JPS58103542A - Cap for containers for carbonated beverages - Google Patents

Abstract

PURPOSE:To provide the titled cap having excellent creep and stress crack resistance, by using a PE compsn. comprising a specified PE and an ethylene/alpha- olefin copolymer. CONSTITUTION:A PE compsn., MFR2 (melt flow rate measured at 190 deg.C under the total load of 2.16kg) of 0.3-30g/10min, density of 0.945-0.965g/cm<2> and high shearing flow rate (HSFR) of 600sec<-1>, obtained by mixing 20-70wt% PE, MFR2 of 5-2,000g/10min and density of 0.965-0.975g/cm<3>, with 80-30wt% ethylene/alpha-olefin copolymer, MFR2 <=15g/10min, MFR10 (melt flow rate measured at 190 deg.C under the total load of 10.0g) <=15g/10min and density of 0.890- 0.950g/cm<3>, is used to make a cap for containers for carbonated beverages. EFFECT:A cap having excellent sealing performance and shock resistance without deformation by internal pressures or external forces and free from gas leakage from sealing section may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to caps for carbonated beverage containers.Caps for carbonated beverages such as beer and soft drinks have traditionally been made of metal, but attempts have been made in recent years to convert them to caps made of resin. ing.

Carbonated beverage containers are subject to considerable internal pressure, so it is important to select a material for the cap that has strong resistance to impacts and will not cause breakage.At the same time, it is important to select a cap material that will not cause damage, but it is also important to select a cap material that has a strong resistance to impact, etc., and will not cause damage. Must be of good quality. In particular, when thermoplastic resin is used as a cap material, it must be processable so that it can be molded with good dimensional accuracy to fit the seal structure.Furthermore, when storing carbonated drinks, the resin may be deformed due to internal pressure or external force. , no gas leakage from the seal □
) It is also necessary to have good leave properties.

Conventionally, polyethylene compositions obtained by blending or sequentially polymerizing two types of polyethylene (including a copolymer of ethylene and a small amount of a-olefin) with different density and melt flow rate (VFR) have been improved in processability, It has excellent stress crack resistance and impact resistance, and is suitable for pipes, bottles,
Although it is known that they can be used as molded products such as containers, fibers, films, and sheets, many of these known compositions are not necessarily suitable as cap materials for carbonated beverage containers with strict quality requirements. Ta.

The present inventors have investigated materials that are particularly suitable for caps of carbonated beverage containers, and have found that the following polyethylene compositions are excellent, and have completed the present invention.

That is, the present invention provides (A) load 2.16 to 9 mel) 7tl-ray) MFR2 of 5 to 2000 g/
10m1n.

20 to 70 parts by weight of polyethylene having a density of 0.965 to 0.975 g/1ys3 and (B) MF
R20,01 stone 0.2 g/10m1n, load 1
Melt 7°-ray at 0.0 kQ) MF R,
o/NF R2 is 15 or less, density 0.890 copolymer 8
L3. consisting of 0 to 30 parts by weight (100 parts by weight in total) and having an MFR2 of 0.3. Og/10w1n,
Density 0.965 to 0.945 g/apt3, H
A cap for a carbonated beverage container characterized by using a polyethylene composition having a FR of 6 D Oaec or more.

Here, MFR2 meets the E conditions of ASTM D-1238-73, i.e. temperature 190'C, total load 2.16kg, M
FR1oN conditions, i.e. humidity 190℃, total load 1
0.0 #g, and H8FR is a value that has a good correlation with spiral flow in injection molding, and was measured using a capillary rheometer under the following conditions.

H8FR measurement conditions Equipment: Shimadzu Cavity Rally type rheometer Nozzle diameter: 1. Ommφ, L/D=30 Temperature 190″C The H8FR value is expressed as the shear rate (s-c) at a shear stress of 2.4×106dyne/3 according to the melt flow curve in FIG.

The component (A) used in the cap of the present invention has an MFR2 of 5
to 2000 g/10m1n, preferably 20 to 1000 g/10m1n, density 0.965
to 0.975 g/C1l' of polyethylene. When the polyethylene having MFR2 smaller than the above is used, the H8FR of the composition is 6008θc.
-1 or more, as component (B) MFR1o/
It is necessary to use a thick MFR2, and as a result,
The disadvantage is that stress crack resistance is poor. Furthermore, if a polyethylene having an MFR2 larger than the above is used, the impact resistance of the composition will be poor.
In particular, defective welding occurs at the weld part, and when used as a cab, there is a drawback that it is easily damaged by impact. Furthermore, when a polyethylene with a lower density is used, as shown in Figure 3, the composition has poor creep properties and poor stress (resistance to cracking) properties, resulting in poor sealing performance and impact resistance as a cap. cause problems.

On the other hand, the component (B) used in the cap of the present invention is MFR
2 is 0.01 to 0.2 g/10m1n,
Preferably sail 01 to 0.1 g/l 0mtn,
MFR, o/MFR2 is 15 or less, density is 0.890 to 0.950 g/cI11, preferably 0.90
0 to 0.945 g/clR(7) l lene/α-olefin copolymer. Examples of the α-olefin include carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, and 4-methyl-1-pentene. Examples include numbers 3 to 18.

If a component with MFR2 larger than the above is used as the component CB), the composition will have poor creep resistance and stress crack resistance, and when used as a cap, problems such as gas leakage due to creep deformation or cracked foil formation will occur. In addition, using a material with a very high molecular weight, the MFR2 of which is much smaller than the above, is because (8) (B) a good mixing state of both components cannot be obtained, spoiling the appearance of the cap, and causing fusion of the weld part. cause defects. Also, MFR4゜/MFR
If a material in which 2 is larger than the above range is used, the stress crack resistance will be poor. If a material in which the density of component (B) is smaller than the above range is used, "sticking" of the composition pellets and the products will occur. Undesirable.

Furthermore, if a material with a density higher than the above is used, creep resistance and stress crack resistance will still be inferior.

The blending ratio of component (A) and component (B) is (AJ component 20
to 70 parts by weight, preferably 30 to 60 parts by weight, and 80 to 30 parts by weight, preferably 7 parts by weight of component (B).
0 to 40 parts by weight (total 100 parts by weight), and the MFR2 of the composition is 0.3 to 3.0 g / 10
min s preferably 0.5 to 2-0 g/1
0mln, density 0.945 to 0.965g/
C1N, preferably 0.950 to 0.960 g
/ax3, H8FR is 600 sec-' or more, preferably 800 esc or more. If the blending ratio of the component (A) exceeds the above range, a good mixing state will not be obtained and poor weld fusion will result, which is undesirable.On the contrary, the ratio of the component will become smaller than the above range, and the M F of the composition will be reduced.
If the values of R2, density, etc. are smaller than the above ranges, the molding dimensional accuracy and creep resistance will be poor, which is not preferable. In addition, in order to obtain the above-mentioned composition, in the presence of a catalyst formed from a transition metal compound catalyst component and an organometallic compound catalyst component, component (A) is produced, and then component CB) is produced, or (B) After producing the component (A)
Adopting two-stage polymerization, such as the method for producing components, is
(A) and (B) are preferred because a homogeneous mixture of both components can be obtained. However, each component (A) and (B) may be separately produced and then blended using various blending methods.

In manufacturing the cap, additives such as various stabilizers, antioxidants, pigments, etc. may be appropriately added to the above composition.

Caps for carbonated beverage containers are particularly required to be airtight. Its shape and airtight structure can be appropriately selected depending on the shape of the container body and other factors.Hereinafter, it will be explained using examples.

Example 1 (1) Catalyst Synthesis 5 moles of anhydrous magnesium chloride were suspended in 10 g of dehydrated hexane in a nitrogen stream, 25 moles of ethanol was added dropwise over 1 hour with stirring, and the suspension was reacted for 1 hour at room temperature. To this was added dropwise 12 mol of diethylaluminium chloride at room temperature, and the mixture was stirred for 2 hours. Next, titanium tetrachloride 1
After adding 0 mol, the temperature was raised to 60°C and the reaction was carried out with stirring for 3 hours.

The generated solid portion was separated using a tilter, washed repeatedly with purified hexane, and then made into a hexane suspension.

The T1 concentration in the hexane suspension was determined by titration.

Further, when a portion of the obtained solid was dried under reduced pressure and the catalyst composition was examined, it was found that 74 mg of titanium, 202 mg of magnesium, and 618 mg of chlorine were present per gram of the solid.

(2) Polymerization Polymerization of component A and component B for blending was carried out as follows.

A component: 50% dehydrated hexa in a 200% polymerization vessel
6/hr,) ethylaluminum 140 mmol
The supported catalyst was continuously supplied at a rate of 1.4 mmol/hr in terms of T1 atoms, and while the contents of the polymerization vessel were discharged at the required rate and maintained at 80°C, ethylene was added. 1s kg/hr s hydrogen 18Nm/hr
The polymerization was carried out continuously under conditions of a total pressure of 7 to 9/cIII2 and an average residence time of 2 hours.

The MFR2 of the obtained polyethylene was 240 g/10 m1n, and the intrinsic viscosity [η] was 0.73.
The d6/g% density was o, 974 g/g.

Component B: Same as the polymerization of component B, triethylaluminum 75 mmol/hr, catalyst 1 in terms of T1.
, Q mmol/hr, polymerization temperature 70°C.

Ethylene 15&9/hrs 1-butene 750g/hrs
BRS hydrogen was introduced at a rate of 0.080 N rn /hr, and polymerization was carried out continuously under the conditions of a total pressure of 4 kg/(:R2).

MFR2 of the obtained polyethylene is 0.06 g/10 m1n1 (77) is 3.20 dl
/g.

MFR, o/MFR2 is 9.7, density is 0.956g/
cIII (3) Blend The above ingredients and B component powder are blended at a blending ratio of 50150, heat stabilizer and salt M@harvesting agent are added, and mixed in a Henschel mixer.

Next, cross-wire granulation was performed using a 65 mmφ full-flight single-screw extruder.

The obtained ethylene copolymer composition had the following physical properties.

MFR2=0.78g/10m1n, (η)=L96a
g/gs'Ij'lK = 0.955 g/cps
5.asFR=1050sec'Example 2 Using the same catalyst as in Example 1, a continuous series of two-stage polymerization was carried out.

5Ql/h of hexane to the first stage polymerization vessel with an internal volume of 2001
r,) ethylaluminum 140 mmol/hrs
The supported catalyst was continuously fed at a rate of 2.8 m m 01/h1 in terms of T1, and ethylene was fed at 80° C. at 15&9/hr while discharging the contents of the polymerization vessel at the required rate.

Hydrogen was introduced at a rate of 18 N m/hr, with a total pressure of 7
kg/as.

The first stage polymerization is carried out continuously under conditions of an average residence time of 2 hours. Suspension solution of hexane containing polyethylene produced by polymerization (ethylene polymer content 300 g/l, MFR2 of polyethylene = 270 g/10 m1n, intrinsic viscosity [η] =
0.71 dl/g, density = 0.974 g/3.) was introduced into a flash drum at the same temperature, and after separating the hydrogen contained in the solution, the entire amount was directly introduced into the second stage polymerization vessel with an internal volume of 2001. 15 k of ethylene at 70 °C without adding catalyst, feeding 50//hr of purified hexane and discharging the polymerizer contents at the required rate.
ti/hr, 1-butene 650g/hr
The second stage polymerization is carried out continuously under the following conditions: hydrogen is introduced at a rate of 0.075 N m /hr, the total pressure is 5 kg/cm 2 , and the residence time is 2 hours.

The effluent from the second stage polymerization vessel is an ethylene polymer composition of 30%
0g/1l-hr, and the MF R2 of the polymer is 0.
68 g/ 10m1ns ('7) is 2.07 dl/
The g1 density was 0.955 g/cm3.

The physical properties of the second stage polymerization product calculated from the additivity with the first stage physical properties and the conversion formula are as follows: 0 [η) = s, 43al/g MFR2 = 0.043g /10m1n (MFR2=38(η)-5,5) p=0.955g/α3 The polymer was obtained into pellets under the same granulation conditions as in Example 1.

Examples 3 to 7, Comparative Examples 1 to 4 Components A and B obtained by changing the amount of hydrogen and 1-butene supplied and the type of α-olefin as a comonomer in the method of Example 1 were used as examples. An ethylene copolymer composition was obtained by blending in the same manner as in 1.

Comparative Example 5 Component A is polyethylene obtained by the usual continuous polymerization described in Example 1, and is the same material as Component A in Example 3 and Comparative Example 1.

B component: Hexane 6011 in a polymerization vessel with an internal volume of 200 g.
2.8 mmol of supported catalyst in terms of T1, 120 mmol of ethylaluminum, and 0.14N of hydrogen.
m is initially supplied in bulk.

Ethylene 2/;9/hr while keeping the temperature at 85℃
.

Polymerization is carried out by continuously introducing 1-butene at a rate of 80 g/hr.

The first depressurization was performed 3 hours after the start of polymerization. Depicting the decrease in hydrogen. Thereafter, depressurize every 3 hours.

The total polymerization time was 12 hours, and the polyethylene yield was 23 kg.The change in MF R2 after 0 hours and the physical properties of the final product were as follows.

After 6 hours After 6 hours After 9 hours After 12 hours MPR21
50171,30,15 Physical properties, MFR2=0.15 g/10m1n, (
η]=2.70dj? /g, density = 0.938g/cM
1MF R10/MF R2 == 18.5 (2) Blend Blend is made by the method of Example 1 at blend ratio A/B =
I went with 40/60. The obtained ethylene copolymer composition had the following physical properties.

MFR2=0.84 g710min, (η) =
1.96 dl/g1 density = 0.955g/as, H
8FR:=1120sec-1 Examples 7 to 10, Comparative Examples 6 to 1° In the method of Example 2, the ratio of the polymerization amount in the first stage and the polymerization amount in the second stage, the comonomer in the first stage and the second stage supply ratio,
Ethylene copolymer compositions were obtained by varying the type of comonomer and polymerization conditions.

The ethylene copolymer composition was press-molded to a length of 200 m.
A test piece of m x 20 mm x 2 mm was prepared and tested for mechanical properties. The test conditions are as follows: (1) Tensile test ASTM D-638 (2) Izot impact strength ASTM D-256 with notch according to ASTM D-1695.

Temperature: 50°C Surfactant: Antarox A400.10% solution (4) Tensile creep test For the ethylene copolymer compositions of Example 1 and Comparative Example 3: According to AsTM D-674, 80"C, stress 30k
Measure the strain by adding g/lx2. The results are shown in Figure 3.

An injection moldability test was conducted under the following conditions.

(Re-injection molding machine Toshiba l5-50 (2) Spiral 70-test mold R: s mm, semicircular spiral flow mold Mold temperature 40'C Resin temperature 260°C Injection time 5 seconds Cooling time 5 seconds Injection speed High speed (3) shrinkage rate Mold 150X 120X2mm Mold temperature 40℃ Resin temperature 200℃ Injection pressure 1000/800kIj10I2 Injection time 1076 seconds Cooling time 30 seconds Injection speed Low speed shrinkage rate difference (total) Also, under the conditions shown below, the diameter is 50mm, A screw cap with a height of 20 mm and a wall thickness of 2 mm as shown in Figure 1 was injection molded and subjected to a sustained pressure test and a drop strength test.0 Molding machine: Toshiba ZS-50 Resin temperature: 220℃ Mold temperature: 30℃ Injection time 2 seconds injection pressure 1000/800 to 9/2 cooling time
10 seconds (1) Continuous pressure test Coca-Cola 50 cooled in a glass bottle (inner volume 6DJ)
After injecting ml, close it with the above cap with a tightening torque of 15 kg・α. Store 10 specimens per test specimen in an upright position in an air bath at 50°C for 10 days, and inspect for changes in the shape of the cab, presence of cracks, and presence of liquid leakage.

(2) Cap side drop test The above-closed bottle was placed with the cap side down, and 50cI11
Drop it onto a concrete surface and inspect for cracks.

The results are shown in Tables 1 to 3.

[Brief explanation of drawings]

FIG. 1 is an example of a cap, FIG. 2 is a drawing showing the relationship between shear rate and shear stress, and FIG. 3 is a drawing showing an example of a tensile IJ-B curve. Applicant Mitsui Petrochemical Industries Co., Ltd. Agent Kazuzu Yamaguchi 1 0 mm 〈-□ mm

Claims (1)

[Claims] (1) (4) Melt flow rate MFR2 at a load of 2.16 kg is 5 to 2000 g710m1n
, 20 to 70 parts by weight of polyethylene with a density of 0.965 to 0.975 g/♂ and (B) VFR 20,01 to o-2 g/10 m
in, melt flow rate at a load of 10.0 kg)
MFRl. / M F R2 is 15 or less, density 0.890 to 0
．． It consists of 80 to 30 parts by weight (total 100 parts by weight) of an ethylene/α-olefin copolymer of 950 g/cII3, and has a VFR2 of 0.3 to 3.0 g/1.
0mln, density 0.945 to 0.965g 7c
m3, high shear 7t17-1z -) H8FR is 60
A cap for a leg acid drink container characterized by using a polyethylene composition of 0 sec-1 or more.