JPH0859907A - Polyethylene resin composition - Google Patents

Abstract

PURPOSE: To obtain the subject composition excellent in adhesion to paper, metal foil, a polyolefin basic material, etc., and also excellent in low temperature heat sealing and hot tacky adhesivity by compounding a high-pressure low-density polyethylene with a specific copolymer. CONSTITUTION: This resin composition is composed of (A) 95-40wt.% of a high- pressure low-density polyethylene (preferably, 0.88-0.92g/cm<3> in density and 3-15g/10min in a melt flow rate) and (B) 5-60wt.% of a polyethylene-ethylene/ butene-polyethylene triblock copolymer having a melt peak temperature of 30-105 deg.C measured by DSC and a critical strain-energy release ratio of >=100J/m<2> (preferably, 5090 wt.% in ethylene/butene content). Further, the component A is generally obtained by polymerizing ethylene at 120-300 deg.C under the pressure of 800-4000kg/cm<2> using autoclave-type or tubular- -type reactor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene resin composition which is excellent in adhesiveness to paper, metal foil, polyolefin substrate, etc., and is excellent in low-temperature heat-sealing property and hot tack property, and a laminate thereof.

[0002]

2. Description of the Related Art Generally, a laminate used as a packaging material is a polyolefin on a plastic film or paper such as polypropylene, nylon or polyethylene terephthalate, a substrate such as an aluminum foil, or a polyolefin such as a carboxylic acid, an acid anhydride or the like. A laminate of modified polyolefins modified with the above-mentioned ester is used.

Among polyolefins, high-pressure low-density polyethylene (low-density polyethylene polymerized by high-pressure method) is widely used because of its excellent processing characteristics, transparency and heat-sealing property. Further, there are methods such as an extrusion laminating method and a dry laminating method for laminating a layer made of high-pressure low density polyethylene on a substrate, but the extrusion laminating method which is advantageous in terms of productivity and cost is widely used. .

However, when a high-pressure low-density polyethylene laminated film is produced by an extrusion laminating method, there is a problem that the adhesive strength between the base material and the polyethylene resin layer is weak. As a method for improving this, a method of increasing the molding temperature or a method of using an adhesive such as a urethane-based adhesive made of polyethyleneimine, isocyanate or the like (hereinafter referred to as AC agent) (Japanese Patent Laid-Open No. 62-103139, Japanese Patent Laid-Open No. 3-103139). 76
640) and the like have been proposed.

However, polyethylene, polypropylene,
In the case of a polyolefin base material composed of a polyolefin film such as an α-olefin homopolymer such as poly-4-methylpentene-1 or a copolymer, heat shrinkage occurs when the molding temperature is raised, and a printing pitch shift occurs. In addition, the heat seal strength is reduced due to the oxidative deterioration of the polyethylene resin. Further, even if the AC agent is used, there is a problem that sufficient adhesive strength cannot be obtained because the polyolefin substrate itself is nonpolar. In addition, since the AC agent uses a large amount of organic solvent, it is not preferable in terms of cost and safety.

In addition, since the paper base material cannot be used because it swells and contracts when it is applied and dried, it is necessary to raise the molding temperature in order to improve the adhesive strength. is there. However, if the molding temperature is increased, the adhesive strength is improved, but the heat seal strength and hot tack property are deteriorated. As described above, it has been difficult to improve the heat-sealing property and the hot tack property while maintaining a sufficient adhesive strength.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a polyethylene resin composition having excellent adhesion to paper, metal foil, polyolefin substrate, etc., and excellent low temperature heat-sealing property and hot tack property, and a laminate thereof. The challenge is to provide.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that a polyethylene-ethylene / butene-polyethylene triblock copolymer (hereinafter also referred to as TBC) is added to high-pressure low-density polyethylene. Yes, even if the AC agent layer is not provided,
Can be firmly bonded to paper, metal foil, polyolefin substrates, etc.
Moreover, they have found that they have excellent properties such as low-temperature heat-sealing property and hot tack property, and have completed the present invention.

That is, the above problems are (A) 95-40% by weight of high-density low-density polyethylene, (B) a melting peak temperature by DSC of 30-105 ° C., and a critical strain energy release rate of 100 J / m ^2. A polyethylene resin composition comprising the above polyethylene-ethylene / butene-polyethylene triblock copolymer in an amount of 5 to 60% by weight, and a polyethylene resin composition obtained by laminating the polyethylene resin composition on a substrate using an extrusion laminating method. It can be solved by a laminate. Hereinafter, the present invention will be described in detail.

The high-pressure low-density polyethylene, which is the component (A) in the present invention, contains ethylene in an amount of 120 to 300 in an autoclave type or tubular type reactor.
It is generally obtained by polymerizing at a temperature of 800 to 4000 kg / cm ² . Melt flow rate (JIS-K67
It is measured according to 60 and is abbreviated as MFR hereinafter. ) Is generally 1 to 50 g / 10 minutes, preferably 1 to 30 g / 10
Min, more preferably 3 to 15 g / 10 min. MFR
If it is less than 1 g / 10 minutes, the processing speed cannot be increased due to insufficient fluidity, and if the MFR exceeds 50 g / 10 minutes, the neck-in at the time of molding becomes large and the heat seal strength of the product decreases. The density is generally 0.88 to
0.93 g / cm ^3, which is heat sealability at low temperature,
Considering the hot tack property, it is preferably less than 0.92 g / cm ³ .

The polyethylene-ethylene / butene-polyethylene triblock copolymer (hereinafter referred to as component (B))
Sometimes called TBC. ) Is one in which an ethylene / butene copolymer is located at the center of the molecule and crystalline polyethylene blocks are located at both ends thereof, and is generally produced by hydrogenating a butadiene copolymer. To be done. The melting peak temperature by DSC of TBC used in the present invention is required to be 30 to 105 ° C.
If the melting peak temperature is less than 30 ° C, blocking of the product occurs, and if the melting peak temperature exceeds 100 ° C, the heat sealing property and hot tack property at low temperature deteriorate.

The critical strain energy release rate of TBC is 10
Need to be 0 J / m ² or more, 150 J / m
It is preferably ² or more. When the critical strain energy release rate is less than 100 J / m ² , good adhesive strength is not exhibited.

Here, the critical strain energy release rate means that the melt flow rate (JIS K6758) is 30 g / 1.
Polypropylene having 0 minutes, Mw / Mn of 7 and stereoregularity mm of 98% (hereinafter referred to as standard polypropylene).
Is a critical strain energy release rate (hereinafter referred to as Gc) at a flat interface between and, and is a value when measured by an asymmetric double cantilever beam method in a phase angle range of −2 to −12 °. .

The asymmetric double cantilever beam method (hereinafter referred to as ADCB) is used to measure the Gc at the interface because cracks run along the interface. In the peel test conventionally used, cracks cannot be grown along the interface, and Gc at the interface cannot be accurately measured. The parameter that determines the crack growth direction is the phase angle ψ defined by the following equation. ψ = tan ⁻¹ (KII / KI) where KI and KII are stress intensity factors for mode I and mode II. The phase angle ψ depends on the geometry of ADCB, elastic modulus of each material, Poisson's ratio, and crack length.
Numerically, it is evaluated by the boundary element method and the finite element method.
In the present invention, it is necessary to measure Gc in a phase angle range of −2 to −12 °. If the phase angle is outside the range of −2 to −12 °, the growth of cracks becomes unstable and Gc cannot be evaluated accurately.

The content of ethylene / butene in the TBC in the present invention is generally 35 to 95% by weight, preferably 40.
˜90% by weight, more preferably 50 to 90% by weight. If the ethylene / butene content is less than 35% by weight, the heat sealability and hot tack property at low temperature are deteriorated.
If it exceeds 5% by weight, workability is deteriorated and good adhesive strength cannot be obtained.

The polyethylene resin composition of the present invention is (A)
It is manufactured by mixing the component and the component (B). The mixed composition at this time is 5 to 60% by weight of the component (B), preferably 10 to 60% by weight, more preferably 2%.
It is 0 to 50% by weight. If the amount of the component (B) is more than 60% by weight, the moldability is lowered, and if it is less than 5% by weight, the adhesive strength is lowered, and good low temperature heat sealing property and hot tack property cannot be obtained.

The mixing method of the components (A) and (B) is not particularly limited, and a method of dry blending with a mixer such as a Henschel mixer or a tumbler generally used in the field of synthetic resins, kneader, Banbury, extrusion. A method of mixing while melting with a machine is used.
When mixed, 2,6-t-butyl-, which is widely used in the field of synthetic resins and synthetic rubbers, may be used.
Methylphenol, 4,4'-thiobis (3-methyl-
6-t-butylphenol) and other phenolic antioxidants, dilaurylthiodipropionate, distearylthiodipropionate and other sulfide antioxidants, tridecyl phosphite, trinonylphenyl phosphite and other phosphite antioxidants Antioxidant, 2-hydroxy-
In addition to heat, oxygen and light stabilizers such as benzophenone-based UV absorbers such as 4-methoxybenzophenone and substituted benzotriazole-based UV absorbers, additives such as flame retardants, fillers, colorants, lubricants and antistatic agents , May be added as long as the adhesiveness, heat sealability and hot tackiness are not impaired.

The polyethylene resin composition thus obtained is laminated on a substrate by an extrusion laminating method or a dry laminating method to form a polyethylene resin layer. In the extrusion laminating method, a polyethylene resin composition is heated and melted by using an extruder, extruded in a film form from a die and placed on a substrate, and molding and laminating are simultaneously performed. The polyethylene resin composition layer can be formed on one side or both sides of the substrate, and if the polyethylene resin composition layer is on the adhesive surface, a coextrusion laminating method in which two or more kinds of resins are simultaneously extruded Good. When laminating on a polyolefin substrate, a generally widely used dry laminating method may be used.

The polyolefin base material is α-type such as polyethylene, polypropylene, poly 4-methylpentene-1.
It refers to a polyolefin substrate composed of a polyolefin film such as an olefin homopolymer or a copolymer. If necessary, the polyolefin base material may be subjected to discharge treatment such as corona discharge or plasma discharge, or surface treatment with a chemical such as sulfuric acid or chromic acid. Further, it may be uniaxially or biaxially stretched depending on the application. Further, it may be a laminate with another plastic film or foil as long as the polyolefin layer is on the adhesive surface.

The molding temperature during laminate molding is generally 2
40-340 degreeC, Preferably it is 260-330 degreeC, More preferably, it is 300-325 degreeC. Molding temperature is 240 ℃
If it is lower than this, sufficient adhesive strength cannot be obtained, and the molding speed cannot be increased, resulting in a decrease in productivity.
When the molding temperature exceeds 340 ° C., the heat seal strength decreases due to deterioration of the resin surface, and in the case of a polyolefin substrate, shrinkage due to heat causes printing pitch deviation.

[0021]

The present invention will be described in more detail with reference to Examples and Comparative Examples. (Example 1)

(Measurement of critical strain energy release rate Gc)
Polyethylene-ethylene / butene-ethylene triblock copolymer (TBC-1) having a melting peak by DSC of 88 ° C., a melt flow rate (JIS-K6758) of 0.6 g / 10 minutes and a density of 0.88 g / cm ^3. ) Was pressed to form a film having a thickness of 10 μm. This film was sandwiched between standard polypropylene sheets with different thicknesses made by pressing, and the temperature was 180 ° C.
Fusion was performed under the conditions of ° C, pressure of 3.5 kg / cm ² , and time of 10 minutes to form a planar interface. The interface was cracked, and the Gc was measured by the ADCB method (Journal Closed Loop,
1990, Vol. 23, page 3929. )
It was measured at. The phase angle is controlled by the ratio of the thickness of the standard polypropylene sheet, and the boundary element method (Boundary element) is used.
ment method, BEM method). The measurement was performed at a phase angle of -7 °. The evaluation results are shown in Table 1.

(Production of Polyethylene Resin Composition) (A)
As an ingredient, MFR 8.0g / 10 minutes shown in Table 1,
High-pressure polyethylene (PE with a density of 0.918 g / cm ³
80 parts by weight of -1) and 20 parts by weight of TBC-1 as the component (B) were dry blended by a tumbler for 10 minutes, and then melt-kneaded at a die temperature of 200 ° C using a 40 mmφ extruder to form pellets.

(Production of Laminate) The production of the laminate was carried out by extrusion laminating. The extrusion laminating molding machine was equipped with a 90 mmφ extruder and used a molding machine having a roll surface width of 1300 mm. The lamination was performed on a biaxially oriented polypropylene film (abbreviated as OPP) or a paper substrate at a molding temperature of 315 ° C., a molding speed of 70 m / min, and a laminate thickness of 30 μm.

(Measurement of Adhesive Strength) The laminate was cut into a strip having a width of 15 mm in the flow direction at the time of molding, peeled between the substrate and the polyethylene resin composition, and peeled at 180 ° at a speed of 300 mm / min. The peel strength at that time was evaluated. TBC
Compared to PE1 component by adding 20% by weight component, 2
More than twice the adhesive strength was obtained. Table 2 shows the evaluation results.

(Measurement of heat seal strength) 1 in the flow direction
Sealing width 5 mm, temperature 1 with the polyethylene resin surfaces of the laminate cut into strips 5 mm wide in contact with each other
Heat sealing was performed under conditions of 00 to 140 ° C., pressure of 2 kg / cm ² , and sealing time of 1 second, and peeling was performed at the seal interface under the same conditions as the measurement of the adhesive strength to measure the seal strength. T
By adding BC, the heat-sealing strength starts to rise from 110 ° C., and the heat-sealing property at low temperature is greatly improved. Table 2 shows the evaluation results.

(Measurement of Hot Tack) Heat sealing was carried out under the same conditions as in the measurement of heat sealing strength, and the peeling distance when a load of 23 g was applied was evaluated. Similar to heat sealing, the hot tack property is significantly improved at low temperature, especially at 120 ° C or lower. Table 2 shows the evaluation results.

(Example 2) Lamination was carried out in the same manner as in Example 1 except that 78 g / m ² of high quality paper was used as the substrate.
Only the adhesive strength was evaluated, and the same method as in Example 1 was used. Adhesion was also good for paper, and the adhesion was such that the paper cohesively failed. Table 2 shows the evaluation results.

Example 3 50% by weight of PE-1 as the component (A) and 50% by weight of TBC-1 as the component (B).
Composition and lamination were performed in the same manner as in Example 1 except that the above was adopted. By increasing the TBC, all of the adhesive strength, heat seal strength and hot tack property are further improved. Table 2 shows the evaluation results.

(Example 4) Lamination was carried out in the same manner as in Example 3 except that 78 g / m ² of high-quality paper was used as the base material.
Only the adhesive strength was evaluated, and the same method as in Example 1 was used. Adhesion was obtained in the same manner as in Example 2 such that the paper cohesively failed. Table 2 shows the evaluation results.

Example 5 As the component (B), the melting peak by DSC was 92 ° C., the melt flow rate (JIS
-K6758) is 1.5 g / 10 minutes, density 0.88 g /
A laminate was produced and evaluated in the same manner as in Example 1 except that 20% by weight of a polyethylene-ethylene / butene-polyethylene triblock copolymer (TBC-2) having a cm ³ and Gc of 140 J / m ² was used. . The adhesive strength, heat seal strength, and hot tack were good.

(Example 6) TBC-2 as the component (B)
A laminate was produced and evaluated in the same manner as in Example 1 except that 50% by weight was used. By increasing the TBC component, the adhesive strength, heat seal strength, and hot tack property were further improved as compared with Example 5. Table 2 shows the evaluation results.

Comparative Example 1 Lamination and evaluation were carried out in the same manner as in Example 1 except that only PE-1 which was the component (A) was used instead of the polyethylene resin composition. With only the component (A), the adhesive strength was weak, and sufficient values could not be obtained for both heat sealability and hot tack at a low temperature of 130 ° C. or lower. Table 2 shows the evaluation results.

(Comparative Example 2) PE-1 as the component (A) is 35% by weight, and TBC-1 as the component (B) is 65% by weight.
Lamination was attempted in the same manner as in Example 1 except that the polyethylene resin composition was used, but the motor load on the extruder was large and the speed could not be increased to 70 m / min.

Comparative Example 3 TBC-3 as the component (B)
Same as Example 1 except that is used. Since the melting point of the component (B) is high, the heat seal strength at low temperature,
No significant improvement in hot tack was observed. Table 2 shows the evaluation results.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

EFFECT OF THE INVENTION The polyethylene resin composition of the present invention and the laminate thereof have excellent adhesiveness to paper and polyolefin substrates, and have good heat sealability and hot tack at low temperature.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B29L 7:00 (72) Inventor Hiroshi Kasahara 3-2 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Awakazu Electric Works Co., Ltd. Kawasaki Plastics Research Laboratory (72) Inventor Shuichi Tanaka 3-2 Chidori-cho, Kawasaki-ku, Kawasaki City, Kanagawa Sho Town No.3-2 Showa Denko Co., Ltd. Kawasaki Resin Research Laboratory

Claims (3)

[Claims] 1. (A) High-pressure method low-density polyethylene 95-
40% by weight, and (B) DSC has a melting peak temperature of 3
0 to 105 ° C, and the critical strain energy release rate is 10
A polyethylene resin composition comprising 5 to 60% by weight of a polyethylene-ethylene / butene-polyethylene triblock copolymer having 0 J / m ² or more. 2. The polyethylene resin composition according to claim 1, wherein (A) the high-pressure low-density polyethylene has a density of 0.88 to 0.92 g / cm ³ . 3. A laminate obtained by laminating the polyethylene resin composition according to claim 1 or 2 on a substrate using an extrusion laminating method.