JP2000086722A - High-density polyethylene resin for injection stretch blow molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-density polyethylene resin for injection stretch blow molding, capable of being subjected to stretch blow molding in a high draw ratio, having excellent surface gloss and buckling strength of molded bottle. SOLUTION: This high-density polyethylene resin for injection stretch blow molding characteristically has (A) 1-15 g/10 minutes melt index at 190 deg.C under 2.16 kg load, (B) 10-14.5 flow ratio and (C) 0.961-0.973 g/cm3 density. The high- density polyethylene resin is suitable for injection stretch blow molding and provides a molded bottle having high rigidity and also excellent environmental stress resistance due to no pinch off. The bottle produced by this invention has extremely improved environmental stress resistance to be a problem in direct blow and the high-density polyethylene resin is a resin capable of sufficiently dealing with lightening of bottle to be required currently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-density polyethylene resin suitable for injection stretch blow molding. More particularly, it relates to a high density polyethylene resin for injection stretch blow molding having a specific melt index, flow ratio and density range.

[0002]

2. Description of the Related Art Polyethylene resin is used as a material for various containers because of its low cost and excellent mechanical strength. Polyethylene resin is widely used in ordinary direct blow bottles, but is currently rarely used in injection stretch blow bottles. However, recent advances in molding techniques and the like have made it possible to perform high-temperature release of the bottomed parison formed in the injection stretch blow molding process, and the injection stretch blow molding of polyethylene resin is now at a stage where it is being put to practical use.

In order to provide a polyethylene resin for injection stretch blow molding, for example, JP-A-59-1400
No. 33 and JP-A-9-194534 disclose polyethylene resins having a large flow ratio. However, when these polyethylene resins are used, unless the draw ratio of the bottomed parison is low, it is difficult to form a stable bottle, and particularly, the surface gloss of the formed bottle becomes poor. Japanese Patent Application Laid-Open No. 9-216915 discloses a low-density polyethylene resin. However, an injection-stretched blow-molded bottle molded using the polyethylene resin has insufficient buckling strength of the bottle. However, there is a problem that the bottomed parison cannot be stretched uniformly because the flow ratio is too small. Therefore, in the conventional injection stretch blow molding using a polyethylene resin, the range of molding conditions is extremely narrow, and commercial production of an injection stretch blow molded bottle has been difficult. Therefore, at present, a high-density polyethylene resin for injection stretch blow molding has not been provided which is satisfactory in terms of moldability, appearance such as surface gloss, and mechanical strength of a bottle.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention is capable of performing injection blow molding at a high draw ratio, and is excellent in surface gloss and buckling strength of a molded bottle. An object is to provide a high-density polyethylene resin for molding.

[0005]

The present inventors have made intensive studies on high-density polyethylene resin for injection stretch blow molding and found that the following high-density polyethylene resin for injection stretch blow molding can solve the above-mentioned problems. Heading,
The present invention has been completed. That is, the present invention provides: (A) a melt index at a load of 2.16 kg at 190 ° C. of 1 to 15 g / 10 min. (B) a flow ratio of 10 to 14.5 (C) a density of 0.961 to 0.973 g / cm ³ , a high-density polyethylene resin for injection stretch blow molding.

Hereinafter, the present invention will be described in detail. The high-density polyethylene resin for injection stretch blow molding of the present invention is an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, preferably 4 to 20 carbon atoms,
Particularly, an ethylene homopolymer is preferable from the buckling strength of the bottle. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, butene-1, pentene-1,3-methylbutene-1, hexene-1,4-methylpentene-1, octene-1, decene-1, tetradecene-1, hexadecene-1, octadecene-1, eicocene-1. Can be used. Further, vinyl compounds such as vinylcyclohexane or styrene and derivatives thereof can also be used. Also,
If necessary, a ternary random polymer containing a small amount of a non-conjugated polyene such as 1,5-hexadiene and 1,7-octadiene may be used.

The density of these ethylene homopolymers or ethylene copolymers is 0.961 to 0.973 g / cm ³ ,
Preferably from 0.962~0.970g / cm ^3.
The density of the strand obtained at the time of the melt index measurement was 100 ° C. in accordance with JIS-K-7112.
And then left to cool for 1 hour at room temperature.
This is a value measured with a density gradient tube. When the density of the polyethylene resin is less than 0.961 g / cm ³ , the buckling strength of the bottle is insufficient. Further, high density polyethylene resin having a density exceeding 0.973 within the range of the melt index of the present invention cannot be produced at present.

The high-density polyethylene resin for injection stretch blow molding of the present invention has a melt index (MI _2.16 ) at 190 ° C. under a load of 2.16 kg of 1 to 15 g / 10.
Min, preferably 3 to 12 g / 10 min, more preferably 4 to 10 g / 10 min. When the MI _2.16 is less than 1 g / 10 min, the fluidity in injection molding is insufficient. Particularly in the case of a multi-cavity mold, there is a problem that high-density polyethylene resin is not uniformly filled in each mold. appear. On the other hand, if it exceeds 15 g / 10 minutes, the viscosity of blow molding of the bottomed parison will be insufficient, and if stretch blown, the problem will occur that the side surface of the bottomed parison will be easily broken by the air pressure of the blow.

The high-density polyethylene resin for injection stretch blow molding of the present invention has a specific flow ratio. The flow ratio used in the present invention is the ratio of the melt index (MI _11.2 ) under a load of 11204 g at a temperature of 190 ° C. to the melt index (MI _1.12 ) under a load of 1120 g. The range of the flow ratio of the high-density polyethylene resin for injection stretch blow molding of the present invention is narrow, from 10 to 14.5, preferably from 12 to 12.
~ 14. Beyond this range, the bottomed parison will not elongate uniformly, and the molded bottle will have thicker and thinner portions, resulting in uneven pressure on the bottle. Conversely, even when the flow ratio is less than this range, the bottomed parison does not elongate uniformly, and the formed bottle has thick spots.

As a method for controlling the flow ratio of these high-density polyethylene resins, a method of polymerizing a high-density polyethylene polymer with a specific catalyst or a method of subjecting a high-density polyethylene polymer to a slight cross-linking reaction with a peroxide or the like. Etc. In consideration of economy and the like, a method of directly polymerizing and manufacturing a high-density polyethylene resin having this fluid ratio with a specific catalyst is preferred. When producing a high-density polyethylene resin having the fluidity ratio of the present invention using a specific catalyst, if the molecular weight distribution of the high-density polyethylene resin ranges from 3.5 to 5 as one standard, the fluidity ratio of the present invention can be improved. Control of high-density polyethylene resin having In addition, even if the molecular weight distribution of the produced high-density polyethylene resin is out of the above range, the flow ratio of the present invention can be satisfied by a slight crosslinking reaction of peroxide or the like.

[0011] The molecular weight distribution of the high density polyethylene resin is measured by gel permeation chromatography. The measuring device used was 150-CA manufactured by Waters.
LC / GPC, AT-8 manufactured by Shodex
07S and Tosoh TSK-gelGMH-H6 in series, using trichlorobenzene as the solvent, 140
Measure in ° C.

The high-density polyethylene resin used in the present invention is not particularly limited to a production method as long as it has a specific density, a melt flow index and a flow ratio. For example, high-density polyethylene resin is a specific Zigraina nata catalyst,
It is adjusted by a chromium catalyst and a specific metallocene catalyst. The metallocene catalyst is a catalyst prepared by a combination of a titanium or zirconium metallocene compound and a promoter. In particular, in the present invention, a metallocene catalyst is preferably used, and the high-density polyethylene resin polymerized by the metallocene catalyst exhibits a crystallization behavior suitable for the stretching blow step. That is, the crystallization rate of the obtained high-density polyethylene resin is lower than that of the high-density polyethylene resin obtained by using a Zigguranatta catalyst or a chromium catalyst, so that the bottomed parison does not rapidly solidify because it is slow.
There is an advantage that the shrinkage of the bottomed parison is small. The high-density polyethylene resin of the present invention may be blended with a polyethylene resin obtained by polymerization with the above catalyst.

The metallocene catalyst is a catalyst comprising a metallocene compound and a co-catalyst. Metallocene compounds are those substituted by at least one cyclopentadienyl group, substituted cyclopentadienyl group, hydrocarbyl silicon, etc., and those in which the cyclopentadienyl group is cross-linked by oxygen, nitrogen and phosphorus atoms. Is a known metallocene compound. The cocatalyst general formula C ⁺ A ^- is represented by, C ⁺ is an organic compound, a Bronsted acid comprising a oxidizing cationic organometallic compound or an inorganic compound, or a Lewis base and a proton acid, metallocene distribution Reacts with the ligand anion to form a cation in the metallocene compound. Examples of the metallocene compound for producing the high-density polyethylene resin of the present invention include, for example, a titanium compound η-bonded to a cyclopentadienyl or substituted cyclopentadienyl group represented by the following general formula.

[0014]

Embedded image

Here, Ti is a titanium atom in an oxidation state of +2, +3, +4, Cp is a cyclopentadienyl or substituted cyclopentadienyl group that is η-bonded to titanium, X1 is an anionic ligand, X2 is a neutral conjugated diene compound. n + m is 1 or 2, Y is —O—, —S—, —NR— or —PR—, and Z is SiR ₂ , CR ₂ , SiR ₂ —SiR ₂ , CR ₂ C
R ₂ , CR = CR, CR ₂ SiR ₂ , GeR ₂ , BR ₂
R is hydrogen, hydrocarbyl in each case,
It is selected from silyl, germum, cyano, halo or combinations thereof and combinations thereof having up to 20 non-hydrogen atoms.

The substituted cyclopentadienyl group includes 1
Species or higher C1-C20 hydrocarbyl, C1-C20 halohydrocarbyl, Cyclopentadienyl substituted by halogen or C1-C20 hydrocarbyl-substituted Group 14 metalloid group , Indenyl, tetrahydroindenyl, fluorenyl or octafluorenyl, preferably having 1 to 1 carbon atoms
6 is a cyclopentadienyl group substituted by an alkyl group.

As X1 and X2, for example, in the above formula, when n is 2, m is 0 and the oxidation number of titanium is +4, X1 is selected from methyl and benzyl, and when n is 1 and m is 0, If the oxidation number of titanium is +3, X1 is 2- (N, N
If the oxidation number of titanium is +4, then X1 is 2-butene-1,4-diyl, and if n is 0, m is 1 and the oxidation number of titanium is +2, X
2 is 1,4-diphenyl-1,3-butadiene or 1,3-pentadiene.

The co-catalyst includes a borate compound. Examples of borate compounds include triphenyl (hydroxyphenyl) borate, diphenyl di (hydroxyphenyl) borate, triphenyl (2,4-dihydroxyphenyl) borate, and tri (p-tolyl)
(Hydroxyphenyl) borate, tris (pentafluorophenyl) (hydroxyphenyl) borate, tris (2,4-dimethylphenyl) (hydroxyphenyl) borate, tris (3,5-dimethylphenyl) (hydroxyphenyl) borate, tris ( 3,
5-Difluoromethylphenyl) (hydroxyphenyl) borate, tris (pentafluorophenyl) (2-hydroxyethyl) borate, tris (pentafluorophenyl) (4-hydroxybutyl) borate, tris (pentafluorophenyl) (4 -Hydroxy-cyclohexyl) borate, tris (pentafluorophenyl) (4- (4 ^, -hydroxyphenyl) phenyl) borate, tris (pentafluorophenyl) (6-hydroxy-2naphthyl) borate, and most preferably tris (pentane) Fluorophenyl) (4-hydroxyphenyl) borate.

Examples of the counter cation of the borate compound include a carbonium cation, a tropylluium cation, an ammonium cation, an oxonium cation, a sulfonium cation, and a phosphonium cation. In addition, metal cations and organic metal cations whose self-confidence is easily reduced can also be mentioned. Specific examples of these cations include triphenylcarbonium ion, diphenylcarbonium ion, cycloheptatrinium, indenium, triethylammonium, tripropylammonium, tributylammonium, dimethylammonium, dipropylammonium, dicyclohexylammonium, and trioctylammonium. N, N-dimethylammonium, diethylammonium, 2,4,6-pentamethylammonium, N, N-dimethylbenzylammonium,
Di- (i-propyl) ammonium, dicyclohexylammonium, triphenylphosphonium, triphosphonium, tridimethylphenylphosphonium, tri (methylphenyl) phosphonium, triphenylphosphonium ion, triphenyloxonium ion, triethyloxonium Um ion, pyrium, silver ion, gold ion, platinum ion, copper ion, palladium ion, mercury ion, and ferrocenium ion. Of these, ammonium ions are particularly preferred.

The method for polymerizing the high-density polyethylene resin of the present invention is not particularly limited, and examples thereof include a fluidized bed gas phase method, a slurry method, and a bulk polymerization method. The high-density polyethylene resin of the present invention includes a phenol stabilizer and / or an organic phosphite stabilizer, and / or an organic thioether stabilizer and / or a stabilizer such as a metal of a higher fatty acid, a pigment, a dye,
Nucleating agents, lubricants, inorganic fillers such as carbon black, talc, and glass fibers or compounding agents added to polyolefins such as reinforcing materials, flame retardants, and neutron blocking agents are added within a range that does not impair the purpose of the present invention. be able to.

Examples of the phenolic stabilizer include 2,6-di-t-butyl-4-methylphenol, 2,6-di-cyclohexyl-4-methylphenol, 2,6-diisopropyl-4-ethylphenol, 2,6-Di-t-amyl-4-methylphenol, 2,6-di-t-octyl-4-n-propylphenol, 2,6-dicyclohexyl-4-n-octylphenol, 2-isopropyl-4-methyl -6-t-butylphenol, 2-t-
Butyl-2-ethyl-6-t-octylphenol, 2
-Isobutyl-4-ethyl-6-t-hexylphenol, 2-cyclohexyl-4-n-butyl-6-isopropylphenol, tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrocinnamate )
Methane, 2,2'-methylenebis (4-methyl-6-t
-Butylphenol),

4,4'-butylidenebis (3-methyl-
6-t-butylphenol), 4,4′-thiobis (3
-Methyl-6-t-butylphenol), 2,2′-thiobis (4-methyl-6-t-butylphenol),
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxyphenyl) benzylbenzene, 1,3,5-tris (2-methyl-4-hydroxy-5-t-butylphenol) methane, tetrakis (methylene (3,5-di-butyl) -4-hydroxyphenyl) propionate) methane, β- (3,5-di-tert-butyl-4-hydroxylphenol) propionic acid alkyl ester, 2,2′-oxamidebis (ethyl-3- (3,5-di -T-butyl-4-hydroxyphenyl) propionate, tetrakis (methylene (2,4-di-t-butyl-4-hydroxyl) propionate), n-octadecyl-3- (4 ^, -hydroxy-3,5-di -T-butylphenyl) propionate, 2,6-di-t-butyl-p-cresol, 2,
4,6-tris (3 ′, 5′di-tert-butyl-4′-hydroxybenzylthiono-1,3,5-triazine,
2,2′-methylenebis (4-methyl-6-t-butylphenol),

4,4'-methylenebis (2,6-di-t
-Butylphenol), 2,2′-methylenebis (6-
(1-methylcyclohexyl) -p-cresol), bis (3,5-bis (4-hydroxy-3-t-butylphenyl) butyric acid) glycol ester,
4′-butylidenebis (6-t-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-tris (2 , 6-Dimethyl-3-hydroxy-4-t-butylbenzyl) isocyanurate, 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl)
-2,4,6-trimethylbenzene, 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanate, 1,3,5-tris ((3,5-
Di-tert-butyl-4-hydroxyphenyl) propionyloxyethyl) isocyanurate, 2-octylthio-4,6-di (4-hydroxy-3,5-di-tert-butyl) phenoxy-1,3,5 -Triazine, 4,4 '
-Thiobis (6-t-butyl-m-cresol) and the like.

As the organic phosphite-based stabilizer, trioctyl phosphite, trilauryl phosphite,
Tridecyl phosphite, octyl-diphosphite,
Tris (2,4-di-t-butylphenyl) phosphite, triphenylphosphite, tris (butoxyethyl) phosphite, tris (nonylphenyl) phosphite, distearylpentaerythritol diphosphite, tetra (tridecyl)- 1,1,3-Tris (2-
Methyl-5-t-butyl-4-hydroxyphenyl) butanediphosphite, tetra (tridecyl) -4,4 '
-Butylidenebis (3-methyl-6-tert-butylphenol) diphosphite, tris (3,5-di-tert-butyl-4-hydroxyphenyl) phosphite, tris (mono or dinonylphenyl) phosphite, hydrogenated-
4,4'-isopropylidene diphenol polyphosphide, bis (octylphenyl) bis (4,4'-butylidenebis (3-methyl-6-t-butylphenol)) 1,6-hexaneol diphosphide, phenyl- 4,4'-isopropylidene diphenol pentaerythritol diphosphide, bis (2,4-di-t-
(Butylphenyl) pentaerythritol diphosphide, bis (2,6-di-t-butyl-4methylphenyl) pentaerythritol diphosphide, tris ((4,4′-isopropylidenebis (2-t-butylphenol)) Phosphide, di (nonylphenyl) pentaerythritol diphosphide, tris (1,3-
Di-stearoyloxyisopropyl) phosphite,
4,4'-isopropylidenebis (2-t-butylphenol) di (nonylphenyl) phosphide, 9,10
-Di-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, tetrakis (2,4-di-t
-Butylphenyl) -4,4'-biphenylenediphosphide and the like.

Examples of the organic thioether-based stabilizer include dialkylthiopropionates such as dilauryl-, dimyristyl- and distearyl-, and butyl-, octyl-, and the like.
Esters of polyhydric alcohols of alkylthiopropionic acids such as lauryl-, stearyl-, etc. (for example, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, trishydroxyethylisocyanurate), for example, pentaerythitol tetralaurylthiopropio Nate). More specifically, dilauryl thiopropionate, dimyristyl thiopropionate, distearyl thiodipropionate,
Lauryl stearyl thiodipropionate, distearyl thiodibutyrate and the like can be mentioned.

Examples of the metal salts of higher fatty acids include alkaline earth metal salts such as magnesium, calcium and barium salts of higher fatty acids such as stearic acid, oleic acid, lauric acid, caprylic acid, arachidic acid, palmitic acid and behenic acid. , Cadmium salts, zinc salts, lead salts, sodium salts, potassium salts, lithium salts and the like. Magnesium stearate, magnesium laurate, magnesium palmitate, calcium stearate calcium oleate, barium stearate, barium laurate, barium laurate, magnesium, zinc stearate, zinc calcium oleate, zinc stearate, zinc laurate, Lithium stearate, sodium stearate, sodium palmitate, sodium laurate, potassium stearate, potassium laurate, calcium 12-hydroxystearate, etc.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to examples and the like, but these do not limit the scope of the present invention. MI _2.16 ; 190 according to ASTM-D-1238.
This is a value measured at a temperature of 2.degree. Flow ratio; temperature 190 according to ASTM-D-1238
Melt index (MI _11.2 ) at 11204 g load at 100 ° C and melt index at 1120 g load
(MI _1.12 ). Density: The strand obtained at the time of the melt index measurement was measured at 100 ° C. for 1 strand in accordance with JIS-K-7112.
After a heat treatment for an hour, and then left to cool for 1 hour at room temperature, it was measured with a density gradient tube.

Injection stretch blow molding: The bottomed parison is stretched 4 times in length and 2 times in width by using an injection stretch blow molding machine (SBIII-250P-50) manufactured by Aoki Solid Laboratory Co., Ltd. A square bottle having a diameter of 20 mm and an internal volume of 800 ml was formed. The surface gloss of the molded bottle was measured with a gloss meter manufactured by Nippon Denshoku Industries Co., Ltd. The thickness unevenness was measured by measuring the thickness of the bottle side surface, measuring the thickness of the thickest portion and the thickness of the thinnest portion, and evaluating the ratio. The greater the ratio, the greater the thickness unevenness. The compression speed was 10 mm / min using a compression tester.
To determine the load at the time of 4 mm deformation, and the buckling strength of the bottle was evaluated.

[0029]

Examples 1 to 4 Triethylammonium tris (pentafluorophenyl) (4-hydroxyphenyl) borate and titanium (N-1,1-dimethylethyl) dimethyl (1- (1,2,3,4,5,-) et
a) -2,3,4,5-tetramethyl-2,4-cyclopentadien-1-yl) silanaminato) ((2-)
Using a metallocene catalyst having N)-(η ⁴ -1,3-pentadiene) supported on silica, ethylene and hydrogen were supplied to the reactor at 75 ° C. in hexane. The resulting high-density polyethylene resin was extruded to produce ethylene homopolymers shown in Table 1. In any of the examples, the high-density polyethylene resin can be molded without any problem, and the molded bottle has small thickness unevenness, glossiness, and excellent buckling strength.

[0030]

Comparative Examples 1 to 3 According to the production method of Example 1, high-density polyethylene resins of Comparative Examples 1 to 3 shown in Table 1 were produced.
Injection stretch blow molding was performed in the same manner as in Example 1 using the obtained high-density polyethylene resin. In Comparative Example 1, the melt index was low, the flow of the injection process was insufficient, and as a result, residual strain remained in the bottomed parison,
When the bottomed parison was released from the mold at high temperature, the bottomed parison deformed. In Comparative Example 2, the viscosity of the bottomed parison was insufficient, and the bottomed parison was broken during blowing. In Comparative Example 3, the buckling strength was extremely reduced due to the low density.

[0031]

Comparative Example 4 A high-density polyethylene resin shown in Table 1 was produced using a well-known Ziegler-Natta catalyst. The resulting high-density ethylene resin had a large flow ratio and the bottomed parison was not stretched uniformly.

[0032]

Comparative Example 5 An ethylene homopolymer was produced by bulk polymerization using methylalumoxane and bis (n-butylcyclopentadienyl) zirconium dichloride.
In the obtained high-density polyethylene resin, the flow ratio is small and the bottomed parison is not stretched uniformly. Further, despite the ethylene homopolymer, the density is low, and the buckling strength of the bottle is insufficient.

[0033]

[Table 1]

[0034]

The high-density polyethylene resin of the present invention is suitable for injection stretch blow molding, and the molded bottle has high rigidity and no pinch-off, so that it has excellent environmental stress resistance. The bottle formed by the present invention has a remarkably improved environmental stress resistance, which is a problem in direct blowing, and is a resin that can sufficiently cope with the demand for lighter bottles in recent years.

Continued on the front page F term (reference) 4F208 AA05A AA05C AG07 AH55 AR15 AR17 AR18 LA05 LB01 LG01 4J100 AA02P AA03Q AA04Q AA07Q AA09Q AA15Q AA16Q AA17Q AA19Q AA21Q CA01 CA04 DA15 DA36 DA42 FA10 JA58

Claims (4)

[Claims] (A) Melt index at 190 ° C. under a load of 2.16 kg: 1 to 15 g / 10 min. (B) Flow ratio: 10 to 14.5 (C) Density: 0.961 to 0.973 g / cm ³ , a high density polyethylene resin for injection stretch blow molding. 2. The high density polyethylene resin for injection stretch blow molding according to claim 1, wherein the high density polyethylene resin is an ethylene homopolymer. 3. The high density polyethylene resin for injection stretch blow molding according to claim 1, wherein the molecular weight distribution is from 3.5 to 5. 4. The high-density polyethylene resin for injection stretch blow molding according to claim 1, wherein the high-density polyethylene resin is produced using a metallocene catalyst.