DE1176849B - Process for the production of vulcanized moldings - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 08 f

German class : 39 b- 22/06

Number: 1176 849

File number: M 46627 IVc / 39 b

Filing date: September 22, 1960

Opening day: August 27, 1964

During the various processing stages of rubber-like substances such as mixing, pressing, calendering and shaping, it can be advantageous for various reasons to work at the highest possible temperatures, which depend on the degradability of the elastomer. However, if the mixtures already contain vulcanizing agents, temperatures of 100 to 120 ^° C. cannot be exceeded in order to avoid so-called burning. This is obviously a severe limitation for various processes, for example for extrusion processes, in which large amounts of fillers, which greatly promote extrusion, have to be added in order to be able to carry out the process at these temperatures.

The invention relates to a process for the production of vulcanized molded articles from rubber-like polymers using per-compounds and optionally sulfur, which is characterized in that ethylene-propylene or ethylene-butene copolymers or mixtures of polyethylene or polypropylene with at least 5 percent by weight, based on the mixture of an ethylene-propylene or ethylene-butene copolymer, optionally in a mixture with fillers and / or sulfur, ^{shaped at temperatures of 160 to 300 0} C, the objects obtained cool, with an organic per compound, dissolved in a solvent which does not dissolve the polymer, impregnated, dried, and finally cured under pressure at 100 to 22O ⁰ C.

During deformation of mixtures of rubbery polymers and peroxides at relatively high temperatures, for example about 140 ⁰ C, then a more or less strong burning, already been pointed out above. This process represents premature vulcanization, which occurs when the molded body has not yet assumed the desired final shape. With such a partial pre-crosslinking, irregularly shaped objects with an uneven appearance or corrugated surfaces or z. B. in the case of cables with sprayed-on insulation, air pockets in this insulation. According to the invention, all these disadvantages are avoided by the subsequent introduction of a peroxide compound into the already formed objects and the possibility is created to carry out the deformation at much higher temperatures at which the polymer is highly liquid and easily fills the mold and, in particular, also eliminates air inclusions . It was not anticipated that a peroxide addition to the finished article would process vulcanized
Moldings

Applicant:

Montecatini Societä Generale per l'Industria
Mineraria e Chimica, Milan (Italy)

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald
and Dr.-Ing. Th. Meyer, patent attorneys,
Cologne 1, Deichmannhaus

Named as inventor:

Giovanni Pedretti,

Luigi Corbelli, Milan (Italy)

without using special dragging or carrying means from the outer surface of the objects would migrate inside, so that a uniform vulcanization of the entire object is possible.

According to the invention, for. B. manufactured an object in its final form, then cooled and immersed in a vessel containing a suitable organic peroxide in acetone or alcohol (about 20 to 100 g peroxide in 1 1 solvent). The immersion time varies from about 1 hour to a few days, depending on the maximum thickness of the object and the bath temperature (30 to 50 ^° C.); during this time the peroxide, ie the vulcanizing agent, penetrates the entire object by diffusion. In the state of equilibrium, there is a certain relationship between the concentration of the peroxide diffused into the rubber-like polymer and the peroxide in the solvent. The object is then removed from the bath and kept for a few hours in a drying cabinet in a vacuum at approximately 40 to 50 ^° C. in order to evaporate the small amount of the absorbed solvent; then it is placed in an autoclave and then pressurized to vulcanization at a temperature which, depending on the nature of the peroxide used is generally between 100 and 22O ⁰ C, to carry out.

The copolymers used have z. B. a molecular weight of 50,000 to 500,000, preferably from 80000 to 180000, and include, for example

409 658/485

40 to 65 mole percent propylene or butene. The following are the advantages of the invention Procedure related to the manufacture of special items, such as electrical cables, Tubing and yarn, shown.

Cables for conducting electrical current have an insulating jacket, which is made of elastic or can consist of plastic materials; the first type includes vulcanized rubbers such as natural rubber, Butadiene-styrene copolymers, butyl rubber, silicone rubber and rubber-like Ethylene-propylene copolymers; the second group includes plastics such as polyethylene, polypropylene and Polyvinyl chloride.

The difficulties which arise when pressing pure types of rubber and which are exacerbated by the fact that, as already stated, the temperatures of 100 to 120 ^° C. must not be exceeded, led to the use of mixtures with a high content of fillers ( generally kaolin or calcium carbonate).

However, these fillers noticeably deteriorate the electrical properties of the original elastomers; there is a decrease in the volume resistance and an increase in the dielectric constant and the dielectric loss, a higher water absorption and a higher possibility of occurrence of sources of error due to uneven distribution of the fillers.

The use of the plastic polymers does not give rise to any particular extrusion problems; this process can easily be carried out even without the use of fillers, provided that it is carried out at sufficiently high temperatures; On the other hand, however, the thermoplasticity of these substances is a serious disadvantage, since in the event of short circuits of a certain duration, whereby temperatures of over 150 ^° C. can be reached in the conductor, the entire cable is caused by melting or strong softening of the insulation layer and the resulting displacement of the same Conductor can be damaged or destroyed; in addition, large cables are usually operated at operating temperatures of 70 to 90 ° C, with these polymers beginning to soften.

In the case of polyethylene, for example, attempts have been made to overcome this disadvantage by crosslinking the insulation layer through the action of β or γ rays; however, very expensive equipment must be used here.

By using the method according to the invention, there is now the possibility of the insulation layer of electrical cables made from pure elastomers without the addition of fillers by pressing them out at higher temperatures than were previously possible in the presence of vulcanizing agents.

example 1

There were smaller cables with the following properties:

Because of its consistency and its permeability to gases, mere resulted in compressed bodies, which are especially were smooth, compact and free of bubble holes.

Immediately after pressing, the cables were immersed ^{in water at 20 ° C. to cool;} After drying with a stream of air, they were wound onto bobbins and then immersed in an acetone bath at 40 ° C. in which 50 g of tetrachloro-tert-butyl peroxide per liter of acetone were dissolved. The immersion time was 20 hours; the cables are then finally cured for about 2 hours in a drying cabinet at 40 ° C under vacuum and 60 minutes in an autoclave at 15O ⁰ C.

At the end of the vulcanization, the dielectric strength and the electrical strength of the insulation layer were tested according to ASTM D 460/58 T, where the following results were obtained:

Highest permissible voltage (volts) 69,000

Highest permissible electric field

(Volts / mm) 24,000

Electrical strength (ΜΩ / kg) 35,000

Electrical resistance (Ll ■ cm) 2 · 10 ^le

The insulating layer separated from the conductor was subjected to mechanical tests in accordance with ASTM D 412/5 1 T subjected to the following results:

Tensile strength (kg / cm ² ) 32

Elongation at break (° / ₀ ) 600

Module at 300% elongation (kg / cm ² ) 11

In order to further improve the tensile strength of the ethylene-propylene copolymer, starting mixtures with polyethylene or polypropylene were produced. For example, insulation jackets with a tensile strength of 70 to 75 kg / cm ² were produced from mixtures containing 30 parts of polyethylene.

In accordance with the aforementioned process, small cables were also made from an ethylene-butene copolymer made with good results.

Example 2

55

Length about 50 m

Conductor cross-section 16 mm ²

Thickness of the insulation jacket 5 mm

manufactured for experimental purposes.

An ethylene-propylene mixed polymer was used for this. The extrusion temperature was about 200 ° C. The ethylene-propylene mixed polymer was a mixture of 80 parts of ethylene-butene mixed polymer (Molar ratio of the monomers 60:40) with 20 parts of polyethylene (grade 10).

With this mixture, a cable with a length of 200 m was produced by pressing at a temperature of approximately 190 ^° C., the conductor having a diameter of 4 mm and the insulation jacket having a thickness of 2 mm.

Immediately after extrusion, the cable was immersed in water for cooling of 2O ⁰ C, then dried in a stream of air, wound on a bobbin and immersed in an acetone bath at 40 ° C containing 50 g of chlorinated di-tert-butyl peroxide per liter acetone contained.

The immersion time was 12 hours; the cable

was then dried in a drying cabinet at 40 ° C under vacuum for about 1 hour and finally vulcanized in an autoclave for 40 minutes at 150 ° C.

After vulcanization, the electric

Properties of the insulation jacket measured, where

5 6

The following results were obtained (ASTM D where very good results were obtained. Similar

470/58 T: Results were also obtained using

Ethylene-butene copolymers obtained. Highest permissible voltage (volts) 32,000

Maximum permissible electric field 5 _RA : "":. ι c

(Volts / mm) 23000 Example 3

Electrical strength (ΜΩ / km) 16 000 Production of yarn with high elastic

Electrical resistance (Ω · cm) 1.5 ■ ΙΟ " ¹⁶ elongation and excellent rebound resilience

and very good aging resistance has been known

The insulation jacket, which is separated from the conductor, has so far been carried out in such a way that (with the help of suitable

mechanically tested, and the following result machines) thin vulcanized rubber sheets in

nits obtained: tapes were cut, the width of which is the thickness

of the bow, or that this by spinning

ASTM D 412/51 T 64 _oc j _e r failures in suitable baths of threads

Elongation at break (%) 650 15 concentrated vulcanizable latexes obtained

Modulus at 300% (kg / cm ² ) 23 were.

Made by this usual process from natural

Cables of the type described above have also been made of yarns obtained from or synthetic polymers

Mixtures of ethylene-butene copolymer with can due to the large surface area of the counter-

Made from 10 to 20% polypropylene. 20 status and the poor aging resistance of the

Product under special conditions

Example 3 must be applied and always with a cover

are protected from more resistant yarns,

Made of a mixture with a content of 100 parts, which is wrapped around this, so as to increase the elongation

len polyethylene and 30 parts of mixed polymer 25 are not limited.

from 48% ethylene and 52% propylene (molecular weight by using the weight according to the invention 120,000) were electrical cables, hoses, it is now possible to use elastic yarns various size, container of various type and excellent properties of mechanical, ther objects for medical purposes by mixing, chemical and electrical resistance shaping with the most suitable for this mixture of saturated, amorphous copolymers suitable temperatures. The vulcanization of ethylene and propylene or ethylene and butene was obtained directly after the finished items.

by the method described in Example 1. The yarns are simply pressed out

guided. The articles thus vulcanized were obtained and then impregnated with the peroxide and

Finally vulcanized for 10 hours in a drying cabinet at 150 ° C.

brought; they all retained their shape and consistency. The main advantages resulting from the application

and obtained elastic properties similar to those obtained by the method according to the invention,

of rubber. are the following:

With a mixture containing 100 parts of polypropylene and 40 parts of ethylene-propylene mixed polymer 40 a) The merizate used as the basis of the mixtures, various objects were produced on a mixed polymer have very good mechanical similarity; these objects were properties, especially very high tensile strength - held for 4 hours at 200 ⁰ C, and there were similar speeds; They also have extraordinary results, as with the polyethylene blends - resistance to light, heat, hold. 45 acids, bases, oxidizing agents and ozone;

In the vulcanization of manufactured goods, which also have good electrical properties,

Essentially made of polyethylene or polypropylene As a result of these properties, these yarns

are used under the most difficult conditions depending on the desired application

degree of wetting 5 to 50, preferably 20 to 40 parts, without them of any protection

Mixed polymer per 100 parts of polyethylene and 10 to 50 are required.

60 parts, preferably 30 to 50 parts of mixed polymer b) The spinning is carried out without the use of

used per 100 parts of polypropylene. Solvents carried out, d. H. without the

Need for recovery equipment

Example 4 doors and inevitable losses. It is therefore

55 a particularly economical process.

According to one of the principles described in Example 1. ^. ". . ,,,,. . ,, ".

similar procedure using ^c ) ^The spinning mixes do not contain any volcanic

Pure ethylene-propylene copolymers were sationsmittel and are against heating up to

^sth by pressing at a temperature of 200 ⁰ C ³⁰⁰ A, ^α even during long periods

Hoses and pressed objects of different 60 ^steel } which worked at the temperatures

Shape and size made. ^ ^ground ' ^where the viscosity for the

The same items were also ^S P ^{mnen best} g ^eei § ^{lst net} ·

Mixtures of ethylene-propylene copolymers d) The addition of vulcanizing agents by means of dif-

th with different amounts of carbon black or silica fusion after spinning makes it possible with

and sulfur made; with these mixtures 65 peroxides of the most varied kinds were to be worked,

the extrusion temperature 160 to 170 ⁰ C. without being hindered by the fact

Impregnation and vulcanization became different vulcanizing agents during

carried out according to the method according to the invention, the spinning cause a pre-vulcanization.

The process steps of spinning and vulcanizing are described schematically as follows:

The copolymers or its mixture with fillers, with or without sulfur, but without peroxide, in a metal vessel, which is kept under nitrogen, heated to 200 to 28O ⁰ C. (This vessel can also be an extruder, suitably heated and kept under nitrogen.)

The polymer heated in this way becomes liquid and can be fed directly to the pump that controls the spinneret feeds. The spinneret is attached directly above the cooling water vessel, and the spinneret Leaving threads are cooled quickly, reducing the surface oxidation of the hot threads, so far this is possible, is prevented. (A nitrogen chamber can also be used for this purpose.) The cooled and solidified threads are dried and passed through a bath containing the peroxide solution contains, where under conditions corresponding to those described in the previous examples, impregnated to the desired peroxide content.

The threads containing the peroxide can be collected in a centrifuge and the resulting ones Thread cakes can be steam vulcanized in an autoclave; but this treatment can also be carried out continuously by passing the peroxide-containing threads through a bath of an alloy, which melts at about 150 ° C, or by means of some other continuous thermal treatment vulcanized.

The spinning mix had the following composition:

35

Ethylene-propylene copolymer (molecular weight 100,000 to 120,000) 100 parts

Post-abrasion-resistant furnace black 50 parts

Sulfur 0.5 part

Total number 194 denier of eighteen threads 0.16 190 denier 420/450 Tensile strength, g / denier ... 0.18 Elongation at break, ° / o 420/470 Continuous stretching after 1 hour 200% 7th stretching and 1 minute Recovery time 8th

Example 6 The spin mix consisted of:

Ethylene-propylene copolymer 100 parts

Polypropylene 20 parts

Sulfur 0.5 part

This mixture was spun under the same conditions as just described, the nitrogen pressure being regulated in each case according to the desired extrusion rate.

The yarn collected from a bobbin was immersed for 1 hour in an acetone bath containing 20 g of tetrachloride tert-butyl peroxide per liter of acetone and, after vulcanization in an autoclave under 5 atm at about 153 ^° C. for 30 minutes, had the following properties:

Total number

of eighteen threads

185 i 205

Tensile Strength, g / denier ... 0.09

Elongation at break,% 220/320

Permanent denung, ° / o ··· I 15 to 17

0.07 170/290 16 to 20

The mixture was placed in a kettle and pressurized with the aid of a piston. The vessel was closed, connected via a reducing valve with a nitrogen bomb and heated to 200 to 22O ⁰ C.

The nitrogen pressure is maintained at approximately 30 atm and the yarn exiting the spinneret was cooled in water and wound onto a spool.

The thread was slightly sticky, but the individual threads could still be separated from each other will. The tress produced in this way is placed in the impregnation bath at room temperature for 1 hour.

The bathroom consists of:

Acetone 80 parts

chlorinated tert-butyl peroxide 20 parts

The thus treated yarn is vulcanized in an autoclave with steam for 30 minutes under a pressure of 153 atm at about ⁰ C.

The vulcanized yarn showed the following properties:

Under the microscope these threads showed certain irregularities of the diameter, which partially the lower mechanical strength can be explained.

As can be seen, the anti-aging agents were intentionally omitted from the mixtures to show the resistance properties of the polymer used.

a) The yarns prepared according to Examples 5 and 6 were immersed for 30 days at cold 68 ° / ₀ nitric acid. After this treatment, the properties of the products compared to the properties before the treatment were as follows:

Yarns in example 5

Tensile strength, g / denier ... Before the After 195 denier Elongation at break, ° / o treatment 30 days- 0.1 Continuous elongation, ° / ₀ .. with ENT ₃ treatment 520 6ο with ENT ₃ 14th Total number of eighteen threads 190 denier 0.18 450 8th

Yarns in example 6

Tensile strength, g / denier ...

Elongation at break,%

Continuous elongation,%

Before after treatment, treatment with ENT ₃ with ENT ₃

Number of eighteen threads 185 denier 190 denier

0.09 220/320 17

0.05 350

25th

Before the After 192 denier treatment treatment 0.12 with H ₂ SO ₄ with H ₂ SO ₄ 320 Total number 12th of eighteen threads 190 denier Tensile strength, g / denier ... 0.18 Elongation at break, ° / o 450 Continuous elongation,% .. 8th

Yarns in example 6

Before the After 192 denier treatment treatment 0.055 with H ₂ SO ₄ with H ₂ SO ₄ 190 Total number 22nd of eighteen threads 188 denier Tensile strength, g / denier ... 0.09 Elongation at break,% 220/320 Continuous elongation,% 17th

10

The properties after this treatment were as follows:

Yarns in example 5

b) The yarns produced according to Examples 5 and 6 were immersed in cold 98% strength sulfuric acid for 30 days immersed. After this treatment, the properties of the products were compared to the Properties before treatment as follows:

20th

Yarns in example 5

Tensile strength, g / denier ...

Elongation at break, ° / o

Continuous elongation,%

Before the
treatment

After treatment

Total number
of eighteen threads

190 denier I 185 denier

0.18
420/470
8th

0.12
420
12th

Yarns in example 6

Tensile strength, g / denier ...

Elongation at break,%

Continuous elongation,%

Before the
treatment

After
treatment

Total number
of eighteen threads

185 denier I 180 denier

0.09
420/470
8th

0.06
420
12th

35

40

45

c) The yarns produced according to Examples 5 and 6 were placed in a ventilated drying cabinet for 8 days brought at 100 ° C. After this treatment, the yarns produced according to Example 6 were slightly sticky, but the threads could still be separated.

Claims (2)

Patent claims: 1. A process for the production of vulcanized molded articles from rubber-like polymers using per compounds and optionally sulfur, characterized in that ethylene-propylene or ethylene-butene copolymers or mixtures of polyethylene or polypropylene with at least 5 percent by weight, based on the mixture, an ethylene-propylene or ethylene-butene copolymer, optionally in a mixture with fillers and / or sulfur, molded at temperatures of 160 to 300 ° C, the objects obtained are cooled with an organic per-compound dissolved in a solvent that the polymers does not dissolve, impregnated, dried, and finally cured under pressure at 100 to 22O ⁰ C. 2. The method according to claim 1, characterized in that a starting mixture is used containing 0.1 to 3 gram atoms of sulfur per mole of peroxide absorbed. Considered publications:
French Patent No. 1,215,944. 409 658 / 48S 8.64 © Bundesdruckerei Berlin