JPS60161442A - Polyolefin composition - Google Patents

Abstract

PURPOSE:The titled composition, obtained by blending a specific linear low- pressure processed polyethylene with a propylene polymer resin, having improved transparency, rigidity and moldability, and suitable for injection molding. CONSTITUTION:A polyolefin composition obtained by blending (A) 5-95pts.wt., preferably 20-80pts.wt. linear low-density polyethylene having 0.01-5g/10min melt flow rate (hereinafter abbreviated to MFR), 0.905-0.940g/cm<3> density, 10- 30 flow ratio (ratio between MFRs under 10kg load and 2.16kg load) and <=60sec time to reach 1/2 calorific value of the gross calorific value generated in the isothermal crystallization at a temperature expressed by the formula with (B) 95-5pts.wt., preferably 80-20pts.wt. propylene resin, e.g. propylene homopolymer or random or block copolymer with ethylene, having 2-100g/10min MFR.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polyolefin compositions with improved transparency, stiffness and moldability.

Linear low-density polyethylene has better resistance to environmental stress cracking (ESCR), heat resistance, cold resistance, and
Due to its excellent dimensional accuracy and gloss, it is expected to be used in many applications such as industrial parts, containers, and caps.

However, linear low-density polyethylene has the drawback that its transparency is greatly inferior, so in order to improve this, aliphatic and aromatic dicarboxylic acids or their anhydrides, amine salts, metal salts, aromatic Nucleating agents such as acid aluminum salts were tried, but none of them were effective, and even with dibenzylidene rubitol or its derivatives, which are said to be effective, the addition concentration is 0.2 weight 5 to achieve transparency. Although the above is necessary, at this high concentration, the characteristic odor of nucleating agents may cause food,
Not only is it unsuitable for applications such as cosmetics, but if the density is increased to the level of medium-density polyethylene in order to maintain high rigidity, which is one of the objectives of the present invention, the effect of adding a nucleating agent is lost.

Second, with linear low-density polyethylene, depending on various molding conditions such as the shape of the injection molded product, the shape of the gate, the molding temperature, and the injection pressure, delamination may occur at the gate or hinge part, which can significantly reduce the product value. It has the disadvantage of reducing This delamination may be observed not only in the vicinity of the gate, but also particularly in the transition area from a thick portion to a thin portion. In general, delamination often occurs in immiscible polymer blends, but delamination in a single system is unique to linear low-density polyethylene, and is more pronounced as the reeds and MFR decrease. Appearance near the gate and delamination in areas where the wall thickness of the molded product changes are both caused by a combination of various conditions such as the shape of the molded product, gate shape, molding temperature, and injection pressure.For example, if the molding temperature is high, υ, gate shape Although it is possible to solve this problem to some extent by devising the
The molding cycle may be sacrificed or the design may be restricted, so there is no fundamental solution.

Third, linear low-density polyethylene has a stiffness that is higher than that of high-pressure low-density polyethylene, but lower than that of medium-density or high-density polyethylene, and is problematic because it cannot be used in a wide range of applications.

Conventionally, increasing rigidity has usually been achieved by increasing density, but in this case there are disadvantages such as further deterioration of transparency and reduction in ESCR.

Fourth, linear low-density polyethylene has a disadvantage of poor mold release properties compared to high-pressure low-density polyethylene and medium-high density polyethylene. As a countermeasure against this problem, adding a slip agent may improve the problem to some extent, but it is not a fundamental solution, and products with complex shapes require time to take out, which poses a problem in terms of the molding cycle.

On the other hand, although propylene polymer resin has the features of high rigidity, high heat deformation resistance, and excellent ESCR, it has the drawback of poor impact resistance. - Blends of propylene rubbers have been used, but the former has the disadvantage that transparency is impaired, and the latter has a poor balance with rigidity.

The inventors of the present invention have conducted extensive studies on the serious problems, and have surprisingly found that these problems can be solved all at once by blending a specific linear low-pressure polyethylene and propylene polymer resin. I found it.

That is, the present invention has a melt flow rate (VFR) of 0
．． 01~5f/10min, density 0.905~0.940
t/al! , the flow ratio (ratio of IOKg load melt flow rate to 2.16 Kf load melt flow rate) is 10 to 30 and reaches 1/2 of the total heat amount generated in isothermal crystallization at a temperature expressed by the following formula l. A polyolefin composition comprising 5 to 95 parts by weight of linear low density polyethylene having a melt time of 60 seconds or less and 95 to 5 parts by weight of a propylene polymer resin having a melt rate of 2 to 100 f710 minutes.

Temperature ('K); 367.5 X density + 45.88 (formula 1) However, the density in the formula is 48
This is a value measured after punching out after a period of time (cooling rate: 25° C./min).

The linear low density polyethylene used in the present invention has an MFR (1
90℃) 0.01~5f/10min, density 0.905~
An ethylene polymer having a flow ratio of 0.940 f/cd, a flow ratio of 10 to 30, and a time to reach 172 of the total heat generated by isothermal crystallization at the temperature represented by the above formula 1, which is 60 seconds or less, Generally, ethylene and an α-olefin having 3 to 12 carbon atoms, preferably 3 to 8 carbon atoms, and particularly preferably 4 to 6 carbon atoms are copolymerized using a chromium-based catalyst by a gas phase method, a liquid phase method, a slurry method, or the like. Preferably, those obtained by The α-olefin content of this product is generally 2 to 20% by weight for α-olefins having 3 to 5 carbon atoms, and 2 to 20% by weight for α-olefins having 6 or more carbon atoms.
- For olefins, the content is 1 to 10% by weight, preferably from 4 to 15% by weight for α-olefins having 3 to 5 carbon atoms, and from 2 to 6% by weight for α-olefins having 6 or more carbon atoms.

Preferred linear low density polyethylene has a MFRo of 1 to 4.
f710 minutes, flow ratio 12-20, density o, 91
o -0.93s t/di and the above-mentioned heat amount arrival time is 40 or less.

The MFR of this linear low density polyethylene is 0.01f/1
If it is less than 0 minutes, flow marks are likely to occur due to insufficient flowability, and 5
When f/10 minutes is exceeded, low-temperature impact resistance is impaired. If the flow ratio is less than 10, the flowability and delamination are poor;
If it exceeds 0, shrinkage anisotropy will occur, which is not preferable. Density is o
If it is less than , 9 osr/-, it will be stiff (if it exceeds 0,940, transparency will be impaired. If the time to reach 1/2 heat amount exceeds 60 seconds, transparency will be impaired and the cooling time will also become longer.

Such methods for producing linear low density polyethylene are introduced, for example, in Japanese Patent Publications No. 47-21574, No. 47-16647, and No. 112891/1983. Even those obtained with Ziegler catalysts are partially crosslinked, etc.
In addition, those that have been subjected to deodorizing and decolorizing treatments, or those that have been polymerized with an improved catalyst can be used.

Furthermore, the propylene polymer resin used in the present invention has an MFR of
(230°C) 2-100 f 710 min, preferably 5
~80 f/10 min. MFR is 2f/
If it is less than 1 G, the fluidity of the composition is poor, and 100 f/
If the time exceeds 10 minutes, the low temperature impact resistance ratio becomes a problem. Suitable examples of this material include a propylene homopolymer, a random copolymer containing 10% by weight or less of ethylene, and a block copolymer containing 15% by weight or less of ethylene. In terms of rigidity, random copolymers with an ethylene content of 10% by weight or less have
Further, a block copolymer having an ethylene content of 15% by weight or less is selected from the viewpoint of transparency. More preferably, a random copolymer has an ethylene content of 2 to 6% by weight, and a block copolymer has an ethylene content of 5 to 8% by weight.
Preferably.

The comonomer copolymerized with propylene is generally ethylene, but ethylene-butene-propylene ternary random copolymers, ethylene-butene random copolymers and propylene block copolymers, or butene-propylene Also preferred are block copolymers of random copolymers and ethylene. In this case, the butene content in the case of a random copolymer of ethylene-butene-propylene is 10% by weight or less, and in the case of a block copolymer of ethylene-butene random copolymer and propylene, the total content of ethylene and butene is 10% by weight or less. The total content of ethylene and butene is preferably 15% by weight or less, and in the case of a block copolymer of propylene-butene random copolymer and ethylene, the butene content is preferably 20% by weight or less based on the propylene content.

The blend ratio of linear low density polyethylene and propylene polymer resin is 95-5 parts by weight to 5-95 parts by weight, preferably 80-20 parts by weight to 20-80 parts by weight. If the blending ratio of the propylene polymer resin is less than 5 parts by weight, no improvement in rigidity will be observed, and no improvement in mold releasability will be achieved. In addition, it is not preferable for dogs to use 95 parts by weight, especially when propylene is used alone or as a random copolymer, since the cold resistance is inferior.

In the present invention, in addition to the essential ingredients, other additional ingredients such as neutralizing agents, dispersants, antioxidants, weathering improvers, antistatic agents, pigments, fillers, etc. may be blended within a range that does not inhibit the expression of effects. Can be done.

The compositions of the present invention are made using known cross-mixing methods, such as roll, Prabender Plastograph, Banbury Mixer 1 extruders, and the like. In particular, those containing 30 to 70 parts by weight of linear low-density polyethylene may be triblended and subjected to direct injection molding.

In addition to the above-mentioned transparency, the composition of the present invention has improved appearance, which is a problem unique to injection molding, and in that sense, it can be said to be particularly suitable as a composition for injection molding.

EXAMPLE 0.2,6-di-t-butyl-p-cresol was added to the linear low-density polyethylene and propylene polymers shown in Table 1.
Add 05 parts by weight and mix with a Henschel mixer,
■Pelletize at 530℃ using a diameter extruder, and use Toshiba l890
Injection molded samples were made using B injection molding machine and evaluated. The results are shown in Table 1.

The MFR (measured at 190°C) of the compositions of Examples 1 to 3 was 0.
9-2.8 f Despite being as low as 710 minutes, the spiral flow was higher than MFR5 and 1 of the compositions of Comparative Examples 1 and 2.
0 general-purpose linear low-density polyethylene, and is easy to mold. In addition, the materials of the Examples had no problems with regard to their llAm properties and could be molded. This is significant when compared with the fact that layer peeling at the gate portion was not observed in any of the Examples and was not resolved in Comparative Examples 1 and 2 even though the MFR was increased. Rigidity is 2000~9900Kg/
Even though it can be changed widely with CD, the height is 30-55.
%, which is extremely excellent. Comparative Example 3, in which the same type of polypropylene was blended with a GR8N7049 base having substantially the same MFR and density as those of the example but different flow ratio and 1/2 heat arrival time, had a short spiral flow and poor haze. Furthermore, although the composition of Example 6 significantly increased the MFR, there was no decrease in -j''EscH. Generally, the ESCR decreases as in the 20 comparative examples. It has also been found that the composition of the invention has utility as a thin transparent material.

The evaluation method is as follows.

(1) MFR: JIS-7210 (2,16
load) 190℃ when the linear low density polyethylene is 50% more by weight or more, 2 when the propylene polymer is the majority by weight
30°C (2) Density: JIS-7112, however, specimens were made using JIS-6760 to create a 2-inch thick press sheet.
After 48 hours without annealing (cooling rate 1ii1-
25°C/min) by punching.

(3) Flow ratio: MFR at 10Kf load and 2.1
Ratio of MFR at 6 ceramic loads (4) Time to reach 1/2 of the total heat generated by isothermal crystallization at the temperature expressed by the above formula 1: Using a Perkin-Erlenmeyer DSC, sample 20 (2) is held at 160° C. for 3 minutes to melt, and then cooled to a predetermined isothermal crystallization temperature at a cooling rate of 80° C./min. Heat generation is observed during crystallization and continues until the end of crystallization. The time taken to reach V2 of the total calorific value at this time is adopted.

However, the density in the above formula 1 is 4 mm without annealing a 2 mm thick press sheet prepared according to JIS-6760.
This is the value measured after punching out the sample after 8 hours (cooling rate: 25° C./min).

(5) Layer peeling @: O, S ■ thick film gate mold, tooxtooxt each ■ sheet at temperature [200℃,
Injection molding was performed under the conditions of injection pressure sso r4/c+J, cooling water temperature at room temperature, and cooling for 20 seconds, and observation was made at the gate. No peeling was observed as ○, and peeling was observed on a part of the gate as Δ. , and those seen on the same surface were marked as ×.

(6) Haze: ASTM-DI Go 3-52 (
1 sheet) (7) ESCR: ASTM-D1693 (Liponox 75 vo1%, 2 sheet TD direction) + 8) 2 viral flow: semicircular square mold, temperature 260°C,
Injection pressure 5soKp/d (9) Mold releasability: Qualitative mutual comparison Stiffness: JIS-720:l (2m thick injection sheet) (Margins below)

Claims (1)

[Claims] Melt flow rate 0.01 to 5 f/10 min, density 0.
905 to θ-94097d, flow ratio (ratio of 10-load melt flow rate to 2.16Kf load melt flow rate) 10 to 30, and the following formula! 5 to 95 parts by weight of linear low-density polyethylene whose heating time is 60 seconds or less to reach 1/2 of the total amount of heat generated by isothermal crystallization at a temperature expressed by A polyolefin composition comprising 95 to 5 parts by weight of a body resin. 1+[('K) = a a 7.5)l[+4
s, s s (Formula t) However, the density in the formula is measured by punching out a 2-inch thick press sheet prepared according to JIS-6760 after 48 hours without annealing (cooling rate 25°C/min). This is the value.