CS214344B1 - A synergistic mixture to improve the color stability of acrylonitrile polymers - Google Patents

Abstract

The invention relates to a synergistic mixture for increasing the color stability of acrylonitrile polymers. The synergistic mixture contains a dienophile and a reducing agent. The advantage of the synergistic mixture according to the invention is a reduction in the total content of stable components in the polymer and an improvement in the stable system. The invention can be used in the production of acrylonitrile polymers.

Description

The invention relates to a synergistic composition for improving the color stability of acrylonitrile polymers.

Acrylonitrile polymers have been commercially important for many years. This term also includes, according to customary practice, polymers of acrylonitrile itself or methacrylonitrile itself, and copolymers thereof with other monomers, in particular styrene, butadiene, alphamethylstyrene and butyl acrylate, with a separate group consisting of biphase ABS-type polymers containing elastomeric , most commonly based on polybutadiene, and a glassy phase, most often based on a copolymer of stytene-acrylonitrile. A well-known property of acrylonitrile polymers is their susceptibility to yellowing to browning or even blackening under elevated temperatures, in particular at temperatures of 150 to 250 [deg.] C., which are customary for their processing. In some cases, such as butadiene-acrylonitrile emulsion copolymers, film yellowing also occurs to a much greater extent when stored at normal temperatures than with acrylonitrile-free polydiene alone. This particular deficiency of acrylonitrile polymers is attributed to the mutual reaction of the nitrile groups that are part of the polymer chains. When acrylonitrile groups form longer sequences in the polymer, either due to the inheritance of copolymerization or due to specific conditions in their synthesis, the color instability of the polymer is generally higher than in the absence of these sequences.

It is known that acrylonitrile polymers can be stabilized against discoloration under thermal stress by addition of aluminum salt such as borate, aluminum, aluminum chloride, aluminum sulfate / US 2661343 / by adding calcium salts such as CaCl _2, Ca / No ^ / j / USA 2661344 /, addition of strontium salts such as SrCl ₂ Sr./No _3/2, strontium maleate / US 2661345 /, addition of a chloride or a borate manganatélio / US 2661346 /, the addition of maleic anhydride or acid / USA 2 661,347 /.

A major disadvantage of the application of said salts to the polymer is their adverse effect on the appearance properties of the moldings and on the corrosion of the processing equipment; these phenomena are due to the incompatibility of the inorganic salts with the organic polymer and the release of part of the bound acids at the processing temperatures. In the case of application of maleic anhydride or maleic acid, volatilization of maleic anhydride from the melt is impeded, which in addition to the corrosive effects on metals also leads to a serious deterioration of the working environment. It has recently been proposed to stabilize acrylonitrile polymers by the addition of monoalkyl males of four and 22 carbon atoms in alkyl (U.S. Pat. No. 3,984,499) or dialkyl tin maleate or monodecyl esters thereof (U.S. Pat. No. 3,907,932). In both cases, it is desirable, for reasons of hygiene and cost, to keep the concentration of these added substances as low as possible, since their thermal decomposition at the processing temperatures results in the formation of maleic anhydride. High concentrations of these substances in the polymer are undesirable also because of their adverse effect on the heat resistance of the product.

These drawbacks of known additives can be reduced or eliminated by using the synergistic mixture of the invention. According to the invention, a synergistic mixture of dienophile and reducing agent is used to increase the color stability of acrylonitrile polymers, the weight ratio of which is in the range of 90: 10 to 10: 90, preferably dioctyl maleate as dienophile and dilauryl thiodipropionate or trisonylphenylphosphite or beta-tert-dodecylmer, ptopropionitrile.

As a dienophile, substances capable of Diels-Alder addition to a conjugated double bond system may generally be used, in particular mono- and dialkyl maleates, alkyl acrylates, acrylamide derivatives, mono- and dialkyl fumarates. Examples of such materials are dioctyl maleate, dibutyl maleate, monooktyl maleate, methylene bisacrylamide, dodecyl acrylate.

In general, substances which degrade peroxides or hydroperoxides, for example tetramethylthiuram disulfide, sodium formaldehyde sulfoxylate, diethylhydroxylamine, dilauryl thiodipropionate, zinc phenylethyldithiocarbamate, beta-dodecylmercaptopropitol, are used as reducing agents. Reducing agents containing varying valence metal ions, such as Fe, Co, Ni, Ti, Cu, are not suitable, as these may in some cases catalyze unwanted side reactions in the polymer.

The presence of conventional antioxidants which are used to stabilize unsaturated elastomers in ABS resins is generally not an obstacle to the application of the synergistic composition of the invention. However, it is desirable to take into account the color intensity of their oxidation products during their run-out.

The dosing of the synergistic components may be carried out together or separately at a suitable stage of manufacture, for example in the manufacture of emulsion ABS polymers into latexes or dry powder prior to granulation. When dosing during production, it has to be taken into account that many dienophils are capable of polymerization or other side reactions (hydrolysis). The condition of the stabilizing effect is the presence of dienophile in the mass at the time of thermal stress. In the case of the second component of the synergistic mixture, i.e., the reducing agent, the beneficial effects of the portion are achieved even if the agent is first treated with the latex stage polymer and only after addition of the polymer is added the addition of dienophile.

The advantage of the synergistic composition according to the invention is, on the one hand, a reduction in the total content of the stabilizing components and, on the other hand, in most cases also a reduction in the stabilizing system while maintaining or increasing the stabilizing effect. The first of these is particularly relevant for food contact materials where the total content of non-polymeric ingredients is limited and for materials where heat resistance plays an important role.

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

Example 1

The following additives (in parts by weight per 100 parts by weight of polymer) were added to the latex of styrene-acrylonitrile copolymers (70:30 by weight) prepared by emulsion copolymerization to 98% conversion and vacuum distillation of residual monomers whose dry matter was 35%: experiment number 123456789 di (2-ethylhexyl maleate) 1,0 0,9 0,8 0,7 0,5 0,3 0,1 0 O dilauryl thiodipropionate 0 0,1 0,2 0,3 0,5 0,7 0,9 1 , 0 0

Both additives were dosed to the latex as emulsions of their 10% solutions in toluene with po3

214 344 by water: oil phase 2: 1. Sodium dodecylbenzenesulfonate in an amount of 0.3% was used as emulsifier. The mixed latexes with the above additions were dried on a Petri dish (30 min / 120 ° C) and transferred to an oven, thermostated at 200 ° C.

After 10 minutes of heating at 200 ° C, the melts of samples 4, 5, 6 were pale yellow, 1, 2, 3,

7, 8 yellow, 9 yellow-brown. After 30 minutes at 200 ° C, samples 5, 6 were slightly yellow, samples 1, 2, 3, 4, 7, 8 were tan, 9 brown. After 40 minutes at 200 ° C, sample # 6 was faintly yellow, yellow, 1, 2, 3, 4, 7, 8 yellow-brown, 9 brown. From the results, there is an apparent synergistic effect of the two substances used, i.e. their mixture shows a higher efficiency than the same amount of either of its two components.

Example 2

The following additives (parts by weight per 100 parts by weight of polymer) were added to the latex used to prepare samples 1-8:

No. of sample 10 11 12 13 14 15 Dec 16 17 18 sodium formaldehyde sulfoxylate 0 0.2 0.6 0.35 0.30 - - 0.1 0.3 die thylhydroxylamine - - 0.03 - 0.05 - - - 0.02 dibutyl maleate - - - - - 2,0 1.0 1.0 1.0

Both reducing agents were dosed into the latex in the form of 5% aqueous solutions, the dienophile in the form of an aqueous emulsion of 10% toluene solution similar to Example 1. The individual latexes with the mentioned additives were coagulated after 0.8 hours with 0.8% aqueous CaCl 3 solution. was filtered, washed with distilled water in a standard manner (300 ml / 10 g of polymer) and dried at 120 ° C. The dried powder was transferred to a 200 ° C oven on petri dishes and the progress of coloring was monitored. After 10 minutes at 200 ° C, the samples were 10, 11, 12, 13, 14 brown, 16 dark yellow, 15 and 18 yellow, 17 light yellow. After 20'min at 200 ° C, the samples were 10-14 dark brown, 16 brown, 15 and 18 yellow-brown, 17 yellow. As in Example 1, the strongest staining retardation was observed in the combination of dienophile with reducing agents.

In contrast to Example 1, in which both components of the synergistic mixture remained in the polymer, however, most of the reducing agents used in Example 2 were washed out of the polymers during the polymer recovery. This example illustrates the possibility of time delay in the action of both synergistic components.

Example 3

The following additives (parts by weight per 100 parts by weight of polymer) were added to the latex used in the previous Examples 1 and 2.

Sample No. 19 20 21 22 Mono-octyl maleate - 6.5 3.25 Beta-tert-dodecyl-mercaptopropionitrile 1.94 - 0.97

Dienophile was dosed directly into the latex, without dilution, with the reducing component in the form of an emulsion of its solution in toluene similar to the dienophile in Examples 1 and 2. After 10 minutes of heating the dried melt at 200 ° C, sample 22 was tan, samples 19 and 20 yellow. and sample 21 light yellow.

Example 4

The following additives (parts by weight per 100 parts by weight of polymer) were added to the latex used in the previous examples: Sample No. 23 24 25 26 27 Di (ethylhexyl) maleate 0 0.2 0.5 0.7 1.0 tris - (monylphenyl) phosphite 1.0 1.8 0.5 0.3 0

Both components were dosed as emulsions of their toluene solution as a dienophil in Example 1. After 10 minutes heating at 200 ° C, samples were 23 to 27 yellow, after 20 minutes / / 200 ° C, samples were 25, 26, 27 yellow-brown and 23, 24 dark brown, after 40 minutes / 200 ° C, samples 25, 26 were yellow-brown and samples 23, 24, 27 were dark yellow-brown.

Example 5

To the ABS copolymer latex containing 13 weight% polybutadiene component and 87 weight% styrene-acrylonitrile component with a 70/30 styrene / acrylonitrile ratio, the following emulsion components were added as in Example 1 (parts by weight per 100 parts by weight of polymer) «

Sample No. 28 29 30 31 Di- (2-ethylhexyl) maleate 0.85 0.42 - Dilauryl thiodipropionate - 0.49 0.98

After 30 minutes / 120 ° C, samples 28 and 29 were white, 30 and 31 yellowish. After 10 minutes / 180 ° C, sample # 29 was slightly yellowish, samples 28 and 30 were yellow and 31 were tan. After 10 minutes at 200 ° C, sample # 29 was light brown, samples 28 and 30 were brown, and sample 31 was dark brown.

Example 6

The following additives (parts by weight per 100 parts by weight of polymer) were added to the styrene-alfamethylstyrene, acrylonitrile, butadiene powder copolymer containing 14% by weight polybutadiene component, 26% by weight bound acrylomitrile and 12% by weight bound alpha-methylstyrene:

Sample No. 32 33 34 Di (2-ethylhexyl) maleate 1,0 - 0,5 Tris-nomylphenyl phosphite - 1,0 0,5

The powder was melted in a standard manner and the melt extruded at 200 ° C on a laboratory extruder. The obtained granulate from sample no. 34 was pure white, yellowish from samples no. 32 and 44 ·

Claims (1)

SUBJECT OF THE INVENTION A synergistic blend for enhancing the color stability of acrylonitrile polymers, characterized in that it consists of a dienophile, preferably dioctyl maleate, and a reducing agent, preferably dilauryltiodipropionate, or trisnonylphenylphosphite, or beta-tert-dodecylmercaptopropionitrile, having a weight ratio of 90: 10 : 90.