KR101511666B1 - Method of preparing rubber composition for curing bladder - Google Patents

Abstract

The present invention relates to a process for producing a rubber for curing bladder, which is capable of remarkably improving thermal conductivity while improving the compatibility with rubber by preparing a thermally conductive filler in advance in a master batch with a raw rubber, , The rubber manufacturing method according to the present invention can smoothly manufacture and work the vulcanized bladder, significantly improve the thermal conductivity, shorten the vulcanizing process time, and manufacture the vulcanized bladder with an extended service life have.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a vulcanized rubber bladder,

The present invention relates to a method for producing a rubber for a vulcanized bladder with improved thermal conductivity characteristics. More particularly, the present invention relates to a curing bladder which is capable of significantly improving thermal conductivity while improving graining with rubber by preparing and injecting high crystalline fine graphite as a thermally conductive filler in advance with a raw material rubber, The present invention relates to a process for producing a rubber for a rubber composition.

Vulgar bladders are commonly used in vulcanization processes for the crystallization and heat transfer of the inner form of the tire. Such a vulcanized bladder is used as a medium for supplying a heat source. In order to improve the productivity by shortening the vulcanizing time, excellent thermal conductivity is required.

A conventional vulcanized bladder composition is prepared by adding a filler to a raw rubber so as to withstand steam or hot water. In recent years, various additives have been used to improve the thermal conductivity of vulcanized bladder, . However, the rubber itself has a very low thermal conductivity, and the processability of compounding with a filler having a high thermal conductivity is lowered, causing a problem of deteriorating the physical properties of the final product.

In order to improve the thermal conductivity, it has been proposed to mix Ketjen Black with a common filler as disclosed in Korean Patent Application No. 1999-20743 (June 4, 1999) And the tensile strength is too high and the stretch ratio is low, so that the bladder does not perform well, and there is a decrease in fatigue, an increase in price, and difficulty in dispersion. In addition, if the hardness of the rubber composition becomes too high, it becomes difficult to mount the rubber composition on a cure press, which has disadvantages of deterioration in workability.

Also, as disclosed in Korean Patent Application No. 1997-40146 (Aug. 22, 1997), it is proposed to use graphite excellent in thermal conductivity with a general filler, but it is preferable to use 5 to 10 parts by weight of graphite , The effect of substantially improving the thermal conductivity is not significant. When the amount exceeds the above range, the use of the filler in combination with the conventional filler results in a decrease in the processability and a decrease in the physical / chemical properties due to non-dispersion And the like.

In addition, butyl rubber, which is excellent in heat resistance, aging resistance and air permeability, is mainly used as raw material rubber for rubber compound for bladder. In order to improve the thermal conductivity property when vulcanizing tire, excellent thermal conductivity property as filler, N220 (C / B grade) or N330 (C / B grade), which is a furnace carbon black with a large and well-developed molecular structure, is used. In order to improve the productivity of the tire, a number of measures for shortening the cure time of the tire have been proposed. For example, a method of maintaining the vulcanization temperature of the tire at a high temperature of 180 ° C or more, And a method of using it is used. However, increasing the amount of N330 or N220 furnace carbon black can increase the thermal conductivity, but there is a limit to increase the amount of carbon black used due to dispersion and excessive heat generation. In addition, although acetylene black having a thermal conductivity characteristic superior to N330 or N220 is used in combination with carbon black, there are some problems as well. A major problem is that at least 25 parts by weight of acetylene black per 100 parts by weight of the raw rubber should be used in order to maintain excellent thermal conductivity properties. However, in this case, since the cure rate is lowered and the degree of rubber binding to the raw rubber is lower than that of carbon black, when the polymer is deformed at a high temperature of 185 ° C or higher, ), And the butyl rubber, which is a raw rubber, undergoes a decrease in physical properties due to reduction of heat resistance and aging resistance under high temperature and high pressure steam.

In general, thermally conductive fillers have a critical point of thermal conductivity in view of material properties, and thus there is little effect of improving thermal conductivity when a certain amount of the filler is added.

Further, the addition of the thermally conductive filler to the rubber composition containing the general filler improves the thermal conductivity of the vulcanized bladder to facilitate the heat transfer with the tire, but the bonding force of the rubber with the thermally conductive filler is decreased, . In particular, highly crystalline micrographic graphite can inhibit its bonding with other additives because of its unique lubricity and the absence of molecular chains capable of binding to the rubber.

Therefore, the inventors of the present invention have been studying a method for enhancing the thermal conductivity of a vulcanized bladder using a high-crystalline fine graphite as a thermally conductive filler, thereby improving heat transfer between the tire and a tire, When the high crystalline fine graphite is preliminarily prepared with the masterbatch in the masterbatch and used, it is possible to improve the heat conductivity while improving the problem of compounding with rubber, and thus the present invention has been completed.

Korean Patent Application No. 1999-20743 (June 4, 1999) Korean Patent Application No. 1997-40146 (August 22, 1997) Korean Patent No. 10-0837081

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method for manufacturing a rubber for a vulcanized bladder which can improve the thermal conductivity while maintaining the physical / chemical property level of the rubber even when using a thermally conductive filler.

In order to solve the above problems,

A method for producing a rubber for a vulcanized bladder, characterized in that a thermally conductive filler is introduced into a masterbatch prepared in advance by blending the rubber with a raw rubber. The vulcanized bladder having improved thermal conductivity while maintaining the physical / A method of manufacturing a rubber is provided.

In the method for producing a rubber for a vulcanized bladder according to the present invention, the thermally conductive filler preferably has a crystallinity (Lc) of 30 to 300 nm, a purity of 80 to 99% and a thermal conductivity of 100 W / mK to 200 W / mK is preferable.

It is preferable that the starting rubber is butyl rubber alone or as a resin vulcanizing additive, butyl rubber combined with neoprene at most 35% by weight.

The raw rubber and the thermally conductive filler are preferably mixed in a ratio of 1: 1 to 10: 1 by weight

The method for manufacturing a rubber for a vulcanized bladder according to the present invention comprises the steps of preparing a master batch by blending raw rubber and a thermally conductive filler; Adding a raw rubber, a general filler, an oil, and a thermally conductive filler in this order to prepare a first master batch; Preparing a second master batch in which the first master batch 1/2, the neoprene and the first master batch 1/2 are mixed in order; And mixing the master batch 1/2, resin, ZnO and second master batch 1/2 in this order, wherein the thermally conductive filler is in the form of a master batch with the raw rubber, Of the rubber for a vulcanized bladder.

According to the present invention, when compared with the prior art using a general filler and a thermally conductive filler, it is possible to improve the workability and improve the thermal conductivity remarkably by enabling a smooth compounding process without deteriorating the physical properties of the rubber composition, A rubber composition which can shorten the processing time and prolong the service life can be obtained.

Hereinafter, the present invention will be described in more detail with reference to embodiments. However, these do not limit the technical scope of the present invention.

The rubber composition for a vulcanized bladder according to the present invention contains 5 to 60 parts by weight of highly crystalline fine graphite as a thermally conductive filler per 100 parts by weight of the raw rubber.

As the raw rubber, butyl rubber may be used, and a combination of butyl rubber and neoprene which is a resin vulcanizing additive may be used. In this case, neoprene is preferably combined with butyl rubber in a range of up to 35% by weight. When the content of neoprene is more than 35% by weight, not only the compounding is difficult but also the gelation of the rubber can be caused by the increase of the exothermic temperature during the compounding.

As the thermally conductive filler used for improving the thermal conductivity of the present invention, when the graphite-containing fossil is collected, separated and purified, or calcined at a temperature of 2000 ° C or higher, the crystallinity (Lc) of the filler is 30 nm to 300 nm Or higher, a purity of 80% to 99%, and a thermal conductivity of the filler itself of 100 W / mK to 200 W / mK. They are preferably used in a range of 5 to 60 parts by weight based on 100 parts by weight of the starting rubber. When the thermally conductive filler is used in an amount of less than 5 parts by weight, the effect of improving the thermal conductivity may be insufficient. When the thermally conductive filler is used in an amount exceeding 60 parts by weight, problems may arise in combination with rubber.

The rubber for vulcan bladders may contain, in addition to the thermally conductive filler, ordinary fillers, vulcanizing resins, zinc oxide for crosslinking the resin, and oils.

The term "general filler" refers to fillers such as carbon black, silica and the like generally used in this field, and it is generally preferable to use Furnace Black (generic name) for rubber compositions for vulcanized bladders. Acetylene black may also be used. They are preferably contained in the range of 10 to 60 parts by weight based on 100 parts by weight of the raw rubber.

As the vulcanizing resin (or resin), an alkylphenol vulcanizing resin may be used, and it may be used in a range of 3 to 15 parts by weight based on 100 parts by weight of the starting rubber.

The castor oil may be used as the oil, and may be used in an amount of 0 to 20 parts by weight, preferably 1 to 15 parts by weight, based on 100 parts by weight of the raw rubber.

The zinc oxide for crosslinking the resin may be used in an amount of 3 to 10 parts by weight based on 100 parts by weight of the raw material rubber.

The rubber composition for a vulcanized bladder may be a processing aid. The processing aid may be stearic acid, a dispersion homogenizer or the like. The composition may be varied depending on the compounding method and the type of the blender, .

Wherein the rubber composition for vulcanized bladder comprises 10 to 60 parts by weight of a general filler based on 100 parts by weight of a raw rubber in which 65 to 100 parts by weight of butyl rubber and 0 to 35 parts by weight of neoprene as a resin vulcanizing additive are mixed; 5 to 60 parts by weight of a thermally conductive filler; 3 to 15 parts by weight of a vulcanized resin; 0 to 20 parts by weight of oil; And 3 to 10 parts by weight of zinc oxide for resin crosslinking.

In addition, the present invention facilitates the construction of a conductive pathway by using high-crystalline fine graphite, which is high in crystallinity and has a plate-like structure, different from a general filler as a thermally conductive filler, It is possible to expect shortening of the vulcanization process time.

The rubber for a vulcanized bladder according to the present invention comprises a raw material rubber and a thermally conductive filler to prepare a master batch; Adding a raw rubber, a general filler, a thermally conductive filler and an oil in this order and mixing them to prepare a first master batch; Preparing a second master batch in which the first master batch 1/2, the neoprene and the first master batch 1/2 are mixed in order; And mixing the master batch 1/2, resin, ZnO and second master batch 1/2 in order, wherein the thermally conductive filler is in the form of a master batch with the raw rubber, .

The preparation of the masterbatch and the introduction of the raw rubber and the thermally conductive filler in the previous step of preparing the first masterbatch can increase the thermal conductivity without changing the physical properties of the final rubber.

The master batch of the raw rubber and the thermally conductive filler may be prepared by kneading the raw rubber for 1 to 80 seconds and then adding the thermally conductive filler in the order. In this case, the raw rubber and the thermally conductive additive are preferably mixed in a weight ratio of 1: 1 to 10: 1. If the weight ratio of the raw rubber to the thermally conductive additive is 2: 1, the mixing time may be about 60 to 300 seconds at 30 to 60 RPM, except for the kneading time.

In the case of the above-mentioned blending, not only highly crystalline fine graphite thermally conductive fillers but also all other fillers difficult to disperse such as carbon nanotubes (CNT), acetylene black, N110 and N220 high- May also be applied.

The master batches of the raw rubber and the thermally conductive filler prepared as described above are put into a rubber compounding system, which is described below, by adjusting the required amount.

Subsequently, the first step of producing the first master batch is carried out by adding the raw rubber, the general filler, the thermally conductive filler and the oil in this order, in which case the mixing is carried out at a temperature of 40 to 60 DEG C and 40 to 50 rpm .

Specifically, it is preferable that the raw rubber is firstly soviet within approximately 20 to 100 seconds. The Soviet process is sometimes referred to as a descent operation, which means that the rubber is softened by causing shear force and heat to cause depolymerization, resulting in a uniform plasticized state. The Soviet process is a low-temperature Soviet method and a high-temperature Soviet method, and is influenced by the workability and physical properties of the rubber product depending on the degree of the Soviet Union. For example, when the Soviet work is insufficient, the physical properties of the product are lowered, the shrinkability is increased, and the appearance is poor. On the contrary, when the Soviet Union becomes excessive, the physical properties of the product are largely lowered, and the shrinkability is very small, but the appearance is generally good. The Soviet operation according to the present invention is performed sufficiently within about 20 to 100 seconds.

Examples of the mixer that can be used in the Soviet process include a roll mill, a Kneader, a Banbury mixer, and the like

Subsequently, a master batch of thermally conductive filler such as ordinary filler such as furnace black, oil such as castor oil, and high crystalline fine graphite is added to the soviet raw rubber in order and mixed to prepare a first master batch. A processing aid such as stearic acid or a dispersion homogenizer may be added to the first master batch.

A second master batch is produced by mixing the first master batch (1/2) obtained in the first step, the neoprene and the first master batch (1/2) in this order, followed by a second step of producing a second master batch, Is preferably carried out at a temperature of 40 to 60 DEG C and 40 to 60 rpm.

Followed by a third step of mixing the second master batch 1/2, resin, ZnO and second master batch 1/2 obtained in the second step in this order, wherein the blending is carried out at a temperature of 40 to 60 ° C Temperature and 40 to 50 rpm.

Here, the master batch means a compounded rubber formed by adding raw material rubber and additives and dispersing them.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

Production Example 1

Master batch of raw rubber and thermally conductive filler

The raw rubber was kneaded in a mixer for about 60 seconds and then mixed with the thermally conductive filler (high crystalline fine graphite) at 45 RPM for about 100 seconds to prepare a master Batches are manufactured.

Example 1

(Butyl rubber) was sacked with reference to the components and contents shown in the following Table 1, a general filler (N220) was added, oil (castor oil) was added and the raw rubber of Production Example 1 was added with a thermally conductive filler The master batch was weighed and added in the desired amount, and mixed at a temperature of 50 캜 and 50 rpm to prepare a first master batch. For the dispersibility of neoprene, the first master batch 1/2 corresponding to half (1/2) of the first master batch, neoprene and the first master batch 1/2 were added in order and the TCU temperature at 50 rpm and 50 캜 To prepare a second master batch. Then, the rubber was prepared by blending the second master batch 1/2, resin, ZnO and second master batch 1/2 under the conditions of 45 rpm and 50 캜 to facilitate dispersion of the resin.

Example 2

A rubber composition was prepared in the same manner as in Example 1, except that acetylene black was further added after the general filler (N220) in the production of the first master batch in Example 1.

Comparative Example 1

The raw rubber (butyl rubber) was sieved, followed by the usual filler (N220), an oil, a thermally conductive filler (high crystalline fine graphite), and the like, without using a master batch made of a thermally conductive filler in the raw rubber of Production Example 1. [ And mixed at a temperature of 50 RPM and 50 캜 to prepare a first master batch. Subsequently, a first master batch of 1/2, neoprene, and a first master batch were put in order and mixed at 50 RPM and 50 캜 to prepare a second master batch. Subsequently, a second master batch of 1/2, resin, ZnO and a second master batch of 1/2 were put in order and mixed at 45 RPM and 50 캜 to prepare a rubber.

Comparative Example 2

       In the production of the first master batch, rubber was produced in the same manner as in Comparative Example 1, except that the rubber was charged in the order of rubber, polymer, general filler (N220), acetylene black, oil and thermally conductive filler (high crystalline fine graphite) Respectively.

Raw material Comparative Example 1 Comparative Example 2 Example 1 Example 2 Butyl rubber 95 95 95 95 Neoprene 5 5 5 5 Normal filler (N220) 30 30 30 30 Acetylene black - 30 - 30 High crystalline fine graphite 30 7 30 7 Resin 8 8 8 8 Zinc oxide 5 5 5 5 Castor oil 6 6 6 6

Test Example 1

Each of the rubber compositions of Examples 1 and 2 and Comparative Examples 1 and 2 was pressurized with a hot press for 60 minutes to prepare a plate having a thickness of 3 mm and then a hardness and a modulus of 300% Modulus, tensile strength and elongation were measured, and thermal conductivity and fatigue test were respectively measured before aging and after aging (100 占 폚 占 24 hours), and the results are shown in Table 2 below.

division Comparative Example 1 Comparative Example 2 Example 1 Example 2 Hardness (Shore A) 66 69 67 70 300% modulus 55 65 58 67 Tensile strength (kgf / cm2) 141 140 140 142 Elongation (%) 700 650 700 660 Thermal conductivity 0.368 0.355 0.371 0.357 Fatigue test
(Demattia) Before aging 100 thousand times ↑ 100 thousand times ↑ 100 thousand times ↑ 100 thousand times ↑ After aging
(100 < 0 > C X 24hrs) 80,000 times 70,000 times 90,000 times 100,000 times Evaluation of finished products
phenomenon

Inner bubble Outer bubble normal normal Service life 270 times 280 times 320 times 330 times

* The hardness means the harder the higher the value.

* Tensile properties (300% modulus, tensile strength, elongation) mean that the higher the value, the better each property.

* The fatigue test means that the higher the number of times, the higher the durability, for example, the fatigue resistance.

* The higher the thermal conductivity, the better the heat transfer.

* The evaluation of the finished product shows the internal phenomenon (shape change) after using the actual vulcanized bladder. The use frequency is the actual lifetime. The higher the value, the longer the life.

  In Examples 1 and 2, the physical properties and the thermal conductivity were the same as those of Comparative Example 1 and Comparative Example 2, and the fatigue characteristics after aging were more excellent. Comparative Examples 1 and 2 cause defects such as air bubbles when the articles are actually used in accordance with the interference of the high-crystalline fine graphite with the general filler, and the phenomenon is as shown in the above table, And 2 showed longer lifetimes than those of Comparative Examples 1 and 2 at least 50 times.

Claims (5)

Adding raw rubber, carbon black, oil and fine graphite in this order and mixing them to prepare a first master batch;
Preparing a second master batch in which the first master batch 1/2, the neoprene and the first master batch 1/2 are mixed in order; And
A second master batch 1/2, a resin, ZnO, and a second master batch 1/2 in this order. The method according to claim 1,
Wherein the fine graphite has a crystallinity (Lc) of 30 to 300 nm and a purity of 80 to 99%, and has a thermal conductivity of 100 W / mK to 200 W / mK. The method according to claim 1,
Wherein the raw material rubber is butyl rubber alone or as a resin vulcanizing additive, butyl rubber having a maximum of 35 weight% of neoprene combined therewith. The method according to claim 1,
Wherein the raw rubber and the fine graphite are blended in a weight ratio of 1: 1 to 10: 1. delete