NO783997L - SOLID, HYDROLY-RESISTANT PHOSPHORIC ACID STARTERS WITH IMPROVED STABILIZER EFFECT IN PLASTICS - Google Patents

Description

Solid, hydrolysis-resistant phosphoric acid ester-tll preparations with improved stabilizer action in plastics.

Phosphoric acid esters are becoming increasingly important..as antioxidants in stabilizer systems for plastics, especially for the pulp products polyethylene, polypropylene and PVC. Due to the easier dosage and mixability with plastics, but also with the other components of the overall stabilization, solid products in powder and shell form are preferred to the liquid ones. However, their serious disadvantage is that in moist air, already partially wrapped when sent to the consumer, especially when stored and opened, they quickly hydrolyze and thereby lose their effect as a stabilizer. The hydrolysis products then react with the stabilizer system's other components, such as metal soaps, to form insoluble compounds that make the plastics cloudy and thus can sensitively disrupt the production process, if it is not completely interrupted.

The invention was based on the task of eliminating these disadvantages of solid phosphoric acid esters - and to prevent their hydrolysis or strongly to diminish it without affecting its effect.

There has previously been no shortage of attempts to improve the hydrolysis stability of phosphoric acid ester stabilizers. Thus, reference is made in DOS 2,626,225 to an already previously proposed addition of smaller quantities of an amine, since, however, in addition to only a short-term effect, very unfortunate discolorations can occur, when the phosphite treated according to this method, e.g. used in PVC.

In the same publication, it is recommended as a more suitable precaution to add metal salts of organic acids, whereby, however, the hydrolysis cannot be prevented, but its consequence is to be combated, which is for example made visible by lowering the pH. This precaution thus does not exclude the above-mentioned phenomena in the case of sieve clogging during the processing of plastic and its cloudiness.

in the case of lower-melting phosphites. That by the combination of wax with a. phosphite stabilizer, a faster and more thorough distribution in the plastic could not be predicted either.

Finally, in many cases it is by adding

few wt% wax to phosphite to observe a clear increase of the melting point. This effect is surprising, as normally when a substance is contaminated, its melting point drops. The melting point increase is . particularly advantageous when phosphite is to be used for so-called Bunker stabilization of polyolefin powder. In this process, the plastic powder falls out from the polymerization at a temperature of -approx. 60-80°C. Stabilizing mixtures containing a low-melting phosphite cake together at this temperature and can then only be distributed homogeneously into plastic powder with very high work. This disadvantage can be avoided by using phosphites whose solidification point is raised by the addition of wax. Such phosphites are also easier to confection by atomization or shell formation, moreover, they tend to stick together less when exposed to heat and pressure than untreated phosphites.

It is also surprising that with the addition of wax, the volatility of the phosphites in the heat is drastically reduced, and with a higher amount of wax it is almost completely suppressed. This effect is therefore of great importance, because it ensures that during the processing of the plastic, persons present are not exposed to any fumes harmful to health.

Phosphoric acid esters, known in and of themselves for stabilizing plastics, are understood to mean solid, organic phosphites such as e.g. di-stearyl phosphite, tri-stearyl phosphite, preferably penta-erythritol phosphite, as they e.g. is mentioned in the German Offenlegungs-schr^iften 2,219,695, 2,347,997, 2,621. 323, 2,630,257, 2,431,623

and the German patents 1,237,312 and 2,505,152, sugar alcohol phosphites according to German Offenlegungsschriften 2,633,392 and 2,633,393, as well as solid triaryl phosphites according to German Offenlegungsschrift 2,606,358. With the latter, the sometimes undesirably high melting point can be lowered by the addition of wax, as well as the particularly strong sublimation tendency of these substances to be reduced at high temperatures.

Wax means products with 20 to approx. 500, preferably between 30 and 250 C atoms in the molecule, which fall under the general definition of the term wax according to the DGF-Einheits-methoden Mil (75) as paraffins, e.g. refined table paraffin with m.p. from approx. 40 to approx. 80°C, microparaffins, synthetic paraffins incl

m.p. between '80 and 130°C, long-chain plant and insect waxes,

such as Carnauba wax, Cadelilla wax, semi-synthetic 'ester wax, such as e.g. Montane wax derivatives, synthetic waxes, such as amide waxes, e.g. distearyl-ethylenediamide, polyolefin wax, e.g. polyethylene and polypropylene wax in the molecular range from approx. 2,000 to 10,000, poly-<1>ethylene wax oxides and esters thereof, which are obtainable by the addition of dialkyl phosphites to long-chain α-olefins in the presence of radical-donating catalysts. Mixtures of the aforementioned waxes can also be used. Building polyethylene wax and amide wax are preferred, especially the latter. In the wax-phosphoric acid ester preparation according to the invention, the amount of wax should be between 3% and 80%, preferably between 5 and 40%.

The production and preparation preferably takes place in such a way that wax and the solid phosphoric acid esters are melted together. The forge is then assembled according to methods known per se, e.g. by shell formation, by brittleness, by slinging or grinding after cooling. The wax-phosphite melt can also be added to some or all parts of a collection stabilizer system as phenolic antioxidants, e.g. substituted tert.-butylphenols, organic sulphides, such as e.g. thioglycolic acid ester or distearyl sulphide, metal salts of fatty acids, such as e.g. stearate, laurate, or montanates of calcium, barium, magnesium, cadmium, zinc and lead, as well as light stabilizers such as benzophenone, triazoles or hindered amines. As these stabilizers often have a waxy character, they can also enhance the hydrolysis-preventing effect of the wax. From the range of wax types, in the case of an overall stabilizer system, the individual is selected which ensures the homogeneity of the melt of the overall mixture. With this method, one obtains an additional advantage later on being able to mix all stabilizers in one operation in the plastic.

Another possibility for preparing the preparations consists in coating fine particles of the phosphoric acid ester which is to be protected by enveloping with a wax film. This can, for example, take place by applying wax melted or dissolved in a solvent to the phosphite particles during or after the atomization or shell formation of the phosphite.

■The preparation according to the invention is used to stabilize plastic mass on the basis of jpolyolefins or of chlorine-containing polymers against the harmful effects of light and heat, namely-in amounts from 0.01 to 5, preferably .0.05. to 2% VAT,

referred to plastic mass and phosphoric acid ester quantity in the preparation. Mention must be made in certain masses of polyethylene, preferably polypropylene, copolymers of ethylene with C^- to Cj--a-olefins, polyvinyl chloride, their copolymers with vinylidene chloride and other olefins, chlorinated polyolefins, as well as of mixtures of polymers .

The invention shall be explained in more detail with the help of some . examples:

Example 1 (production example)

a) 2 g kerosene, m.p. 58-60°C, dissolve in 100 ml heptane by boiling, after cooling to 80°C stir in 18 g finely ground

isophthalic acid di-pentaerythritol phosphite ester (prepared according to DOS 2. 506 . 207, Ex. 6), after which the solvent is removed at 30°C on a rotary evaporator. b) As under a), 18 g of isophthalic acid pentaerythritol is coated with 2 g of a synthetic paraffin with m.p. 102°C. c) As under a) 18 g of isophthalic acid pentaerythritol ester are coated with 2 g of a decomposing polyethylene wax with a chain length

of approx. 200 C atoms.

d) As under a) 18 g of acetoacetic acid pentaerythritol phosphite ester (prepared according to DAS 2.505.152) is added to a heptane solution of

2 g of a polyethylene degradation wax with a chain length of approx.

200 C atoms at approx. 60°C and cool. The cooled solution. pressure filtered and then evaporated. e) Stir 20 g of acetoacetic acid pentaerythritol phosphite ester into a melt of 20 g of synthetic paraffin with m.p. 102°C and then cooled. f) Stir 10 g of di-stearyl-pentaerythritol-diphosphite into an approx. 50°C hot solution of 2 g of triacontylphosphonic acid dimethyl ester

in heptane. At 30°C, the solvent is removed in the rotary evaporator.

g) Stir 20 g of di-stearyl-pentaerythritol diphosphite into a melt of 20 g of triaceontylphosphonic acid dimethyl ester. The forging will be

formed.

Each time, 18 g of di-stearyl-pentaerythrityl-diphosphite are fused with

h) -2 g synthetic paraffin, m.p. 102°C, resp.

i) 2 g polyethylene wax, molecular weight approx. 2000 or

j) 2 g microparaffin or

k) 2 g kerosene, m.p. 58-60°C.

The melts are cast.

1) 18 g of dis-stearyl-(3-hydroxytriacontyl-sorbityl-triphosphite (manufactured according to DOS 2,633,392, Ex. 6) are combined in melt with 2 g of a synthetic paraffin with m.p. 102°C.

m) 18 g of di-stearyl-3-hydroxytriacontyl-sorbitol-triphosphite are mixed in melt with 2 g of a polyolefin wax with a chain length of approx. 200 C atoms. The mixture is stirred.

Example 2

In this example, the improved hydrolysis resistance of the phosphityl preparation according to the invention shall be shown. a) Each time 5 g of according to Ex. 1 prepared substance samples are boiled in 100 ml of desalted water for 20 minutes under reflux. It is filtered while still warm through a folding filter. From the aqueous phase, 40 ml<1>s samples are taken each time and titrated with 0.1 molar KOH against bromophenol blue.

The following table shows the degree of hydrolysis determined under these conditions as a quotient of actual lye consumption and theoretically possible lye consumption with complete hydrolysis. For comparison, the hydrolysis stability of the phosphites underlying the individual preparations is indicated.

b) Water absorption of a phosphoric acid ester preparation according to the invention compared to water absorption of the underlying one

phosphoric acid esters when stored in a water vapor saturated atmosphere.

Phosphite: Di-stearyl-pentaerythrityl-diphosphite 1 Test body: Circular plates, diam.= 60 mm, height= 5 mm Air temperature: 2 0°C i

. Humidity: 100%

Duration: 24 hours.

Example 3.

In this example, the advantageous increase in the solidification point of the organic phosphites treated according to the invention shall be shown.

a) Tristearyl sorbitol triphosphite (prepared according to DOS 2,633,393, ex. 1) with a pour/drop point (Fp/Tp) 52/53°C, mix

with 3.5% by weight of a polyethylene oxide (dropping point 117°, acid number 19)

in the forge. The cooled product has a pour/drop point of 86/91°C.

b) Tristearyl sorbitol triphosphite is melted with 4.5% by weight of a polyethylene oxide with an acid number of 9 and a dripping point of >

115°C together, you get a preparation with Fp/Tp of 76/80°C.

. c) Of the preparations 1 h) to 1 k), consisting of 90% by weight of dis-stearyl-pentaerythritol-diphosphite and 10% by weight of various waxes, it was determined by the pour/dropping point and compared with Fp/Tp of unmixed phosphite.

Example 4

In this example, the improved effect of the phosphite preparation in relation to the underlying phosphites shall be shown. From the measured values, it appears that with the preparation according to the invention, a considerable increase can be achieved both in the heat aging resistance and also in the processing resistance, although the phosphite content is always lower than in the comparison tests.

a) Heat aging resistance testing

■ On a two-roller, a mixture of

100 parts by weight of unstabilized polypropylene powder of density 0.90 (melt index is approx. 6g/10 min.

determined in connection with ASTM D. 1238-62 T)

0.15 parts by weight of 3',5'-di-tert-butyl-4'-hydroxyphenyl-propionic acid octacedyl ester and

each time 0.1 parts by weight of a phosphite or a phosphite preparation at 200°C for five minutes. The plastic ingot is then pressed at 200°C into a plate of 1 mm thickness. Strip-shaped specimens (60 x 10. x 1 mm) are punched out of the cooled plate and hung in a circulation drying cabinet on a motor-driven stand with rotating •hordes. The samples are subjected to a controlled atmosphere (fresh air supply with defined quantities) for a uniform temperature load of 140°C air temperature. As an end point, there is a period of time during which, in some places, an incipient local embrittlement occurs according to DIN 53.583, characterized by the formation of discolored, unclear, partially interrupted places. In the following table, this period is indicated in days.

b) Examination of processing resistance

From the mixture referred to under a) it was determined

melting index<s>(<i>2/300^ ^r°^after a 60-minute thermal load at 300°C. The table shows the quotient of the thus determined melting index range —^—. The smaller this

in after

quotient is, the greater the thermal degradation of the plastic melt, the less its processing stability.

Example 5

This example shows that the addition of wax according to the invention reduces the volatility of the phosphite.

Each time 1 g of phosphite is melted with 2 g of polyethylene wax (mol weight 2000-3000). An accurately weighed amount of this mixture is then stored in a heating cabinet for 2 hours at 200°C

in the air and then return.

The following table lists the volatilities determined in this way, as well as the pour/drop point compared to the starting phosphate.

Claims (9)

1. Solid, hydrolysis-resistant phosphoric acid ester preparations with improved stabilizer action in plastics, consisting of 20 to 97% by weight of a phosphoric acid ester known per se as a stabilizer for plastics and 80 to 3% by weight of a wax. 2. Preparation according to claim 1, characterized in that the wax contains 20 to 500 C atoms in the molecule. 3. Preparation according to claim 2, characterized in that the wax is a paraffin wax, a natural or semi-synthetic ester wax, an amide wax, a polyolefin wax, a polyolefin wax oxidate, or, an ester of such, or a waxy ester of a long-chain .phosphonic acid. ... 4. Preparation according to claims 1-3, characterized in that other components of a stabilization system are also added to it. 5. Method according to claim 4, characterized in that the other components of the stabilization system are sulphidic and/or phenolic antioxidants, optionally metal salts of fatty acids, as well as light stabilizers from the group of benzophenones, benztriazoles and hindered amines. 6. Method for producing preparations according to claims 1, 3, 4 and 5, characterized in that - that one either a) melts the phosphoric acid ester and the wax together and confections the melt, possibly after adding additional stabilizing components in a manner known per se, into granules or powders, or b) on the phosphoric acid ester particle, apply the wax as a melt or dissolved in a solvent. 7. Use of hydrolysis-stable phosphoric acid ester preparations of 20 to 97% by weight of a phosphoric acid ester known per se as a stabilizer for plastics and 80 to 3% by weight of a wax for stabilizing polyolefins or chlorine-containing polymers against the harmful effects of light and heat, optionally in the presence of additional stabilizers, in amounts from 0.01 to 5% by weight, referred to the polymer and phosphite portion of the preparation. 8. Process for stabilizing plastic masses based on polyolefins or chlorine-containing polymers against the harmful effects of light and heat, characterized by adding a stabilizer preparation to the masses, consisting of 20 to 97% by weight of a stabilizer for plastics in and of itself known phosphoric acid ester and 80 to 3% by weight of a wax - optionally in the presence of further stabilizers, in amounts from 0.01 to 5% by weight, referred to the polymeric and phosphite part in the stabilizer preparation. 9. Plastic mass based on polyolefins or chlorine-containing polymers, in which a preparation according to claim 1 or 4 is contained in an amount of from 0.01 to 5% by weight, referred to the phosphoric acid.