JPH07227845A - Reutilization of unvulcanized foamed rubber - Google Patents

Abstract

PURPOSE:To reutilize unvulcanized foamed rubber by adding water in the re- milling (RFM) process of a final mill and a master batch remilling (RMB) process to control the temp. of rubber to the optimum range and suppressing the foaming of vulcanized matter caused by the mixing with nonstandard foamed rubber. CONSTITUTION:In the reutilization of unvulcanized foamed rubber, 0.3 6 pts.wt. of water is added to' 100 pts.wt. of unvulcanized foamed rubber and this water added rubber is kneaded within a falling temp. range of 90-120 deg. by a hermetically closed mixer or a master batch of usual tread rubber is mixed with 20wt.% or less of treated unvulcanized rubber when it is again masticated and 0.3-10 pts.wt. of water is further added to the master batch and the resulting mixture is kneaded at 140-190 deg. by the hermetically closed mixer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reusing an unvulcanized and foamed rubber material for tires as a normal unvulcanized rubber.

[0002]

2. Description of the Related Art The foamed rubber (multi-cell compound) used for winter tires controls the foaming rate in order to improve the performance on ice and the performance on snow. However, since foaming is a chemical change, it is very unstable,
The vulcanization speed is greatly affected by the temperature during kneading, the degree of dispersion, and the time for which the kneaded rubber is left, especially due to moisture absorption when left unattended. Test using). Further, the extruded tread contracts due to cooling, and therefore, when the tread is cut, a contraction amount is expected, but a dimensional variation occurs depending on the temperature and the extrusion conditions. Therefore, at the stage of unvulcanized rubber such as extruded tread, those that do not meet the foaming standard or those that do not meet the dimensional standard cannot be directly applied to tire products, so it is necessary to reuse them by another method. is there.

At present, as a processing method, there are a method of mixing the same kind of rubber and reusing it, and a method of discarding it.

Conventionally, in winter, tires have been used by driving spike pins in order to satisfy ice performance and snow performance. However, due to dust problems and road maintenance problems, the use of spike pins has been postponed, and tire manufacturing companies have decided to use them. ,
We have come to provide alternative tires. As one of the measures, there is a method of ensuring various performances by foaming the tread rubber in contact with the road surface and controlling the foaming rate.

This foamed rubber is obtained by adding azodicarbonamide (ADCA), azobisformamide (ABFA), the same type of tread rubber as that which is usually applied.
Azo compounds such as azobisinbutyronitrile (AIBN) and diazoaminobenzene (DAB), N, N'-
Dinitrosopentamethylenetetramine (DPT), N,
Nitroso compounds such as N'-dimethyl-N, N'-dinitrosoterephthalamide (DMDNTA), P, P '
-Oxybis (benzenesulfonyl hydrazide (OBS
H), benzenesulfonyl hydrazide (BSH), toluene sulfonyl hydrazide (TSH) and other hydrazide-based decomposable blowing agents, that is, compounds that decompose at the vulcanization temperature and release gas are added and kneaded. It is foaming.

However, when the target product performance is not obtained in the manufacturing stage, especially in the extruded tread product, that is, when the foaming rate does not satisfy the standard or the dimension is not satisfied, it is directly applied to the product. It is excluded, repeated (remill) again, mixed with other rubber and reused.

The problems at this point are as follows. That is, (1) since it is a foamed rubber, if it is mixed in with a material other than the foamed rubber, it foams during vulcanization, resulting in a marked decrease in tire performance. (2) Therefore, if the foamed rubber is mixed and treated, the viscosity of the unvulcanized rubber is changed, and the foaming rate after vulcanization is changed. Therefore, it is necessary to change the amount of the foaming agent in a timely manner. Will be significantly reduced. (3) Further, the disposal process is not only costly but also unfavorable because it causes a problem of industrial waste.

[0008]

The object of the present invention is to provide an unvulcanized foamed rubber that does not meet the standards in terms of foaming ratio, dimension, etc.
It is possible to effectively decompose the foaming agent and mix it with normal tread rubber without mixing it with other foamed rubber to reduce productivity or cause industrial waste problem. It is to provide a method for reusing vulcanized and foamed rubber.

[0009]

Means for Solving the Problems As a result of earnest research on the above-mentioned problems imposed on the reuse of unvulcanized tire foam rubber that cannot be diverted to tire products, the present inventors have found that during kneading. The present invention has been completed by finding a method for decomposing and removing the foaming agent.

That is, the present invention is as follows. (1) 0.3 to 100 parts by weight of unvulcanized and foamed rubber
6 parts by weight of water is added, and the dropping temperature is 90 ° C to 120 ° C.
A method for reusing unvulcanized and foamed rubber, which comprises kneading with an internal mixer in the temperature range of.

(2) When a masterbatch of a normal tread rubber containing no foamed rubber is masticated (remilled) again, unvulcanized rubber obtained by decomposing the foaming agent by the method of claim 1 is mixed, and this rubber is mixed. The mixture is set to 100% by weight so that the unvulcanized rubber obtained by decomposing the foaming agent becomes 20% by weight or less.
Add 10 parts by weight of water, fall temperature 140 ° -190 ° C
A method for reusing unvulcanized and foamed rubber, which comprises kneading with an internal mixer in the temperature range of.

The mastication is to impart sufficient plasticity to the raw rubber by applying mechanical shearing force.
As a result, it facilitates the mixing and kneading work such as making it easier to disperse the compounding agent, and further stabilizes the dimensions, cleans the skin, makes it difficult to scorch, etc. in the subsequent processes such as rolling and extrusion. Plays a role in making things easier.

It is known that mastication is closely related to the operating temperature and that the plasticizing effect of natural rubber is good at a temperature of 110 to 120 ° C. and at a temperature lower and higher than that temperature. . Further, mastication is easily affected by oxygen in the air, and in nitrogen, the plasticity change due to mastication is small. In mastication at low temperature, rubber molecules are cut by mechanical shearing force such as rolls, and oxygen and other radical acceptors are added to the radicals generated thereby, mastication is performed and plasticity (molecular weight ) Is said to decrease. In this case, mastication can be performed even in nitrogen if an effective radical acceptor is present.

For high temperature mastication, a Gordon plasticizer or a closed kneader is mainly used. In recent years, high-temperature mastication is often used because it has higher productivity, better workability, and higher safety than a roll machine. In particular, high-temperature mastication using a mastication accelerator is common.

In the case of high-temperature mastication, a particular note is the temperature. High-temperature mastication is considered to be a kind of heat deterioration because mastication proceeds by a chemical reaction with oxygen at a high temperature, so plasticizing at a too high temperature in a short time is a physical property of the compound, especially exothermic heat. It should be noted that it may adversely affect heat aging and heat aging.

In general, the step of kneading a polymer, a filler, an antiaging agent, etc. may be referred to as masticating, and the step of uniformly kneading various compounding agents into a raw rubber may be referred to as kneading, but both of them may be combined. Sometimes called kneading. The step of kneading the polymer, the filler, the antioxidant, etc. is called a masterbatch (abbreviated as MB), and the step of kneading the masterbatch again is called a masterbatch remill (abbreviated as RMB).

The kneading in a narrow sense, in which a vulcanizing agent, a vulcanization accelerator, a foaming agent and the like are added to the MB or RMB to uniformly knead, is referred to as a final mill (abbreviated as FM). The step of kneading the final mill again will be referred to as a remill of the final mill (abbreviated as RFM).

In the present invention, when the unvulcanized foamed rubber is remilled (RFM), it is added to 100 parts by weight of the rubber.
Adding 3 to 6 parts by weight of water and kneading with a closed mixer is performed by lowering the reaction start temperature of the foaming agent in the foamed rubber,
This is because the foaming agent reacts with water and decomposes and is consumed without foaming during kneading. When the amount is less than 0.3 parts by weight, the effect is small, and when the amount is more than 6 parts by weight, the rotor and the rubber are mixed. This is because slippage occurs between them and it takes a long time to knead.

The dropping temperature is preferably 90 ° C. to 120 ° C. When the dropping temperature is lower than 90 ° C., water remains in the rubber and remarkably affects the vulcanization reaction, and when it is higher than 120 ° C.
This is because it is not desirable because it causes scorch.

In the first invention, the RFM of foamed rubber is performed by
This is because the foaming agent is decomposed at an early stage by adding water at the earliest stage until the rubber is supplied to the next step, so that the foaming of the general tread rubber is suppressed to a low level, and it is composed of various kinds of rubber. It also has the meaning of making the foamed tread rubber uniform and improving the dispersion when mixed with general rubber. Although there are some rubber materials that can be treated only by the first invention, some rubbers are not sufficient by the treatment of the first invention. In this case, therefore, in the second invention in which general rubber is mixed, water is added, and Decomposes the blowing agent.

Next, the unvulcanized rubber obtained above is mixed in 20% by weight or less with 100% by weight of the rubber mixture at the time of remill (RMB) of commonly used tread rubber,
Further, adding 0.3 to 10 parts by weight of water to 100 parts by weight of this rubber mixture and kneading with a closed mixer is
This is because if the amount of mixing exceeds 20 parts by weight, scorch tends to occur, and the amount of water added is for the same reason as above. Further, the falling temperature is preferably in the range of 140 ° to 190 ° C.
This is because if the temperature is lower than 0 ° C., the foaming agent is not completely consumed and remains, and if the temperature is higher than 190 °, gelation of the rubber proceeds, which is not preferable in terms of processability.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(1) Final Mill Remill (RFM)

[Table 1]

(2) Master batch remill (RMB)

[Table 2] For the prototype No. 1 in Table 2, mixed rubber types A to E in Table 1
5 kinds of are applied.

(3) The compositions of A to E in Table 1 were replaced with those in Table 2
Table 3 shows the foaming degrees of the vulcanizates obtained as trial production results, which were used as the mixed rubbers for trial production of Nos. 6 to 6. With regard to the component E, because of the scorch, it was not possible to proceed to RMB. The degree of foaming of the vulcanizate is 17 for a sample of 10 mm x 100 mm x 70 mm.
The state when vulcanized at 0 ° C. for 3 minutes and 160 ° C. for 3 minutes was observed.

[0026]

[Table 3]

A diagrammatic description of the embodiment is shown in FIG.

Regarding the concept of the mixing treatment of the kneaded tread rubber, N, N'-dinitrosopentamethylenetetramine (DP) was used as a foaming agent.
T) P, P'-oxybis (benzenesulfonylhydrazide) (OBSH) Azodicarbonamide (ADCA) is used. Table 4 shows the decomposition temperatures obtained from the absorption peak values by differential thermal analysis (DSC).

[0029]

[Table 4]

[0030]

EFFECT OF THE INVENTION In the remill (RFM) and masterbatch remill (RMB) steps of the final mill, water is added to control the rubber temperature to an optimum state, whereby foaming of the vulcanized product due to mixing of the foamed rubber occurs. I was able to suppress it.

[Brief description of drawings]

FIG. 1 is a diagram of a foaming agent decomposition process corresponding to (1) and (2) of the present invention.

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Claims (2)

[Claims] 1. To 100 parts by weight of unvulcanized and foamed rubber,
Add 0.3 to 6 parts by weight of water, and further drop temperature 90 ℃ ~
A method for reusing unvulcanized and foamed rubber, which comprises kneading with a closed mixer in a temperature range of 120 ° C. 2. An unvulcanized rubber obtained by decomposing a foaming agent by the method according to claim 1, when remastering a masterbatch of a normal tread rubber containing no foamed rubber, and mixing this rubber mixture. Is set to 100% by weight so that the unvulcanized rubber obtained by decomposing the foaming agent becomes 20% by weight or less, and 0.3 to 10 parts by weight of water is added to 100 parts by weight of this rubber mixture, and the dropping temperature is set to 140%. A method for reusing unvulcanized and foamed rubber, which comprises kneading with a closed mixer in a temperature range of ° C to 190 ° C.