JPH0260951A - Thermoplastic elastomer composition of excellent weathering resistance - Google Patents

Abstract

PURPOSE:To obtain the title composition improved in weathering resistance by partially crosslinking a specified blend by heating in the presence of an organic peroxide. CONSTITUTION:A blend is obtained by mixing 100 pts.wt. total of 90-10 pts.wt. peroxide-crosslinkable olefin copolymer (e.g., ethylene/butadiene copolymer rubber) of a Mooney viscosity of 10-250 and an iodine value <=18 and 10-90 pts.wt. olefin plastic (e.g., atactic PP) of an MI of 0.1-50 with 3-100 pts.wt. mineral oil-based softener (e.g., paraffinic process oil) of a viscosity index >=80. A mixture of this blend with 0.05-3wt.% organic peroxide (e.g., dicumyl peroxide and 0.1-2wt.% polyfunctional vinyl monomer (e.g., devinyl-benzene) is partially crosslinked by dynamically heating at 150-280 deg.C for 1-20min at a shear rate of 10-10<4>sec<-1> to obtain a thermoplastic elastormer composition of a hot toluene- insolubles content of 3-80wt.% and a melt flow rate of 0.01-100g/10min.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a thermoplastic material with excellent weather resistance, which contains a peroxide crosslinked olefin copolymer rubber, an olefin plastic, and a mineral oil softener as essential components. The present invention relates to elastomer compositions.

(Prior art) Thermoplastic elastomers are used as an energy-saving and resource-saving substitute for vulcanized rubber in automobile parts (bumpers, bellows, fascia 5 interior sheets, etc.), industrial machinery parts (pressure-resistant hoses, gaskets, etc.), and electronics. , electrical equipment parts,
Widely used in various fields such as building materials.

As this thermoplastic elastomer, those using olefin copolymer rubber such as EPDM as a rubber component are known, and furthermore, the elastomer can be easily processed and various fillers can be easily dispersed or vulcanized rubber can be used. It is also known to incorporate mineral oil-based softeners for the purpose of reducing the hardness and increasing flexibility and elasticity.

(Problems with the Prior Art) However, when a mineral oil softener as described above is blended into a thermoplastic elastomer, its weather resistance becomes a problem. In other words, a thermoplastic nidistomer containing a mineral oil-based softener has good appearance and various physical properties immediately after molding, but when used outdoors for a long period of time, a so-called chalking phenomenon (whitening phenomenon) occurs, and various physical properties deteriorate. It also has the disadvantage that it also decreases.

Therefore, even when used outdoors for a long time, the present invention
A technical problem is to provide a thermoplastic elastomer composition whose appearance and various physical properties are maintained at a constant level.

(Means for Solving the Problems) The present invention provides that when a mineral oil softener having a certain viscosity index is used and its rubber component is partially crosslinked, the thermoplastic elastomer This is based on the new finding that the composition has excellent weather resistance.

That is, the thermoplastic elastomer composition of the present invention comprises (a) peroxide crosslinked olefin copolymer rubber 90 to 1;
(b) Olefin plastic 10 to 90 parts by weight (
(where (a,) + (b) are selected to be 100 parts by weight), and (c) contains 3 to 100 parts by weight of a K oil-leveling softener as an essential component, ( (b) The mineral oil softener used has a viscosity index (Vt) of 80 or more, and (b) The blend containing each of the components (a) to (c) is an organic An important feature is that it is subjected to dynamic heat treatment in the presence of peroxide, resulting in partial crosslinking.

(Function) In the present invention, it is important to use a mineral oil softener having a viscosity index (Vl) of 80 or more in order to obtain excellent weather resistance.

For example, as is clear from the results of the examples described below, in the thermoplastic elastomer composition (Comparative Example 1) containing a mineral oil softener with a viscosity index of 75.8, JIS Z
The retention rates of tensile strength (T, ) and tensile elongation at break (Ea) in the Sunshine Weathero test based on 2381 were 62% and 43%, respectively, and the appearance also showed considerable chalking (whitening). .

On the other hand, in the thermoplastic elastomer composition (Example 2) containing a mineral oil-based softener with a viscosity index of 80.7 according to the present invention, the retention of tensile strength (Cho a) was was 89%, and the retention rate of tensile elongation at break (E8) was 75%, and it is recognized that the retention rate is significantly improved compared to the composition of the above-mentioned comparative example.

In the present invention, the viscosity index (Vl) is an index indicating the rate of viscosity change due to temperature change with respect to a constant reference oil, and is generally calculated by the following formula.

In the formula, L: reference paper Vl oil (VI=0) no 100°
Kinematic viscosity (cst) at F (37, 78 °C), H; Reference product Vl oil (VI = lOO) CD Kinematic viscosity (cst) at 100 °F, Ll; Viscosity of sample oil at 100' F (cs
t), is shown.

That is, using the table of 8 STM D 2270-IP 22B, find the viscosity of the sample oil at 210°F (98,89°C) and the H-based oil and L-based oil with the same viscosity, and calculate from the above formula (1). do.

In addition, for those whose Vl is 100 or more, it is calculated by the following formula.

In the formula, N is a number that satisfies ν21°N÷H/U,
Here, υ2. . indicates the kinematic viscosity (cst) of the sample oil at 210°F, and H and U have the meanings previously described.

It is also important that the thermoplastic elastomer composition of the present invention is partially crosslinked by dynamic heat treatment.

That is, when a thermoplastic elastomer composition is prepared using a mineral oil-based softener having a viscosity index of 80.6, a thermoplastic elastomer composition that has not been partially crosslinked by dynamic heat treatment (comparative example) 7), the retention rate of tensile strength (Ta) when subjected to the Sunshine Weathero test was 73%, and the retention rate of tensile elongation at break (EB) was 64%.

On the other hand, in the thermoplastic elastomer composition (Example 6) partially crosslinked according to the present invention, the retention rate of tensile strength (Ta) was 85%, and the tensile elongation at break was 85%. The retention rate of (Ea) was 76%, and it was recognized that both were improved by 10% or more.

It is generally believed that deterioration in various physical properties and appearance of thermoplastic elastomers due to outdoor use is due to gelation of the rubber component.

According to the present invention, as mentioned above, by using a mineral oil-based softener having a certain viscosity index and partially crosslinking it by dynamic heat treatment in advance,
Partial or local gelation of the elastomer molded product due to subsequent use is effectively prevented, and thus deterioration of various properties due to long-term use etc. is effectively and reliably prevented.

(Preferred embodiments of the invention) (a) Peroxide crosslinked olefin copolymer rubber The peroxide crosslinked olefin copolymer rubber used in the present invention is, for example, ethylene-propylene-nonconjugated diene rubber, ethylene-butadiene rubber, etc. An amorphous elastic copolymer mainly composed of olefins, such as copolymer rubber, which crosslinks when mixed with organic peroxide and kneaded under heat, resulting in decreased fluidity or no flowability. Refers to rubber. The non-conjugated diene includes dicyclopentadiene, 1,4-hexadiene, dicyclopentadiene, methylene norbornene, ethylidene norbornene, and the like.

Among these copolymer rubbers, ethylene-
Propylene copolymer rubber, ethylene-propylene non-conjugated diene rubber, which has a molar ratio of ethylene units to propylene units (ethylene/propylene) of 50,150 to 90.
/10, especially those with a ratio of 55/45 to 85/15 are preferably used, and among them, ethylene-propylene-nonconjugated diene copolymer rubber, especially ethylene-propylene-ethylidene norbornene copolymer rubber, has a heat-resistant sex,
This is preferable in that a thermoplastic elastomer with excellent tensile properties and impact resilience can be obtained.

Also, the Mooney viscosity ML of this copolymer rubber.

(at 100°C) is preferably 10 to 250, particularly 4 to 160. If it is less than 10, a composition with poor tensile properties will be obtained, while if it exceeds 250, the composition will have poor fluidity.

Further, the iodine value (degree of unsaturation) of the copolymer rubber is preferably 16 or less, and within this range, a thermoplastic elastomer with well-balanced fluidity and rubber properties can be obtained.

(b) Olefinic Plastics The olefinic plastics of component (b) consist of crystalline, high molecular weight solid products obtained from the polymerization of one or more monoolefins by either high pressure or low pressure processes.

Specifically, for example, isotactic and syndiotactic monoolefin polymer resins can be mentioned, and representative ones thereof can be obtained commercially.

Examples of suitable monoolefins include ethylene, 1-butene, 1-pentene, 1-hexene, 2-methyl-1-
Propene, 3-methyl-1-pentene, 4-methyl-1
-pentene, 5-methyl-1-hexene and the like.

Particularly preferred olefin plastics in the present invention are peroxide decomposition type olefin plastics.

Peroxide-decomposable olefin-based plastics are olefin-based plastics that are mixed with peroxide and kneaded under heat to thermally decompose, reduce the molecular weight, and increase the fluidity of the resin.For example, isotactic polypropylene and copolymers of propylene and small amounts of other α-olefins, such as propylene-ethylene copolymers,
Examples include propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-4-methyl-1-pentene copolymer, and the like. Melt index of olefin plastic to be mixed (ASTll
-D-1238-65T, 230°C) is preferably in the range of 0.1 to 50, particularly 5 to 20. In the present invention, the olefin plastic has the role of improving the fluidity and heat resistance of the composition.

(cl 糺 Belly plate ball akishin μ This component (c) mineral oil-based softener is usually used when rolling rubber, weakening the intermolecular force of the rubber to facilitate rolling processing, and also as a filler. Facilitates the dispersion of carbon black, white carbon, etc. to be blended,
It is also used for the purpose of reducing the hardness of vulcanized rubber and increasing its flexibility and elasticity, and generally high boiling point petroleum fractions such as paraffinic, naphthenic, and aromatic are used.

In the present invention, as already detailed, among these, the viscosity index (Vl) is 80 or more, preferably 100 to 1.
50, most preferably 110~! Use one in the range of 40.

(a) Peroxide crosslinked olefin copolymer rubber 9
0 to 10 parts by weight, especially 90 to 40 parts by weight, (b) 10 to 901 parts by weight of olefinic plastics,
In particular, 10 to 60 parts by weight (where (a) + (b) is 10 parts by weight)
0 parts by weight) and (c) 3 to 100 parts by weight, especially 5 to 60 parts by weight of a mineral oil softener, and dynamically heat treated in the presence of an organic peroxide, Manufactured by partial crosslinking.

If the copolymer rubber component (a) is used in an amount greater than the above range, the elastomer composition will have poor moldability, and if it is used in a smaller amount, the rubber properties such as rubber elasticity will be unsatisfactory.

If the amount of the olefin plastic (component (b)) is larger than the above range, the elastomer composition will have unsatisfactory rubber properties such as rubber elasticity, and if it is small, the fluidity will decrease, resulting in Formability deteriorates.

If the amount of the mineral oil softener (component (c)) is greater than the above range, the resulting elastomer composition will have unsatisfactory rubber properties, and if it is in a small amount, the moldability will be unsatisfactory. becomes.

Also, the fluidity (moldability) of the elastomer composition produced
, fillers such as calcium carbonate, clay, kaolin, within the range that does not impair the rubber properties and thermal adhesive properties.
Talc, silica, diatomaceous earth, snow powder, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, basic magnesium carbonate, molybdenum disulfide, graphite, glass fiber, glass bulb, shirasu balloon,
Carbon fibers or coloring agents such as carbon black, titanium oxide, zinc white, hengara, ultramarine, deep blue, azo pigments, nitroso pigments, lake pigments, phthalocyanine pigments, etc. can be blended.

The present invention also uses known heat stabilizers such as phenolic, sulfide, phenylalkane, phosphite or amine stabilizers, anti-aging agents, weather stabilizers, antistatic agents, lubricants such as metal soaps and waxes, etc. can be blended to the extent used in olefin plastics or olefin copolymer rubbers.

In the present invention, a blend of the above-mentioned components is dynamically heat treated in the presence of an organic peroxide to partially crosslink it.

Dynamic heat treatment means kneading in a molten state.

Examples of the organic peroxide used in the present invention include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-
butylperoxy)hexane, 2゜5-dimethyl-2,
5-di(tert-butylperoxy)hexane-3,
1,3-bis(tert-butylperoxyisopropyl)benzene, 1. I-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4- dichlorohensyl peroxyto, tert-butyl peroxybenzoate, t
Examples include ert-butyl perbenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butyl cumyl peroxide.

Among these, it ranks 2.5 in terms of odor and scorch stability.
-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2°5-di(tert-butylperoxy)hexane,
-butylperoxy)hexane 3.1.3-bis(te
rt-butylperoxyisopropyl)benzene, 1.
1-bis(tert-butylperoxy) -3,3,
5-trimethylcyclohexane, and n-butyl-4,
4-bis(tert-butylperoxy)valerate is preferred, and 1,3-bis(tert-butylperoxyisopropyl)benzene is most preferred.

The blending amount of this organic peroxide is (a), (bl
and (c) in a range of 0.05 to 3% by weight, preferably 0.1 to 1% by weight, based on the total amount of component (c). If this amount is less than the above range, fa
As a result of the degree of crosslinking of components ) and (b) being too low, the rubber properties and strength such as heat resistance, tensile properties, elastic recovery and impact resilience of the thermoplastic elastomer obtained are insufficient; When used in large amounts, the degree of crosslinking of components (a) and (b) increases, resulting in a decrease in moldability of the thermoplastic elastomer.

In the present invention, in the partial crosslinking treatment with the organic peroxide, sulfur, p-quinonedioxime, p, p'
-dibenzoylquinonesioxime, N-methyl-N,
Peroxy crosslinking coagents such as N'-m-phenylene dimaleimide or polyfunctional methacrylate monomers such as divinylbenzene, triallyl cyanurate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and acrylic methacrylate. Polyfunctional vinyl monomers such as , vinyl butyrald or vinyl stearate can be incorporated.

With such a compound, a homogeneous and mild crosslinking reaction can be expected. Particularly in the present invention, when divinylbenzene is used, it is easier to handle and the above-mentioned? It has good compatibility with olefin plastics, which are the main component of Il fillers, and has an organic peroxide solubilizing effect and acts as a peroxide dispersion aid, so the crosslinking effect by heat treatment is homogeneous and fluidity is improved. This is most preferable because a composition with well-balanced physical properties can be obtained.

In the present invention, the blending amount of such crosslinking aid or polyfunctional vinyl chloride is 0.
．． It is preferably in the range of 1 to 2% by weight, particularly 0.3 to 1% by weight. If the amount exceeds 2% by weight, the fluidity of the composition will deteriorate as a result of the crosslinking reaction progressing. On the other hand, if the amount of organic peroxide blended is small, it will exist in the composition as unreacted particles, and the physical properties may change due to the thermal history during processing and molding of the composition, so excessive blending is necessary. should be avoided.

In addition, in order to promote the decomposition of organic peroxides, triethylamine, tributylamine, 2,4゜6-tris (
It is also possible to use decomposition accelerators such as tertiary amines such as dimethylamino)phenol and naphthenates of aluminum, cobalt, vanadium, copper, calcium, zirconium, manganese, magnesium, lead, mercury and the like.

As the kneading device, conventionally known devices such as an open type mixing roll, a closed type Banbury Mixer 1 extruder, a kneader, and a continuous mixer can be used. Among these, it is preferable to use a closed type apparatus, and it is preferable to knead in an inert gas atmosphere such as nitrogen or carbon dioxide gas.

The crosstalk is carried out at a temperature at which the half-life of the organic peroxide used is less than 1 minute, usually 150 to 280°C, preferably 17°C.
It may be carried out at 0 to 240°C for 1 to 20 minutes, preferably 3 to 10 minutes. The applied shearing force is usually 10 to 10'5ec-', preferably 102-103 in terms of shear rate.
sec-'.

Thermoplastic Elastomer Composition In the thus obtained thermoplastic elastomer composition, the copolymer rubber of component (a) and the olefin plastic of component (b) are partially crosslinked by the above-mentioned dynamic heat treatment. The total amount of hot toluene insoluble matter (gel reagent) is usually in the range of 3 to 80% by weight, particularly 5 to 60% by weight.

Also, because it is partially crosslinked, the melt flow rate (ASTM D 1238.230°C) of the composition is generally 0. Ol~100g710min, especially 0.
The moldability is in the range of 05 to 5 Q g/lomin, and the moldability is extremely good.

The thermoplastic elastomer composition of the present invention has particularly excellent weather resistance and moldability, and various physical properties such as strength and rubber elasticity are stable even when the molded product is used outdoors for a long time. It has the advantage of being held.

(Example) From the elastomer composition produced in each example,
The molding conditions and test method for obtaining test samples are as shown below.

(1) Injection molding machine; Dynamelter (Awayo Seisakusho) Molding temperature: 22
0° C. Injection speed: Maximum molding speed: 90 sec/cycle (2) Basic physical properties A test piece was punched out from a 3 mm thick square plate obtained by injection molding using the method described in (1), and measured using the following method.

Tensile properties: Measured by the method of JIS K-6301.

(Mloo) Stress at 100% elongation (T8) Tensile strength (EB) Tensile elongation at break Measured by the bu method It is expressed as residual elongation at % elongation.

Heat resistant temperature: Place the test piece in a constant temperature bath and set the temperature of the bath to 20℃
The temperature was increased at a rate of 1/min, and the temperature was indicated as the temperature at which a needle (diameter 08 mm) with a load of 49 g penetrated 0.1 mm into the test piece.

Weather resistance, based on Sunshine weather test.

The test was carried out according to the method of JIS Z 2381 under the following conditions.

120 minutes of irradiation, 18 minutes of rain Black panel? M degree 63±3℃ Appearance judgment is based on the following evaluation.

After the test, the tensile strength (Tll) and tensile elongation at break (Ell) were measured according to the method described above, and the residual percentage relative to the original value was shown.

Example 1 The following formulation, ethylene content 70 mol%, iodine value 15, Mooney viscosity M L +, (100°C) 60 or less EP
Abbreviated as DM, polypropylene 30 parts by weight MFR (
8 STM D 1238, 230℃) 13g/10
m1n.

Density 0.91 g/cm3 Hereinafter abbreviated as PP, Carbon black 2m2 parts or less H
Abbreviated as AF, paraffin-based process oil 30 parts by weight pW-380 manufactured by Idemitsu Kosan Co., Ltd. Specific gravity (+5/4℃) 0.8769 Color (STM, Seibold) +30 Heavy viscosity (cst) 381 (100' F), 30
(210'F)Vl 130 Aniline point (℃) 144 Hereinafter abbreviated as oil (1), these were kneaded in a Banbury mixer for 5 minutes at taO℃ in a nitrogen atmosphere, passed through a roll, and then mixed with a sheet cutter. Manufactured a beret.

Next, the pellet and 0.3 parts by weight of 1,3-bis(tert-butylperoxyisopropyl)benzene (hereinafter abbreviated as peroxide A) were mixed with 05 parts by weight of divinylbenzene (hereinafter abbreviated as DVB).
The solution was mixed with a tumbler blender to uniformly adhere the solution to the surface of the pellet.

Next, this pellet was heated in an extruder under a nitrogen atmosphere at 210
A pellet of the desired elastomer composition was obtained by extrusion at .degree.

Each f1 characteristic of this composition was measured according to the measurement method described above, and the results are shown in Table 1.

Example 2 In Example 1, naphthenic process oil NS-100 manufactured by Idemitsu Kosan Co., Ltd. Specific gravity (+5/4°C) 0.8905 Color (8 STM, Seibold) L05 Heavy viscosity (cst) 94. gl (100°F), 9.
458 (210°F) Vl 80.7 Aniline point ('C) 106.1 An elastomer composition was prepared in the same manner as in Example 1, except that oil (2) was used.

Comparative Example 1 In Example 1, naphthenic process oil NS-24 manufactured by Idemitsu Kosan Co., Ltd. Specific gravity (15/4°C) 0.9068 Color (ASTM, Saybold) LL, 0 Thin viscosity (cst) 24. OH+00'F), 4.20
0 (210°F) Vl 75.8 Aniline point ('C) 69.8 An elastomer composition was prepared in the same manner as in Example 1 except that oil (3) was used.

Comparative Example 2 In Example 1, the process oil was aromatic process oil AH-16 manufactured by Idemitsu Kosan Co., Ltd. Specific gravity (15/4°C) 0.9990 Color (ASTM, Saybold) 80 or more Thin viscosity (cst) 6341.5 (100'F), 1B
An elastomer composition was prepared in the same manner as in Example 1, except that 1 l (210°F) Vl -130, hereinafter abbreviated as oil (4), was used.

Example 3 The same procedure as in Example 1 was carried out, except that in Example 1, the blending base of polypropylene was changed to 20 parts by weight, and 10i7i parts of polyisobutylene (vistanex MML-1α0 or less, abbreviated as PrB, manufactured by Esso Corporation) was newly blended. An elastomer composition was prepared.

Stream side 4. Comparative Examples 3 and 4 Elastomer compositions were prepared in the same manner as in Example 3, except that oils (2), (3), or (4) were used as the process oils, respectively.

An elastomer composition was prepared in the same manner as in Example 1 except that the amount of EPDM was changed to 501 parts by weight and the amount of polypropylene was changed to 50 parts by weight.

Example 6. Comparative Examples 5 and 6 In Example 5, oil (1) was replaced with oil (
Example 5 except that 2+, (3) or (4) was used.
An elastomer composition was prepared in the same manner.

Comparative Example 7 An elastomer composition was prepared in the same manner as in Example 5, except that peroxide A and DVB were not blended and the dynamic crosslinking treatment was not performed.

As is clear from the results of the above examples and comparative examples, oils (1) and (2) with a viscosity index (VI) of 80 or more
It is understood that weather resistance is dramatically improved when .

Furthermore, from a comparison between Example 5 and Comparative Example 7, the retention rate of tensile strength T8 and tensile elongation at break E8 after the sunshine test was found to be higher in the examples of the present invention in which partial crosslinking was performed compared to those in which partial crosslinking was not performed. It is understood that this has improved by about 10%.

Claims (2)

[Claims] (1) (a) 90 to 10 parts by weight of peroxide crosslinked olefin copolymer rubber, (b) 10 to 90 parts by weight of olefin plastic, (here (a) + (b) is 100 parts by weight) and (c) 3 to 100 parts by weight of a mineral oil-based softener having a viscosity index (VI) of 80 or more, as essential components. 1. A thermoplastic elastomer composition with excellent weather resistance, characterized in that it is dynamically heat treated and partially crosslinked. (2) The thermoplastic elastomer composition according to claim 1, wherein the mineral oil softener has a viscosity index of 100 or more.