JP2802669B2 - Rubber composition with improved tackiness when unvulcanized - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a rubber composition which reduces the temperature dependence of tack and has good early stability of tack.

[Prior art] The rubber composition for covering reinforcing cords such as pneumatic tires for automobiles and conveyor belts has a temperature dependence on tack when unvulcanized. The tackiness varies. In particular, in the case of a rubber composition containing an organic acid cobalt salt such as cobalt naphthenate, cobalt rosinate, cobalt stearate, cobalt neodecanoate, cobalt octylate, and cobalt propionate to improve the adhesion of the rubber to the steel cord. Was easy to overtack in summer when the ambient temperature was high. For this reason, the rubber sheet in which the reinforcing cord is embedded in the rubber composition has a remarkable tackiness on the surface, and tires have a problem in that workability in manufacturing rubber products such as a conveyor belt is deteriorated and productivity is reduced. there were.

The tackiness of such a rubber composition is generally reduced by blending paraffin wax (hereinafter abbreviated as wax). For example, for summer, in the wax analysis chart by the gas chromatography,
Ratio (%) of the count area of each number of carbon atoms (hereinafter abbreviated as C number) to the total count area of a certain number of carbon atoms
A wax having the maximum peak of the C number-C area distribution in which (hereinafter, referred to as C area) is plotted against the C number is around C number 34 is used. On the other hand, for winter, a wax having the maximum peak of C number-C area distribution near C number 27 is used. Thus, depending on the ambient temperature, C
By mixing waxes having different C numbers showing the maximum peak of the number-C area distribution, the tackiness of the rubber composition can be improved. However, although the rubber composition containing these waxes has good tackiness in a limited period of summer or winter, respectively,
Unless the ambient temperature is kept constant, there is a problem that good tackiness cannot be obtained, or the bloom bloom speed fluctuates and the early stability of tack is impaired.

[Problems to be solved by the invention]

An object of the present invention is to provide a rubber composition which improves the early stability of the tack while reducing the temperature dependence of the tack, and particularly provides a rubber composition containing an organic acid cobalt salt having excellent adhesion to a steel cord. That is.

[Means for solving the problem]

An object of the present invention is to provide a gas chromatograph containing at least 50% by weight of n-paraffin per 100 parts by weight of at least one rubber component selected from natural rubber, diene rubber and non-diene rubber. In a wax analysis chart by chromatography, the number of carbon atoms (hereinafter referred to as C _max) showing the maximum count number in the range of 24 to 44 carbon atoms.
Paraffin wax having a value of 4.0 or less obtained by dividing the chart area of the chart number of the carbon atoms (hereinafter abbreviated as C _min ) indicating the minimum count number by 0.001 to 1.5. This can be achieved by a rubber composition mixed with parts by weight.

The wax used in the rubber composition of the present invention must contain at least 50% by weight, preferably 75% by weight or more of n-paraffin. If the content of the n-paraffin is less than 50% by weight, the bloom speed of the wax decreases, and a rubber composition having good early tack stability can not be obtained.

The above wax has a C number of ₂₃ to ₄₂ (hereinafter, C _{23 to} C _42).
A display), preferably, has a distribution C area ratio in the range of C ₂₅ -C ₄₀ is 4.0 or less, i.e., uniform C number -C area distribution in the range of the C ₂₃ -C ₄₂ It is necessary to have the wax.

As shown in FIG. 1, such a wax has the horizontal axis representing the C number of paraffin molecules constituting the wax,
In C number -C area distribution diagram represented taking the area on the vertical axis, if the C area ratio in the range of C ₂₃ -C ₄₂ is 4.0 or less, the line a, b, c, the distribution indicated by d Can be taken.

By blending a wax having a uniform C number-C area distribution within the range of the specific C number, the temperature dependency of the tack of the rubber composition of the present invention is reduced, and the time of use and the ambient temperature are reduced. Regardless, good tackiness can be obtained.

The compounding amount of the wax in the rubber composition of the present invention is 1.5 parts by weight or less, preferably 1 part by weight or less per 100 parts by weight of the rubber component. Even if the amount exceeds 1.5 parts by weight, there is almost no difference in the temperature dependency and early stability of the tack, and rather the physical properties of the rubber composition may be impaired.

The compounding of the wax is particularly effective for a rubber composition containing a cobalt salt of an organic acid in order to improve the adhesion to a steel cord.

As the rubber component of the rubber composition of the present invention, natural rubber,
There are diene rubbers such as synthetic polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber and butyl rubber, and non-diene rubbers such as ethylene-propylene-diene terpolymer rubber (EPDM). These rubber components can be used alone or in combination of two or more.

Further, the rubber composition of the present invention includes a reinforcing agent such as carbon black, sulfur, a vulcanization accelerator, a vulcanization aid, an antioxidant,
A softening agent and the like are appropriately blended, but the blending composition and blending amount are not particularly limited.

〔Example〕

Six wax having different C area ratio and n- paraffins content in the range of C ₂₃ -C _42, it was formulated respectively, to prepare a rubber composition compounding composition shown in Table.

For each of these six types of rubber compositions, using a tack tester Pikumatak II manufactured by Toyo Seiki Co., Ltd.,
The following tack test was performed.

Tack test: A rubber sheet with a thickness of 1 mm made from a rubber composition is pressed on a specified backing cloth at 100 ° C for 5 minutes, then cut into a 5 mm wide strip and a 50 x 50 mm sheet and used as a sample. I do. The strip-shaped sample is wound around a pressure ring of a tack tester, and is pressed onto a sheet-shaped sample. Next, the sheet-like sample is peeled, and the peeling force (g) at that time is measured. The smaller the peeling force, the smaller the tackiness.

The measurement conditions were as follows: the ambient temperature was 0 ° C, 10 ° C, 20 ° C.
The sample was left at these ambient temperatures under five conditions of ° C, 30 ° C, and 40 ° C, and the peel force over time was measured. Crimping conditions for measurement were as follows: crimping speed 500 mm / min, peeling speed 12
The pressure was 50 mm / min, the pressure load was 500 g, and the pressure time was 0 second.

From the peeling force measurement results, the following reduced peak temperature, half-value time and R were calculated. The results are shown in the table and FIG.

Decreased peak temperature: The temperature at which the lowest peel force is exhibited in the tack test. This temperature has a range, and the wider the range, the smaller the temperature dependence of the tack.

R: Difference between the maximum peeling force and the minimum peeling force in the tack test. The smaller the value of R, the smaller the temperature dependence of the tack.

Half-value time: In the tack test, the peeling force is measured while keeping the measurement temperature constant, and changing the interval after leaving. The peeling time is half the peeling force when the leaving time is 0. The smaller the value, the better the early stability of the tack.

As can be seen from the table, the lowered peak temperatures were lower than those of Comparative Examples 1 to 5.
Has no width, whereas the example has a width (30 to 40 ° C.), R has the smallest value in the example, and the temperature dependence of tack is the smallest.

The half value time of Comparative Example 4 having a large amount of n-paraffin is the smallest, and has good early stability of tack. The comparative example 2 having a small amount of n-paraffin is the largest, and the early stability of tack is poor. There is almost no difference between the working line and Comparative Examples 1, 3, and 5,
It has the same early stability of tack.

Further, FIG. 2 shows that, in comparison with Comparative Examples 1 to 5, the value of tack (peeling force g) with respect to temperature is low, the variation is small, and the temperature dependence of tack is small.

[Effects of the Invention] According to the present invention, the n-paraffin content is at least 50% by weight based on at least one rubber component selected from natural rubber, diene rubber and non-diene rubber, and C ₂₃ since C area ratio in the range of -C ₄₂ 4.0 specified amount of paraffin wax having a C number -C area distribution is less than a small temperature dependence of tack, good rubber early stability of tack Things are obtained. In particular, the temperature dependence of tack of a rubber composition containing a cobalt salt of an organic acid having excellent adhesion to a steel cord can be effectively reduced.

[Brief description of the drawings]

FIG. 1 shows the C number of the paraffin wax specified in the present invention.
FIG. 2 is a diagram showing the C area distribution, and FIG. 2 is a diagram showing the relationship between the temperature of the rubber composition and the peeling force (tack).

Claims (1)

(57) [Claims] 1. A rubber composition comprising at least 50% by weight of n-paraffin per 100 parts by weight of at least one rubber component selected from natural rubber, diene rubber and non-diene rubber,
And in the wax analysis chart by gas chromatography, the value obtained by dividing the chart area of the number of carbon atoms indicating the maximum count in the range of 23 to 42 carbon atoms by the chart area of the number of carbon atoms indicating the minimum count is A rubber composition containing 0.001 to 1.5 parts by weight of paraffin wax having a viscosity of 4.0 or less and having improved tackiness when not vulcanized.