JPS58442B2 - Graft rubber scale - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying graft rubber, and an object thereof is to provide a method for producing a thermoplastic elastomer that has excellent tensile properties and melt fluidity and has a low gel content. be.

Ethylene/α-olefin copolymer rubber having an ethylene content of about 85 mol % or less cannot be used as it is for rubber purposes because it has low tensile strength and large permanent deformation.

For this reason, attempts have generally been made to crosslink and improve the properties by various means, but those having a considerable amount of crosslinked structure have poor fluidity and cannot be extruded.

However, if an unsaturated dicarboxylic acid or its anhydride is grafted onto the above-mentioned ethylene/α-olefin copolymer rubber with almost no crosslinking, a thermoplastic elastomer with excellent processability and good tensile properties can be obtained. , and a grafting method suitable for it were discovered through research by the present inventors.

The present invention aims to further improve the tensile properties of the rubber thus modified without substantially impairing its fluidity.

That is, the present invention has 0.08 to 1 milliequivalent/g of a derivative consisting of an acid anhydride or ester of an unsaturated polycarboxylic acid or a graft unit of the same and an unsaturated polycarboxylic acid, and has a melt viscosity index ( ASTMD
-1238-65T) in the range of about 0.5 to 30 g/10 min, and the gel content is in the range of about 10% by weight or less.
A method for modifying kraft rubber with excellent melt fluidity, characterized by hydrolyzing ethylene content (with an ethylene content in the range of 50 to 85 mol%) to make it contain at least 0.16 milliequivalents/g of carboxyl groups. be.

The grafted ethylene/α-olefin copolymer rubber used in the present invention has a structure in which an unsaturated polycarboxylic acid derivative or an unsaturated polycarboxylic acid is grafted onto an ethylene/α-olefin copolymer rubber.
It can be obtained by grafting an unsaturated polycarboxylic acid or a derivative thereof onto an α-olefin copolymer rubber, or by deriving it from a grafted product thereof.

The α-olefin component in the ethylene/α-olefin copolymer rubber can be selected from propylene, ■-butene, 4-methyl-1-butene, 4-methyl-1-pentene, etc., but especially propylene Or 1-butene is preferred.

Further, the higher the ethylene content in the copolymer rubber, the higher the tensile strength, but the higher the permanent deformation, so it is preferably in the range of 50 to 85 mol%.

Examples of unsaturated polycarboxylic acids used in the production of graft rubber include maleic acid, fumaric acid, itaconic acid, citraconic acid, allylsuccinic acid, nadic acid, and methylnadic acid.

Further, the unsaturated polycarboxylic acid derivative is a derivative consisting of an acid anhydride or ester of the unsaturated polycarboxylic acid, and specifically, maleic anhydride, itaconic anhydride, citraconic anhydride, allylsuccinic anhydride, nadic anhydride, etc. Examples include acid anhydrides of unsaturated polycarboxylic acids such as methylnadic anhydride, and esters of unsaturated polycarboxylic acids such as monoethyl maleate and dimethyl maleate.

Among these monomers, acid anhydrides are preferred, and maleic anhydride is particularly preferred.

When grafting these, other vinyl monomers may be present.

Grafted rubber using unsaturated polycarboxylic acid as the only monomer cannot be used as a raw material for the present invention as long as it is maintained in a completely grafted state, but it cannot be used as a raw material for the present invention due to the heat during grafting or when the grafted rubber is molded. In many cases, the heat generated during this process partially changes the structure into an acid anhydride structure, and such modified materials can be used as raw materials for the present invention.

Thus, the raw material graft rubber of the present invention has a structure grafted with an unsaturated polycarboxylic acid derivative, preferably an unsaturated dicarboxylic acid anhydride, and these may further contain a graft unit of an unsaturated polycarboxylic acid. .

In order to obtain a modified product with good tensile properties, the content of these graft units should be approximately 0.08 to 1 meq/g.
, preferably 0.1 to 0.6 meq/g.

Furthermore, in order for the modified product to have good processability, the raw material graft rubber must have a melt viscosity index of approximately 0.5 at 230°C.
It should be thrown at between about 1 and 30, preferably between about 1 and 15.

They typically have a gel content (as measured by hot paraxylene insolubles content) of about 10% by weight or less, preferably about 5% by weight or less, and more preferably about 3% by weight or less.

Grafted ethylene/α-olefin copolymer rubber having such properties can be produced by, for example, ethylene/α-olefin copolymer rubber using a radical initiator in an alkyl aromatic hydrocarbon medium at a temperature of at least 115°C or higher. It is obtained by grafting the monomers.

Alternatively, a very small amount of an alkyl peroxide, preferably an aliphatic difunctional peroxide, the monomer and ethylene α
- It can also be obtained by kneading olefin copolymer rubber at 200°C or higher.

For details of these two methods, please refer to Japanese Patent Application No. 50-12123.
3 and the specification of Japanese Patent Application No. 124349/1982.

When such grafted ethylene/α-olefin copolymer rubber is in a solution, molten state, or solid state such as pellets or molded products, some or all of the polycarboxylic acid derivative graft units are added to 1 g of modified rubber with carboxyl groups. 0.16 milliequivalent or more, preferably 0.20 to L2
Hydrolyze until it contains milliequivalents.

There is a very close correlation between the carboxylic acid structure, that is, the content of carboxyl groups, and various physical properties of rubber as an elastomer, such as tensile strength, elongation, permanent set, and heat distortion temperature. In order to maintain the physical properties, it is preferable to carry out the modification within the range described above.

If the grafted monomer is an anhydride of an unsaturated polycarboxylic acid, or even if it is an unsaturated polycarboxylic acid, if it has been transformed into an anhydride by the heat during grafting or molding, hydrolysis may occur. The reaction proceeds relatively easily.

For example, it is only necessary to contact graft rubber in a state with a relatively large surface area, such as a pellet, string, sheet, or film, with liquid or gaseous moisture at about 20 to 120°C.

The contact time varies depending on the shape of the kraft rubber, temperature, water condition, etc., but is about 2 hours to 14 days.

For example, in a method in which a sheet of graft rubber about 1 inch thick is brought into contact with humid air with a relative humidity of 55% at 23°C,
It is sufficient to leave it for about 1 to 2 weeks, and in the method of immersing it in distilled water at 60 to 80°C, about 6 to 10 hours is sufficient.

This hydrolysis reaction may be performed on the graft comb before molding.

However, it is inevitable that the dehydration reaction occurs during molding and a portion of the molded product returns to the acid anhydride group structure, resulting in some loss of diistomer properties, so it is more advantageous to hydrolyze the molded product itself. .

In addition, there are methods in which water vapor is blown into the graft rubber after molding without contact with moisture, and fillers that are highly hygroscopic and do not react with the structural parts of carboxylic acids or their derivatives to cause gelation are added to the graft rubber in advance. This method is effective because it further accelerates the hydrolysis reaction.

In addition, when the grafted monomer is a derivative of an unsaturated polycarboxylic acid other than an anhydride, the object of the present invention can be achieved by conducting a hydrolysis reaction under acidic or alkaline conditions to induce a carboxylic acid structure. It is possible to achieve what you want.

The content of acid anhydride structure, carboxylic acid structure, etc. in the present invention was determined from the IR spectrum of a film obtained by dissolving the graft rubber in a solvent such as cyclohexane and then evaporating the solvent.

The modified kraft rubber obtained in this way has further improved elastomeric properties, such as strength at break, permanent set, heat distortion temperature, etc., compared to the raw material kraft rubber, while the melt viscosity index, which is a measure of moldability. Since there is almost no change, extrusion processing etc. can be easily performed.

In addition, in actual use, various stabilizers such as antioxidants and ultraviolet absorbers, various additives such as lubricants, fillers, pigments, etc. can be appropriately blended.

Next, a more detailed explanation will be given with reference to Examples.

The physical properties of the modified graft rubber obtained by the method of the present invention were evaluated as follows.

[Melt viscosity index (MI), the melt flow of the polymer under a constant load of 1 2H5of
The value was measured at 30℃ for 10 minutes, and the unit is 1710m.
It is m.

[Tensile test]

100% modulus (Mloo), strength at break (Tb)
, the elongation at break (Eb) was measured with an inner diameter of 18 mm and an outer diameter of 2.
The measurement was performed using a 2 mm ring-shaped test piece in an atmosphere of 26° C. at a tensile rate of 50 Omm/min.

[Permanent set (PS)] JIS No. 1 dumbbell test piece was
After elongating by 00% and continuing that state for 10 minutes, the stress was released and the residual elongation (%) after 10 minutes was checked.

[Heat distortion temperature (HDT)] The temperature was measured when the penetration of the sample piece reached 0.1 mm under a load of 49 g.

Example 1 P-xylene 11 and ethylene-propylene copolymer rubber (ethylene content 78 mol%, ML1+4 (1
0 o C) 13, MI 8, Density 0.88) 200 g was charged, the system was replaced with nitrogen, the temperature was raised to 140 C, and then a xylene solution of maleic anhydride and a xylene solution of dicumyl peroxide were added using a pump. (Maleic anhydride 1g/1ml, dicumyl peroxide 1g/10ml
) were fed from separate conduits over a period of 4 hours, and finally 24.5 g of maleic anhydride, 1.35 g of dicumyl peroxide
g 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 washed several times, 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 modified ethylene/propylene copolymer rubber in the form of a white crumb with a diameter of 1 to 5 mm.

The maleic anhydride unit content of this modified product was 3.14% by weight (0.32 meq/g) and the MI was 1.5.

Further, when the gel content was examined by dissolving it in hot para-xylene, it was found to be 0% because it was completely dissolved.

Although this purified ethylene/propylene copolymer rubber was extracted with boiling point acetone for 30 hours using a Soxhlet extractor, the content of maleic anhydride units in the graft rubber did not substantially decrease, so it was considered that the crude kraft rubber It was confirmed that the above-mentioned method was sufficient for the purification of .

This method was used to purify the crude graft material in subsequent experimental examples as well.

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 pressed at a pressure of 40 kg/cmG for 5 minutes. Then, using a compression molding machine through which cooling water was passed, the material was compressed and cooled at 100 kg/cmG to obtain a colorless and transparent sheet with a thickness of 1 mm.

The carboxyl group content of this sheet was determined from an infrared absorption spectrum and was 0.02 milliequivalent.

It was g.

On the other hand, the physical properties of the elastomer are M1oo12kg/cm
, Tb 73kg/cm, Eb 900%, PS 6
%, HDT was 80°C.

This sheet was further immersed in distilled water at 60° C. for 24 hours to hydrolyze the acid anhydride group structure.

As a result, the carboxyl group content was 0.62 milliequivalent/
g, and M at this time.

o is 15kg/cm, Tb140 kg/cm, Eb
The physical properties of the elastomer were significantly improved compared to before hydrolysis treatment: 800%, PS 4%, HDT 115°C.

In addition, in order to investigate the reusability of molded products, which is a major advantage of thermoplastic nidistomers, we measured the MI and gel content of the sheet immersed in hot water.
It was found that the content was 1.4% and 0% by weight, respectively, which was not much different from the raw material graft rubber and could be reused sufficiently.

Example 2 10 kg of approximately 2 mmφ pellets of ethylene-propylene copolymer rubber with an ethylene content of 78 mol%, MI 8, and a density of 0.88, 300 g of powdered maleic anhydride, and 2,5-dimethyl-2 passed through 60 meshes.・5-shi (ter)
t butylperoxy)hexyne-314,3ft(
peroxy group (50 meq) and 10
01 Place in a Henschel mixer and stir for 5 minutes to make a homogeneous mixture (M).

M is transferred through a tube to the hopper of a 40 mmφ extruder (with nitrogen flowing through it).

The extruder is equipped with a single screw with L/D=28 and a dalmage-shaped tip, and the die has four holes with a diameter of 3 mm, and the polymer strands extruded through these holes are water-cooled. It can be made into pellets using a post-cutter.

The rotation speed of the screw of this extruder was 10 Orpm, the residence time of the polymer was 60 seconds, and the temperature of the cylinder was 1 and the temperature of the polymer was 2.
Adjust the temperature to 80℃ and continue extruding at 60℃ per hour.
．． A crude grafting reaction product in the form of pellets was obtained at a ratio of 6 to 6.

100 g of this crude reaction product was dissolved in 11 xylene, transferred to a mixer, stirred at high speed, and 51 acetone was gradually added to precipitate the polymer in the form of crumbs with a diameter of 1 to 5 mm, followed by filtration.

The crumb-like polymer was once again immersed in acetone at room temperature for 2 hours, then taken apart and dried in a vacuum dryer at room temperature for 2 days.

The content of maleic anhydride units in the purified graft rubber obtained was 2.4% by weight (0.24 meq/g), MIo,
8 and the gel content was 1%.

This purified kraft rubber was compression molded in the same manner as in Example 1 to form a transparent, slightly yellow sheet with a thickness of 1 mm.

The carboxyl group content of this sheet is 0.04 milliequivalent/g, and its diistomer physical properties are Mlgol 5
kg/cm, Tb 69kg/ca, Eb900%
, PS 7%, HDT 70°C.

On the other hand, after this sheet was hydrolyzed in the same manner as in Example 1, the carboxyl group content was 0.42 milliequivalents/g, and the physical properties of the diastereomer were as follows: Mtoo l 7kg
/cm, Tb 9.6kg/cd, Eb850%, P
The S content was 5% and the HDT was 89°C, which was a further improvement.

When the MI and gel content of this hydrolyzed sheet were measured, they were 0.7 and 1% by weight, respectively.

Comparative Example 1 Unmodified ethylene/propylene copolymer rubber as polymer (ethylene content 80 mol%, MIo, 7, density 0.8
8), compression molding was performed in the same manner as in Example 1, and a 1 mm
It was made into a sheet.

The physical properties of this sheet can be maintained as is, or
The sheet was examined after being immersed in distilled water at 0'C for 10 days.

The results are shown in Table 1.

Comparative Example 2 Acrylic acid 9. was used instead of maleic anhydride as a modifier.
36 g, ethylene propylene rubber was modified in the same manner as in Example 1 except that methanol was used instead of acetone as a washing solvent after the reaction, and the acrylic acid content*, that is, the carboxyl group content was 3.67% by weight, 0. A grafted rubber with an MI of 5.6 and a weight of .51 meq/g was obtained.

(*Determined from oxygen analysis value) This acrylic acid modified rubber was compression molded in the same manner as in Example 1 to form a 1 mm thick sheet.

The physical properties of this nidistomer were measured either as it was or after immersing it in hot water at 40°C for 10 days.

The results are shown in Table 2.

Example 3 In Example 1, ethylene/1-butene copolymer rubber (ethylene content 81.5 mol%, MI 7.5, density 0.86) was used instead of ethylene/propylene copolymer rubber.
Modification was carried out in exactly the same manner as in Example 1, except that g was used, and the final maleic anhydride unit content was 3.0% by weight (
0.31 meq/g).

A grafted rubber with Mll of 1 and a gel content of 0% was obtained.

This was molded into a 1 mm thick sheet using the same method as in Example 1, and the carboxyl group content and elastomer physical properties were measured before and after hot water immersion treatment (60° C. distilled water for 24 hours).

The results are shown in Table 3. When the MI and gel content of this hydrolyzed sheet were measured, it was found that each
．． 0 and 0% by weight.

Examples 4 to 6 The maleic anhydride-grafted ethylene/propylene copolymer rubber used in Example 1 was molded to a thickness of 1 m in the same manner as in Example 1.
It was compression molded into a sheet of m.

By decomposing this sheet in humid air at a relative temperature of 55% and a temperature of 23°C for 3,7, and 14 days, the amount of cal-phoxyl foundation was 0.19, 0.48, and 0.60 milliequivalents/ A sheet of grafted rubber as shown in g was obtained.

Table 4 shows the results of the physical properties of these elastomers.

Furthermore, the MI and gel content of these hydrolyzed sheets were measured, and the results are also shown in Table 4.

Examples 7 and 8 Citraconic anhydride (56.0%) was used instead of maleic anhydride as the modifier in Example 1, respectively. , or by carrying out the same operation as in Example 1 except for using 61.5 g of allylsuccinic anhydride, the monomer unit content was 0.0, respectively.
10.0.12 meq/g.

Grafted ethylene/propylene copolymer rubbers having MI of 4.3.3.6 and gel contents of 0% by weight and 0% by weight, respectively, were obtained.

Using these kraft rubbers, compression molding was performed in the same manner as in Example 1 to obtain a 1 mm sheet.

These carboxyl group contents and elastomer physical properties were measured before and after hot water immersion treatment (distilled water at 60°C for 24 hours).

The results are shown in Table 5.

Furthermore, the MI and gel content of these sheets after the hydrolysis treatment were measured, and the results are also shown in Table 4.

Examples 9-10 In Example 2, the ethylene-propylene copolymer rubber had an ethylene content of 80 mol% and a number average molecular weight of 32,000.
．． Using 10 kg of approximately 2 mm diameter pellets of ethylene-propylene copolymer rubber with MI5 and density 0.89, equimolar dimethyl maleate (Example 9 )
Alternatively, the same procedure as in Example 2 was carried out except that monoethyl maleate was used and the polymer temperature in the cylinder was changed to 280°C.

Table 6 shows the properties of the purified kraft rubber obtained.

This purified graft rubber was compression molded in the same manner as in Example 1 to form a transparent, pale yellow sheet with a thickness of 1 mm.

Table 6 shows the physical properties of this sheet.

On the other hand, once this sheet is set to 0. Table 6 shows the properties and physical properties after hydrolysis treatment by immersing in an IN sodium hydroxide aqueous solution at 80° C. for 16 hours and then immersing in pure water at 80° C. for 8 hours.

Furthermore, the MI and gel content of the sheet after this hydrolysis treatment were measured, and the results are also shown in Table 6.

Comparative Example 3 A mixture consisting of 200 g of the same ethylene-propylene copolymer rubber used in Example 9 and 6 g of maleic acid was mixed on two rotating rolls at 60° C. for 200 minutes.

An additional 1.21 g of di-tert-butyl peroxide was added at 20° C. and mixing continued for 5 minutes.

Approximately 30 ml of the resulting mixture was pressed in a nitrogen atmosphere at a temperature of 200° C. and a pressure cuff of 0 kg/cm for 30 minutes to allow the reaction to proceed.

This crude graft reaction mixture was treated in the same manner as in Example 1 to obtain a purified graft copolymer.

The physical properties of this purified graft copolymer are that the acid value is 4 mgKOH.
/g (carboxyl group content 0.01 meq/g), M
I is 0.02g/10mln, gel content is 24% by weight,
M,, o is 9 kg/cm, Tb is 15 kg/cm,
Elb was 380% and PS was 17%.

After hydrolyzing this graft rubber according to the method of Example 1, the carboxyl group content was 0.06 meq/g, and the physical properties of the elastomer were Mloo of 9 kg/c.
m, Tb is 17 kg/cm, ELb is 370% and P
S was 16%.

The MI and gel content of the sheet after this hydrolysis treatment were measured and found to be 0.01 and 28% by weight, respectively.

Claims (1)

[Scope of Claims] 1. A derivative consisting of an acid anhydride or ester of an unsaturated polycarboxylic acid, or a graft unit of the same and an unsaturated polycarboxylic acid in an amount of 0.08 to 1 milliequivalent/g, and 230
Grafted ethylene/α-olefin copolymer rubber (ethylene content ranges from 50 to 85 mol%) to remove at least 0 carboxyl groups.
．． A method for modifying a graft rubber having excellent melt fluidity, characterized by containing 16 milliequivalents/g or more.