JPH0233062B2 - NETSUKASOSEIERASUTOMAASOSEIBUTSUNOSEIZOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing thermoplastic elastomer compositions. More specifically, the present invention relates to a method for producing an at least partially crosslinked thermoplastic elastomer composition that has further improved physical properties such as compression set. Partially crosslinked heat obtained by dynamically heat treating an uncrosslinked compound containing an organic peroxide crosslinked olefinic copolymer rubber and an organic peroxide decomposed olefinic plastic as essential components in the presence of an organic peroxide. Plastic elastomer compositions have various excellent properties, but due to their structure, they have hard segments that do not have rubber properties to ensure moldability and are thermoplastic. It cannot be denied that, compared to vulcanized rubber, it is inferior in terms of physical properties such as compression set, permanent elongation, and rebound resilience, especially under high temperature conditions. For this reason, thermoplastic elastomer compositions have not been able to be used in the field of vulcanized rubber applications, particularly in applications such as flexible packing materials and sealing materials. That is, in these application fields, a low compression set is an absolutely necessary condition, and therefore, there has been a strong desire for improvement in this respect for thermoplastic elastomer compositions as well. The present inventors have conducted various studies in search of a thermoplastic elastomer composition that is flexible and has low compression set while maintaining good moldability. It has been found that repeating the heat treatment multiple times is extremely effective. Accordingly, the present invention relates to a method for producing an at least partially crosslinked thermoplastic elastomer composition, the thermoplastic elastomer composition comprising an organic peroxide crosslinked olefin copolymer rubber and an organic peroxide decomposed olefin plastic. It is produced by dynamically heat-treating an uncrosslinked formulation containing an essential component in the presence of an organic peroxide, and performing the dynamic heat treatment in two stages. If necessary, an organic peroxide non-crosslinked hydrocarbon-based rubbery substance, a mineral oil-based softener, or both may be blended into the uncrosslinked compound to be treated. Dynamic heat treatment in the presence of organic peroxide is carried out in two stages. Specifically, the mixture is uniformly kneaded in advance using a kneading machine such as a Banbury mixer, and then cut into square pellets using a sheet cutter or the like. mixing of the uncrosslinked formulation is carried out in a first step,
In the second step, dynamic heat treatment is carried out in which the square pellets are kneaded, reacted and granulated in an extruder with organic peroxide under partially cross-linking conditions, and the granulated pellets are mixed with organic peroxide under cross-linking conditions again. At the same time, a dynamic heat treatment of kneading, reaction, and granulation in an extruder is performed in the third step. The first step and the second step can also be carried out at the same time. In this case, the pellets of each component constituting the uncrosslinked compound and the organic peroxide are put into an extruder together, and the pellets are placed under partially crosslinked conditions. After the dynamic heat treatment of kneading, reaction, and granulation is performed in step 3, it is subjected to dynamic heat treatment again in the presence of organic peroxide in the third step. The organic peroxide crosslinked olefin copolymer rubber to be crosslinked includes ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1
- A random copolymer with an α-olefin such as pentene, 1-hexene, 1-decene, preferably peropylene or 1-butene, preferably a random copolymer further copolymerized with a polyene component. used. Polyene components include 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5
- linear non-conjugated dienes such as hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, cyclohexadiene, dicyclopentadiene, methyltetrahydroindene,
5-vinylnorbornene, 5-ethylidene-2-
norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene,
Cyclic non-conjugated dienes such as 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2, 2-norbornadiene, 1,3,7-octatriene, 1,4,9-
Typical examples include trienes such as decatriene, with 1,4-hexadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene being particularly preferred. These ethylene/α-olefin copolymers are
Ethylene and α-olefin are approximately 50/50 to 95/
5. It is preferably copolymerized at a molar ratio of about 55/45 to 85/15, and when a polyene component is further copolymerized, the iodine value of the copolymer is about 4 to 85/15.
75, preferably about 8 to 40. These ethylene, α-olefin copolymers generally have a Mooney viscosity (ML ₁₊₄ at 100°C) of about 10 to 250, preferably about 40 to 200.
have. Furthermore, the organic peroxide crosslinked olefin copolymer rubber composed of ethylene/α-olefin copolymer is a so-called oil-extended product, which is blended in advance with about 150 parts by weight or less of a mineral oil softener per 100 parts by weight of the copolymer rubber. It can also be used in a state. Organic peroxide decomposition type olefin plastics include low-density to high-density polyethylene,
95 mol% or more of ethylene and 5 mol% or less of propylene, 1-butene, 1-pentene, 4-methyl-
- Copolymers with α-olefins such as pentene and 1-hexene, olefinic doubles other than α-olefins such as 85 mol% or more of ethylene and 15 mol% or less of vinyl acetate, acrylic esters, methacrylic esters, etc. Copolymer with a polymerizable monomer having a bond; polypropylene; crystalline copolymer of 90 mol% or more propylene and 10 mol% or less α-olefin other than propylene; poly-1-butene;
90 mol% or more of 1-butene and 10 mol% or less of 1-butene
Crystalline copolymer with α-olefin other than butene; poly 4-methyl-1-pentene, 90 mol%
Examples include crystalline copolymers of the above 4-methyl-1-pentene and 10 mol% or less of α-olefin other than 4-methyl-1-pentene, and mixtures thereof.
10 minutes (190°C) of the above ethylene homopolymer or copolymer, melt index 0.1-100g/
Homopolymers or copolymers of propylene and mixtures thereof for 10 minutes (230° C.) are preferably used. These olefin plastics are
It is used in a weight ratio of about 10/90 to 50/50, preferably about 20/80 to 40/60, based on the copolymer rubber. In the uncrosslinked formulation, an organic peroxide non-crosslinked hydrocarbon rubbery material is included to improve the moldability of the crosslinked thermoplastic elastomer composition;
A mineral oil softener or a mixture thereof may be blended as a moldability improver. Organic peroxide non-crosslinked hydrocarbon-based rubbery substances are hydrocarbon-based rubbery substances that do not crosslink even when mixed with peroxide and kneaded under heat, and therefore do not reduce fluidity, such as polyisobutylene, Examples include butyl rubber, a copolymer of propylene with ethylene or 1-butene containing 50 mol% or more, and atactic polypropylene. Among these, polyisobutylene and propylene with a content of about 50 to 95 mol% have a reduced specific viscosity. (0.1g polymer/100ml decalin, 135℃; same below) is approx.
A rubbery copolymer of propylene and ethylene with a concentration of 1.5 to 9.0/g is most preferred from the viewpoint of performance and handling. Mineral oil softeners usually weaken the intermolecular forces of rubber during roll processing, making processing easier, and also help disperse carbon black, white carbon, etc., or reduce the hardness of vulcanized rubber. It is a high-boiling petroleum fraction used for the purpose of increasing flexibility and elasticity, and is classified as paraffinic, naphthenic, or aromatic. These moldability improvers are generally blended in a proportion of about 5 to 150 parts by weight, preferably about 10 to 80 parts by weight, particularly preferably about 20 to 60 parts by weight, based on 100 parts by weight of the copolymer rubber component. Subjected to a heat treatment process. By blending the moldability improver in such a proportion,
Even when injection molding large-sized molded products with high strength and thick walls,
A product with excellent gloss and no flow marks or sink marks can be obtained. If the proportion is higher than this, the heat resistance and strength of the molded product will decrease, which is not preferable. The dynamic heat treatment in the presence of an organic peroxide, which is carried out in two stages, is carried out by melting the uncrosslinked compound and the organic peroxide, kneading them, and subjecting them to a crosslinking reaction. As kneading equipment, open mixing rolls, closed Banbury mixers, extruders, kneaders, continuous mixers, etc. are used.
It is preferable to use a non-open type device and to knead in an atmosphere of an inert gas such as nitrogen gas or carbon gas. Kneading is carried out at a temperature at which the half-life of the organic peroxide used is less than 1 minute, generally around 150°C.
~280℃, preferably about 170-240℃, about 1-20
This is carried out for about 3 to 10 minutes, preferably about 3 to 10 minutes. Crosslinking of copolymer rubber performed by such dynamic heat treatment is a competitive reaction between the crosslinking reaction and the decomposition reaction that occurs when the copolymer is thermally reacted with a crosslinking agent such as an organic peroxide. This refers to a phenomenon in which the apparent molecular weight of the copolymer increases as a result of more crosslinking reactions occurring. Examples of organic peroxides used as crosslinking agents include dicumyl peroxide, ditert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and 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-butyl peroxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4
-Dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, tert-butyl cumyl peroxide and the like. Among these organic peroxides, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 2,5-dimethyl-2,5-di( tert-butylperoxy)-hexyne-3,1,3-bis(tert-butylperoxyisopropyl)benzene,
1,1-bis(tert-butylperoxy)-3,3,
3-trimethylcyclohexane, n-butyl-
4,4-bis(tert-butylperoxy)valerate and the like are preferred, and 1,3-bis(tert-butylperoxyisopropyl)benzene is particularly preferred. These organic peroxides are used in the second and third steps in an amount of about 1 x 10 ^-4 to 4.5 x 10 ^-3 mol, preferably about 5 x 10 ^{-4 to} 3.5 mol, per 100 g of uncrosslinked copolymer rubber, respectively. Generally used in the proportion of ×10 ^-3 moles. The proportion of organic peroxide used in each step is sufficient to partially crosslink the copolymer rubber, so that the thermoplastic elastomer composition obtained through the second and third steps is at least partially crosslinked. It can be said that this has been done. When a crosslinking aid is present in the heat treatment process, a uniform and mild crosslinking reaction is expected, and a thermoplastic elastomer composition with excellent heat resistance can be obtained. Examples of crosslinking aids include sulfur, p-quinonedioxime, p,p'-dibendiylquinonedioxime, 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, vinyl stearate, etc. are used. Since divinylbenzene has good compatibility with olefinic plastics, the crosslinking effect upon heat treatment is uniform, providing a thermoplastic elastomer composition with a good balance between fluidity and physical properties and excellent heat resistance. The various crosslinking aids as described above are used in an amount of about 0.1 to 2 parts by weight per 100 parts by weight of the total amount of the compound in the heat treatment process.
It is preferably added in an amount of about 0.3 to 1 part by weight. If the blending ratio is higher than this, the crosslinking reaction will proceed if the blending amount of the organic peroxide is large, giving a thermoplastic elastomer composition with poor fluidity, while if the blending ratio of the organic peroxide is small, unreacted monomers will be produced. It may remain in the thermoplastic elastomer composition as a polymer, and its physical properties may change due to the thermal history during processing and molding. In this way, by performing dynamic heat treatment in the presence of organic peroxide in two stages,
Compared to a single use of the same amount of organic peroxide, the resulting partially crosslinked thermoplastic elastomer composition has significant improvements in compression set and moldability, and It has also been improved in other ways. Therefore, by effectively utilizing the properties improved in this way, it is possible to use it for the same purposes as vulcanized rubber. Next, the present invention will be explained with reference to examples. Example 1 Ethylene/propylene/5-ethylidene-2-
Norbornene ternary copolymer rubber (EPF; ethylene/propylene molar ratio 78/22, Mooney viscosity
ML ₁₊₄ 90, iodination (2) 55 parts (weight, same below),
Polypropylene (PP; ASTM-D-1238-65T
Melt index 20, measured at 230°C by
Density 0.91g/cm ³ ) 20 parts, propylene/ethylene copolymer rubber (PER; molar ratio of propylene/ethylene 57/43, reduced specific viscosity 3 dl/g) 25 parts and mineral oil softener (paraffinic process oil) 20 parts in a nitrogen atmosphere using a Banbury mixer.
After kneading at 180°C for 5 minutes, the mixture was passed through a roll and pellets were produced using a sheet cutter. [First step] To 120 parts of this pellet, 0.3 part of 1,3-bis(tert-butylperoxyisopropyl)benzene (this corresponds to 1.94×10 ^-3 mol per 100 g of EPT) was added in advance to 0.5 part of divinylbenzene. The dissolved and dispersed solution was added and mixed using a tumbler blender to adhere this solution to the pellet surface. Then, using an extruder, the pellets are
It was extruded at 210°C in a nitrogen atmosphere to form pellets.
[Second step] Furthermore, 120 parts of this pellet and 0.4 parts of 1,3-bis(tert-butylperoxyisopropyl)benzene
part (this corresponds to 2.58 × 10 ^-3 mol per 100 g of EPT) of a solution of 0.5 part of divinylbenzene,
The solution was applied to the pellet surface by mixing using a tumbler blender. Thereafter, this pellet was extruded using an extruder at 210° C. in a nitrogen atmosphere to prepare the desired thermoplastic elastomer composition. [Third Step] Example 2 In Example 1, 10 parts of liquid paraffin (Nippon Oil Products High White) was used instead of the mineral oil softener, the first step was omitted, and this was used in the second step. After mixing together the raw materials and pelletizing, a thermoplastic elastomer composition was prepared through a third step. Example 3 In Example 1, the amount of EPT was increased from 55 parts to 60 parts, and instead of 25 parts of PER, polyisobutylene (PIB; Vistanex MML, a product of Etsuo Co., Ltd.) was used.
-100) 20 parts were used. Comparative Example 1 In Example 1, the third step was omitted. Comparative Example 2 In Example 2, liquid paraffin was mixed in the first step, and the third step was omitted. The moldability and basic physical properties of the thermoplastic elastomer compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 2 above were evaluated by the following methods. The obtained results are shown in Tables 1 and 2 below. [Test method] 1. Injection moldability (1) Injection molding was performed using the following equipment and conditions. Molding machine: Dynamelter (manufactured by Kaki Seisakusho) Molding temperature: 200℃ Injection pressure: Primary pressure 1300Kg/ ^cm2 , secondary pressure 700
Kg/ ^cm2 Injection pressure: Maximum Molding speed: 90 seconds/1 cycle Mold: 2-point gate square plate mold Molded product: 3 types of square plates (length 300mm, width 180mm)
mm, thickness 2, 4, 7 mm) (2) Appearance criteria for molded products (a) Flow marks were evaluated on the following 5 scales (Evaluation) 1: Flow marks are extremely common 2: Significantly seen over the entire surface of the molded product 3: Slightly observed on the entire surface of the molded product. 4: Slightly observed only on the opposite side of the gate 5: No flow marks observed at all 2 Extrusion moldability (1) The tube was extruded using the following equipment and conditions Molding machine: 40mmφ extruder (manufactured by Toshiba Machine Co., Ltd.) ) Molding temperature: 210℃ Die: Straight die (Die/core = 12.5
mm/10.0mm) Take-up speed: 10 m/min (2) As a criterion for the appearance of the molded product, the unevenness of the tube surface was evaluated on the following 5 scales (Evaluation) 1: Large wavy rough skin 2: Significant rough skin 3: Fine rough skin 4: Skin is smooth but not shiny 5: Skin is extremely smooth and shiny 3 Basic physical properties Thickness obtained by injection molding using method 1 above 2
A test piece was cut from a mm square plate and the following values were measured. Melt flow index: ASTM-D-
1238−65 (230℃, 10Kg load) 100% elongation stress: JIS K-6301 Tensile stress at break: JIS K6301 Tensile elongation at break: JIS K-6301 Spring hardness: JIS K-6301 (JISA type) Permanent elongation: JIS K-6301 Compression set: JIS K-6301 (70℃, 22 hours)

【table】

【table】

Claims (1)

[Scope of Claims] 1. An uncrosslinked compound containing an organic peroxide crosslinked olefin copolymer rubber and an organic peroxide decomposed olefin plastic as essential components is dynamically heat-treated in the presence of an organic peroxide, and partially When producing a crosslinked thermoplastic elastomer composition, a first step in which an uncrosslinked formulation is mixed; a second step in which an organic peroxide is added to the first step mixture and a dynamic heat treatment is performed;
A method for producing a thermoplastic elastomer composition, characterized in that an organic peroxide is further added to the second step dynamic heat treatment product, and a third step of dynamic heat treatment is sequentially carried out. 2. The method for producing a thermoplastic elastomer composition according to claim 1, wherein an uncrosslinked compound containing an organic peroxide non-crosslinked hydrocarbon rubbery substance and/or a mineral oil softener is used. 3. The method for producing a thermoplastic elastomer composition according to claim 1, wherein the dynamic heat treatment in the second step and the third step is performed in the presence of a crosslinking aid. 4 A partially crosslinked thermoplastic elastomer is obtained by dynamically heat-treating an uncrosslinked compound containing an organic peroxide crosslinked olefin copolymer rubber and an organic peroxide decomposition type olefin plastic as essential components in the presence of an organic peroxide. When producing the composition, the first and second steps are performed in which mixing and dynamic heat treatment of the uncrosslinked compound and the organic peroxide are performed simultaneously, and the organic peroxide is further added to the dynamic heat-treated product of the first and second steps. 1. A method for producing a thermoplastic elastomer composition, which comprises sequentially carrying out a third step in which a thermoplastic elastomer composition is added and a dynamic heat treatment is performed. 5. The method for producing a thermoplastic elastomer composition according to claim 4, wherein an uncrosslinked compound containing an organic peroxide non-crosslinked hydrocarbon rubbery substance and/or a mineral oil softener is used. 6. The method for producing a thermoplastic elastomer composition according to claim 4, wherein the dynamic heat treatment in the second step and the third step is performed in the presence of a crosslinking aid.