JP3377117B2 - Non-whitening polypropylene resin composition with excellent discoloration resistance - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a whitening-resistant polypropylene resin composition having excellent discoloration resistance, and more specifically, it is discolored even when it is brought into contact with foods, especially vegetables such as Chinese cabbage and spinach for a long time. The present invention relates to a polypropylene-based resin composition which is excellent in discoloration resistance such as no problem and is also excellent in mechanical properties such as whitening resistance, heat aging resistance, heat resistance, rust resistance, impact strength and bending strength.

[0002]

2. Description of the Related Art Propylene / ethylene block copolymers are excellent in heat resistance, rigidity, and impact resistance, so that they can be used in various containers such as food containers, household containers, clothes cases,
It is used in large quantities in applications such as seal containers. However, the propylene / ethylene block copolymer has a drawback in that when an impact force such as hitting an object is applied, the part is whitened. In addition, discoloration may occur when the food is contacted for a long time. For this reason, when used in food containers, whitening and discoloration damage the commercial value, so discoloration resistance and whitening resistance (whitening resistance) are maintained while maintaining sufficient mechanical strength. Must also be met.

It is said that the discoloration caused by long-term contact with foods is due to the fact that pigments and nitrous acid contained in vegetables such as Chinese cabbage and spinach change the properties of additives such as antioxidants. There is. For this reason, hindered phenolic antioxidants which are said to cause significant discoloration (for example, JP-A-3-52962) are used, and hindered amine antioxidants which are said to cause little discoloration are used (for example, Japanese Patent Laid-Open No. Hei 3-259940, Japanese Patent Laid-Open No. Hei 3
-52959) and so on. However, these changes in antioxidants have not been fully satisfactory, including heat aging resistance and rust resistance. On the other hand, in order to realize whitening, improvements have been made by blending polyethylene with a propylene / ethylene block copolymer (for example, JP-A-55-10433). However, with this composition, a composition in which impact resistance, rigidity, heat resistance, and whitening resistance are sufficiently balanced has not been obtained. From this, impact resistance, rigidity, heat resistance,
A polypropylene resin composition having excellent whitening resistance has not yet been developed.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is not to cause problems such as discoloration even after contact with foods, particularly vegetables such as Chinese cabbage and spinach, for a long time, and also to be whitening resistance, heat aging resistance and heat resistance. A polypropylene resin composition having excellent rust resistance and having well-balanced mechanical properties such as impact resistance and flexural strength is provided.

[0005]

Means for Solving the Problems In view of the above, the present inventors have made diligent studies to solve these problems, and as a result, identified propylene / ethylene block copolymers, propylene / ethylene random copolymers and high density polyethylene. It was found that the above problems can be solved by blending a specific amount of an organic phosphorus antioxidant, a hindered phenolic antioxidant and an acid absorber with respect to the resin component containing the amount, and the present invention has been accomplished. It was.

The invention of claim 1 of the present invention is (A) propylene / ethylene block copolymer 50 to 90% by weight (B) propylene / ethylene random copolymer 5 to 45% by weight (C) density 0.94 g / Cm ³ or more high-density polyethylene resin 5 to 45 parts by weight of resin component 100 parts by weight containing at least the following (D)-(F) additive components, characterized in discoloration resistance It is an excellent whitening polypropylene resin composition. (D) Organophosphorus antioxidant 0.01 to 0.5 parts by weight (E) Hindered phenolic antioxidant 0.01 to 0.1 parts by weight (F) Acid absorbent 0.02 to 0.3 Parts by weight

According to the second aspect of the present invention, the melt flow rate of the (A) propylene / ethylene block copolymer is 4 to 60 g / 10 min., The ethylene content is 5 to 20% by weight,
Intrinsic viscosity of ethylene / propylene copolymer part 1.5-8d
1 / g, (B) the propylene / ethylene random copolymer has a melt flow rate of 6 to 50 g / 10 min., an ethylene content of 1 to 10% by weight, and (C) a density of 0.94.
The whitening-resistant polypropylene resin composition having excellent discoloration resistance according to claim 1, wherein the melt flow rate of the high-density polyethylene of g / cm ³ or more is 0.2 to 25 g / 10 min.

The present invention will be further described below. The (A) propylene / ethylene block copolymer of the present invention comprises a solid catalyst component containing a transition metal and an organoaluminum compound or a catalyst system obtained from these electron-donating organic compounds to produce ethylene and propylene. It is obtained by performing block copolymerization in multiple stages of stages or more. The solid catalyst component is widely known in the polymerization of propylene, and titanium trichloride or a eutectic thereof, a trivalent or tetravalent titanium compound or a carrier thereof such as a magnesium compound, or the compound and other compounds. Typical examples include those obtained by processing.

The propylene / ethylene block copolymer component (A) used in the present invention is not limited to one kind of polymer obtained by polymerizing in one polymerization reaction system, and two or more kinds separately polymerized. It may be a mixture of the above propylene / ethylene block copolymer. The melt flow rate of the propylene / ethylene block copolymer component (A) (the discharge amount of the molten resin for 10 minutes when a load of 2,16 kg at 230 ° C. is applied; hereinafter, referred to as MFR) is 4 to 60 g / 10 min. , Preferably 5 to 50 g / 10
It is better to select from the range of min. MFR is 4g / 10min.
If it is less than 60 g, the workability is lowered, and if it is 60 g / 10 min. Or more, the impact resistance becomes insufficient.

The propylene / ethylene block copolymer component (A) has an ethylene content of 5 to 20% by weight, preferably 5 to 10% by weight. If the ethylene content is less than 5% by weight, the impact resistance decreases, and
If it is more than weight%, the rigidity becomes insufficient. The ethylene content in the present invention is a value measured by the ¹³ C-NMR method.

Regarding the molecular weight of the propylene / ethylene copolymer portion of the propylene / ethylene block copolymer component (A), the intrinsic viscosity ([η]) of the decalin solution at 135 ° C. is 1.5 to 8 dl / g, preferably 2 to 6 dl. It is better to select from the range of / g. If the intrinsic viscosity of the propylene / ethylene copolymerized portion is less than 1.5 dl / g, the impact resistance becomes insufficient, and if it is 8 dl / g or more, the dispersion with the polypropylene homopolymerized portion becomes poor and it becomes a foreign substance.

The (B) propylene / ethylene random copolymer of the present invention is obtained by using a catalyst system obtained from a solid catalyst component containing a transition metal and an organoaluminum compound or an electron donating organic compound thereof to obtain ethylene and propylene. It is obtained by copolymerizing and. Typical examples of the solid catalyst component include those obtained by treating a carrier such as titanium trichloride or a eutectic thereof, or a magnesium compound with a trivalent or tetravalent titanium compound or the compound and another compound. To be

The (B) propylene / ethylene random copolymer used in the present invention is not limited to one kind of polymer obtained by polymerizing in one polymerization reaction system, and two or more kinds of separately polymerized. It may be a mixture of propylene / ethylene random copolymer.

The ethylene content of the (B) propylene / ethylene random copolymer used in the present invention is preferably 1 to 10% by weight, particularly preferably 2 to 8% by weight. Ethylene content is 1
If it is less than 10% by weight, the effect of improving the whitening property is lowered, and if it is 10% by weight or more, the rigidity becomes insufficient. Ethylene content 1
Although a final composition excellent in impact resistance can be obtained even if it is out of the range of 10% by weight, in order to obtain the final composition in which the effects of improving rigidity, impact resistance, and whitening resistance are well balanced, Those within the range are preferable. The ethylene content in the present invention is a value measured by the ¹³ C-NMR method.

The MFR of the propylene / ethylene random copolymer (B) is usually 6 to 50 g / 10 minutes, preferably 7 to 45 g / 10 minutes. When the MFR is less than 6 g / 10 min., The workability is deteriorated, and when it is 50 g / 10 min. Or more, the impact resistance becomes insufficient.

The high density polyethylene (C) referred to in the present invention has a density of 0.94 g / cm ³ or more, preferably a density of 0.
High-density polyethylene polymerized at a medium or low pressure by a liquid phase method or a gas phase method using a known Ziegler-based catalyst of 945 g / cm ³ or more, ethylene alone or ethylene and an α-olefin having 3 to 12 carbon atoms And copolymers thereof, and specific α-olefins include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-dodecene and the like. If the density of the high-density polyethylene (C) is 0.94 g / cm ³ or less, the rigidity decreases. Melt flow index (load at 190 ° C 2,16k
Discharge amount of molten resin for 10 minutes when g is added. Less than,
Abbreviated as MFR) is 0.2 to 25 g / 10 min., Preferably 0.3 to 20 g / 10 min., More preferably 0.5 to 15
It is desirable to select from the range of g / 10min. If the MFR is less than 0.2g / 10min., The workability will be reduced to 25g / 10mi.
Above n., the impact resistance becomes insufficient.

Specific examples of the (D) organophosphorus antioxidant referred to in the present invention include (1) tris (mixed, mono and dinonylphenyl) phosphite, and (2) tris (2,4-). Di-t-butylphenyl) phosphite, (3) 4,4'-butylidene bis (3-methyl-6)
-T-butylphenyl-di-tridecyl) phosphite, (4) 1,1,3-tris (2-methyl-4-di-
Tridecyl phosphite-5-t-butylphenyl)
Butane, (5) bis (2,4-di-t-butylphenyl) pentaerythritol-di-phosphite,
(6) Tetrakis (2,4-di-t-butylphenyl)
-4,4'-biphenylene phosphonite, (7) bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-di-phosphite, (8) 2.
2'-ethylidene bis (4,6-di-t-butylphenyl) fluorophosphite, (9) methylenebis (4,6-di-t-butylphenyl) -2-ethylhexyl-phosphite and the like can be mentioned. Of these, preferred are (2) and (7). The compounding amount of the component (D) is 0.01 to 0.5 per 100 parts by weight of the resin composition.
Parts by weight, preferably 0.05 to 0.2 parts by weight. If it is less than this amount, the heat aging resistance becomes insufficient. On the other hand, even if added in a certain amount or more, the effect of improving the heat aging resistance reaches its peak, which is uneconomical.

Specific examples of the hindered phenolic antioxidant of the component (E) used in the present invention include (11)
n-octadecyl-β- (4′-hydroxy-3 ′,
5'-di-t-butylphenyl) propionate, (1
2) Tetrakis [methylene-3- (3 ', 5'-di-t
-Butyl-4'-hydroxyphenyl) propionate] methane, (13) 1,3,5-trimethyl-2,
4,6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, (14) calcium (3,5
-Di-t-butyl-4-hydroxy-benzyl-monoethyl-phosphate), (15) triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-)
Hydroxyphenyl) propionate], (16) 3,
9-bis [1,1-dimethyl-2- {β- (3-t-butyl-4-vidoxy-5-methylphenyl) propionyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5 , 5] Undecane, (17) Bis [3,3]
-Bis (4'-hydroxy-3'-t-butylphenyl) -butyric acid] glycol, (18) N, N'-bis [3
-(3,5-Di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, (19) 2,2'-oxamidobis [ethyl 3- (3,5-di-t-butyl-
4-Hydroxyphenyl) propionate], (20)
1,3,5-tris (3 ', 5'-di-t-butyl-
4'-hydroxybenzyl) -s-triazine-2,
4,6 (1H, 3H, 5H) -trione, (21) 1,
3,5-tris (4-t-butyl-3-hydroxy-
2,6-dimethylbenzyl) isocyanurate, (2
2) 3,5-di-t-butyl-4-hydroxyhydrocinnamic acid triethyl stills 1,3,5-tris (2-hydroxyethyl) -s-triazine-2,
4,6 (1H, 3H, 5H) -trione, and the like. The compounds of (12) and (16) are preferable. The amount of the component (E) added is 0.01 to less than 0.1 part by weight, preferably 100 parts by weight of the resin composition.
0.02 to 0.05 parts by weight. If it is 0.01 part by weight or less, the heat aging resistance of the resin composition is impaired, and if it is 0.1 part by weight or more, the problem of discoloration becomes strong, such being undesirable.

Examples of the (F) acid absorbent in the present invention include fatty acid metal salts, hydroxy fatty acid metal salts, fatty acids, hydrotalcites and the like. Fatty acids, fatty acid metal salts, such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid and other fatty acids and these fatty acids and lithium, sodium, magnesium, calcium, zinc and other metals Examples thereof include salts, but calcium stearate is particularly preferable.

Hydrotalcites are double salt compounds represented by the following formula, and both natural products and synthetic products can be used. In particular, synthetic products in which M ²⁺ is Mg and A ^n- is CO ₃ ^2-. Is preferred. (M ²⁺ ) _1-x Al _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (where 0 <X ≦ 0.5, m: real number, M ²⁺ : Mg, C
a or Zn, A ^n- : n-valent anion, n is an integer) The amount of the component (F) added is 0.02 to less than 0.3 part by weight relative to 100 parts by weight of the resin composition, Preferably,
It is 0.05 to 0.1 part by weight. If it is 0.02 parts by weight or less, the rust resistance of the resin composition is impaired, and if it is 0.1 parts by weight or more, discoloration easily occurs, which is not preferable.

[0021]

The whitening-resistant polypropylene resin composition having excellent discoloration resistance of the present invention is (A) propylene / ethylene block copolymer (abbreviated as block PP) 50 to 90% by weight, (B) propylene / ethylene random. Copolymer (abbreviated as random PP) 5 to 45% by weight, (C) density 0.9
Polypropylene resin composition in which at least the additive components (D) to (F) are mixed with 100 parts by weight of a resin component containing 5 to 45% by weight of high density polyethylene (abbreviated as HDPE) of 4 g / cm ³ or more. It is a thing. The component (A) itself is excellent in rigidity, mechanical strength, heat resistance, etc., but has the drawback of poor whitening resistance as described above. (B) as component (A)
When only the components are blended, the whitening property is improved, but the degree of improvement is insufficient and the low temperature impact strength is also lowered. Further, when only the component (C) is blended with the component (A), the whitening property is improved, but the degree of improvement is still insufficient and the heat resistance is lowered, so that it is not practical. When the blending ratio of the component (A) is 90% by weight or more, the whitening property deteriorates, and when it is 50% by weight or less, rigidity, mechanical strength, heat resistance and the like decrease. If the blending ratio of the component (B) is 45% by weight or more, the rigidity becomes insufficient, and if it is 5% by weight or less, the whitening property becomes insufficient. The blending ratio of component (C) is 45
If it is more than 5% by weight, the heat resistance will be insufficient, and if it is less than 5% by weight, the degree of improvement of the whitening property will be insufficient.

In the present invention, when a specific amount of the component (B) and the component (C) are blended with the component (A), the whitening property is improved and the rigidity, impact resistance, heat resistance, processability, etc. are improved. The reason why a balanced final composition can be obtained is not clear, but it is a result that a specific amount of the component (B) and the component (C) mixed with the component (A) act synergistically. Conceivable. The organophosphorus antioxidant of the component (D) contributes to the heat aging resistance together with the hindered phenolic antioxidant of the component (E) without particularly impairing the discoloration resistance.
The acid absorbent as the component (F) neutralizes free chlorine remaining in the copolymer and prevents rust due to corrosion of the extruder and the mold. As described above, addition of a specific amount of the component (D), the component (E) and the component (F) to the resin component containing the component (A), the component (B) and the component (C) in a specific ratio. Discoloration resistance is improved by blending agent components, and it is also excellent in whitening resistance, heat aging resistance, heat resistance, rust resistance, and a good balance of mechanical properties such as impact strength and bending strength. It is considered that a polypropylene resin composition having the above properties can be obtained.

[0023]

EXAMPLES The present invention is described in detail below with reference to examples, but the present invention is not limited to the examples without departing from the spirit of the present invention. (Test method) 1. Whitening test 100 under injection condition of resin temperature 230 ℃ and mold temperature 50 ℃
An injection plate having a thickness of mm × 200 mm × 2 mm was molded, a 1 kg weight was dropped from a height of 20 cm using a DuPont impact tester, and the whitening degree of the sample was observed for up to 4 days and visually determined. Judgment criteria ◎: No whitening spread at all ○: No whitening spread but whiteness is more noticeable △: Whitening spread is slightly present and whitening is noticeable ×: Whitening spread is large and whitening is very noticeable

2. Food Contamination Test After adding salt to Chinese cabbage, immerse the test piece of injection plate (2mm thickness) in juice crushed finely with a mixer at 40 ° C.
After left for 4 days in a thermostatic chamber, the degree of discoloration was visually evaluated. Judgment Criteria ◎: No discoloration ○: Light discoloration △: Discoloration visible, discoloration ×: Dark discoloration

3. Heat aging test A test piece of an injection plate (2 mm thick) was placed in an oven at 150 ° C, and the judgment was made by the time when the surface turned brown. ◎: 10 days or more ○: 3 to 10 days △: 1 to 3 days ×: less than 1 day

4. Rust test Soft iron plate is embedded in molten resin for 2 hours, then cooled 5
After being left in a thermostatic chamber at 0 ° C. and a humidity of 98% or more for 20 hours, the soft iron plate was taken out from the resin, and the state of rust generation was visually determined. ⊚: No rust was generated. ○: Light rust slightly adhered in spots. △: Light rust adhered to about 1/3. ×: Dark rust adhered to the entire surface.

5. Flexural modulus; tested according to ASTM D790.

6. Impact strength (Izod); JIS K
Tested according to 6758.

7. Heat resistance (deflection temperature under load); JIS
Tested according to K7207.

(Resin component) (a) Block PP; MFR = 8 g / 10 min, C ₂ content = 7.5% by weight, intrinsic viscosity of ethylene / propylene copolymer part = 3.0 (decaline [η at 135 ° C. [η ]The value of the). (B) Block PP; MFR = 45 g / 10 minutes, C ₂ content = 7.5% by weight, intrinsic viscosity of ethylene / propylene copolymer portion = 2.5 (value of [η] at decalin 135 ° C.). (C) Random PP; MFR = 8 g / 10 min, C ₂ content = 3 wt% (d) Random PP; MFR = 45 g / 10 min, C ₂ content = 2.7 wt% (e) HDPE; MFR = 5 0.3 g / 10 min, density =
0.963 g / cm ³ (f) HDPE; MFR = 17 g / 10 min, density = 0.
958 g / cm ³

(Additive component) (a) Organophosphorus antioxidant; tris (2,4-di-t)
-Butylphenyl) phosphite (trade name; Irgaphos-168, manufactured by Ciba Geigy) (b) Organophosphorus antioxidant; bis (2,6-di-t-)
Butyl-4-methylphenyl) pentaerythritol-
Diphosfight (trade name; ADEKA STAB PEP-3)
6. Asahi Denka Kogyo Co., Ltd. (c) Hindered phenolic antioxidant; tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4']
-Hydroxyphenyl) propionate] methane (trade name; Irganox-1010, manufactured by Ciba Geigy) (d) Hindered phenolic antioxidant 3,9-bis [1,1-dimethyl-2- {β- (3- t
-Butyl-4-vidroxy-5-methylphenyl) propionyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane (trade name; ADEKA STAB AO-80, Asahi Denka Kogyo Co., Ltd.) (Product name: Sumilizer GA-80, manufactured by Sumitomo Chemical Co., Ltd.) (e) Acid absorbent; Calcium stearate (f) acid absorbent; Hydrotalcite (trade name: DHT
-4A, manufactured by Kyowa Chemical Co., Ltd.)

Example 1 A resin component having the composition shown in Table 1,
Mixing the additive components, resin temperature 230 ℃, mold temperature 50
An injection plate having a thickness of 100 mm × 200 mm × 2 mm was molded under the injection condition of ° C. and various tests were conducted. The results are shown in Table 1.

(Examples 2 to 7) In the same manner as in Example 1, injection plates were molded with the formulations shown in Table 1 and various tests were conducted.
The results are also shown in Table 1.

Comparative Example 1 An injection plate was molded using only the block PP (a) with the composition shown in Table 1 and various tests were conducted. The results are also shown in Table 1. It has excellent workability, rigidity, mechanical strength, etc., and is also excellent in discoloration resistance, heat aging resistance, heat resistance, and rust resistance, but its whitening resistance is insufficient.

(Comparative Example 2) An injection plate was molded using the block PP (a) and the random PP (c) with the composition shown in Table 1 and various tests were conducted. The results are also shown in Table 1.
Excellent workability, rigidity, mechanical strength, etc., and resistance to discoloration,
It is also excellent in heat aging resistance, heat resistance, and rust resistance, but the degree of improvement in whitening resistance is insufficient.

(Comparative Example 3) Block PP (a) and HDP
Using E (e), mold the injection plate with the composition shown in Table 1,
Various tests were conducted. The results are also shown in Table 1. It is excellent in workability, rigidity, mechanical strength, etc., and is also excellent in discoloration resistance, heat aging resistance, heat resistance, and rust resistance, but the degree of improvement in whitening resistance is insufficient.

(Comparative Example 4) An injection plate was molded by using block PP (a), random PP (c) and HDPE (e) without using a hindered phenolic antioxidant and using the composition shown in Table 1. Then, various tests were conducted. The results are also shown in Table 1. Excellent workability, rigidity, mechanical strength, etc.
It is also excellent in discoloration resistance, rust resistance, whitening resistance, and heat resistance, but its heat aging resistance is insufficient.

(Comparative Example 5) An injection plate was molded by using block PP (a), random PP (c) and HDPE (e) without using an organophosphorus antioxidant and using the composition shown in Table 1. , Various tests were conducted. The results are also shown in Table 1. It has excellent workability, rigidity, mechanical strength, and the like, and is improved in heat aging resistance, heat resistance, rust resistance, and whitening resistance, but its discoloration resistance is insufficient.

(Comparative Example 6) Block PP (a), random PP (c) and HDPE (e) were used without using an acid absorbent, and an injection plate was molded according to the composition shown in Table 1 to obtain various types. The test was conducted. The results are also shown in Table 1. It has excellent workability, rigidity, mechanical strength, heat aging resistance, heat resistance, whitening resistance, and discoloration resistance, but rust resistance is insufficient.

[0040]

[Table 1]

(Comparative Example 7) The resin components (A) to (C) and the additive components (D) to (F) were all mixed in the proportions shown in Table 2. An injection plate was molded using a resin composition whose amount was outside the range of the present invention, and various tests were conducted. The results are shown in Table 2. It has excellent workability, mechanical strength, heat aging resistance, whitening resistance, discoloration resistance, and rust resistance, but insufficient rigidity and heat resistance.

(Comparative Example 8) The resin component (A) whose content is outside the range of the present invention, the resin component (C) and the components (D) to
(F) An injection plate was molded using the resin composition containing the additive components in the mixing ratio shown in Table 2, and various tests were conducted.
The results are shown in Table 2. It is excellent in workability, rigidity, mechanical strength, heat aging resistance, heat resistance, discoloration resistance, and rust resistance, but insufficient whitening resistance.

(Comparative Example 9) The resin components (A) to (C) and the additive components (D) to (F) were all compounded in the compounding ratios shown in Table 2, but (B) and (C). Various tests were carried out by molding an injection plate using a resin composition having a resin component content outside the range of the present invention. The results are shown in Table 2. It has excellent workability, mechanical strength, heat aging resistance, whitening resistance, discoloration resistance, and rust resistance, but insufficient rigidity and heat resistance.

(Comparative Example 10) The resin components (A) to (C) and the additive components (D) to (F) were all compounded in the compounding ratios shown in Table 2, but the resin component (B) was contained. An injection plate was molded using a resin composition whose amount was outside the range of the present invention, and various tests were conducted. The results are shown in Table 2. Workability, rigidity,
It has excellent mechanical strength, heat aging resistance, heat resistance, discoloration resistance, and rust resistance, but insufficient whitening resistance.

(Comparative Example 11) The resin components (A) to (C) and the additive components (D) to (F) were all compounded in the compounding ratios shown in Table 2, but (B) and (C). Various tests were carried out by molding an injection plate using a resin composition having a resin component content outside the range of the present invention. The results are shown in Table 2. Excellent workability, rigidity, mechanical strength, heat aging resistance, discoloration resistance, rust resistance, and whitening resistance, but insufficient heat resistance.

(Comparative Example 12) The resin components (A) to (C) and the additive components (D) to (F) were all compounded in the compounding ratios shown in Table 2. An injection plate was molded using a resin composition whose amount was outside the range of the present invention, and various tests were conducted. The results are shown in Table 2. Workability, rigidity,
It has excellent mechanical strength, heat aging resistance, heat resistance, discoloration resistance, and rust resistance, but insufficient whitening resistance.

[0047]

[Table 2]

[0048]

The whitening polypropylene resin composition having excellent discoloration resistance of the present invention comprises (A) a propylene / ethylene block copolymer, (B) a propylene / ethylene random copolymer and (C) a density of 0. For a resin component containing a specific amount of high-density polyethylene of 0.94 g / cm ³ or more,
A resin composition containing a specific amount of (D) an organophosphorus antioxidant, (E) a hindered phenolic antioxidant, and (F) an acid absorbent, which is a drawback of conventional polypropylene resin compositions. In addition to solving problems such as discoloration resistance and whitening resistance, it also has excellent workability, heat aging resistance, heat resistance, rust resistance, and well-balanced mechanical properties such as impact strength and bending strength. So, of course, the application of food containers,
Since it can also be used for household containers, clothes cases, seal containers, etc., it has high industrial utility value.

Continuation of front page (51) Int.Cl. ⁷ identification code FI C08L 23:04) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 53/00 C08K 5/13 C08K 5/49

Claims (2)

(57) [Claims] 1. (A) Propylene / ethylene block copolymer 50 to 90% by weight (B) Propylene / ethylene random copolymer 5 to 45% by weight (C) High density polyethylene having a density of 0.94 g / cm ³ or more A whitening polypropylene resin composition having excellent discoloration resistance, characterized in that 100 parts by weight of a resin component containing 5 to 45% by weight of a resin is mixed with at least the following additive components (D) to (F). object. (D) Organophosphorus antioxidant 0.01 to 0.5 parts by weight (E) Hindered phenolic antioxidant 0.01 to 0.1 parts by weight (F) Acid absorbent 0.02 to 0.3 Parts by weight 2. The melt flow rate of the (A) propylene / ethylene block copolymer is 4 to 60 g / 10 min., The ethylene content is 5 to 20% by weight, and the intrinsic viscosity of the ethylene / propylene copolymer part is 1.5 to 8 dl. / G, the melt flow rate of the (B) propylene / ethylene random copolymer is 6 to 50 g / 10 min., And the ethylene content is 1 to 10% by weight.
And (C) the high-density polyethylene having a density of 0.94 g / cm ³ or more has a melt flow rate of 0.2 to 25 g / 10 mi.
The whitening polypropylene resin composition having excellent discoloration resistance according to claim 1, characterized in that it is n.