JP2000178404A - Propylene resin composition and use thereof - Google Patents

Abstract

(57) [Problem] To provide a resin composition having an excellent balance between rigidity and impact resistance and having high slidability, and a molded article thereof. SOLUTION: The melt flow rate is 4 to 50.
(G / 10 minutes), 85 to 95 parts by weight of an ethylene-propylene block copolymer having an ethylene content of 6 to 15% by weight, and a melt flow rate of 400 to 1200.
(G / 10 minutes) of a propylene homopolymer or 5 to 15 parts by weight of a random copolymer. Further, when a nucleating agent such as an organic phosphate metal salt is added to the composition, the effect is further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a propylene resin composition, a food container comprising the composition, and a container cap. More specifically, the present invention relates to a propylene resin composition having an excellent balance between rigidity and impact resistance and excellent slidability, and a food container and a cap using the same.

[0002]

BACKGROUND OF THE INVENTION In general, propylene resin has excellent chemical and physical properties and has excellent moldability, so that it is widely used in the production of molded articles such as food containers, medical containers, caps, and automobile parts. Have been. It is desirable that resins for these applications have high rigidity, high impact resistance, and high moldability, but it is difficult to uniformly adjust all performances to target levels.

Further, when a propylene resin molded product is smoothly moved and transported on a final product production line, the same slidability as a high-density polyethylene resin molded product is required. The slidability is not sufficient because the coefficient of kinetic friction against metal is high.

Therefore, in order to improve the sliding properties, fatty acid amides generally referred to as propylene resin such as stearylamide and erucylamide, fatty acid monoglyceride, fatty acid monoethanolamine, and fatty acid monoglyceride generally referred to as antistatic agents.
Compounds such as fatty acid diethanolamine, fatty acid diethanolamide, and fatty alcohol are blended to reduce the dynamic friction coefficient. However, since these compounds themselves have an odor, the odor migrates to the contents through the molded article, and since these lubricants are hydrophilic, foaming occurs when the contents are liquid. Therefore, it is not preferable as a molded article particularly for food use.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems associated with the prior art, and has an excellent balance between rigidity and impact resistance and improved slidability. It is intended to provide a propylene resin composition and a molded article using the same.

[0006]

That is, the present invention provides:
(A) Ethylene having a melt flow rate of 4 to 50 (g / 10 minutes) and an ethylene content of 6 to 15 (% by weight)
85 to 95 parts by weight of a propylene block copolymer,
(B) The melt flow rate is 400 to 1200 (g / 1
0 minutes) and 5 to 15 parts by weight of a propylene homopolymer or a random copolymer.

In the present invention, a nucleating agent is further added to the propylene resin composition, and a total amount of (A) an ethylene-propylene block copolymer and (B) a propylene homopolymer or a random copolymer is 100 parts by weight. For 0.
Regarding the propylene resin composition containing 0.05 to 0.4 parts by weight, the nucleating agent is preferably an organic metal phosphate salt.

Further, the present invention relates to a food container and a food container cap formed from the propylene resin composition.

[0009]

Next, the present invention will be described in detail. The propylene resin composition according to the present invention comprises (A) an ethylene-propylene block copolymer, (B) a propylene homopolymer or a random copolymer, and, if necessary, (C) a nucleating agent.

(A) Ethylene-propylene block copolymer
The united ethylene-propylene block copolymer is a polymer basically composed of a polypropylene segment and an ethylene-propylene copolymer segment, and may further contain a polyethylene segment as necessary. The polypropylene segment is crystalline and mainly contributes to imparting mechanical strength such as rigidity of the block copolymer. The ethylene / propylene copolymer segment has rubber-like properties and forms the rubber portion of the block copolymer, contributing to imparting impact resistance.

The polypropylene segment accounts for 80 to 99, preferably 82 to 88% by weight in the block copolymer, and the ethylene / propylene copolymer segment accounts for 1 to 20, preferably 12 to 18% by weight. hand,
Within this range, it is suitable for improving various mechanical properties of the resin composition. If necessary, the coexisting polyethylene segment is preferably in the range of 0 to 20% by weight.

The ethylene content in the block copolymer is from 6 to 15, preferably from 7 to 9 (% by weight), and within this range, it is suitable for improving the impact resistance of the resin composition. . Melt flow rate of block copolymer (MF
R) is 230 ° C. according to ASTM D-1238,
2. The value measured under a load of 16 kg is 4 to 50, preferably 4 to 12 (g / 10 minutes), and within this range, a resin composition suitable for mechanical strength and moldability is provided. .

[0013] Such a block copolymer is obtained by performing homopolymerization of propylene, then copolymerization of propylene and ethylene, and if necessary, homopolymerization of ethylene in the presence of an olefin stereoregular polymerization catalyst. It can be produced by employing a multi-stage polymerization method. Also,
It can also be produced by mechanically melt-kneading a propylene homopolymer, a copolymer of propylene and ethylene, and if necessary, an ethylene homopolymer.

(B) Propylene homopolymer or lander
The propylene polymer serving as the copolymer (B) component is preferably a propylene homopolymer, but a random copolymer can be used as long as the mechanical strength of the propylene resin composition is not reduced. Here, the random copolymer is a polymer obtained by copolymerizing propylene with another α-olefin of 10 mol% or less, preferably 1 mol% or less, particularly preferably 0.5 mol% or less of all monomer units. is there. Examples of other α-olefins include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene,
-Decene and the like.

The propylene homopolymer or random copolymer has a melt flow rate (MFR) of ASTM.
The value measured at 230 ° C. under a load of 2.16 kg according to D-1238 is 400 to 1200, preferably 600
８００800 (g / 10 minutes). Within this range,
Without sacrificing the mechanical strength of the resin composition, moldability can be improved and slidability can be improved. Such a propylene homopolymer or a random copolymer uses an olefin stereoregular polymerization catalyst,
By polymerizing propylene and, if necessary, other α-olefins while adjusting the molecular weight,
Can be manufactured.

Nucleating agent The propylene resin composition according to the present invention may optionally contain a nucleating agent, simply referred to as a nucleating agent. Examples of the nucleating agent that can be used include (a) a metal carboxylate such as aluminum p-tert-butylbenzoate;
(B) polyhydric alcohol derivatives such as dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol; (c) sodium-2,2-methylenebis (4,6
Metal salts of organic phosphoric acid esters such as -di-tert-butylphenyl) phosphate; (d) branched olefins such as 3-methyl-1-butene, 3,3-dimethyl-1-butene, 3-methyl-1- Examples thereof include a polymer nucleating agent such as a homopolymer or a copolymer such as pentene, 4-methyl-1-pentene and 3-methyl-1-pentene, and the like.

Among these, metal salts of organic phosphoric acid esters are preferred, and the addition thereof can achieve a good balance between the rigidity and impact resistance of the propylene resin composition and impart excellent sliding properties. As an organic phosphate metal salt, sodium-2,2- represented by the formula (1)
Examples thereof include methylene bis (4,6-di-tert-butylphenyl) phosphate and an aluminum compound represented by the formula (2). Particularly, the effect of the compound represented by the formula (1) is high.

[0018]

Embedded image ... (1) Here, t-Bu shows a tert-butyl group.

[0019]

Embedded image ..... (2)

In the formula (2), R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl,
Examples include groups such as butyl, isobutyl, tert-butyl, amyl, tert-amyl, hexyl, heptyl, octyl, nonyl, 2-ethylhexyl, and the like. X is an alkylene group, such as methylene, ethylene, and propylene.

Specifically, when X is a methylene group and R is
₁ is tert- butyl group, a compound of R ₂ is a methyl group, and X is a methylene group, compounds of R ₁ and R ₂ are tert- butyl group, and further X is a methylene group, R ₁ and R _Two
Can be exemplified as a compound having a tert-amyl group.

Propylene Resin Composition The resin composition according to the present invention comprises (A) an ethylene-propylene block copolymer of 85 to 95, preferably 90 to 95.
95 parts by weight, (B) 5 to 15, preferably 5 to 10 parts by weight of the propylene homopolymer or random copolymer. Within this range, a composition excellent in balance between rigidity and impact resistance of the propylene resin composition and excellent in slidability can be obtained.

Further, in the present invention, the nucleating agent is used in an amount of 0.05 to 0 with respect to 100 parts by weight of the total of (A) the ethylene-propylene block copolymer and (B) the propylene homopolymer or the random copolymer. .4, preferably 0.05
To 0.3, more preferably 0.1 to 0.3 parts by weight. Within this range, a composition having excellent balance between rigidity and impact resistance of the propylene resin composition and further excellent sliding properties can be obtained.

If necessary, the propylene resin composition may contain a phenolic, phosphorus-based or thioether-based antioxidant, neutralizer, light stabilizer, weather resistance stabilizer, flame retardant, pigment, dye, filler, etc. And the like can be blended as long as the object of the present invention is not impaired. In addition, a lubricant such as stearylamide or erucylamide can be added within a range of a compounding amount that does not generate odor, which is one object of the present invention.

The resin composition according to the present invention comprises (A) an ethylene-propylene block copolymer, (B) a propylene homopolymer or a random copolymer, and, if necessary, a nucleating agent and other additives. After mixing using a mixing machine such as a Henschel mixer, a V-blender, a ribbon blender, a tumbler blender, and the like in the mixing amount range described above, melt kneading with a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, or the like. Thus, a composition having a uniform composition can be obtained.

The propylene resin composition described above formed shapes bodies, injection molding, blow molding, using a molding means like extrusion, it is possible to produce various kinds of molded articles. These molded products have an excellent balance between rigidity and impact resistance, and are used in food, medical,
It can be used in a wide range of industrial fields such as the automobile parts field and the packaging field.

Particularly, it is suitable for use as a food container and its cap, and has high slidability, so that it can be smoothly used in a final product production line such as a content filling step and a packing body packing step. Can be moved and transported.

[0028]

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples. First, the resins and additives used in Examples and Comparative Examples will be described.

(A) Ethylene-propylene block copolymer; ethylene content: 7 wt%, melt flow rate (ASTM D-1238, 230 ° C., 2.16 kg load): 8 (g / 1
0 minutes). (B) Ethylene-propylene block copolymer; ethylene content 7 wt%, melt flow rate (ASTM D-
1238,230 ° C, 2.16kg load) 4 (g / 10min).

(C) Propylene homopolymer Melt flow rate is 800 (g / 10 minutes). (D) High density ethylene homopolymer Density (ASTM D-1505) is 0.956 (g / cm ³ ) and melt flow rate (ASTMD-1238, 190 ° C, 2.16 kg load) is 12
(G / 10 min).

(E) a phenolic antioxidant; tetrakis [methylene-3 (3,5-di-tert-butyl-4)
-Hydroxyphenyl) propionate] methane (F) phosphorus antioxidant; tris (2,4-di-tert-
(Butylphenol) phosphite (G) neutralizer; calcium stearate (H) neutralizer; hydrotalcite

(I) Nucleating agent 2,2-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate (J) lubricant; erucylamide (K) lubricant: stearylamide

Examples 1 to 3 The above-mentioned resins and additives were prepared in the proportions (parts by weight) shown in Table 1, and then uniformly mixed in a Henschel mixer. Then, using a CIM-50 high-speed twin-screw extruder manufactured by Nippon Steel Works, resin temperature 2
The mixture was melt-kneaded at 00 ° C., and the kneaded product was extruded to obtain pellets. Using the pellets, a 2 mm-thick sheet-shaped test piece was prepared by injection molding at a resin temperature of 200 ° C. and a mold temperature of 40 ° C.

Using the pellets and test pieces, various physical properties were examined by the following methods. (A) Melt flow rate (MFR); ASTM D-1238,2
30 ° C, 2.16kg load, unit (g / 10min). (B) Initial flexural modulus; 23 ° C., according to ASTM D-790. The unit is (MPa). (C) Izod impact strength: A notched test piece was used at 23 ° C. according to ASTM D-256. Units,
(J / m)

(D) Coefficient of static friction and coefficient of dynamic friction by slip test: 200 g of stainless steel, 23 ° C.
, In accordance with ASTM D-1894-75-C method. (E) Odor: 100 g of the pellet is put in a 500 ml closed glass bottle, and 100 ml of distilled water is poured. The bottom was immersed in a water bath at 90 ° C., opened after 1 hour, and immediately after that, the odor was judged by smell.

Comparative Examples 1 to 5 Pellets and test pieces were obtained in the same manner as in Example 1 except that the resins and additives described in Table 1 were used. Thereafter, a physical property test was performed, and the results are also shown in Table 1.

Examples 1 and 2 were systems in which no lubricant was added, and had a much lower dynamic friction coefficient than Comparative Example 5. In Example 3, the lubricant was added to the composition of Example 1 in a range where no odor was felt, and the dynamic friction coefficient was lower than that of Comparative Example 1 in which the same amount was added. Further, the dynamic friction coefficient of Example 3 reached the same level as the dynamic friction coefficient of the high-density ethylene resin molded product. In Comparative Examples 2 and 3, the type of the lubricant was changed, and the dynamic friction coefficient was reduced. However, the odor was strong and the resin was not suitable as a resin for food containers.

As is clear from Table 1, the resin compositions obtained in Examples 1 to 3 are balanced in rigidity and impact resistance as compared with Comparative Examples 1 to 3 and 5, and at the same time are low. It can be seen that it has a dynamic friction coefficient.

[0039]

According to the present invention, a resin having an excellent balance between rigidity and impact resistance is obtained by blending a highly flowable propylene homopolymer or random copolymer with an ethylene-propylene block copolymer. A composition could be obtained, and at the same time, the slidability could be improved.

Although the nucleating agent is usually blended to increase the transparency of the resin or sometimes to increase the rigidity, the resin composition of the present invention achieves an excellent balance between rigidity and impact resistance. At the same time, the slidability, which was unknown until now, could be improved at the same time.

Accordingly, molded articles obtained from the present resin composition are used in a wide range of industrial fields where high rigidity and impact resistance are required, and in particular, must be smoothly moved and transported on a production line. Suitable for use in food containers and their caps.

[0042]

[Table 1]

Claims (5)

[Claims] (A) a melt flow rate of 4 to 50 (g);
/ 10 min) and 85 to 95 parts by weight of an ethylene-propylene block copolymer having an ethylene content of 6 to 15 (% by weight), and (B) a melt flow rate of 400 to 1200.
(G / 10 minutes), comprising 5 to 15 parts by weight of a propylene homopolymer or a random copolymer. 2. The resin composition according to claim 1, further comprising a nucleating agent in a total amount of 100 parts by weight of (A) an ethylene-propylene block copolymer and (B) a propylene homopolymer or a random copolymer. In contrast, 0.05 to 0.4 parts by weight of a propylene resin composition. 3. The propylene resin composition according to claim 2, wherein the nucleating agent according to claim 2 is a metal salt of an organic phosphate. 4. A food container formed from the propylene resin composition according to claim 1. 5. A cap for a food container, which is formed from the propylene resin composition according to claim 1.