JPS6248749A - Olefinic thermoplastic elastomer - Google Patents

Abstract

PURPOSE:The titled composition suitable for exterior automotive trims such as side lace, etc., having improved matting effects on molded article, appearance, fluidity and moldability, obtained by blending PP with a specific flow rate with specific amounts of specific EPDM an EVA. CONSTITUTION:(A) 35-60wt% crystalline polypropylene having 5-80g/10min. melt flow rate is blended with (B) 20-50wt% oil-extended ethylene propylene diene terpolymer having 10-100phr oil extension amount and 30-100 Mooney viscosity ML1+8(120 deg.C) and (C) 5-30wt% ethylene vinyl acetate copolymer having 5-40wt% vinyl acetate content and 50-400g/10min. melt flow rate.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an olefinic thermoplastic elastomer (hereinafter referred to as "
Regarding "TPO"), it is particularly suitable as an injection material for automotive exterior parts such as side moldings, bumpers, and mudguards.

<Prior Art> Since TPO has features such as low specific gravity, good cold resistance, and excellent weather resistance, its application as a material for the above-mentioned automobile exterior parts is being promoted. The recent trend is that automotive exterior parts are required to have a matte appearance, but when attempting to obtain matte exterior automotive parts by injection molding using TPO, Due to the influence of the rubber component (EPDM), flow (or swirl) marks and the like were generated on the molded product, making it difficult to obtain a good or uniform appearance.

Therefore, if we use TPO in which the rubber component is partially crosslinked (JP-A-47-18943, JP-A-48-28838, JP-A-5
No. 3-145857, No. 52-142753, No. 54
-1386, etc.), the above-mentioned problems can be solved to some extent, and the difficulty in obtaining an injection molded product with a good matte appearance is reduced.

However, since the preparation of injection materials made of TPO involves a partial crosslinking process, it is difficult to control and it is difficult to obtain TPO of stable quality.As a result, injection materials made of TPO end up being expensive. became.

Therefore, the inventors of the present invention have developed a method using T that does not require partial cross-linking of the rubber component, which can produce an injection molded product with a good matte appearance.
As a result of our dedicated efforts to develop PO, we have achieved a specific Mooney viscosity,
EPDM30 defined by propylene content and third component
~70 wt%, specified vinyl acetate content, Mn specified EVAIO ~30 wt%, and specified Mn. We have developed TPO, a polyblend consisting of 20 to 50 wt% P P (Japanese Patent Application No. 60-93226;
Unpublished).

<Problem to be solved by the invention> However, the above TPO is an EP with relatively high Mooney viscosity.
Since it is essential to use DM and the fluidity of the polyblend is not good, there is a problem in that the plasticizing temperature and injection pressure must be increased during injection molding. Increasing the plasticizing temperature or injection pressure is undesirable because it adversely affects moldability (productivity).

<Object of the Invention> In view of the above, the present invention makes it possible to obtain a molded product with a good matte appearance without the complicated manufacturing process of partial crosslinking, and in addition, the polyblend itself has good fluidity. The purpose of the present invention is to provide a TPO that has excellent moldability.

Means for Solving the Problems> The TPO of the present invention has a specific melt flow rate (hereinafter r
MFRJ: PP 35-60wt% defined by melt index at 230°C, oil-extended EPDM 20-50wt defined by specific oil extension amount and Mooney viscosity
%, specific vinyl acetate content and MFR
The above object is achieved by creating a polyblend containing VA of 5 to 40 wt%.

(1) Examples of the PP used above include propylene homopolymers or copolymers of propylene and α-olefins such as ethylene, butene-1, and pentene-1; A copolymer of is preferred. This PP has an MFR of 5 to 80 g/l.
o minutes (preferably lO to 50 g/JO minutes). If the MFR is less than 5 g/10 minutes, the fluidity of the polyblend is not good (see MFR in Comparative Example 4), and appearance defects such as flow marks are likely to occur.
If it exceeds g/10 minutes, it will be difficult to obtain a molded product with a strength for regular use (for exterior parts of automobiles, etc.) and a matte appearance.

(2) The oil-extended EPDM used above has an oil-extended amount of 10 to
100 phr (preferably 4O-100 phr), and Mooney viscosity ML, rod (120°C) 30-10
It is defined as 0.

If the amount of oil extended is less than 10 phr, the mold releasability of the molded product will decrease, and if it exceeds 100 phr, there is a risk that bleeding will occur in the molded product after the mold is released. Note that paraffin-based or naphthene-based oils are used for oil extension.

If the above Mooney viscosity is less than ML t+ (120°C) 30, it is difficult to obtain a sufficiently matte state on the surface of the molded product (it tends to become glossy), and if it exceeds 100, blending with PP becomes difficult and molding becomes difficult. It is difficult to obtain regular strength from the product.

6 (3) The EVA used above has a vinyl acetate content of 5 to 30 wt.
%, MFR is defined as 50 to 400 g/10 minutes.

Here, if vinyl acetate is less than 5 wt%, flow marks are likely to occur in the molded product, and if it exceeds 30 wt%, blending with PP and oil-extended EPDM becomes difficult, making it difficult to obtain regular strength in the molded product. In addition, the higher the MFR of EVA, the more desirable it is from the viewpoint of fluidity of the polyblend.
/10 minutes or less, the fluidity of the polyblend is not good (see MFR of Comparative Example 7).

(4) PP, oil-extended EPDM, EVA (7) The blend ratios are as described above.

If the PP content is less than 35 wt%, it is difficult to obtain a molded product with regular strength and it is difficult to obtain a uniform matte appearance (see Comparative Example 2), and if it exceeds 60 wt%, the hardness of the molded product is low. This makes it difficult to impart elastomer properties to molded products.

If oil-extended EPDM is less than 20 wt%, the amount of PP will increase relatively, and as mentioned above, it will be difficult to impart elastomeric properties to the molded product, and if it exceeds 50 wt%, it will be difficult to obtain regular strength and the fluidity will be poor. (See MFR of Comparative Example 3).

When the EVA content is less than 5 wt%, it is difficult to obtain a uniform matte appearance in the molded product (see Comparative Example 3), and when it exceeds 40 wt%, it is difficult to obtain the regular strength and the wax remover resistance is poor.

(5) TPO, which is the polyblend, contains auxiliary materials that are added to general thermoplastic resins, such as heat stabilizers, anti-aging agents, ultraviolet absorbers, lubricants, processing aids, pigments, fillers, etc. They may be blended as appropriate.

The production of TPO is usually carried out using a closed temperature kneader such as a Banbury mixer 1 pressurized kneader. ! This will be carried out using one machine. In some cases, a part of PP or a part of EVA and oil-extended EPDM are melt-mixed in advance in the above-mentioned closed kneader, and square pellets are obtained from the separated sheet with a sheet pelletizer,
The square pellets and the remaining PP and EVA pellets may be tampled and then blended and pelletized using a -screw or twin-screw extruder for production.

<Effects of the Invention> The TPO of the present invention makes it possible to obtain injection molded products with a good (uniform) matte appearance, as shown in the Examples below, even without including a partial crosslinking process during the preparation of the injection material. can. That is, since a partial crosslinking process is not included in the preparation of the injection material, rough control of temperature and pressure conditions and a simple crosslinking mechanism are required, and material costs can be significantly reduced.

In addition, it has good fluidity, so there is no need to increase the plasticizing temperature or injection pressure during injection molding, and moldability (productivity) also improves.

<Examples> Hereinafter, the present invention will be explained in more detail based on Examples.

EPDM, EVA and PP used in each example/comparative example
The characteristics of each are shown in Tables 1 and 2Φ3.

The polyblend combined according to the recipe shown in Table 4 was put into a BR type Banbury mixer heated with steam, and kneading was continued until the resin temperature rose to 200°C.
After dispensing with a 0-inch roll, a pelletized injection material was prepared using a sheet pelletizer.

Using each injection material thus obtained, the injection temperature was 220°C.
, injection pressure 800 kgf/c, injection time 10 seconds,
100X200X5II11 depending on the mold temperature (30℃)
A molded product was obtained. Then, the following test measurements were performed on each of the molded products. The results are shown in Table 4.
It can be seen that all of the molded products made of PO exhibit a good matte appearance, have sufficient wax removal resistance at a practical level, and have good fluidity.

(1) Gloss condition: Measured with a 60@φ60@in-reflection gloss meter (GM-3M, new product of Murakami Color Technology Research), reflectance of 10% or less is "matte", and reflectance of 50% or more is "glossy". ”.

(2) Appearance uniformity: visual comparison with uniform matte coating, approximately equivalent to "O", and noticeable flow marks etc. to "X".

(3) Wax remover resistance...JISK6301 (
The swelling ratio (volume change rate) before and after immersion in kerosene (80°C) for 10 minutes was rated "○" if it was less than 50%, and if it was 50% or more, it was rated "X".

(4) MFR: Measured according to ASTM-D1238.

Claims (1)

[Claims] Crystalline polypropylene (hereinafter referred to as "PP") 35-60wt
%, oil-extended ethylene-propylene-diene terpolymer (
(hereinafter referred to as "oil-extended EPDM") 20 to 50 wt%, ethylene.
Vinyl acetate copolymer (hereinafter referred to as "EVA") 5-40wt
%, and the PP has a melt flow rate of 5 to 80 g/10 min, and the oil-extended EPDM has an oil extension amount of 10 to 100 phr.
, Mooney viscosity is ML_1_+_8 (120℃) 30~
100 is used, and the vinyl acetate content is 5 to 30 wt% as the EVA.
, an olefin thermoplastic elastomer having a melt flow rate of 50 to 400 g/10 min.