JPH11279342A - Resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene resin compsn. which exhibits an excellent processibility, while reducing the load on an extruder, when formed into film and which gives a film with reduced fish eyes. SOLUTION: This compsn. comprises 100 pts.wt. polyethylene having a density in the range of 0.880-0.950 g/cm<3> and a melt strength (MS) at 190 deg.C of 30-300 mN and 0.01-5 pts.wt. polyethylene wax having a ratio (Mw/Mn) of wt. average mol.wt. (Mw) to number average mol.wt. (Mn), in the mol.wt. distribution, of 3 or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a resin composition characterized by having excellent processability and reducing the load on an extruder, and at the same time reducing fish eyes in a molded film, in film processing of a polyethylene resin. It is about.

[0002]

2. Description of the Related Art A plastic film widely used as a packaging material is formed by various methods such as an inflation molding method, a T-die casting molding method, and an extrusion laminating molding method. These films include a single-layer film and a laminated (laminated) film composed of a plurality of films, and a large amount of polyethylene is used as a raw material.

[0003] In forming a film by each molding method, the raw material polyethylene has an appropriate melt strength (Melt Street).
ngth, hereinafter abbreviated as MS) is one of the important conditions. Generally, when the resin fluidity at the time of molding is to be increased by the raw material resin, the MS is reduced, which seriously impairs the film forming property. That is, in the inflation molding method, a product defect occurs due to a decrease in bubble stability, and in the T-die cast molding method or the extrusion laminate molding method, a product loss increases due to an increase in neck-in.

Recently, in order to improve film productivity,
High-speed processing aptitude is required. However, in order to process the film at high speed, it is necessary to increase the discharge amount of the molten polyethylene extruded from the molding machine. Attempts to increase the discharge rate while maintaining the same polyethylene as in the prior art have the problem that the motor load of the extruder and the pressure of the molten resin increase, causing overloading of the molding machine. Further, if polyethylene having a high fluidity is used to avoid overloading of the molding machine, there is a problem that the above-mentioned problems occur due to a decrease in MS. Furthermore, when a technique of increasing the MS by appropriately subjecting a highly fluid polyethylene to a cross-linking reaction is used, there is a problem that fish eyes (FE) when formed into a film are increased and the appearance of the film is impaired.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resin composition which has excellent workability and reduces the load on an extruder, and at the same time reduces fish eyes in a formed film, in a film forming process of polyethylene. It is to provide.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by adding a small amount of a specific polyethylene wax to a specific polyethylene, it has been found that the suitability of the film for high-speed processing is improved. An excellent resin composition was found, and the present invention was completed.

That is, according to the present invention, the density is from 0.880 to
Ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) in 100 parts by weight and molecular weight distribution of polyethylene having a melt strength (MS) at 190 ° C. in the range of 0.950 g / cm ^{3 and} a range of ³⁰ to 300 mN. (Mw / M
polyethylene wax having n) in the range of 3 or less.
The present invention relates to a resin composition comprising from 0.01 to 5 parts by weight.

Hereinafter, the present invention will be described in detail.

[Polyethylene] As the method for producing polyethylene used in the present invention, ethylene alone or a mixture of ethylene and a comonomer such as vinyl acetate or α-olefin is subjected to radical polymerization of oxygen or an organic peroxide. Using an initiator, high temperature, high pressure method to polymerize at high pressure, medium pressure method to polymerize at medium polymerization pressure using metal oxide catalyst, low pressure method to polymerize at low pressure using Ziegler catalyst,
Any of these methods may be used.

The density of the polyethylene used in the present invention is 0.880 to 0.950 g / cm ³ , preferably 0.890 to 0.940 g / cm ³ , more preferably 0.900 to 0.935 g / cm ^3. Range. If the density is less than 0.880 g / cm ³ , or 0.95
If it exceeds 0 g / cm ³ , the film processability of the resin composition is inferior, which is not preferable.

The polyethylene 190 used in the present invention.
The melt strength at 30 ° C. (MS) is 30 to 300 mN, preferably 35 to 200 mN, more preferably 40 to 10 mN.
The range is 0 mN. Melt strength at 190 ° C (M
When S) is less than 30 mN or more than 300 mN, the film processability of the resin composition is inferior and is not preferred.

As the polyethylene used in the present invention, a polyethylene having a low MS increased by a crosslinking reaction is preferable. This is due to the fact that by appropriately utilizing the crosslinking reaction for polyethylene having high fluidity (ie, low MS), the decrease in resin fluidity is kept small (low extruder load) and the MS is increased to the required range. This is because it is relatively easy to do. In the cross-linking reaction, a method in which a radical generator is thermally decomposed and reacted is generally used.

The radical generator used in the present invention includes:
Organic peroxides such as hydroperoxides, dialkyl peroxides and peroxyesters are preferred. Among these organic peroxides, those having a decomposition temperature of 90 ° C. or higher for obtaining a half-life of 1 minute are preferable.

As specific examples, dicumyl peroxide, t-butyl hydroperoxide, 1,3-bis (t-butylperoxyisopropyl) benzene, di-t-butyl peroxide, 2,5-di ( t-butylperoxy) hexane, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne 3,2,5-dimethyl-2,5-di (t-butylperoxy) hexyne (Butylperoxy) hexane, di-t-butylperoxyphthalate and the like.

Although any method may be used for the reaction, specific examples include the following methods.

1) After the polymerization of polyethylene is completed, in a step of granulating (pelletizing) with an extruder, a radical generator is simultaneously extruded to cause a melt reaction.

2) A masterbatch containing a large amount of a radical generator is prepared in advance, and polyethylene pellets and the masterbatch are blended, melt-kneaded, and reacted.

The amount of the radical generator to be added is not particularly limited, but is preferably in the range of 1 to 100 ppm depending on the type of the polyethylene and the radical generator to be used because the effect of improving the processability is higher.

The temperature for the reaction is not particularly limited, but may vary depending on the type of polyethylene and radical generator used.
It is preferable that the temperature is in the range of 300 to 300 ° C. because the effect of improving the workability is higher.

The time for the reaction is not particularly limited, but depends on the type of polyethylene and radical generator used.
A range of 0 minutes is preferable because the effect of improving workability is higher. When the crosslinking reaction as described above is performed, it is preferable to add an antioxidant after the reaction. As the antioxidant, a phenolic antioxidant and a phosphorus antioxidant are used. Examples of the phenolic antioxidants include monophenolic, thiobisphenolic, and trisphenolic antioxidants. More specifically,
2,4-bis (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5
Triazine (commercially available from Nippon Ciba Geigy Co., Ltd. under the trade name Irganox 565), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (trade name from Nippon Ciba Geigy Co., Ltd.) Commercially available under the name Irganox 1076), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl)
-Isocyanurate (sold by Nippon Ciba Geigy KK under the trade name Irganox 3114) and the like, and these are used alone or as a mixture. Specific examples of the phosphorus-based antioxidant include tris (2,4-di-t-butylphenyl) phosphite (trade name Irgafos 16 from Nippon Ciba Geigy Co., Ltd.).
8), tetrakis (2,4-di-
t-butylphenyl) -4,4'-biphenylenephosphonite (commercially available from Nippon Ciba Geigy Co., Ltd. under the trade name Irgafos P-EPQFF), and tris (nonylphenyl) phosphite (commercially available from Asahi Denka Co., Ltd.) Commercially available under the name MARK1178), and these are used alone or as a mixture.

[Polyethylene Wax] In the present invention,
A polyethylene wax is added to the above polyethylene and melt-kneaded.

Examples of the polyethylene wax used in the present invention include a polymerization type wax obtained by polymerization of ethylene and a pyrolysis type wax obtained by pyrolyzing low density polyethylene. Among these waxes, those having a low density and a high melting point are preferred from the viewpoint of melt kneading and stickiness.

The molecular weight distribution of the polyethylene wax used in the present invention is such that the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) by gel permeation chromatography (GPC) is 3 or less. , Preferably 2.9 or less. A wax having Mw / Mn of more than 3 is not preferable because it causes surface stickiness when the resin composition is formed into a film.

The polyethylene wax is added in an amount of 0.01 to 5 parts by weight, preferably 0.05 to 4 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of polyethylene.
The range is 3 parts by weight. If the amount of the polyethylene wax is less than 0.01 part by weight or more than 5 parts by weight, the effect of the present invention is not sufficiently exerted, which is not preferable.

[Ethylene / α-olefin copolymer] The resin composition of the present invention also includes a composition obtained by further mixing an ethylene / α-olefin copolymer with the above composition.

The ethylene / α-olefin copolymer used in the present invention is obtained by copolymerizing ethylene and α-olefin in the presence of a Ziegler catalyst, a chromium oxide catalyst, a molybdenum oxide catalyst, a vanadium catalyst, a metallocene catalyst or the like. It can be obtained by As the catalyst, a catalyst which gives a copolymer having a uniform composition distribution or the like is preferable, and is, for example, a metallocene catalyst.

The α-olefin which is a comonomer of the copolymer is represented by the general formula R—CH ＝ CH ₂ (wherein R represents 1 carbon atom).
The above alkyl group is shown), and specific examples thereof include propylene, 1-butene, 1-pentene,
1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene,
Octadecene and the like. Among these α-olefins, those having 5 to 10 carbon atoms, which are excellent in tensile strength, tear strength, impact strength, heat seal strength and the like in a film sample after forming a copolymer, are particularly preferable, and 1-hexene and 1-hexene are particularly preferable. -Heptene, 1-octene, 4-methyl-1-pentene. The copolymer is obtained by copolymerizing at least one of these α-olefins with ethylene. Specifically, an ethylene / 1-hexene copolymer, an ethylene / 1-heptene copolymer, an ethylene / 1
Examples thereof include a 1-octene copolymer, an ethylene-4-methyl-1-pentene copolymer, and an ethylene / propylene / 1-hexene terpolymer.

By adding the ethylene / α-olefin copolymer, the mechanical strength of the resin composition is greatly improved, and it is possible to obtain a higher strength film product or the like.

The amount of the ethylene / α-olefin copolymer to be added is in the range of 1 to 2,000 parts by weight based on 100 parts by weight of the composition comprising polyethylene and polyethylene wax. When the addition amount is less than 1 part by weight, the effect of adding the ethylene / α-olefin copolymer does not appear, and when it exceeds 2000 parts by weight, the effect of the present invention is not sufficiently exhibited, which is not preferable.

It should be noted that other optional components can be added to the resin composition of the present invention as long as the effects of the present invention are not significantly impaired. Other optional ingredients include antioxidants,
Slip agent, antistatic agent, antiblocking agent, light stabilizer, ultraviolet absorber, neutralizer, antifogging agent, colorant, filler,
Examples include a nucleating agent, a clarifying agent, a plasticizer, and a flame retardant.

[0031]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

The measurement and evaluation of physical properties in Examples and Comparative Examples were carried out by the following methods.

(A) Melt flow rate (MFR) J at a test temperature of 190 ° C. and a test load of 2.16 kgf
The measurement was performed according to IS K7210.

(B) Density The density was measured in accordance with JIS K7112.

(C) Melt strength (MS) Using Capillograph 1G manufactured by Toyo Seiki Seisaku-sho, resin temperature 190 ° C., barrel diameter 9.55 mm, orifice diameter 2.10 mm, orifice length 8.00 mm, piston extrusion speed 10 mm / Min and a take-up speed of 10 m / min. (D) Molecular weight 150C ALC / GPC manufactured by Waters (column:
GMHHR-H (S) manufactured by Tosoh Corporation, solvent: 1,2,2
Using 4-trichlorobenzene), a weight average molecular weight (Mw) and a number average molecular weight (Mn) were measured by a gel permeation chromatography (GPC) method. The column elution volume was calibrated by universal calibration using standard polystyrene manufactured by Tosoh Corporation.

(E) Melting point (Tm) Differential scanning calorimeter (Perkin Elmer DSC-7)
When the sample is melted at 200 ° C. for 5 minutes in the apparatus, and then cooled at a cooling rate of 10 ° C./min to 30 ° C. and then heated at a rate of 10 ° C./min. The temperature at the maximum peak position of the obtained endothermic curve was defined as the melting point (° C.).

(F) Extrusion lamination processability An extrusion lamination molding machine having a 90 mmφ extruder was used.
Kraft paper or biaxially stretched nylon film (15μ
m) was used as a substrate, and extrusion lamination was performed with a T-die effective width of 600 mm and an air gap of 115 mm. The resin processing temperature is 310 ° C. for high-pressure method low-density polyethylene (hereinafter abbreviated as LDPE) and 285 ° C. for a blend system of LDPE and ethylene / α-olefin copolymer (hereinafter abbreviated as L-LDPE) at a measured temperature under a T-die. I went in.

The high-speed spreadability (drawdown) was evaluated at the maximum speed (m / min) at which the take-up speed was increased at a screw rotation speed of the extruder of 20 rpm and the film did not break.

The neck-in is the difference (m) obtained by subtracting the actual coating width from the T-die effective width of 600 mm in a processed film having a film thickness of 20 μm and a take-up speed of 200 m / min.
m).

The extruder load was 100 k of molten resin discharge.
The motor load (g) in g / h was evaluated.

(G) Fish Eye The 20 μm laminated film processed in the above (e) was peeled off from the substrate (nylon film), and the number of fish eyes was counted (number / 0.2 m ² ) and evaluated.

(H) Heat sealing start temperature In the processing in the above (e), a film thickness of 20 μm was previously determined.
A biaxially stretched nylon film (35 μm in total thickness) on which m-L-LDPE was extrusion-laminated was used as a substrate.
On the L-LDPE layer side of this substrate, each resin composition was subjected to extrusion lamination with a film thickness of 30 μm to provide a heat seal layer. Using this three-layer laminate film, a sealer pressure of 2 kg / c is applied by a tester heat sealer.
Heat sealing was performed at m ² and a sealing time of 1 second. Heat sealing was performed while changing the temperature of the seal bar by 5 ° C, and each sample was subjected to T-peeling at a speed of 300 mm / min with a shopper type tensile tester, and the heat sealing strength (kg / 15 mm) of each sample was measured. did. From the correlation between the obtained heat seal temperature and heat seal strength, the heat seal temperature at which the heat seal strength reached 4 kg / 15 mm was defined as the heat seal start temperature.

(I) Comprehensive Evaluation From the results obtained by the above-mentioned various evaluation methods, the comprehensive evaluation for each resin composition was evaluated from good to bad in the order of △ to △ to ×.
Indicated by Large drawdown, small neck-in, small motor load, few fish eyes,
Those with a low heat sealing start temperature are good.

<Example 1> MFR 13 g / 10 min, density 0.919 g / c manufactured by high pressure radical method
40 ppm of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane as a radical generator was added to LDPE having an m ^{3 of} 15 mN and a melt strength (MS) of 15 mN.
Using a mmφ extruder, melt kneading and pelletizing were performed at 200 ° C., MFR 11 g / 10 min, density 0.919
LDPE having a g / cm ³ and a melt strength (MS) of 40 mN was obtained. To 100 parts by weight of the pellets, add 300 parts of an antioxidant.
ppm (a mixture of 100 ppm of Irganox 1076 as a phenolic antioxidant and 200 ppm of Irgafos P-EPQFF as a phosphorus antioxidant) and a polyethylene-based wax (density 0.914 g /
cm ³ , Tm = 102 ° C., Mw = 5180, Mn = 18
50, low-density polyethylene wax having Mw / Mn = 2.8), and melt kneading and pelletizing at 200 ° C. using a 50 mmφ extruder.
The desired resin composition was obtained.

Using this resin composition as a raw material, 90 mmφ
Processing was performed at a resin processing temperature of 310 ° C. (actually measured temperature under a T-die) using an extrusion laminate molding machine having an extruder, and workability was evaluated using kraft paper as a base material. Next, the substrate was changed to a biaxially stretched nylon film to obtain a laminated film for fisheye measurement. Table 1 shows the results of these evaluations.

<Comparative Example 1> MFR1 was added without adding a radical generator, an antioxidant, and a polyethylene wax.
3 g / 10 min, density 0.919 g / cm ^3, except that the LDPE of melt strength (MS) 15 mN was directly as a raw material, processed in the same manner as "Example 1" was evaluated. Table 1 shows the results.

<Comparative Example 2> Processing was performed in the same manner as in "Example 1" except that no polyethylene wax was added.
An evaluation was performed. Table 1 shows the results.

<Comparative Example 3> Processing and evaluation were performed in the same manner as in "Example 1" except that the radical generator and the antioxidant were not added. Table 1 shows the results.

Example 2 MFR produced by a high-pressure radical method: 8 g / 10 min, density: 0.919 g / cm ³ ,
50 ppm of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane as a radical generator was added to LDPE having a melt strength (MS) of 20 mN, and
Melt kneading and pelletizing were performed at 200 ° C. using an extruder, MFR 3 g / 10 min, density 0.919 g / cm
^3. LDPE having a melt strength (MS) of 100 mN was obtained. 900 ppm of an antioxidant is added to 100 parts by weight of the pellet.
(Irganox 107 as a phenolic antioxidant
6 mixed with 300 ppm, and 600 ppm of Irgafos P-EPQFF as a phosphorus antioxidant)
And polyethylene wax (density 0.914 g / cm
³ , Tm = 102 ° C., Mw = 5180, Mn = 185
0, low-density polyethylene wax having an Mw / Mn of 2.8), and further added were 15 g / 10 minutes of MFR produced by Ziegler catalyst and a density of 0.91.
0 g / cm ³ of 300 parts by weight of L-LDPE was added,
Melt kneading and pelletizing were performed at 200 ° C. using a 50 mmφ extruder to obtain a target resin composition.

Using this resin composition as a raw material, 90 mmφ
Processing was performed at a resin processing temperature of 285 ° C. (actually measured temperature under a T-die) using an extrusion laminating machine having an extruder, and workability was evaluated using kraft paper as a base material. Next, the substrate was changed to a biaxially stretched nylon film to obtain a laminated film for fisheye measurement. Further, the base material is 20 μm thick.
Extrusion-laminated film thickness of 15 L-LDPE
A laminated film for heat seal measurement was obtained by changing to a biaxially stretched nylon film of 35 μm (thickness meter: 35 μm). Table 2 shows the evaluation results.

<Example 3> Polyethylene wax (density 0.914 g / cm ³ , Mw = 5180, Mn = 18)
Processing and evaluation were performed in the same manner as in "Example 2" except that 0.5 part by weight of a low-density polyethylene wax having a Tm of 102 ° C and Mw / Mn of 2.8 was added. Table 2 shows the results.

Example 4 Polyethylene wax (density 0.914 g / cm ³ , Tm = 102 ° C., Mw = 51)
80, Mn = 1850, and low-density polyethylene wax having Mw / Mn = 2.8) were processed and evaluated in the same manner as in "Example 2" except for adding 3.0 parts by weight. Table 2 shows the results.

<Comparative Example 4> Processing and evaluation were performed in the same manner as in "Example 2" except that the radical generator and the polyethylene wax were not added. Table 2 shows the results.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

As described above, when the resin composition of the present invention is used, a film having excellent processing suitability in film processing and reducing the load on the extruder, and at the same time, a film having a good appearance with few fish eyes in the formed film can be obtained. can get.

[0057]

Claims (2)

[Claims] (1) a density of 0.880 to 0.950 g / cm ^3;
And the melt strength (MS) at 190 ° C. is 3
A polyethylene wax having a weight average molecular weight (Mw) and a number average molecular weight (Mn) ratio (Mw / Mn) of 3 or less in 100 parts by weight of polyethylene in a range of 0 to 300 mN and a molecular weight distribution of 0.01 to 5; A resin composition comprising parts by weight. 2. A resin composition comprising 100 parts by weight of the resin composition according to claim 1 and 1 to 2000 parts by weight of an ethylene / α-olefin copolymer.