JPS5853005B2 - Netsukasosei Elastomer - Noseizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to thermoplastic elastomers with good tensile properties, heat resistance, transparency and adhesion.

Unvulcanized ethylene/α-olefin copolymer rubber has low tensile strength and large permanent deformation, so it cannot be used as is for rubber purposes.

For this reason, for example, a method is known from Japanese Patent Publication No. 11679/1983 in which ethylene-propylene copolymer rubber is grafted with maleic anhydride and crosslinked, and further ionically crosslinked with zinc oxide or the like to improve its tensile properties.

That is, in this publication, since the tensile strength of the ethylene-propylene copolymer rubber is low only by modifying it with maleic anhydride, the strength characteristics are further improved by ionic crosslinking.

Both the maleic anhydride-modified rubber and its ionically crosslinked rubber have a high gel content, making them difficult to flow, and therefore cannot be extruded using a normal extruder, resulting in significant restrictions on processing methods.

The present invention provides a thermoplastic nidistomer that has good 9-strength properties and excellent processability without performing such two-stage modification.

The present invention also provides a thermoplastic elastomer that has a high heat distortion temperature (excellent heat resistance) and also has transparency and adhesive properties.

That is, the present invention provides a method for adding an unsaturated dicarboxylic acid or its anhydride to a substantially saturated ethylene/α-olefin copolymer rubber in an alkyl aromatic hydrocarbon medium in the presence of a radical initiator at a temperature of at least 115°C or higher. This is a method for producing a thermoplastic elastomer, which comprises grafting.

Substantially saturated ethylene α used in the present invention
- Olefin copolymer rubber is a rubber-like substance that does not contain any polyene components such as dienes and trienes in its polymer chain, or even if it does, it contains very little, for example, 0.5 mol % or less.

In other words, if an ethylene copolymer rubber with many unsaturated bonds, such as EPDM, which is generally commercially available, is used as a raw material, only a modified product with a high gel content and extremely poor fluidity even at high temperatures will be obtained, so secondary processing will be required. Therefore, the purpose of the present invention cannot be achieved.

The ethylene content of the copolymer rubber is preferably 50 to 85.
mol %, particularly preferably 60 to 83 mol %.

The α-olefin component of the copolymer rubber is selected from propylene, 1-butene, 4-methyl-1-butene, etc., and propylene or 1-butene is particularly preferred.

If a crystalline ethylene/α-olefin copolymer with an ethylene content of more than 85 mol % is used as a raw material, only a modified product with a large permanent deformation will be obtained, making it impossible to achieve the object of the present invention.

Furthermore, in order to produce a modified product with good tensile strength, it is not advantageous to use a copolymer rubber with a low ethylene content.

Copolymer rubbers with various molecular weights of 0 can be used, but generally those with a number average molecular weight (measured by permeation pressure method) of 10,000 to 100,000, particularly 20,000.
It is preferable to use one having a molecular weight of 70,000 to 70,000 because modified products with excellent tensile properties and processability can be easily produced.

In addition, as the raw material rubber of the present invention, a product obtained by oxidative decomposition of the above-mentioned copolymer rubber, whose molecular weight due to decomposition is within about 5%, and whose molecular weight is within the above range, may also be used. I can do it.

In the present invention, an unsaturated dicarboxylic acid or its anhydride is grafted onto the ethylene/α-olefin copolymer rubber using a radical initiator, and the selection of the reaction solvent and reaction temperature is important. be.

As the reaction solvent, an alkyl aromatic hydrocarbon is used, such as toluene, various xylenes, ethylbenzene, ethyltoluene, cumene, cymene, diethylbenzene, trimethylbenzene, diisopropylbenzene (. is a mixture thereof, etc.).

Using something other than alkyl aromatic hydrocarbons as a reaction solvent, such as unsubstituted aromatic hydrocarbons such as benzene, halogenated hydrocarbons such as chlorobenzene, aliphatic hydrocarbons such as octane, decane, and kerosene, etc. However, the tensile strength of the resulting graft modified product is as low as the raw rubber, and it cannot be used as is for various purposes.

Although the reaction temperature varies depending on the type of radical initiator used, it must be at least 115°C or higher, preferably 120 to 200°C.

If the reaction temperature is lower than the above range, the tensile strength of the resulting graft-modified product will be low and the gel content will be high, which is not preferable.

Specific examples of unsaturated dicarboxylic acids or their anhydrides used for grafting include maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, maleic anhydride,
Examples include citraconic anhydride and nadic anhydride.

It is particularly preferable to use acid anhydrides, and maleic anhydride is the most preferred monomer.

Radical initiators useful in the present invention include commonly used radical initiators, such as organic peroxides and azonitrile.

Examples of organic peroxides include lauroyl peroxide, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, p-chlorobensoyl peroxide, 2,4-dichlorobensoyl peroxide, 4-methoxybenzoyl peroxide, and phthaloyl. Peroxide, dicumyl peroxide, p-menthane hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-(tert-7” tylperoxy)hexane, 2・5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, α・α
'-di(tert-butylperoxy)diisopropylbenzene, tert-butylperoxyisobutyrate, tert-butylperoxyhybarate, tert
-butylperoxy-2-ethylhexanony), t
Examples include ertbutyl peroxylaurate and acetylcyclohexane sulfonyl peroxide.

Examples of azonitrile include azobisisobutyronitrile, azobisisopropionitrile, and the like.

The reaction of the present invention can be carried out in various ways.

Generally, it is preferable to adopt a method of dissolving the copolymer rubber in an alkyl aromatic hydrocarbon and adding an unsaturated dicarboxylic acid or its anhydride and an organic peroxide thereto.

At this time, a method of adding the surrounding components of the monomer and radical initiator to the rubber solution all at once, a method of adding only one side at once,
There is a method in which other components are added continuously or discontinuously in small amounts, or a method in which surrounding components are added in small amounts in portions.

Among these methods, the method of partially adding the surrounding components in small amounts is preferred because the modified product has excellent strength and processability.

These polymerization methods can be carried out not only by a batch method but also by a semi-continuous method or a continuous method.

During the reaction, the amount of the alkyl aromatic compound used is preferably an amount sufficient to maintain a low viscosity in the system in order to proceed smoothly with the reaction.
The amount by weight is preferably 4 to 20 times by weight.

The amount of radical initiator used varies depending on its type and reaction temperature, but usually copolymer rubber 1
0.001 to 0.5 mol, preferably 0
．． 0.005 to 0.1 mole.

The amount of unsaturated carboxylic acid or its anhydride used is generally selected so that the acid value of the modified product is 8 or more.

Therefore, it is generally in the range of 0.1 to 10 mol, preferably 0.3 to 6 mol, per 1 kg of copolymer rubber, although it naturally varies depending on the reaction conditions.

In order to isolate the modified product, that is, the thermoplastic elastomer of the present invention, from the reaction mixture, the reaction mixture is poured into a large amount of acetone, the modified product is precipitated, and then, if necessary, a non-solvent such as a precipitant is added. It may be cleaned or, more conveniently, a technique such as steam stripping may be used.

The thermoplastic elastomer of the present invention generally has an acid value of 8 or more, preferably an acid value of 14 to 50, and a melt index (
It is desirable that the material be modified so that the ASTM D1238-65T) is 0.1 to 30.

These have high tensile strength and impact resilience, low permanent deformation, good heat resistance and processability, and can be processed into rubber products of arbitrary shapes using an extruder or the like.

Next, the present invention will be explained in more detail with reference to examples.

The physical properties of the modified ethylene/α-olefin copolymer rubber obtained by the method of the present invention were evaluated as follows.

[Melt index (MI)] The melting flow of a polymer under a constant load of 2160P is 2
The value was measured at 30'C for 10 minutes, and the unit is g/1.
01Mt.

[Tensile test]

100% modulus, strength at break, and elongation at break were measured using a ring-shaped test piece with an inner diameter of 18 mm and an outer diameter of 22 mm.
Measurement was carried out in an atmosphere at 26° C. at a tensile rate of 5007ILrIL/cylinder.

[Permanent distortion]

1 JIS No. 1 dumbbell test piece in an atmosphere of 26℃
After elongating by 00% and continuing that state for 10 minutes, the stress was released and the residual elongation (%) after 10 minutes was measured.

[Heat distortion temperature]

49′? The temperature was measured when the penetration of the sample piece reached 0.1 mm under a load of .

Example 1 In a 2 ton stainless steel pressure-resistant reaction vessel equipped with a thermometer and a stirring bar, 1 ton of p-xylene and ethylene-propylene copolymer rubber (ethylene content 78 mol%,
℃) 13, MI8) 200P was charged, the system was replaced with nitrogen, the temperature was raised to 125℃, and then a xylene solution of maleic anhydride and a xylene solution of dicumyl peroxide (maleic anhydride 11/ 1rrLl,
Dicumyl peroxide 11/10rILl) was fed through separate conduits over 4 hours, and finally maleic anhydride 2
4.5? , 1.35f of dicumyl peroxide was supplied into the system.

After continuing stirring for an additional 2 hours, the system was cooled to around room temperature.

The reaction solution was poured into a large amount of acetone to precipitate the maleic anhydride graft polymer, which was then collected, and the modified product was washed repeatedly with acetone.

The washed precipitate was dried under reduced pressure at room temperature for 2 days to obtain a white popcorn-shaped modified ethylene/propylene copolymer rubber.

The acid value of this modified product was 23 (maleic anhydride unit content by infrared absorption spectrum was 3.2% by weight), and M
I was 0.7.

The maleic anhydride grafted ethylene-propylene copolymer rubber obtained by the above method was preheated for 5 minutes using a compression molding machine set at 175°C to fluidize the polymer, and then heated at a pressure of 40 kg/crtlG for 5 minutes. Press,
Furthermore, using a compression molding machine through which cooling water is passed, 100 kg/c
It was pressed with rAG and cooled to obtain a colorless and transparent sheet with a thickness of 1 inch.

When we measured the physical properties of this sheet as an elastomer, we found that it had a 100% modulus of 12 kg/cr; L, a strength at break of 68 kg/crA, an elongation at break of 900%, and a permanent set of 5%.
, the heat distortion temperature was 102°C.

In addition, this modified product is benzene, xylene, tetralin,
Since it is completely dissolved in solvents such as decalin, dichloroethylene, and trichlorobenzenecyclohexane, the gelation rate can be considered to be substantially 0%.

Comparative Example 1 The same operation as in Example 1 was performed except that maleic anhydride was not supplied.

As a result, a polymer with an acid value of 0 and an MI of 7.3 was obtained.

When I investigated this physical property, I found that it had a 100% modulus of 6
kg/crA, strength at break 9 kg/cd, elongation at break 6
The results were 90% permanent deformation, 22% permanent set, and a heat distortion temperature of 26° C. or less, which showed no difference in physical properties from the raw material polymer and did not exhibit any elastomer-like physical properties.

Example 2.3.4.5.6 Toluene mixed xylene, cumene, cymene,
A maleic anhydride-modified ethylene-propylene copolymer rubber was obtained by carrying out the same operation as in Example 1, except that each solvent of mesitylene was used and the amount of maleic anhydride supplied was as shown in the table below.

Table 1 shows their acid value, MI, and physical properties as a nidistomer.

This table shows that the obtained modified product can be used satisfactorily as a thermoplastic nidistomer.

Comparative Example 2.3.4.5 The same operation as in Example 1 was carried out, except that the solvent Toshite, benzene, chlorobenzene, and n-decane kerosene were used, and the amount of maleic anhydride supplied was as shown in Table 3 below. A maleic anhydride-modified ethylene/propylene copolymer was obtained.

Table 2 shows their acid value, MI, and physical properties as elastomers.

As described above, when these solvents are used, only the MI is greatly reduced, and the tensile strength and permanent set are hardly improved compared to the raw material polymer, which is insufficient for use as an elastomer. .

Example 7 and Comparative Example 6 The reaction temperature was 110.140°C, and the amount of maleic anhydride supplied was 78.4.24.5'! By performing exactly the same operation as in Example 1 except for /, acid value pot 2
Modified ethylene/propylene copolymer rubbers of 3.24 MI and 0.02 and 1.0, respectively, were obtained.

The physical properties of these elastomers are shown in Table 3.

As described above, when the reaction is carried out at 110° C., the MI becomes extremely low, resulting in a decrease in workability, and furthermore, the tensile strength becomes so low as to be of no practical use.

Example 8.9 Benzoyl peroxide 1.2 as radical initiator
1S' or di-tert-butyl peroxide 1.
The same operation as in Example 1 was carried out except that 46P was used to obtain modified ethylene-propylene copolymer rubbers each having an acid value of 24.22 and an MI of 0.7.06.

These tensile properties are shown in Table 4, and they had sufficient practical properties as a thermoplastic nidistomer.

Example 10 and Comparative Example 7 As a raw material polymer, ethylene/1-butene copolymer comb (ethylene content 80 mol%, MI (230°C) 10)
Alternatively, ethylene/propylene/dicyclopenk diene copolymer rubber (ethylene content: 7).

mol%, dicyclopentadiene content 2.5 mol%, MI
(230° C.) The same operation as in Example 1 was performed except that 3) was used.

As a result, when a rubber containing a diene component was used, the viscosity of the reaction solution increased so much that the reaction had to be stopped 2 hours after the dropwise addition of maleic anhydride and dicumyl peroxide started.

Hereinafter, the same operation as in Example 1 was performed, and the acid value was 24.7 each.
, MI of 0.8, o, and oi were obtained.

It was found that the latter could not be compression molded at all and could not be considered a raw material for thermoplastic elastomers in terms of processability.

On the other hand, the physical properties of a modified ethylene/1-butene copolymer rubber are 100% modulus of 13 kLg/crA, strength at break of 75 kg/crA, elongation at break of 700%, and permanent set of 6%, which are sufficient for use as a thermoplastic nidistomer. I understand.

Reference Example The modified ethylene/propylene copolymer rubber 261 obtained in Example 1 was sandwiched between 0.2 mm thick steel plates and heated at 200°C.
After preheating for 5 minutes using a compression molding machine set to 5
Pressure was applied at 0 kg/cniG for 5 minutes.

Further, transfer to a compression molding machine with cooling water flowing to 100 kg/c.
It was pressed with aG for 3 minutes and cooled.

In this way, a laminate having a total thickness of 1 mm was obtained.

This laminate was cut to a width of 2 crIL and subjected to a 1800 peel test in an atmosphere at 23°C.

As a result, the peel strength was 23 ky/crIl, indicating very strong adhesion.

Example 11 Fumaric acid 46. instead of maleic anhydride as a modifier.
4? Before starting the reaction, the same ethylene-propylene copolymer rubber 2001 as in Example 1 and 1 ton of mixed xylene were charged into a reaction vessel.

The inside of the system is replaced with nitrogen while stirring.

The temperature was increased to 125°C and a xylene solution of DCP (DCP
1, 351) was added dropwise over 4 hours, and stirring was continued for an additional 2 hours.

After the reaction is completed, by performing the same operation as in Example 1,
The modified polymer was precipitated, and the precipitate was thoroughly washed with methanol.

The obtained modified ethylene-propylene copolymer rubber had an acid value of 16 and an MI of 6.5.

This modified product was compression molded into a sheet with a thickness of 17IL and 7IL in the same manner as in Example 1, and its physical properties were examined, and it was found that the 100 modulus was 20 kg/crA and the strength at break was 96 kg/c.
al, elongation at break was 790%, and permanent set was 12%.

Claims (1)

[Claims] 1. Grafting an unsaturated dicarboxylic acid or its anhydride onto a substantially saturated ethylene/α-olefin copolymer rubber in an alkyl aromatic hydrocarbon medium in the presence of a radical initiator at a temperature of at least 115°C or higher. A method for producing a thermoplastic elastomer characterized by: