JPH05117489A - Polymer composition for injection-molded product - Google Patents

Abstract

PURPOSE:To provide a polymer compsn. useful for molding an injection-molded product excellent in the balance between dimensional stability (linear expansion coefficient) and impact resistance at low temp. CONSTITUTION:The title compsn. comprises 40-70wt.% polyamide resin (A) having an MFR of 0.1 to 100dg/min and 30-60wt.% maleic anhydride-modified ethylene-propylene copolymer rubber (B) having an MFR of 0.1 to 50dg/min, a propylene monomer unit content of 20 to 40wt.% and a maleic anhydride graft monomer unit content of 0.1 to 10wt.%, and has an MFR ratio of the component A to the component B of 0.01 to 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer composition useful for producing an injection-molded article having an excellent balance between dimensional stability (low linear expansion coefficient) and low temperature impact resistance.

[0002]

2. Description of the Related Art In recent years, automobiles have been rapidly made of plastics for the purpose of improving fuel efficiency by reducing weight, and instrumental panels, console boxes,
Interior parts such as glove box, handle, trim,
Various plastic materials have come to be used not only for exterior parts such as moldings, lamp housings, front grilles, mudguards, and side bumpers, but also for bumpers, fascias, bodies (partial parts), etc., which were conventionally metal. Examples of plastics used for such automobile parts include polymer alloy materials such as RIM / urethane, composite polypropylene, and polycarbonate / ABS. In particular, the materials used for bumpers and fascias are currently inferior to the type that uses a low-rigidity material that has the property of absorbing and mainly recovering the energy at the time of collision, and then recovering, It is divided into two types: a type that uses a lightweight, low-priced, high-rigidity material.

Of these materials, the former is mainly RIM.
Urethane, polypropylene with partially cross-linked ethylene / propylene copolymer rubber (EPR) and the like are used, and the flexural modulus is about 2000 to 5000 kg / cm ² . The latter is made of polypropylene containing EPR / inorganic filler and has an elastic modulus of 8000 to 12000.
It shows about kg / cm ² . Recently, these materials have been widely used particularly because of their high cost and high productivity of versatile injection molding.

Among these materials, the low-rigidity type material relates to, for example, a polypropylene composition in which partially crosslinked ethylene / propylene copolymer rubber and oil are mixed with polypropylene. Sho 53
-145857, 54-16554 and 57-13584
By the method described in Japanese Patent No. 7 or the like, or
The relatively low-rigidity type relates to a polypropylene-based composition in which a non-crosslinked ethylene / propylene copolymer rubber and high-density polyethylene are blended, and is manufactured by a method described in JP-A-56-106948. There is.
Further, the high rigidity type material relates to, for example, a polypropylene-based composition in which a non-crosslinked ethylene / propylene copolymer rubber and oil are blended.
No. 52-12650 and No. 63-146951, and the like.

[0005]

However, the low-rigidity type material produced by the method described in the above publication cannot be coated in an injection-molded article without surface modification such as plasma treatment. Also, they did not always have a good quality balance. Moreover, in recent car design, especially in terms of obtaining the flatness of the whole body and the finished finish close to sheet metal, the coefficient of linear expansion is large at around 15 × 10 ^-5 / ° C. When used in a high temperature environment, because the degree of thermal expansion of the paint and the plastic of the base material is different, peeling of the coating film and fine cracks on the coated surface occur, and the film clarity is not good, I couldn't get anything satisfactory.

Furthermore, when a large plastic molded product is used in combination with another material, for example, a metal or wood molded product, the degree of thermal expansion differs under a high-temperature use environment, resulting in problems such as dimensional difference and poor meshing. Has occurred. In addition, the high-rigidity type material manufactured by the method described in the above-mentioned publication had a good quality balance in the injection-molded body, but when it was coated like the low-rigidity type material. Since the surface modification of the molded product of No. 1 is necessary and the coating film clarity and the coefficient of linear expansion are not satisfactory, a satisfactory product could not be obtained.

On the other hand, as a technique for producing a material having a low linear expansion, a method of filling a plate-like or fibrous filler in a resin is generally used. However, in order to obtain a material with a good low linear expansion, it is necessary to add a large amount of filler, which deteriorates the flowability and deteriorates the appearance of moldability (including film clarity). Also, the low temperature impact resistance was not good.

[0008]

Means for Solving the Problems As a result of intensive studies to solve these problems, the present inventors have found that a specific maleic anhydride-modified ethylene
A polymerization composition in which a propylene copolymer rubber is blended in a specific ratio remarkably improves the dimensional stability (low linear expansion coefficient) of a molded article, which is the above-mentioned problem, and at the same time, low-temperature impact resistance,
In order to produce an injection-molded article having a good performance balance, the inventors have found that it is a preferable molding material, and have completed the present invention.

That is, the polymer composition according to the present invention comprises a component A: 40 to 70% by weight of a polyamide resin having a melt flow rate of 0.1 to 100 dg / min, and a component B: a melt flow rate of 0.1 to 50 dg / min. And 30 to 60% by weight of a maleic anhydride-modified ethylene / propylene copolymer rubber having a propylene content of 20 to 40% by weight and a maleic anhydride graft amount of 0.1 to 10% by weight, and the melt flow rate of component A (MFR _A ) to the melt flow rate of component B (MFR _B ) (MF
R _A / MFR _B ) is 0.01 to 50.

[I] Polymer composition <Component A> The component A constituting the polymerization composition of the present invention has a melt flow rate of 0.1 to 100 dg / min, preferably 0.3 to 80 dg / min. , And more preferably 1.
It is a polyamide resin of 0 to 70 dg / min. The melt flow rate (MF) of the polyamide resin in the present invention is
R) has a water content of 3 according to ASTM D1238.
The resin of 00-900 ppm at a temperature of 280 ° C.
Measured under a load of 6 kg. When the amount of water contained in the polyamide is large, the polyamide easily hydrolyzes at the time of MFR measurement to change the MFR. Therefore, the amount of water contained in the polyamide must be suppressed to 300 to 900 ppm. If the MFR of less than the above range is used, the moldability is difficult, and if the MFR of more than the above range is used, the low temperature impact resistance is lowered.

The polyamide resin has --C in its polymer main chain.
It has an O-NH- bond and can be heated and melted. Typical examples thereof are nylon-4 and nylon-
6, nylon-6,6, nylon-4,6, nylon-
12, nylon-6,10, and the like. In addition, low crystalline or amorphous polyamide containing a monomer component such as a known aromatic diamine, aromatic dicarboxylic acid, or transparent nylon can also be used. Preferred polyamides are nylon-6,6, nylon-6, or amorphous polyamides, with nylon-6,6 and nylon-6 being particularly preferred.

<Component B> Component B which constitutes the polymer composition of the present invention is a maleic anhydride-modified ethylene / propylene copolymer rubber having a melt flow rate of 0.1 to 50 dg / min. Propylene content is 20-4
0% by weight and a maleic anhydride graft amount of 0.1 to 10% by weight. Melt flow rate of component B (MF
R) is 0.1 to 50 dg / min, preferably 1 to 30 d
g / min. The MFR of component B is ASTM-D
According to 1238, at a temperature of 230 ° C, 2.16 kg
Measured under load. When the MFR of less than the above range is used, not only the linear expansion coefficient of the obtained molded product becomes high but also the moldability is deteriorated (especially, the appearance of the obtained molded product is deteriorated, for example, generation of flow marks, etc.). ) And then MF
When R exceeding the above range is used, the low temperature impact strength is lowered.

The propylene content of component B is 20-40% by weight, preferably 22-30% by weight. When the propylene content is less than the above range, the elastic modulus of the obtained injection-molded article becomes too high. If the propylene content exceeds the above range, the appearance of the molded product and the releasability during molding deteriorate. The graft amount of maleic anhydride in the component B is 0.1 to 10% by weight, preferably 0.2 to 8% by weight, particularly preferably 0.4 to 3% by weight. If the graft amount of maleic anhydride is less than 0.1% by weight, the low temperature impact strength will be insufficient, and if it exceeds 10% by weight, the molding appearance will be deteriorated.

The ethylene / propylene copolymer type rubber as the base polymer constituting the component B is a copolymer consisting of ethylene and propylene, and if necessary, these and other comonomers, especially non-conjugated diene, It also includes a copolymer with. As a preferable example of the ethylene / propylene copolymer rubber, an amorphous random copolymer mainly composed of ethylene and propylene, particularly a non-conjugated diene is copolymerized. As the non-conjugated diene in this case, dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylnobornene, 5-ethylidene-2-norbornene and the like are used. These ethylene / propylene copolymer rubbers are typically produced by polymerization using a vanadium-based catalyst composed of a vanadium compound such as vanadium chloride or vanadium oxychloride and an organoaluminum compound such as triethylaluminum sesquichloride. Target. The copolymer rubber produced by such a catalyst system generally has good randomness.

<Other Components> The polymer composition of the present invention contains the components A and B described above.
The term "contains" as used herein means that auxiliary components may be contained in addition to the listed components A and B, as long as the gist of the present invention is not impaired. The polymer composition of the present invention is
In addition to the components A and B, various additives such as pigments, stabilizers, antioxidants, ultraviolet absorbers, and foaming agents that are generally blended in ordinary resin materials can be added depending on the purpose.

Further, the composition is a polyphenylene ether resin (P) within a range that does not significantly impair the effects of the present invention.
PE), polycarbonate resin (PC), polyester resin (PE _S ), ethylene polymer (high pressure polyethylene: LDPE, low pressure low density polyethylene: LLP)
E, low-pressure polyethylene: HDPE, ethylene / vinyl acetate copolymer: EVA, ethylene-acrylic acid ester copolymer: EEA, ethylene-acrylic acid copolymer: EAA, etc.), and other resins such as polyamide and polybutene can be blended. In addition, mineral oil-based softeners called process oils or extender oils, which are commonly used as rubber softeners, and inorganic fillers such as calcium carbonate, carbon black, talc, clay whiskers, and glass fibers are also required. It can be added accordingly.

<Blending Ratio> The polymer composition of the present invention comprises the above-mentioned component A (polyamide resin) and component B (maleic anhydride-modified ethylene / propylene copolymer rubber) and, if necessary, other components. It is prepared by blending. The mixing ratio of the component A is 40 to 70% by weight, preferably 40 to 65% by weight, and more preferably 45 to 60% by weight, based on the total amount of the components A and B. The blending ratio of component B is based on the total amount of component A and component B,
It is 30 to 60% by weight, preferably 30 to 55% by weight, and more preferably 35 to 50% by weight. When the blending ratio of the component A is less than the above range (when the blending ratio of the component B exceeds the above range), the appearance of the obtained injection-molded article and the releasability at the time of molding are deteriorated, and the above range is not satisfied. When it exceeds (when the blending ratio of the component B is less than the above range), the linear expansion coefficient and the low temperature impact resistance deteriorate.

<MFR Ratio of Component A and Component B> Component A and Component B must have the above-mentioned specific melt flow rates, and the ratio of both, that is, the melt flow rate of Component A ( MFR _A ) / Component B melt flow rate (MFR _B ) is 0.01 to 5
It is important that it is 0, preferably 0.05-40. When the melt flow rate ratio is less than the above range,
Releasability at the time of molding and the appearance of the molded product deteriorate. If the melt flow rate ratio exceeds the above range, the low temperature impact strength of the obtained injection-molded product may decrease, or the linear expansion coefficient may increase.

[II] Injection Molded Article The production of an injection molded article using the polymer composition of the present invention will be described below. <Molding> The above-mentioned components A and B (and other components as required) are mixed within the above-mentioned mixing ratio in a Banbury mixer, a tumbler type mixer, a Henschel type mixer, a kneader, a single-screw extruder, An injection-molded article is obtained by blending with an ordinary kneading machine such as a twin-screw extruder and then performing injection molding by a conventional method.

<Physical Properties of Molded Product> The injection molded product molded from the polymer composition of the present invention has a linear expansion coefficient in accordance with ASTM-D696, particularly a linear expansion coefficient in the resin flow direction of 1.
It can be 0 × 10 ⁻⁵ / ° C. or less, preferably 8 × 10 ⁻⁵ / ° C. or less. If this value is exceeded, the dimensions of the injection-molded article will change greatly in the operating temperature range of, for example, -40 ° C to 80 ° C, and therefore inconvenience will occur when it is assembled as an automobile exterior part, for example. It should be understood that these physical properties are, by definition, those of an injection-molded article consisting of only component A and component B. However, when the amount of the above-mentioned “other components” is small, it can be considered as the value when such a component is contained.

The injection-molded article molded from the polymer composition of the present invention has a thickness direction of 300 μm to about 1 m from the surface.
A skin layer (rubber orientation layer) is formed with a thickness of about m, whereby a molded product having a good low linear expansion coefficient can be obtained. The surface of such a skin layer has not been clarified yet, but when the above polymer composition is vigorously injected into a molding die by injection molding, the flow of the skin layer flows while being cooled by the wall surface of the cooled die. As a result, it is considered that the ethylene / propylene copolymer rubber contained in the composition was stretched in the flow direction to form a vertically long sea / island structure.

The linear expansion coefficient of the sea / island structure injection molded article is small because the stretched rubber component of the sea / island structure is contracted by heat, which causes It is considered that the coefficient of thermal expansion of the polyamide resin is subtracted, and the coefficient of linear expansion of the entire injection-molded article is reduced. However, these skin layers cannot withstand the linear expansion coefficient of the entire injection-molded article if the injection-molded article itself is too thick, so that the thickness of the injection-molded article is indispensable.

<Uses> Since the injection-molded product molded from the polymer composition of the present invention has the above-mentioned characteristics, for example, bumpers, facias, fenders, air dams, air spoilers, moldings, front grilles. ,
It is extremely useful as a vehicle exterior member such as a mudguard.

[0024]

EXAMPLES The following examples and comparative examples serve to explain the present invention more specifically. Examples 1 to 5 and Comparative Examples 1 to 3 Constituents of Polymer Compositions : Component A and Component B used in Examples and Comparative Examples are shown in Tables 1 and 2. Component B is ethylene / propylene copolymer rubber (EPR) and maleic anhydride using a twin-screw kneading extruder at a set temperature of 230 ° C. and a screw rotation speed of 250 r.
It is melt-kneaded at pm and graft-modified (M-
EPR).

[0025]

[Table 1]

[0026]

[Table 2]

Blending and melt-kneading : The polyamide resin of component A shown in Table 1 above and the maleic anhydride-modified ethylene / propylene copolymer rubber of component B shown in Table 2 were prepared.
The mixture was blended in the proportions shown in Table 3 below and sufficiently mixed and stirred with a Henschel type super mixer to prepare a mixture, and this mixture was mixed with a TEX twin-screw extruder (L / D = 30) (manufactured by Japan Steel Works). Melt-kneading at a preset temperature of 250 ° C. and a screw rotation speed of 250 rpm, and extruding into a strand shape,
It was made into pellets with a cutter. This was dried at 95 ° C. for 8 hours with a hot air dryer. Molding and Evaluation : (Injection molding) From the pellets of the above polymer composition, an in-line screw injection molding machine (IS manufactured by Toshiba Machine Co., Ltd.)
(-90B type), injection molding was performed at a cylinder temperature of 280 ° C. and a mold cooling temperature of 70 ° C. to prepare a test piece. (Press molding) Using the pellets of the above polymer composition, press molding was performed at 280 ° C to prepare a press molding test piece for evaluation. Before molding, a vacuum dryer was used immediately before the molding under the conditions of 0.1 mmHg and 80 ° C.
It was dried for an hour. Further, the molded test piece was put into a desiccator immediately after molding, allowed to stand at 23 ° C. for 4 days to 6 days, and then an evaluation test was conducted. The results are shown in Table 3.

The physical properties and various characteristics were measured by the following methods. (1) Flexural modulus ISO R178-1974 procedure 12 (JIS
According to K7230), it measured using the Instron tester. The measurement temperature was 23 ° C. (2) Izod impact strength ISO R180-1969 (JIS K7110)
(Izod impact strength with notch) was measured using an Izod impact tester manufactured by Toyo Seiki Seisakusho. The measurement atmosphere temperature was −30 ° C. (3) High-speed impact test A test piece (120 m) installed on a support (hole diameter: 2 inches)
m × 80 mm, thickness 2 mm), a dart (diameter 5/8 inch), which is a load sensor, is collided at a speed of 1 lm / sec to measure the deformation and fracture behavior of the test piece under an impact load,
The impact energy absorbed up to the crack initiation point in the obtained impact pattern was calculated as the impact strength of the material. The measurement atmosphere temperature was −30 ° C. (4) Linear Expansion Coefficient The linear expansion coefficient was measured according to ASTM-D696 using the 4 mm injection-molded sheet prepared under the above-mentioned molding conditions. However, the measurement temperature range is 23 to 80 ° C.

[0029]

[Table 3]

Front Page Continuation (72) Inventor Shigekazu Oi 1 Toho-cho, Yokkaichi-shi, Mie Prefecture Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (1)

[Claims] 1. Component A: Melt flow rate 0.1 to 10
40-70% by weight of polyamide resin at 0 dg / min, and Component B: anhydrous with a melt flow rate of 0.1-50 dg / min, a propylene content of 20-40% by weight, and a maleic anhydride graft amount of 0.1-10% by weight. It contains 30 to 60% by weight of a maleic acid-modified ethylene / propylene copolymer rubber and has a ratio (MF) of the melt flow rate (MFR _A ) of the component _A and the melt flow rate (MFR _B ) of the component B.
Injection molded body polymer composition R _A / MFR _B) is characterized in that 0.01 to 50.