WO1985000172A1

WO1985000172A1 - Procedure for making copolymers of ethylene and long-chained alpha olefins

Info

Publication number: WO1985000172A1
Application number: PCT/FI1984/000045
Authority: WO
Inventors: Jukka Seppälä
Original assignee: Neste Oy
Priority date: 1983-06-22
Filing date: 1984-06-21
Publication date: 1985-01-17
Also published as: GB2152517A; US4690991A; FI68632C; NL190666C; JPS60501609A; GB8502724D0; NL190666B; FI68632B; JPH0699524B2; BE899984A; DE3490300T1; FR2549073A1; FI832287A0; FR2549073B1; NL8420184A; IT8421468A0; DE3490300C2; IT1175515B; FI832287L; IT8421468A1

Abstract

A procedure for copolymerization of ethylene and alpha olefins with at least eight carbon atoms in the presence of a catalyst of Ziegler-Natta type to become a polymer in which the quantity of alpha olefin containing at least eight carbon atoms can be regulated between 0.01 and 15% by weight. Polymerization is carried out at a temperature not exceeding 120oC in a fluid in which the polymer is insoluble. The monomer mixture contains, for increasing the reactivity of the long-chained alpha olefin, 0.01 to 2.0 mol/dm3 of short-chained alpha olefin with not more than five carbon atoms. The alpha olefin containing not more than five carbon atoms is 1-butylene or propylene.

Description

Procedure for making copolymers of ethylene and long-chained alpha olefins

The present invention concerns a procedure for making mixed polymers of ethylene and long-chained alpha olefins. To be more precise, the invention concerns a procedure for making copolymers of ethylene and long-chained alpha olefins in which the density and melting point of the polymer can within given limits be regulated independent of each other and in which the quantity of long-chained alpha olefin can be easily regulated in a wide range in suspension polymerization.

For copolymerizing ethylene with olefins with the purpose of making LLDP (linear low density polyethylene) a number of commercial procedures are known in prior art, in which the most commonly used alpha olefins are 1-butylene and 1-octylene. In suspension and gas phase polymerization, 1-butylene is as a rule used, whereas in solution polymerization 1-octylene is used. The tensile strength, tearing strength and piercing strength of films made from copolymers are as a rule better when the comonomer is a long- chained alpha olefin, and it is therefore advantageous to be able to include them in the polymer.

Copolymerization of ethylene and long-chained alpha olefins containing more than eight carbon atoms by solution and gas phase polymerizing is commonly known in the patent literature. In suspension polymerization, in contrast, long-chained alpha olefins containing more than eight carbon atoms could not be used because at the low temperatures employed, the reactivity of long-chained alpha olefins is not sufficient. If it is specifically desired to make copolymers in which the quantity of long-chained alpha olefin is relatively high, one would have to use excessively high alpha olefin monomer contents in suspension polymerization. This, however, entails the drawback that the polymer being produced swells and the reactor gets dirty. The proportion of long-chained alpha olefin in the polymer still cannot be made high enough in this way. As a result, the making of copolymers of ethylene and long-chained alpha olefins by suspension polymerizing is not commercially practised, and even in other methods the use of copolymers with more than eight carbon atoms is not often presented, not even in the examples of patent specifications.

According to the invention, it has been unexpectedly found, that by polymerizing ethylene and alpha olefins containing at least eight carbon atoms by the suspension method at a temperature under 120°C it is possible in a simple way to increase the reactivity of long- chained alpha olefins. Since in this instance no excess of the long-chained alpha olefin monomer need be used, swelling of the polymer that is obtained and soiling of the reactor are also avoided. Through the increase of reactivity, the proportion of long-chained alpha olefin in the polymer can be significantly increased.

The procedure of the invention for making mixed polymers of ethylene and alpha olefins containing at least eight carbon atoms in the presence of a catalyst of Ziegler-Natta type to become mixed polymers in which the quantity of alpha olefins containing at least eight carbon atoms can be regulated within 0.01 to 15 per cent by weight is characterized in that polymerization is carried out at a temperature not higher than 120°C in a fluid in which the polymer that is produced is insoluble, and that the monomer mixture contains, to the purpose of increasing the reactivity of the long- chained alpha olefin, 0.01 to 2.0 mols per dm³ short-chained alpha olefin with no more than five carbon atoms.

The use of monomer mixtures containing long-chained alpha olefin and 1-butylene is not in itself unknown in the art. For instance, in the European Patent Application No. 0 010 428, a procedure is disclosed for mixed polymerizing of ethylene, alpha olefin containing 3-4 carbon atoms and long-chained alpha olefin containing 5 to 18 carbon atoms. In the procedure solution polymerization is utilized at a comparatively high temperature, 130-220°C. However, said publication presents no examples regarding the use of alpha olefins containing more than eight carbon atoms, nor has the effect of 1-butylene on the reactivity of the long- chained alpha olefin been observed in any way.

In the German application print No. 30 19 871 is described a two- phase polymerization where in the first phase ethylene is copolymerized in suspension in a fluid containing 3-4 carbon atoms. The monomers are in said procedure preferably alpha olefins containing 3-4 carbon atoms or mixtures thereof. In the second phase of the procedure, the fluid is evaporated off and the reaction is continued as a gas phase polymerization. The comonomers are in this procedure defined as having a length not greater than ten carbon atoms, and no advantage is stated to be gained by simultaneous use of a short-chained and a long-chained alpha olefin.

The German Patent No. 29 47 921 concerns the manufacturing of medium or low density copolymers of ethylene using alpha olefins, by gas phase polymerizing. According to the publication, the polymerization is carried out with ethylene and propylene and/or 1-butylene and alpha olefins containing 6 to 12 carbon atoms. Hereby, polymers are obtained with density 0.900-G.945 kg/dm³. The use of heavy hydrocarbons is, however, impossible in the gas phase because long-chained alpha olefins have a low vapour pressure.

None of the references cited above reveals the observation constituting the basis of the present invention: that copolymers of ethylene containing higher contents than before of long-chained alpha olefin can be made by suspension polymerization if at polymerizing a short-chained alpha olefin is present, for instance 1-butylene, even if in minimal amount. The 1-butylene causes the reactivity of the long-chained alpha olefin to be much higher than if no 1-butylene is present. Said copolymers have therefore an obvious interaction on each other.

Particularly surprising is the observation of the invention that the increase in reactivity of the long-chained alpha olefin is strongest when the 1-butylene content is very low. Therefore, in the polymer being produced the proportion of long-chained alpha olefin can be varied within very wide limits by the aid of small 1-butylene additions.

Thus, according to the invention the possibility is gained to regulate within certain limits the properties of the polymer that is being produced. First, the melting temperature of the product is determined according to its 1-butylene content. The melting point does not essentially change as the quantity of long-chained alpha olefin increases. Secondly, the crystallinity of the product decreases with increasing content of long-chained alpha olefin. This causes further that the density decreases powerfully from the value typical of ethylene/1-butylene copolymers when the content of long-chained alpha olefin increases and that of 1- butylene remains constant in the monomer mixture. In this way by suspension polymerizing, mixed polymers with low density can be obtained. In addition, the mechanical properties of the product are excellent.

By the method of the invention, mixed polymers of ethylene can be made by the suspension procedure having densities down to 0.900 kg per dm³ and which may contain up to 15 per cent by weight of long- chained alpha olefin containing at least eight carbon atoms, preferably at least ten carbon atoms, or a mixture thereof.

By low pressure suspension polymerization, ethylene/alpha olefin copolymers can be produced which have density less than 920 g/dm³, even 90-910 g/dm³.

From the polymer produced according to the procedure, mechanically strong film is obtained which has ultimate tensile strength 30-60 MPa, even 80 MPa.

In the procedure of the invention, polymerization is carried out in a hydrocarbon suspension. For fluid, any liquid hydrocarbon may be used which is inert towards the monomers. A suitable hydrocarbon fluid is for instance n-heptane. The reaction temperature in the polymerization is selected in the range 0-120°C , preferably in the range 70-90°C.

The alpha olefin contents in the reaction mixture depend on how much alpha olefin is desired in the product. As a rule, the monomer supplied into the polymerizing reactor contains 1-butylene

0.01-2.0 mol/dm³ and long-chained alpha olefin 0,1-2 mol/dm³.

The long-chained alpha olefin contains at least eight carbon atoms, preferably at least ten carbon atoms. With alpha olefins containing less than ten carbon atoms, the increase of reactivity is not yet significant, neither are the characteristics of the polymers as good as when using alpha olefins containing at least 10, preferably 12-16 carbon atoms. Alpha olefins may, of course, also be used in mixture. Examples of suitable alpha olefins are, for instance: 1-decylene, 1-undecylene, 1-dodecylene, 1-tridecylene, etc. When the number of carbon atoms rises over 20, the respective alpha olefins are solid at room temperature already and therefore no longer competitive as to their price in the procedure of the invention.

The reaction pressure in the polymerizing reactor is usually kept on the same level as in general in suspension polymerization of ethylene, that is, at 0-70 bar gauge pressure.

For the catalyst in the polymerizing process catalysts of the same type are used as in general in coordination polymerizing ethylene. Catalysts of this kind belong to the coordination catalysts and they are thus complexes composed of organometallic compounds of groups I-III and of a transition metal salt of groups IV-VIII. TiCl₃, complexes of 1/3 A1C1, and Et₃Al are highly appropriate catalysts in the procedure of the invention. Also the use of various carrier catalysts is possible, as it is in general in coordination polymerization of ethylene. EXAMPLES

Performing the polymerizations

In a nitrogenated 4 dm³ reactor, 3 dm³ dried heptane were introduced. The heptane was nitorgenated for about half an hour for removing the dissolved oxygen, if any. The catalysts prepared in a nitrogen chamber were added through the cover of the reactor.

First aluminium alcyl, then the titanium compound. When liquid comonomers were used they were added after the catalysts with a syringe through the cover of the reactor. The reactor was closed, and the gaseous comonomer to be used (I-butylene) was added. Hydrogen was added to bring its partial pressure to desired level. The reactor was heated to the polymerization temperature and with ethylene supply the pressure was kept at the polymerizing temperature chosen. With oil circulating in the jacket of the reactor, the temperature of the reactor was kept at the polymerizing temperature chosen.

On completion of the polymerizing time, the supply of ethylene was discontinued and the reactor was cooled. The produced polymer sludge was removed from the reactor through a bottom valve. To it was added 2 dm³ isopropanol for deactivating the catalyst. The mixture was filtrated through a sinter, and the polyethylene thus obtained was washed with 2 dm³ of heptane and with 1 dm³ of a 10 % by weight mixture of hydrochloric acid and methanol until no more chloride was precipitated from the filtrate by silver nitrate. The polymer was dried to constant weight either in a heating chamber or in a fluidized bed drier. The temperature of the heating chamber was 80°C and the temperature of the blast air in the fluidized bed drier was 60°C.

Example 1

In the manner as above, polymerization was carried out in a half- charge type 4 dm³ mixing reactor. The coordination catalyst was composed of aluminium-activated titanium chloride (TiCl₃ x 1/3 A1C1₃) and triethylaluminium chloride. The quantities used were respectively 0.93 mmol and 2.04 mmol. The fluid in the reactor was

3 dm heptane.

Into the reactor were added 0.48 mol/dm³ 1-butylene and 0.48 mol/dm³ of 1-decylene. The partial pressure of hydrogen in the reactor was adjusted to be 300 kPa. The temperature in the reactor was maintained at 80-83 C, and the pressure was kept constant.

After two hours' reaction time, 415 g polymer were obtained. In the polymer, the weight proportion of 1-decylene was 5.7 per cent by weight. Melting point 127°C, crystallinity 48 %, density 925 g/dm³.

Example 2

Copolymerizing was carried out as in Example 1, but the 1-butylene was omitted from the reaction mix. The conditions of reaction are given in Table 1. The yield was 463 g polymer with 1-decylene content lower than 3 % by weight. The product that was obtained was close to HDPE, having density 946 g/dm³, crystallinity 64 % and melting point 135°C.

Example 3

Copolymerization was carried out in the same way as in Example 1, except that only 1-butylene was used for comonomer, at 48 mol/dm³. The polymer yield was 377 g and density 928 g/dm³. The melting point was 127°C and crystallinity 48 %.

Examples 4, 5, 6, 7 and 8

Under the conditions specified in Table I, and otherwise as in Example 1, copolymers of ethylene, 1-butylene and 1-decylene were prepared. The properties of the products have been compiled in

Table II. The lowest densities reached in the series were

914 g/cm³, the copolymer then containing 13.5 % by weight of

1-decylene. Example 9

At the temperature of 80°C, ethylene and 1-decylene were polymerized with the catalyst quantities stated in Table I and otherwise as presented in Example 2. The polymer yield was 185 g and density 940 g/cm³. The crystallinity was 59 % and the melting point, 130°C.

In Table I are given the polymerizing conditions applied in Examples 1-9 and in Table II, the properties of the polymers obtained. The test results reveal that by adding 1-butylene to the reactor the 1-decylene could also be made to react. Thereby the values of crystallinity, density and melting points also clearly changed.

Example 10

Copolymerization was carried out as in Example 1, however so that the long-chained alpha olefin was 1-dodecylene. 580 g polymer were obtained, with melting point 127°C, crystallinity 38 %, density 913 g/dm³. By ¹³C NMR analysis, the 1-dodecylene content was found to be 8.5 % by weight.

Example 11

Copolymerization was carried out as presented in Example 10, but using for comonomer only 1-dodecylene. 420 g polymer was obtained, with melting point 136°C, crystallinity 67 % and density over 944 g/dm³. The 1-dodecylene content in the polymer was less than 3 % by weight.

Example 12

Copolymerization was carried out as in Example 1, however so that the long-chained alpha olefin was 1-hexadecylene. 222 g polymer was obtained, with melting point 125°C, crystallinity 38 % and density 913 g/dm³. The 1-hexadecylene content in the polymer was found to be 11 % by weight.

Example 13

Copolymerization was carried out as in Example 1 , however so that for comonomer was used only 1-hexadecylene. 40 g polymer was obtained with melting point 137°C, crystallinity 65 % and density 943 g/dm³. The 1-hexadecylene content was so low that it could not be quantitatively observed in the ¹³C NMR spectrum, I.e., it was less than 0.5 % by weight.

Example 14

Copolymerization was carried out as in Example 1, however so that the long-chained alpha olefin was 1-octylene. 90 g polymer was obtained, with melting point 125 C, crystallinity 41 % and density 917 g/dm³. The 1-octylene content in the polymer was found to be

5.7 % by weight.

Example 15

Copolymerization was carried out as in Example 2 with the exception that for comonomer only 1-octylene was used. 156 g polymer was obtained, with melting point 129°C, crystallinity 56 % and density 936 g/dm³. The content of 1-octylene in the copolymer was found by analysis to be 3.9 % by weight.

In Table III are presented the polymerizing proportions used in Examples 10-15 and in Table IV, the properties of the polymers obtained.

Example 16

A test series was carried out in which the quantity of long-chained alpha olefin (1-dodecylene) in the monomer mixture was kept constant (0.48 mol/dm³) and the quantity of 1-butylene was varied in the range of 0-0.65 mol/dm³. The polymerization was accomplished as in Example 1. In Table V, the characteristics of the polymers obtained are presented. In the figure is shown the dependence of the 1-dodecylene content of the polymer on the

1-butylene quantity added into the reactor.

Table V and the figure reveal clearly that even the 0.06 mol/dm³ 1-butylene addition sufficed to raise the 1-dodecylene content of the polymer from the level under 3 % by weight to the level of 7-10 % by weight. The density has decreased from the level

939 g/dm³ to below the level of 926 g/dm³. In the test series, even one density as low as 908 g/dm³ was achieved.

Claims

1. A procedure for copolymerizing ethylene and alpha olefins with at least eight carbon atoms in the presence of a Ziegler-Natta type catalyst to become a copolymer in which the quantity of alpha olefin with at least eight carbon atoms can be regulated in the range of 0.01-15 % by weight, characterized in that polymerizing is carried out at a temperature not higher than 120 C In a fluid in which the polymer that is produced is insoluble, and that the monomer mixture contains, to the purpose of increasing the reactivity of the long-chained alpha olefin, 0.01-2.0 mol/dm³ of short-chained alpha olefin containing not more than five carbon atoms.

2. Procedure according to claim 1, characterized in that the alpha olefin with not more than five carbon atoms is 1-butylene or propylene.

3. Procedure according to claim 1, characterized in that the density of the copolymer is selected by changing the content of alpha olefin containing more than eight carbon atoms.

4. Procedure according to any one of the preceding claims, characterized In that the long-chained alpha olefin is 1-decylene, 1-undecylene, 1-dodecylene, l-trldecylene, 1-tetradecylene, 1-pentadecylene, 1-hexadecylene, 1-heptadecylene, 1-octadecylene, 1-nonadecylene, 1-eikocylene or a mixture containing these monomers.