JP2006206628A - Thermoplastic elastomer composition and its molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molded product having low impact resilience in wide temperature range, particularly at high temperature and low temperature and a thermoplastic elastomer composition having high fluidity. <P>SOLUTION: The thermoplastic elastomer composition comprises at least one kind of thermoplastic resin and at least one kind of particulate rubber dispersed into the thermoplastic resin. In the elastomer composition, the ratio of the thermoplastic resin to the rubber is (85/15) to (45/55) and the ratio of the thermoplastic resin having 30-80°C glass transition temperature to total of the thermoplastic resin and the rubber is ≥30 mass% and the ratio of the rubber having -40 to -10°C glass transition temperature to the total of the thermoplastic resin and the rubber is ≥15 mass% and when the thermoplastic elastomer composition is softened, melt index is ≥15g/10 min. The molded product is obtained by using the thermoplastic elastomer composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermoplastic elastomer composition and a molded body thereof.

Currently, a hard disk drive widely used is one of digital devices indispensable for personal computers.
A general hard disk drive has a large number of magnetic disks (platters), spindle motors, and actuators (positioning devices) arranged on a base. Further, a control board is arranged on the back side of the base.
The magnetic disk is attached to the spindle motor and rotates at a high speed.
Examples of the actuator include a swing type actuator that swings about a rotation axis. This swing type actuator has a hard disk arm composed of a magnetic head (the magnetic head reads and writes data to and from a rotating magnetic disk) and a plurality of swing arms. The magnetic head is supported at each end of the plurality of stacked swing arms. The swing arm is used so as to sandwich a disk-shaped rotating disk. The magnetic head is moved in the radial direction of the rotating disk by turning the hard disk arm about the rotating shaft. In this way, the magnetic head can reach the recording track at an arbitrary position on the rotating disk.
Furthermore, in order to drive the hard disk arm to turn, a coil and a permanent magnet are arranged at the rear of the hard disk arm. The permanent magnet is disposed around the coil. In order to drive the hard disk arm to swing, first, an appropriate magnetic field is formed around the coil by a permanent magnet. If the coil is appropriately energized, a driving force according to Fleming's left-hand rule acts on the coil, and the hard disk arm is pivoted.

When the hard disk drive having such a configuration is operated, the spindle motor rotates at a high speed, and the swing arm repeats turning. Therefore, the hard disk drive is vibrated vigorously and abnormal noise is likely to be generated.
For this reason, many vibration damping materials and vibration damping materials are used in hard disk drives. For example, stopper rubbers are arranged one by one on the left and right of the rear part of the hard disk arm of the swing type actuator. The hard disk arm collides with the stopper rubber to reliably stop the movement of the hard disk arm, and to suppress vibration that occurs when the hard disk arm collides with the stopper rubber.

However, since the conventional stopper rubber is made of polyurethane, if the temperature inside the hard disk drive rises as the hard disk drive starts up, the resilience of the stopper rubber increases, and at the same time the vibration damping and vibration proofing properties decrease. Was.
For this reason, even if the hard disk arm moves and hits the stopper rubber, the hard disk arm bounces back to the opposite side due to its high rebound resilience, and the hard disk arm cannot be stopped.
In order to solve such a problem, Patent Document 1 describes an alternative to a hard disk drive stopper rubber formed by molding a polymer composition in which an active ingredient that increases the amount of dipole moment of the polymer is blended with a thermosetting polymer. Things are listed.
Next, Patent Document 2 discloses an electronic apparatus comprising an elastomer member made of styrene-ethylene-butylene-styrene block copolymer formed into a cylinder, and a shaft member for attachment to a case inserted into the cylinder. An anti-vibration member and a method for manufacturing the same are described. The anti-vibration member for an electronic device and the manufacturing method thereof in Patent Document 2 are rubber materials that do not affect the electronic device, maintain the anti-vibration function for a long period of time, serve as a stopper for the head stack assembly, and have a permanent distortion. The aim is to use very little rubber material.

JP 2002-184136 A JP 2002-21930 A

  However, the hard disk drive stopper rubber substitute described in the above-mentioned Patent Document 1 is replaced with a hard disk drive of a device or device (for example, a car stereo such as a CD, MD, DVD, or car navigation) mounted on an automobile. In addition to the temperature rise caused by starting the hard disk, the temperature inside the automobile rises to a high temperature such as about 60 to 80 ° C., so that the impact resilience of the stopper rubber substitute is increased. However, there is a problem that the hard disk arm cannot be stopped.

Next, when the vibration isolator for electronic devices described in Patent Document 2 is used for a hard disk drive of a device, apparatus, or the like mounted in an automobile, as in Patent Document 1, the interior of the automobile When the temperature becomes high as described above, the rebound resilience of the vibration isolator for electronic equipment increases and there is a problem that the hard disk arm cannot be stopped. Moreover, since the said vibration isolator for electronic devices is a cylindrical elastomer member on the outer side and the inner shaft member is a metal, it has poor anti-vibration properties.
In addition, anti-vibration rubber used for automobiles is generally required to function in a wide temperature range of −40 to 100 ° C., and is used in hard disk drives such as equipment and devices mounted on automobiles. The stopper rubber must also have low rebound resilience over a wide temperature range from low to high.

  Accordingly, an object of the present invention is to provide a molded article having low rebound resilience in a wide temperature range, in particular, low rebound resilience at high and low temperatures, and to realize the molded body, and It is an object of the present invention to provide a composition that has high properties and can easily form a good molded article by injection molding.

  The inventor of the present invention is a molded article having low impact resilience in a wide temperature range, in particular, low impact resilience at high and low temperatures, and a composition capable of forming such a molded article. As a result of diligent research on a composition that is high and can easily form a good molded article by injection molding, first, it contains at least one thermoplastic resin and at least one rubber, Among the rubbers, it is obtained from a thermoplastic resin elastomer composition containing a specific ratio of a thermoplastic resin having a glass transition temperature of 30 to 80 ° C. and a rubber having a glass transition temperature of −40 to −10 ° C. It has been found that the molded article has low impact resilience over a wide temperature range, and particularly low resilience at high and low temperatures.

Further, the present inventor blends the thermoplastic resin and the rubber in a specific ratio, and the thermoplastic resin elastomer composition has a specific melt index, so that the thermoplastic resin is softened. The thermoplastic resin elastomer composition has high fluidity, and a good molded article can be easily molded by injection molding using the thermoplastic resin elastomer composition as a raw material. I found it.
The present inventor completed the present invention based on these findings.

That is, the present invention provides the following (1) to (8).
(1) A thermoplastic elastomer composition comprising at least one thermoplastic resin and at least one particulate rubber dispersed in the thermoplastic resin,
The ratio of the thermoplastic resin and the rubber is 85/15 to 45/55,
Of the thermoplastic resin and the rubber, the proportion of the rubber having a glass transition temperature of 30 to 80 ° C. is 30% by mass or more and the glass transition temperature of −40 to −10 ° C. Is 15% by mass or more,
A thermoplastic elastomer composition having a melt index of 15 g / 10 min or more when the thermoplastic elastomer composition is softened.

(2) The thermoplastic elastomer composition according to the above (1), which contains polyamide 11 and / or polyamide 12 as the thermoplastic resin having a glass transition temperature of 30 to 80 ° C.
(3) The thermoplastic elastomer composition according to the above (1) or (2), wherein at least a part of the rubber is crosslinked.
(4) A molded article formed using the thermoplastic elastomer composition according to any one of (1) to (3).

(5) The molded body according to (4), wherein the molded body is molded by injection molding.
(6) The molded article according to (4) or (5), wherein the molded article has a rebound resilience at -20 to 80 ° C of less than 70%.
(7) A vibration-proof material comprising the molded article according to any one of (4) to (6).
(8) The vibration isolator according to (7), which is for a hard disk drive.

The molded product of the present invention has low rebound resilience in a wide temperature range from low temperature to high temperature, and particularly low rebound resilience at high temperatures and low temperatures.
Further, the thermoplastic elastomer composition of the present invention has high fluidity, excellent moldability, and can easily form a good molded article by injection molding or the like.

Hereinafter, the present invention will be described in detail.
First, the thermoplastic elastomer composition of the present invention will be described.
The thermoplastic elastomer composition of the present invention comprises:
A thermoplastic elastomer composition comprising at least one thermoplastic resin and at least one particulate rubber dispersed in the thermoplastic resin,
The ratio of the thermoplastic resin and the rubber is 85/15 to 45/55,
Of the thermoplastic resin and the rubber, the proportion of the rubber having a glass transition temperature of 30 to 80 ° C. is 30% by mass or more and the glass transition temperature of −40 to −10 ° C. Is 15% by mass or more,
When the thermoplastic elastomer composition is softened, the thermoplastic elastomer composition has a melt index of 15 g / 10 min or more.

The thermoplastic resin contained in the thermoplastic elastomer composition of the present invention will be described below.
The thermoplastic elastomer composition of the present invention contains at least one thermoplastic resin. Moreover, the ratio of the said thermoplastic resin and the said rubber | gum is 85 / 15-45 / 55, and the ratio of the thermoplastic resin which has a glass transition temperature of 30-80 degreeC among the said thermoplastic resin and the said rubber | gum is. 30% by mass or more.

  It is more preferable that the thermoplastic resin having a glass transition temperature of 30 to 80 ° C. has a glass transition temperature of 40 to 60 ° C., particularly considering vibration damping properties and / or vibration isolation properties at high temperatures. This is because the glass transition temperature of a thermoplastic resin corresponds to the temperature at the peak of the absorption energy of the thermoplastic resin. When the glass transition temperature of the thermoplastic resin is, for example, about 60 ° C., the thermoplastic resin has the largest absorbed energy at about 60 ° C., and therefore the rebound resilience of the thermoplastic resin is the lowest at about 60 ° C. Become.

  In the present invention, the glass transition temperature refers to the temperature at which the thermoplastic resin and rubber transition from glassy to rubbery. In the present invention, a dynamic viscoelasticity test was performed on each material, a temperature dependence curve of tan δ was obtained under the condition of 20 Hz, and the temperature at which the curve showed a peak was used as the glass transition temperature.

  Examples of the thermoplastic resin having a glass transition temperature of 30 to 80 ° C. include polyamide resin, polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, and ABS. Of these, polyamide resin is preferable.

Specific examples of the polyamide resin include polylactams such as polyamide 6 (nylon 6), polyamide 7 (nylon 7), polyamide 8 (nylon 8), polyamide 11 (nylon 11), polyamide 12 (nylon 12);
Amino acid homopolymers such as polyamide 4 (nylon 4, polypyrrolidinone);
A copolyamide of dicarboxylic acid and diamine such as polyamide 46 (nylon 46), polyamide 66 (nylon 66), polyamide 69 (nylon 69), polyamide 610 (nylon 610), polyamide 612 (nylon 612);

Aromatic and partially aromatic polyamides such as polyamide 6I (nylon 6I) (I: isophthalic acid), polyamide 6T (nylon 6T) (T: terephthalic acid), polyamide MXD6 (nylon MXD6) (MXD: metaxylylenediamine);
Polyamide 6/66 (nylon 6/66) copolymer, polyamide 6/66/610 (nylon 6/66/610) copolymer, polyamide 6 / 6T (nylon 6 / 6T) copolymer, polyamide 66 / PP (nylon 66 / PP) copolymer, polyamide 66 / PPS (nylon 66 / PPS) copolymer, polyamide elastomer and the like.

  Among these polyamide resins, polyamide 11 and polyamide 12 are preferable because they are rich in flexibility and used for electronic devices and the like because of long-term requirements for heat resistance and water resistance.

  The thermoplastic resins having a glass transition temperature of 30 to 80 ° C. can be used alone or in combination of two or more.

And it is one of the suitable aspects that the thermoplastic resin contained in the thermoplastic elastomer composition of this invention consists only of a thermoplastic resin which has such a glass transition temperature of 30-80 degreeC.
Moreover, the thermoplastic resin contained in the thermoplastic elastomer composition of this invention can contain the thermoplastic resin which has glass transition temperature other than 30-80 degreeC as needed. The thermoplastic resin having a glass transition temperature other than 30 to 80 ° C. is not particularly limited as long as it is a thermoplastic resin having a glass transition temperature lower than 30 ° C. or a thermoplastic resin having a glass transition temperature higher than 80 ° C. .

  Examples of such thermoplastic resins include polyolefin resins, polyether resins, polynitrile resins, polymethacrylate resins, polyvinyl resins, polycellulose resins, polyimide resins, polyacetal resins, polysulfone resins, and polyphenylene sulfide resins. The thermoplastic resins can be used alone or in combination of two or more.

The rubber contained in the thermoplastic elastomer composition of the present invention will be described below.
The rubber contained in the thermoplastic elastomer composition of the present invention is at least one particulate rubber dispersed in the thermoplastic resin. Moreover, the ratio of the said thermoplastic resin and the said rubber | gum is 85 / 15-45 / 55, and the ratio of the rubber | gum which has a glass transition temperature of -40--10 degreeC among the said thermoplastic resin and the said rubber | gum is 15. It is at least mass%.

  When the thermoplastic elastomer composition of the present invention contains a rubber having a glass transition temperature of −40 to −10 ° C., the molded product obtained from the thermoplastic elastomer composition of the present invention can be operated in an electronic device, an apparatus, or the like. At the start, excellent vibration damping and / or vibration isolation can be achieved at low temperatures. Since normal electronic devices are used in a temperature range of −20 ° C. or higher, the glass transition temperature of rubber is −40 to −10 ° C., and −25 to − It is preferably 10 ° C.

  Regarding the glass transition temperature of rubber, a dynamic viscoelasticity test was performed for each material, a temperature dependence curve of tan δ was obtained under the condition of 20 Hz, and the temperature at which the curve showed a peak was used as the glass transition temperature.

  Examples of rubber having a glass transition temperature of −40 to −10 ° C. include acrylic rubber, acrylonitrile butadiene rubber (NBR), modified NBR, hydrogenated NBR, chloroprene rubber (CR), hydrin rubber (CHR), and chlorosulfonated polyethylene. (CSM) and chlorinated polyethylene (CM).

  Among these, NBR that can control the glass transition temperature by the amount ratio of acrylonitrile and butadiene is preferable in terms of material design. Moreover, NBR modified with a carboxy group or the like is more preferable because of high compatibility with thermoplastic resins.

The rubber is preferably at least partially crosslinked. Thereby, the physical property of a molded object improves and it can stabilize thermally.
Examples of the rubber that is at least partially crosslinked include a crosslinked rubber obtained by previously crosslinking the above rubber, a dynamically crosslinked rubber, and the like. Of these, dynamically crosslinked rubber is preferred. The crosslinked rubber can be produced by a known method. The rubber that is at least partially dynamically crosslinked will be described later.
Said rubber | gum can be used individually or in combination of 2 or more types.

  And in the thermoplastic elastomer composition of this invention, rubber | gum is a particulate form and is disperse | distributing in the thermoplastic resin. The particulate rubber as the dispersed phase is preferably 10 μm to 0.1 μm in diameter and more preferably 2 to 0.5 μm in diameter from the viewpoint of fluidity and physical properties.

  When the particulate rubber is dispersed in the thermoplastic resin, the fluidity of the thermoplastic elastomer composition is lowered. In addition, the smaller the particle size of the particulate rubber, the worse the fluidity of the thermoplastic elastomer composition. However, when the rubber particle size is too large, the strength of the thermoplastic elastomer is extremely reduced, so that a balance is necessary.

The ratio of the thermoplastic resin and rubber contained in the thermoplastic elastomer composition is 85/15 to 45/55. A preferred ratio is 80/20 to 50/50, more preferably 70/30 to 55/45. In such a range, the thermoplastic elastomer composition has high fluidity and good injection moldability, and the resulting molded product has few defects such as sink marks. In such a range, the rebound resilience of the molded product obtained from the thermoplastic elastomer composition can be kept low over a wide range of temperatures, and in particular, the rebound resilience at high and low temperatures can be lowered.
In addition, the ratio of the thermoplastic resin and rubber | gum contained in a thermoplastic elastomer composition is mass ratio.

  In the thermoplastic elastomer composition of the present invention, the ratio of the thermoplastic resin having a glass transition temperature of 30 to 80 ° C. of the thermoplastic resin and the rubber is 30% by mass or more and 55 to 85% by mass. Is preferred. In such a range, the molded product obtained from the thermoplastic elastomer composition has low impact resilience at high temperatures.

  Moreover, in the thermoplastic elastomer composition of the present invention, the ratio of the rubber having a glass transition temperature of −40 to −10 ° C. of the thermoplastic resin and the rubber is 15% by mass or more, and 30 to 45% by mass. Is preferred. In such a range, the impact resilience on the low temperature side can be lowered.

  The thermoplastic elastomer composition of the present invention has a melt index of 15 g / 10 min or more when the thermoplastic elastomer composition is softened. The melt index of the thermoplastic elastomer composition is preferably 20 to 50 g / 10 min, more preferably 20 to 30 g / 10 min. Those having a low melt index hinder mass production because of low fluidity, and those having a high melt index make the part extremely brittle. When it is in the above range, the thermoplastic elastomer composition has high fluidity and good moldability, and the resulting molded product has few defects such as sink marks.

  Further, the temperature of the thermoplastic resin when the thermoplastic elastomer composition is softened may be higher than the melting temperature of the thermoplastic resin, and can be appropriately selected depending on the kind and blending amount of the thermoplastic resin. In one preferred embodiment, the temperature of the thermoplastic resin when such a thermoplastic elastomer composition is softened is, for example, not less than the melting temperature of the thermoplastic resin and not more than (melting temperature + 40 ° C.). Specifically, when polyamide 11 is used as the thermoplastic resin, since the melting point of polyamide 11 is 195 ° C., molding at 220 to 230 ° C. is preferable. Within such a range, the melt index of the thermoplastic elastomer composition can be increased.

  Moreover, as for the thermoplastic elastomer composition as a whole, one preferred embodiment is that the heating temperature is 260 ° C. or lower. If it is such a range, the burn of a thermoplastic resin or rubber | gum can be prevented.

  In addition, melt index (MI value) passed the orifice for a fixed time under the load of 21.18N (2.16kgf), after heating a sample at specific temperature (230 degreeC) using the melt indexer. This is a value obtained by measuring the mass of the molten sample and converting it to the number of grams per 10 minutes.

In the thermoplastic elastomer composition of the present invention, it is desirable that the thermoplastic resin and the rubber satisfy the formula [φ _R / φ _A ] × [η _A / η _R ] <1.0. In the formula, φ _{R represents} the volume fraction of rubber, φ _{A represents} the volume fraction of the thermoplastic resin, η _{R represents} the melt viscosity of the rubber during kneading, and η _A represents the melt viscosity of the thermoplastic resin during kneading.
When the thermoplastic resin and the rubber are kneaded and satisfy the formula [φ _R / φ _A ] × [η _A / η _R ] <1.0, the thermoplastic resin wraps around the rubber and the rubber forms a domain. It becomes like this.

In this case, the morphology is such that rubber is present as fine particulate domains in a thermoplastic resin matrix. Such morphology is due to the melt viscosity of the thermoplastic resin and rubber. Here, in order to further improve the physical properties, it is desirable that the melt viscosity ratio between the rubber and the thermoplastic resin is 0.8 <η _R / η _A <1.2. In addition, it is desirable that the melt viscosity ratio of the thermoplastic elastomer composition composed of the thermoplastic resin and rubber and the thermoplastic resin is 0.8 <η _E / η _A <1.2. In the formula, η _E represents the melt viscosity of the thermoplastic elastomer composition during kneading.

Here, the melt viscosity refers to any temperature and melt viscosity of components during kneading. The melt viscosity of the polymer material is dependent on temperature, shear rate (sec ⁻¹ ) and shear stress. For this reason, in general, the stress and shear rate of the polymer material in an arbitrary temperature in the molten state flowing through the narrow tube, particularly in the temperature range during kneading, are measured, and the melt viscosity η is calculated from the following equation (1). .

  In the thermoplastic elastomer composition of the present invention, in addition to the thermoplastic resin and rubber described above, the scope of the present invention is not impaired in order to improve the fluidity, heat resistance, physical strength, cost, etc. of the thermoplastic resin. Thus, a necessary amount of a compounding agent added to a normal composition such as a reinforcing agent, a filler, a softening agent, an anti-aging agent, an anti-deterioration agent, or a processing aid can be added. Furthermore, an inorganic pigment or an organic pigment can be added to the thermoplastic resin for the purpose of coloring or the like.

  Moreover, the preparation method of a thermoplastic elastomer composition is not specifically limited. Examples of the preparation method include a method in which a thermoplastic resin and unvulcanized rubber are previously supplied to a kneader and melt-kneaded.

  Addition of various compounding agents to the thermoplastic resin or unvulcanized rubber is, for example, a method performed during the melt-kneading operation between the thermoplastic resin and the unvulcanized rubber, or the thermoplastic resin and the unvulcanized rubber. The method of performing separately before melt-kneading with, etc. is mentioned. Among these, it is preferable to separately mix the thermoplastic resin and the unvulcanized rubber before melt-kneading.

When at least a part of the rubber is cross-linked, it is preferable to prepare the thermoplastic elastomer composition by dynamic cross-linking as follows.
In the preparation method of the thermoplastic elastomer composition by dynamic crosslinking, first, the thermoplastic resin and the unvulcanized rubber to which various compounds are separately added in advance are melted using, for example, a twin-screw kneader or the like. At the same time or afterwards, the vulcanizing agent (further vulcanization aid) is added and further kneaded. Here, the rubber is dynamically cross-linked in the presence of a thermoplastic resin. That is, the rubber is kneaded and dispersed in the thermoplastic resin so that the crosslinking proceeds in a fine particle state. In the thermoplastic elastomer composition prepared by such a method, rubber at least partially crosslinked as a dispersed phase (domain) is stably dispersed in a thermoplastic resin forming a continuous phase (matrix). State. Thus, the thermoplastic elastomer composition has high fluidity when the thermoplastic resin is softened.

  In addition to the above, the timing of addition of the vulcanizing agent is, for example, previously mixed with other compounding agents in the rubber, and during the kneading of the thermoplastic resin and the rubber, crosslinking is performed, Rubber can also be dynamically crosslinked.

What is necessary is just to determine suitably the vulcanizing agent used for dynamic bridge | crosslinking of rubber | gum, a vulcanization | cure adjuvant, vulcanization | cure conditions (temperature, time), etc. according to the rubber composition to be used.
A general rubber vulcanizing agent (crosslinking agent) can be used as the vulcanizing agent.
Examples of rubber vulcanizing agents (crosslinking agents) include sulfur-based, organic peroxide-based, phenol resin-based vulcanizing agents.

Examples of the sulfur vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, alkylphenol disulfide, and the like.
In the case of using a sulfur-based vulcanizing agent, the amount used is, for example, an amount that is in a ratio of 0.5 to 4 phr (parts by mass per 100 parts by mass of rubber, hereinafter the same) is a preferred embodiment.

Examples of the organic peroxide vulcanizing agent include benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy). ) Hexane and the like.
In the case of using an organic peroxide vulcanizing agent, the amount used is, for example, one of preferred embodiments in an amount of 1 to 15 phr.

Examples of the phenol resin vulcanizing agent include bromides of alkylphenol resins;
Examples thereof include a mixed crosslinking system containing a halogen donor such as tin chloride and chloroprene and an alkylphenol resin.
In the case where a phenol resin vulcanizing agent is used, the amount used is, for example, one of the preferred embodiments in an amount of 1 to 20 phr.

  Further, as vulcanization aids, for example, magnesium oxide, risurge, p-quinonedioxime, p-dibenzoylquinonedioxime, tetrachloro-p-benzoquinone, poly-p-dinitrosobenzene, methylindianiline, etc. are used. can do.

  Moreover, you may add a vulcanization accelerator to rubber | gum as needed. Examples of the vulcanization accelerator used include general vulcanization accelerators such as aldehyde / ammonia, guanidine, thiazole, sulfenamide, thiuram, dithioate, and thiourea. What is necessary is just to use the usage-amount of such a vulcanization accelerator about 0.5-2phr, for example.

Specific vulcanization accelerators include, for example, aldehyde / ammonia vulcanization accelerators such as hexamethylenetetramine;
Guanidine vulcanization accelerators such as diphenylguanidine;
Thiazole vulcanization accelerators such as dibenzothiazyl disulfide (DM), 2-mercaptobenzothiazole and its Zn salt, cyclohexylamine salt;
Cyclohexylbenzothiazylsulfenamide (CBS), N-oxydiethylenebenzothiazyl-2-sulfenamide, Nt-butyl-2-benzothiazolesulfenamide, 2- (thymolpolynyldithio) benzothiazole Sulfenamide vulcanization accelerators such as

Thiuram vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetramethylthiuram monosulfide (TMTM), dibentamethylene thiuram tetrasulfide;
Zn-dimethyldithiocarbamate, Zn-diethyldithiocarbamate, Zn-di-n-butyldithiocarbamate, Zn-ethylphenyldithiocarbamate, Tc-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, pipecorinpi Dithioate vulcanization accelerators such as pecolyl dithiocarbamate;
And thiourea vulcanization accelerators such as ethylenethiourea and diethylthiourea.

  The vulcanization accelerator can be used in combination with a general vulcanization accelerator. As the vulcanization acceleration aid, for example, zinc white (about 0.2 to 6 phr), stearic acid, oleic acid, and their Zn salts (about 0.1 to 3 phr) can be used.

  In addition to these, the rubber may include, for example, an anti-aging agent, an anti-degradation agent, an antioxidant, an ultraviolet ray inhibitor, a colorant such as a pigment or a dye, a reinforcing agent such as carbon black or silica, and the like. May be included.

  In addition, when the dynamically crosslinked rubber is difficult to disperse in the thermoplastic resin in the form of micro particles, it is possible to compatibilize both by using an appropriate compatibilizing method, for example. Examples of such a compatibilizing method include a method of mixing a compatibilizer in the system. By mixing the compatibilizer, the interfacial tension between the thermoplastic resin and the rubber decreases, and as a result, the particle diameter of the rubber forming the dispersed phase becomes fine. Thereby, both the characteristics of a thermoplastic resin and rubber are expressed more effectively.

  Examples of the compatibilizer include, for example, a thermoplastic resin, a copolymer having a rubber structure or a rubber structure, an epoxy group capable of reacting with the thermoplastic resin or rubber, a carboxyl group, a carbonyl group, a halogen group, an amino group, Examples thereof include those having a copolymer structure having an oxazoline group, a hydroxyl group, and the like. Such a compatibilizer can be selected according to the kind of thermoplastic resin and rubber to be mixed.

  Specific compatibilizers include, for example, styrene / ethylene / butylene / styrene block copolymers (SEBS) and their maleic acid modified products, EPDM, EPM and their maleic acid modified products, EPDM / styrene or EPDM. / Acrylonitrile graft copolymer and its modified maleic acid, styrene / maleic acid copolymer, reactive phenoxin and the like.

  When the compatibilizing agent is blended in the thermoplastic elastomer composition of the present invention, the blending amount of the compatibilizing agent is 0.5 to 20 parts by mass with respect to 100 parts by mass in total of the thermoplastic resin and the rubber. This is one of the preferred embodiments.

  The kneader used for kneading the thermoplastic resin and rubber is not particularly limited, and examples thereof include a screw extruder, a kneader, a Banbury mixer, and a biaxial kneading extruder. In a preferred embodiment, a twin-screw kneading extruder is used for kneading the thermoplastic resin and rubber and dynamic crosslinking of the rubber. Two or more types of kneaders may be used and kneaded sequentially.

  As conditions for melt-kneading, the temperature may be equal to or higher than the temperature at which the thermoplastic resin melts, and is preferably 200 to 250 ° C. In such a temperature range, the fluidity of the thermoplastic elastomer composition is high, and the rubber is dispersed in the form of particles in the thermoplastic resin, so that the thermoplastic resin or rubber can be prevented from being burned.

The shear rate during kneading is preferably 500 to 5000 sec ⁻¹ .
In one preferred embodiment, the entire kneading time is, for example, 30 seconds to 10 minutes. Moreover, it is one of the suitable aspects that the vulcanization time after adding a vulcanizing agent is, for example, 15 seconds to 5 minutes.

The molding method of the thermoplastic elastomer composition of the present invention will be described below.
Examples of the molding method include injection molding, extrusion molding, and hollow molding. Of these, injection molding is preferred.

  As an injection molding machine used for injection molding of a molded body, for example, a conventionally known injection molding machine can be used. As an injection molding machine for injection molding a molded body, for example, an injection device constituting the injection molding machine may have either an inline type or a pre-plastic type structure. Further, the mold clamping device constituting the injection molding machine may have either a direct pressure type or a toggle type structure. Further, the injection device and the mold clamping device may be arranged in either a horizontal type or a vertical type. Further, the driving method of the injection device may be a hydraulic type, an electric type or a hybrid type.

Further, as a mold clamping mechanism in the injection molding machine, methods such as injection compression and core compression can be used.
Further, an injection molding machine having a mechanism for performing molding by reducing the pressure inside the mold cavity can also be used. When injection molding is performed while reducing the pressure in the mold cavity, the amount of residue remaining in the mold due to volatile components or heat processing can be extremely reduced. Therefore, the method of performing injection molding while reducing the pressure in the cavity of the mold is one of the preferred embodiments in order to contribute to the improvement of the quality of the molded body and the extension of the mold maintenance interval.

  In the molding process using such an injection molding machine, the cylinder diameter and the clamping force are appropriately determined according to the shape of the molded body to be molded. Generally, when the projected area of the molded body to be molded is large, it is preferable to increase the clamping force. Moreover, when the capacity | capacitance of a molded object is large, it is one of the preferable aspects to enlarge a cylinder diameter.

  The molding conditions for the molding process vary depending on the type of injection molding machine used, the shape of the molded body to be molded, and the like. In general, when the molded body is thin, molding is performed under high-speed and low-pressure molding conditions, and when the molded body is thick, molding is performed under low-speed and high-pressure molding conditions.

  The temperature of the thermoplastic resin in the molding process using the injection molding machine is preferably set in the range of (Tm + 20) to (Tm + 50) ° C., where Tm is the softening temperature (melting point) of the thermoplastic resin.

  In molding using an injection molding machine, as a technique for stably injection molding a molded body with an injection molding machine (that is, a technique for minimizing deterioration of thermoplastic resin due to thermal history during processing or shearing) For example, it is one of preferred embodiments to use a method of reducing the pressure in the cylinder and / or the hopper or filling an inert gas such as nitrogen or argon.

  In addition, multilayer molding, two-color molding, insert molding, and the like can be performed with other organic polymers or inorganic substances.

Next, an injection molding die attached to the injection molding machine will be described.
As the injection mold, one made of a known steel material can be used. Depending on the purpose, the surface of the mold may be coated with, for example, a chromium-based, titanium-based, boron-based, or carbon-based material.

  When it is necessary to form a pattern or the like on the surface of the molded body to be molded, a desired steel pattern is formed by forming a soft steel layer such as nickel on the inner surface of the mold and cutting the soft steel layer. A method of forming a pattern shape corresponding to the target, a method of forming a pattern shape corresponding to the target pattern by electroforming on the inner surface of the mold, and an etching process on the inner surface of the mold A method of forming a pattern shape to be formed, a method of forming a pattern shape corresponding to a target pattern by sandblasting on the inner surface of the mold, a method of forming a pattern shape corresponding to the target pattern by using a stamper, etc. It is possible to use.

Examples of the mold assembly structure include a two-piece cracking structure, a three-piece cracking structure, and a nested structure, depending on the molded body to be molded, the gate, the sprue, the number of workpieces, and the like.
As the protruding mechanism in the mold, for example, a method of using a pin or the like, a method of protruding the entire core, a method of lifting with air or the like can be used. Moreover, in order to make taking out easy, it is also possible to make a cavity end part into a slide core structure. Also, the ejector ejector may be structured to automatically return with a spring. Also, a bearing structure can be adopted to make the ejector operate smoothly.

Next, the temperature control of the mold can be performed by a known method using, for example, water, high-pressure water, an oil medium, an electric heater, electromagnetic heating, or the like.
Moreover, the gate shape in a metal mold | die is not specifically limited, According to the shape etc. of the molded object which should be formed, it can select suitably from a direct gate, a film gate, a fan gate, a pin gate, a submarine gate, etc. In order to reduce the mechanical distortion of the material, it is one of preferred embodiments to use the shape of a film gate or a fan gate. In order to disperse the distortion, it is also a preferable aspect to adopt a shape in which a diaphragm is provided in the middle of the gate. Furthermore, it is possible to use a known runner such as a hot runner.

  Secondary processing can be performed on the molded body formed by injection molding as described above. Secondary processing includes, for example, anti-reflection processing, hard coat processing, aluminum deposition processing, adhesion processing, thermal fusion processing, ultrasonic fusion processing, electromagnetic fusion processing, corona discharge processing, cutting, surface pattern pressing, surface Examples include cutting, painting, and pattern printing.

Next, the molded product of the present invention will be described.
The molded article of the present invention is obtained by using the thermoplastic elastomer composition as a raw material.
Examples of the molding method include injection molding, extrusion molding, and hollow molding. Of these, injection molding is preferred. Specific methods and conditions for injection molding are as described above.

  Moreover, it is preferable that the impact resilience rate in the -20-20 degreeC of the molded object of this invention is less than 70%, and it is more preferable that it is less than 50%. By maintaining a low impact resilience of less than 70% in such a wide temperature range, the molded body has excellent vibration damping properties and / or vibration proof properties in a wide temperature range from low temperature to high temperature. It becomes.

  And the molded object of this invention suppresses the impact resilience in high temperature like 60-80 degreeC low, and has the outstanding vibration suppression and / or vibration proofing property in high temperature.

  The molded article of the present invention has vibration proofing and vibration damping properties over a wide temperature range, and particularly has excellent vibration proofing and vibration damping properties at high temperatures. It can be suitably used as a vibration damping material, a vibration damping material or the like. Specific examples of the vibration isolating material include, for example, a vibration isolating material for a hard disk drive. Especially, it can use suitably as a vibration isolator for hard disk drives, such as an apparatus and an apparatus mounted in a motor vehicle. Examples of devices and apparatuses mounted on automobiles include car stereos such as CD, MD, and DVD, and car navigation.

  In the vibration damping material or the vibration damping material, the shape, size, part formed by the thermoplastic elastomer composition, etc. are not particularly limited, and the location of the vibration damping material or the vibration damping material, the required damping / The frequency can be selected as appropriate based on the frequency and temperature range for exhibiting vibration isolation, amplitude, load bearing performance, and the like.

In the case where the vibration damping material or the vibration damping material is a vibration damping material for a hard disk drive such as a device or apparatus mounted on an automobile, examples of the shape include a cylinder and a cylindrical shape.
When the shape is a cylinder, the size is, for example, from about 2 mm in height and about 1 mm in diameter to about 10 mm in height and about 15 mm in diameter.
When the shape is a cylindrical shape, the size is, for example, from about 2 mm in height, about 1 mm in diameter, and about 1 mm in inner diameter to about 10 mm in height and 15 mm in diameter.

  In addition to this, the molded article of the present invention can greatly suppress noise and vibration caused by transportation such as automobiles. In addition, it is possible to satisfy the advanced requirements of low vibration and low noise inside the automobile. In addition, it is possible to reduce noise and vibration generated from office machines that are widely used in general households such as copying machines and printers. Furthermore, it is possible to reduce vibrations generated by household electrical appliances such as refrigerators, washing machines, and vacuum cleaners that are becoming larger, and to achieve quietness by reducing noise. Etc. can be suppressed.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention. However, it goes without saying that the present invention is not limited to the following examples.

1. Preparation of NBR rubber The components and blending amounts of the NBR rubber used in the thermoplastic elastomer composition shown in Table 1 are shown below.
-NBR (acrylonitrile butadiene rubber): 50 parts by mass (Nipol 1043, manufactured by Nippon Zeon)
Carboxy NBR (carboxy group-containing acrylonitrile butadiene rubber): 50 parts by mass (Nipol 1072, manufactured by Nippon Zeon)
Carbon black: 5 parts by mass (Seast V, manufactured by Tokai Carbon Co., Ltd.)
・ Zinc flower: 2 parts by mass (manufactured by Karuizawa Refinery)
Deterioration preventing agent: 1.5 parts by mass (NOCRACK 224, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Stearic acid: 1 part by mass (bead stearic acid, manufactured by NOF Corporation)
・ N, N'-M-phenylene dimaleimide: 1 part by mass (DuPont)
・ Vulcanizing agent: 0.5 parts by mass (powder sulfur)

The above blend was mixed for 3 minutes with a rubber Banbury mixer, then released, cooled, and processed into 3 mm diameter pellets with a rubber pelletizer.
A part of the rubber was press molded at 200 ° C. for 5 minutes to prepare a vulcanized rubber sheet. When the viscoelasticity test was done about the obtained vulcanized rubber sheet, it confirmed that the glass transition temperature of vulcanized rubber was -30 degreeC.

2. Preparation of Thermoplastic Elastomer Composition Next, with a formulation (parts by mass) shown in Table 1, a biaxial kneader was charged with a thermoplastic resin and NBR rubber, and about 3 at 200 ° C. and a shear rate of 1000 cm ^−1. After kneading for a minute, the mixture was cooled with water and pelletized with a pelletizer to obtain a thermoplastic elastomer composition.

Details of each component shown in Table 1 are as follows.
Polyamide 12 (low viscosity): Ube nylon 3014U (manufactured by Ube Industries)
Polyamide 11 (low viscosity): Rilsan BMF (manufactured by Atofina)
Polyamide 11 (high viscosity): Rilsan BESN O TL (manufactured by Atofina)
Polyamide 6 (low viscosity): Ube nylon 1011FB (manufactured by Ube Industries)
・ Polyester elastomer: Perprene P150B (manufactured by Toyobo)
-NBR rubber: NBR rubber prepared as described above. For comparison, a polyester elastomer (Perprene P150B) conventionally used as a stopper is used as a conventional example (Comparative Example 1 in Table 1). I picked up.

3. Evaluation of Thermoplastic Elastomer Composition (1) Measurement of Melt Index (MI Value) After heating the sample at 230 ° C. using a melt indexer according to JIS K 7210: 1999, 21.18 N (2.16 kgf) The mass of the molten sample that passed through the orifice for a certain time under load was measured. This was converted to the number of grams per 10 minutes to obtain the melt index. The results are shown in Table 1.

4). Evaluation of Specimen The test specimens of each Example and Comparative Example were each measured for injection moldability, impact resilience, stopper performance, and long-term durability under the following conditions to evaluate each performance. Each evaluation result is shown in Table 1.

(1) Injection moldability The injection moldability was evaluated by actually molding a stopper. First, the thermoplastic elastomer composition shown in Table 1 was introduced into the hopper of the above injection molding machine using an injection molding machine with a mold clamping pressure of 100 t, the cylinder temperature was 220 ° C., and the injection pressure was molded. The mold was filled at 25 MPa. Furthermore, in order to improve the shape transfer accuracy, filling was continued until a sufficient pressure increase in the mold was obtained.

  As the mold, 64 molds were used. The mold was held constant at a mold temperature of 20 ° C. 30 seconds after completion of filling the thermoplastic elastomer composition, the mold was opened, and the test specimen was removed from the mold to obtain a test specimen.

  Evaluation of injection moldability is ○ when all 64 pieces are filled and there is no sink, etc., and all 64 pieces are filled, but △ is given when there are some defects, and 64 pieces are not filled Was marked with x.

(2) Rebound resilience For rebound resilience, in accordance with JIS K 6255: 1996, rebound resilience at temperatures of −20 ° C., 0 ° C., 20 ° C., 60 ° C., and 80 ° C. is used. It was measured. The test body used for the measurement of the impact resilience was a cylindrical product having a thickness of 12.7 mm and a diameter of 30 mm obtained by press-molding a thermoplastic elastomer composition at 220 ° C. In addition, the numerical value of the evaluation result of rebound resilience is shown as rebound resilience in Table 1, and the unit is%.

(3) Stopper performance The stopper performance was measured under the condition of 60 ° C. with the molded stopper mounted on an actual apparatus. In the evaluation of the stopper performance, 80% or more and less than 120% of the current level was evaluated as △, the resilience of less than 80% of the current level was rated as ○, and the resilience of 120% or more of the current level was rated as ×.

(4) Long-term durability The long-term durability was obtained by molding a thermoplastic elastomer composition into a plate shape having a thickness of 2 mm at 220 ° C. and punching it into a dumbbell No. 3 shape. Thereafter, it was immersed in warm water at 95 ° C., and a tensile test was conducted after one year.
In the evaluation of long-term durability, the case where the strength retention rate was 90% or more was evaluated as ◯, the case where the strength retention rate was 50% or more and less than 90% was evaluated as Δ, and the case where the strength retention rate was less than 50% was evaluated as x.

As is apparent from Table 1, all of the molded articles of the examples had a rebound resilience at -20 to 80 ° C. of less than 70%, and good vibration damping and / or vibration isolation at a wide range of temperatures. It shows that it has sex. When the rebound resilience is less than 70%, it can be said that the vibration damping property and / or the vibration proofing property is excellent.
Since the molded body of Comparative Example 1 is formed from a composition that includes a polyester elastomer (glass transition temperature: −70 ° C.) that has been conventionally used as a stopper and does not include rubber, a high temperature (60 ° C., The impact resilience modulus at 80 ° C. exceeds 70%, and the vibration damping properties and / or vibration proofing properties at high temperatures are low.
Comparing Example 3 and Comparative Example 4, Comparative Example 4 with more polyamide 11 and less NBR rubber than Example 3 has a rebound resilience at a low temperature of more than 70%. The rebound resilience of Example 3 is less than 70%. For this reason, the ratio of the thermoplastic resin to the rubber is preferably 85 or less for the thermoplastic resin and 15 or more for the rubber from the viewpoint of impact resilience.

In addition, the thermoplastic elastomer compositions of the examples all have a melt index of 15 g / 10 min or more at a melting temperature of 230 ° C., indicating that they have good fluidity.
When Example 1 and Comparative Example 3 are compared, Comparative Example 3, which contains only 40 parts by mass of the thermoplastic resin, has a low melt index of 13 g / 10 min and poor fluidity during melting. Accordingly, even when the composition of Comparative Example 3 was molded by injection molding, the molded product had molding defects such as sink marks, weld lines, and flow marks, and the injection moldability was poor.
In Comparative Example 5, because the thermoplastic resin used has a high viscosity and low fluidity, even when mixed with rubber to produce a thermoplastic elastomer composition, the melt index of the thermoplastic elastomer composition becomes small, Like Comparative Example 3, the injection moldability was poor.

Claims (8)

A thermoplastic elastomer composition comprising at least one thermoplastic resin and at least one particulate rubber dispersed in the thermoplastic resin,
The ratio of the thermoplastic resin and the rubber is 85/15 to 45/55,
Of the thermoplastic resin and the rubber, the proportion of the rubber having a glass transition temperature of 30 to 80 ° C. is 30% by mass or more and the glass transition temperature of −40 to −10 ° C. Is 15% by mass or more,
A thermoplastic elastomer composition having a melt index of 15 g / 10 min or more when the thermoplastic elastomer composition is softened.   2. The thermoplastic elastomer composition according to claim 1, comprising polyamide 11 and / or polyamide 12 as the thermoplastic resin having a glass transition temperature of 30 to 80 ° C. 3.   The thermoplastic elastomer composition according to claim 1 or 2, wherein at least a part of the rubber is crosslinked.   The molded object which uses the thermoplastic elastomer composition in any one of Claims 1-3.   The molded body according to claim 4, wherein the molded body is molded by injection molding.   The molded article according to claim 4 or 5, wherein the molded article has a rebound resilience at -20 to 80 ° C of less than 70%.   The vibration isolator which consists of a molded object in any one of Claims 4-6.   The anti-vibration material according to claim 7, which is used for a hard disk drive.