JP2691172B2 - Thermoplastic elastomer composition with excellent weather resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has a thermoplastic elastomer having excellent weather resistance, which contains a peroxide-crosslinking olefin copolymer rubber, an olefin plastic and a mineral oil softener as essential components. It relates to a composition.

(Prior Art) Thermoplastic elastomers are energy-saving and resource-saving vulcanized rubber substitutes, such as automobile parts (bumpers, bellows, fascias, interior seats, etc.), industrial machine parts (pressure hoses, gaskets, etc.), electronic parts, Widely used in various fields such as electrical equipment parts and building materials.

As this thermoplastic elastomer, one in which an olefin copolymer rubber such as EPDM is used as a rubber component is known, and further, various fillers can be easily dispersed in the elastomer to facilitate processing or a vulcanized rubber. It is also known to add a mineral oil-based softening agent for the purpose of lowering the hardness and increasing the flexibility and elasticity.

(Problems of Prior Art) However, when the above-mentioned mineral oil-based softening agent is blended with a thermoplastic elastomer, its type becomes a problem.
That is, a thermoplastic elastomer containing a mineral oil-based softening agent has good appearance and various other physical properties immediately after molding, but when used outdoors for a long time, a so-called chalking phenomenon (whitening phenomenon) occurs, and various physical properties It also has the drawback of decreasing.

Therefore, the present invention, even when used for a long time outdoors,
It is a technical object 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 uses a thermoplastic elastomer having a certain viscosity index as a mineral oil-based softening agent and when the rubber component thereof is partially crosslinked. It is based on the new finding that excellent weather resistance is imparted to the composition.

That is, according to the present invention, (a) peroxide cross-linking olefin copolymer rubber 90
To 10 parts by weight, (b) 10 to 90 parts by weight of olefinic plastic (where (a) + (b) is selected to be 100 parts by weight), and (c) the viscosity index (VI) is 110. A blend containing 3 to 100 parts by weight of a paraffinic mineral oil softening agent in the range of 140 to 140 as an essential component is dynamically heat treated in the presence of an organic peroxide to be partially crosslinked. A thermoplastic elastomer composition having excellent weather resistance is provided.

(Function) In the present invention, it is important to use a paraffinic mineral oil softener having a viscosity index (VI) in the range of 110 to 140 in order to obtain excellent weather resistance.

For example, as is clear from the results of Examples described below, in a thermoplastic elastomer composition (Comparative Example 1) containing a naphthenic mineral oil softener having a viscosity index of 75.8, JIS
Tensile strength at Sunshine Weather-O-based testing Z 2381 (T _B) and tensile retention of elongation at break (E _B) respectively
It is 62% and 43%, and the appearance is also marked by the chalking phenomenon (whitening).

Further, in the thermoplastic elastomer composition (Comparative Example 8) containing a mineral oil-based softening agent having a viscosity index of 80.7, the tensile strength (T _B ) retention rate was 89% and the tensile elongation at break (E _B ) retention was rate
Although it is improved to 75%, the appearance of whitening is still observed in the sunshine weatheraro test under the above conditions, and the occurrence of the chalking phenomenon cannot be completely avoided.

On the other hand, according to the present invention, in a thermoplastic elastomer composition (Example 1) containing a paraffinic mineral oil softener having a viscosity index of 130, a tensile strength (T _B ) retention rate of 92% was obtained in the same test. , Tensile elongation at break (E _B ) retention rate 79
%, Not only does it show excellent physical property retention, but also no whitening is observed in the appearance, and almost no change is observed when compared to the original one.

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

In the formula, L; 100 ° F (37.78 ° C) of standard low VI oil (VI = 0)
Kinematic viscosity (cst), H; kinematic viscosity at 100 ° F of standard high VI oil (VI = 100) (cs
t), U; viscosity (cst) of sample oil at 100 ° F.

That is, using the table of ASTM D2270-IP226,
The H-based oil and L-based oil having the same viscosity as the ° F (98.89 ° C) viscosity are obtained and calculated from the above formula (1).

If VI is 100 or more, it is calculated by the following formula.

In the formula, N is a number satisfying ν ₂₁₀ ^N = H / U, where ν ₂₁₀ represents the kinematic viscosity (cst) of the sample oil at 210 ° F, and H and U represent the above-mentioned meanings. .

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 was prepared using the mineral oil-based softening agent having a viscosity index of 80.6, the thermoplastic elastomer composition was not partially crosslinked by dynamic heat treatment (Comparative Example 7). Then, the retention rate of tensile strength (T _B ) when subjected to the sunshine weathering test is
73% and retention of elongation at break (E _B ) 64%
It is.

On the other hand, in the thermoplastic elastomer composition partially extruded according to the present invention (Example 3), the retention of tensile strength (T _B ) was 82% and the tensile strength (T _B ) was 82%. The retention rate of elongation at break (E _B ) is 75%, and it is recognized that the rate of improvement is about 10% or more.

In addition, although a whitening phenomenon (choking phenomenon) appears in appearance, a composition in which a mineral oil-based softening agent having the same viscosity index as in Comparative Example 7 is blended and partially crosslinked is performed (Comparative Example 10).
Shows that both the tensile strength retention rate and the tensile elongation at break retention rate are improved as compared with the composition of Comparative Example 7 in which partial crosslinking is not performed.

It is generally considered that deterioration of various physical properties and appearance of the thermoplastic elastomer due to outdoor use is caused by gelation of the rubber component.

According to the present invention, as described above, a mineral oil-based softening agent having a certain viscosity index is used and partially cross-linked by a preliminary dynamic heat treatment so that the subsequent Etostomer molded article is obtained. It is possible to effectively prevent gelation from being partially or locally used for the above, and thus effectively and surely prevent deterioration of various characteristics due to long-term use and the like.

(Preferred Embodiment of the Invention) (a) Peroxide Crosslinking Olefin Copolymer Rubber The peroxide crosslinking olefin copolymer rubber used in the present invention is, for example, ethylene-propylene-
Non-conjugated diene rubber, such as ethylene-butadiene copolymer rubber, is an amorphous elastic copolymer containing olefins as a main component, and is mixed with an organic peroxide and crosslinked by kneading under heating to have a fluidity. Rubber that decreases or does not flow. The non-conjugated diene refers to dicyclopentadiene, 1,4-hexadiene, dicyclopentadiene, methylene norbornene, ethylidene norbornene and the like.

Among these copolymer rubbers in the present invention, ethylene-propylene copolymer rubber, ethylene propylene-non-conjugated diene rubber, the molar ratio of ethylene units and propylene units (ethylene / propylene) is 50/50 to 90 / 10, particularly preferably 55/45 to 85/15, ethylene-propylene-non-conjugated diene copolymer rubber, especially ethylene-propylene-ethylidene norbornene copolymer rubber, weather resistance It is preferable in that a thermoplastic elastomer having excellent properties, tensile properties and impact resilience can be obtained.

Mooney viscosity of this copolymer rubber ML _{1 + 4} (100 ℃)
Is more preferably 10 to 250, particularly preferably 40 to 160. If it is less than 10, only a composition having poor tensile properties can be obtained. On the other hand, if it exceeds 250, the composition has poor flowability.

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

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

Specific examples thereof include isotactic and syndiotactic monoolefin polymer resins, and typical ones thereof are commercially available.

Examples of suitable mono-olefins are 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 can be mentioned.

In the present invention, the particularly preferable olefin-based plastic is a peroxide decomposition type olefin-based plastic.

What is peroxide decomposable olefin plastic?
It is mixed with peroxide and kneaded under heating to be thermally decomposed to reduce the molecular weight and increase the fluidity of the resin.This refers to an olefin plastic in which the fluidity of the resin increases. Propylene-ethylene copolymer, propylene-1-butene copolymer, propylene-1
-Hexene copolymer, propylene-4-methyl-1-pentene copolymer and the like. Melt index (ASTM-
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-based plastic plays a role of improving the fluidity and heat resistance of the composition.

(C) Mineral oil-based softening agent The mineral oil-based softening agent of this component (c) is usually compounded as a filler while weakening the intermolecular action force of the rubber to facilitate the roll processing when rolling the rubber. It is used for the purpose of facilitating dispersion of carbon black, white carbon, etc., and decreasing the hardness of vulcanized rubber to increase flexibility and elasticity. Generally, paraffinic, naphthenic and aromatic compounds are used. High boiling point petroleum fractions such as systems are used.

In the present invention, as described above, a paraffinic mineral oil having a viscosity index (VI) in the range of 110 to 140 is used as a softening agent.

Production of Thermoplastic Elastomer Composition The thermoplastic elastomer composition of the present invention comprises (a) a peroxide-crosslinking olefin-based copolymer rubber 90.
To 10 parts by weight, especially 90 to 40 parts by weight, (b) 10 to 90 parts by weight of olefinic plastic, especially
10 to 60 parts by weight (where (a) + (b) is selected to be 100 parts by weight), and (c) paraffinic mineral oil softener 3 to 100 parts by weight,
In particular, 5 to 60 parts by weight are blended, dynamically heat-treated in the presence of an organic peroxide, and partially crosslinked.

When the copolymer rubber component of the component (a) is used in a larger amount than the above range, the elastomer composition has poor moldability,
On the other hand, if the amount is small, rubber properties such as rubber elasticity will be unsatisfactory.

When the amount of the olefin-based plastic as the component (b) is larger than the above range, the elastomer composition becomes unsatisfactory in rubber-like properties such as rubber elasticity, and when the amount is small, the fluidity is deteriorated. Moldability deteriorates.

If the content of the component (c) mineral oil softener is larger than the above range, the resulting elastomer composition will be unsatisfactory in rubber properties, and if it is small, it will be unsatisfactory in molding processability. Become.

Further, a filler such as calcium carbonate, clay, kaolin, talc, silica, diatomaceous earth, mica powder, etc. within the range that does not impair the fluidity (moldability), rubber-like properties and thermal adhesiveness of the produced elastomer composition. Asbestos, alumina, barium sulphate, aluminum sulphate, calcium sulphate, basic magnesium carbonate, molybdenum disulfide, graphite, glass fibers, glass spheres, shirasu balloons, carbon fibers, etc. or colorants such as carbon black, titanium oxide, zinc white , Red iron oxide, ultramarine blue, navy blue, azo pigment, nitroso pigment, lake pigment, phthalocyanine pigment and the like can be added.

In the present invention, known heat stabilizers such as phenol-based, sulfite-based, phenylalkane-based, phosphite-based or amine-based stabilizers, antiaging agents, weathering stabilizers,
Antistatic agents, metal soaps, lubricants such as waxes, and the like can be compounded to the extent that they are used in olefin plastics or olefin copolymer rubbers.

In the present invention, the blend of each component described above is dynamically heat-treated in the presence of an organic peroxide to partially crosslink.

Dynamically heat treating means kneading in a molten state.

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

Of these, odor and scorch stability are 2,5.
-Dimethyl-2,5-di- (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di- (tert-butylperoxy) hexane-3,1,3-bis (tert-butyl) Peroxyisopropyl) benzene, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, and n-butyl-4,4-bis (tert-butylperoxy) valerate are preferable, among which 1,3 -Bis (tert
Most preferred is -butylperoxyisopropyl) benzene.

The blending amount of the organic peroxide is selected so as to be in the range of 0.05 to 3% by weight, preferably 0.1 to 1% by weight, based on the total amount of the components (a), (b) and (c). If the blending amount is less than the above range, the degree of crosslinking of the components (a) and (b) becomes too small, and as a result, the thermoplastic elastomer selected has rubber-like properties such as heat resistance, tensile properties, elastic recovery and impact resilience. The properties and strength are not sufficient. On the other hand, when used in a larger amount than the above range, the degree of crosslinking of the components (a) and (b) increases, resulting in deterioration of moldability of the thermoplastic elastomer.

In the present invention, sulfur, p-quinonedioxime, p, p '
-Dibenzoylquinone dioxime, N-methyl-N, N '
Peroxy crosslinking aids such as -m-phenylene dimaleimide, polyfunctional methacrylate monomers such as divinylbenzene, triallyl cyanurate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, acrylic methacrylate, vinyl butyrate. Polyfunctional vinyl monomers such as ates or vinyl stearates can be incorporated. With such a compound, a uniform and mild crosslinking reaction can be expected. In particular, in the present invention, when divinylbenzene is used, it is easy to handle and has good compatibility with the olefin-based plastic which is the main component of the object to be treated, and also has an organic peroxide solubilizing action, which aids dispersion of peroxide. Since it functions as an agent, a crosslinking effect by heat treatment is uniform, and a composition having a well-balanced fluidity and physical properties can be obtained, which is most preferable.

In the present invention, the compounding amount of such a crosslinking aid or a polyfunctional vinyl monomer is such that
The range of 0.1 to 2% by weight, particularly 0.3 to 1% by weight is preferable, and if the amount exceeds 2% by weight, when the amount of the organic peroxide is large, the crosslinking reaction proceeds, resulting in poor fluidity of the composition. However, if the amount of the organic peroxide is small, it is present in the composition as an unreacted onomer and changes in the physical properties may occur due to the thermal history during processing and molding of the composition, so excessive mixing should be avoided.

In order to accelerate the decomposition of organic peroxides, tertiary amines such as triethylamine, tributylamine, 2,4,6-tris (dimethylamino) phenol, aluminum, cobalt, vanadium, copper, calcium, zirconium, manganese, magnesium A decomposition accelerator such as naphthenate such as lead, mercury and the like can also be used.

As the kneading device, conventionally known devices such as an open mixing roll, a non-open Banbury mixer, an extruder, a kneader, and a continuous mixer can be used. Among these, it is preferable to use a non-open type apparatus, and it is preferable to knead under an atmosphere of an inert gas such as nitrogen or carbon dioxide. The kneading may be 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 170 to 240 ° C, for 1 to 20 minutes, preferably 3 to 10 minutes. The shear force applied normally at a shear rate of 10 to 10 ⁴ sec
^-1 , preferably 10 ² to 10 ³ sec ^-1 .

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

Also, because of its partial cross-linking, the melt flow rate (ASTMD 1238, 230 ° C) of the composition is generally 0.01 to 1
It is in the range of 00g / 10min, particularly in the range of 0.05 to 50g / 10min, and the moldability is extremely good.

The thermoplastic elastomer composition of the present invention is particularly excellent in weather resistance and moldability, and even when the molded product is subjected to long-term use outdoors such as strength, various physical properties such as strength and rubber elasticity are stable. It has the advantage of being retained.

(Example) Molding conditions and a test method for obtaining a test sample from the elastomer composition produced in each example are as follows.

(1) Injection molding Molding machine: Dynamelter (manufacturing machine) Molding temperature: 220 ℃ Injection pressure: Primary pressure 1300kg / cm ² Secondary pressure 700kg / cm ² Injection speed: Maximum molding speed: 90sec / cycle Gate: Direct gate (Land length 10 mm, width 10 mm, thickness 1 mm) Molded product: length 300 mm, width 180 mm, thickness 3 mm (2) Basic physical properties Test from a 3 mm thick square plate obtained by injection molding by the method of (1) A piece was punched out and measured by the following method.

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

(M100) Stress at 100% elongation (T _B ) Tensile strength (E _B ) Tensile elongation at break Spring hardness (HS): JIS A described in JIS K-6301
It was measured by the type method.

Permanent elongation (PS): 100% measured by the method of JIS K-6301
It was indicated by the residual elongation during elongation.

Heat-resistant temperature: Place the test piece in a constant temperature bath and keep the bath temperature at 20 ℃ / m.
The temperature was increased at a speed of in and the needle (diameter 0.8 mm) loaded with a load of 49 g penetrated 0.1 mm during the test.

Weather resistance: According to sunshine weatherro test. JIS Z 2
The method of 381 was performed under the following conditions.

Irradiation for 120 minutes, rainfall for 18 minutes Black panel temperature 63 ± 3 ℃ Appearance judgment is based on the following evaluation.

Score 1: Almost the same as the original.

2: A slight bleaching phenomenon is observed.

3: Whitening and choking phenomenon are observed.

After the test, the tensile strength (T _B ) and the tensile elongation at break (E _B ) were measured according to the method described above, and the residual ratios relative to the original values were shown.

Example 1 The following formulation, ethylene-propylene-ethylidene norbornene copolymer rubber 70 parts by weight Ethylene content 70 mol%, iodine value 15, Mooney viscosity ML _{1 + 4} (100 ° C) 60 or less Abbreviated as EPDM, polypropylene 30 parts by weight MFR (ASTM D 1238,230 ℃) 13g / 10min, density 0.91g / cm ³ or less Abbreviated as PP, carbon black 2 parts by weight or less HAF, paraffinic process oil 30 parts by weight Idemitsu Kosan PW-380 Specific gravity ( 15/4 ℃) 0.8769 color (ASTM, Saybolt) +30 Kinematic viscosity (cst) 381 (100 ° F), 30 (210 ° F) VI 130 Aniline point (° C) 144 or less Abbreviated as oil (1) Was mixed with a Banbury mixer in a nitrogen atmosphere at 180 ° C. for 5 minutes, passed through a roll, and pellets were produced with a sheet cutter.

Next, a solution obtained by dissolving and dispersing the pellets and 0.3 parts by weight of 1,3-bis (tert-butylperoxyisopropyl) benzene (hereinafter abbreviated as peroxide A) in 0.5 parts by weight of divinylbenzene (hereinafter abbreviated as DVB), And were mixed by a tumbler blender, and were evenly adhered to the surface of the solution pellet.

Then, the pellets were heated in an extruder under a nitrogen atmosphere at 210
Pellets of the intended elastomer composition were obtained by extruding at ° C.

Various properties of this composition were measured by the above-mentioned measuring methods, and the results are shown in Table 1.

Example 2 In the same manner as in Example 1 except that the polypropylene content was 20 parts by weight and 10 parts by weight of polyisobutylene was newly added, Esso Vistanex MML-100 (hereinafter abbreviated as PIB). To prepare an elastomer composition.

Comparative Example 1 In Example 1, as a process oil, a naphthene-based process oil manufactured by Idemitsu Kosan Co., Ltd. NS-24 Specific gravity (15/4 ° C) 0.9068 color (ASTM, Saybolt) L1.0 Kinematic viscosity (cst) 24.05 (100 ° F) ), 4.200 (210 ° F.) VI75.8 Alinine point (° C.) 69.6 or less Abbreviated as oil (3), an elastomer composition was prepared in the same manner as in Example 1.

Comparative Example 2 In Example 1, as the process oil, an aroma process oil AH-16 manufactured by Idemitsu Kosan Co., Ltd. Specific gravity (15/4 ° C) 0.9990 color (ASTM, Saybolt) 6.0 or more Kinematic viscosity (cst) 639.5 (100 ° F) An elastomer composition was prepared in the same manner as in Example 1 except that Oil (4), 15.11 (210 ° F) VI-130 or less, was used.

Example 3 An elastomer composition was prepared in the same manner as in Example 1 except that the compounding amount of EPDM was 50 parts by weight and the compounding amount of polypropylene was 50 parts by weight.

Comparative Examples 3 and 4 Example 2 except that oil (3) and oil (4) were used as process oils in Example 2, respectively.
An elastomer composition was prepared in the same manner as in.

Comparative Examples 5 and 6 An elastomer composition was prepared in the same manner as in Example 3 except that Oil (3) and Oil (4) were used instead of Oil (1).

Comparative Example 7 An elastomer composition was prepared in the same manner as in Example 3 except that the peroxide A and DVB were not blended and the dynamic crosslinking treatment was not performed.

Comparative Example 8 In Example 1, as a process oil, a naphthene-based process oil manufactured by Idemitsu Kosan NS-100 Specific gravity (15/4 ° C) 0.8906 color (ASTM, Seybolt) L0.5 Kinematic viscosity (cst) 94.91 (100 ° F) ), 9.458 (210 ° F) VI80.7 alinine point (° C) 106.1 or less, abbreviated as oil (2). An elastomer composition was prepared in the same manner as in Example 1.

Comparative Example 9 An elastomer composition was prepared in the same manner as in Example 3 except that the oil (2) was used as the process oil instead of the oil (1).

Comparative Example 10 An elastomer composition was prepared in the same manner as in Example 3, except that the oil (2) was used instead of the oil (1).

As is clear from the results of the above Examples and Comparative Examples, when the paraffinic oil (1) having a viscosity index (VI) in the range of 110 to 140 was used, the tensile strength (T _B ) And tensile elongation at break (E _B ), the whitening phenomenon does not appear, and the appearance hardly changes.

In the compositions of Comparative Example 8, Comparative Example 9 and Comparative Example 10 in which the oil (2) having a viscosity index (VI) of 80.7 was used, the retention rates of T _B , E _B, etc. were improved, but the whitening phenomenon was developed. Is observed, and the appearance is still insufficient.

Further, from the comparison between Example 3 and Comparative Example 7, in the present invention example in which partial cross-linking was performed, the tensile strength T _B and the tensile elongation at break E _B after the sunshine test were higher than those in the case of not performing it. It is understood that the retention rate has improved by about 10%.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-21145 (JP, A) JP 53-149241 (JP, A) JP 62-129332 (JP, A) JP 59- 207948 (JP, A) Japanese Patent Sho 56-8865 (JP, B2)

Claims (1)

(57) [Claims] 1. (a) 90 to 10 parts by weight of a peroxide-crosslinking olefin-based copolymer rubber, (b) 10 to 90 parts by weight of an olefin-based plastic (where (a) + (b) is 100 parts by weight) And (c) 3 to 100 parts by weight of a paraffinic mineral oil softening agent having a viscosity index (VI) in the range of 110 to 140, as an essential component, A thermoplastic elastomer composition having excellent weather resistance, which is characterized by being dynamically heat-treated in the presence of a peroxide and partially crosslinked.