DE1669808C3 - Polyolefin mixtures for the production of moldings with no melt fracture - Google Patents

Description

mixture of vulcanizing agents. 35 would take on ⁶ properties of the defect described. Others to melt fracture no

Low polyolefins are those using

Catalysts made from aluminum silicates containing chromium

received.
40 The reduced viscosity // red is calculated according to

The invention relates to polyolefin blends of the formula:

Manufacture of moldings free of melt fractures on the basis of- __ 1 J] L - »7q_

location of a low-pressure polyethylene or a low- '^ * " ¹ ~~ _c ' ^

llruckcopolymeren from ethylene on the one hand and Pro-.

pylene or butene-1, on the other hand, with a density of 45 ^where

C, 932 to 0.958 and a reduced specific Vis- _c = concentration (0.1 "/" solution),

viscosity from 2.0 to 3.0, measured in decalin at 135 ° C. ^ ₌ dynamic toughness Jer solution,

From such polyolefins, if they _ dynamic viscosity of the solvent

a narrow molecular weight distribution accordingly

have a non-uniformity of 1 to 3, does not mean 50. IhIvI _n M ,.

easily produce moldings free of melt fracture- For the measurement, an Ostwald or Ubbelohde-

In our Schmel? bruch we understand that the shape viscometer of certain dimensions (, Mj, body Structures in the form of a sometimes over mol Chemie 13 [1954] p. 71) related. Measured Spreading out the entire surface, numerous is in decalin at 1J5 C.

individual notches show existing corrugation. 55 The inconsistency is defined as the behavior As a result, the finished molded body experiences understanding -

Certainly an impairment. - - - 1,

One endeavors to remedy this deficiency through Va- Ai _n

riation of the processing conditions (change of the

Pressure build-up, the temperature program, the 60 being the weight average
Screw speed range etc.) as well as the ma- - _ Zd Mt

fast device itself (screw exchange, i » _m - ^

Tool change, etc.) if possible.

However, the complete elimination of the melt fracture is achieved in a good approximation by means of the ultracentrifuge, or in the rarest of cases. It is also obvious that the number average is obtained by 65 light scattering
an increased use of common lubricants such as Stea- _ "ZrtiMi

rate, ester salts of polyvalent carboxylic acids, paraffin ^ M _n = -

waxes or lower molecular weight polyethylene types ^ m

by means of osmotic measurements Ut - weight concentration with molecular weight Mt, nt ^r number of molecules with molecular weight Mt).

The polyethylene to be added to eliminate the melt fracture is an ethylene homopolymer with a density of 0.935 to 0.950, a reduced specific viscosity of 3.2 to 4.8 and a non-uniformity from 4 to 10. Its production is carried out using complex catalyst systems, such as for example titanium tetrachloride, and an inactivating organoaluminum compound based on a dialkyl monochloride of aluminum, such as B. Jet butyl aluminum monochloride according to Ziegler.

Non-polar rubbers are to be understood as meaning those whose molecular structure is free of heteroatoms, in contrast to polychloroprene rubber or butadiene-acrylonitrile elastomers or also chlorosulfonated poly ethylene.

Suitable apolar types which can be crosslinked with sulfur are obtained by various processes, for example by ionic polymerisation of isobutylene and isoprene at -90 to -100'C with the aid of aluminum chloride in methylene chloride, forming a butyl rubber, or by polymerizing Isoprene in cyclohexane on a butyl or phenyllithium contact, giving cis-1,4-polyisoprene; Furthermore, a using complex catalyst systems with vanadium chlorides and aluminum alkyls is suitable Ethylene-propylene rubber made in tetrachlorethylene at -20 to -100 C with 0.5 to 10 percent by weight diryclopentadiene (U.S. Patent 3,000,866), a cis 1,4-polybutadiene. that is obtained from a contact of aluminum trialkyls and titanium tetrabromides or iodides, or also a butadiene-styrene rubber, as z. B. by radical chain polymerization in emulsion below Use of redox systems such as cumene hydroperoxide and divalent iron ions will.

The mils that can be used for crosslinking are sulfur in the usual form of sulfur bloom together with zinc oxide and stearic acid and optionally also other accelerators well known from rubber chemistry such as. B. Mercaptobenzothiazole. Tetramethylthiuram disulfide or di-o-tolylguanidine.

These additives make the apolar rubbers firmly in the molecular structure of the polyethylene components built in or grafted on, so that an overall system results whose meltability ei remains.

The molding compositions can also contain the additives customary for thermoplastics, e.g. B. Antioxidants and stabilizers such as 4-, 4'-butylidenebis (6-t-butyl-m-cresol), Dilauryl thiodipropionate, dibcnzylrcsnrzin and 2- (2'-hydroxy-5-methyl-phenyl) -benzotriazole, lubricants such as zinc, sodium or calcium carate. Fatty acid esters and paraffin waxes, antistatic agents such as nonylphenyl-heptaethylene glycol, lauryldietanolamine or coconut fatty acid diethanolamide, pigments of an inorganic nature such as titanium white, cadmium yellow, iron oxide, Phthalocyanines and finally also fillers such as chalk, silicates, sulfates, asbestos, glass fibers and Russian.

The mixture expediently starts from the products obtained in powder form during manufacture, which are mixed together with the respective ingredients (rubber crumbs, vulcanizing agents, antioxidants, lubricants, pigments and fillers) at room temperature and then through an extruder with between 140 and 210 "C temperature settings can be processed into granules, or the compression takes place simultaneously with the mixing process by 3 to 10 minutes during agglomeration between 100 and 120 C in an appropriately heated mixer. The rubber is thereby - probably via sulfur bridges - in the polyethylene molecular association The use of partially or fully vulcanized rubbers does not give the same good results, quite apart from the fact that the distribution leaves a lot to be desired.

From British patent specification 933 194 it is known that one similar mixtures, but with which the proportion of the second component, its inconsistency is not defined, should not exceed 15 percent by weight, can be used to opaque polyethylene to make it more transparent. The published documents of the Belgian patent 647311 teach that similar mixtures, but whose second component has a density of at least 0.955 and should have a melt index of 1 to 20 (in contrast to the present invention, where this Melt index b, 0), an improved stress flow behavior show. Neither of the two writings indicated that certain changes could be made the measures lead to mixtures that are free of melt fracture.

Above all, however, the expert could not foresee that one freed with melt fracture afflicted polyolefins from this disadvantage that one they add particularly high molecular weight and correspondingly poorly flowing polyethylenes; all the more so more than the difficult flow conditions to be expected tend to increase the melt fracture considerably instead of not only reducing it, as was surprisingly found, but even abolishing it.

Example!

a) Polymer with melt fracture

The granules of an ethylene-butylene copolymer containing 0.2 parts of 4,4'-thiobis (6-t-butyl-3-methylphenol) with 4 percent by weight of butylene, a density of 0.932, one ;; _r p (i-wide of 2.3 and a non-uniformity of 2) is calculated on an extruder using a short compression screw customary for polyolefins (50 D, LD ratio 15, compression I: 1.7) under the following temperature program:

Cylinder (from feed hopper to

Nozzle towards) 140 ⁰ C, 170'X

190 ⁰ C

Tool 210 "C

200 C nozzle

from a 1 mm wide nozzle gap extended as a hose and into hollow bodies of 11 contents and Blow out a wall thickness of 0.5 mm. Even the extended hose shows a severe melt fracture, as well the resulting hollow bodies.

b) Mixture according to the invention

A mixture prepared at room temperature in a high-speed mixer of 70 percent by weight of the ethylene-butylene copolymer described under a) and 30 percent by weight of an ethylene homo-

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polymers with a density of 0.942. a reduced specific viscosity of 3.9 and a nonuniformity of 8 are after previous compression carried out via a granulator under the at a) described processing conditions extruded and blow them into hollow bodies. This results in products that are completely free of melt fractures. Self when replacing the short compression screw with one that is less common for polyolefin processing core progressive screw (50 D, LD ratio: 15, compression: 1: 1.7) are melt fracture-free Hollow body received.

c) Mixture according to the invention

A mixture of 74 percent by weight of the copolymer described under a) is produced at room temperature, 18 percent by weight of the homopolymer identified under b) and 7 percent by weight a butyl rubber containing 2.5 percent by weight isoprene the Mooncy viscosity 45 5 together with 0.2 percent by weight 4-, 4-thio'is- (6-t-butyl-m-cresol), 0.07 weight percent sulfur. 0.1 percent by weight di-o-tollylguanidine, 0.03 percent by weight Stearin. 0.4 percent by weight zinc oxide and 0.2 percent by weight N-phenyl-, N'-iso-propyl-p-phenylenediamine agglomerate the mixture in a 150-1 mixer at 115 ° C. for 5 minutes and process it as described above for hollow bodies. In this case, too, moldings that are completely free of melt fracture are obtained.

d) Counterexample

A mixture prepared at room temperature in a high-speed mixer of 70 percent by weight of the ethylene-butylene copolymer described under a) and 30 percent by weight of an ethylene-propylene mixture polymer containing 0.8 percent by weight propylene and having a density of 0.946, corresponding to an η ^ Λ value of 3.0 A molecular weight of about 130,000 and a non-uniformity of 7 are extruded and blown into hollow bodies under the processing conditions described under a) after previous compression carried out in a granulator. The hollow bodies show clear melt fracture.

If the ethylene-propylene copolymer is replaced by 30 percent by weight of an ethylene homopolymer with a density of 0.950, a reduced specific viscosity of 2.7 and a non-uniformity of 8, or an equal amount of a correspondingly broadly distributed ethylene-propylene film. If a polymer with 0.5 percent by weight propylene and an i / _re <i value of 3.5 is used, hollow bodies with melt fracture are likewise obtained.

e) Counterexample

If one of 82 percent by weight copolymer is processed under the conditions of example c) and 18 percent by weight homopolymer or a mixture consisting of 93 percent by weight copolymer and 7 weight percent butyl rubber composite mixture, the products show from it a recognizable smelting pipe.

Example 1 thus clearly shows the influence of the reduced specific viscosity of an ethylene homopolymer addition component on the melt fracture of a polyethylene for a given broad molecular weight distribution (non-uniformity). Furthermore, it has been shown that a mixture which, in addition to the homopolymer of high molecular weight and broad distribution, also reveals a sulfur-vulcanizable rubber , allows the starting material with melt fracture to participate more in the overall mixture than would be possible if only the homopolymers * added according to the invention were used.
That the basic behavior of such mi-

iQ improvements through the simultaneous use of fillers is not influenced in any way, the following examples show inactive soot fillings, one also recognizes the superiority of the mixtures according to the invention, in particular the rubber-containing.

Example 2

a) Counterexample
A granulate of 80 percent by weight of the marked in Example la). η and as there stabilized polyethylene and 20 percent by weight of an acetylene black with an average particle size of 43 μm is initially at a screw speed on an extruder equipped with a pipe die and a short compression screw (60 D, LD ratio: 20, compression ratio: 1: 3, 3 zones) of 12 UpVI with the following temperature program (from the funnel to the nozzle, including nozzle 7 heating points): 135, 170, 240, 250, 250, 250.

260 C processed into pipes with a diameter of 32 mm. Even with this optimal temperature control, no melt fracture-free tube can be created and the screw speed is increased further only increased melt fracture, so that from around 25 rpm pipe production becomes pointless.

The pipes do not meet the strength requirements in any way, as they are subjected to the resistance test. Unless they burst immediately after the print job, the service life values are scattered at random provide.

b) Mixture according to the invention

On the other hand, a mixture which contains 80 parts of the mixture from Example 1 b) and 20 parts of acetylene black, after previous compaction, gives a granulator under the same processing conditions completely melt fracture-free tubes with a surface resistance of 10 ⁵ Ω. The speed can now also be increased up to the maximum, which in the present case is 50 rpm, without melt fracture occurring. There are considerable technical advantages associated with eliminating the melt fracture.

For test stresses of σ - 30 kp / cm ² and π - = 41 kp / cm ² are required at 80 "C in accordance with DIN 8075 paragraph 2, requirement A, minimum standing times of 170 or 48 hours; the pipes made from the mixture according to the invention show the following well-matched values:

a 30 at 8O ⁰ C: 953 870 960 960 960 hours CT41bet80 ° C: 177 225 201 249 169 hours

Example 3
a) Counterexample

The granules from Example 2a are processed on the machine from Example 1a, only at around 4 ° C higher cylinder temperatures, otherwise

1 689 808

but the same processing conditions as the already Hollow bodies characterized there.

The hollow bodies show severe melt fracture.

b) Mixtures according to the invention

The granules of Example 2 b) are processed under the conditions of Example 3a). Hollow bodies are obtained with surfaces that are completely smooth on the inside and outside, free of enamel bulges, and surface resistances of 10 · Ll.

c) Mixture of the invention

A mixture is made from 20 parts by weight of acetylene! uß and 80 parts of the mixture from Example 1 c), only replacing the butyl rubber with an unsaturated ethylene propylene rubber with 2.5 percent by weight dicyclopentadiene and a Mooney viscosity of 50, the mixture is granulated and processed as in Example 3a). The hollow body is obtained with completely smooth, melt fracture-free surfaces both inside and outside and surface resistances of 10 " LI.

For the purpose of further investigation, the hollow bodies obtained from the above tests are filled with a mixture of water and glycol in a ratio of 1: 1 to 90 percent by volume and immediately subjects it to a drop test after storage for 24 hours at -35 ° C. The heights of fall that are without break can be achieved, the samples of Example I are compared below:

Samples from example height of fall

1 a) 0.5 m

I b) 1.0 m

I c) 1.5 m

1 d) 0.5 m

3 a) 0.5 m

3 b) I, 0 m

3 c) 1.5 m

ίο It's surprising that just a polyethylene that In comparison to the polymer with the enamel cervix, it flows more difficultly, which solves the problem.

It is also surprising that rubber alone, with or without vulcanization agents and even with Do tations that far exceed the said upper limit go out, the melt fracture is not eliminated. It was also not obvious to work as claimed, there too a peroxide addition which is on the order of about 0.005 to 0.01 weight percent decrease

ao of the I ₅ value, the melt fracture is not eliminated. It does not matter whether bisperoxides are used for this purpose, for example in accordance with US Pat. Falling speed controlled simple monoperoxides used. Also otherwise more advantageous when in use

Fabric cottons result in such a case

only processing difficulties.

Also additions of pigments or fillers

have no effect on the melt fracture.

Claims (2)

I 669 608 ι ² as well as through various combinations of these substances. bruch! ™ "mold core doing ms: 5" eKf Ähung "nz ^ ben:" eiche den sdmer- a) a low-pressure _{polyethylene or a w} j _e lowing disadvantage of the polyolefins mentioned safely low-pressure copolymers from ethylene one eliminated on the one hand and propylene or butene-I on the other hand This object is achieved according to the invention by having a density of 0.932 to 0.958 and a _{χρ ejncn content of the} mixture of 20 to 50 weight- _{reduced specific viscosity of 2.0 cents} . _nes low-pressure polyethylene with a density of up to 3.0 and ₀ 935 ^ ₅ o, 95O, a reduced specific viscosity b) 20 to 50 percent by weight of a low-pressure _t ~ _{t of} 3.2 to 4.8 and a non-uniformity in polyethylene with a density of 0.935 to 0.950, _between 4 _and 10. a reduced specific viscosity of _{In a} further embodiment of the invention 3.2 to 4.8 and a non-uniformity between ^^ the problem is solved by a content of the mixes 4 and 10 of 10 to 30 percent by weight of a low . , riruckDolväthylens a density of 0.935 to 0.950, 2. Polyolefin molding compounds for the production of melt- «™ reduced specific viscosity of 3.2 to 4.8 break-free moldings consisting of: ^ ^ _ejner unevenness between 4 and 10 and a) a low-pressure polyethylene or ^a ° _{by e ne} j content with 10 to 4 weight percent of a Niederdruckcopolymeren of ethylene on the one _apo stellar sulfur cross rubber at the same part, and propylene or butene-1 on the other hand zeitigem addition of 0.1 to 1.0 weight percent, bemit a density from 0.932 to 0.958 and a _{coated o} f the total mixture, specific viscosity of 2.0 to Vulkanisationsreduzierten means. to 3.0, which are polyolefins that tend to melt fracture b) 10 to 30 percent by weight of a low-pressure polyethylene and its copolymers with up to 8 polyethylene with a density of 0.935 to 0.950, percent by weight propylene or 1-butene, as obtained with a reduced specific viscosity from special processes, for example according to 3, 2 to 4.8 and a _{non-uniformity} between 3O the low-pressure process using see 4 and 10 as well as mixed catalysts made of halo-titanium acid esters e.ner- c) 10 to 4 percent by weight of a non-polar side and aluminum trialkylene or - «« JJ «^ · ^ ·