CA1280850C

CA1280850C - Copolymers

Info

Publication number: CA1280850C
Application number: CA000538964A
Authority: CA
Inventors: John Hobes; Wolfgang Payer; Ludger Bexten
Original assignee: Ruhrchemie AG
Current assignee: Hoechst AG
Priority date: 1986-06-26
Filing date: 1987-06-05
Publication date: 1991-02-26
Anticipated expiration: 2008-02-26
Also published as: EP0254022A3; EP0254022A2; DE3621394A1; US4883853A

Abstract

ABSTRACT OF THE DISCLOSURE

Novel copolymers of ethylene containing per 100 parts by weightof ethylene 0.2 to 5.0 parts by weight of 2,4,4-trimethyl-pentene-(l) and optionally 2.0 to 20 parts by weight of vinyl ester or vinyl ether or ester of acrylic acid or methacrylic acid with alcohols of 1 to 8 carbon atoms having a melt index MFI (190/2.16) of 0.4 to 20 g/10 min. a density of 0.915 to 0.960 g/ml and an impact tensile strength of 850 to 2,600 mJ/mm2 and a process for their preparation useful for making transparent films.

Description

~2aoaso DE-AS 2,018,718 describes a process for the preparation of modified high pressure polyethylene polymers where the poly-merization of ethylene and optionally other compounds which can be copolymerized with ethylene takes place in the presence of oligomers of isobutylene which consist of 4 to 100 isobutylene units. The said polymers are suitable for the manufacture of films and the addi~ion of oligomers of isobutylene prevents surface stickiness of the films, known~as blocking.
If, on the other hnd, disobutylene is used~ n`on-homo-geneous polymers are obtained and the films made from suchmaterials are cloudy and exhibit specks (cg. DE-AS 2,01~,718, col.

2, lines 32 to 38 and column 6, comparative Example 21). Therefore, they are unsuitable for pac~ing purposes. Certain demands are placed on films which are used as packing material especially for goods to be stored at low tèmperature. They have to have high , transparency, stiffness, Luster and good impact tensile strength and these properties must~also be retained at low temperatures~

It is an object of the invention to provide novel ethylene copol~mers useful for films having excellent properties, even at low temperatures and their preparation.
It is another object of the invention to provide novel films of excellent properties.
~ These and other ob;ects and advantages of the invention : will become obvious from the ollowing detailed description.
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'. The novel copolymers of the invention are comprised of a copolymeri of ethylene containing per lOO parts by weight of ~ 0 8~0 ethylene 0.2 to 5.0 parts by weight of 2,4,4-trimethylpentene-(1) and optionally 2.0 to 20 parts by weight of vinyl ester or vinyl ether or ester of acrylic acid or methacrylic acid with alcohols of 1 to 8 carbon atoms having a melt index MFI (190/2.16) of 0.4 to 20 g/10 min. a density of 0.915 to 0.960 g/ml and an impact tensile strength of 850 to 2,600 mJ/mm2.
The binary copolymers contain per 100 parts by weight of ethylene 0.2 to 5.0, preferably 0.3 to 4.0, in particular 0.35 to 3.5 par~s by weight of 2J4,4-trimethylpentene-(1). The ternary copolymers consist of ethylene, 2,4,4-trimethylpentene-(1) and a further monomer selected from the group consisting of vinyl ester, vinyl ether, acrylic acid ester or methacrylic acid ester! vinyl ester and the ester of acrylic acid or methacrylic acid are particu-larly suitable as monomers. Acrylic acid ester and in particular vinyl ester are preferred.
Among the preferred vinyl esters are those whose car-boxylic acid groups contain 2 to 4 carbon atoms, preferably vinyl acetate and the preferred vinyl ethers contain 4 to 8 carbon atoms.
An example o~ these compounds is vinyl ethyl ether. The acrylic - acid ester and methacrylic acid ester are derived from aliphatLc alcohols of 1 to 8 carbon atoms in the molecule. The alcohols can :
be straight-chained or branched and carry the OH group on a primary, secondary or tertiary carbon atom. Methyl, ethyl and tertiary - bNtyl.acrylate as well as methacrylate have prov~d to be partlcularly suitable.
~;r The ternary polymers contain per 100 parts by weightof ethylene 0.2 to 5.0, preferably 0.3 to 4.0 and in paxticular 0.35 , ,~ to 3.5 parts by weight of 2,4,4-trimethylpentene-~) and 2.0 to 20 r preferably 2.2 to 15 and in particular 2.5 to l0 parts by weight 30 J of the afore-mentioned monomers .

1'~ 80 8 50 The copolymers o~ the invention are characterized by a melt index MFI (19Q/2.16) of 0.4 to 20.0, preferably O.5 to 10.0 and particularly 0.6 to 4.0 g/10 min. The said melt indices are determined according to German standard DIN S3735. Empirically, an average mol mass de~ermined by the process of gel permeation chromatography can be assigned to every melt index measured and the corresponding values can be taken from the following table.
MFI 190/2.16 Average mo~ mass tg/10 min.) (g x mol~ ) 16.0-20.0 20,000 3.0 70,000 2.0 100.~00 .
0.8 120,000 0.4 140,000 The density of the copolymers is 0.915 to 0.960, preferably 0.920 to O.945 and in particular 0.925 to 0.940 g/cm3. The polymers are - also defined by their impact tensile strength which ranges from 850 to 2,600, preferably 870 to 2,500 and in particular 900 to 2,200 mJ/mm2. The impact tensile strength is determined according 2~ to German standard DIN 53448.
The novel binary and ternary ethylene copolymers can be prepared by copolymerization of the monomers at 50 to 350 mPa and 100 to 350~C in the presence of oxygen or radical-forming compounds.
Mixtures are polymerized from 100 parts by weight of ethylene, 0.4 , ` to 10.0 parts by weight o~ 2,4,4-trimethylpeptene-~1~ and optionally ;. 1.5 to 25.0 parts by weight of vinyl e~ter or vinyl ether or ester , ~ . .
: of acrylic acid or methacrylic acid and an aliphatic alcohol of 1 to 8 carbon atoms. As the polymerization rate of the monomers is . . ~ .
generally different, the composition of the polymer often derivates from the composition of the monomer mixture.

~'~ 80 ~50 Polymerization takes place at a pressure of 50 to 350, preferably 100 to 300, and in partic~lar 125 to 275 mPa and the po].ymerization temperature is 100 to 300, preferably 120 to 325 and in particular 130 to 300C.
Oxygen or radical-forming compounds are employed as polymerization initiators and the radical forming -compounds include organic peroxides, hydroperoxides or aæo compounds. Of the organic peroxides, tertiary butylperbenzoate, tertiary butylperoxypivalate and dilaurylperoxide have proved useful. Azo-bis(isobutylronitrile) - has been successfully used as an azo compound. Tertiary butylperoxy-pivalate has proved to be particularly suitable. The compounds can all be used alone or as a mixture. The polymeriæation initiators are used in a concentration of 3 to 50, preferably 5 to 40, in particular 10 to 25 weight ppm based on the ethylene. They are added to the polymerization dlrectly or as a solution in an organic solvent.
Hydrocarbons such as isooctanej benzene, toluene or gasoline frac-tions serve as solvents.
An essential feature of the process for the new polymers -~ of the invention is the absence of separate molecular mass regulators 20 ~~ (moderators) during polymerization. Molecular mass regulators are compounds which are added to the monomers in various concentrations :
to influence the growth of the polymer molecule and thus the mol mass of the polymer. The mol mass regulat~rs include members of a wide variety of substance classes. Examples are: hydrogen, alkanes, unbranched alpha olefins, alcohols, aldehydes and ketones (~
; Fortschr. Hochpolym.-Forschg. 7~3), 386-448).
. , - In this connection~it must be pointed out that diiso-butylene, i.e. a mixture mainly consisting of 2,4,4-trimethylpentene-, (1) and -~2), itself ac~s as a mol mass regulator (cf. Fortschr.
Hochpolym.-Forschung ?(3) 417). Thus,- mono~er mi~tures with a . .

~'~ 8~ 8S0 higher content of 2,4,4-trimethylpentene-(1) produce polymers with a lower mol mass than monomer mixtures in which the 2,4,4-trimethyl-pentene-(l) concentration is lower.
If polymerization takes place not Gnly in the presence of 2,4,4-trimethylpentene-(1) but also in the presence of other mol mass regulators, polymers are obtained which are not suitable for the manufacture of films. The draw-down i~ particularly unsatisfactory.
Moreover, the films exhibit specks and are useless as packing material owing to their lack of transparency. It was not to be foreseen that if the separate addition of a re ~ ator apart from the comonomer 2,4,4-trimethylpentene-(l) acting simultaneously as a mol mass regulator was dispensed with, polymers would be ~ormed which can excellently be processed to films with outstanding properties.
The monomer mixture reacted according to the invention process always contains 2j4,4-trime~thylpentene-(1) with its content being 0.4 to 10.0, preferably 0.6 to 8.0, particularly 0.7 ~o 7.0 parts by weight per 100 parts of ethylene. 2,4~4-trimethylpentene-(1) can also be added to the polymerization reaction in the form of -a mixture with other C8 olefins. Diisobutylene is particularly suit-~able as a mixture containing 2,4,4-trimethylpentene-~1) mainly con-sisting of 2,4,4-trimethylpentene-(1) and 2,4,4-trimethylpentene-(2) whLch is formed during dimerization of 2-methyl-propene-~i-butylene) ~ with acidic catalysts (e.g. ion exchangers). Depending on the manu-;~,facture, it contains 50 to 90, preferably 55 to 80 and in particular i~60 to 75 parts by weight of 2,4,4-trimethylpentene-~1), in each case based on 100 parts by weight o diisobutylene.
~;Apart from ethylene and 2,4,4-trimethylpentene-~1), the ;monomer mixture polymerizèd by the process of the invention can con-tain other monomers including vinyl este~s, vinyl ethers, acrylic acid es~ers and methacrylic acid esters. Their con~ent in the -5,-,' ,; ' ' ,, ~ X 8~ ~O
monomer mixture is 1.5 to 25.0, preerably 2.0 to 20.0 and in par~icular 3.0 ~o 15.0 parts by weight, based on 100 parts by weight of ethylene. The residence period o the monomer mixture in the polymerization stage is 30 to 180, preferably 50 to 160 and in particular 60 to 140 seconds.
The process of the inven~ion can be performed in high pressure reactors known for the polymerization of ethylene and ethylene-containing monomer mixtures. These include etirred auto-claves and tubular reactors (cf. Ullmann Enyclopadie der Technischen 10 ~ Chemie, 4. Auflage, Verlag Chemie Weinheim-Basel 1980, volume 19 page L69, 172-175). When a tubular reactor is used~ the entire monomer mixture already containing initiators can be added in a stream to the reactor. However, it is particularly advantageous to use a tubular reactor with subsequent dosing of cold gas and initiator and to divide the monomer mixture into at least two partial streams. One partial stream is fed in at the reactor entrance and - other partial streams are introduced into the reaction zone along the . ~ , .
reactor mostly in the region of a peak temperature.
Films manufactured Xrom the new copolymers have high~
strength (measured as impact tensile strength~ and remarkable trans-~
; parency which properties are retained even at low temperatures, such ~ ,: . .
a~s those occuring when deep-freeze goods are stored. Moreover, the material is characterized by high draw-down tmeasured as the lowast film thickness which can be manufactured by drawing without the film tearing or holes appearing~. It is 5 to 30, preferably 8 to 25 and ,. ,," ~ ., ; in particular 10 to 20 ~m.
In the following examples A to F the, new polymers and ' the process for their manu~acturearc explained in more de~all.
Examples 1 to 14 relate to compara~ive tests which ~how that obser-vance o the claimed features tmaterial propexties and process para-~ 80 850 meters) are necessary to solve the task on which the invention is based. In the examples~2,4,4-tri~ethylpentene-(1) is always used in the ~orm of the mixture of various C8 hydrocarbons which is designated diisobutylene and has the following composition:
Weight~%
2,4,4-trimethylpentene-(1) 71.3 2,4,4-trimethylpentene-(2) 22.0 other isomers of trimethylpentene 3.3 2,4,4-trimethylpentene 10 - trans-2,2-dimethylhexene-(3) 1.8 It boils at 101C and its density d20 is 0.711 g/cm3.
The following processes were employed to detenmine the properties of the polymers.
Melt Lndex MFI (190/2.16) g/10 min: measured by ~IN
53735; impact tensile strength measured by DIN 53448; draw-down determined by processing of the copolymer on a blown-film machine.
The throughput was 7 kg/h, the noæzle had a diameter of 1 = ~ the blow-up ratio was 2.5:1; transparency; visual assessment of the films.
The 2,4,4-trimethylpentene-(1) share of the polymers was determined from the ~as chromatographically determined~ dif-ference between t~e Z,4,4-trimethylpentene-(1~ content of the monomer mixture at the reactor entrance and the reactor exit. The vinyl ~; acetate share of the polymers was determined by pyrolysis and measure-:- ment of ~he acetic acid liberated by aqueous iodide/iodate solution~
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~ F
; The copoly~ers were manu~actured in a con~inuously : operated high-pressure reac-~or ~irred autoclave) downs~ream of whi~h are a hig~-pressure gas separator and a low-presqure gas separator. The monomer mixture determined for the polymerization _7_ w~ ~ro~lght to the desi~e~ px ~ure and ed in ~o t~he high-pressure reac~or. A~ the ~lne tir~e, ~he ~nlount of polyTneriz~tion initi~tor terti~y but~lperoxypiv~late di~solved in gasoline) required to ~alntai~ the pol~me~ization was added. The re~idetlce pèriod of the reaction Dnix~ure lr~ the high-pre~r~ reac'cor WAB a~out 90 secon~s.
Reaction conditions t lniti~or ~urlcentx~tion (related to the ethylene employed~ and the ~o~lpo~l~ion vf the monome~ mlx~u~e are reported in Table 1 and the properties o~ t~e eopolymers are reported in Ta~le 2.

1~ EXAMPLES 1 t~ S (C.o~pa ~,iv _ e_ Examples ~ t~ S ~ere carried out in the sa~e manner the ~xanlple~ A - F with the only differenee ~ein~ t:h~t ~he rnono~er mlxture contained a ~ep~rate ~ol mas~ regul~tor (tnode~ator). The details o~ the te~ts per~orm~d ax~e in Table 1. Co~p~sition And prop~ties of the cop~lymers obcaine~ a~cording ~o Example~ 1 to 5 ~re lis~ed in 2ahle 2.
CompRred wit~ ~he ~opol~e~ o~ ~xample~ 1 ~ 5, the copol~ers o~ Examples A - F of th~ inventlon e~hibited a conside~ly ine~e~sed impACt ~e~ile s~ength, ~n appreci~bl~r higher draw-d~n 20 as well as significan~ imp~o~emen~ of ~he t:~n~paren~ hey are . t~ere~ore parti~ularly ~ui~a,bl~ ~or the manu~artur~ ~ ;eilms.

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~ 0 ~50 Various modificatio~s of the copolymers and method of the invention may be made without departing from the spirit or scope thereof and it is to be understood that the invention is 4 to be limLted only as defined in the appended claims.

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Claims

1. A copolymer of ethylene containing per 100 parts by weight of ethylene 0.2 to 5.0 parts by weight of 2,4,4-trimethyl-pentene-(1) and optionally 2.0 to 20.0 parts by weight of at least one third member of the group consisting of vinyl ester, vinyl ether or ester of acrylic acid or methacrylic acid with aliphatic alcohols of 1 to 8 carbon atoms, said copolymers having a melt index MFI (190/2.16) of 0.4 to 20 g/10 min., a density of 0.915 to 0.960 g/ml and an impact tensile strength of 850 to 2,600 mJ/mm2.

2. A binary copolymer of ethylene containing 0.2 to 5.0 parts by weight of 2,4,4-trimethylpentene-(1) per 100 parts of ethylene.

3. A binary copolymer of ethylene of claim 2 containing 0.3 to 4.0 parts by weight of 2,4,4-trimethylpentene-(1) per 100 parts of ethylene.

4. A binary copolymer of ethylene of claim 2 containing 0.35 to 3.5 parts by weight of 2,4,4-trimethylpentene-(1) per 100 parts of ethylene.

5. A ternary copolymer of claim 1 containing 0.3 to 4.0 parts of 2,4,4-trimethylepentene-(1) and 2.2 to 15 part of the third member per 100 parts of ethylene.

6. A ternary copolymer of claim 5 containing 0.35 to 3.5 parts of 2,4,4-trimethylpentene-(1) and 2.2 to 15 of the third member per 100 parts of ethylene.

7. A copolymer of claim 1 having a melt index of 0.5 to 10.0 g/min.

8. A copolymer of claim 1 having a melt index of 0.6 to 4.0 g/min.

9. A copolymer of claim 1 having a density of 0.920 to 0.945 g/ml.

10. A copolymer of claim 1 having a density of 0.925 to 0.940 g/ml.

11. A process for the preparation of a copolymer of claim 1 comprising polymerizing at a pressure of 50 and 350 mPa and a temperature of 100 to 350°C in the presence of oxygen or radical-forming compounds as polymerization initiators a mixture of 100 parts by weight of ethylene, 0.4 to 10 parts by weight of 2,4,4-trimethyl-pentene-(l) and optionally 1.5 to 25 parts by weight of vinyl ester or vinyl ether or ester of acrylic acid or methacrylic acid and an aliphatic alcohol of 1 to 8 carbon atoms.

12. A process of claim 11 wherein 2,4,4-trimethyl-pentene-(l) is used in the form of a mixture of 2,4,4-trimethyl-pentene-(l) with other olefins of eight carbon atoms.

13. A process of claim 12 wherein diisobutylene is used as a mixture containing 2,4,4-trimethylpentene-(l).

14. A process of claim 11 wherein the residence period in the polymerization stage is 30 to 180 seconds.

15. A process of claim 11 wherein an organic peroxide or azo compound is used as polymerization initiator.

16. A process of claim 11 wherein tertiary butylper-benzoate, tertiary butylperoxipivalate and/or dilaurylperoxide are used as organic peroxides and azo-bis(isobutylronitrile) as an azo compound.

17. A film made of a copolymer of claim 1.

18. A film made of a copolymer of claim 2.

19. A film made of a copolymer of claim 5.