CA2040083A1 - Polyolefinic composition having oxygen barrier property, as well as sheet and container made of said composition - Google Patents

Abstract

ABSTRACT
The improved resin composition comprising a polyolefin, an oxidation catalyst and 0 - 500 ppm of a radical inhibitor can be used to fabricate a sheet and a container that have good oxygen barrier quality on its own without being combined with expensive other resins that have oxygen barrier quality.

Description

2 ~

POLYOLEFINIC COMPOSITION HAVING OXYGEN BARRIER
PROPERTY, AS WELL AS SHEET AND CONTAINER
MADE OF SAID COMPOSITION

This invention relates to a polyolefin containin~
resin composition, as well as a sheet and a container that are made o~ said resln compositlon and that have an oxygen barrier property. This inventlon also relates to a process ~or producing such a sheet and container havlng an oxygen barrler property.
PolyoleEins are thermoplastic and can be shaped by various techniques including melt extrusion, inJection molding and blow moldlng. In addition, polyoleflns are inexpensive. Because of these advantages, polyolefins are extensively used as materials for packaging films and sheets, as well as ln the manu~acture of bottls and other containers.
A maJor disadvantage of polyoleflns ls their high oxygen permeabllity, so in order to package foods and other materlals that dislike oxygen, they have to be used in lamination wlth other reslns that are expenslve and tha~
have an oxygen barrler property, as exempllfied by ethylene/vinyl acetate copolymers and polyvinylidene chloride.
.

The present invention has been accomplished under these circumstances and has as an ob~ect providlng a polyolefinic resin composition that exhibits an e~fective oxygen barrier property on its own without using expensive other resins that have oxygen barrier quality.
Another obJect of the present invention is to provide a sheet having oxygen barrier quality using said polyolefinic resin composition.
A further ob~ect of the present invention is to provide a process for producing said sheet.
Still another ob~ect of the present invention is to provide a container havlng oxygen barrier quality using said polyolefinic resin composition.
Yet another ob~ect of the present invention is to provide a process for producing said container.
As a result of the intensive studies conducted in order to attain these ob~ect, the present inventors ~ound that they could be attained by a polyole~lnic resin composition comprislng a polyole~ln, an oxldatlon catalyst and O - 500 ppm of a radical inhlbitor, an oxy~en barrier sheet made of that composition, an oxygen barrier container made of that composition, as well as processes for producing that oxygen barrier sheet and container.

t~3 Any oxldation catalyst can be used ln the present invention as long as it promotes the oxidation o~
polyole-fins with oxygen, whereby the oxy~en that would otherwise penetrate or permeate through the polyolefin o~
interest is reacted with the latter to reduce its oxy~en permeability and hence improve its oxygen barrier quality.
Metal catalysts made of transition metals in a compound form are preferably used as such oxidation catalysts. The ions of transition metals, as they make a transition from the oxidized to reduced state and vice versa, permit oxygen to react with polyolefins and this would be the mechanism by which those transition metals work as oxidation catalysts.
Preferred examples of transition metals that can be used in the present invention include Co, Mn, Fe, Cu, ~i, Ti, V and Cr, with Co being particularly preferred.
Compounds o~ these metals include salts with organlc aclds such as stearic acid, acetylacetonic acld, ,~
dimethyldithiocarbamic acld, linoleic acid and naphthenic acid.
Aluminum compounds can also be used as oxidation catalysts in the present invention because of their many advantages including cleanness, colorlessness and low cost.

0 ~ 3 The oxidation catalysts described above are pre-~erably containined in the polyolefinic cornposition in amounts Or at least 100 ppm in terms o-f the weight o-f metal atoms.
~rom the viewpoint o-f oxygen barrier quality, those oxidation catalysts are pre-ferably contained in high concentrations but if their content is excessive, rapid oxygen absorption leads to the deterioration o e polyolefins, which will cause ha~e, lower strength and other defects in sheets and otherwise shaped parts o-f polyolefins. Therefore, to avoid these prob:lems, oxidation catalysts are preferably used in anmounts not exceeding 2,000 ppm in the polyolefinic compos:Ltion.
Radical inhibitors are typically used in polyolefinic resins in order to prevent the generation of radicals or -to eliminate the rad:Lcals once formed. However, the use of such radlcal inhib:Ltors is either ent:lrely avo:lded or limited to a content of 500 ppm in the resLn composLt:Lon O-e the present invention. Radical lnhib:Ltors that may be used ln the present invention are classified into ~our major types: a static heat stabilizer that inhibits a radical reaction (oxidation reaction) by adding hydrogen atoms to the radicals generated ln an oxidation reaction; a dynamic heat stabilizer that decomposes and consumes peroxides to prevent the generation of radicals, thereby inhibiting an oxidation reaction; a radical trapping a~ent that acts on generated radicals ln such a way that they are reactlvely bonded together to inhlbit an oxldation reaction; and a uv absorber that absorbs the energy o~ light to become a compound in the excited state, which reverts back to the initial ground state upon releasin~ the absorbed energy o~
light, thereby preventing the photo-excited generation o-f radicals.
A speci~ic example of the dynamic heat s$abilizer is tris~2,4-dl-t-butylphenyl)phosphite (IRGAFO~ 168 of CIBA-GEIGY Corp.) Specific examples of the static heat stabilizer include: triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate] (IRGANOX 245 of CIBA-GEIGY
Corp.), 1,8-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenylpropionate] (IRGANVX 259 o~ CIBA-GEIGY Corp.), 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanllino)-1,3,5-trlazine (IRGANOX 565 o~ CIBA-GEXGY Corp.), pentaerythrityltetraquisr3-(3,5 di-t-butyl-4-hydroxyphenyl)propionate](IRGANOX 1010 o~ CIBA-GEIGY
Corp.), 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)Propionate~ (IRGANOX 1035FF of CIBA-GEIGY
Corp.), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (IRGANOX 1076 of CIBA-GEIGY
Corp.), N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-*Trade-mark hydrocinnamide (IRGANOX 1098 of CIBA-GEIGY Corp.~, 3,5-di-t-butyl-4-hydroxy-benzylphosphonate-diethyl ester (IRGANOX
1222 of CIBA-GEIGY Corp.), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (IRGANOX 1222 of CIBA-GEIGY Corp.), bis ~ethyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate)calcium (IRGANOX 1425WL of CIBA-GEIGY Corp.), tris~3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate (IRGANOX 3114 of CIBA-GEIGY Corp.), octylated diphenylamlne (IRGANOX 5057 of CIBA-GFIGY Corp.), and 2,4-bisl(octylthio)methyl]-o-cresol tIRGANOX 5057 of CIBA-GEIGY
Corp.) Specific examples of the radical trapping ~gent lnclude: the polycondensation product of dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine (TINUVIN 622LD of CIBA-GEIGY Corp. ), poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2-4-diyl}~(2,~,6,6-tetramethYl-4-piperidyl)iminohexamethylene ~CHIMASORB* 944FL of CIBA-GEIGY Corp. ), and the condensation product of N, N ' -bis t 3-aminopropyl)ethylenediamlne and 2,4-bis[N-butyl-N-~1,2,2,6,6-pentamethyl-4-plperidyl)amino]-6-chloro-1,3,5-triazine (CHIMASORB ll9FL of CIBA-GEIGY Corp. ) Specific examples of uv absorbers include 2-(5-methyl-2-hydroxyphenyl)benzotriazole (TIN W IN PFL o~ CIBA-* Trade-mark 2 ~ g 3 GEIGY Corp.), 2-[2-hydroxy-3,5-bis(~,2-dimethylbenzyl)penyl]-2H-benzotr:Lazole (TINUVI~ 23~ of CIBA-GEIGY Corp.), 2,-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole (TINUVI~ 320 o-f ~IB~-GEIGY
Corp.), 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole (TINUVIN 326 o~ CIBA-GEIGY Corp.), 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole (TINUVIN 327 of CIB~-GElGY Corp.), 2-(3,5-di-t-amyl-2-hydroxyphenyl)ben~otriazole (TINUVIN 328 of CIBA-GEIGY
Corp.), and 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole (TINUVIN 329 of CIBA-GEIGY Corp.) The polyole-finic composition does not contain those radical inhibitors or contains them in amounts of up to 500 ppm, pre-ferably up to 100 ppm. When the con-tent O-e radical inhibitors in the polyole-einic composition exceeds 500 ppm, they will inhibit the oxidation reaction O-e polyole-fins and the reaction -for oxygen absorpt:Lon :Ls inh:Lb:Lted to Increase the oxygen permeab:Llity of the polyo:Le-eins. It shou:Ld be part:Lcularly noted that commercial polyolee:Lns are not pre-ferred -for the purposes o-f the present invention since radical inhibitors are incorporated in large amounts in order to prevent deterioration that would otherwise occur during thermal formation o~ the polyole-~ins.
Polyole-fins that can be used in the present inven-tion include polyethylenes such as low-density polyethylene, 2 ~ C~

medium-density polyethylene and high-dens:ity polye-thylene, polypropylene, polybutene, polypentene, e-thylene-propy:l.ene copolymers, ethylene-butene copolymers, and ethy]ene-pentene copolymers. From the viewpoint o-f oxygen barrier quality, homo- and copolymers o-f propylene monomers are pre-ferred.
The polyolefinic composition o-f the present invention may also contain other thermoplastic resins than polyole-fins.
The résin composition o-f the present invention can be shaped into sheets, containers and other packaging materials by means of various ~chermal forming techn:iques, such as melt extrusion molding -for making -films, sheets and pipes, injection molding -for making containersl and blow molding -for making bottles and other hollow containers.
Blow molding can be per-formed in two diffe~ent waYs, one being an extrusion blow molding process which consLsts of making a parison by extruslon mo:Lding and thern blow:Lng :i.t, and the other being an inJection blow molding process which consists of making a pre-form by inJection molding and then blowing it.
Another preferred method consists o-f mixing a metal catalyst with a polyolefin of interest, leaving the mixture to stand until the polyole-fin is oxidized, blending the 2~0~3 resulting composition with another polyole-fin, and extrusion-molding the blend into a sheet.
The resin composition o-f the present invention can be shaped at temperatures in the range o-f 200 - 320C which is customarily used in the thermal -formation o-f polyole-fins.
I-f necessary, shaping temperatures o-f up to about 350~ can be employed. Generally, polyolefins are thermally -formed at comparatively low temperatures in order to prevent thermal deterioration that would otherwise take place during forming. In the present invention, however, there is no need to consider thermal deterioration since the oxidation catalyst will decompose upon heating to promote the generation of radicals and this enables the resin composition to be shaped at fairly high temperatures.
The thickness o-f the shaped article is pre-ferably at least 50 l~m, more pre-ferably at least 100 llm, most preferably a~ least 400 )Im. Thicknesses less than 50 11~1 are insufficient to achleve the desired oxygen barr:Ler qua:LLt~.
The sheet, packaging material, container and other shaped articles of the resin composition of -the presen-t invention may be single-layered or, alternatively, they may be laminated with other various layers. A polyolefin layer containing an oxidation catalyst decomposes by absorbing oxygen during standing over time and experiences deterioration as manifested by reduced strength or bleeding due to -the formation o-f m:Lcro-crystals. In order -to avoid these problems and malnta:ln the overall strength o-f a container, the polyolefin layer is preferably laminated with a shape-retaining resin layer made o-f a material that will not deteriorate in strength over time. If a transition metal is used as the oxidation catalyst, the inside sur-face of a -food packaging material or container is pre-ferably laminated w~th a transition metal -free layer in order to avoid direct contact with the food contents. In a pre-eerred embodiment, one or both sides o-f the polyole-fin layer containing an oxidation catalyst are laminated with a layer of another thermoplastic resin such as one that does no-t contain an oxidation catalyst. Layers o-f other thermoplastic resins that can be used include ~those which are made o-f polyesters, polyole-fins, polyami.des, polyvinyl chloride, polyvinylidene chloride, polyacrylonitri.le, polycarbonates or modi~ied products thereo-f. The polyo:lefln layer contain:Lng an ox:Ldat:lon cata:Lyst and laye:rs of other thermop:lastic resins can be laminated by var:Lous methods including lam:i.nation using adhesives, coextrusion, co-inJection molding, co-extrusion blow molding, and co-inJection blow molding.
The polyole-finic resin composition o-f the present can be used in many and various applications as described below. ~irst, they may be used as container materials for 2 ~

storing -foods and other articles that w:L:L1 be readily denatured by oxygen. In this case, as already mentioned, foods and other contents are pre-ferably prevented -erom contact with transition metals by providing transition metal free resin layers on the inner sur-face of the container. Sheets or -films of the resin composition can be used as bag materials, blister pack materials or the lid Oe containers. Pipes o-f the resin composition can be used as containers by sealing the opening at both ends with a suitable means such as a ~etallic lid. InJection molded containers or bottles may be immediately used as practical containers.
In the present inventlon, films, sheets, containers, bottles and other articles shaped from the polyole-finic resin composition of the present invention may be exposed to radiations or subJected to a corona discharge treatment so as to enhance and improve the oxygen barr:Ler performance o-f the composition. Preferred radiatLons suitab:le -f`or th:Ls purpose include ~-rays, ~-rays, ~-rays, X-rays and electron beams, with the last mentioned electron beams being particularly preferred for several reasons includin~ the convenience of equipment and the procedural sa-fety.
Exposure to electron beams means accelerating thermions at high voltage in vacuo and applying them onto an article o-f interest. Radiations including electron beams are pre-ferably applied at doses o-f at least 30 KGy, more pre-ferably a-~ least 50 KGy.
Radiations are applied to at least one side o-f a elLm, a sheet, a container or a bottle i-f they are made o-f a single polyolefin layer containing an oxidation catalyst.
Exposure to radiations is also e-ffective even i~ one or both sides o-f the oxidation catalyst containing polyolefin layer is laminated with another resin layer that does not contain an oxidation catalyst. Radiations may be applied to any side o-f -films, etc. but they are preferably applied to the side having the polyole-fin layer containing an oxidation catalys-t. Exposure to radiations may be per-~ormed by various known methods.
The oxygen barrier quality o-f the laminate based on the oxidation catalyst contain:Lng polyo:Le-fin sheet of the present invention will be suppressed i:~ there is an ad~acent res:Ln layer containing an antioxidant. Rven in this case, the desired oxygen barrier qual:Lty :ls guaranteed by performing exposure to radiations in the manner descr:Lbed above. A probab:Le mechanism -for this phenomenon is that irradiation permits more radicals to be -formed to surpass the inhibition Or their generation by antioxidants or that irradiation promotes the generation o-f radicals in areas where the e-f-fects o-f antioxidants are less intense.

, A corona discharge treatment makes use o-P "corona discharge", a phenomenon in which a conductor placed under high voltage in the air undergoes dielectric breakdown only in the area that is close to its sur-face and which has a large potential gradient, with the resulting discharge being sustained until a plasma called "corona" develops in the discharged area. For the purposes of the present invention, the corona discharge treatment is pre-ferably conducted with power applied at a value o-f at least 50 W/m2 per min, more pre-ferably at least 100 W/m2 per min. Any articles can be subjected to a corona discharge treatment and they include -films, sheets, containers, bottles, etc.
In making laminated sheets, corona discharge can be produced by applying a high voltage between a roller supporting the substrate and an opposing electrode, w:Lth the substrate belng contlnuously passed between the roller and the electrode to perform the intended treatment on the surface o-f the substrate. When performing a corona discharge treatrnent on ho:Llow articles such as contalners and bottles, the two electrodes may be positloned in such a way that one o-f them is inserted into the container while the other is put outside so that the container wall is held between the two electrodes.

~, , For the purposes o-f the present invention, a corona discharge treatment is desirably appl:led to the surface o~' a polyole~in layer eontaining an oxidatlon catalyst. lt is generally di-f-ficult to insure that the corona discharge treatment works e-~fectively aeross the thlckness Oe a resln layer. If the artiele to be treated is composed o-~ a single polyolefin layer containing an oxidation eatalyst, either side of the layer can be e-e~ectively treated by corona diseharge. However, when an oxidatlon catalyst free resln layer is laminated on one side o-~ the polyole-fin layer containing an oxidation catalyst, the other side o-f the polyole-~in layer must be sub~eeted to a corona discharge treatment. In other words, the corona discharge treatment will prove little e-f-fective if an oxidation eatalyst free resin layer is provided on both s:ides o-f the polyole-fin layer eontaining an oxidation catalyst.
Polyolefins will readily -Porm radica:Ls :L~ they are subJeeted to the action of l:Lght or heat during therma]
shaping or storage in the presence Oe oxidat:Lon catalysts, and the formed radicals will react with aerial oxygen to become peroxy radieals, whieh in turn reaet with the polyolefin to generate hydroperoxides and radicals. The generated hydroperoxides are believed to deeompose -to an alkoxy radical and a hydroxy radical, which in turn react with the polyolefin to produce radicals.

-- 1 ar --2 ~ 3 By employing the speclfied -~eatures o-~ ~he present invention, particularly by incorpora-ting an oxidation catalyst in a polyolefin resin, more radicals would be generated in the manner described above, whereby the reaction for the polyolefin to absorb oxygen through radical reaction is enhanced and the resulting consumption o-f aerial oxygen contributes to an improvement in the oxygen barrier quality of the polyolefinic resin layer.
Both exposure to radiations and corona discharge treatment would be effective in enhancing the generation of radicals to achieve a further improvement in the oxygen barrier quality of the polyole~inic resin layer by virture o-f the applied energy of radiations or corona discharge.
The following examples are provided for the purpose of further illustrating the present invent:Lon but are in no way to be taken as limiting.
Example 1 Polypropylene having a me:Lt index (M.:[.) of 0.5 that con-tained 10 ppm o-f' cobalt stearate in terms of' the concentration of' cobalt atoms but whlch dld not conta:Ln a radical inhib.Ltor was extrusion molded at 260C to -Porm a sigle-layered sheet of polypropylene 800 ~Im thLck, which was desginated sample 1.
AdditLonal samples 2 - 6 and comparative sample 1 were prepared by repeating the same procedure except that the concentratlon of cobalt atoms in cobalt stearate was changed to the values shown in Table 1.
Immediately after their preparation by extrusion molding, the individual samples were left to stand at 25C
for measuring the time-dependent pro~ile of their oxygen permeability with MOCON Ox-TRAN 100 ~Modern Controls, Inc.) The results are also shown ~n Table 1.
- Table 1.
_ Sample Concentratlon Oxygen permeability, ml/m ~day/atom No. of cobalt stearate, ppm O day 7 days 14 days 28 days 5B days 1 10126.8 124.3 122.2112.7 81.6 2 25145.3 142.5 137.2114.3 82.9 __ __ . _ 3 50137.1 136.4 124.798.0 ~2.7 4 100137.2 125.9 105.271.0 22.0 _ _ _ _ ~
5200 105.4 82.~ 50.6 11.4 0 1 61000 6.6 0.1 0.1 0.1 0.1 . ____ . _ _ _ Compa-risonl O 151.3 151.2151.2 151.1 151.0 As Table 1 shows, the addition o~ cobalt stearate as an oxidation catalyst was effective in causing a substantlal drop in the oxygen per~eabllit~ of polyolefin.

* Trade-mark Example 2 Additional sheet samples~7 - 12 were prepared by repeating -the procedure o-f Example 1 -for the preparat:lon o-f sample 1, except that cobalt stearate was replaced by aluminum stearate or aluminum acetylacetonate -that were used in the amounts indicated in Table 2, and that the temperature -~or extruion modllng was set at 220~C. These samples were subjected to the same evaluation as in Example 1 and the results are also~shown in Table 2.
Table 2 Sample Type and concent- Oxygen permeab11ity,ml/m2~day/atm No. ration of oxida-tion catalyst*
~ (PP _ _ Oday 7days 14days 28days 58days 7 lOO 145.7 146.3 134.6 143.4 138.6 _ ., ,,_ . . . ,, ~ __ __ . _,,.,_ . .. _,__ _. _ _ ~
8 A 153.2 140.3 123.2 119.3 110.2 ~ . ~ ., _ . , , . _ _ _ . __ .. _ ; ~ 9 500 150.2 149.8 145.9 106.5 107.B
_._ ., ... _, __. ____ ~ _____ _._ _.. , .............. ._ 1L) _ 100 132.2 125.3 l11.9 119.3 :Ll7.3 11 200 140.4 136.8 131.0 125.4 123.7 . .. ~ _ ... ., __ . .~__ . .. _~.~ ,_ ~,~ .. ,.,, .. _ ................ __ . 12 B 138.6 137.5 133.8 128.4 123.l A: aluminum stearate; B: aluminum acetylacetonate 2 ~

The concentration o-f each oxidation catalyst :Ls expressed in terms o-f aluminum atoms.
As is clear -~rom Table 2, oxygen barrier quality could also be achieved by using aluminum containing oxidation catalysts.
Example 3 Additional sheet samples 13 - 36 and comparative samples 2 - 7 were prepared by repeating the procedure o-f Example 1 -for the preparation o-f sample 5, except that in addition to the oxidation catalyst, the radical inhibltors shown in Table 3 were incorporated in polyole-fin, which was extrusion molded at 220C to make sheets having a thickness o-f 1,000 IJm. Each Oe these samples was subjected to the same evaluation as in Example 1 and the results are shown in Tables 3, 4 and 5.
(The remaining space is leet b:lank.) 2 ~

Table 3 . _ __ Sample Type and concent- Oxygen permeability,ml/m ~day/atm No. ration of radical inhibitor _ _ (ppm) Oday 7days 14days 28days 58days . .... ~ ~ _ _ _ 13 a 97.9 67.9 33.2 0.2 O
_ ~_ _~.
14 a 99.1 _ 43.0 5.0 _ 50 __ a 102.8 96.3 96.3 88.2 68.5 .. __ Compa- a 104.4 96.7 98.2 96.7 95.8 rison 2 1000 --~ _ ___ ~ ~, _. .
16 b 35.0 _ 0.6 O
._A _ . . ~...... _ ___ ____ _ 17 blO 77.7 13.2 0.3 0.1 _ _ .. _ .. _ .__ _ 18 b 77.6 _ 6.0 0.3 ._. ... ... ,_ _ .. _ ____ 19 b 84.3 59.7 32.8 0.1 0.1 . __ . _ _ ~_ . .
b 88.2 _ 52.1 20.0 _ A __ ~ . _.. . __ _ . ~ _ . ._ _ 21 b 95.1 _ 78.3 50.1 . . . __, , ~ . . I--~ - - ~ 1----------- - - - - I
Compa- b 95.8 92.5 88.7 83.1 62.2 rLson 3 1000 ~ _ ,.. _. . .
~The remaining space is left blank.) Table 4 _ , Sample Type and concent- Oxygen permeability,ml/m2~day/atm No. ration o-f radical inhibitor ~ -- -~
(ppm) Oday7days 14days 28days 58days . . .__ _. .__ 7 . . . _ . . . __ 22 c 25.2 _ 0.7 .1 . . . ,,.~. . . _ -- - -----~
23 c 65.95.7 0.1 0.1 0.1 __ .. ... . .... _ ... _ 24 c 75.2 _ 9.0 0.3 .__ ...._ .._ .
25 . c 97.778.2~3.5 0.~ 0.1 .. .... _ ~ _ ..
26 c 97.8 _ 48.7 24.

. . ... _ .. . . ~
27 c 100.1 _ 81.2 71.0 .. _ . _ .... ...... __ _._ Compa- c 104.995.491.3 82.4 15.0 rison 41000 .. _ ._ .__ __ ~ . ____ 28 d 89.347.0 16.2 0.1 ... _ __ ........ .~, 29 d 92.3 . 23.0 0.1 _ .. __ ~ ___. .... ._ _ ___ d 96.3 65.5 3~.6 0.1 __ . ._.__ ... ~. ... ___ - ....... ..
Compa- d 95.8 85.8 92.1 91.7 rison 51000 ~ . . . ..

(The remaining space is left blank.) Table 5 ~ __ .~ ..................... ~
Sample Type and concent- Oxygen permeability,ml/mZ day/atm No. ration of radical inhlbitor _ _ (ppm) Oday 7days 14days 28days 58days _ . _ .. __ . _ 31 10 96.2 58.6 4.4 0.2 ~ - - . __ .
. 32 5eO 99.2 _ 29.1 4.0 _ I_~ ~ _ ------ ---- --'-I
33 100 100.8 88.5 90.2 87.6 ~ ...
Compa- e 97.7 91.4 101.4 105.4 rison 6 1000 .. ~ ____. ._ ._ 34 lfO 100.5 56.3 13.6 0.1 . _ ._._ ... ~
-5fo 97.3 _ 37.8 3,0 . . _ ... _ . ._ __ . ,,._.
36 l-OfO 102.1 89.3 78.2 66.3 . _ . . _ ., _ _ . . . _ Compa- .f 99.9 90.7 101.0 97.0 rison 7 1000 _ _ __ , __ ._ Radical :Lnhibltors a: IRGANOX1010 b: IRGAFOS168 c: TINUVIN622L,D
d: TINUVIN326 e: IRGAFOS168/IRGANOX1010=2/1 -f: IRGAFOS168/IRGANOX1010=1/1 :

As is clear -from Tables 3, 4 and 5, the smaller the content o-~ radical inhibitor, the lower the oxygen permeability and hence the bet-ter oxygen barrier qual:Lty.
In contrast, the drop in oxygen permeability was negligible in comparative samples 2 - 7 which conta:ined more than 1,O00 ppm o-~ radical inhlbitors.
Example 4 Additional sheet samples 37 - 39 were prepared by repeating the procedure of Example 1 -~or the preparation o-~sample 5 except that the sheet thickness was adjusted as shown in Table 5. These samples were subJected to the same evaluation as in Example 1 and the results are shown :Ln Table 6 toge-ther with the data -for sample 5.

Table 6 ,, ..,.__ No. Sheet sample Oxygen permeability, ml/m2~day/a-tm Thickness, _ _ __ _ ---llm Oday 7days 14days 28days 58days ,,_ .~ ~ ~ ~ ~ .,_ 37 200 520.6466.2 417.4 263.4 2~8.4 38 400 266.0213.0 135.0 32.1 15.3 39 1200 78.462.9 0.1 0.1 0.1--5 800 _10~.4_ 82.7 50.611.4 0.1 (The remaining space is le~t blank.) 3 ~ ~ s~

Example 5 Polypropylene (M.I. 0.5) that contained cobalt stearate at predetermined concentrations o-f cobalt atoms (see Table 7) but which did not contain a radical inhibitor was extrusion molded at 260~C to -form single-layered sheets of polypropylene 800 1Im thick. A biaxially oriented polyester -film having a thickness o-~ 5.4 1Im, 12 um or 25 um was laminated on both sides o-~ each polypropylene sheet using a urethane resin adhesive, whereby laminated sheet samples 40 - 44 were prepared. These samples were subjected to the same evaluation as in Example l and the results are shown in Table 7.
Comparative samples 8 - lO were prepared by repea~ting the procedures -for preparing samples 41 - 43, respectively, except that no cobalt stearate was con-tained. These comparative samples were subJected to the same evaluation as above and the results are also shown in Ta~le 7.
(The remaining space is le-~t blank.) ~ ~3 ~ c~

Table 7 . . _ . ~
Sample Co con- Thickness Oxygen permeabil:ity,ml/rn2~day/atm No. centra- o-f OPET
tion, on one _ _ .
ppm ~m 1 day 14 days30 days 60 days _ . _ _ ,......... . . __ 200 25 0.2 0.1 0.1 0.1 _ _ .. _ . ~ _ ___ 41 200 12 0.2 0.1 0.1 0.1 .. ,._ _ ~ __ .
Inven- 42 200 5.4 4.0 0.1 0.1 0.1 tion _ 43 500 12 0.2 0.1 0.1 0.1 _ .. _ __ ~ ____ ~ .~
44 500 5.4 0.1 0.1 0.~ 0.1 .. _ _ .. __ . ___ ... .
8 O 25 ~17.6 17.4 17.5 17.2 _ . . _ .. . _ .__ Compa- 9 O 12 34.1 33.9 34.4 34.3 rison _ . . .
O 5.4 54.2 54.5 54.1 53.9 Example 6 An addi-tional sample 45 was prepared by repeating the procedure o~ Example 1 -~or the prepara-tion O-e sample 5, except that the extrusion tempera-ture was adJusted -to 250C, that the sheet thickness was changed to 400 ~m, and -that aeter extrusion mold:Ln~, one sur-eace o-~ the sheet was exposed to electron beams at an acce:Leration voltage Oe 200 kV ~or a total dose O-e 5 Mrad. Another sample 46 was prepared by repeating this procedure except that the total exposure dose o-~ electron beams was increased to 10 Mrad.

S-till another sample 47 was prepared by repeat:Lng the same procedure except that exposure to electron beams was no-t - 2~ -2 13 ~

per:~ormed. The three samples thus prepared were sub~ected to the same evaluation as in Example 1 and the results are shown in Table 8 below.
Table 8 She .t sample ~ Oxygen permeabllity, ml/m2-day/atm¦
No. Exposure _ _ , _ dose, Mrad O day 7 days 1~ days 30 days . ~ . ._ . . .
~5 5 120.0 65.0 38.0 12.0 ._~ . . . - . . .__ 46 10 53.0 32.0 18.0 6.0 .. ... _. . . .
47 none 266.0 213.0 135.0 20.0 _ ... . .. __ . ... _ __ __ . ._ As is clear from Table 8, exposure -to electron beams was ef-fective in enhancing the oxygen barrier quality o-f polypropylene.
_ample 7 Polypropylene A tM.I. 0.5j that contained 200 ppm of cobalt stearate in terms of the concentration of cobalt atoms but which did not contain a radical inhlb:l-tor, and polypropylene B that contained neither oxidatio:n ca-talys-t nor radical inhibitor were co-extrusion Molded at 250~C -to -fornl a two-ply lam:lnated sheet that consisted o-f polypropylene layers A and B in respective thicknesses o-f 500 IJm and 250 llm. The side o-f the laminated sheet that had the layer o-f polypropylene A containing the oxidation catalyst was exposed to electron beams under the same ~ 3 conditions as in Examp]e 6 -~or the preparation o-f sampLe 46, whereby sheet sample 48 was obtained. An additional sample 49 was prepared by repeatin~ the same procedure except that exposure to electron beams was not per-formed.
Each sample was subjected to the same evaluation as in Example 6 and the results are shown in Table 9.
Example 8 Polypropylene A (M.I. O.S) that contained 200 ppm o-~cobalt stearate in terms o-~ the concentration of cobalt atoms but which did not contain a radical inhibitor and polypropylene B that contained neither ox:idation ca-talyst nor radical inhibitor were co-extrusion molded at 250C to -~orm a three-ply laminated sheet that consisted o-~ three propylene ].ayers B, A and B in respective th:Lcknesses of 250 llm, 500 IJm and 250 l~m. One side o-f the lamlnated sheet was exposed to electron beams under the same conditions as in Example 6 ~or the preparation o~ sample 46, whereby sheet sample 50 was obtained. An addltional samp:Le 5.l was prepared by repeatin~ the same procedure except that exposure -to electron beams was not per-~ormed. Each sample was subJected to the same evalua-tion as in Example 6 and the resul-ts are shown in Table 9.

Table 9 . ... _ , _ _ . _ . _._ ....................... .... _ __ She et sample Oxygen permeabLlity, ml/m ~day/atm No. Exposure ~ ---------I
dose, Mrad Oday 7days 14days 30days 180days ._ _ ~.__ 48 1010.0 4.0 2.0 1.5 1.5 . __ ~ _ . ._ _ 49 none117.0 70.0 15.0 10.0 4.0 _ _ _ _ Oday 7days 14days 32days _ _ ._ . _ , . _ 11.0 10.0 8.0 5.0 _ _ ~ . ... -----I
51 none 117.0 70.0 15.0 8.0 _ . .__ -- . ._ __ _ ~ s is clear -from Table 9, propylene sheets o-f good oxygen barrier quality could be produced by performing exposure to electron beams whether they were two- or three-ply laminates.
Example 9 An additlonal sample 52 was prepared by repeating the procedure o-f Example ~ -for the preparation o-f samp:Le 5, except that the ex-trus:Lon terl~perature was adJusted -to 250C, that the sheet -thickness was changed to ~00 llm, and that a-fter extrus:Lon moldLng, one sur-face o-f the sheet was subJected to a corona d:Lscharge treatment with a power of 667 W/m2 per min for a width o-f 0.6 m at a line speed of 10 m/min. Another sample 53 was prepared by repeating this procedure except that no corona discharge treatment was performed. Each o-f these samples was subJected to the same 4,~

evaluation as in Example l and the results are shown in Table 10.
Example 10 Polypropylene A (M.I. 0.5) that contained 200 ppm of' cobalt stearate in terms o-~` the concentration of cobalt atoms but which did not contain a radical inhibitor, and polypropylene B that contained neither oxidatlon catalyst nor radical inhibitor were co-extrusion molded at 250C to form a two-ply laminated sheet that consisted Or polypropyléne layers A and B in respective thicknesses o~
500 um and 250 um. The side of the laminated sheet that had the layer o-f poLypropylene A containing the oxidation catalyst was sub~ected to a corona discharge treatment under the same conditions as in Example 9 ~or the preparation of sample 52 except that the applied power was changed to the values shown in Table L0, whereby sheet samples 5~ and 55 were obta:Lned. ~n add:Ltional sample 56 was prepared by repeating the same procedure excep-t tha-t no corona discharge treatMent was conducted. Each o-f the three samples was sub~ected to the same evaluation as in Examp:Le 9 and the results are shown in Tahle 10.

3 ~

Table 10 _ _ Sheet sample Oxygen permeability, rnl/rn2-say/atrn No. Corona -~is-charge power, _ _ _ _ W/m omin 0 day 7 days 14 days 30 days _. ..... ._._ ._ 52 667 204.082.0 65.0 13.0 53none 266.02l3.~135 0 1 20.0 54 _667 101.033.0 32.0 1 19.0 55 100 101.062.0 43.0 28.0 .. ~ ._ . . _ 56none 134.0 98.0 70.0 38.0 . . .. _ .__ __ _~

As is clear -from l'able 109 the oxygen barrier quality o-f propylene sheets could be enhanced by corona discharge treatment.
Example 11 Polypropylene (M.I. 0.5) that contained 200 ppm o~
cobalt stearate in terms o-f the concentrat:Lon o-f cobal-t atoms and which did no-t con-tain a rad:Lca:L :Lnhlbitor was extrusion molded at 260C to -form a s:lng:Le-:Layered sheet of polypropylene, which was subsequently stored :Lndoors -for 4 rnonths (shee-t O!) .
Sheet ~ was ground into particles and added in an amount o-f 0.2 part by weight to one part by weight of polypropylene containing no radical inhibitor. To the mixture, cobalt stearate was added in such an amount that the total concentration o-f cobalt atoms would be 200 ppm, 2 ~

and the resulting blend was extrusion molded at 220~C to -~orm a single-layered sheet o-f polypropylene in a thlckness of 800 llm, which was designated sample 57. This sheet was subJected to the same evaluation as in Example 1 and the results are shown in Table 11.
Example 12 The ground particles of sheet ~ prepared in Example 11 were added in an amount of 0.25 part by weight to one part by weight of poIypropylene containing no radical inhibitor.
The resulting blend and polypropylene B containing neither oxidation catalyst nor radical inhibitor were co-extrusion molded at 220C to -form a three-ply laminated sheet having a total thickness o-f 1 mm that consisted of the intermediate blend layer (400 ~Im) sandwiched between polypropylene B layers each having a thickness o-~ 300 um, whereby sample 58 was obtained. This sample was subJected to the same evaluation as in Examp].e 1 and the resul-ts are shown in Table 11.
Table 11 . . . _ . ._ . _ .. . _ . _ _ _ ~. .
Sample Oxygen permeability, m]/m2-day/atom ~ _ ,~,~
No. O day14 days 28 days .... __ .. ~
57 121.2 0.4 0.1 .
58 11~.2 _ 17.2 ' _ . .__ .. ~

~ s is clear -f'rom Table 11, the oxygen barrier qual:i.ty o-f a polypropylene shee~ could be improved by blending with a polypropylene composition that had been oxidized upon standing.
Example 13 Polypropylene (~ .5) that eontained 200 ppm o-f cobalt stearate (oxidation catalyst~ in terms of the concentration of eobalt atoms but which did not eon-tain a radical initiator was extrusion blow-molded to fabricate a bottle having a capacity of 900 ml, a sur-faee area o-f 2.4 x 10 2 m2 and an average wall thickness o-f 900 ~Im in the body. This bottle was designated sample 101. Additional samples 102 - 10~ and compara-tive sample 101 were -fabricated by repeating the same procedure exeept that eobalt stearate was replaeed by the oxidation cata].ysts shown in Table 12. More additional samples 105 and 106 and comparative sample 102 were fabrieated by repeat:Lng -the proeedure of the -fabr:Lcation o-f sample 101 except that the eoneentrat:Lon of cobalt atoms in eobalt stearate was ehanged as shown in Table 12 and that the average wall thiekness o-f the body was redueed to 500 um. Immediately after their fabrieation by extrusion blow molding, samples 101 - 106 and eomparative samples 101 and 102 were left to stand at 25C for measuring the time-dependent profile o-f 2 ~

oxygen permeability with MOCON Ox-TRAN 100 tModern Controls, Inc). For samples 105 and 106 and comparative sample 102, the oxygen permeabil:Lty measurement was conducted only on the 30th day. The results are shown .in Table 12.
Table 12 ._ ___ . ..................................... _ . _ .
Bottle sample ¦Oxygen permeability, ml/m2~day/atm : No. Oxidation cata- _ _ _ _ I
lyst and its 10 days 30 days 60 days 90 days concentration, . ~ ._ _ _ _ _ 101 ~ 13.5 0.3 0.0 0.0 102 C 107.2 ___ _ _ 74.5 103 D 120.6 _ _ 97 7 __ 104 E 54.5 3.1 0.6 0.4 _____ ____._, ___ _. _._ .. . ....... ~~
risonnone 116.3 116.3 116.3116.3 --- - - ------1 ~ ------- ~--- ---- -105 A _ 2.6 _ . . -- - ---I --- - --- - ----106 A _ 4.7 _ Compa- _ ~ ~ __ _ _ rison none _ _._ 165.0 _ __ ***C: aluminum acetylacetonate D: titanium oxyacetylacetonate E: manganese acetylacetonate As described in detail on the forego:Lng pa~es, the present invent:Lon provides a polyolefinic resin compos:Lt:ion that exhibits an effective oxygen barrier property on :L-ts own without using expensive other reslns that have oxygen barrier quallty. The present invention also provides a sheet and a container that have oxygen barrier quality using such an improved polyole-finic resin composition.
Further, the present invention provides processes -for producing such a sheet and container.
~The remaining space is le-ft blank)

Claims (16)

1. A polyolefinic resin composition that comprises a polyolefin, an oxidation catalyst and 0 - 500 ppm of a radical inhibitor.

2. A polyolefinic resin composition according to claim 1 wherein said polyolefin is a homo - or copolymer of a propylene monomer.

3. A polyolefinic resin composition according to claim 1 or 2 wherein said oxidation catalyst is a compound of a transition metal.

4. A polyolefinic resin composition according to claim 1 or 2 wherein said oxidation catalyst is an aluminum compound.

5. A polyolefinic resin composition according to claim 1 or 2 wherein said oxidation catalyst is contained in an amount of at least 100 ppm in terms of the weight of metal atoms.

6. A polyolefinic resin composition according to claim 1 or 2 wherein said radical inhibitor is contained in an amount of 0 - 100 ppm.

7. A sheet having an oxygen barrier property that is made from the resin composition recited in claim 1 or 2.

8. A packaging material having an oxygen barrier property that is made from the resin composition recited in claim 1 or 2.

9. A packaging material having an oxygen barrier property that is comprised of a laminate of a layer made from the resin composition recited in claim 1 or 2 shape-retaining resin layer.

10. A container having an oxygen barrier property that is made from the resin composition recited in claim 1 or 2.

11. A hollow container having an oxygen barrier property that is made from the resin composition recited in claim 1 or 2.

12. A process for producing a sheet having an oxygen barrier property by melt extrusion molding the resin composition recited in claim 1 or 2.

13. A process for producing a sheet having an oxygen barrier property, which comprises mixing a polyolefin with a metal catalyst, leaving the mixture to stand for oxidation, blending the oxidized mixture with another polyolefin, and extrusion molding the resulting blend.

14. A process for producing a sheet having an oxygen barrier property, which comprises shaping the resin composition recited in claim 1 or 2 and subsequently exposing the shaped composition to radiations.

15. A process for producing a sheet having an oxygen barrier property, which comprises shaping the resin composition recited in claim 1 or 2 and subsequently performing a corona discharge treatment on the surface of said shaped composition.

16. A process for producing a hollow container having a barrier property, which comprises making a parison or preform from the composition recited in claim 1 or 2 and subsequently blow molding said parison or preform.