JPH056577B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a thermoplastic elastomer, and more particularly to a partially crosslinked olefin thermoplastic elastomer with excellent thin film formability. Technical background Generally, rubber products are widely used in various fields where elasticity, flexibility, etc. are particularly required, but they have problems in the production process such as the need for vulcanization during molding. Since it is not suitable for mass production, alternatives to rubber that can be molded without vulcanization and have properties similar to rubber are being considered. Soft plastics such as soft vinyl chloride resin, ethylene-vinyl acetate copolymer, and low-density polyethylene are known as materials with properties similar to rubber, but these have good moldability and flexibility. Although it has the advantage of being rich in properties, it has disadvantages such as poor heat resistance, mechanical strength, and impact resilience, which greatly limits its use. Attempts have also been made to improve heat resistance and mechanical strength by mixing soft plastics with plastics with a high melting point, such as high-density polyethylene or polypropylene, but this results in a loss of flexibility and the need for extrusion molding or injection molding. Sink marks occur during molding, making it impossible to obtain a good product. Therefore, so-called thermoplastic elastomers have recently attracted attention as having performance intermediate between vulcanized rubber and soft plastics. As such a thermoplastic elastomer, the present inventors first dynamically heat-treated a peroxide crosslinked olefin copolymer rubber, a peroxide crosslinked polyolefin resin, an organic peroxide, a crosslinking aid, and a peroxide non-crosslinked polyolefin resin. The resulting thermoplastic elastomer was proposed (Japanese Patent Application Laid-open No. 71739/1983). This thermoplastic elastomer has excellent heat resistance, tensile properties, weather resistance, flexibility, and rebound resilience, and can be easily molded into products without flow marks by extrusion molding or injection molding, making it suitable for molding large and thick products. Although it is very satisfactory, its thin film formability is still insufficient, and it is still not fully satisfactory for applications such as car floors, walls, ceilings, interior walls of trunks, and skin sheets for interior materials such as seat bags. The current situation is that it is difficult to say that this is something that can be achieved. Purpose and Summary of the Invention The present inventors used a specific peroxide crosslinked polyolefin resin, blended it with a peroxide crosslinked olefin copolymer rubber and a peroxide decomposed polyolefin resin, and created a dynamic It has been found that a thermoplastic elastomer having excellent properties such as heat resistance and tensile properties as well as excellent thin film formability can be obtained when it is partially crosslinked by heat treatment. That is, an object of the present invention is to provide a thermoplastic elastomer that has excellent properties such as heat resistance, tensile properties, weather resistance, flexibility, and rebound resilience, as well as excellent thin film formability. According to the present invention, (a) 60 to 30 parts by weight of peroxide crosslinked olefin copolymer rubber, (b) 20 to 40 parts by weight of peroxide crosslinked polyolefin resin, and (c) 40 to 20 parts by weight of peroxide decomposition type polyolefin resin. Department (here
(a) + (b) + (c) selected to be 100 parts by weight) is dynamically heat treated in the presence of (d) organic peroxide and partially crosslinked to produce a thermoplastic material. In the elastomer, (b) peroxide crosslinked polyolefin resin is
A random copolymer of ethylene and α-olefin having 4 to 10 carbon atoms, the copolymer has an ethylene content of 90 to 99.5 mol%, a melt index of 0.1 to 50 g/10 min, and a density of 0.910 to 0.940 g. /
cm ³ and a melting point of 115 to 130°C. Structure of the Invention The (a) peroxide crosslinked olefin copolymer rubber used in the present invention refers to an amorphous rubber whose main component is olefin, such as ethylene-propylene-nonconjugated diene rubber or ethylene-butadiene copolymer rubber. Rubber is an elastic copolymer of (d) that becomes crosslinked when mixed with an organic peroxide and kneaded under heating, resulting in reduced fluidity or no fluidity. Note that the non-conjugated diene refers to dicyclopendadiene, 1,4-hexadiene, dicyclooctadiene, methylene norbornene, ethylidene norbornene, and the like. In the present invention, among these copolymer rubbers,
Ethylene-propylene copolymer rubber, ethylene-
Propylene - non-conjugated diene rubber, in which the molar ratio of ethylene units to propylene units (ethylene/propylene) is from 50/50 to 90/10, especially
Those with a ratio of 55/40 to 85/15 are preferably used,
Among these, ethylene-propylene-nonconjugated diene copolymer rubber, particularly ethylene-propylene-ethylidene norbornene copolymer rubber, is preferred in that a thermoplastic elastomer having excellent heat resistance, tensile properties, and rebound properties can be obtained. Also, the Mooney viscosity of this copolymer rubber is ML _1+4.
(100℃) is preferably 10 to 120, especially 40 to 80,
If it is less than 10, only a composition with poor tensile properties will be obtained, while if it exceeds 120, the fluidity of the composition will be poor. Furthermore, the iodine value (degree of unsaturation) of the copolymer rubber is 16.
It is preferably below, and within this range a thermoplastic elastomer with well-balanced fluidity and rubber properties can be obtained. The peroxide decomposition type polyolefin resin (c) used in the present invention refers to a polyolefin resin that does not crosslink and exhibit no decrease in fluidity even when mixed with (d) organic peroxide and kneaded under heating. That is, (d)
In the competitive reaction between the decomposition reaction and the crosslinking reaction that occur when thermally reacting with an organic peroxide, many decomposition reactions occur, resulting in a decrease in the apparent molecular weight of the polymer. Examples of such polyolefin resins include α-olefins containing 3 or more carbon atoms, that is, homopolymers of α-olefins having propylene or more, or copolymers of two or more α-olefins, In the present invention, prepyrene, 1-
It is selected from homopolymers and copolymers of butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene, and especially contains polypropylene and usually 50 mol% or more of propylene. Copolymers can be suitably used. In addition, this polyolefin resin has a melt index of about 0.1 to 50 g/10 min, especially 5 to 20 g/10 min, although it varies depending on the type of polymer used.
10 min is preferable. An important feature of the present invention is that in order to impart thin film formability to the thermoplastic elastomer obtained, the above-mentioned (a) peroxide crosslinked olefin copolymer rubber and (c) peroxide decomposition type polyolefin resin are used in combination. b) Peroxide cross-linked polyolefin resin, i.e., polyolefin resin whose fluidity decreases or becomes non-flowable when mixed with (d) organic peroxide and kneaded under heating, is a polyolefin resin containing ethylene and a carbon number of 4 to 10, preferably carbon. The purpose is to use a random copolymer with several 5 to 10 α-olefins. This random copolymer contains so-called linear low-density polyethylene (LLDPE).
) is also included. In this random copolymer, the α-olefin having 4 to 10 carbon atoms to be copolymerized with ethylene includes 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene,
Examples include 1-decene or a mixture of at least two thereof, preferably having 5 to 10 carbon atoms.
α-olefin, most preferably having 6 to 8 carbon atoms
α-olefins, especially 4-methyl-1-pentene, are preferred. Further, this random copolymer has an ethylene content of 90 to 99.5 mol%, preferably 94 to 99 mol%,
It is also important that the content is most preferably in the range of 95 to 99 mol%. If the ethylene content exceeds 99.5 mol %, the resulting thermoplastic elastomer will lack flexibility, and if it is less than 90 mol %, it will become sticky after dynamic heat treatment and the heat resistance will decrease, so both are not preferred. Furthermore, this random copolymer preferably has a crystallinity of 40 to 70% as measured by
The value measured according to the method of D-1238 at 190°C and a load of 2160 g) is 0.1 to 50 g/10 min, preferably 0.5 to 30 g/10 min, and the density is 0.910 to 30 g/10 min.
0.940 g/cm ³ , preferably 0.915 to 0.935 g/cm ³ and a melting point (ASTM-D-2117) of 115 to
A temperature of 130°C, preferably 115-125°C is required. Even if the melt index (hereinafter referred to as MI), density, or melting point of these random copolymers is outside the above range, thermoplastic elastomers with excellent thin film formability as shown in the examples below can be obtained. I can't. For example, if the melt index is lower than 0.1g/10min, the thin film mold (extrusion characteristics) of the thermoplastic elastomer obtained will be impaired;
When the time is higher than 10 min, the tensile strength of the obtained thermoplastic elastomer decreases. In addition, these ethylene and α having 4 to 10 carbon atoms
- As an example of producing a random copolymer with an olefin, the method detailed in JP-A-53-92887 by the present applicant can be exemplified. In the present invention, (a) 60 to 30 parts by weight of peroxide crosslinked olefin copolymer rubber, (b)
Peroxide cross-linked polyolefin resin 20 to 40
(d) organic peroxide. Dynamically heat treated in the presence of to cause partial crosslinking. (b) If the amount of peroxide crosslinked polyolefin resin is more than the above range, the fluidity of the thermoplastic elastomer will decrease, and its moldability will deteriorate. Further, if the amount is less than the following range, desired thin film formability cannot be obtained. (c) If the amount of peroxide-decomposed polyolefin resin exceeds the above range, problems such as a decrease in the heat resistance and tensile properties of the thermoplastic elastomer will occur; if it is less than the above range, the treated olefin resin of (a) The same drawbacks occur when the degree of crosslinking of the polymer rubber is low. Examples of the organic peroxide used as component (d) 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)hexyne-3,1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-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, tert-butyl perbenzoate,
Examples include tert-butyl peroxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butyl cumyl peroxide. Among these, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,
5-di(tert-butylperoxy)hexyne-
3,1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and n-butyl-4,4-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane,
-butylperoxy)valerate is preferred, and 1,3-bis(tert-butylperoxyisopropyl)benzene is most preferred. The amount of this organic peroxide is (a), (b) and
The amount is selected 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 component (c).
If this amount is less than the above range, (a)
As a result of the degree of crosslinking of component (b) being too low, the thermoplastic elastomer obtained will have insufficient rubbery properties such as heat resistance, tensile properties, elastic recovery and rebound resilience, and strength; When used, the degree of crosslinking of components (a) and (b) increases, resulting in a decrease in moldability of the thermoplastic elastomer. According to the present invention, the organic peroxide of component (d) is added to the blend of components (a) to (c) described above,
A partially crosslinked thermoplastic elastomer is obtained by dynamic heat treatment. In the present invention, partially crosslinked means that the degree of crosslinking, that is, the gel content measured by the method below.
Say something between 45 and 98%. Method for Measuring Gel Content: Weigh approximately 100 mg of a sample pellet and immerse it in a sealed container in 30 c.c. of cyclohexane, an amount sufficient for the sample amount, for 48 hours. Next, a sample is taken out onto a filter paper and dried at room temperature for at least 72 hours until it reaches a constant weight. Here, gel content = dry weight after cyclohexane immersion/weight before cyclohexane immersion x 100 (%) In addition, dynamically heat-treated means kneading in a molten state. The kneading is preferably carried out in a closed type apparatus, and preferably in an atmosphere of an inert gas such as nitrogen or carbon dioxide. The temperature is such that the half-life of the organic peroxide used is less than 1 minute, usually 150°C.
-280°C, preferably 170-240°C, and kneading time is usually 1-20 minutes, preferably 1-10 minutes. Also, the applied shear force is usually 10~
10 ⁴ _sec ⁻¹ , preferably 10 ² to 10 ³ _sec ⁻¹ . As the kneading device, a mixing roll, an intensive mixer such as a Banbury mixer, a kneader, a single-screw or twin-screw extruder, etc. can be used, but a non-open type is preferred. In the present invention, in this partial crosslinking treatment, 0.05 to 3% by weight based on the total amount of (a), (b) and (c)
A crosslinking aid can be blended in an amount of . Examples of the crosslinking aid include sulfur, p-quinonedioxime, p,p'-dibenzoylquinonedioxime,
N-methyl-N,4-dinitrosoaniline, nitrobenzene, diphenylguanidine, trimethylolpropane-N,N'-m-phenylene dimaleimide, divinylbenzene, triallyl cyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate , polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, allyl methacrylate, vinyl butyrate, or vinyl stearate, and by using such crosslinking aids, a uniform and mild crosslinking reaction can be expected. Particularly in the present invention, when divinylbenzene is used, it is easy to handle, and a thermoplastic elastomer having a well-balanced fluidity and various physical properties can be obtained. That is, divinylbenzene is liquid at room temperature, can dissolve organic peroxide (d), and has solubility in components (a) to (c), so it can be used as a dispersion aid and diluent for organic peroxides. It works to improve the dispersibility of the organic peroxide into each component, and thus to bring about uniform and mild crosslinking. Further, divinylbenzene itself becomes a radical and acts as a chain transfer agent and a crosslinking agent, and by using divinylbenzene, a crosslinking effect greater than that obtained by using an organic peroxide alone can be expected. In the present invention, a mineral oil-based softener can be added in advance, if necessary, during partial crosslinking. This mineral oil softener usually weakens the intermolecular attraction of rubber during roll processing, making processing easier, and also helps disperse carbon black, white carbon, etc., or reduces the hardness of vulcanized rubber. A high boiling point petroleum distillate used to increase flexibility and elasticity.
They are classified into naphthenic, aromatic, etc. This mineral oil-based softener includes (a), (b) and
It may be used in an amount up to 50% by weight based on the total weight of component (c). If it is used in an amount exceeding this range, the heat resistance of the thermoplastic elastomer will decrease, or the softener will ooze out, resulting in problems such as poor appearance. The thermoplastic elastomer of the present invention also has strength,
Fillers, colorants, anti-aging agents, antioxidants, light resistance or light resistance stabilizers, processing aids, antistatic agents, and other physical property improvers can be added as appropriate to the extent that moldability and rubber properties are not impaired. . These may be blended at any stage of the process. For example, fillers include carbon black, clay, talc, heavy calcium carbonate, kaolin,
Examples include diatomaceous earth, silica, alumina, asbestos, graphite, glass fiber, etc. Antioxidants include phenyl-α-naphthylamine, p-isopropoxy diphenylamine,
Amine-based antioxidants such as N,N'-diphenyl ethylenediamine, nonylated diphenylamine,
2,6-ditertiarybutylphenol, styrenated phenol, butylhydroxyanisole, 4,4'-hydroxydiphenyl, 2,2-methylene-bis-(4-methyl-6-cyclohexyl phenol), tetrakis-[ methylene-3-
(3′,5′-ditertiary-butyl-4′-hydroxyphenyl)propionate]methane, tris-
Examples include phenolic antioxidants such as (2-methyl-hydroxy-5-ditertiarybutylphenyl)butane. (d) To promote the decomposition of organic peroxides, trisethylamine, tributylamine,
Tertiary amines such as 2,4,6-tris(dimethylamino)phenol, and organic metals such as naphthenates and octanoates of aluminum, cobalt, panadium, copper, calcium, zirconium, manganese, magnesium, lead, mercury, etc. A carboxylic acid salt can also be used in combination in the process of dynamic heat treatment. The thus obtained thermoplastic elastomer of the present invention can be molded using equipment used for ordinary thermoplastics, such as extrusion molding, calendar molding,
Suitable for injection molding, etc. Furthermore, since the component (b) of the thermoplastic elastomer of the present invention is partially crosslinked, it has particularly excellent thin film formability, and for example, when applied to sheet forming, it is possible to form a sheet with a thickness of up to 0.08 mm. Suitable for applications such as car floors, walls, ceilings, interior walls of trunks, and surface sheets for interior materials such as seat bags. In addition, the thermoplastic elastomer of the present invention has excellent rubber properties such as heat resistance, weather resistance, tensile properties, flexibility, and rebound resilience because the components (a) and (b) are crosslinked. Because of its good liquidity,
Even when used as a large, thick-walled product, a product with a good appearance without flow marks or sink marks can be obtained. The invention is illustrated by the following example. Example 1 Ethylene-propylene with an ethylene content of 78 mol%, an iodine number of 20, and a Mooney viscosity of ML ₁₊₄ (121°C) 55
Dicyclopentadiene copolymer rubber (hereinafter referred to as
(abbreviated as EPDM) pellets 55 parts by weight, ethylene content 96.5 mol%, melting point 120℃, MFR (190℃, 2.16Kg)
18, 20 parts by weight of ethylene-4-methyl-1-pentene copolymer pellets with a density of 0.920, MFR (230°C,
2.16Kg) 11, polypropylene (hereinafter referred to as PP) with a density of 0.91
25 parts by weight of pellets, 0.3 parts by weight of antioxidant, 0.2 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, and 0.3 parts by weight of divinylbenzene were mixed with paraffinic mineral oil. 0.5
The solution dispersed in parts by weight was mixed using a Henschel mixer to thoroughly and uniformly disperse the pellets, and the solution was evenly adhered to the surface of the pellets. The pellets were then extruded using a twin-screw extruder at 230°C under a nitrogen atmosphere to obtain a thermoplastic elastomer. This thermoplastic elastomer was formed into a sheet with a thickness of 0.08 mm using a T-die using an extrusion molding machine, and its thin film formability was measured at 140°C, assuming molding by hot press.
Table 1 shows the results of evaluating the grain flow properties using a hot plate press for 20 seconds. Example 2 Ethylene-propylene with an ethylene content of 78 mol%, an iodine number of 20, and a Mooney viscosity of ML ₁₊₄ (121°C) 55
Dicyclopentadiene copolymer rubber pellets 45 parts by weight, ethylene content 96.5 mol%, melting point 120°C,
MFR (190℃, 2.16Kg) 18, ethylene-4-methyl-1-pentene copolymer pellets with density 0.920 30
Parts by weight, MFR (230℃, 2.16Kg) 11, 25 parts by weight of polypropylene pellets with a density of 0.91, antioxidant 0.3
parts by weight, and 0.2 parts by weight of 2,5 dimethyl-2,5 di(t-butylperoxy)hexyne-3 and 0.3 parts by weight of divinylbenzene in paraffinic mineral oil.
A 0.5 part by weight solution was mixed using a Henschel mixer to thoroughly and uniformly disperse the pellets, and the solution was evenly adhered to the surface of the pellets. The pellets were then extruded using a twin-screw extruder at 230°C under a nitrogen atmosphere to obtain a thermoplastic elastomer. This thermoplastic elastomer was formed into a sheet with a thickness of 0.08 mm using a T die using an extrusion molding machine, and its thin film formability was measured at 140°C, assuming molding by hot press.
The grain flow properties were evaluated using a hot plate press for 20 seconds, and the results are shown in Table 1. Comparative Example 1 Ethylene-propylene with an ethylene content of 78 mol%, an iodine value of 20, and a Mooney viscosity of ML ₁₊₄ (121°C) 55
70 parts by weight of dicyclopentadiene copolymer rubber pellets, MFR (230°C, 2.16Kg) 11, 30 parts by weight of polypropylene (hereinafter abbreviated as PP) pellets with a density of 0.91,
0.3 parts by weight of antioxidant, and 2,5 dimethyl-2,
5 di(t-butylperoxy)hexyne-3,
A solution in which 0.2 parts by weight and 0.3 parts by weight of divinylbenzene were dispersed in 0.5 parts by weight of paraffinic mineral oil was mixed using a Henschel mixer, and the pellets were well and uniformly dispersed, and the solution was evenly adhered to the surface of the pellets. . The pellets were then extruded using a twin-screw extruder at 230°C under a nitrogen atmosphere to obtain a thermoplastic elastomer. This thermoplastic elastomer was formed into a sheet with a thickness of 0.25 mm using a T-die using an extrusion molding machine, and its thin film formability was measured at 140°C, assuming molding by hot press.
The grain flow properties were evaluated using a hot plate press for 20 seconds, and the results are shown in Table 1. Comparative Example 2 Ethylene-propylene with an ethylene content of 78 mol%, an iodine value of 20, and a Mooney viscosity of ML ₁₊₄ (121°C) 55
55 parts by weight of dicyclopentadiene copolymer rubber pellets, 20 parts by weight of high-pressure low density polyethylene pellets with a density of 0.915, MFR (230°C, 2.16Kg) 11, 25 parts by weight of polypropylene pellets with a density of 0.91, 0.3 parts by weight of antioxidant. , and 0.2 parts by weight of 2,5 dimethyl-2,5 di(t-butylperoxy)hexyne-3 and 0.3 parts by weight of divinylbenzene dispersed in 0.5 parts by weight of paraffinic mineral oil were mixed using a Henschel mixer. The pellets were well and uniformly dispersed, and the solution was evenly adhered to the surface of the pellets. The pellets were then extruded using a twin-screw extruder at 230°C under a nitrogen atmosphere to obtain a thermoplastic elastomer. This thermoplastic elastomer was formed into a sheet with a thickness of 0.08 mm using a T-die using an extrusion molding machine, and its thin film formability was measured at 140°C, assuming molding by hot press.
The grain flow properties were evaluated using a hot plate press for 20 seconds, and the results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1 (a) 60 to 30 parts by weight of peroxide crosslinked olefin copolymer rubber, (b) 20 to 40 parts by weight of peroxide crosslinked polyolefin resin, (c) 40 to 20 parts by weight of peroxide decomposition type polyolefin resin. parts by weight (where (a) + (b) + (c) are chosen to be 100 parts by weight) is dynamically heat treated in the presence of (d) an organic peroxide to partially crosslink it. In the thermoplastic elastomer made of (b) peroxide crosslinked polyolefin resin,
A random copolymer of ethylene and α-olefin having 4 to 10 carbon atoms, the copolymer has an ethylene content of 90 to 99.5 mol%, a melt index of 0.1 to 50 g/10 min, and a density of 0.910 to 0.940 g. /
cm ³ and a melting point of 115 to 130°C. 2. The thermoplastic elastomer according to claim 1, wherein a mineral oil-based softener is added to the blend, if necessary. 3. The thermoplastic elastomer according to claim 1, wherein (d) the organic peroxide is used in an amount of 0.05 to 3% by weight based on the total amount of components (a), (b) and (c). 4 (a) The peroxide crosslinked olefin copolymer rubber is an ethylene-propylene copolymer rubber or an ethylene-propylene non-conjugated rubber having a molar ratio of ethylene to propylene (ethylene/propylene) of 50/50 to 85/15. The thermoplastic elastomer according to claim 1, which is a diene copolymer rubber. 5. (c) The thermoplastic elastomer according to claim 1, wherein the peroxide decomposition type polyolefin resin is a homopolymer of an α-olefin having 3 or more carbon atoms or a copolymer of two or more types of α-olefins. .