JPH0365828B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber composition with improved processability or cold flow properties. Various diene rubbers are characterized by carbon-carbon double bonds present in their chains that enable sulfur crosslinking, and various structures are widely used for rubber and other purposes depending on their properties. . These diene rubbers generally have a larger polymer molecular weight, and the more linear they are, the better they are in various rubber physical properties, such as strength and elasticity.However, on the contrary, they have poor processability, such as mixability in Banbury work, operability in roll work, and extrusion work. In many cases, products obtained using rubber with poor processability are inferior in terms of skin, edges, etc. Furthermore, in some cases, for example, when the diene rubber is polybutadiene, the cold flow may be large, which may pose a problem. There have been many proposals for improving the processability, including cold flow, of these diene rubbers, including the use of trans diene polymers. For example, ring-opened polymers of cyclooctene with many trans structures are called transpolyoctenamers, and are blended with ethylene-prepylene-diene ternary copolymer rubber, chloroprene rubber, acrylonitrile-butadiene copolymer rubber, etc. The effect of improving processability is known (Polymer no Tomo, August issue, 1983, pp. 507-513).
However, although this method does have the effect of improving processability, some physical properties, such as rubber elasticity, are degraded, and the price of the polymer is low, perhaps because cyclooctene, the raw material for the polymer, is relatively expensive. It is expensive and has not yet been widely used industrially. In addition, trans polybutadiene obtained by polymerizing butadiene in a heterogeneous catalyst system is known as trans 4, and it is used to improve extrusion processability by blending it with styrene-butadiene copolymer rubber (industrial materials, Volume 10, No. 6, 19
~21 pages, published in 1962), or it was proposed to be blended with medium vinyl polybutadiene to prevent cold flow (U.S. patent).
No. 4310582). However, the transpolybutadiene obtained using heterogeneous catalysts at that time had a wide molecular weight distribution and sometimes contained a large amount of gel, and its physical properties were compared to balata (transpolyisoprene), a natural transpolymer. (See table above, Industrial Materials, Vol. 10, No. 6, p. 19), and although both blends have the effect of improving processability or cold flow as desired, , its physical properties,
In particular, the dynamic properties of the rubber, typified by its impact resilience, are significantly reduced, and it has not been used industrially. The present inventors focused on the excellent processability improvement effect of these trans-based diene polymers, which appears to result from crystallization at relatively low temperatures, and the co-vulcanization characteristics with other diene-based polymers. Furthermore, various studies were carried out with the aim of alleviating the deterioration in physical properties, which is a drawback of this technology. The inventors have discovered that the physical properties and processability of the rubber-based rubber can be highly balanced, and have arrived at the present invention. That is, the present invention, as shown in the claims, has trans bonds of 75 to 90% and vinyl bonds of 3 to 10%.
%, molecular weight distribution (w/n) of 1.2 to 5, Mooney viscosity of 50 or less, a rubber composition consisting of 3 to 20 parts by weight of trans polybutadiene and 97 to 80 parts by weight of diene rubber (excluding the above trans polybutadiene). It is something to do. The trans polybutadiene of the present invention has a binding mode of trans bonds of 75 to 90%, preferably 80 to 88%.
%, and the vinyl bond is 3 to 10%, preferably 4 to 9
%. If the transformer bond is lower than this range, the effect of improving processability will be insufficient, while if it is higher than this range, a decrease in physical properties such as rubber elasticity will be observed. The binding mode of the present invention is determined by Morello's method using an infrared spectrometer. In addition, the molecular weight distribution measured by gel permeation chromatography (GPC) is expressed as a ratio (w/n) of weight average molecular weight (w) to number average molecular weight (n), and is preferably 1.2 to 5.
It needs to be 1.5 to 3.0, more preferably 1.8 to 2.5. Polymers with a molecular weight distribution exceeding this range result in significant deterioration of physical properties and do not exhibit the effects of the present invention. Furthermore, the Mooney viscosity measured at 100° C. using an L rotor must be 50 or less, preferably 20 or less, and more preferably 10 or less. If the Mooney viscosity is higher than this, the processability improvement effect of the present invention will not be achieved. The transpolybutadiene specified above contains a small amount of copolymer component in its molecular chain, for example 30% by weight.
It may contain the following monomer units such as styrene and isoprene in random or block form. Trans-polybutadiene having such a specified structure can be obtained by polymerizing butadiene in the presence of a homogeneous composite catalyst consisting of a barium, strontium or calcium compound, an organolithium compound or/and an organomagnesium compound (and optionally an organoaluminum compound). The bonding mode, molecular weight distribution, Mooney viscosity, etc. are variable depending on the polymerization conditions such as the amount of catalyst, composition, and polymerization temperature (for example, Japanese Patent Application Laid-Open No. 38827/1983). (See No. 56-112916). The composition of the transpolybutadiene of the present invention in the rubber composition of the present invention needs to be 3 to 20 parts by weight, preferably 5 to 18 to 20 parts by weight. If the ratio is less than this, the effect of improving processability cannot be sufficiently exhibited, while if it is added more than this, the properties of the diene rubber to be improved will be significantly reduced. The diene rubbers to be improved which constitute the remainder of the rubber composition of the present invention include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, and ethylene-based rubber.
Examples include propylene-diene ternary copolymer rubber, and those with particularly favorable effects include polybutadiene rubber (low-cis and high-cis), solution-polymerized styrene-butadiene copolymer rubber, and acrylonitrile-butadiene copolymer rubber (particularly medium-high nitrile and high- nitrile) and chloroprene rubber. Various types and brands of these diene rubbers are commercially available depending on the application, but as mentioned above, the effect of the present invention is generally achieved when the polymer chain structure is relatively high molecular weight and linear. A type that has excellent physical properties but poor processability.
It is greatly reflected in the brand. The rubber composition of the present invention can be used alone or together with other components, such as various compounding agents, fillers, vulcanizing agents, etc., to produce known rubber compositions. It can be easily obtained by mixing in various ways. The most common of these methods are mechanical kneading methods such as Banbury and roll kneading. The composition of the present invention can also be obtained by so-called solution blending, in which each component is in the form of a solution. This method is particularly useful when the diene rubber to be improved is a rubber obtained by solution polymerization. The rubber composition of the present invention can be used alone as an impact modifier by blending or grafting with various plastics, but in general, various compounded chemicals, reinforcing agents, and fillers widely used in diene rubbers are used. The mixture is mixed with additives or other auxiliary materials, and used as a vulcanized rubber using a known vulcanization method. Examples of these compounding agents include the following. Vulcanizing agent, vulcanization accelerator,
Antiaging agents, mastication accelerators, softeners, plasticizers, tackifiers, process oils, carbon black, inorganic reinforcing agents, organic reinforcing agents, inorganic fillers, various fiber materials,
Processing aids, finishing agents, rubber solvents, etc. As mentioned above, the composition of the present invention can be used as a vulcanized rubber in a wide range of applications, particularly by taking advantage of its excellent physical properties and processability. Tire applications such as tire treads, carcass, and sidewalls, belts, hoses, rolls, anti-vibration rubber, ebonite, linings, sponges, adhesives, footwear, rubberized fabrics, cut sheet products, various medical rubbers, electric wires, various balls, and Various separated products, extruded products, etc. Examples of the present invention are shown below to explain the present invention in more detail. Examples 1 to 6, Comparative Examples 1 to 6 and 16 The experimental results when the rubber composition of the present invention is composed of trans polybutadiene and polybutadiene rubber are shown in Tables 1 and 16 as Examples 1 to 6, Comparative Examples 1 to 6 and 16. Shown in 2. The transpolybutadiene used here was produced by polymerization using a homogeneous composite catalyst consisting of barium dinonyl phenoxide, butyllithium, dibutylmagnesium, and triethylaluminum. The compositions used were mechanical blends kneaded with rolls, except for Example 4, which was solution blended using a 20 weight percent solution of n-hexane. As is clear from Tables 1 and 2, it can be seen that the composition of the present invention has significantly improved cold flow properties and processability. Further, the physical properties of the vulcanizate are almost the same as those of the diene rubber alone before improvement, and may be superior in some cases. In other words, it is shown that a high balance between processability and physical properties is obtained in the diene rubber. Moreover, when comparing comparative examples as well, it can be seen that the above-mentioned effects of the present invention are only realized when the structure of trans-polybutadiene and its composition ratio are within the range of the present invention.

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[Table] Table 3 Formula (1) Rubber composition 100 parts by weight HAF grade carbon black 45 Aroma oil 5 Zinc white 5 Stearic acid 2 Sulfur 1.7 Accelerator CBS ^* 1.0 Total 159.7 *N- Cyclohexyl-2-benzothiazolesulfenamide Examples 7-9, Comparative Examples 7-9 and 17 The experimental results when the diene rubber is medium vinyl polybutadiene rubber are shown as Examples 7-9 and Comparative Examples 7-9 and 17. It is shown in Tables 4 and 5. The medium vinyl polybutadiene used here was prepared by polymerization using a catalyst consisting of butyllithium and tetrahydrofuran, and its structural analysis values were a Mooney viscosity of 53, a vinyl bond of 54%, and a molecular weight distribution (w/n) of 2.0. All compositions were also made by solution blending with 20 weight percent solutions of cyclohexane. As is clear from Tables 4 and 5, the effects of the present invention are also exhibited when the diene rubber is medium vinyl polybutadiene rubber. Furthermore, from the comparison between the examples and comparative examples, it is clear that if only the cold flow is improved, there is no need to limit the structure of trans-polybutadiene to the scope of the present invention, but it is necessary to improve the processability and avoid deterioration of the physical properties. It can be seen that the structure limitation of the present invention is essential.

[Table] = Same as Table 1 footnote.
*3

Claims (1)

[Claims] 1 Trans bond 75-90%, vinyl bond 3-10
%, molecular weight distribution (w/n) of 1.2 to 5, and a Mooney viscosity of 50 or less, a rubber composition comprising 3 to 20 parts by weight of trans polybutadiene and 97 to 80 parts by weight of a diene rubber (excluding the above trans polybutadiene).