JPS62201949A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. which gives rubber goods having excel lent dynamic properties, adhesion to fibers and metal and processing char acteristics and gives an vulcanized rubber having excellent characteristics, by blending a rubber with resorcinol (derivative) and a specified melamine derivative. CONSTITUTION:100pts.wt. natural or synthetic rubber (A) (e.g., isoprene rubber) is blended with 0.1-7pts.wt. resorcinol (derivative) (B) (e.g., a resorcinol/ formaldehyde resin), 0.5-7pts.wt. melamine derivative (C) having a bonded formalin unit and a bonded methoxy group unit per melamine molecule in such a rate that 4 <= the number of bonded formalin units <= 6; 2 <= the number of bonded methoxy groups < 6 provided that when the component A contains silica, 4 <= the number of methoxy groups < 6 and the content of monomer is 60-90%, and optionally a vulcanizing agent, a vulcanization aid, a vulcanization retarder, a reinforcing agent, a colorant, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rubber composition suitable for obtaining rubber products such as tires and conveyor belts that are subjected to mechanical fatigue and thermal deterioration.

(Prior Art) A technique for blending a melamine compound into a rubber composition has been known, for example, as disclosed in Japanese Patent Publication No. 40-16421.

45-27463. 46-10295,
47-7640, etc. However, the purpose of these methods is to improve the adhesion between rubber and fibers or metals, and no attention has been paid to the fatigue resistance or heat deterioration resistance of the rubber products obtained therefrom.

In general, automatic tires and the like that are used under conditions of repeated mechanical deformation are strongly required to have dynamic properties, particularly fatigue resistance and heat deterioration resistance due to self-heating of rubber.

In particular, the belt and ply parts of white tires, which are used in the form of a composite of rubber and materials with widely different rigidities such as fibers and metals, suffer from large rigidity differences as well as deterioration of the adhesion between the i-fibers and metal and rubber. Therefore, the interfacial rubber part undergoes large deformation, and second, fatigue progresses locally.

In particular, the recent market environment has become such that the quality of products such as automatic LP tires has improved, and the market environment has become such that only the treads are renewed and reused after the initial or complete completion of cleaning or cleaning due to improved product quality and improved road conditions. The development of rubber compositions with excellent fatigue resistance under heat is absolutely necessary to improve the lifespan of products.

Deterioration of rubber properties due to mechanical repetition of rubber products is controlled by the magnitude of deformation and heat generation/heat resistance.

In other words, the dynamic elastic modulus E', which correlates with the magnitude of dynamic deformation, and the dynamic elastic modulus E', which correlates with dynamic self-heating property, t, an
It is governed by a dynamic characteristic called δ.

Polymers, carbon black,
There are white fillers, softeners, resins, vulcanization aids, vulcanization accelerators, vulcanizing agents, etc. Therefore, by changing the types and amounts of these compounding agents, we can improve the fatigue resistance and heat deterioration resistance of the rubber composition. In other words, we can improve the fatigue resistance and heat deterioration resistance of the rubber composition. In other words, we can improve the fatigue resistance and heat deterioration resistance of the rubber composition. I carefully considered it, but
There are few compounding factors that can improve both of these two properties, which are generally contradictory, and there are also factors that relatively meet this objective, such as increasing the amount of vulcanization accelerator, to improve the adhesion of fibers and metals. turned out to be bad and serve no ultimate purpose.

As a result of intensive studies to improve the dynamic properties of rubber products, we found that the amount of bound formalin in a certain range per molecule of resorcin or resorcin derivative and melamine,
By blending a melamine derivative having a methoxy group and a certain monomer content into natural rubber or synthetic rubber, the adhesion with reinforcing materials and the processability of unvulcanized rubber compounds may be impaired. The dynamic properties of vulcanized rubber are 11
They found that the eyes can be improved and completed the present invention.

(Problems to be Solved by the Invention) An object of the present invention is to provide a rubber composition suitable for obtaining a rubber product with excellent dynamic properties.

Another object of the present invention is to provide a rubber composition suitable for obtaining rubber products that are excellent in adhesion between rubber and fibers or metals, other vulcanized rubber properties, and processing properties.

(Means for solving the problem α) The present invention applies resorcin or a resorcin derivative to natural rubber or synthetic rubber, and the number of bonded formalin and methoxy group per molecule of melamine is 4≦(number of bonded formalin)≦ 6. Dynamic 1, ? is characterized by blending a melamine derivative in the range of 2≦(methoxy group number) x 6 and with a monomer content of 60 to 9096. The present invention relates to a rubber composition with improved properties.

In general, there are two types of compounding systems for automobile tire belts and ply parts: those that contain silica and those that do not.In systems that contain silica, the adhesion between rubber and reinforcing materials such as metals and fibers is poor. Although advantageous, the processability of unvulcanized rubber compounds tends to be rather disadvantageous.

The present invention can be used for El in both systems containing silica and systems not containing silica; however, for systems containing silica;
The number of bound formalin and the number of methoxy groups are 4≦(number of bound formalin)≦6. It is particularly preferable that 4≦(methoxy group number)<6.

In the melamine derivative of the present invention, the higher the U-wood content, the better the vulcanized rubber exhibits excellent dynamic properties, and the moreover, the unvulcanized rubber compound exhibits higher sulfur stability. In other words, when the 114 is less than 60%, even if the number of bound formalin and methoxy groups per melamine molecule is within the range of the present invention, excellent dynamic properties and high group coach stability are obtained. cannot be obtained. = If the iM content exceeds 90%, it cannot be obtained by normal manufacturing methods and requires a special purification process, which increases the manufacturing cost and reduces the commercial value. Upper-13j body content is 60~
A range of 90% is selected.

Furthermore, the greater the number of formalin bound per molecule of melamine, the better the dynamic properties of the vulcanized rubber tend to be, and if the number of formalin bound per molecule is less than 4, sufficient effects cannot be obtained.

The ratio of methoxy groups to free methylol groups in the melamine derivative also affects the dynamic properties of vulcanized rubber and the processability of unvulcanized rubber.

In other words, even if the number of bonded formalin per melamine derivative fj1 and melamine molecule is constant, the fewer methoxy groups there are, the greater the 7Tyrol random number of 7 Li. However, there is a point where the processability of unvulcanized rubber deteriorates over time, and this tendency is noticeable in systems containing silica.

Therefore, it is practically preferable that the number of methoxy groups is 2 or more in a system that does not contain silica, and that the number of methoxy groups is 4 or more in a system that contains silica.

As described above, in the present invention, resorcin or a resorcin derivative is added to natural rubber or synthetic rubber, and the number of bound formalin and methoxy groups per molecule of melamine is within a certain range, and the -■ isomer content is within a specific range. Only when the dynamic properties of the target vulcanized rubber are excellent, and! Since it does not impair the adhesion of the 5-gatamine to fibers or metals or the scorch stability of unvulcanized rubber, its practical value is extremely high in the above-mentioned social situation.

In the present invention, resorcin or a resorcin derivative is usually blended in an amount of 0.1 to 7 parts, preferably 5 parts, per 100 parts (parts by weight, hereinafter the same) of rubber.

Examples of the resorcin derivative include resorcinol-formaldehyde resin, a molten mixture of resorcinol-formaldehyde resin and alkylphenol-formaldehyde resin, and the like.

The melamine derivative is usually 0.0% per 100 parts of rubber.
It is blended in an amount of 5 to 7 parts, preferably 1 to 5 parts.

In the present invention, the rubber component used is one or more of natural rubber (Nfl) and synthetic rubber. Examples of synthetic rubber include polyisoprene rubber (R), polybutanoene rubber ([3RL), styrene-butadiene rubber (SF3R), isoprene-isobutylene rubber (IIR),
L-ethylene-bu-pyrene-tene rubber (EPDM), modified products thereof, blends thereof, etc. can all be used.

The rubber composition of the present invention can be prepared by processing the above-mentioned components using conventional processing equipment u'i,
For example, by rolling, gunbarimigisa, nigu, etc.) H building 11). In addition to the above ingredients, known vulcanizing agents, vulcanization accelerators, vulcanization accelerators, vulcanization slow 5L shavings, manned peroxides, reinforcing agents, fillers, anti-aging agents, tackifiers, colorants. Of course, it is also possible to add the following.

(Example) Reference examples, examples, and comparative examples will be described below. Note that % or parts simply indicates weight % or parts by weight.

Reference Example 1 (Synthesis of melamine derivative) Formalin (37%) was added to 259.6F in a 3-7 rasf made of 11 plastics equipped with a stirrer, thermometer and reflux device.
! (3.20 mol) Prepared with caustic soda in the evening view 1) I
After adjusting to I9.0-9.5, melamine 50.5 bi(0,
40 mol) was charged, and the content was heated to a reflux state (approximately 80°C) and kept in an oil bath. After 60 minutes had passed since the start of reflux, the oil bath was removed, cooled to room temperature, and 202.6 g (6.33 mm) of methanol was added to fl:
It was crowded. Furthermore, sulfuric acid lowers 11 M to 2-3.
The methoxylation reaction was carried out at 0°C for 120 minutes. Water and methanol were distilled off from the synthesized reaction solution by vacuum distillation, and the solution was taken out in a heated state.

The content of the -i form of this melamine derivative is 81%, the number of formalin bound per molecule of melamine is 5.7, and the number of methoxy groups is 4.2.

For formalin, various melamine derivatives were produced in the same manner by changing the molar ratio of methanol, reaction temperature, etc.

In addition, the monomer content, the number of bound formalin, and the number of methoxy groups of the melamine derivative were measured by the following method.

(Measurement method) -HLfffi: Area percentage by GPC (5' permeation chromatography).

- Amount of bound formalin: After adding phosphoric acid, formalin was expelled by distillation, and the resulting amount of formalin was calculated by iodine-sodium thiosulfate titration.

- Number of methoxy groups: After adding hydroiodic acid to the melamine derivative 727-l and propionic acid solution, it was calculated by titration with sodium potassium iodide-thiosulfate.

(In the examples, the number of free methylol groups is shown for reference in order to clarify the structure of the melamine derivative, but the number of free methylol groups was also calculated by titration by the iodine-sodium thiosulfate method in the same way as the others. ) The characteristics of the vulcanized rubber obtained in the examples were measured by the following method.

Dynamic viscoelastic properties: Using a viscoelastic spectrometer manufactured by Script Seisakusho (7 initial M strain 15%, vibration 1111%, frequency 501 (z, room temperature 30'
Measured at C. dynamic elastic modulus E゛ and Rostanzen)
The value of tan δ was expressed as an index and displayed. The higher the index of E, the lower the index with jan, the better.

Mooney scorch property: The scorch time at 125°C was expressed as an index. I
The higher the ndex, the longer the scorch time and the more stable the processing process.

I-layer properties with steel cord; 7 x 4 The pull-out force after heat aging and wet heat adhesive strength were evaluated by the pull-out force after heat aging at 75° C. x 80 RII% x 48 hours. The higher the value, the better.

In addition, I(s represents hardness, Mloo represents 100 c!6 tensile stress, TB represents tensile strength, and CB represents elongation.

Example 1 80 parts of natural rubber (R8S1.), inbrene rubber (T
f12200) 20 parts, 13-IIAF carbon 60
Miyako, 7510 parts of zinc, cobalt naphthenate (Co content 10
96) 3 parts of antifoaming agent<6C), 1 part of resorcinol, 6 parts of sulfur, 1 part of vulcanization accelerator (DZ), and the melamine derivatives or other additives listed in Table 1 are blended into C. A rubber composition was obtained by kneading the mixture for 4 minutes using a Banbury mixer.

In addition, No. 10 did not contain resorcinol.

The obtained rubber composition was mold-vulcanized at 150° C. for 30 minutes, and its properties were measured. The results are shown in Table 1.

From Table 1, the rubber compositions No. 1-4 are! '? i I
'', Y, which is an index indicating fat an δ property:
' / 1. The an δ value is about 1.5 to 1.8 and No. 5
It is higher than about 1.2-1.3 of the rubber composition of ~7,
Shows the common effects of both T and Y. Furthermore, there is no significant difference in adhesion to steel cord between the two groups. No. 8 hexamethylenetetramine also has an E'/lan δ value of 1.5
Although it has excellent properties, its wet heat adhesion is about half that of melamine-based rubber compositions, which is significantly inferior. In the table, the number of bound formalin, the number of methoxy groups, and the number of free methylol groups are values per melamine molecule, and the same applies to the following tables.

Example 2 A rubber composition was obtained in the same manner as in Example 1 except for using the melamine derivatives listed in Table 2. The vulcanization properties of the obtained rubber composition are also shown in Table 2.

Table 2 ttFrom Table S2, as the number of methoxy groups increases from No. 1 to No. 5, the shooch time increases, but L a n δ
There is a tendency for E to become higher and E to become lower.

Example 3 80 parts of natural rubber (R3S#1), impregnated rubber (r
R2200) 20 parts, LS-HAF carbon 52 parts,
Silica 1off5, zinc 1J, 7 parts, cobalt naphthenate (Co content 10%) 2g, anti-aging agent (6CHn, resorcinol 1 part, sulfur W 4.2 parts, vulcanization accelerator (DZ) 0.7
The melamine derivatives listed in Table 3 or other additives were added to the mixture, and mixed in a Banbury mixer for 4 minutes to obtain a rubber composition. In addition, NO,6 is made by adding one part of resorcin/formalin condensate instead of resorcin.
No. 12 contained no resorcinol.

The vulcanization properties of the obtained rubber acid product were similarly shown below.

From Table 3, the former Iδ value of rubber composition 1 of No. 1-G is about 1.6-1.8 and 1.3 of the rubber composition of No. 7-No. 9. It is higher than that and shows excellent common effects. Furthermore, there is no significant difference in adhesion to steel cord between the two groups. No, 10 rubber compositions ri
+= ゛/lax+δ The power bow is high and excellent at 81, but the Shooch Time Index is extremely poor at 60.

The rubber composition of No. 11 also had an E'/lan δ value of 62.
However, the wet heat adhesive strength I +ulex is extremely poor at 58.

Example 4 (Tire) T-ram test) Steel belt topping rubber, steel belt edge rubber,
As the rubber inserted between the steel belt Esso, a rubber 1.
00 R2014P tires were manufactured and sold in the United States.
Based on the and RimA 5sociaLion criteria T read 1caviBcarcass (
After driving for a certain period of time under T L C) conditions, the tires are dismantled 2
The length of the separation from the third and third belt ends was measured at 20 points on the circumference, and the average length was expressed as an index. The smaller Iodc is, the shorter and better the separation is. The results are shown in Tables 4 and 5. ! 14m
Table 1 shows the drum test results of a tire using a belt rubber that does not contain silica, and Table I¥S5 shows the drum test results of a tire that uses a belt rubber that contains silica with exactly the same composition as in Example 3.

4th friend No. Example Comparative example Melamine sleeve of belt rubber - Foil content (%) 65218 83 37
Unbonded formalin number, '+, 8 5, 9 5,
9 5.5 Number of added methoxy groups 4. G5
．． G 2,9 3.7 Addition (free methylol group) 0,2 0,1 2,3 0.2 Belt end separation 6'a 6G 61 86100 (
Tires using the rubber compositions No. 1-3 in Table 54 and No. 1-2 in Table 5 have good indexes of 60 to 70. However, the 1ndex of other tires is thicker. Tires made of rubber 11 using hexamethylenetetramine No. 4 in Table 5 are ■n d L! Although x was good at 72, the moisture and heat resistant adhesion of the tire sample was poor as in the test laboratory evaluation.

(that's all)

Claims (3)

[Claims] (1) Natural rubber or synthetic rubber, resorcin or a resorcin derivative, and per molecule of melamine,
A melamine derivative having a number of bound formalin and a number of methoxy groups in the range of 4≦(number of bound formalin)≦6, 2≦(number of methoxy groups)<6 and a monomer content of 60 to 90% is blended. rubber compositions with improved dynamic properties. (2) The rubber composition according to claim 1, which does not contain silica in the rubber. (3) The rubber composition according to claim 1, wherein the rubber contains silica, and the melamine derivative has a number of methoxy groups per melamine molecule in the range of 4≦(number of methoxy groups)<6.