JP3354352B2 - Method for producing thermoplastic elastomer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic elastomer. More specifically, it is rich in flexibility, excellent in rubber elasticity over a wide temperature range, high-temperature creep performance, mechanical strength, moldability, and has excellent oil resistance, light discoloration resistance, and excellent toning even though it is a thermoplastic elastomer. The present invention relates to a novel method for producing a thermoplastic elastomer which can be used as a material for various molded products.

[0002]

2. Description of the Related Art In recent years, thermoplastic elastomers which are rubber-like soft materials and which do not require a vulcanization step and have the same moldability as thermoplastic resins have been used in automobile parts, home electric parts, electric wire covering materials, medical materials and the like. Used in the fields of parts, miscellaneous goods, footwear, etc. A typical example of the structure of a thermoplastic elastomer is a type in which hard segments and soft segments are alternately contained in a copolymer chain as disclosed in JP-A-61-34050. . Various grades are manufactured from those having high flexibility to those having rigidity by changing the ratio of each segment. In addition, there are other types of thermoplastic elastomers derived from inexpensive and readily available raw materials. That is, as disclosed in Japanese Patent Publication No. 53-21021 or the like, a thermoplastic blend of a monoolefin copolymer rubber and a polyolefin resin partially crosslinked using an organic peroxide, or a monoolefin copolymer rubber and a polyolefin A composition obtained by melt-kneading a resin with an organic peroxide as a crosslinking aid and partially crosslinking the resin corresponds to this. However, in the former case of a thermoplastic elastomer having a structure in which hard segments and soft segments are alternately contained in a copolymer chain, a large amount of soft segments must be contained in order to obtain a flexible thermoplastic elastomer. Is required. Usually, the soft segment has low tensile strength, and has poor heat resistance, fluidity, and oil resistance. Therefore, a flexible thermoplastic elastomer composition containing a large amount of such a soft segment still has low tensile strength and heat resistance. It has disadvantages such as poor fluidity and oil resistance, and cannot be used for various applications over a wide range. In addition, when a flexible grade is synthesized by a multi-stage synthesis method, it is necessary to synthesize the hard segment and the soft segment separately, so that the polymerization apparatus becomes extremely complicated and the properties and ratio of each segment in the polymerization stage are increased. Is very difficult to control, and defective products may occur when switching grades. Further, it is very difficult to recover the produced polymer because it contains a large amount of rubbery substances.

[0003] In the latter case, a thermoplastic elastomer having a structure in which a monoolefin copolymer rubber in a component is partially crosslinked is insufficient in oil resistance and shape recovery at high temperatures because of partial crosslinking. Therefore, it cannot be used for various applications over a wide range. In addition, since an organic peroxide is used, a polymer chain is cut by a radical caused by the organic peroxide at the same time as the crosslinking, and the mechanical strength is reduced. A means for overcoming this drawback is disclosed in Japanese Patent Publication No. 58-46138. That is, this is a means in which only a crosslink of the monoolefin copolymer rubber is preferentially advanced by using a thermoreactive alkylphenol resin as a crosslinker. The thermoplastic elastomer obtained by this means is completely crosslinked and therefore has sufficient oil resistance and shape recovery properties at high temperatures, but the use of an alkylphenol resin results in extremely poor light discoloration resistance and a high degree of freedom in toning. It cannot be used for applications such as automobile parts, home appliance parts, electric wire coating, etc. Also, a method using an organic organosiloxane compound instead of an alkylphenol resin as a crosslinking agent is disclosed in US Pat.
44 has been proposed. In this method, as in the case of alkylphenol resin crosslinking, only crosslinking of the monoolefin copolymer rubber can be preferentially advanced, and a material excellent in oil resistance, shape recovery at high temperature, light discoloration resistance, etc. can be obtained. Therefore, it can be used for applications such as automobile parts, home appliance parts, and electric wire coating, which require a high degree of freedom in toning. However, this method does not mention a method of kneading a resin composition in which a resin component and a rubber component are kneaded. This difference in the resin composition kneading method greatly affects the mechanical strength, fluidity, moldability, and the like of the obtained thermoplastic elastomer.

[0004]

The present invention has good rubber properties over a wide temperature range, and has good tensile strength, fluidity, moldability, and other characteristics. It is an object of the present invention to provide a production method for easily obtaining a large amount of a thermoplastic elastomer which can be used for a rubber.

[0005]

Means for Solving the Problems After kneading a large amount of the resin composition (the rubber component is not cross-linked) before performing the dynamic crosslinking, kneading with a batch-type kneading machine to facilitate cutting and pelletization, and then a roll sheet The research was developed based on the technical idea of preventing the solidification of the resin composition by cooling until the end of the cutting, and by completely cooling and cutting the roll sheet after the end of the cutting, thereby preventing the occurrence of continuous pellets.
As a result, the present inventors completed various studies and completed the present invention. That is, the present invention relates to (a) an ethylene-α-olefin-non-conjugated diene copolymer rubber (b) a polypropylene resin (c) a hydrosilylation catalyst (d) an organic organosiloxane system having two or more SiH groups in a molecule Crosslinking agent A method for producing a thermoplastic elastomer, characterized in that the above (a) to (d) are melt-kneaded and dynamically vulcanized, and more specifically, an ethylene-α-olefin-non-conjugated diene copolymer. A resin composition consisting of 5 to 300 parts by weight of a polypropylene resin (b) and 0.001 to 5 parts by weight of a hydrosilylation catalyst (c) is kneaded with 100 parts by weight of rubber (a) in a batch kneader, Using a strainer-type extruder using a die having an opening ratio of 10% or more, the resin composition is extruded, cut, and pelletized. Organic organosiloxane crosslinking agent (d) mixing 0.5 to 30 parts by weight with more than a method for producing a thermoplastic elastomer described above obtained by carrying out the dynamic crosslinking using a biaxial kneader.

[0006] The ethylene-α-olefin-non-conjugated diene copolymer rubber (a) used in the present invention is suitably composed of α-olefin having 3 to 15 carbon atoms in its composition.
As the non-conjugated diene, 1,4-hexadiene, ethylidene norbornene, methylene norbornene and the like can be used, and EPDM is preferable. Ethylene of copolymer rubber /
α / olefin ratio is 50/50 to 90/10 by weight,
More preferably, 60/40 to 80/20 is suitable. The Mooney viscosity and ML1 + 4 (100 ° C.) of the rubber used here can be suitably selected from the range of 10 to 120, preferably 40 to 100. If the Mooney viscosity is less than 10, preferred crosslinking cannot be obtained, and improvement of compression set at high temperature cannot be expected, which is not preferred. On the other hand, those exceeding 120 are not preferable because the moldability is remarkably deteriorated and the appearance of the molded product is further deteriorated. The rubber preferably has an iodine value of 5 to 30, particularly preferably 10 to 20.

Next, the type of the polypropylene resin used in the present invention may be a homopolymer or a block or random copolymer of an ethylene-propylene copolymer. The amount of the polypropylene resin (b) is preferably 5 to 300 parts by weight, more preferably 10 to 2 parts by weight, per 100 parts by weight of the rubber component (a).
00 parts by weight. If the amount exceeds 300 parts by weight, the hardness of the obtained elastomeric composition tends to be high and flexibility tends to be lost. If the amount is less than 5 parts by weight, processability tends to be poor. The crosslinking reaction catalyst (c) used in the present invention refers to all catalysts that promote a hydrosilylation reaction. As examples of the catalyst, a noble metal catalyst or a peroxide is often used. The most common catalyst is chloroplatinic acid.

The rubber crosslinking agent (d) used in the present invention is an organic organosiloxane compound having two or more SiH groups. This crosslinking method utilizes a selective addition reaction (hydrosilylation) of SiH groups to unsaturated hydrocarbons in the rubber component. In order to be a cross-linking agent, it is necessary to add to two or more molecules of rubber, so it is necessary to have two or more SiH groups in the molecule. Specific compound examples are cyclic polysiloxanes as shown below,
Compounds having the structure of linear polysiloxanes and tetrahedral siloxanes are typical. Further, a compound and / or a polymer derived from the compound may be used. Here, m is an integer of 3 to 30, n is an integer of 0 to 200, R is a hydrogen alkyl group, an alkoxy group, an aryl group or an aryloxy group, and at least one R bonded to a silicon atom. Is hydrogen and two or more silicon atoms are present in the molecule.

The organoorganosiloxane having the above structure can selectively crosslink rubber. Here, the dynamically crosslinked thermoplastic elastomer composition is obtained by refluxing 1 g of the composition obtained in the present invention for 10 hours with a Soxhlet extractor using boiling xylene,
The residue was filtered through a 80-mesh wire gauze, and the gel content represented by the value obtained by multiplying the ratio of the dry weight of the insoluble matter (g) remaining on the mesh to the weight of the component (a) contained in 1 g of the composition by 100 times was obtained. At least 30%, preferably 50% or more (provided that
(Insoluble components such as inorganic fillers are not included in this), and the crosslinking is performed during melt-kneading of the thermoplastic elastomer composition.
In order to obtain such a dynamically crosslinked thermoplastic elastomer composition, the component (d) is added in an amount of 10 (a).
0.5 to 30 parts by weight, preferably 1 to 0 parts by weight
It can be suitably selected from 20 parts by weight, and its gel content can be adjusted. The catalyst of the component (c) can be arbitrarily added in an amount of 0.001 to 5 parts by weight per 100 parts by weight of the rubber component. here,
If it is less than 0.001, crosslinking does not proceed at a practical rate.
If the amount is more than 5 parts by weight, not only does not have the effect of increasing the amount, but also the deactivated catalyst becomes blackish and becomes poor in appearance, and the heat treatment tends to cause undesirable side reactions (such as decomposition of unreacted SiH groups). is there.

The method for producing the composition of the present invention is basically a mechanical melt-kneading method, but forms a so-called sea-island structure in which the component (a) is scattered in the matrix of the component (b). Kneading must be performed so that the average particle size of the component (a) is 1 μm or less. Average particle size is 1
If it exceeds μm, the crosslinked rubber component of the obtained thermoplastic elastomer not only significantly lowers the fluidity of the resin component, but also significantly lowers mechanical properties such as tensile strength. In performing dynamic crosslinking, two kneading steps are required in which an uncrosslinked rubber component and a resin component are kneaded in advance, and then the rubber component of the kneaded resin composition is dynamically crosslinked. One reason is to use a continuous kneader such as a twin-screw kneader to perform kneading at a high shear rate during dynamic crosslinking, but uncrosslinked EPDM is generally a bale-like mass,
This is because, in this state, it is not possible to charge the continuous mixer. The second is to make the average rubber particle diameter of the component (a) after the completion of the dynamic crosslinking be 1 μm or less. The average rubber particle size at the time of kneading the component (a) and the component (b) is about 20 to 10 μm. The component (a) is crosslinked at the time of the next dynamic crosslinking kneading, the tension at the interface between the component (a) and the component (b) is reduced, and the viscosity of the crosslinked component (a) is increased. ) Increases, resulting in a decrease in the average rubber particle size of component (a).

That is, a resin composition in which the components (a) and (b) are previously kneaded is supplied to a continuous kneader, and the component (a) is crosslinked during kneading. A batch-type kneader is generally used for kneading before performing dynamic crosslinking, and a pressure kneader and a Banbury mixer are particularly preferable. In order to obtain the desired thermoplastic elastomer, a method is used in which the resin composition after kneading is pelletized, and then the pellets are charged into a continuous kneader to crosslink the rubber component during kneading. In order to extrude and cut the mixture kneaded by a batch-type kneader, a method of applying this resin composition to a roll, forming a roll sheet, and then cutting is used. However, since the thermoplastic elastomer obtained in the present invention has PP as a resin component, it is cooled and solidified when a roll sheet is prepared after kneading in a batch kneader, and it is difficult to obtain pellets by this method. Further, when cutting is performed by a hot cut or an underwater cut using a strainer-type extruder, it is difficult to obtain pellets because the resin composition adheres to the cutting blade. In the case of using a strand cut with a strainer type extruder, if the total weight of the resin composition is small,
The residence time can be kept short, but the residence time becomes longer as the total weight increases. Here, if a sheet-shaped resin composition is extruded using a strainer-type extruder using a sheet die having a sheet thickness of 10 mm or less, and cutting is performed with a crusher, the residence time can be significantly reduced. . The sheet shape is a shape extruded from a rectangular, trapezoidal, or arc-shaped discharge die, and the sheet thickness of 10 mm or less means that if the thickness exceeds 10 mm, it is difficult to put the sheet into a pelletizer. That's why.

The paraffinic oil used in the present invention (e)
Has an effect of adjusting the hardness of the obtained composition and giving flexibility, and is added as necessary. In general, a softening agent for mineral oil rubber called process oil or extender oil used for softening, increasing the volume of rubber, and improving processability is a mixture of an aromatic ring, a naphthene ring, and a paraffin ring. Those having 50% or more of the total number of carbon atoms in the paraffin chain are called paraffinic, those having 30 to 45% naphthenic ring carbon are naphthenic, and those having more than 30% aromatic carbon are aromatic. It is said. The oil used in the present invention is preferably a paraffinic oil in the above category, and a naphthenic or aromatic oil is not preferred in terms of dispersibility and solubility. The paraffin rubber softener has a kinematic viscosity at 37.8 ° C. of 20 to 500 cs.
t, pour point is -10 to -15 ° C and flash point is 170 to 3
Indicates 00 ° C. The preferred amount of the paraffinic oil (e) is 30 to 30 parts by weight based on 100 parts by weight of the rubber component (a).
0 parts by weight, more preferably 30 to 250 parts by weight. If the amount exceeds 300 parts by weight, bleed-out of softening is liable to occur, and there is a possibility that tackiness may be caused in a final product, and mechanical strength tends to decrease. Also, 3
If it is less than 0 parts by weight, there is no point in adding.

In addition to the above-mentioned components, the composition of the present invention may further contain an inorganic filler, if necessary, especially for applications where no toning is required. This inorganic filler is
Not only has the benefit of reducing product costs as a bulking agent, but also improves quality (heat-resistant shape retention, flame retardancy, etc.)
There is also an advantage that a positive effect is given to. Examples of the inorganic filler include calcium carbonate, carbon black, talc, magnesium hydroxide, mica, barium sulfate, natural silicic acid, synthetic silicic acid (white carbon), and titanium oxide. Black or the like can be used. Of these inorganic fillers, talc and calcium carbonate are economically advantageous and preferred. Further, if necessary, a nucleating agent, an outer lubricant, an inner lubricant, a hindered amine light stabilizer, a hindered phenol antioxidant, a coloring agent, a silicone oil, and the like may be added. Further, other thermoplastic resins such as a styrene block copolymer (SBC) and a thermoplastic urethane resin can be blended. Since the dynamically crosslinked thermoplastic elastomer obtained by the present invention is thermoplastic, it can be molded using a commonly used thermoplastic resin molding machine, and can be molded by injection molding, extrusion molding, calender molding. Various molding methods such as blow molding and the like are applicable.

[0014]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The components and evaluation methods blended in the following Examples and Comparative Examples are as follows. << Raw Materials >><Componenta> Ethylene-propylene-ethylidene norbornene copolymer rubber EP57P manufactured by Nippon Synthetic Rubber [Propylene content: 28% by weight Muni viscosity ML1 + 4 (100 ° C.): 90]
Iodine value: 15 Tg: -40 ° C] <Component b> polypropylene resin manufactured by Asahi Kasei Corporation, M150
0 [MFR (230 ° C.) = 8.0 g / 10 min Heat deformation temperature: 117 ° C.] <Component c> Chloroplatinic acid hexahydrate manufactured by Yasuda Pharmaceutical Co., Ltd. <Component d> Toray Dow Corning Silicone Co., Ltd. 1,3,5,7-tetramethylcyclotetrasiloxane <Component e> Diana Process Oil PW-3 manufactured by Idemitsu Kosan
80 [paraffinic process oil, kinematic viscosity: 381.
6 cst (40 ° C.), 30.1 (100 ° C.), average molecular weight 746, ring analysis: CA = 0%, CN = 27%, CP =
73%]

<< Evaluation Method >> (1) Hardness JIS K6301 A type (2) Tensile strength TS [MPa] and tensile elongation at break Eb
[%] JIS K6301 No. 3 dumbbell (3) Melt viscosity [poise] Measured with a capillograph (manufactured by Toyo Seiki Seisaku-sho, Ltd.) 230 ° C. 40 × 1 mm die used Extrusion speed 500
mm / min (4) Melt flow rate [dg / min] JIS K6758 230 ° C × 2.16 kg (5) Compression set [%] JIS K6301 70 ° C × 22 hr 25% compression (6) Extrusion appearance test 20 mmφ manufactured by Engineering Plastics Industry Using a single screw extruder, L / D =
20 screws, 25 × 0.5mm tape die,
C / R = 3.0, temperature condition C1: 190 ° C., C2: 200 ° C., H: 210
° C, D: 220 ° C, rotation speed 90 rpm. At 25 × 150m
m, and the surface is visually observed.
If one or more spots of 0 μm or more were observed,
(7) Pelletization time (min) Time from input of strainer type extruder to completion of pelletization

<< Examples 1 to 4 >> Of the compounding recipes shown in Table 1, all the components except component (d) were put into a pressure kneader at a time and kneaded at a kneading temperature of 190 ° C. for 10 minutes. Was. Thereafter, for Examples 1 to 4, the kneaded resin composition was put into a strainer-type extruder of a sheet die having a die diameter of 200 mm and a discharge port of 10 × 320 mm, and extruded at a cylinder temperature of 120 ° C., respectively. The resin composition extruded into a shape is cut by a pulverizer, and the obtained pellet-shaped resin composition is put into a twin-screw kneader, and the component (d) is liquid-added while kneading, whereby dynamic crosslinking is performed. Was carried out to obtain an intended thermoplastic elastomer. The total weight of the resin composition charged into the pressure kneader was adjusted to 10 kg. Table 2 shows the results.

<< Comparative Examples 1-4 >> Comparative Example 1 differs from Example 1 in that
Comparative Example 2 is Example 2 and Comparative Example 3 is Example 3 and Comparative Example 4.
Examined the same formulation as in Example 4. For Comparative Examples 1 to 4, the kneaded resin composition (total weight 10 kg) was put into a strainer-type extruder having a die diameter of 200 mm, a strand diameter of 4.0 mm, and an 8-hole die, and the same extrusion conditions as in Examples 1 to 4 were used. To obtain a pellet-shaped resin composition by strand cutting. Table 3 shows the results.

<< Comparative Examples 5 to 8 >> Comparative Example 5 differs from Example 1 in that
Comparative Example 6 is Example 2 and Comparative Example 7 is Example 3 and Comparative Example 8.
Examined the same formulation as in Example 4. For Comparative Examples 4 to 8, the kneaded resin composition (total weight 10 kg) was put into a strainer-type extruder having a die diameter of 200 mm, a strand diameter of 25 mm, and an 8-hole die, under the same extrusion conditions as in Examples 1 to 4. The resin composition was obtained by extrusion and strand cutting. In the time from the introduction of the strainer type extruder to the end of pelletization, the strand diameter was too large to be introduced into the pelletizer and the crusher, and the evaluation was stopped.

<< Comparative Examples 9 to 12 >> Comparative Example 9 differs from Example 1 in that
Comparative Example 10 is Example 2 and Comparative Example 11 is Example 3 and Comparative Example 12.
Examined the same formulation as in Example 4. In Comparative Examples 9 to 12, the resin composition (total weight 10 kg) after kneading with a pressure kneader was applied to a roll, a roll sheet was cut out, and the roll sheet was pulverized to obtain a pellet-shaped resin composition. During the time from the introduction of the strainer-type extruder to the end of pelletization, roll sheet cutting could not be performed due to roll sheet cooling and solidification, and the evaluation was stopped.

<< Comparative Examples 13 to 16 >> Comparative Example 13 differs from Example 1 in that
Comparative Example 14 is Example 2 and Comparative Example 15 is Example 3 and Comparative Example 16.
Examined the same formulation as in Example 4. Comparative Examples 13 to 16 were put into a strainer-type extruder having a die diameter of 200 mm, a strand diameter of 5 mm, and a 72-hole die, extruded under the same conditions as in Examples 1 to 4, and obtained a pellet-shaped resin composition by hot cutting. The thus obtained pellet-shaped resin composition was kneaded using the same biaxial kneader as in Examples 1 to 4 under the same kneading conditions as in Examples 1 to 4, and the component (c) was added by liquid addition. Then, dynamic crosslinking was performed to obtain a desired thermoplastic elastomer. During the time from the introduction of the strainer type extruder to the end of pelletization, continuous pellets were generated due to the adhesion of the pellets to the cutting blade, and the evaluation was stopped because the pellets could not be introduced into the twin screw extruder.

[0021]

Table 2 Example 1 2 3 4 Pelletizing time (min) 2 2 2.7 2 Properties Hardness 81 88 78 89 TS (MPa) 20 19 15 14 Eb (%) 630 600 630 510 Melt viscosity 250 200 260 210 MFR (dg / min) 1.0 3.0 1.1 3.1 CS (%) 37 39 29 44 Extrusion appearance test ○ ○ ○ ○

Table 3 Comparative Example 1 2 3 4 Pelletization time (min) 20 22 27 21 Property hardness 81 88 78 89 TS (MPa) 19 18 15 15 Eb (%) 620 590 630 510 Melt viscosity 260 210 260 210 MFR (dg / min) 0.9 0.9 1.0 3.0 CS (%) 37 40 29 45 Extrusion appearance test ○ ○ ○ ○

[0024]

According to the production method of the present invention, flexibility, mechanical strength, flow characteristics and moldability are excellent, and excellent rubber elasticity is exhibited over a wide temperature range, and rubber elasticity, mechanical strength, molding speed, molding yield, etc. It has become possible to easily knead a large amount of thermoplastic elastomers that can be suitably molded and used for automobile parts, home electric parts, various electric wire coatings (insulation, sheath) and various industrial parts for which improvement is desired.

Claims (2)

(57) [Claims] 1 to 100 parts by weight of an ethylene-α-olefin-non-conjugated diene copolymer rubber (a), 5 to 300 parts by weight of a polypropylene resin (b), and 0.001 to 5 parts by weight of a hydrosilylation catalyst (c). after kneading the parts or Ranaru resin composition in a batch type kneader, then extruded at using strainer extruder having a thickness using the following sheet die 10mm sheet, after water cooling, pelletizer - at Katteingu Then, the pelletized resin composition is further mixed with 0.5 to 30 parts by weight of an organoorganosiloxane-based crosslinker (d) having two or more SiH groups in the molecule, and then mixed with a continuous kneader. A method for producing a thermoplastic elastomer, comprising performing dynamic crosslinking. 2. An ethylene-α-olefin-non-conjugated diene copolymer rubber (a) in an amount of 30 to 300 parts by weight per 100 parts by weight.
2. The method for producing a thermoplastic elastomer according to claim 1, comprising paraffin-based oil (e) in parts by weight.