JPH0463850A - Thermoplastic elastomer composition - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic elastomer composition excellent in injection moldability, shape recovery at high temperature, and oil resistance and desirable for highperformance automobile components or the like by adding a specified resin and a vulcanizer to an ethylene/alpha-olefin/nonconjugated diene elastomer. CONSTITUTION:A thermoplastic elastomer composition is obtained by dynamically vulcanizing a composition comprising 100 pts.wt. ethylene/alpha-olefin/ nonconjugated diene copolymer rubber (A) having a Mooney viscosity (ML1+4/125 deg.C) of 40 or above when 100 pts.wt. this rubber is mixed with 75 pts.wt. mineral oil softener, 10-500 pts.wt., desirably 20-400 pts.wt. crystalline ethylene/propylene block copolymer resin (B) having a melt flow rate of 10-50, 5-100 pts.wt., desirably 10-50 pts.wt. low-molecular weight propylene homopolymer resin (C) having a number-average molecular weight of 2000-20000, and 3-300 pts.wt. mineral oil softener (D), desirably a paraffinic mineral oil, and having an A/C weight ratio of 0.8 or below with 0.5-15 pts.wt. reactive alkylphenol/formaldehyde resin as a vulcanizer.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a thermoplastic elastomer composition, and more specifically, it is suitable for use in automobile parts, industrial machine parts, etc. that require high functionality, and is suitable for injection molding. The present invention relates to a thermoplastic elastomer composition that has well-balanced improvements in properties, mechanical properties, low anisotropy, shape recovery properties at high temperatures (for example, compression set), and oil resistance.

[Conventional technology]

Olefin thermoplastic elastomer compositions made of olefin rubber and crystalline olefin resin are excellent in flexibility, heat aging resistance, weather resistance, and the like.

However, most conventional olefinic thermoplastic elastomer compositions are partially vulcanized using organic peroxides, and lack oil resistance and shape recovery properties at high temperatures (e.g., compression set). This makes it difficult to use it as a high-performance material.

Furthermore, vulcanization using organic peroxides causes crosslinking and molecular scission of the crystalline olefin resin at the same time as vulcanization of the olefin rubber, making it difficult to achieve a high degree of vulcanization, and also impairing the mechanical properties of the resulting composition. It also has the disadvantage of being inferior.

As a method to improve this drawback,
As shown in No. 38 and JP-A No. 5L-91142, a method using a reactive alkylphenol formaldehyde resin (hereinafter abbreviated as "phenolic vulcanizing agent") as a vulcanizing agent is known. ing.

That is, the above method uses a phenolic vulcanizing agent as a vulcanizing agent to produce ethylene-α olefin-
This method improves the degree of vulcanization by selectively reacting only the double bonds in the non-conjugated diene copolymer rubber. According to this method, it is possible to achieve a high level of vulcanization that cannot be achieved with vulcanization systems using organic peroxides, and the resulting composition has significantly improved oil resistance and shape recovery properties at high temperatures. Become something.

As a result, olefin-based thermoplastic elastomer compositions have traditionally been used in fields requiring functionality such as chloroprene rubber, chlorsphonated polyethylene rubber, ethylene-propylene-diene copolymer rubber,
It has become possible to use it mainly as a substitute for synthetic rubbers such as acrylonitrile butadiene copolymer rubber, and in fields where high functionality is required, such as automobile parts and industrial machinery parts.

[Problem to be solved by the invention]

However, olefinic thermoplastic elastomer compositions using phenolic vulcanizing agents have insufficient fluidity;
Injection moldability is poor, and thin-walled molded products in particular have the disadvantage of causing a filling defect phenomenon.

In addition, injection molded products obtained from the above-mentioned olefinic thermoplastic elastomer compositions have strong anisotropy in mechanical properties, and as a result, depending on the shape of the molded product, properties such as tensile strength and elongation at break may be significantly inferior. In some cases, this may cause problems in practice.

The present invention aims to solve these problems and provide an olefinic thermoplastic elastomer composition having excellent physical properties.

[Means to solve the problem]

That is, the gist of the present invention is as follows: (a) Mooney viscosity [MLI +
4 (125°C) ) is 40 or more: 100 parts by weight (b) Crystalline ethylene-propylene block copolymer resin having a melt flow rate in the range of 10 to 50 =
10 to 500 parts by weight (c) Number average molecular weight is 200
Low molecular weight propylene homopolymer resin in the range of 0 to 20,000 = 5 to 100 parts by weight (d) Mineral oil softener: Consisting of 3 to 300 parts by weight, low molecular weight propylene alone for the crystalline ethylene-propylene block copolymer resin By dynamically vulcanizing a composition in which the weight ratio of polymer resin is 0.8 or less using 0.5 to 15 parts by weight of a reactive alkylphenol φ formaldehyde resin as a vulcanizing agent, ethylene-α - An olefin-based thermoplastic elastomer composition obtained by highly vulcanizing an olefin-nonconjugated diene copolymer rubber.

The present invention will be explained in detail below.

In the thermoplastic elastomer composition according to the present invention, it is necessary to use an ethylene-α-olefin-nonconjugated diene copolymer rubber as the first component.

The α-olefin in the copolymer rubber has 3 to 1 carbon atoms.
5 is suitable. Examples of the non-conjugated diene include dicyclopentadiene, 1,4-hexadiene, ethylidene norbornene, and methylidene norbornene. In the present invention, from the viewpoint of availability and vulcanization speed,
Propylene is suitable as the α-olefin, and ethylidene norbornene is suitable as the non-conjugated diene. Therefore,
Ethylene-propylene-ditylidene norbornene copolymer rubber is suitable as the copolymer rubber.

The weight ratio of ethylene/α-olefin in the copolymer rubber is in the range of 50150 to 90/IO, preferably 60/4.
It is in the range of 0 to 80/20. Further, the amount of non-conjugated diene in the copolymer rubber is 5 to 30 in terms of iodine value, especially,
A range of 10 to 20 is desirable.

Further, the copolymer rubber described above needs to have a high molecular weight in order to obtain good mechanical properties.

Specifically, the Mooney viscosity of a product containing 100 parts by weight of copolymer rubber and 75 parts by weight of a mineral oil softener [:ML1]
+4 (125°C)) is required to be a high molecular weight copolymer rubber of 40 or more.

The thermoplastic elastomer composition according to the present invention has a melt flow rate (MFR) (JIS
K7210, 230°C9 load 2.16kg) is 10~
It is necessary to use a high fluidity crystalline ethylene-propylene block copolymer resin in the range of 50. By using such a specific second component, the compatibility with the high molecular weight copolymer rubber of the first component is greatly improved, so that miscibility of the two polymers can be achieved even if their flow properties are significantly different. Ru.

If the MFR of the crystalline ethylene-propylene block copolymer resin is lower than 10, sufficient fluidity, which is the object of the present invention, cannot be obtained. On the other hand, when it is higher than 50, the mechanical properties are significantly deteriorated.

In the present invention, the crystalline ethylene-propylene block copolymer resin is used in an amount of 10 to 500 parts by weight, preferably 20 to 400 parts by weight, based on 100 parts by weight of ethylene-α-olefin-nonconjugated diene copolymer rubber. use.

If the proportion used is less than 10 parts by weight, the resulting thermoplastic elastomer composition will have poor fluidity and a good molded product will not be obtained. If it is more than 500 parts by weight, the resulting thermoplastic elastomer composition will have too high a hardness and will lack its characteristic flexibility.

The thermoplastic elastomer composition according to the present invention requires the use of a low molecular weight propylene homopolymer resin having a number average molecular weight in the range of 2,000 to 20,000 as the third component. This provides a further effect of improving fluidity and eliminating anisotropy in mechanical properties.

If the number average molecular weight of the low molecular weight propylene homopolymer resin is less than 2,000, the resulting thermoplastic elastomer composition will undesirably ooze out. When the number average molecular weight is greater than 20,000, the effect of eliminating anisotropy is not sufficient.

In the present invention, low molecular weight propylene homopolymer resin is added in an amount of 5 to 100 parts by weight, preferably 1 part by weight, per 100 parts by weight of ethylene-α/olefin-nonconjugated diene copolymer rubber.
It is used in a range of 0 to 50 parts by weight. If the proportion used is less than 5 parts by weight, the effect of eliminating anisotropy due to the use of the low molecular weight propylene homopolymer resin will not be exhibited. If the proportion used is more than 100 parts by weight, the mechanical properties will be significantly reduced.

In the present invention, low molecular weight propylene homopolymer resin/
It is necessary that the ratio of crystalline ethylene-propylene block copolymer resin is 0.8 or less.

If this ratio is larger than 0.8, the viscosity difference between the copolymer rubber and the low molecular weight propylene homopolymer resin-crystalline ethylene-propylene block copolymer resin mixture during dynamic vulcanization becomes too large, and the copolymer rubber Poor dispersion occurs.

For this reason, a good olefinic thermoplastic elastomer composition cannot be obtained.

In the present invention, a mineral oil-based softener is used to impart flexibility to the olefin-based thermoplastic elastomer composition and improve fluidity. From this point of view, paraffinic mineral oil is preferred.

The mineral oil softener is used in an amount of 3 to 300 parts by weight based on 100 parts by weight of the ethylene-α/olefin nonconjugated diene copolymer rubber. If the proportion used is more than 300 parts by weight, the mechanical properties of the resulting composition will deteriorate and the mineral oil will ooze out, which is undesirable from a practical standpoint. Furthermore, if the proportion used is less than 3 parts by weight, no sufficient fluidity improvement effect will be observed.

The mineral oil softener may be included in the copolymer rubber in advance, it may be added during dynamic vulcanization, before or after dynamic vulcanization, or a combination of these treatments may be used. You can.

The phenolic vulcanizing agent used in the present invention is a substance represented by the following formula.

Here, n is an integer of 0 to 10, X is a hydroxyl group or a halogen atom, and R is a saturated hydrocarbon group having 1 to 15 carbon atoms.

The above substances are commonly used as vulcanizing agents for rubber, as described, for example, in US Pat. No. 3,287,440 and US Pat. No. 3,709,840. This vulcanizing agent is obtained by condensation polymerization of a substituted phenol and an aldehyde in an alkaline medium.

The amount of the vulcanizing agent used is in the range of 0.5 to 15 parts by weight per 100 parts by weight of the ethylene-α-olefin-nonconjugated diene copolymer rubber. If the amount of the vulcanizing agent used is less than 0.5 parts by weight, the degree of vulcanization during dynamic vulcanization will be low, and the resulting composition will not have sufficient oil resistance, shape recovery properties at high temperatures, etc. If the amount is more than 1 part by weight, the flexibility of the resulting composition will be impaired. The preferred amount of vulcanizing agent used is
The amount is in the range of 1 to 10 parts by weight, more preferably 3 to 8 parts by weight, based on 100 parts by weight of the copolymer rubber.

The vulcanizing agent can be used alone, but it can also be used in combination with a vulcanization accelerator in order to adjust the vulcanization rate. As the vulcanization accelerator, metal halides such as stannous chloride and ferric chloride, and organic halides such as chlorinated polypropylene, butyl bromide rubber and chloroprene rubber can be used. When a vulcanization accelerator is used together, it is more preferable to use a metal oxide such as zinc oxide.

In the present invention, dynamic vulcanization means vulcanizing the ethylene-α-olefin-nonconjugated diene copolymer rubber while mixing and kneading each component.

For this purpose, it is desirable to use the method described in Japanese Patent Publication No. 55-46138.

That is, an ethylene-α-olefin-nonconjugated diene copolymer rubber and a mineral oil-based softener are added to a crystalline ethylene-propylene block copolymer resin and a low molecular weight propylene homopolymer resin, and usually a crystalline ethylene-propylene block copolymer resin is added. Temperature higher than the temperature at which the polymeric resin melts (usually 1
60-250°C). Thereafter, while continuing kneading, an alkylphenol vulcanizing agent is added and kneading is continued to perform dynamic vulcanization.

As the kneading device, a batch kneading device such as Banbury Mixer 1 heating roll or various kneaders, or
Continuous kneading equipment such as a single-screw extruder or a twin-screw extruder can be used.

In the present invention, by the above dynamic vulcanization, ethylene-
The α-olefin-nonconjugated diene copolymer rubber is highly vulcanized. Here, highly vulcanized refers to unvulcanized ethylene-α, which is extracted with hot xylene from the ethylene-α-olefin-nonconjugated diene copolymer rubber contained in the obtained thermoplastic elastomer composition. It means that the amount of olefin-nonconjugated diene copolymer rubber is less than 5% by weight.

As mentioned above, the degree of vulcanization is determined by the vulcanized ratio of ethylene-α-olefin-nonconjugated diene copolymer rubber in the olefin-based thermoplastic elastomer composition; Regarding the components to be considered, focus only on the ethylene-α-olefin-non-conjugated diene copolymer rubber, and there is no need to consider components such as additives other than the ethylene-α-olefin-non-conjugated diene copolymer rubber. .

The details of the hot xylene extraction method will be explained in Examples below.

In the present invention, after dynamic vulcanization, a crystalline propylene-ethylene block copolymer resin, a low molecular weight propylene homopolymer resin, and a mineral oil-based softener can be added within the scope of the present invention.

In addition, a filler is used before and after dynamic vulcanization, or when adding the above-mentioned crystalline olefin resin for homogenization.

Antioxidant, copper inhibitor 7 colorant, ultraviolet inhibitor.

Processing aids such as lubricants may also be added.

The thermoplastic elastomer composition according to the present invention can be molded into a desired molded article by a normal injection molding method, and the molded article has a good surface appearance, various physical properties have been improved in a well-balanced manner, and it can be used for automobile parts, industrial parts, etc. It can be suitably used in a wide range of applications such as parts.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

In the following examples, injection molded flat plates for appearance evaluation were prepared and physical properties were measured in the following manner.

<Creation of injection molded flat plate for appearance evaluation> (1) Shape length: 20cm, width! 5 Cm% thickness 2m (2) Mold film gate type (width 15mm +, thickness 5mm) (3)
Molding machine manufactured by Sumitomo Heavy Industries ■, Sumitomo Nestal Neomat 5G15
0 (mold clamping force 120t) (4) Molding conditions Cylinder temperature (rear) 180°C Cylinder temperature (middle) 190°C Cylinder temperature (front) 20
0°C Nozzle temperature 200°C Mold temperature 40°C Injection pressure 90% of maximum injection pressure Injection speed 50% of maximum injection speed <Measurement of physical properties> (1) Hardness Based on ASTM D-2240, durometer A
type was used.

(2) Tensile test According to JfS K6301, an injection molded plate was punched out using a No. 3 dumbbell in parallel and perpendicular directions to the flow direction.

(3) Compression set according to JIS K6301, conditions are 100°C x 2
It was compressed at 25% for 2 hours.

(4) Oil resistance In accordance with JIS K6301, a test piece measuring 50 mm x 25 mm x 2 mm was immersed in N083 test oil to measure weight changes. The immersion conditions were 70°C for 22 hours.

(5) Melt flow rate Based on JIS K7210, crystalline ethylene-propylene block copolymer resin is 230°C, 2.16 kg
Measured under the following conditions. The olefin thermoplastic elastomer composition was measured at 230°C and 15 kg.

(6) The number average molecular weight of the low molecular weight propylene homopolymer was measured using GPC under the following conditions. Molecular weight was calculated in terms of polystyrene.

Apparatus Waters 150c Column Toyo Soda GMH-HT Solvent O-dichlorobenzene, (0.0% as a stabilizer)
(Contains 2% 3,5-di-t-butyl-4-hydroxy-toluene) Column temperature 140°C Injection part 140°C (7) The amount of thermal xylene extracted was measured by the following method.

The olefinic thermoplastic elastomer composition is made into a film of 0.1 mm or less using a press.

Approximately 1.5 g of the olefinic thermoplastic elastomer composition was accurately weighed (this weight is referred to as Wl), placed in 100 ml of boiling xylene, and stirred for 30 minutes.

The liquid is cooled to room temperature and filtered using a 0.3μ Teflon membrane filter.

Evaporate the xylene in the filtrate until the filtrate becomes about 5 cc and transfer to a centrifuge tube using 10-cyclohexane.

Add acetone 10- and centrifuge at 110,000 RP for 15 minutes. The supernatant liquid is removed and further washed with a solvent of cyclohexane/acetone = 1/1.

Measure the weight after sufficiently evaporating the solvent.

The same operation as above is also carried out for the crystalline propylene polymer. (W, , the weight corresponding to W2 is W3
, W<) The weight percentage of the ethylene-α·olefin-nonconjugated diene copolymer rubber in the olefin thermoplastic elastomer composition is WE, and the weight percentage of the crystalline propylene polymer is W.

The thermal xylene extraction amount E (%) is calculated by the following formula.

However, when using oil-extended ethylene-α olefin-nonconjugated diene copolymer rubber (ethylene-α olefin-nonconjugated diene copolymer rubber containing paraffinic mineral oil in advance), oil-extended The paraffinic mineral oil in the ethylene-α-olefin-nonconjugated diene copolymer rubber is excluded, and the weight percentage of only the ethylene-α-olefin-nonconjugated diene copolymer rubber is defined as WE.

In the examples below, the following samples were used:

(1) For the ethylene-α-olefin-nonconjugated diene copolymer rubber (hereinafter referred to as EPDM), a copolymer rubber using propylene as the α-olefin and ethylidene norbornene as the nonconjugated diene was used. The iodine value is 1
5. Mooney viscosity [ML1+4 (125°C)] (75 parts by weight of paraffin softener per 100 parts by weight of copolymer rubber)
Weight part) is 64, ethylene content is 60 (weight%)
It is.

(2) The following crystalline ethylene-propylene block copolymer resin was used. The unit of MRF is (g/100m
1n) (the same applies hereinafter).

■ MFR2Or block PP-IJ ■ MFR40r block PP-2J ■ MFR5r block PP-3'' ■ MFR60r block PP-4J (3) The following crystalline propylene homopolymer resins were used.

■ MFR2Or homo PP-IJ ■ MFR40r homo PP-2J (4) The following low molecular weight propylene homopolymer resins were used.

■Molecular weight 200Or low molecular weight PP-IJ■Molecular weight 1
5000 r Low molecular weight PP-24■ Molecular weight 500
[Low molecular weight PP-3J■ Molecular weight 50000
rLow molecular weight PP-4J (5) A paraffinic softener with a kinematic viscosity of 100 (cSt, 040°C) was used as the mineral oil softener.

(6) As the phenolic vulcanizing agent, dimethylol-p-cutyl-phenol-formaldehyde resin was used.

(7) The vulcanization accelerator is stannous chloride (SnC72”6
H2O) and zinc oxide were used.

Example 1 40 parts by weight of block PP-1, 15 parts by weight of low molecular weight pp 1.100 parts by weight of EPDM, 2 parts by weight of stannous chloride, 2 parts by weight of zinc oxide and 75 parts by weight of paraffinic The mixture consisting of the softener was kneaded at a rotor rotation speed of 150 RPM in a Banbury mixer having an internal volume of 31 and temperature controlled at 120°C.

When the temperature of the kneaded material reached 170°C due to self-heating, the vulcanizing agent was added and kneading was continued for another 3 minutes.After that, 75 parts by weight of paraffin softener was added and kneading was continued for 1 minute. , an olefinic thermoplastic elastomer composition was obtained.

The physical properties of the obtained olefin thermoplastic elastomer composition are shown in Table 1-2.

From the results in Table 1-2, the appearance of the injection molded product is good;
Excellent mechanical properties, shape recovery (compression set), and oil resistance.
It can be seen that the mechanical object has little sexual anisotropy. Moreover, it can be seen from the melt flow rate (MFR) that the obtained olefinic thermoplastic elastomer composition has good fluidity.

Examples 2 to 7 Olefin thermoplastic elastomer compositions were obtained in the same manner as in Example 1 using the amounts shown in Table 1-1.

The physical properties of the obtained olefin thermoplastic elastomer composition are shown in Table 1-2.

From the results in Table 1-2, the appearance of the injection molded product is good;
Excellent mechanical properties, shape recovery (compression set), and oil resistance.
It can be seen that the mechanical object has little sexual anisotropy. Also, MFR
It can be seen that the obtained thermoplastic olefin elastomer composition has good fluidity.

Comparative Examples 1 to 7 Olefin thermoplastic elastomer compositions were obtained in the same manner as in Example 1 using the amounts shown in Table 2-1.

However, in Comparative Example 2, since there was little self-heating, the vulcanizing agent was added when the temperature of the kneaded material reached 160°C.

The physical properties of each composition obtained are shown in Table 2-2.

In Comparative Example 1, the injection molded product had a good appearance and was excellent in mechanical properties, shape recovery (compression set), and oil resistance, but the anisotropy of the mechanical properties was large and the fluidity was poor.

In Comparative Example 2, an olefinic thermoplastic elastomer composition could not be obtained due to extremely poor dispersion of EPDM.

In Comparative Example 3, oozing occurred on the surface of the injection molded product, and the obtained olefin thermoplastic elastomer composition had no practical value.

In Comparative Example 4, although the appearance of the injection molded product is good and the mechanical properties, shape recovery (compression set), and oil resistance are excellent, the anisotropy of the mechanical properties is large.

In Comparative Example 5, the appearance of the injection molded product is almost good, and the mechanical properties, shape recovery (compression set), and oil resistance are excellent, but the anisotropy of the mechanical properties is large and the fluidity is poor.

In Comparative Example 6, the injection molded product had a good appearance and excellent shape recovery properties (compression set) and oil resistance, but its mechanical properties were significantly inferior.

In Comparative Example 7, the resulting olefinic thermoplastic nylastomer composition was extremely brittle and could not be injection molded.

Comparative Examples 8 to 11 Olefin thermoplastic compositions were obtained in the same manner as in Example 1 using the amounts shown in Table 3-1.

The physical properties of each composition obtained are shown in Table 3-2.

In Comparative Example 8, although the appearance of the injection molded product was good,
High hardness and poor flexibility.

In Comparative Example 9, there was significant bleeding on the surface of the injection molded product, and the mechanical properties were also extremely low.

In Comparative Examples IO and 11, shape recovery property (compression set),
Although it has excellent oil resistance, it has poor elongation at break and fluidity.
The surface of the injection molded product is rough and has no practical value.

(The following is a blank space) [Effects of the Invention] The thermoplastic elastomer composition according to the present invention has the following characteristics, and has extremely high industrial utility value.

(1) It can be molded by a normal thermoplastic resin molding method, and a molded product with a good appearance can be easily obtained.

(2) Since there is little anisotropy in mechanical properties during injection molding, it can be applied to molded products of various shapes.

(3) It has excellent mechanical properties, shape recovery properties, oil resistance, etc., and can be suitably used in applications that require these performances.

Applicant: Mitsubishi Monsanto Chemicals Co., Ltd. Agent: Patent Attorney Oka 1) Kazuhiko

Claims (1)

[Claims] (1) (a) Mooney viscosity of a product made of ethylene-α/olefin-nonconjugated diene copolymer rubber and containing 75 parts by weight of a mineral oil softener in 100 parts by weight of the rubber [ML1
+4 (125°C)] of 40 or more: 100 parts by weight (b) Crystalline ethylene-propylene block copolymer resin with a melt flow rate of 10 to 50: 10 to 50
500 parts by weight (c) Low molecular weight propylene homopolymer resin having a number average molecular weight in the range of 2,000 to 20,000: 5 to 100 parts by weight (d) Mineral oil softener: 3 to 300 parts by weight, consisting of crystalline ethylene- A composition in which the weight ratio of low molecular weight propylene homopolymer resin to propylene block copolymer resin is 0.8 or less is prepared by using 0.5 to 15 parts by weight of a reactive alkylphenol/formaldehyde resin as a vulcanizing agent. An olefin-based thermoplastic elastomer composition obtained by highly vulcanizing an ethylene-α/olefin-nonconjugated diene copolymer rubber by vulcanization.