JPH03223311A - Oxidatively modified isoprene rubber and its production - Google Patents

Abstract

PURPOSE:To obtain an oxidatively modified isoprene rubber which, when added to a rubber composition, can exhibit an effect of softening it before vulcanization and can increase the hardness of a vulcanized rubber article by dissolving an isoprene copolymer in a hydrocarbon organic solvent and irradiating the solution with sunlight or ultraviolet rays in the presence of oxygen. CONSTITUTION:At least one member selected from among an isoprene rubber having at least one polar functional group in the molecule, a cyclized polyisoprene and an isoprene copolymer produced from a starting monomer comprising isoprene is dissolved in a hydrocarbon organic solvent, and the solution is irradiated with sunlight or ultraviolet rays in the presence of oxygen to obtain an oxidatively modified isoprene rubber having characteristic absorptions near 3400cm<-1> and 1720cm<-1> in an infrared absorption spectrum and absorption bands in a temperature range of 0-120 deg.C in differential scanning calorimetry. When this product is added to a rubber composition as a softener, there is an advantage that the viscosity before vulcanization is as low as that attained when the conventional softener such as a process oil is used, and besides, the hardness after vulcanization is equivalent to or higher than that attained when no softener is added.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a novel oxidized and modified isoprene-based rubber and a method for producing the same. More specifically, the present invention relates to a novel oxidized isoprene-based rubber material suitable as a raw material for rubber products and a method for producing the same.

<Prior art> In the field of manufacturing rubber products, various softeners have traditionally been added to unvulcanized rubber compositions to improve workability and processability during molding and cross-contamination of unvulcanized rubber compositions. are doing. Examples of softeners that are used include process oils, petroleum resins, petroleum-based softeners such as coumaron/indene resin, and vegetable oil-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 exhibit a softening effect on unvulcanized rubber compositions equivalent to that of process oils and do not reduce 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 aims to solve the above-mentioned problems in rubber softeners.
This is a new isoprene-based rubber oxidation-modified product that, when added to a rubber composition, exhibits a softening effect equivalent to that of process oil etc. when unvulcanized, and increases the hardness of vulcanized rubber products, and a method for producing the same. For the purpose of providing.

<Means for Solving the Problems> The present invention provides a rubber composition that is manufactured using isoprene rubber having one or more polar functional groups in the molecule, depolymerized isoprene rubber, cyclized polyisoprene, and isoprene as one type of raw material monomer. It is a modified product derived from one or more types of isoprene-based copolymers, and has characteristic absorption in the vicinity of 3400 cm-' and 1720 cm-' in the infrared absorption spectrum, and has a characteristic absorption of 0 to 1720 cm-' in the differential scanning calorimeter. The present invention provides an oxidized modified isoprene rubber characterized by having an absorption band in the range of 120°C.

The present invention also provides isoprene rubber having one or more polar functional groups in the molecule, depolymerized isoprene rubber, cyclized polyisoprene, and isoprene copolymer produced using isoprene as a raw material. An oxidized and modified isoprene rubber product, which is produced by dissolving one or more of the combined compounds in a hydrocarbon organic solvent and irradiating it with sunlight or ultraviolet rays in the presence of oxygen. The present invention provides a method for manufacturing.

The present invention will be explained in detail below.

A first aspect of the present invention is to provide a novel oxidized and modified isoprene-based rubber.

The novel oxidized isoprene-based rubber of the present invention is made from one or more of isoprene rubber having one or more polar functional groups in the molecule, depolymerized isoprene rubber, cyclized polyisoprene, and isoprene-based copolymer. It is a modified product that is induced.

First, the isoprene mixture that is the raw material for the oxidized modified isoprene rubber of the present invention will be explained.

In the present invention, isoprene rubber having one or more polar functional groups in the molecule refers to natural rubber having one or more functional groups such as carboxyl, hydroxyl, epoxy, or amino groups in the molecule, and natural trans- Polyisoprene, synthetic isoprene rubber (cis-1,4-isoprene rubber, trans-1,4-isoprene rubber, 3,4-isoprene rubber,
liquid polyisoprene).

Depolymerized isoprene rubber is natural rubber, natural trans-
Isoprene rubber that is liquid or semi-solid at room temperature and is obtained by treating polyisoprene or synthetic isoprene rubber with heat, light, chemical reactions, etc. Specifically, depolymerized natural rubber, depolymerized natural rubber, etc. Synthetic isoprene rubber, etc.

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

That is, by reacting natural rubber, natural trans-polyisoprene or synthetic isoprene rubber with a strong acid, or by reacting R3
A cyclized polyisoprene is obtained by carrying out a cyclization reaction using O□X or a Lewis acid.

Furthermore, an isoprene-based copolymer is a copolymer in which one of the raw material monomers during copolymer production is isoprene, and a copolymer in which a polar functional group is introduced into the molecule.
An isoprene-based copolymer having one or more polar functional groups.

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,
Isoprene/butadiene/styrene copolymer, isoprene/butadiene/acrylonitrile copolymer, styrene/isoprene/styrene block copolymer, etc., and these copolymers contain carboxyl groups, hydroxyl groups, epoxy groups,
Examples include those into which polar functional groups such as amino groups are introduced.

The above are the isoprene compounds that serve as raw materials for the oxidized modified isoprene rubber of the present invention, but in addition, compounds 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 an oxidized and modified isoprene-based rubber.

In addition, as a raw material for the oxidatively modified isoprene rubber of the present invention, a compound with a high isoprene content is preferable, with 50%
It is preferable that the amount is % by weight or more.

The isoprene compound that is the raw material for the oxidatively modified isoprene rubber of the present invention may be liquid or solid at room temperature.

The oxidized and modified isoprene-based rubber of the present invention is a modified product derived from one or more of the above-mentioned raw material isoprene-based compounds, and has a polar functional group with one or more of the above-mentioned raw material isoprene-based compounds. Isoprene homopolymer (N
Modified products mixed with RlIR) are also included in the oxidized modified isoprene rubber products of the present invention.

The oxidatively modified isoprene rubber of the present invention is one or more of isoprene rubber having one or more polar functional groups in the molecule, depolymerized isoprene rubber, cyclized polyisoprene, and isoprene copolymer, or A mixture of isoprene and isoprene homopolymer is modified by undergoing an oxidation reaction when dissolved in a solvent, but the oxidation reaction occurs in the presence of oxygen.
This is done through the involvement of energy such as heat, ultraviolet rays, electron beams, and visible light.

The characteristics of the oxidized isoprene-based rubber of the present invention are that the infrared absorption spectrum is around 3400 cm-' and 1720 cm-'.
It has a characteristic absorption in the vicinity of cm-' and can be detected by differential scanning calorimetry (DS
C) has an absorption band in the range of 0 to 120°C, and in the infrared absorption spectrum, it has an absorption band of 3400 cm-'
It has a large characteristic absorption near 3400 cm-' and 1720 cm-' in the infrared absorption spectrum.
The characteristic absorption around 20 cm-' is said to be caused by hydroperoxide groups and carbonyl groups, respectively, which are generated within the molecule of the raw material isoprene compound by light irradiation (for example, Rubber Chem, Tecnol,
50, 705.1977) In a differential scanning calorimeter, it has an absorption band in the range of 0 to 120°C, which means that this oxidized modified product has a melting point (softening point) above 0°C. are doing.

Furthermore, this oxidized isoprene rubber is characterized by being insoluble in hexane. Furthermore, it shows good solubility in organic solvents such as chloroform, but as the isoprene content decreases, solubility in chloroform and the like decreases.

It is known that during decomposition, the molecular weight decreases due to irradiation with sunlight or ultraviolet rays. The isoprene-based rubber oxidized modified product of the present invention also has ultraviolet rays, electron beams,
Obtained by irradiation with visible light, etc., and usually has a Mw of 3,00
0 to 50,000, which is 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 isoprene-based rubber oxidized modified products have hydroperoxide groups and carbonyl groups, and the molecular weight has decreased to a certain range, so it is difficult to cyclize or isomerize. It is assumed that a reaction occurred and the product became insoluble in hexane. Furthermore, the fact that cyclized polyisoprene itself is insoluble in hexane among the isoprene compounds that are the raw materials for the oxidized modified isoprene rubber of the present invention supports that a cyclization or isomerization reaction has occurred. be done.

A second aspect of the present invention is to provide a suitable method for producing an oxidized modified isoprene rubber having the characteristics shown in the first aspect.

Specifically, the raw material isoprene compound is dissolved in a hydrocarbon organic solvent and irradiated with sunlight or ultraviolet rays in the presence of oxygen to obtain an oxidized and modified isoprene rubber, usually as a precipitate.

Here, the isoprene compound which is the raw material for producing the oxidized modified isoprene rubber is an isoprene rubber having one or more polar functional groups in the molecule, as exemplified in the explanation of the first aspect of the present invention. One type of isoprene-based copolymer produced using depolymerized isoprene rubber, cyclized polyisoprene, and isoprene as one type of raw material monomer,
Alternatively, it is a mixture of two or more types.

Alternatively, it is a mixture of these raw material isoprene compounds and an isoprene homopolymer.

Further, the solvent for dissolving the raw material isoprene compound may be any hydrocarbon-based solvent that dissolves the compound, and specific examples thereof include hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, Hydrocarbon organic solvents such as ethylbenzene,
Examples include rubber volatile oils containing these as main components, and mixtures thereof.

Among these, aliphatic hydrocarbons such as hexane, alicyclic hydrocarbons such as cyclohexane, etc. Particularly preferred are hydrocarbon-based organic solvents such as rubber volatile oils mainly composed of , aliphatic and alicyclic hydrocarbons, and mixtures thereof. However, as mentioned above,
Since cyclized polyisoprene does not dissolve in hexane, aromatic hydrocarbons such as toluene are preferred when cyclized polyisoprene is used as a raw material. When these hydrocarbon organic solvents are used, an oxidized and modified isoprene rubber is obtained as a precipitate.

Note that it is the concentration of the raw material isoprene compound in the solution (%).

In order to accelerate the modification reaction of the raw material isoprene compound, the raw material isoprene compound or the mixture of the compound and the solvent is treated with a chemical such as a chemical made of an inorganic or organic compound, such as metal soap, specifically naphthene. It is preferable to add metal salts of cyclic fatty acids such as acids and chain fatty acids such as 2-ethylhexylic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid. Examples of metal salts of metal soap include Co, Mn, Mg, Aj2. C
u, Ca, Zn.

Examples include Ti, Fe, Ni, Sn, Zr, and Pb.

Furthermore, ManobondC-16, Manobon
An oxidation catalyst such as an organic acid cobalt-boric acid soap known under a trade name such as dCP-420 or an oxidation aid may be added. Further, a photosensitizer such as benzophenone or acetophenone may be added.

In the second aspect of the present invention, the oxidized and modified isoprene-based rubber of the present invention is obtained by irradiating oxygen to the solution of the raw material isoprene-based compound thus prepared.

In the case of non-irradiation, the raw material isoprene compound is dissolved in the solvent, but as the irradiation progresses, the viscosity of the solution decreases, and eventually a polymer (oxidized modified isoprene rubber) that does not dissolve in the solvent is formed and precipitates. and settle to the bottom of the container.

By removing the solvent portion, the precipitated polymer, that is, the desired oxidized isoprene-based rubber is obtained.

If necessary, the oxidized and modified isoprene rubber can be dissolved in chloroform, etc., and poured into a hydrocarbon organic solvent such as hexane, cyclohexane, toluene, etc. to reprecipitate the oxidized and modified isoprene rubber. Can be purified. Further, in order to prevent deterioration of the oxidized isoprene-based rubber, it is preferable to add a stabilizer such as 2.6 to di-t-butylhydroxytoluene.

When the isoprene-based rubber oxidized modified product of the present invention is used as a compounding agent for rubber, it is preferably purified as described above and then vacuum-dried before use.

There are no particular restrictions on the concentration of oxygen required for light irradiation (
, just exists. Therefore, not only under pure oxygen,
The reaction may be carried out in air or in a mixed atmosphere of oxygen and other inert gas.

The irradiation time of sunlight or ultraviolet rays varies depending on the type of isoprene compound that is the raw material, the degree of polymerization, the concentration of the isoprene compound in the solution, the amount of solution, the intensity of light, the shape of the container, etc. Although it cannot be determined, it is sufficient to carry out the process until the precipitated and dispersed oxidized isoprene-based rubber is precipitated. Preferably, if the irradiation is continued for a while even after precipitation begins, a large amount of the desired modified product can be obtained.

The temperature of the solution during irradiation should be as low as possible in order to obtain a uniform amount of oxidized isoprene-based rubber (usually below 90°C, preferably below 60°C. The temperature of the solution must be above the freezing point of the solvent for one reaction to proceed.

When added to a rubber composition as a compounding agent, the isoprene-based rubber oxidized modified product of the present invention described above lowers the viscosity of the rubber composition when unvulcanized, acts as a softener, and at the same time acts as a softener after vulcanization. It also shows the effect of increasing the hardness of rubber products.

In this case, the raw material rubber for the rubber composition includes natural rubber, polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, ethylene-propylene copolymer rubber, isoprene-isobutylene copolymer rubber, chloro Blend rubber can be exemplified, and these can be used alone or in a blend. Furthermore, in addition to the raw material rubber and the oxidized isoprene-based rubber of the present invention, carbon black, zinc white, an anti-aging agent, sulfur, a vulcanization accelerator, etc. may be added to the rubber composition as necessary. can. The amount of the isoprene mulberry rubber acid modified product of the present invention added to the rubber composition is as follows: raw material rubber 1
0.5 to 50 parts by weight is appropriate.

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

[Example 1] Isoprene-based rubber oxidized modified products were obtained by the following method (Invention Examples 1 to 14), and IR analysis, DSC analysis, GPC analysis, and solubility test were conducted on them using the methods described below.
The results are shown in Table 1 and FIGS. 1, 2, 3, and 4.

(Example 1 of the present invention) Yong! 800 g of purified n-hexane, 94.5 g of isoprene, and 5.5 g of 1,3-butadiene were placed in a 3β stainless steel autoclave and maintained at 60°C. 0.5 moβ 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 obtain 00 g of isoprene arch and 3-butadiene copolymer i which was solid at room temperature. When the GPC analysis described below was performed, the molecular weight was 320,000.

3.0 g of the synthesized isoprene/1,3-butadiene copolymer was placed in a transparent glass container that allows light to pass through and has an air intake, and then 147 g of n-hexane was added to form a homogeneous solution (isoprene/1,3-butadiene copolymer). 3-butadiene copolymer concentration of 2%), sealed with a colorless film, and exposed to sunlight. A precipitate was obtained after 60 hours of irradiation, so the solvent portion was removed, the remaining precipitate was dissolved in chloroform, passed through a 325 mesh net, poured into n-hexane, and reprecipitated to purify it, and purified in a vacuum. When dried, 2.3 g of pale yellow solid (sample A)
was gotten.

(Example 2 of the present invention) Using a commercially available liquid isoprene-butadiene copolymer LIR-340 (■ manufactured by Kuraray) as a raw material, LIR-340
log was dissolved in 190 g of n-hexane (liquid isoprene-butadiene copolymer concentration 5%), and the irradiation time was 150 g.
A precipitate was obtained in the same manner as in Inventive Example 1 except for the time, and when purified and dried, a white powder (Sample B) 6
．． 3g was obtained.

(Example 3 of the present invention) Commercially available liquid isoprene-styrene copolymer L as a raw material
Using IR-310 (■Kuraray), LIR-3105
,0g to n-hexane/toluene (80:20, weight)
A precipitate was obtained in the same manner as in Inventive Example 1, except that it was dissolved in 145 g of a mixed solvent (liquid isoprene-styrene copolymer concentration 3.3%), and the irradiation time was 90 hours, purified and dried. 4.2 g of pale yellow powder (sample C) was obtained.

(Example 4 of the present invention) 10 g of LIR-310 was dissolved in 140 g of n-hexane (liquid isoprene-styrene copolymer concentration 6.7%).
), and the irradiation time was 110 hours, except that the present invention example 3
A precipitate was obtained in the same manner as above, purified and dried to obtain 6.1 g of a pale yellow solid (sample D).

(Example 5 of the present invention) Commercially available Kraton D 1107 (S
Hell Chemical Co., Ltd.) was used, and the irradiation time was 89 hours, but the precipitate was obtained in the same manner as in Inventive Example 1, purified and dried, and 2.4 g of a pale yellow solid (Sample E) was obtained. Ta.

(Example 6 of the present invention) Using n-hexane instead of the n-hexane/toluene mixed solvent, cobalt naphthenate (Co content 1
A precipitate was obtained in the same manner as in Invention Example 3, except that 0.1 g of 0.0% (manufactured by Nippon Kagaku Sangyo ■) was added and the irradiation time was 80 hours.A precipitate was obtained in the same manner as in Invention Example 3, purified, and heated to rJ9, resulting in a reddish brown solid (sample F) 4.1 g was obtained.

(Example 7 of the present invention) Figure 5 shows the reaction cell and irradiation device. 0 g of LIR-3103 used in Example 3 of the present invention was placed in a glass cell 1, 147 g of n-hexane was added, and liquid isoprene was added. A solution having a styrene copolymer concentration of 2.0% was prepared. Subsequently, ultraviolet rays were irradiated using an ultraviolet curing irradiator type UEOII-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 lid 5 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 91 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 (
Sample G) 2.5 g was obtained.

(Example 8 of the present invention) Commercially available carboxyl group-containing liquid isoprene LIR-403 (manufactured by Kuraray) was used as a raw material.

0 g of IjR-4033 was placed in a transparent glass container that allows light to pass through and has an air inlet, and then 147 g of n-hexane was added to make a homogeneous solution (carboxyl group-containing liquid polyisoprene concentration 2%), and a colorless film was formed. The container was sealed with water, and sunlight was irradiated while adjusting the temperature of the solution to 45° C. or lower. A precipitate was obtained after 65 hours of irradiation, so the solvent portion was removed, the remaining precipitate was dissolved in chloroform, passed through a 325 mesh net, poured into n-hexane, and purified by reprecipitation. Upon drying, 2.3 g of a pale yellow solid (Sample H) was obtained.

(Example 9 of the present invention) Commercially available hydroxyl group-containing liquid polyisoprene LIR as a raw material
-503 (manufactured by Kuraray), LIR-5036,0
A precipitate was obtained in the same manner as in Inventive Example 8, except that g was dissolved in 194 g of xane (hydroxyl group-containing liquid polyisoprene concentration: 3%) and the irradiation time was 54 hours, purified and dried. , white powder (Sample I) 5.8
g was obtained.

(Example 10 of the present invention) A mixture of LIR-403 and LIR-503 (
1: A precipitate was obtained in the same manner as in Inventive Example 8, except that 5 g of 1) was used, dissolved in 195 g of n-hexane (rubber mixture concentration 2.5%), and the irradiation time was 85 hours.
After purification and drying, a white powder (sample J) was obtained.4.
5g was obtained.

(Example 11 of the present invention) 100 g of NR (SMR-5L) was passed through a roll adjusted to 50° C.±10° C. and a gap of 1.0 mm 10 times. 7.0g of this rubber was tested in a gear type aging tester (JIs K
6301 compliant) at 120°C for 72 hours,
A depolymerized rubber that is semi-liquid at room temperature was obtained.

Using this depolymerized rubber as a raw material, this depolymerized rubber6.
Dissolve 0g in 144g of n-hexane (depolymerized rubber concentration 4
．． 0%) and the irradiation time was 29 hours, but the same method as in Inventive Example 8 was used to obtain a precipitate, purification, and drying.
5.8 g of white powder (sample K) was obtained.

(Example 12 of the present invention) Commercially available depolymerized synthetic isoprene rubber l5ol as a raw material
Using ene D400 (manufactured by Hardman),
l5olene D4005, 0 g dissolved in 195 g of n-hexane (depolymerized synthetic isoprene rubber concentration 2.5
%) and the irradiation time was 73 hours.
A precipitate was obtained in the same manner as above, purified and dried to obtain 3.1 g of white powder (sample L).

(Example 13 of the present invention) Commercially available cyclized polyisoprene Thermolyte P as a raw material
(manufactured by Seiko Kagaku Co., Ltd.) using Thermolite P5. Dissolve Og in 195g of toluene (cyclized polyisoprene concentration 2.5
%) and the irradiation time was 45 hours.
A precipitate was obtained in the same manner as above, purified and dried to obtain 0.5 g of an off-white powder (sample M).

(Example 14 of the present invention) A precipitate was obtained in the same manner as Example 7 of the present invention, except that LIR-503 was used instead of LIR-310 as the raw material, and the irradiation time was changed to 45 hours. When the precipitate was purified and dried, a pale 2.5 g of yellow powder (sample N) was obtained.

(Test Method) ■ Engineering R Analysis Measurement was carried out by the KBr tablet method using a 983 G-type infrared spectrophotometer manufactured by PerkinElmer.

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

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

The solvent was tetrahydrofuran, and the separation column was Ultra Styla Gel 10', 10', 1 manufactured by Waters.
03,500 people were used.

■ Solubility test in solvent Dissolve 0.2 g of oxidized isoprene rubber in 10 mI2 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 2] Regarding the rubber compositions having the formulation shown in Table 2, the viscosity before vulcanization, the vulcanization rate, and the hardness after vulcanization were measured by the following methods. The results are shown in Table 2.

(Test method) ■ Viscosity of unvulcanized rubber The raw materials were kneaded using a Banbury mixer, and the resulting rubber composition was tested using a Mooney tester manufactured by Toyo Seiki Co., Ltd.
Mooney viscosity (ML) according to JIS K 6300
, 100°C) were measured.

■Vulcanization speed For unvulcanized rubber compositions, the temperature was 150℃, ARC±3 using a rheometer TP-100 manufactured by Mon5anto.
T96 was measured under the conditions of .

(2) Hardness after vulcanization The unvulcanized rubber composition was vulcanized at 150° C. for 30 minutes and molded into a rubber sheet. Using these rubber sheets, the hardness (by type A) was measured according to JIS 6301.

Example 1 shows a specific method for producing the oxidized modified isoprene rubber of the present invention and the physical properties and characteristics of the obtained oxidized modified isoprene rubber (Samples A-N) (Table 1) , Fig. 1, Fig. 2, Fig. 3, Fig. 4).

Samples A-N all have characteristic absorptions near 3400 cm-' and 1720 cm-' in their infrared absorption spectra, absorption bands in the range of 0 to 120°C in differential scanning calorimetry, and It is characterized by being insoluble.

Example 2 shows examples of blending the oxidatively modified isoprene rubber of the present invention into rubber compositions (Nos. 15 to 28), and their unvulcanized viscosity, vulcanization rate, and post-vulcanized hardness. This is what is shown.

For comparison, an example without softener (No. 29)
Examples of blending conventional softeners (No. 30 to 33)
)showed that.

As is clear from Table 2, among conventional softeners, petroleum softeners, petroleum resins, and liquid rubber 1+ 4 1
．． Mouth vomiting
Besides, the hardness of the vulcanized rubber also decreases. Further, although gum rosin lowers the viscosity of the rubber composition when it is not cured and does not affect the hardness after vulcanization, it significantly slows down the vulcanization rate. On the other hand, the oxidized isoprene-based rubber of the present invention significantly lowers the viscosity of the unvulcanized rubber composition, but rather than lowers the hardness after vulcanization, it improves the physical properties. And it does not affect the vulcanization rate.

<Effects of the Invention> As explained above, the isoprene-based rubber oxidized modified product of the present invention has the above-mentioned properties, and when added to a rubber composition as a softener, the viscosity when uncured increases. Although the hardness after vulcanization is reduced to the same degree as when using conventional softeners, e.g. process oils,
It has the characteristic that it is equivalent to or better than the case without a softener.

Oxidized modified rubber products are extremely useful as softeners and hardness improvers in the rubber industry.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the infrared absorption spectra of samples A, B, D, and E. FIG. 2 is a graph showing the infrared absorption spectra of L and M for samples H, 1, and. FIG. 3 is a graph showing the results of measuring samples A, B, D, and E using a differential scanning calorimeter. FIG. 4 is a graph showing the results of measuring samples H1, K, L, and M using a differential scanning calorimeter. FIG. 5 is a diagram showing an example of an apparatus for producing an oxidized and modified isoprene-based rubber of the present invention. Explanation of symbols 1... Cell, 2... Reflux condenser, 3... Light source, 5... Quartz lid, 6... Water bath FIG. (cm-') FIG, 2 FIG, 3 (°Zino FIG, 4

Claims (2)

[Claims] (1) One of the isoprene-based copolymers produced using isoprene rubber, depolymerized isoprene rubber, cyclized polyisoprene, and isoprene having one or more polar functional groups in the molecule as one type of raw material monomer. It is a modified product derived from more than one species, and has an infrared absorption spectrum of 3.
It has characteristic absorption near 400cm^-^1 and 1720cm^-^1, and has a temperature range of 0 to 120℃ in a differential scanning calorimeter.
An oxidized modified isoprene-based rubber characterized by having an absorption band in the range of . (2) One of isoprene rubber having one or more polar functional groups in the molecule, depolymerized isoprene rubber, cyclized polyisoprene, and isoprene-based copolymers produced using isoprene as one type of raw material monomer. Oxidation of isoprene rubber, characterized in that the oxidized and modified isoprene rubber according to claim 1 is produced by dissolving the above species in a hydrocarbon organic solvent and irradiating it with sunlight or ultraviolet rays in the presence of oxygen. Method for producing modified products.