JPH03239739A - Rubber composition - Google Patents

Abstract

PURPOSE:To prepare a rubber compsn. which exhibits a low hardness in an unvulcanized state convenient for processing and a high hardness when vulcanized by compounding a natural or synthetic rubber with a specified amt. of a specific acid-modified isoprene rubber. CONSTITUTION:100 pts.wt. at least one rubber selected from the group consisting of natural and synthetic rubbers is compounded with 0.5-50 pts.wt. acid-modified isoprene rubber which shows characteristic absorptions around 3400cm<-1> and 1720cm<-1> in the infrared absorption spectrum and an absorption peak in a range of 0-120 deg.C in differential scanning calorimetry. The resulting compsn. exhibits such a low hardness in an unvulcanized state as that of the conventional rubber compsn. compounded with a softener, e.g. process oil, while showing a hardness, when vulcanized, similar to or higher than that of a compsn. contg. no softener.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a rubber composition, and more specifically, to a rubber composition that improves the processability of unvulcanized rubber and improves the hardness after vulcanization. The present invention relates to a rubber composition containing a novel rubber softener exhibiting the following properties.

<Prior art> In the field of manufacturing rubber products, various softeners have traditionally been added to unvulcanized rubber compositions in order to improve workability and processability during kneading and molding. are doing. Examples of softeners that are used include process oils, petroleum resins, petroleum-based softeners such as coumaron/indene resin, and plant-based softeners such as castor oil and rapeseed oil.

However, although these softeners improve the processability of unvulcanized rubber compositions, they have the drawback of reducing the physical properties, particularly the hardness, of vulcanized rubber products.

Therefore, rosin has been proposed as a softener and tackifier that does not reduce the hardness of vulcanized rubber products, but when rosin is used, the vulcanization rate is significantly delayed.

Recently, liquid natural rubber and isoprene rubber have been proposed as reactive plasticizers that have a softening effect on unvulcanized rubber compositions equivalent to that of process oils and do not deteriorate the physical properties of vulcanized rubber products. However, the hardness of vulcanized rubber products still decreases in proportion to the amount of the reactive plasticizer blended.

<Problems to be Solved by the Invention> The present invention has been made in view of the above facts, and because it contains a new softener, it has a hardness that is easy to process when uncured, and it has a hardness that is easy to process after vulcanization. The purpose of the present invention is to provide a rubber composition having high hardness.

Means for Solving the Problems> The present invention provides at least one type of rubber (A) selected from natural rubber and synthetic rubber, and an infrared absorption spectrum of 340
It contains an isoprene-based rubber oxidized modified product (B) which has characteristic absorption near 0 cm-' and near 1720 am-' and an absorption peak in the range of 0 to 120°C in a differential scanning calorimeter, and contains an isoprene-based rubber acid. The content of the modified substance (B) is
The present invention provides a rubber composition characterized in that the amount is 0.5 to 50 parts by weight per 100 parts by weight of the rubber (A).

The oxidized isoprene-based rubber (B) is preferably soluble in chloroform.

Further, the isoprene rubber oxidation-modified product (B) is preferably a modified product derived from an isoprene copolymer produced using isoprene as one of the raw material monomers.

Furthermore, the isoprene rubber oxidation-modified product (B) is preferably a modified product derived from an isoprene rubber having one or more polar functional groups in the molecule.

The present invention will be explained in detail below.

The rubber contained in the rubber composition of the present invention is one or more rubbers (A) selected from natural rubber and synthetic rubber.

Specific examples include natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, ethylene-propylene copolymer rubber, isoprene-isobutylene copolymer rubber, chloroprene rubber, etc., and these may be used alone or as a blend. It can be used as

The rubber composition of the present invention has characteristic absorptions in the vicinity of 3400 cm-' and 1720 cm-' in the infrared absorption spectrum, and 0 to 120 cm in the differential scanning calorimeter.
The oxidized isoprene-based rubber compound (B) having an absorption peak in the range of °C is a compound obtained by dissolving isoprene-based rubber in a hydrocarbon-based organic solvent and irradiating it with sunlight or ultraviolet rays in the presence of oxygen. be.

Here, isoprene-based rubbers include natural rubber (NR), synthetic isoprene rubber (IR), depolymerized isoprene rubber, cyclized polyisoprene, isoprene-based copolymers, and those containing one or more polar functional groups in the molecule. It is a rubber that contains isoprene as a monomer constituting its molecule, such as isoprene-based rubber (natural rubber, synthetic isoprene rubber, and isoprene-based copolymer).

Specifically, natural rubber includes commonly used NR with a cis-1,4 bond structure, balata and gatsutano<-cha with a trans-1,4 structure, and synthetic isoprene rubber has a cis-1,4 bond structure. 1,4-inbre rubber, trans-1
, 4-isoprene rubber, 3.4-isoprene rubber, 1.
2-There is isoprene rubber.

Depolymerized isoprene rubber is isoprene rubber that is obtained by subjecting natural rubber or synthetic isoprene rubber to treatments such as heat, light, and chemical reactions, and is in a liquid or semisolid state at room temperature. Specifically, These include depolymerized natural rubber and depolymerized synthetic isoprene rubber.

Cyclized polyisoprene is obtained by subjecting natural rubber or synthetic isoprene rubber to a Friedel-Krach reaction.

That is, cyclized polyisoprene can be obtained by reacting natural rubber or synthetic isoprene rubber with a strong acid, or by performing a cyclization reaction using R502X or a Lewis acid.

Furthermore, the isoprene-based copolymer refers to a copolymer in which 1 fi of the raw material monomers during copolymer production is isoprene. Examples of other raw material monomers copolymerized with isoprene include diene monomers such as butadiene, styrene, and acrylonitrile. Note that the copolymer is not limited to a binary copolymer.

Specific examples of isoprene-based copolymers include isoprene-based copolymers.
Styrene copolymer, isoprene-butadiene copolymer,
Examples include isoprene-butadiene-styrene copolymer, isoprene-butadiene-acrylonitrile copolymer, and styrene-isoprene-styrene block copolymer.

Isoprene rubber having one or more polar functional groups in the molecule refers to one or more carboxyl groups, hydroxyl groups,
These are natural rubber, synthetic isoprene rubber, and isoprene-based copolymers that have functional groups such as epoxy groups and amino groups.

The above is the isoprene rubber that is the raw material for the oxidized modified isoprene rubber (B), but in addition, those obtained by partially hydrogenating the double bonds of the above compounds can also be used. However, the more double bonds there are, the more suitable it is for producing the oxidized isoprene-based rubber (B).

Further, as a raw material for the oxidized isoprene-based rubber (B), an isoprene-based rubber with a high isoprene content is preferable, and one with an isoprene content of 50% by weight or more is preferable.

The isoprene rubber may be liquid or solid at room temperature.

A preferred method for producing the oxidized isoprene-based rubber (B) is to dissolve one or more of the isoprene-based rubbers in a hydrocarbon-based organic solvent, and then irradiate the solution with sunlight or ultraviolet rays in the presence of oxygen. This is a method in which the oxidized and modified isoprene-based rubber (B) is obtained as an excess precipitate by irradiating the rubber for a certain period of time.

Incidentally, after separating the precipitate from the solvent, it is preferable to perform vacuum drying. Further, to the mixture of the raw isoprene rubber and the solvent, an oxidation catalyst, an oxidation catalyst, an oxidation aid, and a photosensitizer may be added. Furthermore, if necessary, purification may be carried out by dissolving this isoprene-based rubber oxidation-modified product (B) in chloroform, etc., and pouring it into a hydrocarbon-based organic solvent such as hexane, cyclohexane, toluene, etc. for reprecipitation. good.

By the way, the isoprene-based rubber oxidized modified product (B) used in the present invention is characterized by an infrared absorption spectrum of 3400
It has characteristic absorption near cm-' and 1720 cm-', and has an absorption peak in the range of 0 to 120 °C in differential scanning calorimeter (DSC), but it has characteristic absorption near 3400 cm-' in the infrared absorption spectrum. The characteristic absorption near 1720 cm-'' is said to be caused by hydroperoxide groups and carbonyl groups, which are generated in the molecules of the raw isoprene rubber by light irradiation, respectively, and this is due to the vulcanization rate and vulcanization of the rubber composition. It is a factor that affects rubber hardness.

Further, an absorption peak in the range of 0 to 120°C in a differential scanning calorimeter means that this oxidized modified product has a melting point (softening point) of 0°C or higher.

Furthermore, this oxidized isoprene-based rubber (B) is characterized in that it is insoluble in hexane.

The isoprene-based rubber oxidized modified product (B) used in the present invention is
As mentioned above, it is obtained by irradiating isoprene rubber with ultraviolet rays, electron beams, visible light, etc. in a solvent-dissolved state, and usually has a Mw of 3,000 to so, ooo,
low. Therefore, it should normally be liquid and should be soluble in hydrocarbon organic solvents such as hexane. However, the reason why it is insoluble in hexane is that the isoprene rubber oxidized modified product (B) has hydroperoxide groups and carbonyl groups, and also because the molecular weight has decreased to a certain range. Alternatively, it is presumed that an isomerization reaction occurred and the substance became insoluble in hexane. Furthermore, the fact that cyclized polyisoprene itself is insoluble in hexane among the isoprene rubbers that are the raw materials for the oxidatively modified isoprene rubber product (B) used in the present invention makes it difficult for cyclization or isomerization reactions to occur. This is supported.

In addition, the isoprene-based rubber oxidized modified product (B
) shows good solubility in organic solvents such as chloroform. However, when the isoprene content decreases, the solubility in chloroform etc. decreases.

In the present invention, since the unvulcanized rubber composition has a high softening effect, the oxidized modified isoprene rubber composition (B
) is preferably soluble in chloroform, that is, one with a high isoprene content.

Furthermore, in the present invention, isoprene-based rubber oxidized modified product (B
), those derived from isoprene-based copolymers,
Alternatively, it is preferable to use one derived from isoprene rubber having one or more polar functional groups in the molecule.

The rubber composition of the present invention is characterized in that the above-mentioned isoprene-based rubber oxidized modified product (B) is combined with one selected from natural rubber and synthetic rubber.
0.5 to 50 per 100 parts by weight of rubber (A)
It contains 0.5 to 30 parts by weight, preferably 0.5 to 30 parts by weight. If the isoprene rubber oxidized modified product (B) is less than 0.5 parts by weight, there is no effect when added, and if it exceeds 50 parts by weight, the tensile strength of the rubber composition after vulcanization decreases, which is not preferable.

In addition to the above-mentioned essential components, the rubber composition of the present invention may include carbon black, silica,
Reinforcing agents and fillers such as calcium carbonate and phenolic resin,
Contains compounding agents commonly used in the rubber industry, such as aroma oil, petroleum resin, rosin, softeners such as liquid rubber, vulcanizing agents such as sulfur, vulcanization accelerators, vulcanization accelerators, anti-aging agents, etc. You may do so.

The rubber composition of the present invention may be kneaded by any known method, but the temperature at that time is preferably 145°C or lower, preferably 135°C.
The following are more preferred.

The rubber composition of the present invention having the above structure can be applied to tires in general, conveyor belts, hoses, anti-vibration rubber, etc.

<Examples> The present invention will be explained in more detail by Examples below, but the present invention is not limited to these Examples.

First, the production of the oxidized isoprene-based rubber (B) will be described.

Isoprene-based rubber oxidized modified products (B) were obtained by the following method (Production Examples 1 to 11), and I
R analysis, DSC analysis, GPC analysis, and solubility test were conducted. The results are shown in Table 1 and FIGS. 1 and 2.

(Production Example 1) 100 g of NR (SMR-L) was heated at 50 ± 10°C,
It was passed through a roll adjusted to 0 mm 10 times.

This rolled rubber 6, Og was placed in a transparent glass container that allows light to pass through and has an air inlet, and then 144 g of n-hexane was added to make a homogeneous solution (rubber concentration 4%), and a colorless film was formed. The tube was sealed with water, and sunlight was irradiated while keeping the temperature of the rubber solution at 45° C. or lower.

After 60 hours of irradiation, a precipitate was obtained, and the solvent portion was removed and vacuum dried to obtain 5.5 g of a pale yellow solid (sample A).

(Production Example 2) Commercially available synthetic isoprene rubber N1polIR as a raw material
-2200 (manufactured by Nippon Zeon ■) was used without being rolled.

Put 10 g of N1pol IR-2200 into a transparent glass container that allows light to pass through and has an air inlet, then add 190 g of n-hexane to make a homogeneous solution (rubber concentration 5
%), sealed with a colorless film, and irradiated with sunlight while keeping the rubber solution temperature below 45°C. A precipitate was obtained after 150 hours of irradiation, so the solvent part was removed, the remaining precipitate was dissolved in chloroform, and 325
It was purified by passing through a cloth mesh and pouring into n-hexane to cause reprecipitation, and vacuum drying to obtain 9.3 g of white powder (sample B).

(Production Example 3) Commercially available depolymerized synthetic isoprene rubber l5ol as a raw material
Precipitation was carried out in the same manner as in Production Example 2, except that 0 g of l5olene 04005 was dissolved in 195 g of n-hexane (rubber concentration 2.5%) and the irradiation time was 73 hours. When the product was obtained and purified, a white powder (sample C) was obtained.3.
1 g was obtained.

(Manufacturing Example 4) Pre-made n-
800 g of hexane, 94.5 g of isoprene, and 5.5 g of 1,3-butadiene were charged and maintained at 60°C. 0.5 moIl of n-butyllithium as a polymerization catalyst was added, and the mixture was reacted for 60 minutes with stirring. Methanol was added to stop the reaction, and 0.7 g of 2,6-di-t-butylhydroxytoluene was added thereto to form isoprene solid at room temperature.
100 g of 3-butadiene copolymer was obtained. GP mentioned below
C analysis revealed that the molecular weight was 320,000.

3.0 g of this synthesized isoprene/1,3-butadiene copolymer was dissolved in 147 g of n-hexane (rubber concentration 2
．． 0%) and the irradiation time was 60 hours, a precipitate was obtained in the same manner as in Production Example 2, purified and dried, and 2.3 g of a pale yellow solid (sample D) was obtained.

(Production Example 5) Using commercially available liquid isoprene-butadiene copolymer LIR-340 (manufactured by Kuraray) as a raw material, LIR-340
Dissolve 103 in 190g of n-hexane (rubber concentration 5%)
However, a precipitate was obtained in the same manner as in Production Example 2, except that the irradiation time was 150 hours, and when it was purified and dried, 6.3 g of white powder (sample E) was obtained.

(Production Example 6) Commercially available isoprene-styrene-isoprene block copolymer Kraton D 1107 (She
(manufactured by Chemica 1), and the irradiation time was 89
A precipitate was obtained in the same manner as Production Example 2 except for the time,
After purification and drying, a pale yellow solid (sample F)2.
4g was obtained.

(Production Example 7) Commercially available liquid isoprene-styrene copolymer L as a raw material
Using IR-310 (Kuraray), LIR-3101
0g was dissolved in 140g of fi-hexane (rubber concentration 6.
7%) and the irradiation time was 110 hours, a precipitate was obtained in the same manner as in Production Example 2, purified and dried, and 6.1 g of a pale yellow solid (sample G) was obtained.

(Production Example 8) Using commercially available carboxyl group-containing liquid polyisoprene LIR-403 (manufactured by Kuraray) as a raw material, LIR-40
Dissolve 33.0g in 147g of n-hexane (rubber concentration 2
．． A precipitate was obtained in the same manner as in Production Example 2, except that the irradiation time was 65 hours, purified, and dried to yield 2.3 g of a pale yellow solid (Sample H).

(Production Example 9) Commercially available hydroxyl group-containing liquid polyisoprene LIR as a raw material
-503 (manufactured by Kuraray), LIR-5036,0
Dissolve g in 194 g of n-hexane (rubber concentration 3%),
A precipitate was obtained in the same manner as in Production Example 2, except that the irradiation time was 54 hours, and when it was purified and dried, 5.8 g of white powder (Sample I) was obtained.

(Production Example 10) A mixture of LIR-403 and LrR-503 (
A precipitate was obtained in the same manner as in Production Example 2, except that 5 g of 1:1) was used, dissolved in 195 g of n-hexane (rubber concentration 25%), and the irradiation time was 85 hours, purified and dried. However, 4.5 g of white powder (sample J) was obtained.

(Production Example 11) The reaction cell and irradiation device are shown in FIG. 3. 0 g of LIR-3103 used in Production Example 7 was placed in a glass cell 1, 147 g of n-hexane was added, and the rubber concentration was 2.0 g. A 0% solution was prepared. Next, the ultraviolet hard north irradiator type U
Ultraviolet rays were irradiated using EOI 1-203 (manufactured by Eye Graphics).

The cell 1 was equipped with a quartz lid 5 and a reflux condenser 2 to prevent the solvent from volatilizing from the system, and to keep the solution in contact with air to maintain a constant oxygen concentration.

A metal halide lamp was used as the irradiation light source 3, and the light source 3 and a quartz M5 were arranged in parallel with a distance of 60 cm so that the amount of light incident on the reaction solution was constant.

In addition, the cell 1
was placed in water bath 6.

A precipitate was obtained after 45 hours of irradiation, so the solvent part was discarded, the remaining precipitate was dissolved in chloroform, and 325 me
It was purified by passing it through a sh net and pouring it into n-hexane to reprecipitate it, and vacuum drying it to give a pale yellow powder (
2.5 g of sample K) was obtained.

(Test Method) IR Analysis Measurement was performed using a PerkinElmer Model 983G infrared spectrophotometer using the KBr method.

■DSC analysis Measurement was carried out using Du Pont's 1090BT at a heating rate of 10° C./min.

■GPC analysis Waters 150-CAL C7
Mw was determined by gel permeation chromatography using 0PC. The calibration curve was created using standard polystyrene manufactured by Pressure Chemical Company.

The solvent is tetrahydrofuran, and the separation column is Ultra Styla Gel 105 10' 1 manufactured by Waters.
0' 500A was used.

■ Solubility test in solvents Dissolve 0.2 g of oxidized isoprene rubber in 10 mj2 of hexane or chloroform at room temperature. Visually check that no precipitate is seen as soluble, and that where precipitate is seen as insoluble. did.

(Example) A rubber composition was prepared by weighing raw rubber and various compounding agents so as to have the composition shown in Table 2, and kneading them using a Banbury mixer or a roll. Regarding the rubber compositions containing the above, kneading was carried out at 120° C. or below, since if the kneading temperature is high, a vulcanization reaction will start during kneading and the viscosity of the rubber composition will tend to increase.

For these rubber compositions, the viscosity before vulcanization, the vulcanization rate, and the hardness after vulcanization were measured.

The results are shown in Table 2.

(Test method) ■ Viscosity of unvulcanized rubber Mooney viscosity (ML
I-4, 100°C) was measured.

■Vulcanization speed For unvulcanized rubber compositions, NR rubber compositions were tested at a temperature of 15
0℃, SBR rubber composition temperature 160℃, ARC±3°
T9a was measured under the following conditions.

■Hardness after vulcanization
The SBR rubber composition was vulcanized at 160°C for 20 minutes,
Molded into a rubber sheet. The hardness (according to type A) of these rubbers was measured according to JIS K 6301 using a sheet.

Table 1 shows the physical properties and characteristics of the oxidized isoprene-based rubbers (samples AK) obtained based on the production examples (see also FIGS. 1 and 2).

Sample A- has characteristic absorption near 3400 cm-'' and 17200 m-'' in the infrared absorption spectrum, and an absorption peak in the range of 0 to 120°C in the differential scanning calorimeter. It is characterized by being insoluble.

Table 2 shows the rubber compositions of the present invention (Invention Examples 1 to 16) containing the oxidized modified isoprene rubber, and their unvulcanized viscosity, vulcanization rate, and post-vulcanized hardness. It is something that For comparison, examples in which no softener was blended (Comparative Examples 1 and 6) and examples in which a conventional softener was blended (Comparative Examples 2 to 5 and Comparative Examples 7 and 8) are shown.

As is clear from Table 2, among conventional softeners, petroleum-based softeners, petroleum resins, and liquid rubbers lower the viscosity of unvulcanized rubber compositions and at the same time lower the hardness of vulcanized rubber. It ends up. In addition, gum rosin lowers the viscosity of the rubber composition when it is unvulcanized and does not affect the hardness after vulcanization.
This will significantly slow down the vulcanization rate. On the other hand, the rubber composition of the present invention has a low viscosity when unvulcanized, but a high hardness after vulcanization, and is excellent in physical properties. And the vulcanization rate is within normal range.

<Effects of the Invention> As explained above, the rubber composition of the present invention has a viscosity when unvulcanized that is as low as that of rubber compositions containing conventional softeners such as process oil. -Still,
The hardness after vulcanization is equal to or higher than that without a softener.

Therefore, the rubber composition of the present invention is extremely useful in the rubber industry.

[Brief explanation of drawings]

FIG. 1 is a graph showing the infrared absorption spectra of samples A, C, D1G, and H. FIG. 2 is a graph showing the results of measuring samples A, C, D, G, and H using a differential scanning calorimeter. FIG. 3 is a diagram showing an example of an apparatus for producing an oxidized and modified isoprene-based rubber. Explanation of symbols 1... Cell, 2... Reflux condenser, 3... Light source, 5... Quartz lid, 6... Water bath FIG, 2 (''C) FIG, 1 (cm- ')

Claims (4)

[Claims] (1) One or more rubbers (A) selected from natural rubber and synthetic rubber, and 3400c in infrared absorption spectrum.
Oxidized modified isoprene rubber (B) that has characteristic absorption near m^-^1 and around 1720 cm^-^1, and has an absorption peak in the range of 0 to 120 °C in differential scanning calorimeter.
The content of the isoprene-based rubber acid-modified product (B) is 0.5 to 50 parts by weight based on 100 parts by weight of the rubber (A).
A rubber composition characterized in that parts by weight. (2) The rubber composition according to claim 1, wherein the oxidized isoprene-based rubber (B) is soluble in chloroform. (3) The rubber according to claim 1 or 2, wherein the oxidized isoprene-based rubber (B) is a modified product derived from an isoprene-based copolymer produced using isoprene as one type of raw material monomer. Composition. (4) The rubber according to any one of claims 1 to 3, wherein the oxidatively modified isoprene rubber (B) is a modified product derived from an isoprene rubber having one or more polar functional groups in the molecule. Composition.