DE1167015B - Process for the production of highly filled moldings from polyethylene - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school KL: C08f

German class: 39 b-22/06

Number:
File number:
Registration date:
Display day:

C 15142IV c / 39 b
July 10, 1957
April 2, 1964

Polyethylene and other ethylene-derived polymers have been in the normal fields of application of plastics have largely found their way into and well received. However, in spite of them, stood many fundamentally desired properties of the extensive use in fields of application, where they are exposed to particularly high loads, there are some deficiencies. Among the greatest of these Disadvantages include low strength, especially at elevated temperatures, and susceptibility to degradation, in particular through oxygen and sunlight, or premature cracking when exposed to the weather, Water or soaps and other environmental influences.

The polymerization at relatively low pressures and in the presence of heterogeneous organometallic Catalysts made polyethylene, which are characterized by a linear structure and higher They are characterized by crystallinity and have higher densities and higher molecular weights than the usual high-pressure polyethylene have a higher strength, especially at elevated temperatures and can be used in a wider temperature range than the usual polyethylenes. she however, they also have certain disadvantages. For example, they are more difficult to process and show after processing a greater shrinkage, so that the dimensional stability becomes difficult Problem becomes. Furthermore, they are because of the expensive catalyst used and difficult to remove the catalyst residues from .dem polymer uneconomical.

Protection against ultraviolet light is just as necessary with these linear types of polyethylene as with the High pressure polyethylenes. It has already been established that the resistance to degradation by UV light can be greatly improved by adding small amounts of soot. For example, 1 to 4 range Weight percent carbon black for this purpose, and these amounts are compatible with any type of polyethylene. However, the flexibility especially of the high molecular weight, linear polyethylenes deteriorates with high Dense quickly due to the presence of large amounts of soot.

It is true that the addition of carbon black and other fillers to polyethylenes increases their softening point and strength at high temperature is increased somewhat, but the embrittlement temperature is thereby worsened.

Given the much lower cost of carbon black and many other fillers compared to polyethylene, especially in comparison to the linear process for the production of highly filled moldings made of polyethylene

Applicant:

Cabot Corporation, Boston, Mass. (V. St. A.)

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald,

Dr.-Ing. Th. Meyer

and Dipl.-Chem. Dr. rer. nat. J. F. Fues,

Patent attorneys, Cologne 1, Deichmannhaus

Named as inventor:

Eli M. Dannenberg, Waban, Mass. (V. St. A.)

Claimed priority:

V. St. v. America July 12, 1956,

dated November 15, 1956

Low pressure polyethylenes, the economic disadvantage is the fact that there are no substantial amounts of filler can be mixed, easily seen.

With one exception, it has so far proven impossible to use a polyethylene with good strength high temperature, high softening point and good flexibility properties with an addition of filler of over 5 percent by weight. This one exception is the treatment of polyethylene by electromagnetic radiation with a wavelength lying in the UV range or shorter. However, this treatment is expensive, cumbersome and by no means uniform to all forms and Polyethylene article sizes applicable.

The invention now relates to a process for the production of highly filled molded bodies from a polyethylene which is solid at room temperature with crosslinking with the aid of peroxides and with the addition of fillers, which is characterized in that at least 5 parts by weight of a filler with a pH are added to 100 parts by weight of the polyethylene. Value not below 5 or one with a pn value below 5, which is neutralized by an amine or another alkaline additive, and with an average particle size of less than about 1 μ and 0.5 to 10 parts by weight of di- (a- aralkyl) peroxide at temperatures not significantly above 127 ⁰ C

409 557/552

works, the mass thus obtained, optionally in a
Press, deformed and to temperatures of at least
135 ⁰ C brings.

According to the invention, organic peroxides
applied in which those on the alkyl radicals
Λ-substituted aryl groups by alkyl, chlorine or nitro groups, but not by aryl groups,
can be substituted.

It has surprisingly been found that each

The exact temperature to be used in the heat treatment of the material according to the invention after mixing and molding depends largely on the wall thickness of the article and on the rate of reaction desired in this part of the processing step. For most articles, that is to say with wall thicknesses of approximately 25 mm or less, a temperature of approximately 135 to approximately 205 ^° C. is preferably used. The time required for carbon black and any inorganic pigment to decompose substantially all of the peroxide in the average particle size range and to effect the desired changes in the approximately 1 micron properties of the processed material used in the method according to the invention will be can, provided that the filler is not in the upper part of this temperature range has a pn value below about 5. Even strongly acidic about 2 to 15 minutes, while in the lower part of these fillers can be used if such a temperature range, times of 30 to 120 minutes, amount of an amine or another alkaline amount may be required.

Additive is added that this acidity Die by the method according to the invention

is neutralized. manufactured finished products are characterized by

The pigment and the peroxide can be found in the exceptionally good properties and are in Polyethylene incorporated in any desired way 20 in this respect the previously known polyethylenes be considered in which by intensive mixing a good superior, no matter what method they use Distribution is achieved. For example, the accessories may have been produced. The process products are in Mixture to the plastic on a two-roll another temperature range applicable as a result calender or in a Banbury mixer or in the achieved increase in the softening point and any other suitable high-shear mixer without the usual heat resistance effect, the loss of flexibility occurring for treatment and mixing and have a higher used for viscous materials. It was found to be strong impact resistance and a lower embrittlement, that the order in which the pigment temperature. These advantages are all the more remarkable and the peroxide added, has no bearing on the fact that the products Has. However, the peroxide usually becomes 30 last due to the possibility of a much higher addition added to reduce the time it takes to make it while on lower cost fillers, the processing of the batch at higher temperatures than is normally the case. is exposed. This can be particularly important when the advantages of the invention become particularly clear

high molecular weight polymers with relative in terms of cost and simplicity of the process high softening point, for example in the region of 35 when compared with that to improve the Eigenvon 116 to 127 ° C. Shafts of polyethylene compounds applied

The maximum amount of pigment that, according to the invention, known high-energy irradiation that can be used to produce, depends on the products with similar properties as they are made in the respective plastic and the respective incorporated according to the invention. The type of th pigment. For the optimal addition, the treatment by irradiating with high energy is, however, extremely difficult to use particle fineness of the pigment and the molecular weight and the more weight and the viscosity of the polymer are decisive, more difficult and expensive, the greater the wall thicknesses of the amount of pigment as the particulate article or the amount of filler increases, or as the fineness and molecular weight and the more complicated the shape becomes. A problem that has to be smaller due to increasing viscosity, and on the other hand the "masking effect" of the fillers. In conventional polyethylenes with a larger diameter, it is also due to the fact that it is difficult even under average molecular weights of 20,000 to 30,000 under the best conditions; about 200 parts and more per moderate exposure. At pigment concentrations that are added to 100 parts of plastic, while at 50 are significantly above 35 parts per 100 parts of the polymer, the inadequate molecular weight uniformity of 60,000 to 200,000 is the maximum addition of pigments in the particle size range
below about 80 ΐημ on the order of 25 to
70 parts per 100 parts plastic tends to lie. 55
Regardless of the molecular weight of the polyethylene, however, the optimal addition is for pigments
with larger particle diameters higher than at
those with a smaller particle size.

The optimal amount of peroxide is usually in the 60 of 2.1, specific gravity of 0.92 and range of about 1 to 3 parts by weight per 100 parts of an average tensile strength of about 123 kg / polyethylene. For economic reasons, cm ² at 23 ° C. was rarely added in amounts greater than 5 parts by weight per 100 parts of a two-roll calender, which was heated to about 93 ° C., to a mass with polyethylene together, as it was generally kneaded by a higher hanging consistency. In the bulk quantities, no additional benefit was obtained. An upper limit of 65 per 100 parts by weight of polyethylene 44 parts by weight is considered to be an amount of 10 parts of a highly reinforcing oil furnace black with an average particle size of about 17 to 17 parts by weight peroxide per 100 parts by weight of polyethylene. 20 ΐημ, a pH of about 9.8 and an average

irradiated materials are getting bigger, so they can be used for many purposes, especially where high Pressures occur, e.g. B. in pipes, are unsuitable.

The advantages of the invention are illustrated by the following examples:

Example 1 A high pressure polyethylene with a melt index

Union specific surface of about 138 m ² / g and 3 parts by weight of technical dicumyl peroxide with a purity of about 95% incorporated evenly.

After being removed from the roller, the highly filled material was shaped into panels with a thickness of about 1.6 mm ^{by heating it in a press to 160 ° C. for one hour.}

The resulting panel was remarkably pliable, tough and strong, particularly in terms of impact resistance. For example, it could be bent sharply repeatedly at room temperature without too much tear or break, while panels of the same thickness, which are removed by the usual procedures the same polyethylene with the same or significantly higher carbon black addition, so brittle are that on the first or second sharp bending or kinking they will crack or even at room temperature break.

The greatly improved properties that are achieved with this polyethylene-FüUstoff mixture results from the stated measured values, the following the properties of the same polyethylene, which the the same amount of carbon black, but no dicumyl peroxide was added, are compared.

Table 1
Polyethylene with 30 percent by weight carbon black

Measured properties Sample with dicumyl peroxide Sample without dicumyl peroxide A. Specific tensile strength at room temperature ...
B. Embrittlement temperature
C. Dimensional stability at 150 ^° C 253 kg / cm ²
below -60 ° C
very good 160 kg / cm ²
above +25 ⁰ C
very bad

These values show that the polyethylene with the addition of peroxide at - 60 ⁰ C is more flexible than a processed in the usual way with the same polyethylene having the same Rußdosierung at 25 ° C. In spite of this improved flexibility, it is more at any temperature and dimensionally stable. The improvement of the dimensional stability appears obvious in the different deflection of 12 mm wide strips which are cut from the above Polyäthylentafeln and clamped at one end in a horizontal position in a room kept at a constant temperature of 150 ⁰ C oven. After 5 minutes, the strip produced without the addition of dicumyl peroxide has become so soft that it has bent downwards through its own weight at right angles to its original position over its entire free length of about 5 cm, while the free end of the strip is made of the material produced with the addition of dicumyl peroxide has only a very small passage (about 12 mm from the original position).

If 2 parts of dicumyl peroxide are used instead of 3 parts in the above experiment, the improvement in properties is almost as great. When the panel at 188 ° C instead of being molded at 160 ⁰ C, the convergence of the results obtained with 2 parts of dicumyl peroxide to the above values is even greater.

Example 2

A high molecular weight polyethylene with a melt index of 2.1 produced in the low pressure process, into which about 11 parts by weight of a highly abrasion-resistant furnace carbon black with a pH of about 9.0 and a particle size of 23 to 25 ηαμ per 100 parts of polyethylene were incorporated in the usual way already brittle at a temperature of 20 ⁰ C. by the addition of 1.5 parts by weight of dicumyl peroxide having a purity of 95% in addition to 11 parts by weight of carbon black for the same polyethylene and heating the shaped material to panels for 30 minutes at 160 ⁰ C, a material can be obtained, which is ^{not only completely flexible at 2O 0} C, but also has a higher softening point and a higher tensile strength than the comparison sample.

Instead of the 1.5 parts of dicumyl peroxide used in the above example, you can achieve the same success about 2 parts of bis (p-tert-butylcumyl) peroxide are added.

From the above examples it can be seen that the mixtures used according to the invention in unexpectedly have better properties than polyethylene filler mixtures produced by known processes.

Although carbon black is preferably used as filler for the mixtures used according to the invention, however, other known, neutral or alkaline fillers can also be used as additives. Suitable fillers are, for example, carbonates and silicates of calcium, magnesium and others Metals.

In addition to the organic peroxides specifically mentioned in the above examples, the following a-aryl-substituted Alkyl peroxides are used:

A. Symmetrical peroxides
Bis (<x-phenylethyl) peroxide,
HH

C ₆ H ₅ - C - O - O - CC ₆ H ₆

CH ₃ CH ₃

or bis («- methylbenzyl) peroxide;

Bis - («- p-isopropylcumyl) peroxide,
CH ₃ CHs

C-O-O-C

CH ₃ CH ₈ CH ₃

Bis - («- p-nitrocumyl) peroxide,
CH ₃ CH ₃

O _a N <

C-O-O-C

NO ₂

CH ₃ CH ₃

and their isomers, homologues or derivatives.

B. Unsymmetrical Peroxides

\ -Cumyl - «- p-tert. ~ Butylcumyl peroxide,

CH ₃

CH ₃

—C-O-O — C—

CH ₃

CH ₃

\ -Cumyl- ü-p-xylyl peroxide,

CH ₃

ρ O

CH ₃

Γ "

-CH ₃

x-cumyl--diphenylmethyl peroxide,

CH,

V-C-O-O-C-H

CH ₃

Ä-Cumyl-Ä-a'-naphthylmethyl peroxide,

CH.

V - C - O - O - C -

CH ₃ H χ

Ä-Cumyl-si-p -nitrocumyl peroxide, CH ₃ CH ₃

—C — O — O — C— <

-NO «,

CH ₃ CH ₃

and their isomers, homologues or derivatives.

Example 3

A weighed mass is placed on a two-roller mill, the rollers of which are heated to around 93 ° C from the high-pressure polyethylene of Example 1 to a uniform, cohesive consistency worked through. The following substances are used for every 100 parts by weight of this polymeric composition added and carefully incorporated:

1. 75 parts by weight of a precipitated calcium silicate with an average particle size of a diameter of 60 m μ. The precipitated calcium silicate has a in aqueous suspension PH of about 10.

2. 2.5 parts by weight of technical dicumyl peroxide (purity about 95%).

After the skin has been removed from the roller mill, the mixture becomes sheets 1.6 mm thick deformed and heated in the platen press at about 175 ° C minutes.

A sample cut from the finished sheet was tested and found to have a yield strength of 2.9 kg / cm ² at about 23 ° C. The finished product swells CH ₃ only slightly when immersed in xylene for 24 hours.

; 5 den at 80 ° C, and it only loses 14 ° / ₀

- C - CH ₃ weight. On the other hand, the starting point is high pressure poly

Ethylene is completely soluble in xylene at 80 ° C.

£ j_ [The particular advantages of the procedure according to the

Invention can be seen in the fact that the so

ίο manufactured fittings through the use Larger amounts of certain fillers in connection with the peroxides result in a significant increase in the Yield strength, especially at elevated temperatures. What is surprising here is the fact that with this increase there is not at the same time a remarkable loss of flexibility or resistance compared to the low temperature brittleness fracture and, moreover, the increase in tensile strength and resistance to Stress cracking again without significant loss of flexibility at low temperatures goes hand in hand. Also highly filled shaped pieces, but in contrast to the method according to the invention in the absence of the peroxides mentioned are so under the same conditions brittle in that they are only suitable to a very limited extent for most applications.

Claims (4)

Patent claims: 1. Process for the production of highly filled moldings from a polyethylene which is solid at room temperature with crosslinking with the help of peroxides and with the addition of fillers, thereby characterized in that one in 100 parts by weight of the polyethylene at least 5 parts by weight a filler with a pH value not below 5 or one with a pn value below 5, which is neutralized by an amine or other alkaline additive, and with a medium one Particle size of less than about 1 μ and 0.5 to 10 parts by weight of di - («- aralkyl) peroxide at temperatures not incorporated significantly above 127 ° C, the resulting mass optionally in a Press deformed and brought to temperatures of at least 135 ° C. 2. The method according to claim 1, characterized in that when using carbon black as Filler heat-treats the molded articles for 2 to 60 minutes. 3. The method according to claim 1 and 2, characterized in that when using polyethylene of an average molecular weight of 20,000 to 40,000 the mixing of the ingredients at temperatures of 80 to 107 ° C and the subsequent curing at temperatures between 135 and 205 ⁰ C is carried out . 4. The method according to claim 1 and 2, characterized in that when using polyethylene having an average molecular weight of 50,000 to 250,000 mixing the ingredients at temperatures of 107 to 130 ° C and the subsequent hardening at temperatures between 149 and 205 ° C is carried out. References considered: U.S. Patent No. 2,528,523. * 09 557/552 3.64 © Bundesdruckerei Berlin