Mixtures Containing an Aminically Crosslinkable Rubber and Polyethyleneimine

Abstract

The invention relates to mixtures containing at least one aminically crosslinkable rubber and a cross-linking system, which consists of at least one crosslinker and optionally at least one vulcanization accelerator, the at least one crosslinker containing polyethylene imine. The invention further relates to the production and to the use of said mixtures; and to the vulcanized products that can be obtained from the mixture, in particular in the form of rubber articles, in particular seals, hoses, membranes and o-rings.

Claims

1. A mixture comprising at least one aminically crosslinkable rubber and a crosslinking system consisting of at least one crosslinker and optionally at least one vulcanization accelerator, wherein the at least one crosslinker comprises polyethyleneimine and wherein the total content of the vulcanization accelerators diphenylguanidine (DPG), di-ortho-tolyl-guanidine (DOTG) and 1-(ortho-tolyl)biguande of the crosslinking system in the mixture is not more than 0.4 phr.

2. The mixture as claimed in claim 1, wherein the crosslinking system consists to an extent of ≥80% by weight, based on the total mass of the crosslinking system, of at least one crosslinker, wherein the at least one crosslinker comprises polyethyleneimine.

3. The mixture as claimed in claim 1, wherein the at least one crosslinker comprises polyethyleneimine and at least one diamine.

4. The mixture as claimed in claim 1, wherein the at least one crosslinker consists of polyethyleneimine and at least one diamine.

5. The mixture as claimed in claim 1, wherein the at least one crosslinker consists of polyethyleneimine.

6. The mixture as claimed in claim 1, wherein the content of polyethyleneimine is from 0.001 to 20 phr.

7. The mixture as claimed in claim 3, wherein the content of the at least one diamine, is from 0.01 bis 5 phr.

8. The mixture as claimed in claim 1, wherein the at least one aminically crosslinkable rubber is a carboxyl-containing rubber.

9. The mixture as claimed in claim 3, wherein the at least one aminically crosslinkable rubber is an ACM rubber, the content of polyethyleneimine is 0.01 to 10 phr, and the content of the at least one diamine is 0.01 to 5 phr.

10. The mixture as claimed in claim 1, wherein the mixture comprises at least one support selected from the group consisting of neutral, acidic and basic silica on which the at least one crosslinker is absorbed and/or adsorbed.

11. A process for producing a mixture as claimed in claim 1, comprising mixing in a first step the at least one crosslinker and optionally the at least one vulcanization accelerator and adding in a second step the at least one aminically crosslinkable rubber to the mixture obtained after the first step.

12. A process for producing rubber vulcanizates, comprising vulcanizing the mixture according to claim 1.

13. A vulcanizate produced by vulcanizing the mixture according to claim 1.

14. A rubber article comprising one or more vulcanizates as claimed in claim 13.

15. A vehicle comprising at least one rubber article as claimed in claim 14.

16. (canceled)

17. A crosslinking system for crosslinking at least one aminically crosslinkable rubber, consisting of ≥80% by weight, based on the total mass of the crosslinking system, of at least one crosslinker, and optionally at least one vulcanization accelerator, wherein the at least one crosslinker comprises polyethyleneimine and optionally at least one diamine, and the total content of the vulcanization accelerators diphenylguanidine (DPG), di-ortho-tolyl-guanidine (DOTG) and 1-(ortho-tolyl)biguanide of the crosslinking system is not more than 0.4 phr, based on the at least one aminically crosslinkable rubber.

18. The mixture as claimed in claim 3, wherein the at least one aminically crosslinkable rubber is an AEM rubber, the content of polyethyleneimine is 0.01 to 10 phr, and the content of the at least one diamine is 0.01 to 5 phr.

19. The mixture as claimed in claim 1, wherein the crosslinking system consists to an extent of ≥95% by weight, based on the total mass of the crosslinking system, of at least one crosslinker, wherein the at least one crosslinker comprises polyethyleneimine.

20. The mixture as claimed in claim 3, wherein the at least one diamine is selected from the group consisting of hexamethylenediamine (HMD) and hexamethylenediamine carbamate (HMDC).

21. The mixture as claimed in claim 1, wherein the at least one aminically crosslinkable rubber is a carboxyl-containing rubber selected from the group consisting of ACM and AEM rubbers.

Description

EXAMPLES

Determination of Properties of Rubber Mixtures/Vulcanizates

Rheometer (Vulcameter) Complete Vulcanization Time (T90) 180° C., Scorch Time (T10), Degree of Crosslinking

[0134] The MDR (moving die rheometer) vulcanization profile and analytical data associated therewith are measured in an MDR 2000 Monsanto rheometer in accordance with ASTM D5289-95. The scorch time T10 is the time at which 10% of the rubber is crosslinked. The complete vulcanization time T90 is the time at which 90% of the rubber has been crosslinked. The degree of crosslinking is measured as the difference between the highest and lowest torque value and is a measure of crosslinking density. The selected temperature was 180° C.

Tensile Strength, 20 Modulus, 50 Modulus, 100 Modulus

[0135] These measurements were effected in accordance with DIN 53504 (tensile test, rod S 2).

Compression Set (CS)

[0136] The CS values were obtained after compression of the sample by 25% at 125° C. and a hold time at this temperature of 24 hours. The CS values were determined after a relaxation time of 30 min (DIN ISO 815).

Production of Rubber Mixtures and Rubber Vulcanizates

[0137] Rubber mixtures were initially produced from the constituents of the rubber mixtures of (comparative) examples 1-12 reported in tables 2, 3, 5 and 6. The respective constituents were then mixed in a respective mixing process as described below.

[0138] The constituents of the rubber mixtures of (comparative) examples 1-12 reported in tables 2, 3, 5 and 6 (more particularly described in table 1) were in each case mixed in a so-called “upside down” process. Carbon black, Aflux® 18, Vanfre® VAM, stearic acid, Naugard® 445 and depending on the formulation, Rhenosin® W 759, Rhenogran® HMDC-70, Rhenogran® DOTG-70, Rhenogran® XLA-60 and/or Lupasol® PR 8515 were initially charged in a kneader (GK 1.5) and mixed at a temperature of 50° C. and at about 40 revolutions/min. After about 1 min, half of the rubber Racrester™ CH/VAMAC® G was added and the mixture was mixed for a further minute. After 2 min the remainder of the rubber was added until a torque equilibrium was achieved and the mixture was discharged. The mixture was subsequently transferred to a temperature-controlled roller to obtain a rolled sheet for further processing. The roller temperature was 25° C.

[0139] The obtained rubber mixtures of (comparative) examples 1-12 were subjected to complete vulcanization at 180° C. and subsequently heat-treated at 175° C. for 4 hours. The pressure was 300 bar.

TABLE-US-00001 TABLE 1 Trade name, description and manufacturer/marketer of constituents of rubber mixtures from tables 2 and 3 and tables 5 and 6 Trade name Description Manufacturer/marketer Racrester ™ CH ACM rubber Osaka Soda Co. Ltd VAMAC ® G AEM rubber DuPont Corax ® N-550 Carbon black CB N550 Orion Engineered Carbons GmbH Rhenogran ® DOTG-70 Diorthotolylguanidine LANXESS Deutschland GmbH Aflux ® 18 Flow promoter (primary fatty amine) LANXESS Deutschland GmbH Vanfre ® VAM Demolding agent (phosphate ester) Vanderbilt Chemicals, LLC Stearic acid Processing aid Peter Greven GmbH und Co. KG Rhenosin ® W 759 Processing aid (mixture of ether/ester) LANXESS Deutschland GmbH Naugard ® 445 Aging stabilizer 4,4′-bis(alpha,alpha- Addivant dimethylbenzyl)diphenylamine Rhenogran ® HMDC- Hexamethylenediamine LANXESS Deutschland 70/AEMD carbamate GmbH Rhenogran ® XLA-60 Activated DBU LANXESS Deutschland GmbH Lupasol ® PR 8515 Polyethylenimine, CAS-No.: BASF AG 25987-06-8

TABLE-US-00002 TABLE 2 Constituents of rubber mixtures (comparative examples 1-3) Comparative Comparative Comparative example 1 example 2 example 3 % by % by % by phr wt. phr wt. phr wt. Corax ® N-550 55.00 34.35 55.00 34.06 55.00 33.93 Aflux ® 18 0.50 0.31 0.50 0.31 0.50 0.31 Vanfre ® VAM 1.00 0.62 1.00 0.62 1.00 0.62 Stearic acid 1.00 0.62 1.00 0.62 1.00 0.62 Naugard ® 445 2.00 1.25 2.00 1.24 2.00 1.23 Powder Rhenogran ® 0.60 0.37 0.60 0.37 HMDC-70/AEMD Racrester ™ CH 100.00 62.46 100.00 61.92 100.00 61.69 Rhenogran ® 2.00 1.24 2.00 1.23 DOTG-70

TABLE-US-00003 TABLE 3 Constituents of rubber mixtures (comparative example 4 and inventive examples 5 and 6) Comparative Example 5 (of Example 6 (of example 4 the invention) the invention) % % % phr by wt. phr by wt. phr by wt. Coraxe N-550 55.00 33.93 55.00 34.30 55.00 34.32 Aflux ® 18 0.50 0.31 0.50 0.31 0.50 0.31 Varifre ® VAM 1.00 0.62 1.00 0.62 1.00 0.62 Stearic acid 1.00 0.62 1.00 0.62 1.00 0.62 Naugard ® 445 2.00 1.23 2.00 1.25 2.00 1.25 Powder Rhenogran ® 0.60 0.37 0.60 0.37 HMDC- 70/AEMD Racrester ™ CH 100.00 61.69 100.00 62.36 100.00 62.40 Rhenogran ® DOTG-70 Lupasol ® PR 0.25 0.16 0.75 0.47 8515 Rhenogran ® 2.00 1.23 XLA-60

[0140] Reported amounts are in phr (parts by weight per 100 parts rubber) and percent by weight (based on the total weight of the rubber mixture).

[0141] The produced rubber mixtures of (comparative) examples 1-12 and the vulcanizates obtainable therefrom were subjected to the technical tests specified hereinbelow. The determined values are reported in tables 4, 7 and 8. The rubber mixtures of examples 5, 6, 11 and 12 and the vulcanizates obtained therefrom, whose results are shown under “Example 5”, “Example 6”, “Example 11” and “Example 12” in tables 4, 7 and 8, are inventive.

[0142] The mixing steps and the sequence of additives may be varied as desired and polyethyleneimine may be added in any desired mixing step.

TABLE-US-00004 TABLE 4 Results of technical tests Example 5 Example 6 Comparative Comparative Comparative Comparative (of the (of the example 1 example 2 example 3 example 4 invention) invention) Scorch time T10 29.0 18.0 30.0 30.0 31.0 26.0 [sec] Complete 571.0 520.0 335.0 346.0 499.0 445.0 vulcanization time T90 [sec] Degree of 2.4 0.5 4.0 3.7 7.2 6.8 crosslinking (Fmax-Fmin) Tensile strength 5.9 8.6 7.3 9.5 8.8 [MPa] 20% tensile 0.3 0.4 0.4 0.5 0.5 modulus [MPa] 50% tensile 0.5 0.6 0.6 1.1 1.2 modulus [MPa] 100% tensile 0.8 1.2 1.0 3.1 3.3 modulus [MPa] Compression 24.0 19.0 25.0 15.0 27.0 set [%]

Inventive Example 5 Compared to Comparative Examples 3 and 4

[0143] Comparative example 3 represents a standard crosslinking formulation for an ACM rubber known to those skilled in the art. In addition to rubber, processing aids and carbon black it comprises 0.37% by weight of crosslinker HMDC and 1.23% by weight of the vulcanization accelerator DOTG. The inventive formulation in example 5 comprises only 0.16% polyethyleneimine instead of the guanidine accelerator DOTG. While retaining the short scorch time T10 an advantageous reduction in compression set and advantageous increase in degree of crosslinking and tensile strength are achieved.

[0144] The same applies to a comparison of the inventive rubber mixture according to example 5 with the rubber mixture according to comparative example 4 which comprises DBU as a guanidine substitute and as mentioned in more detail above represents a known standard crosslinking formulation for an ACM rubber.

Inventive Example 6 Compared to Comparative Examples 1 and 3

[0145] In a sole departure from the rubber mixture from comparative example 3, the rubber mixture according to comparative example 1 comprises no vulcanization accelerator. Crosslinking is effected only via the crosslinker HMDC (0.37% by weight) without vulcanization accelerator. Crosslinking is therefore markedly slower (longer T90), degree of crosslinking and tensile strength are lower and compression set is greater. The inventive mixture of example 6 also comprises no vulcanization accelerator but utilizes 0.47% by weight of polyethyleneimine instead of HMDC as crosslinker. Compared to comparative example 1 a faster complete vulcanization time T90 is observed while retaining a short scorch time T10. The degree of crosslinking, tensile strength and moduli at 20%, 50% and 100% extension are higher and therefore more advantageous. Even the standard crosslinking formulation known to those skilled in the art according to comparative example 3 is surpassed in terms of degree of crosslinking, tensile strength and moduli.

Comparative Example 2

[0146] Comparative example 2 shows the standard crosslinking formulation of comparative example 3 without the crosslinker HMDC and thus only with the vulcanization accelerator DOTG alone. No crosslinking reaction took place using only DOTG alone.

TABLE-US-00005 TABLE 5 Constituents of AEM rubber mixtures (comparative examples 7-9) Comparative Comparative Comparative example 7 example 8 example 9 % by % by % by phr wt. phr wt. phr wt. VAMAC ® G 100.00 57.77 100.00 56.59 100.00 55.93 Corax ® N-550 60.00 34.66 60.00 33.96 60.00 33.56 Naugard ® 445 2.00 1.16 2.00 1.13 2.00 1.12 Powder Rhenosin ® W 6.00 3.47 6.00 3.40 6.00 3.36 759 Vanfre ® VAM 1.00 0.58 1.00 0.57 1.00 0.56 Aflux ® 18 0.50 0.29 0.50 0.28 0.50 0.28 Rhenogran ® 2.10 1.21 2.10 1.17 HMDC- 70/AEMD Rhenogran ® 5.70 3.23 5.70 3.19 DOTG-70 Stearic acid 1.50 0.87 1.50 0.85 1.50 0.84

TABLE-US-00006 TABLE 6 Constituents of rubber mixtures (comparative example 10 and inventive examples 11 and 12) Comparative Example 11 Example 12 example 10 (inventive) (inventive) % by % by % by wt. phr wt. phr wt. VAMAC ® G 100.00 57.77 100.00 57.52 100.00 57.72 Corax ® N-550 60.00 34.66 60.00 34.51 60.00 34.63 Naugard ® 445 2.00 1.16 2.00 1.15 2.00 1.15 Powder Rhenosin ® W 6.00 3.47 6.00 3.45 6.00 3.46 759 Vanfre ® VAM 1.00 0.58 1.00 0.58 1.00 0.58 Aflux ® 18 0.50 0.29 0.50 0.29 1.00 0.58 Rherlograne 2.10 1.21 2.10 1.21 HMDC- 70/AEMD Rhenogran ® DOTG-70 Stearic acid 1.50 0.87 1.50 0.86 1.50 0.87 Lupasol ® PR 0.75 0.43 1.75 1.01 8515 Rhenogran ® 2.00 XLA-60

[0147] Reported amounts are in phr (parts by weight per 100 parts rubber) and percent by weight (based on the total weight of the rubber mixture).

TABLE-US-00007 TABLE 7 Results of technical tests (examples 7-9) Comparative Comparative Comparative example 7 example 8 example 9 Scorch time 49.0 26.0 43.0 T10 [sec] Complete 1278.0 668.0 469.0 vulcanization time T90 [sec] Degree of 10.8 0.3 13.3 crosslinking (Fmax-Fmin) Tensile 16.3 14.5 strength [MPa] 20% tensile 4.7 1.1 modulus [MPa] 50% tensile 2.3 2.2 modulus [MPa] 100% tensile 4.9 5.0 modulus [MPa]

TABLE-US-00008 TABLE 8 Results of technical tests (comparative example 10 and inventive examples 11 and 12) Comparative Example 11 Example 12 example 10 (inventive) (inventive) Scorch time T10 44.0 46.0 30.0 [sec] Complete 501.0 773.0 634.0 vulcanization time T90 [sec] Degree of 13.4 18.1 11.9 crosslinking (Fmax-Fmin) Tensile strength 17.0 15.6 14.2 [MPa] 20% tensile 1.3 1.4 1.4 modulus [MPa] 50% tensile 2.8 3.4 3.6 modulus [MPa] 100% tensile 6.4 7.8 8.6 modulus [MPa]

Inventive Example 11 Compared to Comparative Examples 9 and 10

[0148] Comparative example 9 represents a standard crosslinking formulation for an AEM rubber known to those skilled in the art. In addition to rubber, processing aids and carbon black it comprises 1.17% by weight of crosslinker HMDC and 3.19% by weight of the vulcanization accelerator DOTG. The inventive formulation in example 11 comprises only 0.43% by weight of polyethyleneimine instead of the guanidine accelerator DOTG. While retaining a similarly short scorch time T10, an advantageous increase in the degree of crosslinking, tensile strength and tensile moduli at 20%, 50% and 100% elongation are achieved.

[0149] Similar advantages are revealed by a comparison of the inventive rubber mixture according to example 11 with the rubber mixture according to comparative example 10 which comprises DBU as a guanidine substitute and as mentioned in more detail above likewise represents a known standard crosslinking formulation for an ACM rubber.

Inventive Example 12 Compared to Comparative Examples 7 and 9

[0150] In a sole departure from the rubber mixture from comparative example 9, the rubber mixture according to comparative example 7 comprises no vulcanization accelerator. Crosslinking is effected only via the crosslinker HMDC (1.21% by weight) without vulcanization accelerator. The crosslinking is thus markedly slower (longer T90) and the degree of crosslinking is lower. The inventive mixture of example 12 also comprises no vulcanization accelerator but utilizes 1.01% by weight of polyethyleneimine instead of HMDC as crosslinker. Compared to comparative example 7 a markedly faster complete vulcanization time T90 is observed while retaining a short scorch time T10. The degree of crosslinking and the moduli at 50% and 100% extension are higher and therefore more advantageous. Even the standard crosslinking formulation known to those skilled in the art according to comparative example 9 is surpassed in terms of stress moduli at 20%, 50% and 100% extension while retaining similar tensile strength.

Comparative Example 8

[0151] Comparative example 8 shows the standard crosslinking formulation of comparative example 9 without the crosslinker HMDC and thus only with the vulcanization accelerator DOTG alone. No crosslinking reaction took place using only DOTG alone.

[0152] In summary it has surprisingly been found that the use of polyethyleneimine instead of the guanidine-containing vulcanization accelerator DOTG or instead of the crosslinker HMDC or instead of both HMDC and DOTG makes it possible to provide rubber mixtures whose performance properties are not only at the same level as those of the guanidine- and/or HMDC-containing equivalents but rather are even advantageously set apart therefrom, in particular in terms of the tensile strength, moduli and degree of crosslinking of the vulcanizates obtainable therefrom.