JPS58210949A - Preparation of impact-resistant polypropylene composition - Google Patents

Abstract

PURPOSE:To improve impact resistance and whitening resistance of polypropylene with keeping characteristics of its own, by subjecting polypropylene together with a specific ethylene-alpha olefin copolymer resin in the presence of an organic peroxide to degradation in molecular weight. CONSTITUTION:Polypropylene having 0.03-10g/min MFI (at 230 deg.C at 2.16kg load) is blended with 5-50wt% ethylene-alpha-olefin copolymer resin, and subjected to degradation in molecular weight using an organic peroxide in such a way that MFI increases by 2-100 times. Propylene homopolymer, propylene-ethylene random copolymer having <=10wt% ethylene content, etc. are used as the propylene. An ethylene-alpha-olefin copolymer resin having 0.1-50g/10min MI (at 190 deg.C at 2.16kg load), 0.91-0.935g/cm<3> density and 3-20C alpha-olefin is used as the ethylene-alpha olefin copolymer resin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene composition having excellent impact whitening resistance, gloss, transparency and impact resistance.

Polypropylene has excellent mechanical properties and is widely used. Among them, propylene with improved impact resistance.
Ethylene block copolymers are widely used, especially in the injection molding field, due to their increased rigidity. However, propylene-ethylene block copolymers generally whiten when subjected to impact or when bent, which can significantly reduce commercial value depending on the application.

The present inventors made careful efforts to obtain a composition with excellent impact resistance and white color resistance while retaining the inherent W properties of polypropylene, and as a result, they combined polypropylene with a specific ethylene-α-olefin copolymer resin. The present invention was achieved by discovering that a composition having excellent moldability and satisfying the above-mentioned physical properties can be obtained by melt-kneading in the presence of a radical generator to reduce the molecular weight.

That is, the UMF I of the present invention is 0.03 to 10? 5 to 50% of ethylene-α-olefin copolymer resin was mixed with polypropylene for 10 minutes, and MFI was applied using organic peroxide.
The present invention provides a method for producing an impact-resistant polypropylene composition with excellent whitening resistance, characterized in that the molecular weight of the polypropylene is reduced to 2 to 100 times that of the original polypropylene.

The effect of the present invention is that when the polypropylene is homopolypropylene or a propylene-ethylene random copolymer, the impact resistance is greatly improved by the method of the present invention, and the whitening resistance and transparency are higher than that of the polypropylene alone. However, it is possible to obtain a composition that has a much better balance of these physical properties than conventional impact-resistant polymer and Robyrene compositions.

Furthermore, in the case of an ethylene/propylene block copolymer in which polypropylene is open, the method of the present invention significantly improves impact resistance and whitening resistance, and the present invention is characterized by a high melt flow composition. Even when manufactured, it shows not only high impact resistance but also excellent tensile elongation, which further improves the practical impact resistance of molded products.

In general, impact resistance rapidly decreases as MFI increases, but in the case of the present invention, a composition with a low MFI before molecular weight reduction using an organic peroxide is compared to a composition with a very high MFI after molecular weight reduction. has better impact resistance. (Comparison of Comparative Example 1 and Actual Sister Example 1) This indicates that the effect of the present invention is not due to the increased compatibility of the blend composition due to mixing at a high molecular weight, but due to the subsequent peracid and arsenic compound. This is thought to be due to the effect of electrical degeneration, and the possibility of light crosslinking of both components by radicals is considered. Another advantage of the present invention is that the soluble content in solvent oils and fats does not increase compared to rubber blending, which has been conventionally used to improve the impact resistance of PP, and is therefore a preferred method from the viewpoint of food hygiene.

Polypropylene of the present invention and l-1: 230°C, am
2.16Kg Te measured MF I 0.03-1 (
1/10 minute propylene homopolymer, ethylene content 1
It is one selected from a propylene ethylene random copolymer having an ethylene content of 0% by weight or less and a propylene ethylene block copolymer having an ethylene content of 3 to 30% by weight, or a mixture of two or more thereof.

If the MFI is less than 0.03 r/10 minutes, a large amount of organic peroxide is required to obtain a composition with preferable moldability, which may cause deterioration of the color and texture of the composition.

Furthermore, if the time exceeds 710 minutes, the melt viscosity decreases and the dispersibility with the ethylene-α olefin copolymer resin deteriorates, resulting in a poor effect of improving the impact resistance in the lower part.

Ethylene-α olefin copolymer resin is MI (19
0℃, 2.16Kg load) 7% 0.1~50?
/10 min, density 0.910-0.935 f/c
It is a copolymer of ethylene (tl) and one or more α-olefins having 3 to 20 carbon atoms, and is linear low-density polyethylene. The mixing ratio of the above ethylene-α olefin copolymer resin to polypropylene is 5 to 5.
If the content is less than 5% by weight, the effect of improving impact resistance and whitening resistance will be poor, and if it exceeds 50% by weight, the elongation of the molded product will deteriorate.

Organic peroxides used in the present invention include hydrocarbons, alkyl peroxides, acyl peroxides, ketone peroxides, alkyl peresters, and peroxides having a half-life of about 1,400 to 260 degrees per minute. Examples of carbonates include silicone peroxides (for example, tertiary butyl hydroperoxide, tertiary methyl peroxyimpropyl carbonate)
, 2,5-dimethyl-2,5-di, (tertiary methyl peroxyisogropyl) hexane rubber oxide, l, 3 bis (tertiary methyl peroxy isoglopyl) benzene, benzoyl peroxide, methyl inbutyl ketone peroxide Oxide, tertiary butyl perbenzoate cumene hydroperoxide, diisopropylbenzene hydroperoxide and the like can be mentioned.

The organic peracid is added so that the MFI of the composition after molecular weight reduction is 2 to 100 times that of the original polypropylene, and is usually selected in a range of o, oi to 1.0% by weight.

The method for mixing the polypropylene, the ethylene-α olefin copolymer, the position 1 fat, and the organic peracid can be either by mixing the three and melt-kneading, or by melt-kneading the first two and then adding the organic peracid. You may melt and knead again. The kneading can be carried out using devices used in ordinary melt mixing methods, such as a screw extruder heated roll or a Banbury epsilon mixer.

The composition obtained by the method of the present invention can be suitably used in a wide range of general injection molding fields, but it can also be used in film fields such as composite films and retort films, as well as blow molding fields, etc. by taking advantage of its transparency and impact resistance. can also be usefully used.

Next, the present invention will be explained in more detail by giving Examples and Comparative Examples. The physical properties of the compositions shown on each side were measured by the following method.

(a) Preparation of sample plate The pellet was molded into a flat plate with a thickness of 2 cavities using a 10-ounce injection molding machine, and was used as a test sample.

(b) Whitening resistance Injection molded flat plate with a thickness of 2 cm and a height of 50 crn to 30 cm
The size of the white spot that occurs when a steel ball of 01 is dropped is
Displayed on a scale of 10 (good) to 10 (bad). Rank IU, homopolypropylene l' propylene ethylene random copolymer, rank IOH MFI about 30 f
/ 10 minute block copolymer (manufactured by Showa Denko Co., Ltd.)
MK711).

(c) Izot impact strength ASTM D256) Tensile strength ASTM D638 Example I MF I 0.41 r/l (L polypropylene homopolymer powder 8.5 Kq copolymerized with butene-1 MI 7.02 /10 min density 0.9208 y/c
c linear low density polyethylene powder 1.5 KL! and 1,3bis(tert-butylperoxyisopropyl)benzene51 as an organic peroxide and 2,
6 di-tertiary butylene (l) methyl phenol St, calcium stearate 102, and similystyl thiodipropionate 10F were mixed in a Henschel mixer and subjected to crosstalk molecular weight reduction at 230°C using an Ω extruder for 40 minutes. .

The MFI of the obtained pellets was 12.4r710 minutes.

Comparative Example Kneading was carried out in exactly the same manner as in Example 1, except that no organic peroxide was used, to obtain pellets having an MF I of 0.4+1/10 min.

Comparative Example 2 Pellets with an M FI of 11°6F/10 minutes were obtained in exactly the same manner except that the linear low-density polyethylene was not used and the polypropylene powder was changed from 9 to 10.

Comparative Example 3 M F as polypropylene without using organic peroxide
The same procedure as in Example 1 was carried out except that I 13 flIQ was used to obtain a pellet of MF I 12.2 y710.

Comparative Example 4.5 Linear low density polyethylene with a density of 0. c+17o y
/cc, M I 7. High-pressure polyethylene with O1710 min (Comparative Example 4) and density 0.945y/cc1M 1
7. Processed in exactly the same manner as in Example 1 except for changing to high-density polyethylene of 81710 min (Comparative Example 5), and Mp11
3. ty/10 minutes (Comparative Example 4) and I2.0 g/10 minutes (Comparative Example 5) were obtained.

Example 2 Density 0.9162y/C as linear low density polyethylene
The procedure of Example 1 was repeated except that a hexene-1 copolymer with a C, MI of 0.81710 minutes was used and the amount of peroxide was changed to 61, to obtain pellets with an MF I of 13.5 r/10 minutes.

Example 3 Density 0.9296 r/CC, M I 1.3 f
The same procedure as in Example 2 was carried out except that 25% of hexene-1 copolymer of 710 min was added, and M F I 10.4 r
A pellet of 710 minutes was obtained.

Example 4.5 MF12:L5
Sl' / 10 minutes (actual gun example 4), 4.3? /10
(Example 5) pellets were obtained, Actual gun example 6 ethylene content 3.6 weight ratio MF as polypropylene
Using a propylene-ethylene random copolymer of 10.48 SJ/l (l) and copolymerizing octene-1 as linear low density polyethylene, M I 2.1 f/l LO fractional density 0.9174 f/cc was used. The procedure was repeated in the same manner as in Example 1, except that 2,5-dimethyl-2,5-di(tertiary methylperoquine)hexane ff:4P was used as the organic peroxide. Profit/hi.

Comparative Example 6 Same as Example 6, except that linear low density polyethylene was not used, propylene-ethylene copolymer was used 1OK9, and M
A pellet with FI8.2P/10 minutes was obtained.

Example 7 M F I O, 86f 710 as polypropylene
The procedure was carried out in the same manner as in Example 1, except that the propylene ethylene block copolymer with an ethylene content of 8.6% was used at 9.2 Kq, the amount of linear low density polyethylene was set at 0.8 Ky, and the amount of organic peroxide was set at 42. M F I 10.2 r, /
A 10 minute pellet was obtained.

Comparative Example 7 The same procedure as in Example 7 was conducted except that linear low-density polyethylene was not used to obtain pellets with an M FI of 12.3 f and 710 minutes.

Claims (1)

[Scope of Claims] A polypropylene resin composition characterized by mixing 5 to 50'% of an in-copolymer resin and reducing the molecular weight of MFI to 2 to 100 times that of the original polypropylene using an organic peroxide. A method for producing an impact-resistant polypropylene composition with excellent whitening properties. (2) Claims in which the polypropylene is at least one selected from a propylene homopolymer, a propylene ethylene random copolymer with an ethylene content of 10% by weight or less, and a propylene-ethylene block copolymer with an ethylene content of 20% by weight or less 2. A method for producing an impact-resistant polypropylene composition according to item 1. (3) Ethylene-α-olefin copolymer resin has a density of 0
．． 1. The method for producing an impact-resistant polypropylene composition according to claim 1 or 2, wherein the α-olefin is an α-olefin having 3 to 20 carbon atoms.