DE4036420A1 - Low-settling vulcanised rubbers with no nitrosamine toxicity - contg. combinations of special substd. thiuram di:sulphide, metal di:thiocarbamate and N,N-bis-amido-di:sulphide vulcanisation agents - Google Patents

Abstract

Low settling vulcanised rubbers (I) are based esp. on natural rubber (NR), isoprene (IR) or butadiene rubber (BR), polychloroprene, (CR), SBR or NBR or blends thereof and have the compsn. (phr = pts./100 pts. rubber): 100 phr rubber compon-ent(s), 10-100 phr medium- to low-activity carbon black, 0.5-5 phr Zn 2-ethylhexanoate and/or Zn stearate and/or stearic acid, 0.50 phr plasticiser, 1-3 phr anti-ozone wax, 0.5-4 phr p-phenylenediamine and/or polyalkyl-dihydroquinoline anti-ageing additive, 2-10 phr ZnO, x phr vulcanisation agents (A) (combination), 0.2-2 phr sulphur and up to 50 phr other additives; combination (A) comprises 0.3-3 phr cpd. of formula (II) and/or (III) 0.3-3 phr MBTS and/or MMBT and/or chemical equiv. of MBT salts and 0-4 phr cpd. (IV) (A1), or 0.2-3 phr (II) and/or (III), 0.3-2.5 phr TBBS and/or equiv. of other sulphenamides and 0-4 phr (IV) (A2), or 0.3-2.5 phr (II) and/or (III), 0.3-2 phr TBBS or equiv. 0.3-2 phr MBTS and/or MBT salt, and 0-4 phr (IV) (A3); total no of C atoms in the R gps. = at least 16 in (II), at least 8 in (III) and at least 4 in (IV). n = at least 1 in cpd. (II), at least 1 (pref. at least 2) in (III) and at least 1 in (IV) M = metal atom. USE/ADVANTAGE- The invention provides low-settling vulcanised rubber compsns. (I) with no nitrosamine toxicity and a combination of high crosslink density and long Mooney scorch time. (I) are useful esp. for the prodn. of engine bearings.

Description

The properties of low-settlement rubber qualities (e.g. as Part of engine mounts) are required for reasons of Property levels and the favorable processing properties the mixture according to the previously known state of the Technology through the use of vulcanization accelerators or crosslinkers of the type

represents, wherein R₁ to R₄ individually organic radicals or Represent hydrogen or the pairs R₁, R₂ and R₃, R₄, both or individually, a closed ring on the nitrogen, e.g. B. R₁, R₂ = (CH₂) ₂-O- (CH₂) ₂, can form.

It is a type whose chemical-structural Relationship to dithiocarbamates on the one hand and sulfenamides on the other hand is unmistakable. This is the unique case an active substance, with whose help it succeeded, which otherwise only with appropriately substituted dithiocarbamates and / or Thiuramen to achieve high networking density with the Sulfenamiden's own great scorch safety in one To combine substance in an ideal way.  

However, the type of accelerator mentioned has the decisive one Disadvantage, with the rubber compound always in sufficient Amount of nitroso group carriers present with release toxic N-nitrosamines to react both during the Vulcanization expelled as well as in the storage of the rubber article be constantly imitated in the atmosphere. N-nitrosamines have been shown to be carcinogenic in animal experiments.

The object of the invention is a non-nitrosamine toxic Vulcanizate to provide both the essential Characteristics of highly cross-linked, especially low-settling rubber qualities has as well as the most necessary Ensure the high level of soot filling necessary scorch safety can.

There are two main ways to achieve the set goal difficulties that appear insurmountable, namely

• 1) the fact that none (neither non-nitrosamine toxic also accelerator or nitrosamine toxic) Crosslinker type is known, which is the above Combination of effects of high networking density with high Scorch time combined in such a way; such as
• 2) the fact that all available non-nitrosamine toxic Vulcanizing agent from thiuram / dithiocarbamate Type have a much weaker networking potential.

This task is solved by the characteristic composition according to claim 1, wherein the alternative use of Component systems (A, B, C) are essential:

Component system A
Vulcanizing agents (I) and / or (II)
- MBTS and / or MBT and / or chem. Equivalents of the MBT salts
- sulfur

Component system B
Vulcanizing agents (I) and / or (II)
- TBBS and / or chem. Equivalents of other sulfenamides
- sulfur

Component system C
Vulcanizing agents (I) and / or (II)
- TBBS and / or chem. Equivalents of other sulfenamides
- MBTS and / or MBT and / or chem. Equivalents of the MBT salts
- sulfur

The short names used here mean:

MBT 2-mercapto-benzothiazole
MBTS 2-mercapto-benzothiazyl disulfide
TBBS N-tertiary butyl-2-benzothiazylsulfenamide

As an additional component of these component systems can optionally the vulcanization system (III) can be used.

Within the following experimental section Recipes and physical properties of engine mounts (Examples α to δ; Table 1, 2) recorded. Β, γ and δ represent formulations according to the invention represents, while α contains a conventional recipe.  

Table 1

Table 2

Claims (9)

1. Low-settling vulcanizates, particularly based on natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), polychloroprene (CR), styrene-butadiene rubber (SBR), nitrile rubber (NBR) or their blends , without nitrosamine toxic properties, characterized by the following composition (in phr): the vulcanizing agents (I, II, III) have the following basic structures: (Σ R₁, R₂, R₃, R₄16 carbon atoms; n1) (Σ R₁, R₂8 C atoms; n1, especially n2; M = metal atom) (Σ R₁, R₂, R₃, R₄4 atoms; n1) 2. Vulcanizates according to claim 1, characterized in that the substituents R₁ to R₄ are the same or different. 3. Vulcanizates according to claim 2, characterized in that the substituents aliphatic, aromatic or mixed are aliphatic-aromatic hydrocarbons. 4. Vulcanizates according to claim 2 or 3, characterized in that the following structural parameters apply with regard to the vulcanizing agents (I, II):

• (I) R₁ = R₂ = R₃ = R₄ = benzyl; n = 2 [tetrabenzyl-thiuram disulfide],
• (II) R₁ = R₂ = benzyl; n = 2; M = zinc [zinc-N, N-dibenzyldithio-carbamate].

5. Vulcanizates according to claim 2, characterized in that the substituents contain hetero and / or halogen atoms. 6. Vulcanizates according to one of claims 2, 3 or 5, characterized characterized in that the substituents R₁, R₂ or R₃, R₄ are connected together in a ring. 7. Vulcanizates according to claim 6, characterized in that the following structural parameters apply with regard to the vulcanizing agents (I, II):

• (I) R₁, R₂ = R₃, R₄ = (CH₂-CH₂) ₂NCH₃; n = 2 [bis (4-methylpiperazino) thiuram disulfide],
• (II) R₁, R₂ = (CH₂-CH₂) ₂NCH₃; n = 2; M = zinc [zinc bis (4-methylpiperazino) dithiocarbamate].

8. Vulcanizates according to claim 6, characterized in that the following structural parameters apply with regard to the vulcanizing agent (III):
R₁, R₂ = R₃, R₄ = (CH₂) ₅; n = 2 [N, N'-bis (caprolactam) disulfide].