JP2805944B2 - Polyethylene mixture - 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. In addition, in order to be able to cope with changes in sealing conditions, it is desired that the sealing temperature range in which the peeling of the seal does not occur is wide.

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 has even better hot tack properties than L-LDPE, especially a seal temperature range where the peeling of the seal is small is wide both on the low temperature side and on the high temperature side. It is in.

<Means for Solving the Problems> The present inventor has studied in detail the mechanism of the development of hot tack property, which is an important property in polyethylene for packaging, and has two or more polyethylene components each having a specific thermal transition behavior. A polyethylene composition consisting of three types,
It has been found that the stiffness and excellent hot tack properties, especially the seal temperature range where the peeling of the seal is small is wide both on the low temperature side and on the high temperature side.

That is, the present invention relates to: (a) a density of 0.890 or more and less than 0.910 g / cm ³ , a temperature rising thermogram measured by a differential scanning calorimeter after complete melting and then gradually cooling, within a range of 80 to 100 ° C. An endothermic peak is observed, the endothermic amount of the endothermic peak is 0.8 or more with respect to the total endothermic amount, ethylene having an α-olefin content of 2.0 to 10.0 mol% and α-olefin having 3 to 10 carbon atoms.
Random copolymer with olefin, (b) density 0.910
Is less than 0.945 g / cm ³ , and an endothermic peak is observed at 110 ° C. or more and less than 125 ° C. in a heating thermogram measured by a differential scanning calorimeter, and ethylene and carbon number 3 to
(C) a density of 0.945 g / cm ³ or more, and an endothermic peak observed at 125 ° C. or more in a temperature rising thermogram measured by a differential scanning calorimeter. Of a homopolymer of ethylene or a random copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and based on 100 parts by weight of (a), (b) and (c), ) Is from 1 to 50 parts by weight and (c) is from 1 to 40 parts by weight.

 Hereinafter, each item will be described in detail.

(1) Component (a) Component (a) used in the present invention is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, the density of which is 0.890 g / cm ³ or more, and Less than 0.910 g / cm ³ , an endothermic peak was observed in the range of 80 to 100 ° C. in a heating thermogram (a diagram showing the relationship between endothermic rate and temperature) measured by a differential scanning calorimeter (DSC). The endothermic amount of the endothermic peak needs to be 0.8 or more with respect to the total endothermic amount.

As the α-olefin, propylene, 1-butene,
Examples thereof include 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 0.890 or more and less than 0.910 g / cm ³ , excellent hot tack properties cannot be obtained. 0.89
The density is preferably 0 g / cm ³ or more, more preferably 0.895 g / cm ³ , and particularly preferably 0.900 g / cm ³ or more.

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 component (a) used in the present invention needs to have an endothermic peak in the temperature range of 80 to 100 ° C., preferably in the range of 85 to 95 ° C. in the thermogram thereof. 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, the total endothermic amount of an endothermic amount [Delta] H _A of the endothermic peak observed in the temperature range Δ
The ratio ΔH _A / ΔH _TA to H _TA needs to be 0.8 or more, preferably 0.9 or more. [Delta] H _TA from the area between the heating thermogram and the base line, [Delta] H _A each between the endothermic peak observed adjacent to the hot side and cold side of the outdoor temperature range should be present endothermic peak The heating thermogram is estimated from the area between the thermogram and the baseline between the temperatures at which the baseline shows a local minimum (taking the endothermic side positive). 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 (a) can be obtained by the method described in Japanese Patent Application No. 63-142522. Further, the copolymer (a)
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) Component (b) The component (b) used in the present invention is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, having a density of 0.910 or more and 0.945 g / cm Less than ³ , preferably less than 0.940 g / cm ³ , and 100 ° C. or more in a heating thermogram measured by a differential scanning calorimeter (DSC).
It is necessary that an endothermic peak is observed below 25 ° 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.

The component (b) used in the present invention must have one or more endothermic peaks at 100 ° C. or higher, preferably 105 ° C. or higher, and lower than 125 ° C., and preferably lower than 120 ° C. in the temperature-rising thermogram. It is. Unless the endothermic peak is observed above the above temperature, excellent hot tack properties cannot be obtained. When another endothermic peak is observed outside the above temperature range, the ratio of the endothermic amount ΔH _B of the endothermic peak observed within the above temperature range to the total endothermic amount ΔH _TB is ΔH _B / ΔH _TB of 0.8.
Above, more preferably 0.9 or more. In addition,
The method of obtaining the temperature rising thermogram, the method of estimating the endothermic amount of the endothermic peak, and the like are the same as those described for the component (a).

Component (b) can be selected from those produced as linear low-density polyethylene, and examples of the production method are described in JP-A-52-103485, JP-A-56-99209 and the like. However, according to the method exemplified in the description of the component (a), the ratio of α-olefin to ethylene and the molecular weight of hydrogen and the like to be supplied to the reaction system are adjusted so as to satisfy the requirements of the component (b). It is preferable to use one manufactured by changing the concentration or the like of the agent.

(3) Component (c) Component (c) used in the present invention is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and has a density of 0.945 g / cm 3. be ^three or more, it is necessary that the endothermic peak is observed in the 125 ° C. or higher at Atsushi Nobori thermogram as measured by differential scanning calorimetry (DSC).

As the α-olefin, propylene, 1-butene,
Examples thereof include 1-hexene, 4-methyl-1-pentene, and 1-octene, and an α-olefin having 4 or more carbon atoms is preferable.

The density is measured after annealing at 100 ° C. for 1 hour according to JIS K6760.

The component (c) used in the present invention needs to have one or more endothermic peaks at 125 ° C. or higher in its temperature rise thermogram. Unless the endothermic peak is observed above the above temperature, excellent hot tack properties cannot be obtained. When another endothermic peak is observed outside the above temperature range, the ratio of the endothermic amount ΔH _C of the endothermic peak observed within the above temperature range to the total endothermic amount ΔH _TC ΔH _C / ΔH _TC is 0.8 or more, and Is preferably 0.9 or more. 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 component (a).

Component (b) can be selected from those manufactured as high density polyethylene (HDPE).

(4) Mixing ratio In the present invention, the mixing ratio of each component is (a), (b)
(B) is 1 to 50 parts by weight, preferably 5 to 40 parts by weight, and (c) is 1 to 40 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of (c). . When the component (b) is contained within the above range,
Hot tack at high temperatures is better than when this component is not contained. On the other hand, when the component (b) is contained beyond the above range, the hot tack at low temperatures is inferior. When the component (c) is contained beyond the above range, the hot tack at low temperatures is inferior and the transparency is deteriorated. Component (c) is preferably contained at the point of the film's waist.

(5) Polyethylene mixture The mixture of the present invention comprises the above components (a) and (b) or these and component (c), but is further branched to improve moldability and transparency. 1 to 40% by weight, preferably 5 to 30% by weight of low density polyethylene
Other polymers may be contained, for example. The composition of the present invention can be obtained by kneading at a 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 (measured in accordance with JIS K6760, hereinafter abbreviated as MFR) of the mixture of the present invention 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 mixture 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 mixture 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) Synthesis of vanadium catalyst (I) 0.033 mol of vanadium trichloride and 26 mL of n-heptane were added to a 100 mL flask purged with argon, and the temperature was raised to 50 ° C. 0.165 mol was added, and 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.
The compound was represented by 0CH ₃ OH (m and n of the general formula V (OR) mCl ₃ -m · nROH are 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 (A) 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 (I) and 70 mL of a 10 wt% hexane solution of ethylaluminum 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 (A).

The MFR of the copolymer (A) 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 _A
/ ΔH _TA = 1).

(3) Production of copolymer (B) The above-mentioned procedure was repeated except that the supply of 1-hexene was changed to 1.6 kg and the supply of hydrogen was changed to 2.0 kg / cm2 in the preparation of copolymer (A) of (2). In the same manner as in (2), an ethylene-1-hexene random copolymer (B) having an MFR of 2.5 g / 10 minutes and a density of 0.918 g / cm ³ was obtained. The endothermic peak in the DSC heating thermogram was observed only at 110.4 ° C (ΔH _B / ΔH _TB
= 1).

(4) Production of mixture and film The copolymers (A) and (A) obtained in (2) and (3) above
And (B) and HDPE manufactured by Nissan Maruzen Polyethylene
0.950g / cm^Three, Nissan Polyethylene with MFR of 1.0
Len 1010 and the ratio shown in Table 1
125mm, 2.0mm spiral dies and air lips
Pkolar inflation with one-stage air ring
Using an extrusion molding machine K-40R, an extrusion speed of 24 kg / hour, 17
30 ° m thickness at die set temperature of 0 ° C, blow-up ratio of 1.8
A film was obtained. Used to manufacture the following composite films
Film is transferred to a corona treatment machine
The corona treatment so that the surface tension is 42 to 45 dyne / cm.
Was applied.

 Nissan polyethylene used here 1010 is infrared
Ethylene-1-butene copolymer was determined by absorption spectrum analysis.
DSC temperature rise measured after complete melting and slow cooling
Endothermic peak in thermogram observed only at 133.2 ° C
Was done.

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.

(5) Production of composite film Using a desktop test coater manufactured by Yasui Seiki, the film obtained in (4) above was coated 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 mixture layers of the composite film cut out to a width of 15 mm, apply a load of 30 g to one side via a pulley, and use a tester Sangyo Co., Ltd. heat sealer, seal surface pressure 1.3 kg / cm ² , Heat sealing with a sealing width of 20 mm was performed under the condition of a sealing 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.

<Effects of the Invention> As described above, according to the present invention, there is provided a polyethylene mixture which is stiff and has excellent hot tack properties, particularly less peeling of the seal from low to high seal temperatures, and is most suitable for packaging applications. be able to.

Claims (1)

(57) [Claims] (1) a density of 0.890 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
Random copolymer with α-olefin of (b) density
0.910 or more and less than 0.945 g / cm ³ , and 110 ° C. or more in a heating thermogram measured by a differential scanning calorimeter.
Ethylene with an endothermic peak below 25 ° C and 3 carbon atoms
(C) a density of 0.945 g / cm ³ or more, and an endothermic peak observed at 125 ° C. or more in a heating thermogram measured by a differential scanning calorimeter Of a homopolymer of ethylene or a random copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and (a), (b) and (c), with respect to a total of 100 parts by weight, A polyethylene mixture wherein b) is 1 to 50 parts by weight and (c) is 1 to 40 parts by weight.