JPS646654B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ethylene/α-olefin copolymer composition suitable for water-cooled inflation film molding, having excellent blocking resistance and transparency. A copolymer of ethylene and α-olefin called linear low-density polyethylene (L-LDPE) is different from conventional high-pressure low-density polyethylene (HPPE).
It has excellent mechanical strength (tensile strength, tear strength, impact strength, etc.), heat resistance, stress crack resistance, optical properties, and heat sealability as a film, making it suitable as a material for inflation films. be. On the other hand, as means for improving the transparency of blown films, a two-stage cooling method using air cooling, a water cooling method, etc. are known. However, in general, when the transparency of a film is improved by the above-mentioned forming means,
Blocking resistance tends to decrease, and especially in inflation film molding, there is a risk that the film cannot be opened after molding. Therefore, in general, metal soaps such as calcium stearate and zinc stearate, fatty acids such as stearic acid and palmitic acid, acid amides such as stearylamide, oleylamide, and palmitylamide, oleic acid monoglyceride, butyl stearate, and stearic acid monoglyceride are used. Various lubricants such as fatty acid esters, other higher alcohols, liquid paraffin, wax, silicone, and inorganic substances such as silica are added to prevent blocking. However, conventional additives mainly exert their anti-blocking effect by oozing out onto the surface of the resin, so if they are used in large quantities, they tend to contaminate the packaged object, make the film surface cloudy, and reduce transparency. It was hot. The present inventors investigated the prevention of blocking in ethylene/α-olefin copolymer films and found that by adding a specific high-density polyethylene, it was possible to prevent blocking without impairing transparency. It was found that there was no risk of the agent oozing out, and the present invention was achieved. That is, the present invention has a melt index MI ₂ of 0.5 to 3 g/10 min at a load of 2160 g, and a density of
0.910 to 0.940g/cm ³ , X-ray crystallinity
Copolymer of ethylene and α-olefin having 4 to 20 carbon atoms (A) with a melting point of 40 to 70% and a melting point of 115 to 130°C: 60 to 95% by weight and melt index at a load of 2160 g at a load of 2160 g Ratio of melt index MI ₁₀ to the above MI ₂ when MI ₂ is 0.1 to 32g/10min and load is 10Kg
MI ₁₀ /MI ₂ 5 to 18 and density 0.945 to 18
0.970g/ ^cm3 high density polyethylene (B): 5 or
The present invention provides an ethylene/α-olefin copolymer composition for forming a water-cooled inflation film, which has excellent blocking resistance and transparency, and is characterized by comprising 40% by weight of the following. In the ethylene/α-olefin copolymer (A) used in the present invention, examples of α-olefins having 4 to 20 carbon atoms copolymerized with ethylene include 1-
Butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene,
Examples include 1-tetradecene, 1-octadecene, or a mixture of at least two thereof. Among these, copolymers using α-olefins having 6 to 18 carbon atoms are particularly preferred because they have excellent impact resistance, tear resistance, and the like. MI ₂ of ethylene/α-olefin copolymer (A) is
It is in the range of 0.5 to 3g/10min. MI ₂
If the MI 2 is less than 0.5 g/10 min, the melt viscosity is high and the moldability is poor, and if the MI ₂ is more than 3.0 g/10 min, the melt tension is so small that water-cooled inflation films cannot be formed. In addition, in the present invention
MI ₂ is a value measured by the method of ASTM D1238;E. The density of the ethylene/α-olefin copolymer (A) is in the range of 0.910 to 0.940 g/cm ³ . If the density is less than 0.910g/ ^cm3 , the film will be too soft and sticky, and high-density polyethylene (described later)
Addition of (B) does not improve blocking resistance. Anything over 0.940g/ ^cm3 has high rigidity;
Furthermore, transparency is also reduced, which is not preferable. Note that the density in the present invention is a value measured by the method of ASTM D1505. Ethylene/α-olefin copolymer
The degree of crystallinity measured by X-rays in (A) is correlated with density,
A range of 40 to 70%, particularly 45 to 60% is preferred. If the degree of crystallinity exceeds 70%, transparency will decrease, and if it is less than 40%, mechanical strength will be poor. The melting point of the ethylene/α-olefin copolymer (A) is one or more, often two or more, determined from the endothermic curve of a differential scanning calorimeter (DSC) at a heating rate of 10°C/min. This is the highest temperature among three sharp endothermic peaks. and copolymer
(A) preferably has a melting point in the range of 115°C to 130°C, particularly 115°C to 125°C. Those with a melting point of less than 115°C have poor heat resistance, and those with a melting point of over 130°C have poor transparency and low-temperature heat sealability. If the ethylene/α-olefin copolymer (A) used in the present invention is a copolymer with the above properties, a blown film with excellent mechanical properties such as impact resistance and tear resistance can be obtained. A polymer having a molecular weight distribution (weight average molecular weight/number average molecular weight) of preferably 6 or less, particularly preferably 4 or less is preferable because a blown film with further excellent transparency can be obtained. The molecular weight distribution is a value determined by determining a molecular weight distribution curve using a gempermeation chromatograph and calculating the weight average molecular weight and number average molecular weight by the universal calibration method using polystyrene as a standard. The copolymer (A) having the above properties used in the present invention is produced by using a transition metal catalyst, for example, a catalyst consisting of a highly active titanium catalyst component formed from a magnesium compound and a titanium compound, and an organoaluminium compound, and by a so-called medium-low pressure method. Therefore, it can be obtained by polymerizing ethylene and α-olefin in a ratio that provides the required density. In order to obtain a desired melt index, a molecular weight regulator such as hydrogen may be used. Polymerization is slurry polymerization, gas phase polymerization,
It can be carried out by various methods such as high temperature solution polymerization. In the present invention, the high density polyethylene (B) to be mixed with the ethylene/α-olefin copolymer (A) has an MI ₂ of 0.1 to 32 g/10 min, preferably 0.5.
to 20 g/cm ³ , MI ₁₀ /MI ₂ of 5 to 18, preferably 7 to 15, and density of 0.945 to 0.970.
g/cm ³ range. MI ₂ is 0.1g/10min
If the composition is made into a film, the film will have fish eyes and will have poor moldability. If the MI ₂ exceeds 32 g/10 min, the moldability is poor and the impact resistance of the composition is reduced.
If MI ₁₀ /MI ₂ is less than 5, the moldability of the composition will be reduced, and if it exceeds 18, the transparency of the film will be reduced. If the density is less than 0.945 g/cm ³ , there is no anti-blocking effect. The ethylene/α-olefin copolymer composition (hereinafter sometimes abbreviated as composition) for forming a water-cooled blown film of the present invention is the ethylene/α-olefin copolymer composition (hereinafter sometimes abbreviated as “composition”).
α-olefin copolymer (A) and high-density polyethylene
(B) and 95/5 to 60/40 (wt%), preferably
It is a mixture of 90/10 to 70/30 (weight%). If the amount of high-density polyethylene (B) added is less than 5% by weight, there will be no anti-blocking effect, and if it exceeds 40% by weight, transparency will decrease, and low-temperature heat sealability, which is a characteristic of ethylene/α-olefin copolymer, will occur. , there is a risk that heat-sealing performance such as hot-tack properties may be impaired. In order to obtain the ethylene/α-olefin copolymer composition, the ethylene/α-olefin copolymer (A) and high-density polyethylene (B) are mixed within the above range using various known methods such as a V-blender or a tumbler. Method of mixing with a blender, Henschel mixer, ribbon blender, etc., followed by a single screw extruder,
A method of kneading and granulating with a multi-screw extruder or the like, or a method of melt-kneading and granulating with a kneader, Banbury mixer, etc. can be adopted. The composition of the present invention may contain conventional additives such as weathering stabilizers, heat stabilizers, antistatic agents, antifogging agents, pigments, dyes, nucleating agents, rust preventives, antiblocking agents, and small amounts of lubricants and antiblocking agents. Various compounding agents added to the polyolefin may be blended within the range that does not impair the purpose of the present invention. In addition, high pressure low density polyethylene,
Ethylene/vinyl acetate copolymer, amorphous or low crystalline ethylene/propylene or ethylene/1-butene copolymer, etc. may be added. Since the composition of the present invention has excellent blocking resistance, it is suitable for methods of imparting transparency by rapid cooling methods such as water-cooled inflation film molding. The blown film made from the composition of the present invention has excellent blocking resistance, has good opening properties, does not seep out of the antiblocking agent, and has excellent transparency, which is a characteristic of the ethylene/α-olefin copolymer (A). Since it has impact strength, tear strength, and heat sealing performance, it is suitable as a single film for various packaging films such as rice cracker snacks, agricultural foods, livestock foods, marine foods, and textile packaging. It can be used as the above-mentioned packaging film as a multilayer film with two or more layers using polypropylene, high-density polyethylene, nylon, polyester, cellophane, ethylene/vinyl alcohol copolymer, polyvinylidene chloride, etc. as the inner layer and the outer layer. . Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way unless the gist of the invention is exceeded. Example 1 _MI2 : 2.5g/10min, density: 0.933g/ ^cm3 ,
Linear crystallinity: 57.9%, melting point 125℃ (122℃,
(with a peak at 114℃) and molecular weight distribution: 2.8 ethylene/4-methyl-1-pentene copolymer (hereinafter abbreviated as EMP) 80% by weight, MI ₂ : 13.0g/
10 min, MI ₁₀ / MI ₂ : 9.6 and high density polyethylene (hereinafter abbreviated as HDPE) with a density of 0.965 g/cm ³ 20
Silica 10% by weight and as anti-blocking agent
After mixing 1% by weight masterbatch with a concentration of 1% by weight in a Henschel mixer, it was mixed with a 40mmφ extruder (set temperature:
230°C) and extruded through a 100mmφ circular die (die lip: 0.8mm, temperature set at 210°C) to obtain an inflation film with a fold width of 160mm and a thickness of 40μ. Next, the performance of the film was evaluated by the following method. Haze (%): ASTM D1003 Gloss (%): ASTM D523 Film appearance (visual observation): Defects in appearance due to frequent gel formation and poor compatibility were checked, and good was rated as ○ and bad as ×. Blocking (BL: (g/cm): ASTM D1893 Impact strength (FI: Kg cm/cm): ASTM D3420 The results are shown in Table 1. Examples 2 to 4 Instead of HDPE used in Example 1 _MI2 :
5.5g/10min, MI ₁₀ / MI ₂ : 9.4 and density 0.968
g/ ^cm3 high-density polyethylene (hereinafter referred to as HDPE), _MI2 : 1.1g/10min, _MI10 / _MI2 : 9.3 and high-density polyethylene (hereinafter referred to as HDPE) with a density of 0.954g/ ^cm3.
HDPE-) and MI ₂ : 0.9g/10min,
The same procedure as in Example 1 was carried out except that high-density polyethylene (hereinafter abbreviated as HDPE-) having MI ₁₀ /MI ₂ :8.7 and density 0.954 g/cm ³ was used. The results are shown in Table 1. Comparative Examples 1 to 4 MI ₂ instead of HDPE used in Example 1:
0.4g/10min, MI ₁₀ / MI ₂ : 19.0 and density 0.958
g/cm ³ high-density polyethylene (hereinafter abbreviated as HDPE), MI ₂ : 0.04 g/10 min, MI ₁₀ / MI ₂ : 28.0
and high-density polyethylene (hereinafter abbreviated as HDPE) with a density of 0.956 g/cm ³ and a melt index of 8.5.
g/10min (ASTM D1238, L) polypropylene (trade name: Mitsui Petrochemical Polypropylene F630, manufactured by Mitsui Petrochemical Industries, hereinafter abbreviated as PP) and MI ₂ :
The same procedure as in Example 1 was conducted except that 3.3 g/10 min high-pressure low density polyethylene (trade name: Mirason NEO-23H, manufactured by Mitsui Polychemicals, hereinafter abbreviated as LDPE) was used. The results are shown in Table 1. Reference Examples 1 and 2 Same as Example 1 except that EMP used in Example 1 and PP used in Comparative Example 3 were used alone instead of the composition of EMP and HDPE used in Example 1. The results obtained in the same manner are shown in Table 1.
However, EMP does not contain silica masterbatch, an anti-blocking agent. Example 5 The same procedure as in Example 1 was carried out without adding silica masterbatch as an anti-blocking agent to the EMP and HDPE composition used in Example 1.
The results are shown in Table 1. Comparative Example 5 EMP- instead of EMP- used in Reference Example 1
The same procedure as in Example 1 was conducted except that a composition containing 4% by weight of the silica masterbatch used in Example 1 as an antiblocking agent was used. The results are shown in Table 1. With only silica master batch,
In order to obtain the same low blocking value as when HDPE is added, it is necessary to increase the amount of silica masterbatch as described above, and as a result, as shown in Table 1, the degree of haze is lower than in Example 5. I understand. 【table】

Claims (1)

[Claims] 1. Melt index MI ₂ at a load of 2160 g
0.5 to 3g/10min, density 0.910 to 0.940
g/cm ³ , a copolymer of ethylene and an α-olefin having 4 to 20 carbon atoms (A) having a crystallinity of 40 to 70% according to X-rays and a melting point of 115 to 130°C: 60 to 70%
Melt index MI ₂ at 95% by weight and 2160g load is 0.1
High-density polyethylene (B) with a melt index MI ₁₀ to MI ₂ ratio MI ₁₀ /MI ₂ of 5 to 18 and a density of 0.945 to 0.970 g/cm ³ at a load of 10 kg to 32 g/10 min: 5 to 40% by weight of an ethylene/α-olefin copolymer composition for forming a water-cooled inflation film.