JPH0693142A - Partially crosslinked thermoplastic elastomer composition - Google Patents

Abstract

PURPOSE:To obtain a compsn. which is free from odor, resinous deposit and degradation in hue by thermally treating a mixture of a crystalline PP, an olefin copolymer rubber, a softener, a specific crosslinker. and a specific crosslinking aid under specified conditions to partially crosslink the mixture. CONSTITUTION:A mixture of 100 pts.wt. polymer component comprising 5-80wt.% crystalline PP (e.g. an ethylene-propylene block copolymer) and 95-20wt.% olefin copolymer rubber (e. g. an ethylene-propylene- ethylidenenorbornene copolymer rubber), 100 pts.wt. or lower softener (e.g. a mixture of a paraffinic and a naphthenic process oil), a peroxide crosslinker in an amt. of 0.015-0.045 pt.wt. based on 100 pts.wt. the sum of the polymer component and the softener, and a polyacrylate crosslinking aid in an amt. of 0.2-2.0 pts.wt. based on 100 pts.wt. the sum described above is thermally treated dynamically in an atmosphere contg. up to 0.1% oxygen and thereby partially crosslinked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partially crosslinked thermoplastic elastomer composition comprising polypropylene and a rubber component, and more particularly to a thermoplastic elastomer composition having little residual odor and eye blemishes and a small change in hue. .

[0002]

2. Description of the Related Art Thermoplastic elastomers are widely used as materials for filling an intermediate region between rubber and plastic, or as substitute materials for rubber, for automobile parts and the like. Various proposals have hitherto been made regarding such a thermoplastic elastomer. For example, JP-B-53-34210 discloses a thermoplastic blend obtained by partially curing a monoolefin copolymer rubber and a polyolefin plastic. The mono-olefin copolymer rubber is an elastomer such as ethylene-propylene copolymer rubber (EPR) or ethylene-propylene-non-conjugated diene copolymer rubber (EPDM), and the polyolefin plastic is polyethylene, polypropylene or the like. Partial curing takes place during dynamic conditions, ie during melt-kneading.

Japanese Patent Publication No. 54-2662 discloses that 40 to 90 parts by weight of a monoolefin copolymer rubber and 60 to 10 parts by weight of a crystalline polypropylene and / or a crystalline ethylene-propylene block copolymer are kneaded. Disclosed is a method for producing a thermoplastic elastomer, which comprises partially crosslinking in a molten state.

Further, Japanese Patent Publication No. 55-18448 discloses a blend of 25 to 85 parts by weight of a crystalline thermoplastic polyolefin resin and 75 to 15 parts by weight of a vulcanized monoolefin copolymer rubber, and 100 parts by weight of rubber. Disclosed is a thermoplastic elastomer-like composition containing 0 to 300 parts by weight of extender oil and the like.

A composition comprising a polyolefin resin and a partially cross-linked monoolefin copolymer rubber as described above has improved tensile properties, flexibility, impact resilience, etc., but has good moldability and long-term heat stability. There is a problem that the sex is insufficient.

As a solution to such a problem, 5 to 40% by weight of polyisobutylene and / or isobutylene-isoprene copolymer rubber, ethylene-propylene copolymer rubber and / or ethylene-propylene-non-conjugated diene terpolymer are used. A thermoplastic elastomer composition (Japanese Patent Publication No. 54-23702) comprising 30 to 90% by weight of the original copolymer rubber and 5 to 40% by weight of a polyolefin resin, and (a) a peroxide crosslinkable olefin copolymer rubber 90 to 40 parts by weight and (b) 10 to 60 parts by weight of peroxide decomposition type olefinic plastic ((a)
+ (B) is 100 parts by weight), and (c) non-peroxide type hydrocarbon-based rubber-like substance and / or (d) mineral oil-based softener
A method for producing a partially crosslinked thermoplastic elastomer composition, characterized in that a mixture consisting of 100 parts by weight is dynamically heat treated in the presence of an organic peroxide.
-15741) was proposed. Incidentally, typically, the peroxide cross-linking olefin copolymer rubber (a) is ethylene-propylene copolymer rubber or ethylene-propylene-non-conjugated diene copolymer rubber, peroxide decomposition type olefin plastic (b) Is isotactic polypropylene, and the peroxide-non-crosslinked hydrocarbon-based rubber-like substance (c) is polyisobutylene or butyl rubber.

Further, Japanese Patent Publication No. 62-59139 describes (a) 50 to 90 parts by weight of a peroxide-crosslinking olefinic copolymer rubber, (b)
10 to 50 parts by weight of peroxide cross-linking type polyolefin resin (where (a) + (b) is selected to be 100 parts by weight),
If necessary, (c) non-crosslinking hydrocarbon-based rubber-like substance and / or (d) a maximum of 100 parts by weight of a mineral oil-based softener, (e) organic peroxides (a), (b) and (c). ) 0.05 to 1% by weight based on the total amount of the components,
0.07 to 2% by weight based on the total amount of the components (b) and (c), and
(g) Peroxide non-crosslinked polyolefin resin 10 to 100
Disclosed is a thermoplastic elastomer obtained by dynamically heat treating parts by weight.

[0008]

However, in each of the above-mentioned compositions, a crosslinked structure is formed by using a large amount of a peroxide crosslinking agent, and the residual peroxide after crosslinking, peroxide decomposed product and polymer are used. There is a problem that when the composition is molded into a sheet or the like, the surface of the composition is roughened due to the generation of eyes and eyes due to the influence of the decomposed products. In addition, there are problems such as deterioration of hue due to oxidation and generation of odor. Especially when used for building materials, interior materials for automobiles, etc., the problem of residual odor is serious.

Therefore, an object of the present invention is to provide a partially crosslinked thermoplastic elastomer composition which has little residual odor and generation of eye blemishes, little change in hue, and good moldability and tensile strength.

[0010]

As a result of earnest research in view of the above problems, the present inventors have found that crystalline polypropylene, an olefin copolymer rubber, a softening agent, a peroxide crosslinking agent, and a crosslinking assistant. In the composition system containing the agent, without reducing the crosslinking efficiency of the olefin-based copolymer rubber, to reduce odor, eyes, and hue change,
The addition amount of peroxide crosslinking agent is extremely small, and a predetermined amount of polyvalent acrylate crosslinking agent is added.
Furthermore, they have found that it is sufficient to heat-treat each of these components dynamically under a low oxygen concentration, and arrived at the present invention.

That is, the partially crosslinked thermoplastic elastomer composition of the present invention comprises (a) 5 to 80% by weight of crystalline polypropylene and (b) 95 to 20% by weight of olefin copolymer rubber.
And (a) + (b) total 100 parts by weight, (c) softener 100 parts by weight or less, and (a) + (b) + (c) total 10 parts by weight.
With respect to 0 part by weight, (d) a peroxide-based crosslinking agent 0.015
~ 0.045 parts by weight, and (e) polyvalent acrylate crosslinking aid 0.
2 to 2.0 parts by weight, and the oxygen concentration of each component 0.1
%, And is partially crosslinked by dynamically performing heat treatment.

The present invention will be described in detail below. First, each component of the partially crosslinked thermoplastic elastomer composition of the present invention will be described. (a) crystalline polypropylene propylene homopolymer or ethylene, 1-butene,
It is a random or block copolymer containing propylene as a main component, which is a copolymer of α-olefins such as 1-pentene, 1-hexene, and 4-methyl-1-pentene. Its melt flow rate (MFR, 230 ° C, 2.16 kg load) is 0.
3 to 300 g / 10 minutes, particularly 10 to 100 g / 10 minutes are preferable. In the case of the copolymer, the propylene content is 60% by weight or more.
Thus, in the present specification, the term "crystalline polypropylene" means not only a propylene homopolymer but also a copolymer.

Crystalline polypropylene has the highest melting point among polyolefins and contributes to improvement of heat resistance and mechanical strength of the composition.

(B) Olefin-based copolymer rubber ethylene, propylene, 1-butene, 1-hexene, 4
-Methyl-1-pentene and other two or more copolymer rubbers, and two of the above-mentioned monoolefins (preferably ethylene and propylene) and dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, A copolymer rubber with a non-conjugated diolefin such as methylene norbornene or ethylidene norbornene or a conjugated diolefin such as butadiene or isoprene is included. Typically, ethylene-propylene copolymer rubber (EP
R), ethylene-butene copolymer rubber (EBR) and ethylene-propylene-diene copolymer rubber (EPDM)
Etc. These olefinic copolymer rubbers may be used alone or in combination of two or more kinds.

The ethylene content of such olefinic copolymer rubber is preferably 35 to 88% by weight, the iodine value (unsaturation degree) is 30 or less, and the Mooney viscosity ML _{1 + 8.}
(127 ° C) is preferably 5 to 300. The crystallinity of such an olefinic copolymer rubber is usually 40% by weight or less. The olefin-based copolymer rubber is present as a partially crosslinked rubber in the composition and improves its heat resistance rigidity, impact resistance, flexibility and the like.

The compounding ratio of (a) the crystalline polypropylene and (b) the olefinic copolymer rubber as described above is 5 to 80% by weight of the (a) crystalline polypropylene, with the total amount of the two being 100% by weight. %, Preferably 10 to 50% by weight,
(b) The olefin-based copolymer rubber is 95 to 20% by weight, preferably 90 to 50% by weight. When the crystalline polypropylene is less than 5% by weight (when the olefin copolymer rubber exceeds 95% by weight), the mechanical strength decreases, while when the crystalline polypropylene exceeds 80% by weight (the olefin copolymer rubber 20% by weight). If less than), the physical properties of rubber are deteriorated.

(C) Softening agent The softening agent is a high boiling point petroleum fraction used for the purpose of weakening the intermolecular force of the elastomer component, facilitating processing, and improving flexibility, elasticity and moldability, It is classified into paraffin type, naphthene type and aromatic type. It is preferable to use one kind or a mixture of two or more kinds of these softening agents.

The blending amount of the above-mentioned mineral oil type softening agent is 100 in total of crystalline polypropylene + olefin type copolymer rubber.
100 parts by weight or less, preferably 5 to 50 parts by weight,
Parts by weight.

(D) Peroxide-based cross -linking agent As the peroxide-based cross-linking agent, there are hydro-based, dialkyl-based, ketal-based, ketone-based, carbonate-based, ester-based, etc., and examples thereof include dicumyl peroxide and di-t. -Butyl peroxide, 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,1,
3-bis (t-butylperoxyisopropyl) benzene, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4,4-bis (t
-Butylperoxy) valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-
Dichlorobenzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, t-butyl cumyl peroxide and the like can be mentioned.

The amount of the above-mentioned (d) peroxide-based cross-linking agent is 0.01 part with respect to a total of 100 parts by weight of (a) crystalline polypropylene + (b) olefin-based copolymer rubber + (c) softener.
It is 5 to 0.045 parts by weight, preferably 0.02 to 0.04 parts by weight. If the peroxide-based crosslinking agent is less than 0.015 parts by weight,
Insufficient crosslinking of the olefin copolymer rubber,
If it exceeds 0.045 parts by weight, not only the hue is deteriorated, eyes and odor are generated, but also mechanical properties are deteriorated.

(E) Crosslinking aid In the present invention, a polyvalent acrylate crosslinking aid is used as the crosslinking aid because it prevents toxicity, workability, crosslinking efficiency, and deterioration of hue, odor, and eyes. use.

Examples of the polyvalent acrylate crosslinking aid include polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, and 2,2-.
Bis [4- (acryloxydiethoxy) phenyl] propane, 2,2-bis [4- (acryloxypolyethoxy) phenyl] propane, 2,2-bis [4- (acryloxypolypropoxy) phenyl] propane and 2- Diacrylate-based crosslinking aids such as hydroxy-1-acryloxy-3-methacryloxypropane, triacrylate-based crosslinking aids such as trimethylolpropane trimethacrylate, tetramethylolmethane trimethacrylate, trimethylolpropane triacrylate and tetramethylolmethane triacrylate. Agents, tetramethylolmethane tetraacrylate, dipentaerythritol hexaacrylate, and other acrylate-based crosslinking aids having a valence of 4 or more. Of these, trimethylolpropane trimethacrylate is particularly preferable.

The amount of the above-mentioned crosslinking aid compounded is 0.2 to 2.0 parts by weight, preferably 0.2 to 2.0 parts by weight, based on 100 parts by weight of the total of (a) crystalline polypropylene + (b) olefinic copolymer rubber + (c) softening agent. Is 0.3 to 1.5 parts by weight. If the amount of the cross-linking aid is less than 0.2 parts by weight, the crosslinking of the olefinic copolymer rubber is insufficient, and if it exceeds 2.0 parts by weight, poor dispersion of the cross-linking aid causes uneven cross-linking. The physical properties deteriorate.

(F) Other components Furthermore, in the present invention, if necessary, stabilizers such as antioxidants, ultraviolet absorbers, metal deterioration inhibitors, lubricants, antistatic agents, electrical property improvers, flame retardants, A processability improver, an additive such as a pigment, an inorganic filler such as talc, calcium sulfate, barium sulfate, mica, calcium silicate and the like can be added.

The partially crosslinked thermoplastic elastomer composition of the present invention can be produced by mixing the components described above and melt-kneading in an atmosphere having an oxygen concentration of 0.1% or less. If the oxygen concentration exceeds 0.1%, odor is generated and a large amount of eyes and eyes are generated. As a kneading device, a conventionally known device such as a non-open type Banbury mixer, an extruder (including a twin screw), a kneader, and a continuous mixer can be used. In such a device, a device for ejecting an inert gas such as N ₂ gas is provided below the hopper for supplying the raw material, and the inert gas is ejected from the device into the kneading device to remove the air in the kneading device from the inert gas. And the raw material is supplied while ejecting an inert gas, the melt kneading can be performed in an atmosphere having an oxygen concentration of 0.1% or less.

The kneading is carried out at a temperature at which the half-life of the peroxide-based cross-linking agent used is less than 1 minute (normally barrel temperature 130-
280 ° C., preferably 160 to 250 ° C.) for 0.1 to 10 minutes, preferably 0.2 to 3 minutes. In the present invention, the preferred method for mixing and kneading the components is to use a twin-screw extruder and melt crystalline polypropylene, olefin-based copolymer rubber, peroxide-based cross-linking agent, cross-linking aid and softener. Knead.

The partially crosslinked thermoplastic elastomer composition of the present invention obtained in this manner exhibits a good degree of crosslinking, and hardly causes odor or eyes, and does not deteriorate the hue. Such a partially crosslinked thermoplastic elastomer composition of the present invention can be molded by an apparatus used for ordinary thermoplastics, and is suitable for extrusion molding, calender molding, and particularly injection molding.

[0028]

The partially crosslinked thermoplastic elastomer composition of the present invention is a composition system containing crystalline polypropylene, an olefinic copolymer rubber, a softening agent, a peroxide crosslinking agent, and a crosslinking aid, A total of 100 of crystalline polypropylene, olefinic copolymer rubber, and softener
With respect to parts by weight, 0.015 to 0.10 peroxide type crosslinking agent.
With a very small amount of 045 parts by weight, a specific amount of a specific cross-linking aid is added, and each of these components is dynamically heat-treated under a low oxygen concentration, so that the cross-linking structure is sufficiently formed. However, there is almost no generation of odor or eyes and deterioration of hue.

Although the reason why such an effect is obtained is not always clear, even if the addition amount of the peroxide type crosslinking agent is small, a specific amount of the specific crosslinking aid is added, and further, each of these components is reduced. By melt-kneading under an oxygen concentration, a cross-linking structure is efficiently formed by the peroxide-based cross-linking agent, and thus peroxide does not remain after cross-linking, and further, peroxide decomposition products and polymer decomposition products are not generated. It is believed that there is.

[0030]

The present invention will be described in more detail by the following examples. The following raw material components were used in each of the examples and comparative examples. [1] Crystalline polypropylene propylene-ethylene block copolymer BPP: [BJ520 manufactured by Tonen Chemical Co., Ltd., density 0.90 g /
cm ³ , melt flow rate (MFR, 230 ° C, 2.16 kg load) 20 g / 10 minutes, ethylene content 7% by weight] [2] Olefin-based copolymer rubber Ethylene-propylene-ethylidene-norbornene copolymer rubber EPDM: [ Made by Nippon Synthetic Rubber Co., Ltd. EP57P, Mooney Clay ML _{1 + 4} (100 ° C) = 88, iodine value 15.0, propylene content 28% by weight] [3] Softener naphthenic and paraffinic mixed process oil softener: [Exxon Chemical Co., Ltd., Flexon 876] [4] Peroxide type cross-linking agent (POX) 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 [5] Cross-linking aid trimethylol Propane trimethacrylate (TMP
T) Divinylbenzene (DVB)

Examples 1 to 4 and Comparative Examples 1 to 7 25 parts by weight of crystalline polypropylene (a), 75 parts by weight of olefinic copolymer rubber (b), and the amount of peroxide-based crosslinker shown in Table 1. A twin-screw extruder (58 mm φ) having a N ₂ gas jetting device at the bottom of the hopper is added to the agent and a crosslinking aid, and the N ₂ gas is jetted to blow the air in the extruder to the N ₂ gas. After substituting with, the melt kneading was carried out for 0.2 to 3 minutes at 250 rpm at a barrel temperature of 200 ° C. while continuing to spout N ₂ gas. After kneading, add a softening agent at a barrel temperature of 200 ° C for 20-
The mixture was melt-kneaded for 30 seconds, and this kneaded product was cut into a sheet and pelletized.

The composition of the partially crosslinked thermoplastic elastomer composition thus obtained and the oxygen concentration immediately below the hopper are shown in Table 1.

Next, each test piece was molded from the obtained pellets, and the gel fraction, tensile strength, tensile elongation and hue were measured.
Also, the generation of odor and eyes was evaluated. The results are shown in Table 2.

Table 1 Composition (parts by weight) Example 1 Example 2 Example 3 Example 4 BPP 25 25 25 25 EPDM 75 75 75 75 Softener 10 10 10 10 POX^* 0.02 0.04 0.03 0.03 TMPT^* 0.5 0.5 0.5 1.0Oxygen concentration in the extruder just below the hopper (%) 0.05 0.05 0.10 0.05

[0035]

Table 1 (continued)Composition (parts by weight) Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 BPP 25 25 25 25 EPDM 75 75 75 75 Softener 10 10 10 10 POX^* 0.03 0.03 0.03 0.03 TMPT^* 0.5-0.1 2.5 DVB^* − 0.5 − − Oxygen concentration in the extruder just below the hopper (%) twenty one^** 0.15 0.05 0.05 Note) *: Addition amount per 100 parts by weight of BPP + EPDM + softening agent in total. **: N₂Does not eject gas (oxygen concentration in air).

Table 2 Composition (parts by weight) Example 1 Example 2 Example 3 Example 4 Gel fraction⁽¹⁾ 26 34 27 36 Tensile strength⁽²⁾ 52 60 57 62 Tensile elongation⁽³⁾ 380 355 360 370 Odor^(Four) ○ ○ ○ ○^(Five) ○ ○ ○ ○ Hue⁽⁶⁾ 6.0 6.8 7.0 8.1

[0038]

Table 2 (continued) Composition (parts by weight) Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Gel fraction ⁽¹⁾ 0.2 8 10 70 Tensile strength ⁽²⁾ 10 19 24 89 Tensile elongation ^{( 3)} 500 300 340 95 Odor ⁽⁴⁾ ○ × ○ ○ Eyes ⁽⁵⁾ ○ △ ○ ○ Hue ⁽⁶⁾ 30.1 − 6.1 6.7

(1) Gel fraction: Calculated from the weight ratio of the residue after the composition was heat-treated in boiling paraxylene for 12 hours and the initial composition (unit:% by weight). (2) Tensile strength: Measured according to JIS K6310 (Unit is kgf / c
m ² ). (3) Tensile elongation: Measured according to JIS K6310 (unit is%). (4) Odor: 3 compositions (standard sample) containing no peroxide-based crosslinking agent and crosslinking aid, and 1 composition of each Example and Comparative Example (comparative sample) Evaluation by the following criteria by sensory test method by comparative panel test. ◯: 12 or more out of 15 panelists judged that there was no difference in odor between the comparative sample and the standard sample, and the odor was slight or odorless. ×: 12 or more out of 15 panelists judged that the comparative sample had a stronger odor than the standard sample. Δ: Less than 12 people judged that there was no difference in odor between the standard sample and the comparative sample, and less than 12 people judged that the comparative sample had a stronger odor than the standard sample. (5) Eye and eye: The eye and eye means that after the composition is formed into a sheet, the volatile components in the composition adhere to the surface of the sheet and roughen the surface of the sheet. The degree of eye and eye is evaluated according to the following criteria. . ◯: Eyes and eye rash have not occurred for more than 72 hours. Δ: Eyes and eyes were observed in 12 to 72 hours. X: Eye blemishes occurred within 6 hours. (6) Hue: Displays the yellowness index (YI) measured according to JIS K7105.

As is clear from Table 2, the partially crosslinked thermoplastic elastomer composition of the present invention has an appropriate gel fraction, is excellent in mechanical strength such as tensile strength and tensile elongation, and has an odor. It had a good balance of physical properties such as no blemishes and low yellowness.
On the other hand, the compositions of each comparative example had a problem that odor and eyes were remarkably generated, mechanical strength was poor, and gel fraction was low.

[0042]

As described in detail above, the partially crosslinked thermoplastic elastomer composition of the present invention comprises a crystalline polypropylene, an olefin copolymer rubber, a softening agent, a peroxide crosslinking agent, and a crosslinking aid. In the composition system containing and, with respect to the total 100 parts by weight of the crystalline polypropylene, the olefin-based copolymer rubber, and the softening agent, the peroxide-based crosslinking agent is 0.015 to 0.045 parts by weight, which is extremely small. Since a predetermined amount of polyvalent acrylate is added as a cross-linking aid, and these respective components are melt-kneaded under a low oxygen concentration, even if the cross-linking structure is sufficiently formed,
Almost no odor, eyes, or deterioration of hue.

The partially crosslinked thermoplastic elastomer composition of the present invention as described above is suitable as a substitute for elastomers such as polyurethane, particularly for building materials, interior materials for automobiles, and housings for household electric appliances.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masakatsu Suetsugu 3-1, Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Tonen Kagaku Co., Ltd. Technology Development Center

Claims (1)

[Claims] 1. (a) 5 to 80% by weight of crystalline polypropylene
And (b) 95 to 20% by weight of the olefinic copolymer rubber and 100 parts by weight of the total of (a) + (b), (c) the softening agent 10
0 parts by weight or less, and (d) a peroxide-based cross-linking agent 0.015 to 0.04 per 100 parts by weight of the above (a) + (b) + (c).
5 parts by weight, and (e) a polyvalent acrylate crosslinking agent 0.2 to 2.
A partially cross-linked thermoplastic elastomer composition containing 0 part by weight and dynamically cross-linking each of the above components in an atmosphere having an oxygen concentration of 0.1% or less.