DE2135044A1 - AETHYLENE POLYMERISATE WITH HIGH MOLECULAR DISCONNECTION AND THEIR PRODUCTION - Google Patents

Description

Gelsenkirchen-Buer, July 7, 1971

Veba-Cbemie Aktiengesellschaft Gelsenkirchen-Buer

Ethylene polymers with high molecular non-uniformity and their production

The invention relates to a particular polyethylene with unusual and extremely beneficial properties. It also relates to corresponding copolymers of ethylene and butene- (1) a content of butene- (1) copolymer of 0.1 to 5% by weight. aside from that The present invention relates to a process for the production of these novel ethylene polymers or copolymers.

Their crystallinity is essential for the mechanical properties of ethylene polymers. A measure of this is the density determined under standardized conditions, which in turn is a function of the average molecular weight. The tensile strength, the surface hardness, the rigidity, for example, depend on the crystallinity or density - that is, the properties that are essential for the practical application of the material as a plastic. Another very important key figure is the molecular non-uniformity. This is understood to mean the quotient of the weight average and the number average of the molecular weights, reduced by 1. This numerical value U depends on the method of determination, and in the following only molecular irregularities determined by gel permeation chromatography are mentioned. The gel permeation chromatographic investigations were carried out in a device from Waters Associates, model 200 with Styragel (trade name from Water Associates for a polystyrene) in 1,2,5 trichlorobenzene as solvent at 135 ^° C.

- 2 -

31

Important factors depend on the non-uniformity, such as the processability on extruders to, for example, hollow bodies in the blow molding process. If the molecular non-uniformity is too low, a very annoying, disruptive phenomenon occurs during extrusion, which is referred to as shingle fracture and is noticeable in a structured surface with an undesirable appearance. Finished parts with melt fracture are unsaleable and therefore rejects. It is only possible to a "very limited extent" to eliminate melt fracture by increasing the processing temperatures. For many applications, such as for detergents packaging, b, it is necessary that the plastics a high stress aufweisenβ suitable for this purpose polyethylenes with good environmental stress could only be produced so far that oC-olefins j, such as propylene and butene (1) or hexene (1) can be copolymerized by known processes, the disadvantages of which, however, are a reduction in crystallinity and thus a deterioration in the properties dependent thereon; this is because an effective increase in stress cracking resistance has so far only been found in products whose density has been reduced to at least about 0.950 g / ml by the copolymerization.

* According to the prior art, polyethylenes are known with densities of about 0.91 g / ml to about 0.97 g / ml and molecular non-uniformities (^ _W / M _n ) -1 of about 3 to about

Compared to this prior art, the inventive Polyethylene made a very significant advance.

Protection is therefore sought for a polyethylene with gel permeation chromatography determined molecular unevenness of U = 20, which at the same time has a density of 0.963 g / ml to 0.98 g / ml having.

2Ü9884 / 1131

Protection is also sought for copolymers of ethylene and 0.1 to i 5% by weight of copolymeric butene- (1) with a gel permeation chroma- I graphically determined molecular non-uniformity of U * 20 and a density of at least 0.958 g / ml.

It will continue to demand protection for a method of making \ this Äthylenpolymerisate. ·

According to the state of the art, polyethylene can be produced by radical polymerization of ethylene at pressures from 2000 atmospheres to 4000 atmospheres. Polyethylenes are used with low density and generally only low stress cracking resistance.

It is also known to produce polyethylenes and copolymers of ethylene and butene- (1) with oxidic catalysts of VI. Subgroup of the Periodic Table · These processes are known under the name Phillips and Standard Oil processes. After these Processes can produce higher density polyethylene.

It is also known that ethylene and / or oil olefins with catalysts on the one hand transition metal compounds of IV. - VI. Subgroup and on the other hand organometallic compounds of I. - III main group of the periodic table of high molecular weight plastic-like products with densities in the range from about 0.940 to 0.960 can be polymerized. These processes are known as the Ziegler process. In this Ziegler process for Ethylene polymerization is preferably used as catalysts made from compounds of titanium and organoaluminum compounds, such as Trialkyl aluminum or alkyl aluminum halides. Also ground often vanadium compounds, also in combination with titanium compounds, used together with aluminum alkyl compounds. The εν / pus are also catalysts made from chromium compounds and Obtained aluminum alkylene. Usually the polymerization

- 4 -209884/1131

2135Ü44

carried out using inert hydrocarbons as solvents or dispersants. Ethylene partial pressures of fractions of an atmosphere, but also up to 100 and more atmospheres, can be used, but ethylene partial pressures of 20 to 40 atmospheres are preferably set. Polymerization temperatures of approx. 20 to 150 ^° C. are possible. Appropriate polymerization temperatures are between about + 4O ⁰ C and +90 ⁰ C, however, occurs according to the temperature sensitivity of the catalyst even at temperatures deviating from a polymerization. It is often useful to regulate the molecular weights of the resulting polyethylene by adding a molecular weight regulator, for example hydrogen, in order to obtain products with melt viscosities suitable for further processing into finished plastic parts.

It has also been proposed to apply chromyl chloride on an insoluble inorganic support with high surface area adsorb or deposit and the thus prepared chromium-containing solid with an organic aluminum reduction bond with at least one hydrocarbyl group and not more than two oxyhydrocarbyl groups, which are bound to the aluminum, in one for the reduction of at least part of the chromium in the valence state of +2 sufficient amount to be brought into contact. The yields are very low.

In contrast to this, in the process according to the invention for producing the claimed ethylene polymers, chromyl chloride is neither reacted with a silicon component nor adsorbed on it, but an organometallic mixed catalyst of the Ziegler type is produced by reacting the chronryl chloride with trialkylaluminum in the presence of a finely divided silicon component. The mode of action of aes in relation to the starting components, which is practically inert, has not been clarified. The surprisingly beneficial effects of the

- 5 209884/1131

2! 35OU

Additional component on the catalyst activity and the properties of the polymers, such as molecular weight distribution, density, surface hardness, rigidity and resistance to stress cracking. These benefits were not found in the prior art ^v belonging procedure.

It is also noteworthy that the bulk density of the powdery polyethylene formed during the polymerization by the Addition of the silicon component can be increased significantly. Furthermore, the addition of the silicon component has a beneficial effect the flow behavior of the powdery polyethylene.

The present invention therefore also relates to the production of the claimed ethylene polymers, optionally mixed with 0.1 to 5% by weight of butene- (1) in the presence of molecular hydrogen using a catalyst of the Ziegler type composed of chromium compounds and organoaluminum compounds, characterized in that, that for the polymerization a catalyst of chromyl chloride and trialkylaluminum of the general formula FUAl, in which R any alkyl radicals with 1 to 8 carbon atoms is used, which is in a saturated aliphatic or aromatic, liquid hydrocarbon is formed in the presence of disperse silica or silicon dioxide.

The weight ratio of the silicon component added to Chromyl chloride can be between 30: 1 and 190: 1, preferably between 60: 1 and 100: 1. The molar ratio of Trialkylaluminum to chromyl chloride is not critical and is preferably adjusted between 10: 1 and 20: 1.

The printing and timing conditions are the same as those above Information on the Ziogler process.

- 6 ~
2Ü9Ü8A / 1131

The preparation of the catalyst for the novel process for the preparation of the claimed Äthylenpolyinerisate may be such that a preferably to ⁰ ° C to -20 ⁰ C cooled solution of chromyl chloride in a hydrocarbon, such as neopentane, n-pentane, η-hexane, n- Heptane or benzene, with the exclusion of air and moisture, is mixed with the powdery, insoluble silicon component. There is no recognizable reaction or adsorption of the chromium component. Then a trialky aluminum, preferably triethyl aluminum, is added. Immediately thereafter, the catalyst fc is available for the ethylene polymerization according to the invention. The polymerization is conveniently carried out in an inert hydrocarbon solvent or dispersant, as it is also used in the catalyst preparation, with pressures preferably between 20 and 40 atmospheres and polymerization temperatures of 20 C to 150 ⁰ C, preferably 40 ⁰ C to 90 ° C , carried out in the presence of molecular hydrogen. After the polymerization has ended by letting down the pressure and, if necessary, cooling, the polymer is separated off from the liquid hydrocarbon used as solvent or dispersant by filtration or centrifugation and dried.

. As a result of the high activity of the catalyst according to the invention ™ there is no need to extract the catalyst components will. The catalyst residues remaining in the product are so small that when using those prepared according to the invention Ethylene polymers or copolymers as plastics do not have any disadvantages, such as discoloration, accelerated aging or corrosion occur on the processing machinery.

It has surprisingly been found that catalysts prepared in this way from chromium compounds and aluminum trialkyls have higher activities than catalysts prepared analogously without silicon component. It was also found that

- 7 209884/1131

"During the polymerization according to the invention, no wall coverings occur in the polymerization reactor, while during the polymerization with catalysts prepared analogously without the addition of the silicon component Wall coverings soon emerged, causing annoying disruptions due to blockages and sintering of the reactor contents as a result of obstruction give cause for heat dissipation. The inventive method of ethylene polymerization enables the production of plastic-like polyethylene with excellent properties that have not yet been known from polyethylene. The products have an extremely wide molecular weight » / grant and even with high weight average molecular weights extremely high densities. Due to the broad molecular weight distribution with With a high, low-molecular content, the product is suitable for melt fracture-free processing on extruders - especially in the blow molding process to large hollow bodies - suitable in an excellent manner, as is the case with state-of-the-art polyethylene is not known. The densities of the polyethylene produced according to the invention are also above the level of the prior art Technique belonging polyethylene. The density-dependent properties, such as surface hardness and rigidity, are correspondingly excellent. The economic advantages of products with such properties are obvious: For example, the Finished parts are manufactured relatively low processing temperature with a larger number of picks and with thinner wall thicknesses than it with the polyethylene belonging to the state of the art is possible. This means material savings, more economical production and thus lower costs. Furthermore, this enables according to the invention Ethylene polymerization processes open up new areas of application for polyethylene, especially in the technical sector. Despite the extremely high density, that produced according to the invention possesses Polyethylene has a surprisingly high resistance to stress cracking. To achieve the same good resistance to cracking cracks es.sonst required, ethylene with propene or preferably

- 8 2 U 9 8 8 A / 1 1 3 1

To copolymerize butene (1) or hexene (1) by known methods. However, this reduces the surface hardness and rigidity even further. On the other hand, it is through that Process according to the invention of ethylene polymerization has become possible to avoid these disadvantages. Of course, after the process according to the invention can also be copolymerized. Copolymerization of ethylene with butene- (1) is in itself already good stress cracking resistance of the polyethylene according to the invention is further improved without the density and thus the density-dependent ones Properties are reduced as much as in the copolymerization belonging to the prior art.

The following examples serve to illustrate the invention Products as well as their manufacture and are in no way limiting.

Examples 1 to 4

A - Manufacture of the catalyst

With exclusion of air, 7.75 mg of chromyl chloride were added to a suspension of the amounts of silicon dioxide given in Table 1 (trade name - Aerosil 380 from Degussa) in 50 ml of benzene distilled over sodium. This mixture was transferred to a 2 1 steel autoclave to 1 1 65 mg of triethylaluminum containing Hexanschnitt 60 / 8O ⁰ C with stirring.

B - polymerization

Immediately after the catalyst had been prepared, 6.4 ata of hydrogen were injected and then up to a total pressure of 32 ata ethylene. At the same time the contents of the reactor

- 9 209884/1131

heated to 7O ^{0 C.} The total pressure of 32 ata was maintained for 1 hour by forcing in ethylene. The reactor was then depressurized and, after the reactor contents had cooled, the polyethylene formed was filtered off and dried in vacuo. The yields are given in Table 1.

Table 1:

Polyethylene yield depending on the catalyst composition

example SiO ₂ Weight ratio Mole ratio yield kg PE / mgAtomCr mg SiO ₂ : CrO ₂ Cl ₂ Al: Cr G 1 250 32 11.2 50 1.0 2 500 64 11.2 90 1.8 3 750 97 11.2 95 1.9 4th 1500 190 11.2 20th 0.4

The properties of the obtained i to 4 in Examples 1 products are in the following Tables 2 and 2a together.

- 10 -

2Ü9Ö8A / 1131

-.10 -

Table 2:

Properties of the polymers obtained according to Examples 1 to 4

E.g. Weight average
the mole
weights
v ¹⁰ ~ ³ molecular
Inconsistency
opportunity
W ¹ Bulk density
g / cm- ⁵
DIN 53479 JR-A
_CH3 / 1000C dialysis
CH ₂ = CH / 1000 C 1 129 26.4 0.966 1.6 1.0 2 105 27.0 0.967 1.7 1.4 3 184 30.2 0.968 1.6 1.3 4th 308 39.8 0.999 1.6 0.3

Table 2a;

Test values for the products obtained according to Examples 2 and 3

characteristic Measurement method unit value Melt index DIN 53735 g / 10 min 0.31 5.0 kg load (Draft) Bulk density DIN 53479 g / cnr 0.967 Yield stress * DIN 53371 kp / cm 330 Tear strength * DIN 53371 kp / cni 200 Ball indentation hardness DIN 53456 kp / cm after 10 seconds 660 after 60 seconds modulus of elasticity DIN 53457 kp / cm 21 500 Torsional stiffness DIN 53445 kp / cm 9 800 Shear modulus ASTM D 1693-T hours 8 200

* determined on test rods made from panels according to DIN 53504

- 11 20988A / 1131

Examples 5 to 8

The procedure was as in Examples 1 to 4, except that 500 mg each of Aerosil and 7.75 mg of chromyl chloride were used. the The amount of triethylaluminum was, as indicated in Table 3, varied. The test results can be found in this table.

Table 3:

Polyethylene yield as a function of the activator concentration

E.g. mmol of triethyl Mole ratio yield kg PE / mgAtomCr aluminum pro Al: Cr g PE approach 5 0.28 5.6 32 0.64 6th 0.56 11.2 90 1.8 7th 0.84 16.8 55 1.1 8th 1.12 22.4 42 0.84

Comparative experiment A

The procedure was as in Example 1 A and B, but without the addition of Aerosil. The yield of polyethylene was only 15 g = 0.3 kg / ingAtomCr. The wall of the autoclave was firm with a adhesive polyethylene layer covered. The bulk density was only 210 g / l (in example 1 420 g / l).

- 12 -

209 884/1131

Comparative experiment B

The procedure was as in Example 2 A and B, but using of 120 mg of diethylaluminum n-propoxide instead of the triethylaluminum and without the addition of hydrogen. O g of polyethylene were obtained.

Comparative experiment C

The procedure was as in Example 2 A and B, but using of 44 mg of diethylaluminum n-propoxide and 22 mg of triethyl aluminum as an organoaluminum component. Only 25 g of polyethylene were obtained.

Example 9

The procedure was as in Example 2 A and B, but C was polymerized at 90 ^0th 73 g of polyethylene were obtained. The mean molecular weight was 145,000, the non-uniformity 20.8, the density 0.974 g / ml.

Example 10

The procedure was as in Example 2 A and B, but using an equiraolar amount of triisobutylaluminum instead of the triethylaluminum. 160 g of polyethylene were obtained. That mean molecular weight was 365,000, the molecular non-uniformity 63.2 and the density 0.966 g / ml.

Example 11

The procedure was as in Example 2 A and B, but 5 g of butene- (1) were added to the reaction mixture. There were 110 g of copolymer obtained with a molecular non-uniformity of 26 and a density of 0.960 g / ml. The bark test showed > 800 hours

- 13 209-884 / 1-131

Claims (1)

'I ^ polyethylene with a gel permeation chromatography "determined Inconsistency of U = 20 as well as a density j be « according to DIN 53 479, from 0.963 g / ml Ms 0.98 g / ml. Copolymers of ethylene and 0.1 to 5 Gevr.?o of copolymer Butene- (1) with a gel permeation chromatographic ÜneiiiV uniformity of U = 20 and a density, determined close DIN 53 479, of at least 0.958 g / ml * . ^ Process for the production of polyethylene and copolymers according to claims 1 and 2 by polymerization of ethylene,, optionally in the same amount as 0.1 to 5% by weight of 6 butene- (1) in Presence of molecular hydrogen using eitiei Catalyst of the 2iegler type made of chromium compounds and alti * organomine compounds, thereby, g e k e η ft «· distinguishes that a catalyst for the polymerization Chromyl chloride and trialkyl aluminum of the general formula FUAl, in which * E any alkyl radicals with 1 to 8 carbon * atoms mean, is used, which is in a saturated aliphatic or aromatic, liquid `` substance '' in the presence of dispersed * silica or (I S 8 3 4/1 1 3 ■ 1