JPH0948816A - Modified ehtylene-alpha-olefin copolymer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject copolymer having high transparency and excellent adhesivity to metals and polar resins and useful for film, etc., while suppressing the generation of gel by irradiating a base resin with radiation in a specific range and adding a polar monomer to effect the modification of the resin. SOLUTION: A straight-chain ethylene-α-olefin copolymer irradiated with radiation in such a manner as to satisfy the formula 1<=MFRa/MFRb<=10 (MFRa is melt flow rate before irradiation; MFRb is melt flow rate after irradiation) is modified with a polar monomer to obtain the subject copolymer having a density of 0.850-0.945g/cm<3> , the ratio of weight-average molecular weight to number-average molecular weight (Mw/Mn) of <=3 determined by GPC, the ratio of the average branch number of 30wt.% high-molecular weight region to that of 30wt.% low-molecular weight region fractionated by GPC of 0.8-1.2 and a melt flow rate of 1.0-50g/10min measured at 190 deg.C under 2,160g load.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to modified ethylene / α.
-For the olefin copolymer composition, more specifically,
The present invention relates to a method for producing a modified ethylene / α-olefin copolymer having less gelation, excellent transparency, and excellent adhesiveness to a metal or a polar resin as compared with conventionally known ethylene copolymers.

[0002]

2. Description of the Related Art Generally, various polyolefins are excellent in mechanical strength, chemical resistance, etc. and are used in various fields.

Conventionally, low density polyethylene (LDPE) produced by a high pressure method has excellent processability and is processed into shapes such as tubes, pipes, sheets and films and used in a wide range of fields. On the other hand, a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms is
It has a linear molecular structure and a density of 0.945 g / cm ³ or less, and contains a Ziegler type catalyst composed of a solid catalyst component containing magnesium and titanium and an organoaluminum compound or a cyclopentadienyl derivative. Polymerized with a catalyst composed of an organic transition metal compound and a compound that reacts with the compound to form an ionic complex and / or an organometallic compound is known as linear low density polyethylene (LLDPE).

However, it has a drawback that it is poor in adhesiveness because it is chemically stable.

As a method for improving the adhesiveness of a polyolefin resin, a method in which unsaturated carboxylic acids and an organic peroxide are added to the polyolefin resin and melt kneading is generally known.

Specifically, as disclosed in Japanese Patent Laid-Open No. 63-117008, high density polyethylene having a branching degree of 5 or less per 1000 carbon atoms in the main chain has a specific amount of unsaturated carvone. A method in which an acid and an organic peroxide are added and melt-kneaded is proposed. When high density polyethylene, low density polyethylene, linear low density polyethylene or the like having a large degree of branching is used as the polyethylene, crosslinking is excessively advanced during kneading, resulting in generation of gel and reduction in adhesive strength.

As described above, in the conventional melt-kneading method, the polyethylene that can be used is greatly limited, and it is difficult to use it in the field where transparency is required.

[0008] In order to solve these problems, at present, it is general to manufacture by a solution method capable of synthesizing under mild conditions instead of the melt kneading method, but the problem of high manufacturing cost Was left.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves such a problem in a linear low-density ethylene / α-olefin copolymer, that is, improves the adhesiveness without easily forming a gel, It is an object of the present invention to provide a method for producing the above-mentioned copolymer, which contributes to improving processability, improving productivity, and reducing production cost.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have identified that a linear low-density ethylene / α-olefin copolymer having a specific molecular weight distribution and branching degree distribution does not form a gel. The inventors have found that the above problems can be solved by irradiating with radiation in the range, and then adding a polar monomer and melt-kneading, and have reached the present invention.

That is, according to the present invention, ethylene and 3 to 12 carbon atoms are used.
Obtained by copolymerizing .alpha.-olefins having a density of 0.
850 to 0.945 g / cm ³ , the molecular weight distribution determined by GPC is 3 or less, and the low molecular weight region 3 relative to the average branch number of the high molecular weight region 30% by weight fractionated by GPC is 3
The ratio of the average number of branches of 0% by weight is 0.8 or more and 1.2 or less, and according to JIS K6760, 190 ° C, 2160
Melt flow rate (MFR) measured under g load
Is 1.0 to 50 g / 10 min linear low density ethylene / α
-Melt flow rate (MF) of linear ethylene / α-olefin copolymer before irradiation of olefin copolymer
Ra) and melt flow rate after irradiation (MFR
A modified ethylene / α-olefin copolymer and a method for producing the same, characterized in that the polar monomer is added and the mixture is melt-kneaded after irradiation in the range where the ratio of b) is 1 ≦ MFRa / MFRb ≦ 10. Is.

The linear low-density ethylene / α-olefin copolymer used has a weight average molecular weight / number average molecular weight of more than 3 determined by GPC, or an average of 30% by weight in a high molecular weight region fractionated by GPC. When the ratio of the low molecular weight region 30% by weight to the degree of branching exceeds the range of 0.8 or more and 1.2 or less, a gel is easily formed by irradiation with radiation and melt kneading, which is unsuitable as a product. If the amount exceeds the range, the physical properties of the product are deteriorated and the product cannot be put to practical use.

For example, the linear low-density ethylene / α-olefin obtained by the conventional Ziegler type catalyst has a low average branch number of 30% by weight in the high molecular weight region, which is fractionated by GPC, due to the nature of the catalyst used. Molecular weight range 30% by weight
The distribution of the branching degree is such that the ratio of the average number of branches of 3 is larger than 3, the generation of radicals during irradiation is non-uniform, and the generation of gel is large. Chain-like low-density ethylene / α-olefin has substantially no branching degree distribution, and the branches are uniformly present, so that radicals are uniformly generated by radiation irradiation,
It is considered that no gel was generated even when the polar monomer was added and melt-kneaded.

The Mw / Mn and the average number of branches in each region in the present invention are specifically determined as follows.

Waters 150C ALC / GP
C (column: Tohso GMHHR-H (S), solvent:
GPC using 1,2,4-trichlorobenzene)
By the method, Mw and Mn were measured, and Mw / Mn was calculated. The column elution volume was calibrated by the universal calibration method using Tosoh standard polystyrene.

Of the total amount eluted by GPC, the first eluted 30 wt% is the high molecular weight region, the subsequently eluted eluent is the peak molecular weight region, and the last eluted 30 wt% is the low molecular weight region. The molecular weight range. The average number of branches of each molecular weight region component fractionated in this way was calculated as the number of short chain branches per 1000 carbon atoms by connecting FT-IR (1760X manufactured by Perkin Elmer Co., Ltd.) as a detector of the above measuring device. I asked.

Such a linear low-density ethylene / α-olefin copolymer can be produced, for example, by the method disclosed in the following publications. JP-A-60-35006, JP-A-60-35
Japanese Patent Application Laid-Open No. 007, Japanese Patent Application Laid-Open No. 60-350088, Japanese Patent Application Laid-Open No. 3-163088, Japanese Patent Application Laid-Open No. 61-296008, Japanese Patent Application Laid-Open No. 63-22804, Japanese Patent Application Laid-Open No. 58-19.
309, Japanese Patent Application No. 60-00862, Japanese Patent Laid-Open No. 63-61010, Japanese Patent Laid-Open No. 63-152608, Japanese Patent Laid-Open No. 63-264606, Japanese Patent Laid-Open No. 63-
No. 280703, No. 64-6003, No. 1-95110, No. 3-62806, No. 1-259004, No. 64-45.
406, JP-A-60-106808, JP-A-60-137911, and JP-A-61-29600.
No. 8, Japanese Patent Publication No. 63-501369, Japanese Patent Application Laid-Open No. 61-221207, Japanese Patent Application Laid-Open No. 2-22307, Japanese Patent Application Laid-Open No. 2-173110, Japanese Patent Application Laid-Open No. 2-302.
No. 410, No. 1-129003, No. 1-210404, No. 3-66710, No. 3-70710, No. 1-2072.
48, JP-A-63-222177, JP-A-63-222178, and JP-A-63-222179.
Japanese Patent Application Laid-Open No. 1-21407, Japanese Patent Application Laid-Open No. 1-30
1704, JP-A-1-319489, JP-A-3-74412, JP-A-61-264010, JP-A-1-275609, and JP-A-63-2.
51405, JP 64-74202 A, JP 2-41303 A, JP 131488 A, JP 3-56508 A, JP 3-7070 A.
No. 8, JP-A-3-70709, and the like.

The method for producing the linear low-density ethylene / α-olefin copolymer that can be used in the present invention will be described below based on their contents. This linear low-density ethylene / α-olefin copolymer is, for example, an organic transition metal compound (I) containing a cyclopentadienyl derivative, and a compound (II) which reacts with this to form an ionic complex. ) And / or organometallic compound (III)
It can be suitably produced by copolymerizing ethylene with the above-mentioned α-olefin having 3 or more carbon atoms in the presence of a catalyst consisting of

As the α-olefin having 3 or more carbon atoms,
Propylene, 1-butene, 4-methyl-1-pentene,
3-methyl-1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1- Mention may be made of pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene and the like.

The polymerization method used can be exemplified as follows.

The polymerization conditions for the solution polymerization method are as follows. The polymerization temperature needs to be 120 ° C. or higher in consideration of the fact that the copolymer is in a solution state and that productivity is increased. The upper limit of the polymerization temperature is not particularly limited, but is preferably 300 ° C. or lower in order to suppress a chain reaction that causes a decrease in molecular weight and not to lower the catalyst efficiency. The pressure during the polymerization is not particularly limited, but is preferably at least atmospheric pressure in order to increase the productivity.

The conditions for the high pressure polymerization method are as follows. The polymerization temperature needs to be 120 ° C. or higher in consideration of the fact that the copolymer is in a solution state and that productivity is increased. The upper limit of the polymerization temperature is not particularly limited, but suppresses the chain transfer reaction that causes a decrease in the molecular weight,
In addition, the temperature is preferably 300 ° C. or lower so as not to reduce the catalyst efficiency. The pressure during the polymerization is not particularly limited, but is preferably 500 kgf / cm ² or more so that the polymerization conditions can be stably obtained in the high pressure process.

Further, in the gas phase polymerization method, the high temperature is not preferable because the copolymer is in a powder state, and it is necessary to be 100 ° C. or lower. The lower limit of the polymerization temperature is not particularly limited, but is preferably 50 ° C. or higher in order to increase productivity.

In the present invention, the linear low-density ethylene / α-olefin copolymer produced by the above method is irradiated with radiation, then a polar monomer is added, and the mixture is melt-kneaded.
Linear low-density ethylene / α-obtained by such a method
The olefin copolymer is transparent without causing gel, as compared with the one obtained by irradiating a linear ethylene / α-olefin copolymer produced by a conventional Ziegler-type catalyst with irradiation and then melt-kneading. It was possible to improve the adhesiveness and the adhesive strength.

The radiation used in the present invention may be any of γ rays, ultraviolet rays, electron beams and neutron rays, and may be 1 to 2
Irradiation is preferably performed in the range of 0 Mrad. Radiation is within the range where gel is not formed in the linear ethylene / α-olefin copolymer, that is, the ratio of the melt flow rate (MFRa) before irradiation to the melt flow rate (MFRb) after irradiation is 1 ≦ MFRa / Irradiation is performed with an absorbed dose in a range such that MFRb ≦ 10.

Although such irradiation is usually performed at room temperature,
Irradiation may be carried out at a temperature above the melting point as long as gelation does not occur. Irradiation can be carried out in air, nitrogen gas, carbon dioxide gas, but in order to prevent gelation of the linear low-density ethylene / α-olefin copolymer, it is necessary to use an inert gas atmosphere such as nitrogen gas. It is preferable to do in.

The polar monomers used in the present invention include unsaturated carboxylic acids or their derivatives, hydroxyl group-containing ethylenically unsaturated compounds, amino group-containing ethylenically unsaturated compounds, epoxy group-containing ethylenically unsaturated compounds, and aromatic compounds. Examples thereof include vinyl compounds.

Specifically, as the unsaturated carboxylic acid,
Maleic acid, maleic anhydride, fumaric acid, nadic acid anhydride, citraconic acid, crotonic acid, isocrotonic acid, mesaconic acid, itaconic acid, angelic acid, sorbic acid, acrylic acid, itaconic anhydride, citraconic anhydride, etc. are preferred, of which Maleic anhydride is particularly preferable. Examples of unsaturated carboxylic acid derivatives include metal salts, amide imides and esters of the above carboxylic acids. In addition, in the method of the present invention, one type or two or more types of the polar monomers may be used.

The radiation-treated linear low-density ethylene / α-olefin copolymer in the present invention is usually used for polyolefins such as antioxidants, weathering stabilizers, antistatic agents, lubricants, antiblocking agents, etc. Additives may be added, but in order to stabilize the remaining radicals, it is preferable to irradiate the linear low-density ethylene / α-olefin copolymer containing no such additives with radiation. It is preferable to carry out the reaction with a polar monomer, and then add various stabilizers to stabilize.

The method of the present invention can be carried out batchwise, but is preferably carried out continuously.

[0031]

EXAMPLES The present invention will be described below with reference to examples, but is not limited to these examples.

The physical properties in the examples were measured as follows.

Transparency: A 100 μm thick pressed sheet was prepared and measured according to ASTM-D-1003.

Adhesive force measuring method: A press sheet having a thickness of 100 μ was treated with an aluminum foil having a thickness of 500 μ and a heel sheet, and then the peel strength was measured to evaluate the adhesive force. Use a heat sealer for the heel sheet. 2
It was performed under the conditions of 00 ° C., 1 kg / cm ² , and 30 seconds. After forming the heel sheet, a test sample having a width of 25 mm was prepared and the peel strength was measured.

Example 1 Polymerized with a metallocene-type catalyst and having a density of 0.90
0 g / cm ³ , MFR 10 g / 10 min, ratio of average branch number of low molecular weight region 30 wt% to average branch number of high molecular weight region 30 wt% fractionated by GPC is 1.1, G
The ethylene / 1-butene copolymer pellets having a molecular weight distribution Mw / Mn = 1.8 by PC were subjected to γ-ray irradiation treatment with an absorbed dose of 2.5 Mrad.

100 parts by weight of irradiated pellets and 2 parts by weight of maleic anhydride were prepared, dry-blended and melt-kneaded at 240 ° C. to obtain a modified linear copolymer. This modified copolymer was subjected to MFR measurement at 190 ° C. and a capillary type rheometer at a temperature of 190 ° C.
Shear viscosity was measured at various shear rates under the condition of L / D = 20 to obtain a flow curve. The shear rate at which melt fracture occurred was determined by observing the surface condition of the extruded strands. As a result, M
Despite the FR was reduced to 1.2g / 10 minutes,
It was confirmed that the gel that does not dissolve in boiling xylene was less than 1%, that the shear rate dependence of the shear viscosity was improved, that melt fracture did not occur up to the high shear rate region, and that the processability was good.

30 parts by weight of the obtained modified product and 70 parts by weight of low-density polyethylene (density 0.927 g / cm ² ) were dry blended, and further melt-kneaded to obtain a pelletized resin composition. The obtained composition is 1 using a press molding machine.
The sheet was heated at 60 ° C. for 15 minutes to obtain a 100 μm sheet.

The transparency of the obtained sheet and the adhesive strength with an aluminum plate were measured.

The results are shown in Table 1.

Comparative Example 1 Polymerized with a Ziegler type catalyst, having a density of 0.88
5 g / cm ³ , MFR 10 g / 10 min, ratio of the average number of branches in 30% by weight of low molecular weight fraction to the number of branches in 30% by weight of high molecular weight fraction fractionated by GPC was 5, G
Ethylene with a molecular weight distribution Mw / Mn = 5 by PC
The 1-butene copolymer pellet was subjected to γ-ray treatment in the same manner as in Example 1, and the pellet was reacted with maleic anhydride under the same conditions as in Example 1 to observe the surface state of the strand. As a result, melt fracture occurred in the low shear rate region, and only the one with poor surface condition was obtained.

30 parts by weight of the obtained modified product and 70 parts by weight of low-density polyethylene (density 0.927 g / cm ² ) were dry blended, and further melt-kneaded to obtain a pelletized resin composition. The obtained composition is 1 using a press molding machine.
The sheet was heated at 60 ° C. for 15 minutes to obtain a 100 μm sheet.

The transparency of the obtained sheet and the adhesive strength with an aluminum plate were measured.

The results are shown in Table 1.

[0044]

[Table 1]

[0045]

As described above, according to the present invention, the linear low-density ethylene / α-olefin copolymer is modified by the melt-kneading method without generating gel while maintaining the excellent properties. It is possible to improve transparency and adhesiveness, and thus contribute to improvement of productivity and reduction of production cost.

Claims (2)

[Claims] 1. A melt flow rate (MF) before irradiation with radiation.
Ra) and melt flow rate after irradiation (MFR
The linear ethylene / α-olefin copolymer obtained by irradiation so that the ratio of b) is 1 ≦ MFRa / MFRb ≦ 10 is modified with a polar monomer, and the following (a) to (d) are obtained. A modified ethylene / α-olefin copolymer having the following characteristics. (A) Density: 0.850 to 0.945 g / cm ³ ,
(B) Ratio (Mw / Mn) of weight average molecular weight (Mw) and number average molecular weight (Mn) obtained from GPC: 3 or less,
(C) Ratio of average branch number of 30 wt% of low molecular weight region to average branch number of 30 wt% of high molecular weight region fractionated by GPC: 0.8 or more and 1.2 or less, (d) 190 ° C, 21
Melt flow rate measured with a load of 60 g: 1.0 to
50g / 10 minutes 2. A linear ethylene / α-olefin copolymer consisting of ethylene and an α-olefin having 3 to 12 carbon atoms is melt flow rate (MFRa) before irradiation and melt flow rate (MFRb) after irradiation. ) Ratio is 1
A modified ethylene / α-olefin copolymer characterized by irradiating radiation within a range of ≦ MFRa / MFRb ≦ 10, and further modifying the obtained linear ethylene / α-olefin copolymer with a polar monomer. Production method. (A) Density: 0.850 to 0.945 g / cm ³ ,
(B) Ratio (Mw / Mn) of weight average molecular weight (Mw) and number average molecular weight (Mn) obtained from GPC: 3 or less,
(C) Ratio of average branch number of 30 wt% of low molecular weight region to average branch number of 30 wt% of high molecular weight region fractionated by GPC: 0.8 or more and 1.2 or less, (d) 190 ° C, 21
Melt flow rate measured with a load of 60 g: 1.0 to
50g / 10 minutes