JPS61241339A - polyethylene composition - Google Patents

Abstract

PURPOSE:A composition, obtained by incorporating LDPE with an ethylene-alpha- olefin copolymer having melting characteristics in a specific amount, having improved low-temperature heat sealability, low-temperature impact resistance, etc., and suitable to laminated films for food packaging etc. CONSTITUTION:A polyethylene composition obtained by incorporating (A) 95-40 pts.wt., preferably 85-50pts.wt. low-pressure-processed low-density polyethylene having 1-40g/10min melt flow rate and 0.913-0.935g/cm<3> density with (B) 5-60pts.wt., preferably 15-50pts.wt. copolymer of ethylene and a 4-10C alpha- olefin, e.g. 1-butene, in a small proportion having 0.01-50g/10min melt flow rate, 0.87-0.905g/cm<3> density, <=40 composition distribution determined by the formula, <=2 average chain length ratio of methylene groups and 105-125 deg.C maximum melting point measured by a differential scanning calorimeter.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to polyethylene compositions passed through extrusion laminates. More specifically, the present invention relates to a polyethylene composition suitable for obtaining a laminate material having excellent low-temperature heat roll properties, low-temperature impact resistance, interlayer adhesion, and stress crack resistance.

[Conventional technology]

The coating material for composite films made by extrusion coating is polyethylene made by high pressure method, so-called LDPR.
is used in the largest amount as a sealant because of its good low-temperature heat-sealability and excellent processability.

However, since LDPE is inferior in heat seal strength, hot tack properties, etc., attempts have been made to improve or replace LDPH. Materials that can replace LDPH include high-density polyethylene (HDPt) and polypropylene (PP).
), ethylene-vinyl acetate copolymer (1!VA),
Although some ionomers are used, HDPII!
PP has excellent heat sealing strength, but poor low temperature heat sealing properties, large neck-in, and poor processability; PP has strong heat sealing strength, but is susceptible to surging during extrusion processing (
In addition, there are processing disadvantages such as thermal decomposition, a tendency to reduce molecular weight, and large neck-in. EvA has excellent low-temperature sealing properties, but has a unique odor, and ionomers have poor heat seal strength and hot tack properties. Although it is excellent, the load during extrusion processing is large and the processability is poor (all materials have their advantages and disadvantages, so none of them can be said to be optimal.

[Problem that the invention seeks to solve]

In view of this situation, the present inventor has developed a polyethylene composition with excellent moldability suitable for obtaining a laminated base fabric with excellent low-temperature heat sealability, low-temperature impact resistance, interlayer adhesion, stress crack resistance, and odorlessness. As a result of various studies to obtain L
Ethylene with specific composition distribution and melting characteristics for DPR
It has been found that the above object can be achieved by adding an α-olefin copolymer, and the present invention has been achieved.

[Means for solving problems]

That is, the present invention provides: (a) /71/door o-rate (ASTM D 1
238. E') is 1 to 40 g/10min
95 to 40 parts by weight of high-pressure low-density polyethylene,
and (bl melt flow rate) (ASTM D 123
8.E”) is 0.01 to 50 g/Logi
n, density 0.870 to 0.905 g/c+4
, a composition distribution parameter (U) of 40, an average chain length ratio of methylene groups of 2.0 or less, a maximum melting point measured by a differential scanning calorimetry needle of 105 to 125°C, and a small proportion of α having 4 to 10 carbon atoms. -Copolymers with olefins a3)5
The present invention provides a polyethylene composition characterized in that it comprises from 60 parts by weight to 60 parts by weight.

[For production]

Melt flow rate used in the present invention) (MFR:ASTM
D 123B, E”) is 1 to 40g/10m1
High-pressure polyethylene (A) (LDPB (9)) of n is a polyethylene with a normal density of 0.913 to 0.935 g/aj obtained by polymerizing ethylene by so-called high-pressure radical polymerization.
, preferably in the range of 0.915 to 0.930 g/aJ, and preferably has an MFR of 3 to 30 g/10
It is from m1n.

Note that LDPR (A) in the present invention includes not only an ethylene homopolymer but also a small amount of other polymerizable monomers within a range that does not impair the purpose of the present invention, for example, 20% by weight or less, such as propylene, 1 - It may be a copolymer of ethylene and butene, vinyl acetate, acrylic ester, etc.

1 liter of ethylene/α-olefin copolymer used in the present invention
B) is defined by the following (a) to (f).

(B) Melt flow rate) (MPR: ASTM 0
123B, H) from 0.01 to 50 g/10m
1n, preferably in the range of 0.1 to 20g/10ml. If the MFR is outside the above range, the melt viscosity is either too low or too high, resulting in poor moldability.

(b) Density is 0.870 to 0.905 g/aJ
, preferably in the range of 0°880 to 0.900 g/cd. If the density is less than 0.870 g/ctA, blocking resistance and slip resistance are poor, so it is not preferable, and if it exceeds 0.905 g/aJ, it may be necessary to improve low-temperature heat sealability, impact resistance, interlayer adhesion, etc. Less effective. The density in the present invention is a value measured according to ASTM D 1505.

(c) The composition distribution has a composition distribution parameter (U) expressed by the following formula (1) of 40 or less, preferably 30 or less.

U=toox (Cw/Cn-1)...(1)
However, in the formula, Cw represents the weight average degree of branching and Cn represents the number average degree of branching.

If U exceeds 40, the composition distribution is wide, and the effect of improving transparency, tear resistance, impact resistance, low temperature heat sealability, interlayer adhesion, etc. is inferior. 0 Cw and Cn in the present invention are measured by the following method. This is the value. That is, ethylene α-
In order to perform compositional fractionation of the olefin copolymer (El), the copolymer (B) was dissolved in a mixed solvent of p-xylene and butyl cellosolve (volume ratio: 80/20), and diatomaceous earth (El) was dissolved in a mixed solvent of p-xylene and butyl cellosolve (volume ratio: 80/20).
Product name: Celite #560 John Manpil Co. (USA)
A cylindrical column was filled with the cylindrical column coated with the above-mentioned mixed solvent, and while a solvent having the same composition as the mixed solvent was transferred into the column and flowed out, the temperature inside the column was increased from 30°C to 1°C in 5°C increments.
The ethylene copolymer coated by raising the temperature stepwise to 20°C was fractionated, reprecipitated in methanol, filtered and dried to obtain a fractionated product. Next, the number of branches C per 1000 carbons of each fraction is determined by the "C-NMR method, and the number of branches C and the cumulative weight fraction 1 (w) of each fraction are calculated using the following lognormal distribution (Equation (2) ), C- and Cn were determined by the least squares method.

β:1=21n (C-/Cn) ・------(
3), and Co is expressed as C□ −Cw ·Cn −−−−−−= (4).

In addition, the number of branches C according to the 13C-NMR method is G, J, Ra
y.

P.E. Johnson and J.R.Knox+
Macros + oracles.

10 773 (1977),
"It was determined from the area intensity using the methylene carbon signal observed in the c-NDp spectrum.

(d) The average chain length ratio of methylene groups is 2.0 or less, preferably I. 7 or less.

The average chain length ratio is a parameter indicating the random structure of ethylene and α-olefin in the molecular chain of the ethylene/α-olefin copolymer used in the present invention, and is ) together with copolymer [F]
) is one of the important characteristics that specifies the structure of and,
Copolymers in which the average chain length ratio of methylene groups is too large, exceeding 2.0, have improved effects on transparency, tear resistance, impact resistance, low-temperature heat sealability, interlayer adhesion, stress crack resistance, etc. There is no.

In addition, in the present invention, the average chain length ratio of methylene groups is 'C
- Methylene average chain length calculated from the degree of branching measured using NMR and block methylene average chain calculated excluding cases where the number of methylenes between branches (between two adjacent branches) is 6 or less This is a value determined from the length ratio, that is, block methylene average chain length/methylene average chain length.

(e) The ethylene/α-olefin copolymer (B) used in the present invention has one melting point, preferably a plurality of melting points, as measured by DSC, and if there is a plurality of melting points, the highest melting point is 105 to 100. 125°C, preferably in the range of 110 to 120°C.

Those with a maximum melting point of less than 105°C have good blocking resistance,
Poor slip properties, large neck-in, poor melt flowability (and poor moldability).

On the other hand, if the temperature exceeds 125° C., there is no effect of improving transparency, tear resistance, impact resistance, low temperature heat sealability, glabella adhesion, and stress crack resistance.

The highest melting point in the present invention was determined using DSC with a sample of 3 mg.
After melting at 200℃ for 5 minutes, the cooling rate was 10'C/m
The temperature was lowered to 20'C with i. The peak or shoulder on the highest temperature side was defined as the highest melting point. If the highest melting point appears as a peak, the temperature at the peak, and if it appears as a shoulder, the highest melting point is the temperature at the intersection of the points of contact drawn at the inflection point on the high temperature side and the inflection point on the low temperature side of the shoulder.

(f) It is a random copolymer having a substantially linear structure in which the α-olefin copolymerized with ethylene is an α-olefin having 4 to 10 carbon atoms. Specifically, the α-olefin having 4 to 10 carbon atoms is, for example, 1-
Butene, l-hexene, 4-methyl-1-pentene, 1
-hebutene, 1-octene, 1-decene and mixtures thereof. The content of α-olefin component units constituting the ethylene/α-olefin copolymer of the present invention is:
The amount is arbitrary as long as it satisfies the density and composition distribution specified by (b) to (d) above, but it is usually in the range of 3 to 25 mol%, preferably 5 to 20 mol%.

of the ethylene/α-olefin copolymer used in the present invention)
has a melting point as in the characteristic (e) above,
Although the polymer itself has some crystallinity, its degree of crystallinity is usually in the range of 5 to 60%, preferably 10 to 50%. The degree of crystallinity of the ethylene/α-olefin copolymer [F]) is a value determined by X-ray diffraction. The measurement method used a straight line connecting the diffraction angles of 7° to 31.5° as the background, and the rest was carried out in accordance with the method described in the following literature. S.L.Aggrwal an.
d G, P, Ti1ley+ J.

Po1)+n+, Sci,, ljl, 17 (19
55).

of the ethylene/α-olefin copolymer used in the present invention)
can be produced, for example, by the following method. For example, by treating with a highly active solid component (al is alcohol ~) having a specific surface area of 50♂/g or more and containing titanium, magnesium, and halogen as essential components. titanium catalyst component (c) obtained by (c), organoaluminum compound catalyst component) and halogenated hydrocarbons such as ethyl chloride, isopropyl chloride, or silicon tetrachloride.
Using a catalyst formed from zero halogen compound catalyst component that can be used as a halogenating agent in step 3), ethylene and α-olefin are copolymerized to a predetermined density.

At this time, if part or all of the organic aluminum compound catalyst component 03) is a halogen compound, the use of the halogen compound catalyst component (O) can be omitted. Patent application No. 58-196081
I am familiar with

The polyethylene composition of the present invention comprises 95 to 40 parts by weight of the LDPE, preferably 85 to 50 parts by weight, and 5 to 6 parts of the ethylene/α-olefin copolymer.
0 parts by weight, preferably 15 to 50 parts by weight (total 100 parts by weight)
(parts by weight). If the amount of the ethylene/α-olefin copolymer (El) is less than 5 parts by weight, low-temperature heat-sealability, low-temperature impact resistance, interlayer adhesion, and stress crack resistance will not be improved, while if it exceeds 60 parts by weight, Slip properties, blocking resistance, and heat resistance decrease, necking also increases, and high-speed workability decreases.

To obtain a film from the polyethylene composition of the present invention,
After mixing the LDPR (A) and the ethylene/α-olefin copolymer (B) in the above range using, for example, a V-blender, ribbon blender, Henschel mixer, tumbler blender, etc., directly by a normal film forming method, For example, a method of obtaining a film by the T-Gouy method, an inflation method, or a method of forming a film by using the above-mentioned mixture mixed with an extruder, Nigoo, Banbury mixer, etc. and then granulated can be adopted.

In addition, the composition of the present invention may be used by adding weathering stabilizers, heat stabilizers, antistatic agents, antifogging agents, antiblocking agents, slip agents, lubricants, pigments, dyes, droplet agents, etc. to ordinary polyolefins. Various compounding agents may be blended within the range that does not impair the purpose of the present invention.

The composition of the present invention has excellent transparency, bending resistance, and impact resistance as a film, so it can be used for wrapping films for food packaging, stretch films, shrink films, general packaging films, and other packaging films, and for agricultural use. It can be used as a film or a protective film, but by taking advantage of its low-temperature heat-sealability and laminating it with various base materials, packaging films suitable for various uses can be obtained.

As the base material, any polymer having film-forming ability, paper, aluminum foil, cellophane, etc. can be used. Examples of such polymers include high-density polyethylene, medium- and low-density polyethylene, ethylene/vinyl acetate copolymer, ethylene/acrylic acid ester copolymer, ionomer, polypropylene, and polyethylene.
Olefin polymers such as 1-butene and poly-4-methyl-1-pentene, vinyl copolymers such as polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylate, and polyacrylonitrile, nylon 6, nylon 66,
Nylon 7, Nylon 101 Nylon 11, Nylon 1
2. Polyamides such as nylon 610 and polymethaxylylene adipamide, polyesters such as polyethylene terephthalate, polyethylene terephthalate/isophthalate, and polybutylene terephthalate, polyvinyl alcohol, ethylene/vinyl alcohol copolymers, and polycarbonates. These base materials can be appropriately selected depending on the purpose and the item to be packaged. For example, in the case of foods that are easily packaged with corrosion, resins with excellent transparency, rigidity, and gas permeation resistance such as polyamide, polyvinylidene chloride, ethylene/vinyl alcohol copolymer, polyvinyl alcohol, and polyester are recommended. selected. For confectionery, textile packaging, etc., polypropylene or the like with good transparency, rigidity, and water permeation resistance can be selected as the outer layer. Further, if the base material is a polymer, it may be uniaxially or biaxially stretched.

Methods for producing a composite film laminated with the base material using the composition of the present invention include dry lamination,
Various known methods such as extrusion lamination, sandwich lamination, and coextrusion may be employed.

〔Effect of the invention〕

The polyethylene composition of the present invention has low motor load, resin pressure, etc. in an extrusion molding machine, low neck-in, and excellent moldability, and the obtained film has low-temperature heat sealability, low-temperature impact resistance, interlayer adhesion, etc. Since it has excellent stress crack resistance and transparency, it is used in various laminating films by taking advantage of its properties as a sealant material such as divalent salt heat sealability. In addition, various packaging films can be produced by extrusion coating on various substrates or by coextrusion molding with the substrate.
For example, it can be used for food packaging such as snacks, instant noodles, dried foods such as shaved bonito flakes, water foods such as miso, pickles, soups, frozen foods, etc., as well as packaging for liquid transportation due to its excellent impact resistance and bending resistance. Alternatively, by taking advantage of the interlayer adhesive properties, it can be suitably used as a sandwich laminate base material for various base materials and sealant materials.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way unless the gist of the invention is exceeded.

Example 1 Catalyst Preparation> Under a nitrogen atmosphere, 1 mol of commercially available anhydrous magnesium chloride was suspended in dehydrated and purified hexane 2i, 6 mol of ethanol was added dropwise over 1 hour with stirring, and the mixture was reacted for 1 hour at room temperature. . 2.6 mol of diethylaluminum chloride was added dropwise to this at room temperature, and stirring was continued for 2 hours. Next, after adding 6 moles of titanium tetrachloride, the system was heated to 80° C. and the reaction was carried out with stirring for 3 hours. The solid portion after the reaction was separated and washed repeatedly with purified hexane. The solid (A-
The composition of 1) was as follows.

3.7 67.0 20.0 0.4 4.8 Next,
To 50 mmol of Ti in A-1 suspended in purified hexane, 500 mmol of ethanol was added at room temperature, the temperature was raised to 80° C., and the mixture was reacted for 1 hour. After the reaction, the temperature was lowered to room temperature, 150 mmol of triethylaluminum was added, and the reaction was carried out with stirring for 1 hour.The solid portion after the reaction was washed repeatedly with purified hexane. The composition of (B-1) was as follows.

2.8 59.3 13.7 0.5 23.6*) The produced solid was decomposed and extracted with H2O-acetone, and then quantified as ethanol using gas chromatography.

Polymerization> Using a continuous polymerization reactor with an internal volume of 2,001 liters, dehydrated and purified hexane was dehydrated to 1,004 liters of hexane. /hr, ethylaluminum sesquichloride 15 mmol/hr, the catalyst (B-1) obtained above was continuously supplied at a rate of 1.0 mmol/hr in terms of Ti, and at the same time in the polymerization vessel, Ethylene 10kg/hr, 1-butene 33kg/hr.

Hydrogen was continuously supplied at a rate of 201/hr, the polymerization temperature was 150°C, the total pressure was 30 kg/aJ, the residence time was 1 hour, and the copolymer concentration with respect to the solvent hexane was 100 g/J! Copolymerization was carried out under the following conditions. Catalytic activity is 13. OOOg
- copolymer/mmol-Ti.

The obtained ethylene/1-butene copolymer (Il!BC-
The physical properties of 1) are M F R: 2.2g/10+sin
, density 0.889g/cdSU: 23, average chain length ratio of methylene groups: 1.26, highest melting point: 118.2
(there were other peaks at 72.0°C and 103.5°C), crystallinity: 18.4%, and 1-butene content: 9.7 mol%.

<Film forming> EBC-1: 10 parts by weight and MFR near, 2 g/10
m1n and density: 0.917 g/aJ high pressure low density polyethylene (LDPR): 90 parts by weight were mixed in a Henschel mixer, and then the mixed composition-■ was mixed with 65 m
Melt with n + φ extruder (set temperature: 350℃), width 50
Extruded through a 0n++w T-die (set temperature: 320°C), using an 800III wide laminator,
Biaxially oriented polyethylene terephthalate film (0
-Pf! T, thickness 8128 m) and a non-oriented polypropylene film < cpp, thickness 830 μm) were laminated. The thickness of the composition was 15 μm. The moldability during extrusion lamination and the laminated film were evaluated by the following method.

Extrusion amount of Netsuin 2 composition: Processing speed 120 m/wi
Neck-in width of one ear under the condition of n × film thickness 15 μm (
+am) is measured.

Maximum processing speed: At the above extrusion rate, the processing speed was increased until the molten film of the composition broke, and the maximum processing speed (m/5 inch) was measured.

Peel strength: A test piece with a width of 15 mm was cut from the laminated film, and the composition layer and CPP layer were peeled off at a tensile speed of 300 wui/sin, and the strength at that time was defined as the peel strength.

The results are shown in Table 1.

Example 2.3 The same procedure as in Example 1 was carried out except that the mixing ratio of HBC-1 and L[)PR used in Example 1 was used as shown in Table 1. The results are shown in Table 1.

Comparative Example 1.2 MFR obtained using vanadium catalyst instead of EBC-1 used in Example 1 and Example 2: 3-9 g
/10m1n, density: 0.886g/aj, maximum melting point: 68°C (single peak), crystallinity: 8.3% and 1
-Butene content: The same procedure as in Example 1 and Example 2 was performed except that 10.5 mol % of ethylene/1-butene random copolymer (HBC-2) was used. The results are shown in Table 1.

Claims (1)

[Claims] (1) (a) Melt flow rate (ASTM D123
8. 95 to 40 parts by weight of high-pressure low density polyethylene (A) containing 1 to 40 g/10 min of E), and (b)
Melt flow rate (ASTM D1238, E) is 0
．． 01 to 50g/10min, density 0.870 to 0.905g/cm^2, composition distribution parameter (U
) is 40 or less {however, U = 100 x (weight average degree of branching/number average degree of branching - 1)}
, a copolymer of ethylene and a small proportion of an α-olefin having 4 to 10 carbon atoms, which has an average chain length ratio of methylene groups of 2.0 or less and a maximum melting point of 105 to 125°C as measured by differential scanning calorimetry. A polyethylene composition comprising parts by weight.