JP2010235703A - Molded product and composition of olefinic thermoplastic elastomer and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a molded product of an olefinic thermoplastic elastomer, which is excellent in balance between elasticity (particularly elastic recovery) and tensile strength and is free of appearance defects such as fish eye; an olefinic thermoplastic elastomer composition used for manufacturing the molded product; and a method for producing the olefinic thermoplastic elastomer composition. <P>SOLUTION: In the molded product of the olefinic thermoplastic elastomer comprising an olefinic thermoplastic resin and an olefinic crosslinked rubber, the olefinic crosslinked rubber is one obtained by crosslinking an olefinic rubber with a halogenated alkylphenol formaldehyde resin, the compounding amount of the olefinic rubber is 20-70 mass%, and the halogenated alkylphenol formaldehyde resin has a halogen content of ≤3.5 mass% and is compounded in an amount of 0.5-10 mass%. Kneading and dynamic crosslinking are carried out in the presence of a supercritical fluid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a molded product of an olefinic thermoplastic elastomer containing an olefinic thermoplastic resin and a crosslinked olefinic rubber, an olefinic thermoplastic elastomer composition used in the molded product, and the olefinic thermoplastic elastomer composition. It is related with the manufacturing method.

  Today, olefinic thermoplastic elastomers are lightweight and easy to recycle, and in addition, various molded products can be obtained easily by ordinary thermoplastic resin molding methods such as injection molding and profile extrusion molding. It is used for anything. However, olefinic thermoplastic elastomers have a problem that they are inferior in elasticity (particularly elastic recovery) as compared with vulcanized rubber.

  Patent Document 1 describes a conjugated diene having a relatively sharp molecular weight distribution as having improved elasticity while having the advantage of being lightweight and easy to recycle and mold like the above olefinic thermoplastic elastomer. There has been proposed a thermoplastic elastomer composition containing a polymer crosslinked rubber and a thermoplastic resin. However, this thermoplastic elastomer composition does not satisfy the tensile strength which is one of the required performances of products (particularly automobile parts).

  On the other hand, as described above, as a technique for obtaining a thermoplastic elastomer composition containing a crosslinked rubber and a thermoplastic resin, Patent Document 2 discloses a biaxial olefin rubber and an olefin thermoplastic resin together with a crosslinking agent. Oxygen-based thermoplastic elastomer with excellent physical properties is manufactured continuously and in a simplified manner by dynamically cross-linking by supplying to the extruder and uniformly dispersing the cross-linked rubber and thermoplastic resin. Technology has been proposed. However, generally, when a rubber such as an α-olefin copolymer having a high molecular weight compared to a resin is melt kneaded alone, the temperature in the extruder reaches a high temperature due to shearing heat generation, and thermal degradation proceeds. It is difficult to obtain a thermoplastic elastomer composition having both levels of elasticity and tensile strength. In addition, since the temperature in the extruder reaches a high temperature during kneading or the like, the crosslinking reaction cannot be controlled, and appearance defects such as fish eyes due to the crosslinked rubber in an overcrosslinked state occur in the molded product. was there.

  As a production method for reducing fish eyes in a polypropylene resin composition composed of a polypropylene resin and a thermoplastic elastomer of propylene and other α-olefins, Patent Document 3 describes kneading in the presence of carbon dioxide in a supercritical state. Techniques to do this have been proposed. However, what was obtained with this technique was inferior in elasticity. Patent Document 4 proposes a technique for kneading two types of thermoplastic resins in the presence of carbon dioxide in a supercritical state, but the one obtained by this technique is also inferior in elasticity. It was.

  Further, Patent Document 5 discloses a thermoplastic elastomer foam which kneads a thermoplastic resin and a rubber component in the presence of supercritical carbon dioxide and then releases the critical state of carbon dioxide to crosslink the rubber component. Body manufacturing methods have been proposed. However, since this method is a method for obtaining a thermoplastic elastomer composition containing a foam of a crosslinked rubber, only coarse particles of crosslinked rubber in the thermoplastic resin can be obtained, resulting in fish eyes. was there.

JP 2005-139297 A Japanese Examined Patent Publication No. 2-52648 JP 2002-146038 A JP 2002-322288 A JP-A-11-310656

  Accordingly, a molded product of an olefinic thermoplastic elastomer having an excellent balance between elasticity (especially elastic recovery) and tensile strength and having no appearance defects such as fish eyes, an olefinic thermoplastic elastomer composition used in the molded product, and this It aims at providing the manufacturing method of an olefin type thermoplastic elastomer composition.

  In order to solve the above-mentioned problem, a molded product of an olefinic thermoplastic elastomer of the present invention is a molded product of an olefinic thermoplastic elastomer containing an olefinic thermoplastic resin and an olefinic crosslinked rubber, the olefinic crosslinked The rubber is obtained by crosslinking an olefin rubber with a halogenated alkylphenol formaldehyde resin, the olefin rubber has a blending ratio of 20 to 70% by mass, and the halogenated alkylphenol formaldehyde resin has a halogen content of 3 .5% by mass or less, a blending ratio of 0.5 to 10% by mass, kneading of the olefinic thermoplastic resin and the olefinic rubber, and dynamics of the olefinic rubber by the halogenated alkylphenol formaldehyde resin Crosslinking in the presence of supercritical fluid Characterized in that made the.

  In the present specification, the blending ratio is the ratio of each raw material to the total amount of raw materials used (blended) used to obtain the olefinic thermoplastic elastomer.

  The olefinic thermoplastic elastomer composition of the present invention is an olefinic thermoplastic elastomer composition containing an olefinic thermoplastic resin and an olefinic crosslinked rubber, wherein the olefinic rubber is halogenated. Cross-linked with an alkylphenol formaldehyde resin, the olefin rubber has a compounding ratio of 20 to 70% by mass, and the halogenated alkylphenol formaldehyde resin has a halogen content of 3.5% by mass or less. The ratio is 0.5 to 10% by mass, and kneading of the olefinic thermoplastic resin and the olefinic rubber and dynamic crosslinking of the olefinic rubber with the halogenated alkylphenol formaldehyde resin are performed in the presence of a supercritical fluid. Characterized by what has been done.

The method for producing an olefinic thermoplastic elastomer composition of the present invention includes a kneading step of kneading an olefinic thermoplastic resin and an olefinic rubber having a compounding ratio of 20 to 70% by mass in the presence of a supercritical fluid, A cross-linking step of dynamically cross-linking olefin rubber in the presence of a supercritical fluid. In the cross-linking step, a halogenated alkylphenol formaldehyde resin having a halogen content of 3.5% by mass or less is used as a cross-linking agent. ,
The blending ratio of the halogenated alkylphenol formaldehyde resin is 0.5 to 10% by mass.

  The aspect of each element in the present invention is exemplified below.

1. Olefin-based thermoplastic resin The olefin-based thermoplastic resin is not particularly limited, and examples thereof include polypropylene (PP) and polyethylene (PE).
The physical properties of the olefin-based thermoplastic resin are not particularly limited, but are easy to knead with the olefin-based rubber, and the physical properties of the olefin-based thermoplastic elastomer are good. Therefore, at 230 ° C. and 21.18 N (2.16 kgf). The MFR (melt flow rate) is preferably 0.1 to 30 (g / 10 minutes), more preferably 0.5 to 10 (g / 10 minutes).
The blending ratio of the olefinic thermoplastic resin is not particularly limited, but is preferably 5 to 55% by mass, more preferably 10 to 50% by mass because the physical properties of the olefinic thermoplastic elastomer are improved. %.

2. Olefin Rubber The olefin rubber is not particularly limited, but EPDM (ethylene-propylene-nonconjugated diene rubber), EPM (ethylene-propylene rubber), EBM (ethylene-butylene copolymer), EOM (ethylene-octene copolymer). Examples thereof include ethylene-α olefin copolymers such as (polymer), which may be one kind or two or more kinds. Moreover, since it is easy to bridge | crosslink by halogenated alkylphenol formaldehyde resin, it is preferable that it is what contains EPDM at least. Furthermore, since the olefinic crosslinked rubber can be dispersed as smaller particles in the continuous phase of the olefinic thermoplastic resin, it is more preferable to use EPDM and another ethylene-α olefin copolymer. This is because other ethylene-α olefin copolymers such as EPM, EBM, EOM have a compatibilizing action.
When the blending ratio of the olefin rubber is less than 20% by mass, the elasticity of the olefin thermoplastic elastomer is deteriorated, and when it exceeds 70% by mass, kneading is difficult. Preferably, it is 28-70 mass%, More preferably, it is 32-64 mass%. In addition, when the olefin rubber contains at least EPDM, the blending ratio of EPDM is not particularly limited, but is preferably 15 to 70% by mass, and more preferably 18 to 64% by mass. Furthermore, when the olefin rubber is EPDM and another ethylene-α olefin copolymer, the blending ratio of the other ethylene-α olefin copolymer is preferably 10% by mass or less, more preferably 1 to 10% by mass.

3. Olefin-based cross-linked rubber The olefin-based cross-linked rubber is preferably dispersed in the form of particles having an average particle size of 1 μm or less in the continuous phase of the olefin-based thermoplastic resin because the surface appearance of the molded product is improved. This is because if the particles of the olefinic crosslinked rubber dispersed in the continuous phase of the olefinic thermoplastic resin are large, they appear as fish eyes on the surface of the molded product.
Here, the particle size of the olefinic crosslinked rubber is a value of a circle diameter (equivalent circle diameter) equal to the area (cross-sectional area) of the olefinic crosslinked rubber appearing in the cross section of the molded product of the olefinic thermoplastic elastomer. The average particle diameter of the olefin-based crosslinked rubber is an average value of this value (equivalent circle diameter).

4). Crosslinking agent By using a halogenated alkylphenol formaldehyde resin having a halogen content of 3.5% by mass or less as a crosslinking agent, the crosslinking reaction can be suitably controlled by dynamically crosslinking the olefinic rubber. It is possible to suppress the generation of fish eyes that cause the appearance of the molded product to be poor due to suppression of overcrosslinking, and to suppress the foaming of the olefin rubber and to perform kneading and dynamic crosslinking stably.
The halogen content of the halogenated alkylphenol formaldehyde resin is preferably 0.1 to 3.5% by mass, more preferably 1 to 3% by mass, and still more preferably 2.5 to 3% by mass. is there.
When the blending ratio of the halogenated alkylphenol formaldehyde resin having a halogen content of 3.5% by mass or less is less than 0.5% by mass, the elastic recovery of the olefinic thermoplastic elastomer is deteriorated, and when it exceeds 10% by mass, fish eyes are generated. At the same time, kneading and dynamic crosslinking cannot be performed stably.

5). Other raw materials Other raw materials added to the olefin-based thermoplastic elastomer are not particularly limited, and examples thereof include plasticizers for improving kneading and fillers for improving physical properties such as strength of molded products. Moreover, the other raw material may be mix | blended and does not need to be mix | blended.

6). Supercritical fluid The supercritical fluid is not particularly limited as long as it is a substance in a supercritical state, and examples include supercritical carbon dioxide and supercritical nitrogen.
Specifically, since carbon dioxide has a critical temperature of 31.1 ° C. (304.1 K) and a critical pressure of 7.38 MPa, supercritical carbon dioxide has a temperature of 31.1 ° C. or higher. And carbon dioxide in a state where the pressure is 7.38 MPa or more.
The amount of supercritical fluid introduced in the kneading step and the cross-linking step is not particularly limited, but is 0.05 to 100 parts by mass of the total amount of raw materials for obtaining an olefinic thermoplastic elastomer such as an olefinic thermoplastic resin. It is preferable that it is -30 mass parts, More preferably, it is 0.1-15 mass parts. If the amount introduced is less than 0.05 parts by mass, the melt viscosity of the mixture of the olefinic thermoplastic resin and the olefinic rubber during kneading and dynamic crosslinking is less likely to decrease. The amount of the olefinic thermoplastic elastomer obtained per hit is reduced and the productivity is deteriorated.

7). Kneading / Dynamic Cross-linking Equipment for kneading and dynamic cross-linking is not particularly limited, but equipment such as a twin-screw kneader, a single-screw kneader, or the like may be used continuously, or may be processed in a batch such as a pressure kneader. Equipment to do may be used. Moreover, kneading | mixing and dynamic crosslinking may be performed with the same installation, and may be performed with a different installation.
Moreover, kneading | mixing and dynamic cross-linking may be performed substantially in parallel, or dynamic cross-linking may be performed after kneading. Since the particles of the crosslinked rubber become smaller, it is more preferable to perform dynamic crosslinking after performing kneading to some extent.
In addition, since the thermal degradation of the olefinic thermoplastic resin and olefinic rubber during kneading and dynamic crosslinking can be suppressed, the temperature of the mixture of the olefinic thermoplastic resin and olefinic rubber during kneading and dynamic crosslinking is 150 ° C. or less. It is preferable that Further, the temperature of the mixture during kneading and the temperature of the mixture during dynamic crosslinking may be the same or different.

8). Molding Method The molding method of the molded body is not particularly limited, and examples thereof include a method used for molding a thermoplastic resin such as extrusion molding and injection molding.

9. Molded body The usage of the molded body is not particularly limited, but includes automotive exterior parts such as bumpers, cowl louvers, glass runs, opening trims, instrument panels, front pillars, consoles, center clusters, deck side trims, etc. For example, automobile interior parts.

  ADVANTAGE OF THE INVENTION According to this invention, the molded object of the olefin type thermoplastic elastomer which is excellent in the balance of elasticity (especially elastic recovery | restoration) and tensile strength, and does not have external appearance defects, such as a fish eye, The olefinic thermoplastic elastomer used for this molded object A composition and a method for producing the olefin-based thermoplastic elastomer composition can be provided.

2 is a micrograph of a cross section of a molded product of an olefinic thermoplastic elastomer of Example 1. It is a schematic diagram of the biaxial kneader used for kneading | mixing and dynamic bridge | crosslinking of the olefin type thermoplastic elastomer composition of this invention.

  As examples of the present invention, six types of molded products of olefinic thermoplastic elastomers and five types of molded products of olefinic thermoplastic elastomers as comparative examples were prepared, and measurement and evaluation were performed for each. As a result, the blending ratio (composition) and production conditions are shown in Table 1 below. The numbers in parentheses in the EPDM1 and EPDM2 columns are the blending ratio of EPDM, and the numbers in parentheses in the plasticizer column are the plasticizers combined with the plasticizers contained in EPDM1 or EPDM2. The total amount.

In the examples and comparative examples, the following raw materials were used.
Three types of polypropylene were used as the olefinic thermoplastic resin. Each polypropylene has a different MFR at a load of 21.18 N at 230 ° C., the MFR of PP1 is 0.6 (g / 10 min), and the MFR of PP2 is 1.5 (g / 10 min) , PP3 had an MFR of 6 (g / 10 min).
Two types of EPDM (ethylene-propylene-nonconjugated diene rubber) and EPM (ethylene-propylene rubber) were used as the olefin rubber. The EPDM was EPDM 1 with a Mooney viscosity of 51 at 125 ° C. and EPDM 2 with a Mooney viscosity of 66 at 120 ° C. EPDM1 contained 40% by mass of plasticizer (EPDM was 60% by mass), and EPDM2 contained 25% by mass of plasticizer (75% by mass of EPDM). The EPM had an MFR of 7 (g / 10 min) at a load of 21.18 N at 230 ° C.
As the crosslinking agent, two types of halogenated alkylphenol formaldehyde resins having different halogen contents were used. The plasticizer 1 had a halogen content of 2.8% by mass, and the plasticizer 2 had a halogen content of 3.6% by mass.
Further, as a plasticizer separately added in addition to the plasticizer in EPDM, a mineral oil having a kinematic viscosity at 40 ° C. of 96 mm ² / s (cSt) was used.

Each sample was manufactured as follows using the biaxial kneader shown in FIG.
PP, EPDM, EPM, and plasticizer in the blending ratio of each sample were charged from the hopper of a twin-screw kneader (“TEX30α” L / D: 60 from Nippon Steel).
While the raw material charged was mixed in the kneader tank and proceeded to the tip, carbon dioxide was introduced into the tank, and the mixed raw material was placed in the presence of supercritical carbon dioxide.
Then, on the way to the tip of the kneader while being kneaded in the presence of supercritical carbon dioxide, the crosslinking agent and the plasticizer were side-fed to perform dynamic crosslinking.
Thereafter, carbon dioxide was discharged from the deaeration port of the kneader to separate the carbon dioxide, and each sample was obtained.
In addition, after introducing supercritical carbon dioxide, until the dynamic crosslinking is completed, the temperature is 35 ° C. or higher and the pressure is 7.4 MPa or higher so that carbon dioxide can maintain a supercritical state. Managed.

  Measurement and evaluation of each sample were performed as follows.

(1) Manufacturing stability When manufacturing as described above, the case where the manufacturing can be performed continuously for 1 hour or more is marked as ◯, and the manufacturing can be performed continuously for 1 hour or more due to fluctuations in strand foaming or material discharge. The case where there was not was evaluated as x.

(2) Appearance of extruded product Each sample produced as described above was molded into an extruded sheet having a thickness of 1 mm at 200 ° C using a single screw extruder (L / D: 15). The number of fish eyes that appeared on the surface of the extruded sheet with a length of 500 mm was measured. The case where there was no fish eye was evaluated as ◯, the case where there were a few fish eyes was evaluated as Δ, and the case where there were many fish eyes was evaluated as ×.

(3) Average particle diameter of olefinic crosslinked rubber In the cross section near the center of the molded body, the area (cross sectional area) of each olefinic crosslinked rubber (particulate rubber) appearing in this cross section is measured, and the circle equivalent The diameter was determined, and this average value was taken as the average particle diameter of the olefinic crosslinked rubber.
Specifically, the vicinity of the center of the extruded sheet was cut in the thickness direction to form a measurement cross section, and the site of the olefinic crosslinked rubber appearing in the cross section was treated with a heavy metal and colored.
And the 15 * 15 micrometer range of the measurement cross section which colored the site | part of this olefin type crosslinked rubber was expanded using the scanning electron microscope. Image analysis processing (binarization processing) is performed on this enlarged image (see FIG. 1), and the occupancy area of the olefinic crosslinked rubber portion (portion lighter than the other portion in FIG. 1) in this image is specified. did.
The area of each occupying area of the olefin-based crosslinked rubber portion thus identified was calculated by image analysis, and the diameter of a circle having the same area as this area was obtained. And what averaged the value of the diameter calculated | required about each occupation area was made into the average particle diameter of olefin type crosslinked rubber.

(4) Compression set (elastic recovery)
In accordance with JIS K6301, a test was performed at a test temperature of 70 ° C. under a test time condition of 22 hours and measured.

(5) Tensile strength Measured according to JIS K6301.

From the above results, the comparative example was as follows.
Since Comparative Example 1 was not kneaded in the presence of supercritical carbon dioxide, the melt viscosity of the mixture increased, resulting in an increase in the temperature of the mixture in the kneaded part, and the crosslinking reaction could not be controlled. The reaction could not be performed, fish eyes were generated due to over-crosslinking, and the production was unstable due to the discharge of strands due to insufficient crosslinking.
In Comparative Example 2, fish eyes caused by over-crosslinking occurred by using a halogenated alkylphenol formaldehyde resin having a halogen content of 3.6% by mass as a crosslinking agent.
In Comparative Example 3, since the blending ratio of the olefin rubber was as small as 14.4% by mass, the olefinic crosslinked rubber was small and the elastic recovery was inferior.
In Comparative Example 4, the fish eye resulting from over-crosslinking occurred because the blending ratio of the crosslinking agent was as large as 12% by mass.
In Comparative Example 5, since the blending ratio of the crosslinking agent was as small as 0.4% by mass, the olefin-based crosslinked rubber was small and the elastic recovery was inferior.

On the other hand, all examples were as follows.
1) Since kneading and dynamic crosslinking were carried out in the presence of supercritical carbon dioxide, the increase in melt viscosity of the mixture was suppressed, and the temperature of the mixture was also 150 ° C. or less, so that the crosslinking reaction was optimized. It became possible to control, and foaming of the olefin rubber was suppressed, and EPDM could be stably crosslinked. Therefore, strand foaming and material discharge fluctuations did not occur, and it was possible to produce continuously for 1 hour or longer. In addition, fish eyes caused by overcrosslinking did not occur.
2) Since dynamic crosslinking is performed using a halogenated alkylphenol formaldehyde resin having a halogen content of 2.8% by mass as a crosslinking agent, it is possible to optimally control the crosslinking reaction, and fish resulting from overcrosslinking There was no eye.
3) Since the blending ratio of the olefinic rubber was 28 to 63.8% by mass, a sufficient olefinic crosslinked rubber was obtained, and the elastic recovery was good with a compression set value of 38% or less.
4) Since the blending ratio of the halogenated alkylphenol formaldehyde resin crosslinking agent having a halogen content of 2.8% by mass was 0.5 to 10% by mass, fish eyes caused by overcrosslinking did not occur, and sufficient An olefin-based crosslinked rubber was obtained, and the value of compression set was 38% or less, and the elastic recovery was good.
5) The value of compression set was 38% or less and the elastic recovery was good, and the value of tensile strength was 5.0 MPa or more, so the balance between elastic recovery and tensile strength was excellent.

  In addition, this invention is not limited to the said Example, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.

Claims (9)

A molded product of an olefinic thermoplastic elastomer containing an olefinic thermoplastic resin and an olefinic crosslinked rubber,
The olefin-based crosslinked rubber is obtained by crosslinking an olefin rubber with a halogenated alkylphenol formaldehyde resin,
The olefin rubber has a compounding ratio of 20 to 70% by mass,
The halogenated alkylphenol formaldehyde resin has a halogen content of 3.5% by mass or less and a blending ratio of 0.5 to 10% by mass,
The olefinic thermoplastic, characterized in that the olefinic thermoplastic resin and the olefinic rubber are kneaded and the olefinic rubber is dynamically crosslinked with the halogenated alkylphenol formaldehyde resin in the presence of a supercritical fluid. Elastomer molded body.   2. The molded product of an olefin-based thermoplastic elastomer according to claim 1, wherein the olefin-based crosslinked rubber is dispersed in particles having an average particle size of 1 μm or less in a continuous phase of the olefin-based thermoplastic resin. The olefinic thermoplastic resin is polypropylene,
The molded product of an olefinic thermoplastic elastomer according to claim 1 or 2, wherein the olefinic rubber contains at least EPDM. An olefinic thermoplastic elastomer composition comprising an olefinic thermoplastic resin and an olefinic crosslinked rubber,
The olefin-based crosslinked rubber is obtained by crosslinking an olefin rubber with a halogenated alkylphenol formaldehyde resin,
The olefin rubber has a compounding ratio of 20 to 70% by mass,
The halogenated alkylphenol formaldehyde resin has a halogen content of 3.5% by mass or less and a blending ratio of 0.5 to 10% by mass,
The olefinic thermoplastic, characterized in that the olefinic thermoplastic resin and the olefinic rubber are kneaded and the olefinic rubber is dynamically crosslinked with the halogenated alkylphenol formaldehyde resin in the presence of a supercritical fluid. Elastomer composition.   The olefinic thermoplastic elastomer composition according to claim 4, wherein the olefinic crosslinked rubber is dispersed in a particulate form having an average particle size of 1 µm or less in the continuous phase of the olefinic thermoplastic resin. The olefinic thermoplastic resin is polypropylene,
The olefinic thermoplastic elastomer composition according to claim 4 or 5, wherein the olefinic rubber contains at least EPDM. A kneading step of kneading an olefinic thermoplastic resin and an olefinic rubber having a compounding ratio of 20 to 70% by mass in the presence of a supercritical fluid;
A crosslinking step of dynamically crosslinking the olefin rubber in the presence of a supercritical fluid,
In the crosslinking step, a halogenated alkylphenol formaldehyde resin having a halogen content of 3.5% by mass or less is used as a crosslinking agent.
The method for producing an olefin-based thermoplastic elastomer composition, wherein a blending ratio of the halogenated alkylphenol formaldehyde resin is 0.5 to 10% by mass.   The method for producing an olefinic thermoplastic elastomer composition according to claim 7, wherein the temperature of the mixture of the olefinic thermoplastic resin and the olefinic rubber in the kneading step and the crosslinking step is 150 ° C or lower. The olefinic thermoplastic resin is polypropylene,
The method for producing an olefinic thermoplastic elastomer composition according to claim 7 or 8, wherein the olefinic rubber contains at least EPDM.