JP2009215516A - Method for producing natural rubber-blended composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing the natural rubber-blended composition without passing through a mastication process of the natural rubber and without adversely affecting subsequent vulcanizate properties. <P>SOLUTION: The method for producing natural rubber-blended composition is to knead TSR type natural rubber, giving ≤20% amount of polymer gel within 2 weeks after the production, with carbon black in a kneading process (excluding a vulcanizing agent)without carrying out the mastication process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a natural rubber compounding composition. More specifically, the natural rubber compounding process is carried out efficiently at low cost without adversely affecting the physical properties of the subsequent vulcanization without going through a natural rubber mastication step. The present invention relates to a method for producing a natural rubber compounding composition capable of producing a composition.

In general, natural rubber used in the rubber industry is obtained by coagulating and drying rubber tree sap (natural rubber latex) called Hevea brasiliens cultivated in the tropics.
Natural rubber is widely used in a large amount in the rubber industry and the tire industry because of its excellent physical properties. The natural rubber latex immediately after production has a low Mooney viscosity of 60 to 70, but after harvesting, the Mooney viscosity rises to near 90 to 100 within a few months of storage and transportation (this is storage hardening [ storage hardening]).

  As a cause of natural rubber storage and curing, it is said that a heterogeneous bond (such as an aldehyde group) in the isoprene chain crosslinks and reacts with proteins and amino acids in the natural rubber to cause gelation (increase in gel amount) ( The mechanism is not clearly elucidated in the literature). Gelation in natural rubber deteriorates processability. In general, natural rubber preferably has a large molecular weight in view of physical properties, and a decrease in molecular weight adversely affects the physical properties of natural rubber. The molecular weight and polymer gel amount greatly depend on the natural rubber production conditions after collection and the subsequent storage conditions.

  There are two typical methods for manufacturing natural rubber: ribbed smoked sheet (RSS type) and technically rated rubber (TSR type) according to international quality packaging standards (commonly known as Green Book) for natural rubber grades. It is. Of these, the TSR type is broadly divided into two types: wet process and dry process. Natural rubber latex collection → cup lamp production (formic acid is placed in a latex cup in advance and solidified naturally, collection It is a common process until it is tapped by a farmer, etc., and this cup lamp, USS / RSS, etc. are mixed, crushed by a wet process or a dry process, moved to a bucket, dried with a dryer, It is manufactured in the order of packing by pressing to form blocks.

When producing rubber materials such as tires using this TSR-type natural rubber, usually after kneading to reduce the Mooney viscosity of natural rubber (NR), the rubber composition excluding the vulcanizing agent is added to the raw rubber A non-pro (NP) kneading agent is kneaded, and then the non-pro kneaded rubber is sufficiently cooled, followed by a professional kneading in which a rubber compounding agent containing a vulcanizing agent is added and further kneaded.
However, when the above kneading is performed, the rubber physical properties are improved as compared with the case where the kneading is not performed, but there is a problem that the kneading productivity is lowered.

On the other hand, as a technique for eliminating the mastication process of natural rubber, for example, a process for producing natural rubber, which includes, for example, a process of drying natural rubber and a process of adding a viscosity stabilizer such as a hydrazide compound diluted in a solvent to natural rubber (For example, refer to Patent Document 1) or a natural rubber raw material before drying, a method for producing natural rubber, characterized by adding a viscosity stabilizer such as a hydrazine degree compound by immersion and / or spraying (for example, A method using a high-viscosity natural rubber to which a viscosity stabilizer obtained in Patent Document 2) is added is known.
However, the method using a high viscosity natural rubber to which a constant viscosity agent is added is expensive and has problems such as an increase in production cost.
JP 2001-354703 A (Claims, Examples, etc.) JP 2001-354704 A (Claims, Examples, etc.)

  In view of the above-described conventional problems, the present invention intends to solve this problem, and does not go through a natural rubber mastication step, and does not adversely affect subsequent vulcanization properties, and can be efficiently performed at low cost. It aims at providing the manufacturing method of the natural rubber compounding composition which can manufacture a natural rubber compounding composition.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors incorporated a specific TSR type natural rubber into the above-mentioned natural rubber compound by kneading carbon black in a non-pro kneading process without performing a kneading process. The present inventors have found that a method for producing a composition can be obtained, and have completed the present invention.

  That is, the present invention is characterized by kneading carbon black in a non-pro kneading process without performing a kneading process on a TSR type natural rubber having a polymer gel amount of 20% or less within 2 weeks from the production. It exists in the manufacturing method of a rubber compounding composition.

  According to the present invention, there is provided a production method capable of producing a natural rubber compounded composition efficiently at a low cost without adversely affecting subsequent vulcanization properties without going through a natural rubber mastication step. Is done.

The best mode of the present invention will be specifically described below.
The manufacturing method of the natural rubber compounding composition of the present invention is such that a TSR type natural rubber having a polymer gel amount of 20% or less is kneaded with carbon black in a non-pro kneading process without performing a kneading process within two weeks from the production. It is characterized by

In the present invention, the natural rubber to be used is a TSR type natural rubber having a polymer gel amount of 20% or less within 2 weeks from the production. Normally, TSR type natural rubber is manufactured in the following order: natural rubber latex collection → cup lamp preparation → cup lamp, USS / RSS etc. mixed → crumb preparation by wet process or dry process → drying → press molding to block → packing In the present invention, a polymer gel amount of 20% or less is used within 2 weeks from the above production. Preferably, it is desirable to use a polymer gel amount of 15% or less from the viewpoint of further exerting the effects of the present invention.
Even if it is TSR type natural rubber, if the amount of the polymer gel exceeds 20%, the effect of the present invention cannot be exhibited. In general, the amount of polymer gel of TSR type natural rubber gradually increases immediately after production, and usually the amount of polymer gel exceeds 20% when about 2 weeks have passed since production. If the amount of this polymer gel is large, the dispersion of carbon black is hindered in the non-pro kneading process, and the reinforcing property of the carbon black is also lowered. Therefore, the elastic modulus and fracture strength of the vulcanized rubber are lowered. Tend to. Therefore, usually, mastication is performed and a non-professional kneading process is performed to improve vulcanization physical properties. By this mastication, the polymer gel amount becomes 20% or less.

  In the present invention, if the TSR type natural rubber has a polymer gel amount of less than 20% within 2 weeks from the production, the same characteristics as in the case of using the kneaded rubber can be obtained without carrying out mastication. Will be able to. In addition, TSR type natural rubber exceeding 2 weeks from the production is not preferable because the amount of polymer gel exceeds 20% and the rubber physical properties are adversely affected.

  In the present invention (including examples to be described later), the amount of polymer gel is measured by swelling 0.2 g of rubber in toluene overnight, treating with a centrifuge at 35,000 rpm for 1.5 hours, and setting the precipitated gel in a draft. 2 days, dried and weighed, and the value (%) divided by the total weight of the original polymer gel.

  In the present invention, the carbon black used in the non-pro kneading step without performing the mastication step is not particularly limited, and may be a commercially available one depending on the application, for example, a commercially available one that is usually used for tire manufacture. Examples of the carbon black include carbon blacks such as SAF, ISAF, and HAF grades.

These carbon blacks can be used singly or in combination of two or more, and the blending amount thereof varies depending on the use, but within 2 weeks from production, the polymer gel amount is 20%. It is used in the range of 5 to 100 parts by mass, preferably 30 to 70 parts by mass, with respect to 100 parts by mass of TSR-type natural rubber below.
If the blending amount of the carbon black is less than 5 parts by mass, the effect of blending the carbon black cannot be obtained. This is undesirable.

In the production method of the present invention thus configured, natural rubber latex collection → cup lamp production → mixing cup lamp, USS / RSS, etc. → crumb production by wet process or dry process → drying → press molding to block → By kneading carbon black in a non-pro kneading process without performing the mastication process, the TSR type natural rubber having a polymer gel amount of 20% or less is manufactured within 2 weeks from the production in the order of packing. A natural rubber compounding composition can be efficiently produced at low cost without adversely affecting the subsequent vulcanization properties. Usually, it is difficult to carry out the non-pro kneading process within 2 weeks after the production of TSR-type natural rubber, but the efficiency of removing the kneading process by adjoining the natural rubber processing factory and the kneading factory. It is possible to adopt a typical manufacturing process.
In the non-pro kneading step of the present invention, if necessary, it may contain optional components such as a filler other than carbon black, a softening agent, etc., excluding the vulcanizing agent, the vulcanization accelerator, and the vulcanization acceleration aid. it can. In addition, the natural rubber compounded composition obtained by the method of the present invention has good dispersibility of carbon black, can improve the reinforcing property of carbon black, and improve the elastic modulus and fracture strength of rubber after vulcanization. It becomes.

  Next, the present invention will be described more specifically and in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1-2 and Comparative Examples 1-2]
As the TSR type natural rubber, TECHNICALLY SPECIFED RUBBER (product number: SMR # 20), which has passed for 8 days from the production, was used.
The amount of the natural rubber polymer gel (in Comparative Example 1 after mastication by the following method) was measured by the following method.
Each TSR type natural rubber (100 parts by mass) was prepared by blending 40 parts by mass of carbon black (N234) using a Banbury mixer (non-pro process).
Next, the following blending components were blended into the natural rubber blending composition left at room temperature for 130 days by the following blending method to prepare a rubber composition. The resulting rubber composition was measured for the elastic modulus (M300) at 300% elongation, which is a vulcanized physical property, by the following method.
These results are shown in Table 1 below.

(Mastication method of Comparative Example 1)
The kneading conditions were performed with a Banbury mixer at a kneading time of 90 seconds and a product temperature of 140 ° C.
(Measurement method of polymer gel amount)
0.2 g of rubber was swollen in toluene overnight, treated with a centrifuge at 35,000 rpm for 1.5 hours, the sedimented gel was left to dry in a fume hood for 2 days, and weighed as a polymer gel divided by the original total weight. The value (%) was evaluated.

(Compounding component, 100 parts by mass of TSR natural rubber)
40 parts by mass of carbon black, 3.5 parts by mass of zinc white, 2.0 parts by mass of stearic acid, 1.5 parts by mass of sulfur, 1.0 part by mass of phenylenediamine-based antioxidant, vulcanization accelerator (CZ) 5 parts by mass (mixing method)
In a Banbury mixer, other than sulfur and a vulcanization accelerator were kneaded to prepare a non-pro by a conventional method, and then the remaining chemicals were kneaded at a discharge temperature of 110 ° C. or less to prepare a pro rubber.

(Measurement method of M300)
The elastic modulus (M300) at 300% elongation after vulcanization was measured using a dumbbell-shaped sample of JIS No. 3 according to JIS K 6300-2001.

  As is clear from the results of Table 1 above, Examples 1-2, which are the scope of the present invention, can reduce the amount of polymer gel relatively compared to Comparative Examples 1-2, which are outside the scope of the present invention. It has been found that a natural rubber compounding composition can be produced efficiently at low cost without going through the mastication step and without adversely affecting the subsequent vulcanization properties.

  In the present invention, since an efficient manufacturing process in which the mastication step is removed can be adopted, a natural rubber compounding composition that can be suitably used for rubber products such as belts and conveyors in addition to tire products is provided. It will be a thing.

Claims (1)

  Production of a natural rubber compounding composition characterized in that carbon black is kneaded in a non-pro kneading process without performing a mastication process on TSR type natural rubber having a polymer gel amount of 20% or less within 2 weeks of production. Method.