JPH0311291B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a novel thermoplastic elastomeric molded product that has excellent filling properties, high temperature compression set, mechanical strength, oil resistance, and moldability, and has less stickiness on the surface of the molded product. be. In recent years, thermoplastic elastomers (hereinafter abbreviated as TPE), which are rubber-like soft materials that do not require a vulcanization process and have moldability similar to thermoplastic resins, have been used for automobile parts, home appliance parts, and electric wires. It is attracting attention in fields such as coatings, medical parts, footwear, and miscellaneous goods. Various types of polymers such as polyolefin-based, polyurethane-based, polyester-based, and polystyrene-based polymers have been developed and commercially available for such TPE. However, these TPEs do not reach the level of vulcanized rubber in terms of quality in the use of vulcanized rubber, which is one of the wide application fields of rubber, and therefore, they are not suitable for use in the vulcanized rubber field. Usage is extremely limited. For example, polyolefin TPE is a composite of polyolefin resin as a hard segment and polyolefin rubber as a soft segment by melt-kneading, or the rubber part is cross-linked during this melt-kneading process. Although it is inexpensive and has excellent heat resistance and weather resistance, it is not possible to obtain a soft material, and even the most flexible material cannot be obtained.
JIS-A hardness (JIS-K-6301) is about 70,
It is far too hard compared to the JIS-A hardness of 50 to 70 for general vulcanized rubber. In addition, JIS for polyolefin TPE
-The tensile strength in the low hardness region around A hardness 70 is
It is 25-45Kg/cm ² , which is considerably lower than the approximately 100Kg/cm ² for vulcanized rubber. Furthermore, regarding compression set at high temperatures, which is required in many vulcanized rubber applications these days,
The resistance of polyolefin TPE is approximately 55% at 100°C for 22 hours, which is significantly inferior to that of vulcanized rubber, which is approximately 40%. Polyester TPE and polyurethane TPE are also the most flexible commercially available products that meet JIS-A standards.
It has a hardness of 80 to 90, which is much harder than vulcanized rubber.
Not suitable for vulcanized rubber applications. Furthermore, polyester TPE is easily hydrolyzed and has poor hot water resistance.
On the other hand, polyester TPE has problems with moldability and heat resistance. On the other hand, polystyrene TPE based on styrene-butadiene block copolymer (SBC) or styrene-isoprene block copolymer (SIS)
are more flexible and have good rubber elasticity at room temperature than the other TPEs mentioned above, and TPE compositions obtained from them have excellent moldability. However, since this polymer has a double bond as a conjugated diene block in its molecule, it has problems in heat aging resistance (thermal stability) and weather resistance. By hydrogenating the intramolecular double bonds of a styrene and conjugated diene block copolymer, an elastomer with improved thermal stability can be obtained. In addition, several proposals have been made regarding TPE compositions using these hydrogenated substances.
The specifications of publications such as No. 50-14742 and No. 52-6551 disclose a TPE composition in which a hydrogenated styrene-conjugated diene block copolymer is blended with a hydrocarbon, an α-olefin polymer resin, etc. has been done. However, using these hydrogen additives
TPE composition has rubber elasticity (compression set) at high temperatures
It's bad. In order to improve this point, the present inventors have already proposed in Japanese Patent Application No. 57-13948 a crosslinkable composition obtained by silane-modifying a composition containing such a hydrogenated substance and a crosslinked product thereof. In addition, a special request was made in 1982.
-115543, in addition to this hydrogenated styrene-conjugated diene block copolymer, hydrocarbon oil, α-olefin copolymer resin, and inorganic filler, peroxide crosslinked olefin copolymer rubber We have proposed a method for producing a composition consisting of peroxide-crosslinked olefin rubber that is crosslinked. However, in the proposal of patent application No. 57-13948,
The complexity of the process of silane modification and post-crosslinking and TPE
It has the disadvantage of losing its recyclability, which is one of its characteristics. In addition, the product proposed in Japanese Patent Application No. 57-115543 has a compression set at high temperatures (100°C for 22 hours) with a hardness (JIS-A) of 60, which is as high as 50-55%, and also has excellent oil resistance and flexibility. However, there are problems in that the balance of strength and other properties may not be sufficient. On the other hand, the present inventors have developed a method based on hydrogenated derivatives of styrene-conjugated diene block copolymers.
In order to improve the high-temperature compression set of TPE compositions, we have been investigating the possibility of crosslinking with organic peroxides, in addition to the two previous applications. Regarding the partial crosslinking of compositions consisting of peroxide crosslinked polymers (for example EPDM) and peroxide crosslinked decomposable polymers (for example PP) with organic peroxides, there are already many known techniques in the field of polyolefin TPEs. To name a representative example, for example, Japanese Patent Application Laid-open No. 18943/1983 (first of all,
EPDM is cross-linked with organic peroxide and then PP
Melt and knead with etc. ), Japanese Patent Publication No. 53-34210 (Putting EPDM, PP, etc. and organic peroxide all at once into a kneader, and cross-linking them while melting and kneading.) After thorough melt-kneading, organic peroxide is added and cross-linked while further melt-kneading.), JP-A-Sho
Publication No. 53-149241 (in a similar operation to the method of JP-A-52-37953 mentioned above, when adding an organic peroxide, a certain amount of divinylbenzene is simultaneously added and crosslinked while melt-kneading), Unexamined Japanese Patent Publication 1987-
Publication No. 98248 (EPDM sufficiently melted and kneaded in advance)
A granular composition made of PP or the like is impregnated in an aqueous medium at a temperature at which the organic peroxide does not decompose, and then the temperature is raised to a temperature at which the organic peroxide decomposes to statically crosslink. )and so on. The present inventors have developed a TPE based on a hydrogenated derivative of styrene-conjugated diene block copolymer.
As a result of various studies on the organic peroxide crosslinking of the composition, we decided to pre-knead a mixture consisting of a hydrogenated derivative of styrene-conjugated diene block copolymer, a softener, a peroxide-decomposable olefin resin, and optionally an inorganic filler. Later, a method was developed in which organic peroxide or the like was added to partially crosslink the material. The present invention is particularly characterized in that a kneading step is provided first, and that a crosslinking aid and, in some cases, an antioxidant are simultaneously added at the same time as the organic peroxide is added. Only in this case can an elastomeric composition be obtained which is highly flexible and has excellent high temperature compression set, mechanical strength, oil resistance and moldability. Furthermore, it was found that the obtained molded product had less stickiness, which was an unexpected feature of the present inventors. While the proposals in the aforementioned five reports regarding olefin-based TPE are technologies aimed at slightly improving quality, the present invention focuses on the four technical requirements that make up the present invention, namely: (1) optimal blending composition; ,(2)
Before crosslinking, components (a) to (d) are sufficiently melt-kneaded, (3) a crosslinking aid is added during organic peroxide crosslinking, and (4) an antioxidant is optionally added during organic peroxide crosslinking. Only when all of these conditions are met can a partially crosslinked TPE that is highly flexible, has excellent high-temperature compression set, and has a good balance of other qualities be obtained. That is, in the present invention, after kneading a mixture consisting of the following (a) to (d) in advance, an organic peroxide, a crosslinking aid, and optionally an antioxidant are added to partially crosslink the resulting thermoplastic partially crosslinked product. The present invention relates to a method for producing an elastomer-like molded article, which comprises melt-molding it by a conventional method. (a) General formula A(-B-A)n (where A is a monovinyl-substituted aromatic hydrocarbon polymer block, B is a conjugated diene elastomeric polymer block, and n is an integer from 1 to 5) 100 parts by weight of a hydrogenated derivative of a block copolymer represented by d) Inorganic filler 0 to 900 parts by weight Component (a) Component (a) used in the present invention is obtained by hydrogenating a block copolymer represented by the general formula A(-B-A)n. In the above general formula, A is a monovinyl-substituted aromatic hydrocarbon polymer block, B is a conjugated diene elastomeric polymer block, and n is 1.
It is an integer of ~5. The monovinyl-substituted aromatic hydrocarbon monomer constituting the polymer block A is preferably styrene, and α-methylstyrene or the like may also be used. The conjugated diene monomer in polymer block B is preferably butadiene or isoprene, or may be a mixture of the two. When butadiene is used as the single conjugated diene monomer to form polymer block B, the block copolymer retains its elastomeric properties after being hydrogenated to saturate the double bonds. In order to achieve this, it is preferable to adopt polymerization conditions such that the 1,2-microstructure accounts for 20 to 50% of the microstructure in the polybutadiene block, and more preferably, the 1,2-microstructure accounts for 35 to 50% of the microstructure in the polybutadiene block.
45%. The number average molecular weight of polymer block A in the block copolymer is 5,000 to 125,000, and the number average molecular weight of block B is 15,000 to 125,000.
Preferably, it is in the range of 250,000. Many methods have been proposed for producing these block copolymers, but a typical method is, for example, the method described in Japanese Patent Publication No. 40-23798, using a lithium catalyst or Ziegler type. It can be obtained by block polymerization in an inert solvent using a catalyst. The hydrogenation treatment of these block copolymers is
For example, hydrogenation is carried out in the presence of a hydrogenation catalyst in an inert solvent by the method described in the specifications of Japanese Patent Publication No. 42-8704, Japanese Patent Publication No. 43-6636, or Japanese Patent Publication No. 46-20814. . In this hydrogenation,
At least 50%, preferably 80% or more of the olefinic double bonds in polymer block B are hydrogenated, and the aromatic unsaturated bonds in polymer block A are hydrogenated.
Less than 25% is hydrogenated. One such hydrogenated block copolymer is Ciel.
There is one commercially available from Chemical Company under the trade name "KRATON-G." Component (b) The rubber softener used as component (b) in the present invention is suitably a non-aromatic mineral oil or a liquid or low molecular weight synthetic softener. Mineral oil-based rubber softeners, commonly called process oils or extender oils, are used to soften, increase volume, and improve processability of rubber, and are a mixture of aromatic rings, naphthenic rings, and paraffin chains. Those in which the number of carbon atoms in the paraffin chain accounts for 50% or more of all carbons are called paraffinic, those in which the number of carbon atoms in the naphthene ring is 30 to 45% are called naphthenic, and those in which the number of aromatic carbons is more than 30%. are considered aromatic. The mineral oil-based rubber softener used as component (b) of the present invention is preferably a naphthenic or paraffinic one in the above category, and has an aromatic carbon number of 30%.
The above aromatic compounds are not preferred in terms of dispersibility in the composition with component (a). The properties of these non-aromatic rubber softeners include a kinematic viscosity of 20 to 500 cst at 37.8°C, a pour point of -10 to -15°C, and a flash point of 170 to 300°C. As the synthetic softener, polybutene, low molecular weight polybutadiene, etc. can be used, but the above-mentioned mineral oil-based softeners for rubber give better results. The blending amount of the softener as component (b) is 80 to 300 parts by weight, preferably 150 parts by weight, per 100 parts by weight of component (a).
~250 parts by weight. If the amount exceeds 300 parts by weight, the softener tends to bleed out, which may result in tackiness in the final product and may also reduce mechanical properties. On the other hand, if the amount is less than 80 parts by weight, there is no problem in practical use, but it is insufficient from an economic point of view and flexibility is also lost. Component (c) The peroxide-decomposed olefin resin used as component (c) in the present invention is a resin that is thermally decomposed by heat treatment in the presence of peroxide to reduce the molecular weight and increase the fluidity of the resin. Refers to olefin-based resins, such as isotactic polypropylene and copolymers of propylene and small amounts of other α-olefins, such as propylene-ethylene copolymers, propylene-1-butene copolymers, propylene-1-hexene copolymers, etc. Polymer, propylene-4-
Examples include methyl-1-pentene copolymer. MFR of the peroxide-decomposed olefin resin used (ASTM-D-1238-L conditions, 230
C) is preferably in the range of 0.1 to 50 g/10 minutes, particularly 0.5 to 30 g/10 minutes. The blending amount of component (c) is 30 parts by weight per 100 parts by weight of component (a).
-400 parts by weight; if it exceeds 400 parts by weight, the hardness of the resulting elastomeric composition becomes too high and flexibility is lost, making it impossible to obtain a product with a rubbery feel. A preferred formulation is 50 to 300 parts by weight. Additional Components (d) Additional components such as inorganic fillers may be added to the composition of the present invention, if necessary. Inorganic fillers not only have the benefit of reducing product costs as fillers, but also have positive effects on quality improvement (compression set, etc.). Examples of inorganic fillers include calcium carbonate,
Carbon black, talc, magnesium hydroxide, mica, clay, barium sulfate, natural silicic acid, synthetic silicic acid (white carbon), titanium oxide, etc. are available, and as carbon black, channel black, furnace black, etc. can be used. Among these inorganic fillers, talc, calcium carbonate and furnace black are economically advantageous and preferred. The amount of the inorganic filler blended is 0 to 900 parts by weight, preferably up to 500 parts by weight, based on 100 parts by weight of the hydrogenated derivative of component (a). If the amount exceeds 900 parts by weight, the mechanical strength of the composition will drop significantly, and the hardness will increase, resulting in a loss of flexibility, making it impossible to obtain a product with a rubbery feel. Manufacturing method The manufacturing method of the present invention consists of three steps. First, the first step is a step of kneading a blend consisting of components (a) to (d). The kneading method may be a method commonly used for rubber, plastic, etc., such as a single screw extruder, twin screw extruder, roll, Banbury mixer, or various kneaders. The second step is a step of partially crosslinking the composition obtained in the first step by adding an organic peroxide, a crosslinking aid, and optionally an antioxidant. There is a method of kneading using a machine or the like. Particularly when using a Banbury mixer, there is an advantage that the first step and the second step can be performed continuously. Another partial crosslinking method is a method in which peroxide etc. are impregnated into the pellet composition made of each component obtained in the first step in hot water, and then the temperature is raised to statically partially crosslink the composition (for example, Unexamined Japanese Patent Publication 1987-
98248 (publication specification)). The organic peroxide used in the second step may be either aromatic or aliphatic, and may be a single peroxide or a mixture of two types of peroxide. Specifically, 2,5-dimethyl 2,5-di(benzoylperoxy)-hexane,
t-Butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, t-butylcumyl peroxide, diisopropylbenzohydroperoxide, 1,3- Bis-(t-butylperoxyisopropyl)-benzene, benzoyl peroxide, etc. are used. In addition, crosslinking aids used in combination with the peroxide include acrylic polyfunctional monomers such as ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane triacrylate, etc., as well as divinylbenzene and liquid polybutadiene. . In addition, examples of antioxidants that may be used include (1) monophenol compounds, (2) bis,
Tris or polyphenol compounds, (3) thiobisphenol compounds, and (4) phenolic compounds consisting of polyvalent phenols or derivatives thereof, (5) naphthylamine compounds, (6) diphenylamine compounds, or (7) P - There are amine compounds such as phenylene diamine compounds. (1) Compounds belonging to monophenolic compounds include 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol,
Examples include 2,4-dimethyl-6-tert-butylphenol and 2,4,6-tri-tert-butylphenol. (2) Bis, tris or polyphenol compounds include 4,4-dihydroxydiphenyl,
2,2'-methylenebis(4-ethyl-6-tert
-crotylphenol), tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, tetrakis[methylene-3-(3',
Examples include 5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. (3) Thiobisphenol compounds include 4,4'-
Examples include thiobis(6-tert-butyl-3-methylphenol) and 2,2'-thiobis(6-tert-butyl-4-methylphenol). (4) Polyhydric phenols or their derivatives contain di-
Examples include tert-butylhydroquinone. (5) Naphthylamine compounds include phenyl-α
-Naphthylamine, etc. (6) Diphenylamine compounds include p-isopropoxydiphenylamine. (7) The p-phenylenediamine compound contains N,
N'-diphenyl-p-phenylenediamine,
Examples include N,N'-di-2-naphthyl-p-phenylenediamine. Among these, phenolic antioxidants (1), (2), and (3) are preferred. The amount of organic peroxide, crosslinking aid, and antioxidant used in the second step is 0.1 to 3 parts by weight of organic peroxide per 100 parts by weight of the composition consisting of components (a) to (d). (preferably 0.1 to 1 part by weight) Crosslinking aid 0.1 to 5 parts by weight (preferably 0.1 to 3 parts by weight) Antioxidant 3 parts by weight or less (preferably 1 part by weight or less), but in reality the components ( The proportions of a) to (d) are determined by taking into account the degree of crosslinking, which affects the quality of the resulting elastomeric composition. The amount of the crosslinking aid is generally preferably set at a molar ratio of about 1 to 3 times that of the organic peroxide. The degree of crosslinking [wt%] of the partially crosslinked elastomeric composition thus obtained was as follows for sample 1.
After wrapping the sample in a mesh wire mesh and extracting it with boiling xylene for 10 hours using a Soxhlet extractor, the remaining solid content is expressed as the ratio of the weight of the sample to 1 g of the sample. In the present invention, the preferable degree of crosslinking is in the range of 5 to 70% by weight based on the above measured values, and if it is less than 5% by weight, the resulting elastomeric composition will suffer from high temperature compression set, oil resistance, and stickiness of the molded product. It's bad. Moreover, if it exceeds 70% by weight, moldability deteriorates and at the same time, tensile elongation decreases. A particularly preferred degree of crosslinking is in the range from 10 to 60% by weight. The third step is a step of melt-molding the thermoplastic partially crosslinked product obtained through the first and second steps by a conventional method. When molding, pigments, heat stabilizers,
Additives such as antioxidants and UV absorbers can also be added. For the melt molding, conventional methods such as thermoplastic resin molding methods such as injection molding, extrusion molding, blow molding, and calendar molding can be applied. The field of use of the elastomeric molded article of the present invention is for various electric wire coatings (insulation, sheath), and industrial parts such as household appliance parts and automobile parts. Specific uses include various gaskets,
Flexible tube, hose cover, weather strip, flexible bumper, side bumper, molding,
Includes filler panels, lamp housings, wire cable coverings, air intake hoses, etc. Examples In these Examples and Comparative Examples, the test methods used for various evaluations are as follows. (1) Hardness [-] JIS-K-6301, A type. (2) Tensile strength [Kg/cm ² ] and tensile elongation [%] JIS-K-6301, the sample used was a 2 mm thick in-die extension sheet, and the test piece was No. 3 type. (3) Compression set [%] JIS-K-6301, 100℃, 22 hours, 25% deformation. (4) Oil resistance [%] JIS-K-6301, JIS No. 1 oil, volume change rate at 100℃ for 70 hours. (5) Injection moldability Injection molding machine: 5 oz in-line screw type. Mold: 100mm x 100mm x 2mm thick sheet Injection pressure: 500Kg/cm ² Injection temperature: 230℃ Mold temperature: 100× when injection molding is performed under conditions of 40℃ or higher
Injection moldability was judged to be good if it was possible to mold a sheet of 100 x 2 mm thick, without delamination or deformation, and without flow marks that significantly deteriorated the appearance. (6) Stickiness of molded product Two sheets of 100 x 100 x 2 mm thick each obtained by the above injection molding are stacked, a load of 1 kg is applied on top of them, and after being left at room temperature for 24 hours, the two sheets are separated. If no blocking was observed when the two sheets were removed and the two sheets were peeled off, the stickiness was judged to be good. (1) Component (a) KRATON-G1651 manufactured by Ciel Chemical Co., Ltd.
(Brookfield viscosity: 20% by weight toluene solution,
2000cps, 77〓) (2) Component (b) Diana Process Oil PW− manufactured by Idemitsu Kosan Co., Ltd.
380 [Paraffin-based, kinematic viscosity: 381.6cst (40℃)
30.1ocst (100℃), average molecular weight: 746, ring analysis: _CN
=27.0%・C _P =73.0%] (3) Component (c) PP-1: Polypropylene resin manufactured by Mitsubishi Yuka Co., Ltd.
MA-4〈MFR (230℃) 5.0g/10min, density 0.905
g/cm ³ 〉 PP-2: Propylene-ethylene copolymer resin manufactured by Mitsubishi Yuka Co., Ltd. BC-5C〈MFR (230℃) 2.8g/10
Min., density 0.905g/cm ³ 〉 PP-3: Propylene-ethylene copolymer resin SP-X 9800 (MFR (230℃) 1.5 manufactured by Mitsubishi Yuka Co., Ltd.)
g/10 min, density 0.892 g/cm ³ 〉 (4) Component (d) Calcium carbonate with an average particle size of 2.5 microns, surface-treated with higher fatty acid ester (5) Organic peroxide PO-1: Manufactured by NOF Corporation Niper B (benzoyl peroxide) PO-2: Perhexa 2,5B (manufactured by NOF Corporation) (2,
5-dimethyl-2,5-di(t-butylperoxy)hexane-3> (6) Crosslinking aid CA-1: Divinylbenzene CA-2: Trimethylolpropane triacrylate (7) Antioxidant AO-1 : Irganox manufactured by Ciba Geigy
1010〈Tetrakis〔methylene-3-(3',5'-di-
tert-butyl-4'-hydroxyphenyl)propionate [methane] AO-2: Nokrac White manufactured by Ouchi Shinko Chemical Co., Ltd. <N,N'-di-2-naphthyl-p-phenylenediamine> Example Implementation In Example 1, 100 parts by weight of component (a)
KRATON-G1651 and 190 parts by weight of PW-380 as component (b) were mixed in advance in a Henschel mixer for about 5 minutes, and then polypropylene MA-4 and BC5C were mixed as component (c) at 21.4 parts each. Add 143 parts by weight of calcium carbonate as component (d), mix for about 1 minute, blend at 200°C in a 40 mm diameter single screw extruder, and then
To 100 parts by weight of the obtained mixture, 0.3 parts by weight of organic peroxide (Niper B), 0.45 parts by weight of crosslinking aid (divinylbenzene) and 0.2 parts by weight of antioxidant (Irganox 1010) were added and mixed,
Next, the mixture was reacted in a 30 mm diameter twin-screw extruder at 200°C to obtain partially crosslinked thermoplastic elastomer pellets. This was injection molded and evaluated. The obtained molded product had a hardness of 55, little decrease in strength and elongation, and had good physical property variations such as oil resistance (22%), compression set (45%), and stickiness. Furthermore, Examples 2 to 8 were manufactured by the same method as Example 1, and the blending composition was the same as that of Example 1.
As shown in the table. As for quality, compression set, oil resistance, injection moldability, stickiness, etc. were all well balanced compared to Comparative Examples 1 to 6 below. Comparative Examples 1, 2 and 3 are Example 1,
The hardness corresponds to hardnesses of 2 and 7, and they were blended in a 30 mm diameter twin screw extruder according to the formulation shown in Table 1, and were not crosslinked. Comparative Example 4 has the same formulation as Example 1, but
Components (a) to (d) were not blended using an extruder before the crosslinking reaction, but blending and crosslinking were directly carried out at the same time using a 30 mm diameter twin screw extruder. Although this product had improved compression set, oil resistance, and stickiness compared to Comparative Example 1, its strength and elongation were low, and the appearance of the injection molded product was poor, such as spots appearing on the surface. It was bad. Comparative Examples 5 and 6 had the same formulation and manufacturing method as Example 1, but did not use a crosslinking aid. As can be seen from the gel fraction, these were almost at the same level as those without crosslinking, and there was no improvement in quality compared to Comparative Example 1. From the above, it can be seen that in the present invention, the effects of blending components (a) to (d) in advance in a kneader and then carrying out the crosslinking treatment and the combined use of the crosslinking aid are very large.

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Claims (1)

[Claims] 1(a) General formula A(-B-A)n (where A is a monovinyl-substituted aromatic hydrocarbon polymer block, B is a conjugated diene elastomeric polymer block, 100 parts by weight of a hydrogenated derivative of a block copolymer represented by (n is an integer from 1 to 5), (b) 80 to 300 parts by weight of a non-aromatic rubber softener, and (c) peroxide decomposition. Type olefin resin 30～
400 parts by weight is kneaded in advance, an organic peroxide, a crosslinking aid, and optionally an antioxidant are added to partially crosslink the mixture, and the thermoplastic partially crosslinked product is melt-molded by a conventional method. A method for producing an elastomeric molded article.