IE910571A1 - Slippery, antiblocking and optical quality compositions¹based on ethylene copolymers of low crystallinity - Google Patents

Abstract

The sliding, anti-blocking and optical quality compositions are comprised of at least one ethylene copolymer having a cristallinity not exceeding 30 %; they are characterized in that they further include an efficient quantity of ethylene-bis-oleamide. Said compositions may be conveniently used for the fabrication of plates with a thickness comprised between 1 and 10 mm approximately, and particularly for the production of films with a thickness comprised between 10 and 500 mu m approximately.

Description

The present Invention relates to compos it ions fc* based on ethylene copolymers of low crystallinity, .exhibiting good optical, antiblocking and slip I j I properties, and to industrial articles, especially fibred and sheets/ obtained from these compositions.

Zn the industry £or converting plastics into l|j' films the term •blocking* refers to the phenomenon of adhesiveness of a film to itself, which can have many caused, especially an excessively high extrusion temperature, but also the very nature of the plastic to be extruded. To avoid this blocking phenomenon during extrusion and then subsequently on the reels of film, and tp make it easy to open the polymer sleeve obtained it is usual to add to the polymer ’whose function it is to modify the state of the film surface, especially by migration i towards the surface. This is especially the case with ethylene homopolyi ters and copolymers. Conventional additives are inorganic fillers such as silica, or organic ones such-as certain unsaturated fatty acid amides containing^at least 8 carbon atoms, in particular stearic, oleic, palmitic, eruclc, myristic, behenic and lauric amides.

For example, European Patent No. 060,178 1? }by bldw-extrusion^ ‘various additives Ϊ0; IE 91571 1) 2( j describes an antiblocking composition based on ethylene polymer containing from 200 to 2500 ppm of talo.

The abo\ «mentioned conventional additives are completely satisfactory insofar as the antiblocking function is concerned in the case of ethylene polymers and cdpolyraers of intermediate and high crystallinity, that is to say those whose crystallinity, determined by X-ray diffraction/ is at least approximately 30%» this means in particnla|r high density polyethylene (approximately 0.96 to 0.97), radical low density polyethylene (approximately 0.92 to 0.93) and linear low density polyethylene, that is to say copolymers of ethylene and of at least one alpha-olefin containing from 3 to 8 carbon, atoms which have a density l4 f approximately from 0.91 to 0.95. In fact, in the case bf all, these polymers, the addition of approximately up to 2% 'of the above nentloned antiblocking fillers does hot have an unfavourable and appreciable effect on other/ especially optical and mechanical, properties Required in the films.

» The situation ls conpletely different in the I Case of ethylene copolymers of low crystallinity, that is to pay those whose crystallinity, determined by is lover than or equal to X-ray diffraction, ί approximately 30%.

I ί t In this case, in fact, an Appreciable deterioration in the optical properties of the films is noted proportions (which due to the fact that much higher can go up to 10%J of the IE 91571 conventional additives would be necessary to reduce the blocking to an acceptable level, in some extreme cases such as, for example, that of a copolymer containing 70% by weight of e thylene and 30% by weight of methyl acrylate, not onljf are the optical properties greatly degraded but also -the blocking remains 25 times higher than the generally accepted level, despite the addition of 10% of a usual ^antiblocking filler such as talc.

A first problem which the invention is aimed at solving consists therefore in choosing a filler which, when incorporated in an ethylene copolymer of l!i 2( low crystallinity such as defined above, makes it possible to avoid the blocking phenomenon without, j however, appreciably deteriorating the optical and/or ί mechanical properties of the films extruded from this | eopolyioer.

Furthermore, the slippery nature of a thermoplastic is a.so an important parameter for the - conversion industry, where it is necessary to avoid the * btickipg of the stock in the guidance systems of automatic machines. This slippery nature ls generally evaluated using a static or dynamic friction coefficient on the outer face, which measures the ratio of the traction fo::ce to be applied to initiate or maintain the sliding of the two faces to the force which Applies them ^against each other. For a regular use, without difficulties in manufacture, most conversion machines require a coefficient of friction IE 91571 on th$ outer fade not exceeding approximately 0.2.

Until now thia feiult has been achieved by incorporating int< the ethylene polymer a mixture of » metal; salt and Of fatty acid and of a saturated fatty amide, for example a mixture of sine stearate and of :erucaAide. While Iping efficient, this solution has the practical disadvantage of making it necessary during the conversion to .meter out and monitor two ingredients XO, in very low proportions in relation to the plastic forming-the main constituent. .3 [ λ sOcpna problem which the invention is aimed at solving consists therefore in choosing an additive f which, when incorporated into aa ethylene copolymer of . low crystallinity such as is defined above, makes it ethylpne copolyae } possible by ltsel:! to achieve a coefficient of static I * or dynamic f ricti< n on the outer face not exceeding j .approximately 0.a t I ; The present invention is based on the ·. ί .surprising discovery that the two problems set out j|o : above, can be solved simultaneously by incorporating an ' effective quantft;r of ethylenebisoleaiai.de containing an of low crystallinity· A first subject of the present invention relates, therefore, to a slippery, antiblocking and 45 optical quality composition comprising at least one ethylene copolyine:· with a crystallinity not exceeding approximately 30% characterised in that it additionally codapj rises .an effective quantity of ethylenebisoleamide of formula» o o || jl CH,~ { 0¾ j ,-CH-CH- ( CH,)' 7 -C-HH- ( CH, ) ,-NH-C- ( CH,) t-CH^CH- ( CH,) ,-CH, $: ; I An effective Quantity means a quantity which le sufficient to reduce the blocking and/or the coefficient of dynamic or static friction on the outer < j J face of the composition to a level which is acceptable for the convefsioxj of the said composition as a .function of the characteristics of the conversion fa , machine and ai i function of the intended final application. la the majority of cases the required properties are» L 1 I· coefficient of static or dynamic friction on the uter fade not exceeding approximately 0.2* < blocking, determined according to the method described below, not exceeding a value of approximately 20 g, |tn optical hase* determined according to ASTM standard D-1^03, not exceeding approximately 13%. Among the ethylene copolymers of lew lidh can form part of the constitution crystallinity whit of th^ composition according to the invention there may be mentioned especially polar ethylene copolymers which have a comonomer content of at least approximately 0.09 jnol per 100 1 of copolymer* such ass copolymers] of ethylene and of at least one alkyl acrylate o£ nethacrylate whose alkyl group has Irota 1 to 10 carbon atoms (these Inoluding » particularly j ethylene/methyl acrylate copolymers Containing at least 8% hy weight of acrylate, i yopolymers of ethylene and of at least one vinyl ester of a saturated carboxylic acid containing 2 po 5 carboh i tems, such ae vinyl acetate or vinyl propionate, ethylene/apq 1 (meth) acrylate/unsaturated dicarboxylic acid anhydride terpolymers (comprising lp to 15 mol% of (meth)acrylate and up to 3 molt pf^anhydride such as maleic anhydride) Such as are lescribed in Patent FR-A-2,498,609, Othylene/uns.turafced glycidyl monomer copolymers i fknd ethylene/uns atur ated ethylenic itonomer/unsaturated glycidyl monomer terpolymers pomprieing up to 50% by weight of a glycidyl honomer suchjas glycidyl methacrylate and acrylate, mono- and di glyc idyl itaconate, mono-, di- and trigiycidyl butenetrlcarboxylate and, if appropriate, up to 45% by weight of an ethylenic 'as a vinyl ester of a saturated carboxylic acid containing from 2 to 6 carbon atoms, an aeirylate or methacrylate of a saturated I Alcohol containing from 1 to 8 carbon atoms or an ester of mal|ic acid with a saturated alcohol Containing from 1 to 18 carboh atoms, such as are monomer such ip described in patent FR-A-2,130,279, ethylene/unsatUrated dicarboxylic acid anhydride/polyol poly (meth) acrylate copolymers (comprising up to 3 molt of anhydride, up to by reacting an aminoalkylcarbOxylic acid with an i ithylene/alkyl (meth) acrylate/unsaturated lcarboxy lie acid anhydride terpolymer at a iemperatur$ cf between 150* and 300*C. ί Among the ethylene copolymers of low 'crystallinity falling within the scope of the present invention there may also be mentioned copolymers of ethylene and of a/ least one alpha-olefin containing from ? to 8 carbon atoms, whose density is not higher . than |>.91O, such net - popolymers o' density approximately between 0.905 fuid 0.910 in accordance with European Patent jfo. 070,220, . ! - jeopolyaere of density approximately between 0.890 IE 91571 '1 · i and 0.905* generally comprising from 5 to 10 molt of alpha-ole In, I jsopolymers o' density approximately between 0.860 'and 0.890* such as especially* μ polyolefin rubbers marketed by Mitsui under the trademark Tafmer·, consisting of copolymers of 78 to 92 molt of ethylene and 8 • | 1 to 22 molt of an alpha-olefin chosen from propylene and 1-butene, having a density of 0.860.to 0.890* having a residual crystallinity of 1 to 14t, a crystalline melting?temperature J of 75*C* which have a geometric mean molecular mass of 60 to 120 kg/ijtol and a polydispersity index of between 2.2 and 2.7, polyolein rubbers consisting of ethy 16iu/propylene and/or 1-butene copolymers having < melt index of approximately between 0.3 aftdJ15 dg/min and a density approximately between*0.865 and 0.88S, comprising from 77 to 91 melt of units derived from ethylene and from 9 to 33 molt of units derived from propyleie and/or 1-butene* characterised by a Crystal-ine melting temperature J of approximately between 100* and 125*C. Subsidiarily these polyolefin rubbers accordixg to the invention may be characterised by at least one of the ι IE 91571 ID followin' g elementex I a polydispersity index of approximately betjween 3.5 and 15, preferably approximately between 4 and 8, a geometric mean molecular mass (defined ie shown below) of approximately between $5 ’and 70 kg/mol, S relationship between the density d and th« content x (expressed in molt) of units derived from propylene and from 1buteae which is expressed by the double equation» 0.9084 X d + 0.002 x m 0.918 a Residual crystallinity (determined according to the method described below) Of ^approximately between 3 and 15%. 2.0 The crystalline melting temperature J means the temperature determined at the maximum of the melting curve aft^r crystallisation obtained hy subjecting the Copolymer sample to the following three:stage^process» . w meltihg 'at the rate of 8*C per minute from *C pp to 150*C, then k crystallisation at the rate of 8*c per minute » from 15( ’C to 10’C, then again i t· meltipg at the rate of 8*C per minute from ι *C up |o 150*C.

The residual crystallinity is determined by X-ray I The geometric mean molecular mass is defined by thJ mathematical relationship: 1-N ϊ H l°9io IQ i-l where is the freight fraction of material of mass and K-i$ the number of fractions eluted using permeable gel c/romatography.

Such polyolefin rubbers Can be obtained by a process consisting in copolymerising, at a temperature I approximately from 160 to 270 *C and at a pressure approximately from 400 to 850 bars, a gas stream containing approximately from 18 to 424 by volume of ethylene and approximately from 584 to 824 of propylene and/or 1-butene, in the presence of a liegler-type catalyst system comprising, on the one hand, at least one compound of a transition metal of groups IVB, VB, VIB and viii of the Periodic Classification and, on the other* hand, at le, ist one organoaluminium compound and. If appropriate, in the presence of at least one chain transfer agent. The catalyst systep may additionally IE 91571 io comprise at lea^t one aluminium or .magnesium halide. To obtai^i the copolymers which have the characteristics described above and in which the molar ratio of units derived from propyl ene /units derived from 1-butene exceeds 0.5, the composition of the gas stream subjected to the copolymerisation will be preferably such that the propylene/l-butene volume ratio exceeds approximately 0.3/ depending on the nature of the catalyst system employed. The choice of the latter, in fact,'has an influence, known to the specialist, on the relative reactivity of ethylene, propylene and 1-butene » * in the copolymerization and consequently on the tendency for thg units derived from propylene or else the units derived ι Cron 1-butene to be preferentially incorporated into'the maeromolecular chain.

The composition according to the invention may obviously comprise a mixture of two or more copolymers such as are described above. Besides one or more ^uch copolymers, the composition may also comprise another thermoplastic polymer in the case of which the blocking, slip ani optical property problems are 4 { usually solved by .means of other additives, such as especially» is an ethylene polymer or copolymer with a crystallinity which is higher than 30%, such as, for.example, high density polyethylene (approximately 0.96 to 0.97), radical low density^polyethylene (approximately 0.92 to IE 91571 t 0.93/ajd copplymere of ethylene and of at 1) least oi|e alpha-olefin containing from 3 to 8 carbon atoms, which have a density l I approximately from 0.91 to 0.95, ir + a propylene polymer or copolymer comprising « at least; 85 molt of units derived from propylenie and not more than 15 molt of units derived jfrom ethylene or from an alpha-olefin i : j containing from 4 to 8 carbon atoms. 1 The ethylene copolymer of low crystallinity forming part of the constitution of the composition according to thd invention generally has a melt index determined'at l90*C under 2.16 kg according to ASTK standard D-1238 - of approximately between 0.1 and 10 dg^min. The same applies, in the case of the ethylene polymer or copolyiner of a crystallinity which is higher than $0% which may! he present as a mixture with the ethylene copolymer’ of low crystallinity. 2ά 2i i. ' The proportion of ethylenebisoleamide to be '1 * Incorporated' into phe composition according to the invention depends £>n a number of parameters, especially* 1 i - the nature and the proportion of the 1 comonomers present with ethylene in the I copolyme.? of low crystallinity, - the melt index of the copolymer of low cry stall jnity, - the thickness of the measurement specimen, I I t 1 ίο * the l^ve'l of the required properties (blocking, slip, optical haze) and the i property compromise which is accepted aa a functiotj of the method of conversion of the composition and of the intended application of the converted article.

J * ) The cAoice of the proportion of j · ethyl^nebisoleaAid e is within the reach of the specialist, taking into account the following general ; . indications* in meet cases it is recommended to employ a proportion of ethylenebisoleamide which is proportionately higher* j> the lpw^r the crystal Unity of the ethylene copolymer, that is to say the higher the comonomer content and - when the comonomer is an alpha-olefin - the lower the density, - the higher the melt index of the ethylene copolymer of low crystallinity, - the lpwer the value expressing the required ' slip characteristic, according to the method described below.

In the 1 means of the use of not more than 0.8% by weight, preferably approximately 0.1 to 0.6% by weight, of ethylei labieoleamide relative to the ethylene copolymer of Ιοχ crystallinity.

Although the additional use of conventional the disadvantages recalled in the additives presents? preamble of the'present description, in some cases, if desired, it will be possible to add to the composition according to thg Invention» it least one -conventional antiblocking additive such as silica, talc or saturated fatty amide, preferably in a proportion not exceeding Approximated 1% by weight of the composition, and/or ) - at least ohe ’slip-improving additive such as a iatty acid metal salt (for example sine stearate), A saturated iktty amide (for example erucamide) or ethylenebi$s^earamide, preferably in a proportion hot exceeding approximately 1% by weight of the . » tempositlob.

Zn addition, the composition according to the invention may comprise, in a manner which is known per se, al least one conventional additive for ethylene copolymers , sue^t A art antioxidant such as, for example, a sterically hindered phenol, a mercaptan or a phosphorite, taltraviolet eradiation absorbers such as substituted >ensophenones, substituted £henylbene£>t: ria soles and sterically hindered pmines, extinguisherA such as nickel complexes, |ui inorganic or organic pigment such as sine oxide )>r titanium ^xide. d When thd composition according to the invention is intended for special applications such as, for example, the manufacture of films for agricultural use, which must o^fer a sufficient resistance to some climatic conditions {exposure to ultraviolet or I Infrared radiation), it may additionally comprise an effective quantity of one or more additives capable of I providing these special properties, for example: » - Approximately’ from 1 to 15* by weight of dehydrated kaolinite, in accordance, for example, with Patent US-A-4,075,784, with a view to forming a barrier ^o ’infrared radiation, - approximately from 0.5 to 4% by weight of iron oxide of gaann^ crystallographic form, in accordance, for example, with Patent I-R-A-2,347,4oL, with a view to manufacturing a thermal opaque film, *- aj mixture qf approximately from 10 to 200 ppm of an ionic Irion· salt and approximately from 10 to l'OGO ppm of sulphur, in accordance, for example, with Patent pjl-A-2,199,757, with a view to manufacturing1 a photodegradable film, - x’inc oxide,, in accordance, for example, with Patent BP-A-0Q6,049, with a view to manufacturing a, transparent' film for packaging products capable of being damaged by ultraviolet radiation, - a-mixture of biodegradable particles such as natural starch and of a substance capable of 1« undergoing Xuiooxidation to form a peroxide and/or a hydroperokiie, in accordance, for example, with Patent FR-A-2 252,385.

» The compositions according to the invention can be. prepared by, any means permitting the dispersion of etbylenebisolea tide and, if appropriate, the other addit^vps in th^ ethylene copolymer of low crystallinity. Xt is thus possible to employ an internal mixer, 'an* extruder or a calender, the mixing temperature being ’advantageously belcw 200*C and • j preferably at leas(t 120*C. t- 'The cdmpositions according to the invention find advantageous applications for the manufacture of sheet# yith a thicknesB of approximately between 1 and ma^apd, abovp all, for the manufacture of films with a thickness of Approximately between 10 and 500 μ»· ' I Sheet? comprising (a composition according to the invention can be Obtained by compression and injection moulding techniques. Films comprising a composition 2>0 according to the invention can be obtained by extrusion 1 ί through a flat die or else by blow-extrusion at a temperature which is preferably approximately between t t 100 cf and 180*C and with a blow ratio preferably approximately between 1.5 and 3.5. $5 · The examples below are given by way of illustration without limiting the present invention.

I KXAMPLEgl and 2 λ copolymer with a melt index (determined at I I 1.5 2.0 190*C under 2.16' kk according to ASTM standard D-1238) of 2.5 dg/min, containing 84.5% of ethylene and 15.5% by weight of saet'hyi acrylate is considered. This copolymer has a crystallinity, determined hy X-ray diffraction, of 19^. X parts hy weight of ethyl^nebisoleamide are added to 100 parts by weight of this do£olymer by mixing in a twin-screw Brabender I | mixer operating.at a temperature of H0*c and 150*C and at a speed of 4Q rev/ein. The mixture obtained is then lj>; extruded into filnj *ith a thickness of 50 ja on a Troesder B 30 extruder under the following conditions» I ι< ^edperattirA profile» 120*C to 170*C, ^ie diameter40 mm, - |ap» 1 mm, - i - blow ratio) 3·5, - screw speed» -90 revolutions per minute, - yaul-off s£e^dt 4 metres per minute.

The following are measured on the film » I obtained» ! - phe optical Aaze H, expressed as a percentage and determined according to the method of NF standard I 5« "1» I - pxe blocking .B, expressed ln grams and determined According to, the following method, described with Reference toJthe attached figure. A sample of film ‘μ) ie placed between two rectangular plates (2) And (3) 100 mm x 76 mm in else. The ends (4) and (5) of the fjLla extending beyond the plates are opened and jcantened to the outer part of the plates with an adhesive. The two plates are placed horizontally between the jaws (6) and (7) of a tensile testing machine. The upper plate (2) ie connected to |jie upper jaw (6) of the machine by zieans of a chain (8) permitting the plate to move ώ. all directions (Figure la). The plate (2) ie I then moved vertically at a speed of 35 am per minute, in .'a first stage (Figure lb) the method consists ±4 determining the force Fx needed to Separate the (two film layers. The second stage (Figure lc) consists in determining the force F, to ^e applied.to move the plate (2) once the two film ί 1 |ayers are separated. The blocking B is defined by the relationship B - Fx-Ft. j The t£ble below shows the properties obtained I · | as a function of the quant ity X of ethylenebisoleaaide. XXM&ixS 3 to,6* «jornoaratlvel The operating procedure of Example 1 is reproduced with' the same copolymer but with ethylpneblsoleakide replaced with: - a talc marketed by Talcs de Luzenao under the name 100 HOOS (fexamples 3 and 4), - ethylenebIsstearamide (Examples 5 and 6).

, The properties obtained as a function of the > j quantity X of additive are shown in the table below. 1. * » * I i 19 t Examples 1 1 1 : 2 3 4 5 6 , X B » H * 1 0.25 20 10.3 1 1 . 0.75 15 f j 8.8 1.0 180 15.6 5.0 20 49.4 0.25 60 9.3 0.75 20 14.9 1 « EXAMPLE 7. ) » 1 • A copolymer with a melt index (determined at 190*&under 2.16 kg according to A5TK standard D-1238) of 0.3 dg/min, Containing 84.5% by weight of ethylene | : and ip.5% by weight of methyl acrylate, is considered. This topolymer Jia^ a crystallinity of 19%. 0.5% by weight of ethylenebisoleamide are added to 100 parts of this dopolymer by!mixing under the conditions of ? : Example 1. The fixture obtained is then extruded into * t film yith a thickness of 180 pA under the conditions of ί J Example 1.

The following are measured on the film > . obtained* - I* dynamic fraction coefficient, determined according lo.NT standard T 54 112, equal to 0.06, Recording ]to - a blocking', determined according to the method > 1 I W t described inExample 1, equal to 6 g. "4* i I J The operating procedure of Example 7 ie reproduced with (the same copolymer but with ethylenebiaoleamldj} replaced with: - 1% of einc etearate (Example 8): in this case the dynamic f riot Lon coefficient is equal to 0.87 and t the blocking is equal to 8 g, - O'. 5% of ethyl’nebisstearamide (Example S)» in this case the dynaoic friction coefficient is equal to 1.20 and the blocking is equal to 30 g, - 4 fixture of 1% of talc, 0.25% of ethylenebisst I ί coefficient is equal to 0.87 and the blocking is equal to 5 g.] I I i £ ft *

Claims (8)

1. CLAIMS ; , i

1. Slippery, antiblocking and optical « quality composition comprising at least one ethylene copolymer with a crystallinity not exceeding 30%, j characterised in that it additionally comprises an effective quantity of ethylenebisoleamide. »

2. Composition according to Claim 1, characterised in that the ethylene copolymer is a polar copolymer of ethylene which has a Comonomer content of lb at least 0.09 mol per 100 g of copolymer. , }

3. Composition according to Claim 2, characterised in that the polar copolymer of ethylene is chdsen from the' copolymers of ethylene and of at least 'one alkyl acrylate or methacrylate whose alkyl 1$ group has from l tb 10 carbon atoms, the copolymers of ethylene and of at· least one vinyl ester, ethylene/alkyl (methacrylate/unsaturated dicarboxylic acid anhydride terpolymers, ethylene/unsaturated glycidyl monomer cbpolymers and ethylene/unsaturated 20 ethylenic monomer/unsaturated glycidyl monomer ’ j terpolymers, ethylene/unsaturated dicarboxylic acid anhydride/polyol poly (meth) acrylate copolymers and ethylehe/alkyl (meth) acrylate/unsaturated dicarboxylic acid N-CarboxyaIky1 imide copolymers. 25 4. composition according to Claim 1, characterised in that the ethylene copolymer is a I copolymer of ethylene and of at least one alpha-olefin containing from .3 to 8 carbon a terns, whose density is IE 91571 «y*·, id 2.0 not higher than jo.^10. • | 5. Composition according to one of Claims 1 , i to 4, Characterised in that it additionally comprises

4. · an ethylene polymer or copolymer with a crystallinity which is higher ‘than 30% or a propylene polymer or , , copolymer. { , r ι 6. Composition according to one of Claims 1 to 4, Characterised in that the ethylene copolymer has a molt' index of between 0.1 and 10 dg/min.

5. 7. Composition according to one of Claims 1 to 6, characterised in that it comprises not more than 4 * 0.8% by weight of ethylenebisoleand.de relative to the I ί ethylene copolyqer with a crystallinity not exceeding 30%, j

6. 8. Composition according to one of Claims 1 « to 7, characterised in that it additionally comprises | ‘I at least one additive chosen from antiblocking agents, slip-improving additives, antioxidants, ultraviolet I .: ’ radiation absorber's, extinguishers end inorganic and organic pigment^. > I · j

7. 9. £ilm with a thickness of between 10 and 500 /«4 1 , obtained from a composition according to one of Claims ι to

8. '