoyl-quinonedioxime

40.0 60.0 60.0

3.0 2.0

1.5 1.0 1.0 5.0 18.0 0.6

0.5 0.1 2.0 1.5

40.0
60.0
60.0

3.0
2.0

1.5
1.0
1.0
5.0
18.0

0.55

0.5

0.1

2.0

1.5

40.0
60.0

70.0
3.0
2.0

1.5
1.0
1.0
5.0
25.0
0.3
0.33
0.5
0.1
2.0
1.5

40.0 60.0 70.0

3.0 2.0

1.5 1.0 1.0 5.0 25.0

0.44

0.5

0.1

2.0

1.5

Test results

Heating at 143 ° C

45 '

60 '

45 '

60 '

45 '

60 '

45 '

Module at 300% (kg / cm ² ) .. module at 500% (kg / cm ² ) ..

Tensile strength (kg / cm ² )

Elongation at break (%)

Shore hardness ( ⁰ A)

Elasticity (%)

Notch toughness (kg / cm)

Pull-out strength (kg / cm)

Mooney vulcanization (i ₅ )

64

126

160

625

30th

37

80

64

126

158

615

61

31

37

75

154
485
66
35
28
78

158

161

505

88

166

166

510

63

40

23

74

84

182

194

530

65

38

22nd

69

80

146

166

565

67

36

27

9 '

27 '

82 150 160 535 67 37 35 84 over 30 '

Aging for 3 days at 100 ^° C

Module at 300% (kg / cm ² ) .. module at 500% (kg / cm ² ) ..

Tensile strength (kg / cm ² )

Elongation at break (%)

Shore hardness ( ⁰ A)

Elasticity (%)

Notch toughness (kg / cm)

Pull-out strength (kg / cm)

Recipes

84

154

505

62

39

26th

cis-1,4-polybutadiene

Natural rubber

Very highly abrasion-resistant furnace soot

Zinc oxide

Stearic acid

N- phenyl-N'-isopropyl-

p-phenylenediamine

Phenyl-a-naphthylamine

N- phenyl-N'-cyclohexyl-

p-phenylenediamine

Adhesive resin

Plasticizers

oleosulfur-0.2

2-morpholino-mercaptobenz-

thiazole

Test results mixtures
V 01 V 02

60.0

40.0

60.0

3.0

2.0

1.5 1.0

1.0

5.0

12.0

2.2

1.5 60.0

40.0

60.0

3.0

2.0

1.5
1.0

1.0
5.0
12.0
1.65

1.5

Heating at 143 ° C

Module at 300%

(kg / cm ² )

Module at 500%

(kg / cm ² )

Tensile strength (kg / cm ² ) .. Elongation at break (%) ....

Shore hardness (A)

Elasticity (%)

VOl 45 '60'

86

174

181

515

60

39

82

170

186

535

60

42 V 02
45 '60'

79

170

192

545

60

40

116

146
375
70
44
13th
65

116

145
380
70
42
15th
64

114

146 380 66 40 24 62

120

136 340 67 42 18 65

108

147 415 70 39 19 74

Aging for 3 days at 100 ° C

Module at 300% (kg / cm ² )

Module at 500% (kg / cm ² )

Tensile strength (kg / cm ² ) .. Elongation at break (%) ....

Shore hardness ("A)

Elasticity (%)

Mooney-. _s vulcanization (r ₅ )

VOl

124

235

72

42

132

255

70

45

28 '

ν

118

245

71

37

27 '

The above test results show that the physical values of the vulcanizate before and after aging have a quality that is consistent with the

conventional procedure was not achieved. The additional use of 4,4'-dithiomorpholine prevents the occurrence of isomerization as well as those contained in Mixture Examples A, C and E. small amount of elemental sulfur largely.

The 4,4'-dithiomorpholine contained in the vulcanizing agent system according to the invention mediates a short Mooney scorch, elemental sulfur, on the other hand, a higher Mooney value. When Explanation for this is assumed that 4,4'-dithio-

morpholine and ρ, ρ'-dibenzoyl-quinonedioxime with one another react and form an active product, which in turn reacts with the rubber molecules.

The effect of the small amount of elemental sulfur in the individual mixtures is good. Module,

Strength and the other physical properties are better except for one thing lower cut resistance compared to the mixtures containing 4,4'-dithiomorpholine. Interesting is,

that the elemental sulfur in the vulcanization system according to the invention is not only used as a vulcanizing agent, but also acts as a retarder.

In summary, it can be expressed that using the inventive Vulcanization system produced vulcanizates of a blend of cis-1,4-polybutadiene and Natural rubber are well suited for practical use in treads for pneumatic vehicle tires.

Claims (2)

Patent claims: 1. Process for vulcanizing blends of natural rubber and cis-1,4-polybutadiene, the carbon black, extender oil, adhesive resin, zinc oxide, stearic acid, Dibenzothiazyl disulphide, tetramethylthiuramidisulphide, other anti-aging agents and optionally up to 1 part by weight of sulfur, based on the weight of the rubber blends, contain, under the application of pressure and heat, characterized that mixtures are vulcanized which also contain mercaptobenzothiazole, p, p '- dibenzoylquinone dioxime as well as mercaptobenzimidazole. 2. The method according to claim 1, characterized in that instead of sulfur Dithiodimorpholine used. 009 552/358