JPS58469B2 - Novel polybutadiene rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention contains a polymer in which syndiotactic (syn)-1,2-polybutadiene is block-polymerized or graft-polymerized to cis-1,4-polybutadiene,
The 5yn-1/2. - The single polybutadiene rubber region in which polybutadiene is crystallized into short fibers is a polybutadiene rubber composition whose main component is polyisoprene rubber blended with other diene rubbers, and the polybutadiene rubber composition is composed of polyisoprene rubber blended with other diene rubber. The present invention relates to a polybutadiene rubber composition containing polybutadiene rubber as a main component, which has significantly improved fracture resistance and reinforcing properties by specifying the diameter and length.

Since cis-1.4-polybutadiene has excellent flexibility and abrasion resistance, it has been widely used for components such as tire sidewalls, rubber chafers (or rim cushions), and treads.

However, this material has poor workability, such as causing roll baggage and having low strength after vulcanization.
Since it has drawbacks such as a high crack growth rate, it is used by blending it with other diene rubbers such as natural rubber, but it is still not sufficient and cis-1,4-polybutadiene must be used in a high proportion. was difficult.

In order to solve the above-mentioned drawbacks, the inventors of the present invention filed a patent application filed in
As described in No. 144021 and Japanese Patent Application No. 52-144022, 5y
Attempts have been made to improve n-1,2-polybutadiene by block polymerization or graft polymerization, but even if it were synthesized in the same way, the physical properties varied greatly, and the demand for lightweight tires and other products has increased rapidly recently. It is still not enough to be applied to low fuel consumption tires.

As a result of further intensive research by the present inventors to solve the above-mentioned drawbacks, we found that 5yn-1,2-polybutadiene, which undergoes block polymerization or raft polymerization to cis-1,4-polybutadiene, crystallizes and forms short fibers. It has been found that by noting that and specifying the diameter and length of the short fibers, not only the fluctuations in physical properties are small but also the physical properties are dramatically improved.

The gist of the present invention is to contain a polymer in which syndiotactic (Syn)-1,2-polybutadiene is block-polymerized or graft-polymerized to cis-1,4-polybutadiene, and the entire microstructure is cis. -1.4-structure is 78 to 93% by weight.

A polybutadiene rubber having 6 to 20% by weight of 5yn-1.2-structure, wherein at least 40% by weight of the 5yn-1.2-polybutadiene is crystallized and has an average diameter of 0.0.
A polybutadiene rubber composition whose main component is polybutadiene rubber alone or blended with other diene rubber, which is in the form of short fibers with an average length of 0.8 to 10μ and an average length of 0.8 to 10μ. Various inorganic fillers are usually added to such compositions depending on the purpose.

The polybutadiene rubber of the present invention is basically manufactured by Tokuko.

It is manufactured by the method disclosed in Japanese Patent No. 49-17666 and No. 49-17667.

However, even if the rubbers are synthesized in the same manner using such a method, it is difficult to consistently obtain rubbers with the same performance.

This is because 5yn-1,2-polybutadiene polymerizes and crystallizes to form short fibers.
The present invention shows that the shape of the 2-polybutadiene short fibers has a large effect on the performance of the obtained rubber, and that changes in the shape of the short fibers are greatly influenced by the stirring conditions (shear rate distribution, shear rate) during polymerization. This was revealed through research by researchers.

Specifically, if the shear rate distribution is disturbed and the agitation is performed in a state close to turbulent flow, the ratio of average length/average diameter of the short fibers will be small; The diameter ratio increases.

Furthermore, stirring at a high shear rate will decrease the short fiber diameter, and conversely, stirring at a low shear rate will increase the short fiber length.

Therefore, by discovering such a phenomenon, it has become possible to freely and easily change the shape of 5yn-1,2-polybutadiene short fibers over a wide range.

The microstructure of the polybutadiene rubber of the present invention is dissolved in n-hexane and separated into soluble and insoluble components using a centrifuge. The microstructure of the insoluble matter is determined by infrared absorption spectroscopy after dissolving in carbon disulfide, and the microstructure of the insoluble matter is determined by infrared absorption spectroscopy of potassium bromide after drying by the tablet method, and is calculated from the values of both.

The polybutadiene rubber in the present invention is particularly 5yn-1
- The content of 2- structure is important and is 6 to 20% by weight.

If it is less than 6% by weight, the physical properties are almost the same as those of conventional cis-1,4-polybutadiene rubber, and if it is more than 20% by weight, the viscosity is too high and has a significant adverse effect on workability.

However, even in such a case, it is possible to use it satisfactorily by adding cis-1,4-polybutadiene rubber and adjusting the content of the 5yn-1,2-structure to 20% by weight or less as a whole. It is.

In the polybutadiene rubber of the present invention, 5yn-1.
The average diameter and average length of the short fibers of 2-polybutadiene are measured by the method described below, and the average diameter is 0.05 to 1μ and the average length is 0.8 to 10μ.

If the average diameter is less than 0.05 μm, the fracture resistance of the polybutadiene rubber decreases, and if the average diameter is less than 1 μm, the bending resistance of the polybutadiene rubber decreases, which is not preferable.

Furthermore, if the average length is less than 0.8 μm, the polybutadiene rubber will have poor crack growth resistance, and if it is more than 10 μm, the workability will be significantly reduced, which is not preferable.

Further, the average length/average diameter ratio is preferably at least 8, and when it is 8 or more, the fracture resistance of the polybutadiene rubber is further improved.

In the polybutadiene rubber of the present invention, at least 4
It is necessary that 0% by weight of 5yn-1.2-polybutadiene be crystallized.

If it is less than 40% by weight, the melting point of the short fibers decreases and the temperature dependence becomes large, which is not preferable because the temperature dependence of the polybutadiene rubber also increases as a result.

Therefore, the higher the tacticity of 5yn-1.2-polybutadiene, the better it is.

In the polybutadiene composition of the present invention, the other diene rubbers include natural rubber, polyimprene rubber, styrene-butadiene copolymer comb, cis-1.4-polybutadiene rubber, or a blend rubber thereof.

In the polybutadiene rubber composition of the present invention, the vulcanizing agents include sulfur, alkylphenol disulfide and 4.
It is 4'-dithiodimorpholine, preferably sulfur, and its amount is within the range used in ordinary rubber compounding.

In the polybutadiene rubber composition of the present invention, the inorganic fillers include silicic anhydride, calcium carbonate, magnesium carbonate,
Talc, iron sulfide, iron oxide, bentonite, zinc white, diatomaceous earth, clay, clay, alumina, titanium oxide, and carbon black, the amount of which is considered from the viewpoint of reinforcing properties and workability per 100 parts by weight of polybutadiene rubber. Te 20-120
Parts by weight are appropriate.

In order to use the polybutadiene rubber composition of the present invention as a tire tread rubber, it is necessary that the weight average molecular weight of cis-1,4-polybutadiene be 350,000 or more.

This is because if it is less than 350,000, the wear resistance necessary for a tread will not be sufficient.

Furthermore, as carbon black, the iodine adsorption amount (IA) is 60 ■/g or more, and the dibutyl phthalate oil absorption amount (DBP)
Use carbon black with a content of 70 mg/100 g or more.

If IA is less than 60 mg/g, the specific surface area of carbon black is small, sufficient wear resistance cannot be obtained, and DBP is 70.
If it is less than m1/100g, a sufficient reinforcing effect cannot be obtained, and both are unfavorable.

In addition, considering the addition effect, workability, and fatigue resistance, the blending amount is 30 to 30 parts by weight per 100 parts by weight of polybutadiene rubber.
100 parts by weight is suitable.

The polybutadiene rubber composition of the present invention has extremely excellent bending resistance, crack growth resistance, and fracture resistance, so it can be applied to almost all parts other than the above-mentioned tire tread, such as sidewalls. It can be applied to coating rubber, rubber chafer, bead filler, belt end coating rubber, buffer rubber between reinforcing layers, or inner liner, which not only greatly improves the overall performance of tires but also meets the recent demands. It can also be said to be a new material indispensable for the development of various functional tires, including fuel-efficient tires with reduced tire weight.

The present invention will be explained in more detail below with reference to Examples and Comparative Examples.
Three types of polybutadiene rubber with different microstructures.

Regarding the average diameter and average length of short fibers, samples were prepared by extruding various polybutadiene rubbers through a circular goo with a diameter of 2 mm and a length of 10 mm, and the rubber content of this sample was dissolved in n-hexane for 48 hours. After that, it was freeze-dried and stained with osmium oxide (C3O4).

This was embedded in methyl methacrylate (MMA), an ultrathin section was cut perpendicular to the extrusion direction, and the diameter was measured using an electron microscope.

Also, cut out an ultra-thin section parallel to the extrusion direction,
The length was measured in the same manner.

The average diameter and average length were determined by the following formula.

However, r: Average diameter of short fibers ri: Diameter of short fibers 1: Average length of short fibers 1i: Length of short fibers ni: Number of short fibers having a diameter of ri or a length of li Σni
:300 The 13 types of polybutadiene rubbers shown in Table 1 with different microstructures were manufactured as follows.

Toluene 16k was dehydrated and purified after purging with nitrogen gas in a stainless steel cylindrical reaction tank with an internal capacity of 301 cm and equipped with a stirrer.
A solution in which 1.0 kg of 1,3-butadiene was dissolved was added to g, and 3.8 mmol of cobalt octoate and 80 mmol of diethylaluminolide were added.

70 mmol of 1,5-cyclooctadiene (COD) was mixed and stirred at 25°C for 40 minutes to obtain a high cis 1,4 bond polymerized rubber.

The intrinsic viscosity η of the polymer was 2.3.

After cooling this as it was to -5°C, 95 mmol of triethylaluminum and 370 mmol of acetonitrile were added.
Then, 0.5 kg of 1,3-butadiene and 45 mmol of carbon disulfide were added, and the temperature was gradually raised while stirring sufficiently to carry out block-craft polymerization of 5yn-1,2-polybutadiene.

In this 5yn-1.2-polybutadiene polymerization, 13 types of polybutadiene rubbers were obtained by varying the stirring conditions, stirring speed, polymerization time, and final polymerization temperature.

The stirring condition was adjusted using three types of stirrers: a propeller type stirrer, a turbine type stirrer, and a paddle type stirrer.

Table 1 Sample A, 10 has a propeller type, Sample A
A turbine type stirrer was used for Sample No. 1.2.3.4.7.8.9.12, and a paddle type stirrer was used for Sample No. 2.6.11°13.

An outline of the shape of the stirrer is shown, for example, in Figure 168 of Mechanical Engineering Handbook (published by the Japan Society of Mechanical Engineers) 18-50.

The stirring speed, polymerization time, and final polymerization temperature were as shown in Table 1.

Examples 1 to 6 and Comparative Examples 1 to 7 Samples 1 to 13 shown in Table 1 and various polybutadiene rubber compositions compounded according to Table 2 using Ubepol 150 as a conventional example, had Mooney viscosity ( M.L.
1+4), Mooney scorch time (MST), polymer dispersity, roll workability and 150°C, 80kg/cm
Vulcanize for 30 minutes under the conditions of 4, hardness (Hd), breaking strength (
Tb), elongation at break (Eb), 300% modulus (30
0Md), crack growth resistance, and bending resistance were measured.

The results are shown in Table 2.

Regarding the test method, ML1+4 and MST are JIS
The method described in K6300 was followed.

The degree of polymer dispersion was observed using an electron microscope at a magnification of X5000 after mixing each compounding agent (OsO4 staining).

Roll workability was evaluated using a 10-inch roll with or without a roll bag.

JIS for Hd, Tb, Eb and 300Md
Measured according to K6301.

Crack growth resistance was measured using a Dematcher tester (300 cycles/min) and expressed as an index, with the conventional example being 100 and the time taken for an initial cut of 2 mm to grow to 12 mm.

Therefore, the larger the value, the better the crack growth resistance.

The bending resistance was measured using a Demacher tester, and the time until cracking was similarly expressed as an index, with the conventional example set as 100.

Therefore, the larger the value, the better the bending resistance.

What is clear from Tables 1 and 2 is that (1) Example 1
3 and Comparative Examples 1 and 2, the polybutadiene rubber composition of the present invention having a content of 5yrI-1/2 structure of 6 to 20% by weight shows good results; (2) Examples 4～
5 and Comparative Examples 3 to 4, the average diameter of the short fibers formed by 5yn-1,2-polybutadiene is in the range of 0.05 to 1μ, and (3) Examples 2.5 to 4. 6
And from Comparative Examples 5 to 7, the average length of the short fibers formed by 5yn-1,2-polybutadiene is 0.8 to 10μ, and the average length /
Good results are shown when the average diameter ratio is in the range of 8 or more.

Examples 7 to 9 and Comparative Example 8 Samples 14 to 17 shown in Table 3 and various polybutadiene rubber compositions compounded according to Table 4 using Ubepol 150 as a conventional example were compared with Example 1 described above. Similarly, crack growth resistance and bending resistance, as well as fracture resistance and abrasion resistance, were investigated.

In addition, cis-1,4-polybutadiene (
The weight average molecular weight of cis-1/4-polybutadiene rubber is determined by dissolving various polybutadiene rubbers in n-hexane and separating them into soluble and insoluble components using a centrifuge. ) was determined by light scattering method.

In addition, the fracture resistance properties were tested using a single swing type tester.
) was dropped onto a rubber sample (15 cm x 10 cm x 5.5 cm) by its own weight from a certain height, and the depth of the scratches on the rubber sample was determined from the conventional example by 10.
It was expressed as an index with 0 as the value.

Therefore, the larger the value, the better the fracture resistance.

Wear resistance was evaluated by pico wear specified by ASTM D2228, and expressed as an index with the conventional example set as 100.

The larger the value, the better the wear resistance.

Table 4 shows that the polybutadiene rubber composition of the present invention, in which the weight average molecular weight of cis-1,4-polybutadiene is 350,000 or more, has excellent abrasion resistance and can be suitably used for tire tread rubber. is clear.

Claims (1)

[Claims] 1 Contains a polymer obtained by block polymerizing or graft polymerizing syndiotactic (syn)-1,2-polybutadiene to cis-1,4-polybutadiene, and has a total microstructure of cis-1・78-93% by weight of 4-structure
, 5yr1-1.2-structure is 6 to 20% by weight, wherein at least 40% by weight of the 5yr1-1.2-polybutadiene is crystallized and the average diameter is 0.
．． Rubber whose main component is polybutadiene rubber alone or blended with other diene rubbers of polybutadiene rubber, which is in the form of short fibers with an average length of 0.05 to 1μ and an average length of 0.8 to 10μ. A polybutadiene rubber composition characterized by blending an inorganic filler with. 2 Inorganic fillers include anhydrous silicic acid, calcium carbonate, magnesium carbonate, talc, iron sulfide, iron oxide, bentonite, zinc white, diatomaceous earth, clay, clay, alumina, titanium oxide,
The polybutadiene rubber composition according to claim 1, which is carbon black. 3 Carbon black has an iodine adsorption amount (IA) of 60m
g/g or more, dibutyl phthalate oil absorption (DBP) is 7
The polybutadiene rubber composition according to claim 2, characterized in that the polybutadiene rubber composition is carbon black having a carbon black of 0 m1/100 g or more. 4. The polybutadiene rubber composition according to claim 3, wherein the weight average molecular weight of the cis-1.4-polybutadiene is 350,000 or more. 5 Other diene rubbers include natural rubber, polyisoprene rubber, styrene-butadiene copolymer comb, cis-1/4
- The polybutadiene rubber composition according to any one of claims 1 to 4, which is polybutadiene rubber or a blend rubber thereof. 6. The polybutadiene rubber composition according to claim 1, wherein the average length/average diameter ratio of the 6syn-1.2-polybutadiene short fibers is at least 8.