DE1118449B - Molding compound stabilized against oxidation - Google Patents

Description

Molding compositions made from practically saturated hydrogen atoms on tertiary carbon atoms Monoolefin polymers have recently found particular interest, such as. B. polyethylene, Polypropylenes, polybutene- (l) and polymers of 3-methylbutene- (l), 4,4-dimethylpentene- (l) and dodecene- (l). The hydrogen atoms bound to tertiary carbon atoms are in the polymer either statistically distributed according to number and spatial arrangement, or they are in regular arrangement.

Polyethylene, which is the best known of this class of monoolefin polymers, has considerable technical importance for molding and coating compounds as well as insulating and dielectric material. One of the main advantages of polyethylene is its high dielectric strength combined with its repellent properties against water and water vapor. Due to its very good mechanical properties, like tensile strength and abrasion resistance, polyethylene is increasingly used as a material for Cable sheaths.

Unfortunately, however, monoolefin polymers of the type under consideration here are exposed to sunlight and Heat affected. Both factors lead to the oxidation of the polymer and adversely affect it thereby the tensile strength, the low temperature brittleness point and the dielectric properties. Since the thermal oxidation is accelerated considerably by increasing the temperature, result during deformation, extrusion or other manufacturing processes that involve high temperatures work, difficulties. Both types of oxidation can also be used when using the polymers occur in the open air.

The purely oxidative degradation of z. B. Polyethylene has received significant research attention found, and an extensive class of "anti-oxidants" has been developed to support the Effective protection of polymers against thermal oxidation, even in very small quantities. These Antioxidants are generally aromatic compounds that have a substituent Hydroxyl group or a secondary amino group, the compound either by a bulky substituents or by the nature of the core is so sterically hindered that the lifetime of the antioxidant is extended. Typical steric hindrance substituents are alkyl groups with more than 4 carbon atoms, which may be branched to give the Increase bulkiness. An excellent graduation

Molding compound stabilized against oxidation

Applicant:

Western Electric Company, Incorporated,
New York, NY (V. St. A.)

Representative: Dr.-Ing. K. Boehmert

and Dipl.-Ing. A. Boehmert, patent attorneys,

Bremen 1, Feldstr. 24

Claimed priority:
V. St. v. America of November 29, 1956 (No. 625 184)

Walter Lincoln Hawkins, Montclair, NJ,
and Vincent Leonard Lanza, Berkeley Heights, NJ

(V. St. Α.),
have been named as inventors

dealing with antioxidants and the requirements of "resonance" and steric Prevention of such compounds was described by Wheland in "Advanced Organic Chemistry", 2nd edition, Cape. 9 and 10, published. A more detailed discussion of mining of polyethylene can be found in "Modern Plastics", Vol. 31, pp. 121 to 124, September 1953.

To prevent the absorption of ultraviolet rays, on the other hand, a very fine dispersion of carbon black particles is used in the monoolefin polymers with a particle size of at most 1000 Å in amounts of 0.5 to 5 percent by weight of the polymer a. This carbon black dispersion acts as a light protection and reduces UV absorption.

So far, however, it has not yet been possible to stabilize the monoolefin polymers in question against both influences, namely UV absorption and thermal oxidation, by combining the two To achieve additives. Unexpectedly, the combination of soot with the antioxidants results trading at z. B. Polyethylene is not an improvement, but on the contrary a reduction the duration of protection against degradation through thermal oxidation many times over. Lose in many cases Otherwise quite effective antioxidants in the presence of carbon black their effectiveness even completely.

109 747/582

Experimental investigations with the aim of replacing the soot with other light stabilizers have not yet led to a success. With the technical Attempted to circumvent this obstacle by applying the polymer in the case of the Application of soot is loaded with increasing amounts of antioxidants. Still has but even increasing the amount of antioxidant to the limit of compatibility with the Polymers do not lead to an increase in the duration of protection against degradation which is sufficient in practice guided by thermal oxidation.

It has now surprisingly been found that these difficulties can be eliminated and an effective protection of the respective monoolefin polymers against decomposition achieved as a result of UV absorption as well as against the damage caused by thermal oxidation can be. According to the invention, the polymers are used as a stabilizer from 0.5 to 5 percent by weight, based on the total mixture, of soot with a particle size of at most 1000 Å in the mixture with 0.01 to 5 percent by weight, based on the total mixture, of a compound incorporated which the general formula

A commercially available compound falling under the above general formula (1) is 4,4'-thio-bis- (6-tert-butyl-m-cresol), which has the following structural formula:

CH

CH ₃

- (OR) _x

, XX

in which χ is an integer from 1 to 3, R is a normal alkyl radical with 6 to 20 carbon atoms or a branched-chain alkyl radical with 3 to 6 carbon atoms and R 'is a hydrogen atom or a normal alkyl radical with up to 6 carbon atoms . In the above general formula, the total number of carbon atoms in the remainder of the molecule in square brackets must not be greater than 30, since a larger number of carbon atoms would result in a too bulky molecule, whereby the easy dispersibility of the thioether in the polymer would be hindered. As a substituent R, a normal alkyl radical with six or more carbon atoms is just as suitable as, for. B. a tert-butyl substituent.

Examples of compounds within the general formula given above are: 4,4'-thio-bis- (6 - tertbutyl - 3 - ethylphenol), 4,4 '- thio - bis (6 - tert.-butyl-3-n-propylphenol), 4,4'-thio-bis (6-tert-butyl-3-isopropylphenol), 4,4'-thio-bis- (6-tert-butyl-3-n-butylphenol), 4,4'-thio - bis - (6 - tert.butyl - 3-isobutylphenol), 4,4'-thio-bis- (6-tert-butyl-3-sec-butylphenol), 4,4'-thio-bis- (6-tert-butyl-3-tert-butylphenol), 4,4 ' -Thiobis- (6-n-amyl-3-methylphenol), 4,4'-thio-bis- (6-isoamyl -3-methylphenol), 4,4'-thio-bis- (6-sec.amyl-3-methylphenol), 4,4'-thio-bis- (6-tert-amyl-3-methylphenol), 4,4'-thio - bis - (6 - amyl - 3 - ethylphenol), 4,4 '- thio - bis - (6 - amyl - 3 -propylphenol), thio - bis (5-decylresorcinol), Thio-bis- (5-octadecylresorcinol), thiobis- (5-pentadecylcatechol), thio-bis- (5-decylpyrocatechol).

As will be noted, all of the stabilizer components used in the present invention are phenolic Compounds that differ from commercially available secondary amines, which has the advantage of that in general there is no discoloration of the monoolefin polymers.

The carbon black is preferably present in the new stabilized molding compositions in amounts of 3 percent by weight. However, the carbon black concentration should not exceed 5 percent by weight, since otherwise the low-temperature brittleness of the mono-olefin polymers is worsened. On the other hand, the specified lower limit value is also important, since the presence of less than 0.5 percent by weight of carbon black does not guarantee adequate protection against UV absorption and the damage associated therewith.
It is known per se that depolymerization of polystyrene, polyisobutylene and similar polymers, which occurs when heated, can be prevented by adding certain inhibitors. These are essentially phenols and thiophenols, which, however, have no real anti-oxidation effect, since the polymer in question does not absorb any oxygen during depolymerization. In the stabilizer mixture according to the invention, on the other hand, the advanced technical effect is achieved through a special interaction of the carbon black particles with the phenolic thioethers of the general formula (1) given, and attack by oxygen in particular can be effectively combated.

The following examples relate to molding compositions composed according to the invention, which the new Stabilizer included.

Mixture A

Weight percent

Commercial sewer black (particle size 180 Å) 3.0

4,4'-thio-bis- (6-tert-butyl-m-cresol) ... 0.1
Commercially available high pressure polyethylene 96.9

Mixture B
Commercial sewer black (particle size 180 Å) 3.0

Thio-bis (5-pentadecylresorcinol) 0.1

Commercially available high pressure polyethylene 96.9

Mixture C
Commercial sewer soot (particle

6 _S size 180 Ä) 3.0

4,4'-thio-bis- (6-tert.butyi-m-cresol) .. 0.2
Commercial high pressure polyethylene 96.8

The advantages achieved according to the invention result in zen speeds of approximately 25 or 35 rpm.

from those described below and through and at a roller temperature of approximately 120 ° C

graphical representations of explained results of marrying together. The soot-containing mixtures

Aging tests, which show that neither one were made from a premix that was 25 ° / ₀

Carbon black additive only contained an addition of a stabilizer 5 carbon black in polyethylene, in order to ensure good consistency.

Component of the type indicated for an effective division of the carbon black in the bulk of the polyethylene

ensure seed stabilization of the molding compounds in question. In all cases, after

leads. The combined use of carbon black means that the same grinding process is used. This method

and the new thio compounds, on the other hand, were known to have the best possible dispersion

Achieve a remarkable effect that goes far beyond the io alloying of the antioxidant and the soot

Cumulative effect of the stabilizer component in the polyethylene caused.

goes. For the aging tests, this was done in the following manner. After preparing the desired mixture

In the accelerated test procedure described in more detail, the mass became test skins with a thickness of

drive used, being the limit for the prak- roughly 1.27 mm deformed. From these skins

The usefulness of the molding compounds was the time - 15 disks with a diameter of 14 mm were

point is used where oxygen uptake is cut. Four such discs were in each

of the sample in question of 10 cm ³ / g observed on a flat glass dish together with about 2 g

will. powdered barium oxide or another

In the drawings, the oxygen uptake in absorbent in a tube of Pyrex glass is one cubic centimeter brought per gram of sample (ordinate) 20, which indicated on a mercury manometer the time is plotted in hours (abscissa). was closed. The reaction vessel was used several times

Fig. 1 shows test values in two curves, alternately evacuated and again with oxygen, which fill the oxygen absorption of a sample of at least 99.5% purity in order to ensure the polyethylene with a content of 0.1 weight - absence of atmospheric gases, percent of 4,4'-thio-bis- (6-tert-butyl-m-cresol) without 25 Then it was put in an oven with air circulation an addition of carbon black (curve 1) and in combination with, which was built so that a given temperature represents 3% of dispersed soot particles, the particle temperature of which is 180 Å (curve 2) ^{with a margin of ± I 0 C.} In addition, the entire furnace chamber could be maintained, and a reference curve for a polyethylene sample is immediately drawn in without any additive through a short piece of polyvinyl tubing. 30 chloride with an oxygen-filled gas burette

In Fig. 2, curve 3 represents the experimental values for a connected. The oven was heated ^{to 140 ° C. beforehand}

Polyäthylenprobe been at a level of 0.1% ^to. After reaching equilibrium at

Thio-bis- (5-pentadecylresorcinol) and curve 4 the temperature 140 ° C was the system at atmospheric pressure

values for a sample of polyethylene adjusted 3% to zero reading. The reading of the

Soot with a particle size of 180 Å and 0.1% 35 oxygen absorption took place as required at atmo-

of thio-bis- (5-pentadecylresorcinol) contains. At spherical pressure, every 4 to 12 hours

For the same purposes, the reference curve shows the oxidation reading taken.

speed of polyethylene, which is neither one of the graphs shown in FIGS

Anti-oxidant still contains soot. Thio-bis measurement results can be seen that even the

(5-pentadecylresorcinol) has the structural formula 40 best-working carbon black, which also in a mixture

was used with the thio compounds

OH

HO

Application as the only stabilizer the so-called

thermal oxidation about 40 hours at the most

(3) able to prevent long. An addition to the relevant

45 sulfur-containing stabilizer component alone leads

likewise to an unsatisfactory result, and

in some cases even accelerated acid

Material uptake compared with the polyethylene sample For comparison, the results on without any additive are observed in FIG. 3. With an addition of samples made of polyethylene with an addition of the stabilizer according to the invention, on the other hand, a wide variety of commercially available types of carbon black are not only absorbed for many hours, which shows that carbon black is added later, but also proceeds that way slowly, so that in no case is only suitable for an effective suppression of the critical limit value of oxygen uptake by thermal oxidation of 10 cm ³ / g of the polyethylene sample only after approximately. With the types of carbon black No. 2 and No. 4 55 190 hours or even in one case only after it was a furnace soot with an approximately 750 hours being reached. The respective average particle sizes of 360 and 190 Å. Molding compounds therefore retain their favorable physical type of carbon black. No. 3 was a sewer black with a particle size and, in particular, a dielectric inherent size of an average of 330 Å. A short description of the 60 accelerated aging test in reality a test procedure is given below. This procedure provided the usability equivalent of several years.
Results on which FIGS. 1 to 3 are based. In connection with carbon black within the meaning of the invention

used stabilizer components are

Accelerated test procedure by condensation of the single-core

65 phenolic compound with sulfur dichloride

The polyethylene was protected against oxidation. Below are two examples of mediation and, if necessary, the carbon black in a two-way for the production of the compounds, roller mill (dimensions 15.2x30.5 cm) with whale to which in FIGS. 1 and 2 reference is made

will. However, no protection is claimed for these manufacturing processes within the scope of the invention.

Production of 4,4'-thio-bis- (6-tert-butyl-m-cresol)

A three-necked round bottom flask was equipped with a Herschberg mechanical stirrer, a dropping funnel and a water condenser. The flask was charged with 94.4 g (0.58 mol) of 6-tert-butylm-cresol and 400 ecm of carbon tetrachloride. The stirrer was set in motion, and when the 6-tert-butyl-m-cresol was completely gone into solution, a cold solution (about 0 ⁰ C) of 29.4 g (0.28 mol) of sulfur dichloride was dissolved in 100 cc Carbon tetrachloride added dropwise over 48 minutes. Before the start of the reaction, the contents of the reaction vessel and the dropping funnel were at room temperature (24 ° C.). After about half of the sulfur dichloride solution had been added, a white precipitate began to form. At about the same time, a slight rise in temperature became noticeable, and the temperature reached a maximum value of 31 ^° C. during the further addition. After the addition of the sulfur dichloride had ended, the mixture was stirred for a further 1 hour. The contents of the reaction vessel were filtered. The deposited crystals were recrystallized from benzene. 3.7 g of a white crystalline substance with a melting point of 160 ^° C. were obtained as the end product. The melting point value and other test values indicated that this material was 4,4'-thio-bis- (6-tert-butyl-m-cresol).

Production of thio-bis- (5-pentadecylresorcinol)

A three-necked round bottom flask was equipped with a Herschberg chromium-nickel wire stirrer, a dropping funnel and a water condenser. The flask was charged with 6.5 g (V ₈ mol) of pentadecylresorcinol and 500 ecm of anhydrous ether. The stirrer was started and as soon as the pentadecylresorcinol had completely dissolved, which took about 2 or 3 minutes, a solution of 6.5 g (Vi ₆ mol) of sulfur dichloride in 15 ecm of anhydrous ether was added dropwise over 40 minutes added. Before the start of the reaction, the contents of the reaction vessel and the dropping funnel were at room temperature (24 ° C.). After about one third of the sulfur dichloride solution had been added, a slight increase in temperature was noted, with the temperature reaching ^{a maximum of 31 ° C.} After the addition of sulfur dichloride had ended, stirring was continued for a further hour. The contents of the reaction vessel were then transferred to a still and most of the solvent was distilled off under reduced pressure. After repeated recrystallization from absolute ethanol, a light brown colored crystalline compound was obtained. Yield: 7.9 g; F. = 157 ^° C. The melting point, which also agreed with the analysis, showed that the end product was thio-bis- (5-pentadecylresorcinol).

Claims (6)

PATENT CLAIMS: 1. Molding compound stabilized against oxidation and made up of practically saturated hydrogen atoms tertiary carbon atoms containing monoolefin polymers, containing as stabilizer 0.5 to 5 percent by weight, based on the total mixture, of carbon black with a particle size of a maximum of 1000 Å in a mixture with 0.01 to 5 percent by weight, based on the total mixture a compound of the general formula _R XX _R , in which χ is an integer from 1 to 3, R is a normal alkyl group with 6 to 20 carbon atoms or a branched-chain alkyl group with 3 to 6 carbon atoms and R 'denotes hydrogen atom or a normal alkyl group with up to 6 carbon atoms and the number of carbon atoms in the The remainder in square brackets is not greater than 30. 2. Molding composition according to claim 1, containing a homopolymer or an olefin polymer Mixed polymer. 3. Molding composition according to claim 1, containing carbon black and 4,4'-thio-bis- (6-tert-butylm-cresol) as a stabilizer. 4. Molding composition according to claim 1, containing carbon black and thio-bis (5-pentadecylresorcinol) as a stabilizer. 5. Molding composition according to claim 1 to 4, containing as olefin polymer polyethylene or polypropylene. 6. Molding composition according to claim 1, containing polyethylene, 4,4'-thio-bis- (6-tert-butyl-m-cresol) and soot. Considered publications:
British Patent No. 496,966;
U.S. Patent No. 2,727,879. When the registration was announced, 1 priority document was displayed. 1 sheet of drawings © 109 747/582 11.61