JP2805943B2 - Polyethylene composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polyethylene composition having excellent hot tack properties.

<Prior Art> Polyethylene resins are widely used as single-layer or multilayer films with other thin-film materials.

In recent years, there has been a strong demand for packaging films capable of increasing the filling speed. Increasing the filling speed
It means faster film feeding speed, shorter heat sealing, and shorter time before the load of the contents is applied to the sealing surface immediately after heat sealing.
Due to its waist, heat sealability is exhibited at low temperatures, and the seal does not peel off even if a load of the contents is applied while the seal portion is still hot immediately after heat seal, that is, a film having good hot tack properties. It is necessary.

Among the polyethylene resins, a random copolymer of ethylene and α-olefin such as butene, hexene, and octene, called linear low-density polyethylene (L-LDPE),
It is known that hot tack property is superior to branched low density polyethylene produced by a conventional radical polymerization method. However, even with L-LDPE, the hot tack property is insufficient for increasing the filling speed required in recent years.

<Problems to be Solved by the Invention> In contrast to the recent demand for a higher filling speed in packaging films, conventionally known polyethylene resins have insufficient hot tack properties. Accordingly, an object of the present invention is to provide a polyethylene resin which is stiff and more excellent in hot tack property than L-LDPE, particularly excellent in hot tack property at low temperatures.

<Means for Solving the Problems> The present inventor has studied in detail the mechanism of the development of hot tack, which is an important property in polyethylene for packaging, and has ethylene and α-olefin each having a specific thermal transition behavior. It has been found that a polyethylene composition consisting of two kinds of copolymers of the formula (1) and (2) exhibits stiffness and excellent hot tack property, particularly excellent hot tack property at low temperatures.

That is, the present invention has a density of less than 0.900 or 0.910 g / cm ^3, the Atsushi Nobori thermogram as measured by a differential scanning calorimeter after gradual cooling after complete thawing, 80 to an endothermic peak in the range of 100 ° C. Is observed, the endothermic amount of the endothermic peak is 0.8 or more of the total endothermic amount, and the α-olefin content is 2.0 to 1
A random copolymer (I) of 0.0 mol% of ethylene and an α-olefin having 3 to 10 carbon atoms and a density of 0.910
Is less than 0.930 g / cm ³ , and ethylene and an α-carbon having 3 to 10 carbon atoms at which an endothermic peak is observed at 110 ° C. or higher in a heating thermogram measured by a differential scanning calorimeter.
The present invention relates to a polyethylene composition comprising a random copolymer (II) with an olefin.

 Hereinafter, each item will be described in detail.

(1) Copolymer (I) The copolymer (I) of ethylene and an α-olefin having 3 to 10 carbon atoms used in the present invention has a density of 0.900 g / cm ^3.
Above and less than 0.910 g / cm3, the endothermic peak is within the range of 80 to 100 ° C in the temperature rise thermogram (relation between endothermic rate and temperature) measured by the differential scanning calorimeter (DSC). Observed, the endothermic amount of the endothermic peak needs to be 0.8 or more of the total endothermic amount. Examples of the α-olefin include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like, and an α-olefin having 4 to 8 carbon atoms is preferable.

The density is measured after annealing at 100 ° C. for 1 hour according to JIS K6760. If the density is out of the range of 0.900 or more and less than 0.910 g / cm ³ , excellent hot tack properties cannot be obtained.

In the present invention, the temperature rise thermogram by DSC is maintained at 150 ° C. for 5 minutes in DSC in order to completely melt the sample (pre-melt), and then gradually cooled to 40 ° C. at a rate of 1 ° C./min.
Thereafter, the mixture is heated to 150 ° C. at a rate of 10 ° C./min to obtain a thermogram. A straight line is connected between 50 ° C. and the temperature at which all the endotherms are completed on the temperature rise thermogram, and is used as a baseline for obtaining the calorific value. In the present invention, the “peak” clearly indicates a maximum on the heat absorption side, and a shoulder (shoulder) shape simply identified by an inflection point is not regarded as a “peak”.

The copolymer (I) used in the present invention has a temperature rising thermogram within the range of 80 to 100 ° C., preferably 8 to 100 ° C.
It is necessary that an endothermic peak is observed within the range of 5 to 95 ° C. A plurality of endothermic peaks may be observed within the above temperature range. Unless the endothermic peak is observed within the above temperature range, excellent hot tack properties cannot be obtained. If another endothermic peak outside the temperature range is observed, [Delta] H / [Delta] H _T to the total endothermic amount [Delta] H _T endotherm [Delta] H of the endothermic peak observed in the temperature range of 0.8 or more, preferably 0.9 or more It is necessary to be. [Delta] H _T from the area between the heating thermogram and the base line, [Delta] H each temperature between the endothermic peak observed adjacent to the hot side and cold side of the outdoor temperature range should be present endothermic peak Temperature thermogram is minimal relative to baseline (positive endothermic side)
Is estimated from the area between the thermogram between the temperature and the baseline. However, if no endothermic peak is observed on the low temperature side, 50 ° C is used, and if no endothermic peak is observed on the high temperature side, the endothermic end temperature is used.

The copolymer (I) can be obtained by the method described in Japanese Patent Application No. 63-142522. In addition, the copolymer (I)
Can also be obtained by the method described in Japanese Patent Publication No. 46-21212 and the like. When an α-olefin having 6 or more carbon atoms is used, it is preferable to use a catalyst described in JP-A-60-226514.

(2) Copolymer (II) The copolymer (II) of ethylene and an α-olefin having 3 to 10 carbon atoms used in the present invention has a density of 0.910 or more and less than 0.930 g / cm ³ . And 1 in the heating thermogram measured by the differential scanning calorimeter (DSC).
It is necessary that an endothermic peak is observed above 10 ° C.

As the α-olefin, propylene, 1-butene,
Examples thereof include 1-hexene, 4-methyl-1-pentene, 1-octene and the like, and α-olefins having 4 or more carbon atoms, particularly α-olefins having 6 to 8 carbon atoms, are preferred.

The density is measured after annealing at 100 ° C. for 1 hour according to JIS K6760. When a copolymer having a density of less than 0.910 g / cm ³ is used, the stiffness of the film is weakened, and the film is easily blocked. The copolymer (II) used in the present invention is
In the heating thermogram, one or more endothermic peaks must be observed at 110 ° C. or higher, preferably 115 ° C. or higher. Unless the endothermic peak is observed above the above temperature, excellent hot tack properties cannot be obtained. 110
It is preferred that the heat absorption is observed at a temperature range below ° C., it is preferred ratio ΔH _L / ΔH _T to the total endothermic amount [Delta] H _T in this case 110 below ° C. endothermic amount [Delta] H _L is 0.8 to 0.2.
The method of obtaining the temperature rise thermogram, the method of estimating the endothermic amount of the endothermic peak, and the like are the same as those described for the copolymer (I).

The copolymer (II) can be selected from those produced as linear low-density polyethylene. Examples of the production method are described in JP-A-52-103485 and JP-A-56-99209.
No., etc.

(3) Polyethylene composition The composition of the present invention is composed of the above-mentioned copolymer (I) and the above-mentioned copolymer (II), but is further branched to improve moldability and transparency. Other polymers may be contained, such as 1 to 40% by weight, preferably 5 to 30% by weight of low density polyethylene. The composition of the present invention can be obtained by kneading at a temperature not lower than the temperature at which all components are melted. As the kneading device, any of a batch type or a continuous type, a single-screw or a multi-screw screw type can be used, and a screw-type extruder in a molding device such as a film manufacturing device can also be used.

The melt flow rate of the composition of the present invention (measured in accordance with JIS K6760, hereinafter abbreviated as MFR) is not particularly limited, but may be usually selected from the range of 0.1 to 100 g / 10 minutes. 0.1 for blown film applications
It is common to choose an MFR within the range of 1 to 20 g / 10 minutes for T-die film or extrusion laminating applications.

The composition of the present invention can contain known additives such as an antioxidant, a weathering agent, a lubricant, an anti-blocking agent, an antistatic agent, an antifogging agent, a dripless agent, a pigment, and a filler.

Since the composition of the present invention exhibits excellent hot tack properties in the form of a thin film such as a film, it is suitably used not only in the form of a single-layer film but also in the form of a composite film with another substrate. As the base material, polyamide, polyester,
It can be selected from any polymer capable of forming a film such as polypropylene, polyvinylidene chloride, ethylene / vinyl alcohol copolymer, various adhesive polymers, cellophane, paper, paperboard, woven fabric, aluminum foil and the like. In the case of a composite film, a layer comprising the composition of the present invention is preferably present on at least one surface in order to exhibit an excellent hot tack property which is a feature of the present invention.

<Examples> Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof.

Examples 1 and 2 and Comparative Example 1 (1) Production of copolymer (I) Dissolve predetermined ethylene and 1-butene in n-hexane in the lower part of a tank reactor with an internal volume of 200 liters and a stirrer The solution was n-hexane 80 kg / hour, ethylene 1.4 kg
/ Hour, 1-butene was continuously fed at a rate of 0.6 kg / hour. From a separate line, add vanadyl trichloride to the bottom of the reactor.
02 mg / h, 1.2 mg ethyl aluminum sesquichloride
/ Hr, n-butyl perchlorcrotonate was continuously fed at a rate of 0.72 mg / hr. The temperature inside the reactor was controlled at 40 ° C. by circulating cooling water through a jacket attached to the outside of the reactor. The polymerization solution was continuously withdrawn from the top of the reactor so that the inside of the reactor was always full, the polymerization reaction was stopped by adding a small amount of methanol, and after demonomerization and washing with water, the solvent was steam-stripped. ,
The solid copolymer was taken out and dried at 80 ° C. under reduced pressure to obtain an ethylene-1-butene copolymer (a). The formation rate of the copolymer was 1.4 kg / hour. The density of the copolymer thus obtained was 0.906 g / cm ³ , and the MFR was 2.1 g / 10 minutes. The endothermic peak in the DSC heating thermogram was 9
Observed only at 2.9 ° C. (ΔH / ΔH _T = 1). As a differential scanning calorimeter, DSC-7 manufactured by Perkin Elmer Co., Ltd. was used, and a test piece for measurement was used by cutting out about 10 mg from a sheet having a thickness of about 0.5 mm created by a hot press.

(2) Production of composition and film The copolymer (a) obtained in the above (1) and Sumitomo Chemical Co., Ltd.
L-LDPE manufactured by Co., Ltd. with a density of 0.921 g / cm^Three, MFR
Which is an ethylene-1-hexene copolymer of 1.9
Sen Mixed with α prototype (A) at the ratio shown in Table 1.
Spiral die with die diameter 125mm and die lip 2.0mm
And a one-stage air ring with iris
Using an inflation molding machine K-40R
Extrusion speed, die set temperature of 170 ° C, blow-up ratio of 1.8
A film having a thickness of 30 μm was obtained. Composite fill shown below
The film used to manufacture the
Surface tension will be 42 ~ 45dyne / cm by Rona treatment machine
Corona treatment was applied.

 Sumikasen used here Complete fusion of α prototype (A)
In the DSC thermogram measured after slow cooling after dissolution
Endothermic peaks are observed at 107.7 ° C and 121.1 ° C,
The endotherm less than 59.8% of the total endotherm.
(ΔH_L/ H_T= 0.598).

A sample having a width of 2 cm was cut out in a processing direction (MD) or a direction perpendicular to the direction (TD) of the thus obtained film, attached to a tensile tester at a distance between chucks of 6 cm, pulled at a speed of 5 mm / min, and stretched by 1%. 1% secant modulus from the stress at the time
It was calculated by the formula of 100 × (stress) / (cross-sectional area). The values are shown in Table 1.

(3) Production of composite film Using a desktop test coater manufactured by Yasui Seiki, the film obtained in the above (2) was applied with a urethane-based adhesive so as to have a thickness of ² g / m ² after drying. After being pressed at 40 ° C. at 3 kg / cm ² on a stretched nylon base film,
Dry lamination composite film was obtained by heat aging at 0 ° C. for 2 days.

Table 1 shows the hot tack properties of the composite films thus obtained. Hot tack was measured by the following method.

Combine the polyethylene composition layers of the composite film cut to a width of 15 mm, apply a load of 30 g to one side through a pulley, and use a heat sealer manufactured by Tester Sangyo Co., Ltd., and apply a sealing surface pressure of 1.3 kg / cm ² A heat seal having a seal width of 20 mm was performed under the condition of a seal time of 0.3 seconds. Since the load dropped at the same time as the end of the seal, and a peeling force due to the load was applied to the seal surface 0.14 seconds after the end of the seal, the actual peeled length was measured. The same test was performed by changing the temperature of the seal bar (heat sealing temperature) in steps of 5 ° C. The lower the peel length at the lower heat sealing temperature, the better the hot tack.

Examples 3 to 5 (1) Synthesis of vanadium-based catalyst (a) 0.033 mol of vanadium trichloride and 26 mL of n-heptane were added to a 100 mL flask purged with argon, the temperature was raised to 50 ° C, and 0.165 mol of methyl alcohol was added. Then, the mixture was reacted at 50 ° C. for 1 hour with stirring in an argon stream. After the reaction, the supernatant was extracted with a glass filter, washed three times with 25 mL of n-heptane, and dried under reduced pressure to obtain a dark green solid powdery vanadium compound insoluble in n-heptane.

An analysis of the composition of the vanadium compound revealed that vanadium atoms were 21% by weight, chlorine atoms were 42% by weight, and CH3OH was 40% by weight. Therefore, the vanadium compound is VCl ₃ · 3.
It was a compound represented by OCH ₃ OH (m and n of the general formula V (OR) mCl ₃ -m · nROH were 0 and 3.0). Further, no spectrum specific to vanadium trichloride was observed in the X-ray powder spectrum of this compound.

(2) Synthesis of copolymer (b) 60 L of n-hexane was placed in a reactor having an internal volume of 100 L with a stirrer.
3.8 kg of 1-hexene and 400 mL of a 10 wt% hexene solution of ethyl aluminum sesquichloride were supplied. The temperature inside the reactor was raised to 30 ° C. by circulating warm water through a jacket attached to the outside of the reactor. Next, 1.5 kg / cm ² of hydrogen was supplied, and 1.58 g of the vanadium catalyst (a) and 70 mL of a 10 wt% hexane solution of ethyl aluminum sesquichloride were added thereto.
And the polymerization was started. 5 times every 20 minutes
1 mmol / mL n-butyl perchlorocrotonate solution was added in 1.25
mL was added. Ethylene was supplied so that the total pressure became constant during the reaction. The temperature in the reactor was maintained at 30 ° C. by circulating cooling water through the jacket. Two hours after the start of the polymerization, the gas in the reactor was purged, and the content was added to a large amount of methanol to obtain a precipitate. These were filtered and the solid was dried to obtain an ethylene-1-hexene random copolymer (b).

The MFR of the copolymer (b) thus obtained was 1.8
g / 10 min, the density was 0.906 g / cm ³ , and the endothermic peak in the DSC heating thermogram was observed only at 93.8 ° C. (ΔH /
ΔH _T = 1).

(3) Production of composition, film, and composite film Except for using the copolymer (b) obtained in the above (2) in place of the copolymer (a), the composition was the same as in Examples 1 and 2. Products, films and composite films were manufactured. The physical properties are shown in Table 2.

<Effects of the Invention> As described above, according to the present invention, a polyethylene composition which is stiff and has excellent hot tack properties, particularly, a packaging composition exhibiting excellent hot tack properties at low temperatures can be provided.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideaki Koga 5-1 Anesaki Beach, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. (72) Inventor Yuji Shigematsu 5-1 Anesaki Beach, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. (56) References JP-A-3-55233 (JP, A) JP-A-57-34145 (JP, A) JP-A-61-284439 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 23/00-23/36

Claims (1)

(57) [Claims] (1) a density of 0.900 or more and less than 0.910 g / cm ³ ,
In the heating thermogram measured by a differential scanning calorimeter after complete cooling after complete melting, an endothermic peak is observed in the range of 80 to 100 ° C, and the endothermic amount of the endothermic peak is 0.8 or more with respect to the total endothermic amount. Α-olefin content is
2.0 to 10.0 mol% ethylene and 3 to 10 carbon atoms
Having a density of 0.910 or more and less than 0.930 g / cm ³ at a temperature rising thermogram measured by a differential scanning calorimeter of 110 ° C.
A polyethylene composition comprising a random copolymer (II) of ethylene and an α-olefin having 3 to 10 carbon atoms, wherein an endothermic peak is observed as described above.