JPS63186754A - Composite polypropylene composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which scarcely forms voids and is suited for the production of large moldings such as bumpers excellent in appearance, impact resistance and paintability, by adding a specified random copolymer to a crystalline ethylene/propylene block copolymer. CONSTITUTION:A composite polypropylene composition is prepared by adding an amorphous propylene/alpha-olefin random copolymer (B) to a crystalline ethylene/ propylene block copolymer (A). Although an amorphous ethylene/propylene random copolymer has been added to block copolymer A in order to improve impact resistance at low temperature in the preparation of a conventional composition of this kind, there is a difficulty that voids are liable to be formed when simultaneous improvement of size increase, paintability and impact resistance is intended. By replacing part or the whole of the added ethylene/propylene random copolymer by random copolymer B, a large molding such as a bumper of a good appearance can be produced without forming voids.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a composite polypropylene composition suitable for producing large molded articles such as bumpers having excellent appearance, impact resistance, and paintability. , relates to a composite polypropylene composition for large molded bodies with improved dimensional stability.

(Prior Art) Recently, polypropylene compositions have been attracting attention as materials for large molded bodies, such as automobile bumpers, as described in JP-A-57-159841. In order to increase Generally used.

Here, the block copolymer is obtained by adding and reacting propylene gas at the same time or sequentially with about 3 to 15% by weight of ethylene gas during polymerization of propylene, and the block copolymer has about 94 to 70% by weight of ethylene gas.
It consists of a polypropylene (hereinafter abbreviated as PP) component of about 6% to 30% by weight of a random copolymer component and some polyethylene component. On the other hand, EP silane copolymer refers to a random copolymer of ethylene and propylene having an ethylene content of 50% by weight or more.

The random copolymer component produced in the block copolymer has an ethylene content of 30 to 70% by weight, and it is not certain whether ethylene or propylene is predominant. The EP silane copolymer added above has an ethylene content of 70 to 80% by weight. This is because if the ethylene content (hereinafter abbreviated as (E)) is less than 70% by weight, it cannot be made into solid pellets at room temperature and is difficult to handle, and if (E) exceeds 80% by weight, the impact properties will improve. This is because the effect of

From an economic perspective, the cost of the latter is about twice as high as that of the former, so it is important to use as much random copolymer as possible inside the block copolymer. It is advantageous to increase the impact resistance of the block copolymer itself by using a block copolymer containing a copolymer component, and to minimize the amount of EP silane copolymer added afterwards.

Furthermore, in order to improve the rigidity of a molded article such as a bumper, talc is added to the above-mentioned block copolymer and EP silane copolymer system.

Even in this talc-added system, the above block copolymer and EP
The proportions of the silane copolymer are the same.

(Problems to be solved by the invention) The current trend in plastic bumpers is that while previous plastic bumpers have replaced the shape of the conventional iron bumper with resin, the characteristics of plastic have been improved. It is turning into a bumper that makes use of it. Specifically, this involves increasing the size of the bumper and painting it, such as the aero bumper that integrates the bumper and skirt. This necessarily requires a coating and also requires extremely good impact resistance. Thus, modern Bamba materials are required to contain a relatively large amount of EP silane copolymer in order to improve impact resistance at low temperatures, and to be able to form large-sized materials well.

However, in such systems, circular depressions called voids are generally likely to occur on the surface of the molded product.

This is due to the fact that the bumper is enlarged so that sufficient holding pressure is not applied during molding, and that it contains a large amount of EP silane copolymer. If we consider the cause of void generation in detail, we will find that in the molding material, the polypropylene component and EP
The silane copolymer components are not compatible and form a seabird structure. The molding material is then injected into the mold and cooled from the mold surface, thereby exerting a tensile force inside the molded body. To compensate for this, the holding pressure replenishes new material, but if the holding pressure is insufficient, the area is placed under tensile stress. This stress is estimated to be concentrated at the interface between the polypropylene component and the EP silane copolymer component, and when this interface peels off, a disc-shaped vacuum is formed inside the molded body. The more the EP silane copolymer component is present, the easier the vacuum pores will grow, and if they grow larger, dents will occur on the surface of the molded product. That is,
A void is a type of sink mark, and if it is painted, it will be more noticeable than an unpainted one.

Based on the above, voids are likely to occur if the conventional method of adding BP silane copolymer to block copolymer is used to simultaneously achieve the increased size, paintability, and impact resistance required for future resin bumpers. (There was a point that this resulted in a decline in marketability.

(Means for Solving the Problems) As a result of various studies in order to solve the above problems, the present inventors have determined that at least part or all of the EP silane copolymer to be added later is a propylene-α-olefin random The present invention was achieved by discovering that if a copolymer is used, voids do not occur or are extremely unlikely to occur.

Here, the propylene-α-olefin random copolymer is one in which the propylene content exceeds 50% by weight, and the α-olefin is generally ethylene. In addition,
If the propylene content is 70% by weight or more, it can be made into solid pellets at room temperature, making it easier to handle, and if the propylene content is 80% by weight or less, the impact resistance is further improved. For the above reasons, the propylene-α-olefin random copolymer of the present invention is a propylene-ethylene random copolymer having a propylene content of 70% by weight or more and 80% by weight or less (hereinafter referred to as P-E random copolymer). is generally and preferably used.

Therefore, in the first aspect of the present invention, by adding an amorphous propylene-ethylene random copolymer to a crystalline ethylene-propylene block copolymer, the impact resistance is extremely good and the coating is coated without forming voids. Provides a bumper with a good later appearance.

The second aspect provides a bumper that has good rigidity, no voids, and a good appearance after painting, although the impact resistance is slightly inferior to the first aspect.

Table 1 shows the physical properties targeted by the composition of the present invention.

Hereinafter, the present invention will be explained based on the configuration.

The block copolymer (A) used in the polypropylene composition of the present invention is selected from a polypropylene component whose content insoluble in boiling n-hebutane is 95% by weight or more, preferably 97% by weight or more. If it is less than 95% by weight, the flexural modulus (rigidity) of the molded product obtained from the composition of the present invention will not satisfy the physical property targets shown in Table 1, and the thermal deformability of the Bamba molded product will also be insufficient.

Furthermore, (A) has an ethylene content of 3 to 15% by weight.
゛, the amount [A'] of the produced amorphous ethylene propylene random copolymer component existing inside the whole (A) is 1
00% by weight, 5 to 30% by weight is used. 2 More preferably, [A'] is 10 to 25 percent.

In terms of weight, it is preferable to use 20 to 25% by weight. In addition, (A) is MFR (melt flow rate) (g
/230°C for 10 minutes) is preferably from 5 to 40; if it is less than 5, the resulting composition will have insufficient moldability, and if it exceeds 40, the impact resistance will be insufficient.

Next, as for the amorphous propylene-α-olefin random copolymer (B), it is preferable to use an amorphous propylene-ethylene random copolymer (P-IE silane copolymer), which corresponds to MFRo of 1 to 2. It is preferable to use one having a molecular weight. PP if MFR is less than 0.1
It is difficult to disperse into the inside, and if it is larger than 2, the impact resistance is insufficient.

Next, the optionally added amorphous ethylene-propylene random copolymer (C) will be explained. This is used in combination with (B) if it does not adversely affect the generation of voids. Although it should be selected depending on the shape of the bumper to be molded, it is preferable to use one with as low a cyclohexane insoluble content as possible and with an MFR equivalent to CB).

The proportions of the components (A), (B), and (C) will be explained.

This amount ratio varies depending on the amount [A'] of the random copolymer component contained in (A). (A') is the elution rate (%) when (A) is extracted in xylene at 140''C for 2 hours multiplied by the amount of addition [A] of (A).
8' E, amount of (B) [:B), amount of (C) (
C) as each weight%, preferably 25≦(A')
+(B)+[C]≦45, more preferably 30
≦[A′]+(B)+(C)≦35. (A')>0, preferably 10-15 (B)>O
1 Preferably ≧5, more preferably ≧10, (C)≧0
It is. In addition, (A') + CB] + (C) <
25 has insufficient impact resistance, and [8') + [B
]+(C)>45, the rigidity is insufficient and voids are likely to occur; 35<(A')+(B)+[C
)≦45, voids may occur depending on the shape of the molded product. In order to preferably achieve the object of the present invention, it is desirable to use CB〉(C).

The reason why voids are less likely to occur in the present invention is not completely clear, but the adhesion of the interface between the PP component and (B) is
This is thought to be because the adhesion between the component and (C) is superior to that of the interface.

Next, in the second aspect of the present invention, the stiffness of the bumper can be improved, and the structure for this purpose is the addition of talc.

If talc with an average particle size exceeding 3 μm is used, the impact resistance at low temperatures will be significantly lowered, so use one having an average particle size of 3 μm or less. When the amount of talc added is 9% by weight or more, the effect of improving rigidity becomes remarkable. 9% by weight depending on the purpose
The stiffness improves according to the amount of talc added, even if it is less than
Although voids do not occur, if high rigidity is desired,
It is preferable to add 9% or more. Also, talc is 15
If it exceeds the weight percentage, the impact resistance will decrease, the bumper will have excessive rigidity, and the flexibility, which is a characteristic of resin bumpers, will decrease, which is not preferable. Talc may be used untreated, but in order to improve its adhesion and dispersibility with resin, it can be treated with various organic silane coupling agents, fatty acids and their salts, esters, silicone oil, etc. You may use one whose surface has been coated.

In the polypropylene composition of the present invention, pigments, dyes, antioxidants, ultraviolet absorbers, ultraviolet stabilizers, antistatic agents, nucleating agents, which are generally used in polypropylene compositions,
A lubricant or the like can be used as appropriate. As a lubricant, oxidized polypropylene wax (manufactured by Sanyo Kasei Co., Ltd., Viscole 660P, Viscole TS-200) was added at 0.5 to 1
When using % by weight, not only the fluidity but also the flexural modulus is improved. This is considered to be because the oxidized groups improve the dispersion of talc. If the lubricant is less than 0.5% by weight, the effect will be insufficient, and if it exceeds 1% by weight, the low temperature impact will be reduced.

Desired physical properties can be obtained from the polypropylene composition of the present invention by kneading it with a batch kneader such as a Panbury mixer or kneader or a continuous kneader such as a twin-screw extruder. - In a fine crusher, shearing is generally insufficient and good dispersion cannot be obtained, so it is considered difficult to obtain desired physical properties.

FIG. 1 shows a bumper used to evaluate the moldability and appearance (including voids) of the composition of the present invention.

In Figure 1, 21 is approximately 1700 nm, S11 is approximately 300 nm,
2° is approximately 200mm. This bumper is painted and has a smooth surface without any unevenness such as grains.

Further, the test piece for measuring the physical property values of the present invention can be obtained directly by injection molding, or by obtaining a flat plate or the like by injection molding and cutting it out from the flat plate.

Note that the addition of α-olefin polymers such as PP homopolymer and various polyethylenes to the block copolymer is within the scope of the present invention.

(Examples and Comparative Examples) The present invention will be described below based on Examples and Comparative Examples. The various measurement methods used on the opposite side are as follows.

(a) Coefficient of linear expansion Measured in accordance with ASTM D696 (measurement temperature 23°C to 80°C).

(t+)MFR Measured in accordance with JIS K 6758.

(c) Flexural modulus (three-point bending modulus) Measured in accordance with JIS K 7203 (measurement temperature 2
3℃) (d) Izot impact strength Measured in accordance with JIS K 7110 (measurement temperature -
40°C) (ne) Gloss rate Measured in accordance with JIS Z 8741 (reflection angle 60°C)
°) (f) Visually evaluate the flow marks on the external molded product (bumper) (
O...Excellent, Δ...Good, ×...Poor).

(g) Paintability Paintability was evaluated by measuring the peeling strength of the paint film. The peeling strength of the paint film was determined by the following method.

After cleaning the surface of the test piece by contacting the test piece with trichloroethane vapor for 30 seconds, a two-component acrylic-chlorinated polypropylene undercoat (manufactured by Nippon B Chemical Co., Ltd.) was applied to a film thickness of 40 mm. Apply the coating to a volume of ~50 μl, dry at 120°C for 10 minutes, leave it at room temperature for 10 minutes, and then apply a two-component acrylic-urethane top coat (manufactured by Nippon B Chemical Co., Ltd.) to the thickness of the film. is 30-40
It was coated to a thickness of .mu.m, dried at 120"C for 20 minutes, and left at room temperature for 48 hours to obtain a coated product.

Using an NT cutter, two incisions are made in the coating film of this coated product, spaced at 1 cm intervals. Part of the cut edge of the 1cm wide coating film was peeled off in advance, the test piece was fixed on the fixed side of the tensile tester, and the partially peeled coating film was fixed on the movable side of the tensile tester. 10mm/ in the direction of °
The coating film was pulled at a speed of 1.5 to 10 cm, and the beer strength of the coating film at 11 widths was determined.

(h) Void clamping force 2000) Visually evaluate the bumper shaped as shown in Fig. 1 molded with an injection molding machine (0...no void, A...slight and unnoticeable, B... ...easily distinguishable, C...extremely noticeable). The injection molding conditions were selected so that the appearance of each material would be as good as possible within a range compatible with the maintenance of Sumisan, equipment, and molds.

As the block copolymer (A), A1-A shown in Table 2
I chose 4. The table shows the amount (% by weight) of the amorphous random copolymer component generated inside each block copolymer.

Amorphous propylene-α-olefin random copolymer (
As B), the following propylene-ethylene random copolymer was used.

Note that these satisfy the selection condition (B) above.

BI 54030 (Mitsui Petrochemicals, product name) MF
R0,58253025 (same as above) MFR1 The following two types were selected as the optionally added amorphous ethylene-propylene random copolymer (C). These satisfy the selection condition (C) above.

CI Tafuma P680 (manufactured by Mitsui Petrochemicals, product name) C2EPO2 (manufactured by Nippon Rigid Rubber, product name) Takuru (D
), we selected the following two types.

oILMS200 (manufactured by Fuji Talc, product name) 02M
MR (Asada flour milling type, product name) In addition, various stabilizers and colorants are black in color.
It was adjusted to have heat resistance and weather resistance stability suitable for banba.

The composition (wt%) is shown in Table 3, and the evaluation results are shown in Table 4.

(Effect of the invention) As is clear from the above examples, the composition of the present invention has the following properties:
In order to improve impact resistance and paintability, a large amount of random copolymer is added to create a highly marketable bumper that does not generate voids and has a good appearance even when molded into large-sized bumpers such as Aero Bamba. I will provide a.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a bumper used to evaluate the moldability and appearance (including voids) of the composition of the present invention.

Claims (1)

[Claims] 1. A composite polypropylene composition mainly comprising a crystalline ethylene/propylene block copolymer and an amorphous propylene-α-olefin random copolymer.