DE2018423C3 - Process for crosslinking polyolefins and olefin copolymers - Google Patents

Description

R.

R,

C = CH - CH - C

R ₁

R-

ι2ι

R,

CH CH

R ,.

where R; an aryl and R ₂ . R _v Rj. Em aryl-i-can be the hydrogen residue, \ can be used.

4. The method according to claim 1 and 2, characterized in that the luheiie as the polymethine general formula

wherein R ₁ . R ₂ . R ₁ . R _-1 - = hydrogen and R ₅ . ! <“Can be hydrogen and / or aryl or .. if R ₅ = hydrogen. R "also a Heterocyeiüs without heteroatom-bound. active hydrogen can be used

5. The method according to claim I and 2. thereby characterized in that the polymethine compounds are 4; according to the general formula

crosslinking in the presence of 0.1 to 20 parts, carried out based on the weight of the polymer of at least one polymethine.

Due to their structure and chemical reactivity, the polymethines react with the methyl radicals formed during the crosslinking process to form a radical intermediate that acts as a crosslinking agent in place of the trapped methyl radicals works. By using at least one polymethine according to the invention, which act as a methyl radical transferring agent, the crosslinking process can thus can be controlled that prevents methane gas formation in a wide processing latitude, practical however, the same level of crosslinking as is achieved without the addition of these radical transfer agents.

In particular, the use according to the invention of at least one polymethine greatly suppresses the formation of methane in crosslinkable forex bodies which contain a crosslinking agent which forms methyl radicals. This prevents the formation of methane gas bubbles, which can only escape with difficulty as the degree of crosslinking of the polymer increases and thus prevent irreversible pitting in the polymer (clocks) over a wide range of processing options. Technically valuable products with improved mechanical and electrical properties are obtained.

Suitable methyl radical transfer agents, ind polymethines of the alicine formula

R,

C-CH CH-C

R.

where R, an aryl and R ₁ . R ₁ . R _{4 can be} an aryl or Wasscritoffresi. Connections .iUo such. B. I-phenyl-1,3-butadiene r> derl.4-diphenyl -]. 3-buladiene Also polymethines of the general formulas

R,

R;

R,

R,

-ΓΗ-ΓΗ-C

R «

R.,

wherein R ₁ . R ₂ , Rj, R ₄ = hydrogen and R ₅ . R _{6 can be} hydrogen and / or aryl, or if R ₅ = hydrogen, R _{(> can} also be a Heierocycle without heteroatom-bonded active hydrogen can be used.

The invention relates to a process for crosslinking polyolefins and Oiefin copolymers in the presence of tertiary peroxides. According to the invention, we have proven to be particularly favorable.

In formulas 2 and 3, R ,. R ₂ , R ₁ . R ₄ = hydrogen and or aryl or R ₁ ZR ₂ = arylene and or Rj R ₄ = arylene. R ₅ , R ₆ can be hydrogen or

fto be aryl or, if R 1 = hydrogen, R _{6 can} also be a heterocycle without active hydrogen bonded to hetero atoms.

Suitable compounds of the general formula 2, which are bez.cichnet as Filvenc, are, for. B. Phenyl fulvcn. Diphenylfulvene. in-phenyl or. (.i.ni'-Diphenylbzofulven, 9-Phenyl- or 9-Diphenylmelhylenfluorene and furfurylindene-cyclopentadiene (u-Furanylfiilven).

Suitable compounds of the general formula 3 are, for. B. Citraaraylidenfluoren, Cirmamylidenfulven or cinnamylidene indene.

A particular advantage of those to be used according to the invention Compounds of the general formulas 2 and 3 can be seen in the fact that they are extremely easily accessible are. They fall in the condensation of cyclopentadiene or cyclopentadiene derivatives with the corresponding Aldehydes or ketones in a basic medium partly quantitatively and in one purity. which enables their direct use according to the invention

In the production of the fulvenes, any proportions of oligomer products that may arise interfere the intended effect according to the invention of these substances is not.

The use of the polymethines according to the invention together with AU has proven particularly advantageous at least 2% acenaphthylene based on the weight of the olefin polymers. Through a Such an addition to the crosslinkable polyolefin becomes a vulcanizate with excellent oxidation stability receive.

The mode of action of the eiröndungsgeraäß used Polymethine is illustrated by Table I.

It was the percentage decrease in the methane gas volume in milliliters per MUlimol dicumyiperoxide at 160 or 180 ° C. with and without the addition of the polymethines used according to the invention in the hydrocarbon Undecane (under nitrogen atmosphere) determined.

Table

rnNM i-Nl.u Hit'.mn l- ndoc.i-i peroufi 44.S ^: 1.41 44.8 1.41 44.S 1.41 44.S 1.41 44. " i.41 4-1.8 1.4 44. " i.4 44.8 1.4 44. " 1.4 44.S 1.4 4-1. } < 1.4

! Phen ;. ! butadiene 160

1.4-diphen \! H; iU: d! En IbO

! -Phen \ lhutadie; i
1,4-diphen>! Butadiene
Diphenyl FuKen 160

C'innamyiidenlluoren 160

'■ ..! • i'-Diphemlben / ofuhe 160

-Furanyl lines 160

Diphenvlfühlen
Pheinlfulven

1X0
ISO

IN THE)
ISO

!so

Percentage

Mirih.ine.:^·
.ihn.iiimc

S5

60
S2
50

Sl

i>; e rr. ι the W-met / ung of polyolefins with Vlitertiüren fV-Roxidcn. which form ^ k · lhylΓ; ^ dikule above their decomposition temperature. Although we kung the Mcthylradikal-nbtTträgcrstolTc in crosslinking polyethylene Dicumyiperoxid. since methane is formed almost exclusively as a gaseous component, it is the most transparent and most pronounced. The advantageous first effect is shown when the polymethines according to the invention are used, even with peroxides which, in addition to methane, also form other substances that are volatile at low temperatures, i.e. peroxides such as τ. \ Ί. Diated.-butyl peroxide 2.5-bis-tert.-butylperoxy-rf-dimethylhoxane. 1.3-bisttert.-buty! Peroxy i-isopropylbenzene. η -Butyl-4.4-bis-Itert-butylperoxyl-valerut. 2.2- Bi> - (tert -bulvlperoxyl-butane.

Table 2 shows the percentage assumption of the total gas volume in milliliters per millimo! i.3-His- (tert-butylp; roxy) -isop: ropylhenzene at 16 () or \ v. 180 C "with and without the addition of substances. in IJrdecan (nitrogen atmosphere):

table

rr.Moi mV.'i 5.2.Ϊ mmo! 160 j emper.itur 1X0 F'ro / entMJn. nik-c.m l'ernxui 5.2 R.nlikaiUlicrrr.iiici I 160 I.
I. "j ISO i ''] 44.S 1.12 5.2 i-phenylbutadiene 160 I.
i 1X0 ι iS 44.8 1.12 5.25 Diphcnylftilven Sl 44.8 1.12 ~ »- Cinnamyl fluorene 75 44.8 1.12 5.2 1-phenylbutadiene 63 44.8 1.12 Diphcnylfulven 78 44.8 1.12 Cinnamylidene fluorine 72

The most favorable amount of the peroxide to be incorporated in the process according to the invention depends on the effectiveness of the peroxide and on the desired degree of crosslinking of the polymer. Up to 20, preferably 0.5 to 10 percent by weight of the peroxide, based on the weight of the polyethylene, are used. For carrying out the process according to the invention, the polymethines are preferably used in

Amounts from 0.5 to 20, in particular 2 to 10 percent by weight, based on the polymer.

about the effectiveness of z. B. Diphenylfulvene as Polymethine depending on the amount of one crosslinkable polyethylene peroxide mixture added Diphenylfulvens is given in Table 3 and Table 4.

The percentage decrease in the gas volume was determined in milliliters per milliraole of peroxide at 160 ° C decomposition temperature and more variable if added Amounts of dipnenylfulvene (nitrogen atmosphere) in Undecam (Tab. 3 and 4).

Table 3

raMol Undecane

44.8
44, «
44.8
44.8

mmol U η doan

44.8
44.8
44.8
44.8

mmol dicumyl peroxide
(95%)

1.41
1.41
1.41
1.41

mmol Diphenylfulvene

1.41
2.99
5.21
7.49

Table 4

mmol

l.3-bis- <len-

butylperonN I-

isoprop \ l-

hen / ol

1.12
1.12
1.12
1.12

mmol

Diphen> l-

feel

1.12
2.99
5.21
7.49

Percentage Gas takeoff

in % at 160 C

34
67

92

Percentage

Gas takeoff

in "o at

IW) C

18th

47
78
87

In summary, it should be noted that the advantage of the polymethines to be used according to the invention is that they prevent the formation of methane in crosslinkable Strongly push back moldings which contain a crosslinking agent which forms methyl radicals. This causes the formation of methane gas bubbles, which occur during the "pressureless" vulcanization In suitable high-boiling liquids z. B. Salt Melting particularly noticeable as a heat exchanger without using the method according to the invention and leads to the irreversible formation of voids in the vulcanizate, with a wide scope for processing prevented. Technically more valuable, defect-free products with improved mechanical and electrical strength properties are obtained.

Both the usual high (density 0.91 to 0.94) and low-pressure polyethylenes are suitable for the new process (Density 0.95 to 0.98).

For mixing the polyethylene with the invention Radical transfer agents used and the crosslinking agent can use the usual mixing methods to be used. The radical carriers described can, together with other additives such as B. anti-aging agents directly at temperatures, which are below the light-off temperature of the peroxide, added to the molten polymer or mixed with the solid polymer, then the mixture above the softening point of the polymer to warm up. To ensure that the additives are evenly distributed below the softening point of polyethylene to achieve, the radical carrier and'or the crosslinking agent can also m one Room temperature liquid additive which, due to its chemical structure, does not cause any inhibition crosslinking effective radicals leads, added or sprayed on. To control the networking became a kneader mixer with a measuring device for determining the amount of work with a recording device used to measure the torque change in a torque range from 0 to 1 mkp. As a relative measure of the degree of wounding, the measured change in torque from the time of the Add the peroxide to the molten polymeric material until the maximum is reached Torque can be used. The greater the change in torque, the more the material is cross-linked. Information about the rate of crosslinking is provided by the addition of peroxide until it is reached the time elapsed from the maximum torque.

Example '.

In the heated to 150 "C kneader chamber des Mixing kneader with a measuring device to determine the amount of work required were 40 g of commercially available High-chuck polyethylene (density 0.92) registered according to Plasticizing for 5 minutes with 1.6 g of the methyl radical transfer substance and after a further 2 minutes 64 g of dicumyl peroxide (95%) are added. Table 5 gives the values of the change in torque at the maximum torque (Crosslinking strength VS) and that of the addition of peroxide until this is achieved Maximum elapsed time as networking time VZ.

Table 5

VSImkp) VZlminl

1.0

0.9

1.55

0 ^ 5

1.0

1.05

10

10
7.5
9.0 9.5
8.0

Methyl radical carrier

Control material (without addition) ..
Diphenylfulvene

(D.ix'-Diphenylbenzofulven

a-furanylfulvene

Cinnamylidene fluorene

■ ^ 1,4-diphenylbutadiene

Example 2

In a laboratory kneader were at a kneading temperature of 120 ⁰ C, mixtures of high-pressure polyethylene (density 0.92), 1.6 weight percent Peroxiö made with and without the addition of 4 percent by weight of radical transfer agent substance.

The homogeneous mixtures were on a press S5 at 180 ° C / 4min. or! 8O ⁰ QiO min. (pressing temperature / pressing time) pressed into panels about 1 mm thick. The degree of wetting achieved on these plates was determined using the following method:

Samples (~ Ö, 2g) of the press plates were extracted in 50 ecm xylene (stabilized with 0.1% / I-naphthylamine) at 135 ° C for 3 hours. After drying (in vacuo at 110 ^° C.), the dry weight of the extracted sample was determined. The quotient

Dry weight of the extract. sample

100

gra pre

V d <P P ei te

target

Starting weight of the sample
results in the so-called percentage networking V.

Table 6 gives the relative degrees of crosslinking obtained as the percentage crosslinking V of the crosslinked Press plates again:

Table 6

1 mm press plates of the mixture composition

Print certificate Press? Egg (

ISO 4 min.

ISO IO min.

Polyethylene / 1,3-bis (lert.-butyI-

peroxy-isopropyl) benzene 88 "4 90%

Polyethylene / 1,3-bis- (tert-buty 1-

peroxy-isopropyl) benzene /

Diphenylfulvene 87% 88%

Polyäthyien / l, 3-bis-tert-butyi-

peroxy-isopropyl) benzene /

1,4-diphenylbutadiene 87% 89%

Polyethylene / dicumyl peroxide

(95%) 87% 91%

Polyethylene / dicumyl peroxide

(95%) w, (/) '- Diphenylbenzo-

fulven 83% 83%

Example 3

In the heated to 150 ° C kneader chamber des Mixing kneader with measuring device to determine the amount of work was commercially available ethylene-propylene rubber entered, after 5 minutes plasticizing time with 4% (based on the polymer) a methyl radical transfer substance and after a further 2 minutes with 1% dicumyl peroxide (95%) offset. Table 7 gives the values of the change in torque at the maximum torque (crosslinking strength VS in millikilopond) and those of the addition of peroxide The time elapsed until this maximum is reached as the crosslinking time VZ in minutes.

Table 7

Methyl radical transfer agent additive VS Imkp) VZ (min) Control material (without addition) ..
+ Diphenylfulvene
+ «Vo'-Diphenylbenzofulven - · · ■
+ Cinnamylidene fluorene 2.05
3.4
3.75
3.6 2.0
2.0
1.0
1.4

Mclhvlriulikiilühcrlrai'cr / iisiil /

+ (i-furanylfulvene ..
+ Diphenylbutadiene

VSlmkpl

3.2

3.4

V / (min) 1.8

1.3

Et c i s ρ i e I 4

From the mixtures of 98 parts (parts by weight) of high pressure polyethylene (density 0.92) and 2 parts of dicumyl peroxide (95%) = mixture I or 94 parts of high pressure polyethylene (density 0.92), 4 parts of diphenylfulvene and 2 parts of dicumyl peroxide (95%) ) = Mixture II was ^{injected at an extrusion temperature of 130 0} C core insulation with 5 mm insulation wall thickness. Test specimens of this core insulation 15 cm in length were placed in a eutectic salt core, consisting of KNO ₃ (53%), NaNO ₂ (40%) and NaNO ₃ (7%), e.g. Example at temperatures of 170 to 18O ⁰ C salt bath temperature up to the onset of visible gas bubbles crosslinked. The values of the percentage crosslinking V associated with the corresponding crosslinking times (cf. Tab. 8) were determined as described in Example 2.

A comparison of the values obtained shows that those with an additive according to the invention Veisehene mixture II the production of technically sufficiently crosslinked, defect-free core insulation allowed.

Mixture I.

Mixture II

table 8th Salt bath Networking temperature 3EIT _. ££>. _ (Min.) 170 : t, 8 175 2.9 180 ;>, o 170 7.5 175 i), 4 180 3.9

Proc. Networking

(V)

66 48 33

80 77 79

According to the method according to the invention, extruded or injection-molded articles or else Cable insulation is made that have no voids and bubbles and excellent electrical and have mechanical properties.

«9634/292

Claims (3)

Patent claims: 1. Process for crosslinking polyolefins and olefin copolymers in the presence of ditentary peroxides, characterized in that that the crosslinking in the presence of 0.1 to 20 parts by weight of the polymer is carried out by at least one polymethine. 2. The method according to claim 1, characterized in that polymethines together with at least 2 percent by weight acenaphthylene, based on the olefin polymer, can be used. 3. The method according to claim 1 and - · thereby characterized that qb polymethine compounds the general formula