CS210100B1 - Method of demonomerization of the synthetic polymeres latexes - Google Patents

Description

The invention relates to a process for the demonstration of latexes of synthetic polymers whose glass transition temperature T is greater than 50 ° C. Such polymers include, for example, polystyrene.

high-styrene resins, ethylene-arylooitrile copolymers, arylooitrile-butadiene-styrene (ABS) graft polymers, or. graft copolymers of methyl-methyl-atyreenautyl aarylate>

In the manufacture of latexes of these polymers, it is often necessary or desirable to lead the emulsion only to a certain conversion for various reasons. Unreacted mono- or other volatile substances are then removed from the latex by decetation.

Known methods - demenomeeizaoe synthetic latexes discontinuous. or continuous de-steaming with water vapor, optionally in the presence of an inert gas, as described in GDR Pat. 191 363.

According to GB 1 090 976, OLatex is formulated as droplets with water vapor which condenses on these droplets. According to VB 1 205 776, the efficiency of the process is improved by demonstrating an isolation system in which Oatex is mixed with a rapidly flowing gas, for example water vapor, so that a large liquid-gas phase interface results from turbulent mixing.

In all the procedures described, the temperature dependence and velocity characteristics remain. demooomeeizloe practically without substantial changes. While in low temperature T ₀ ellttometer latexes, the dossi temperature can be selected in a wide range without demonstrating

Consequences on the rate of latex demonstration, in latexes with higher glass transition temperature T

O is manifested when the temperature drops below the temperature at demeoorerizaai T _{g of} the polymer popsatné zpomelení process. In practice, therefore, an acceptable compromise must be sought between the kinetics of the process and the undesirable consequences of higher working temperatures at demernal-aggressive conditions, which are generally - for example, faster polymer aging during the process .

According to the invention, the demonstration of latexes of synthetic polymers having a glass transition temperature T greater than 50 ° C is carried out with water vapor or an inert gas so that, before the start of the process, the demonstration process is performed. or during the addition of 0.5 to 10% of the softener to the latex, based on the moisture content of the latex. The softener can be added to the latex in the form of a water emulsion. At the same time, it is possible to dispense with the plasticizer some or all of the polymerization of the polymers prior to aging.

As used herein, a plasticizer is a material which is liquid at the temperature of the demonstration and is miscible with the polymer of the latex at that temperature to the extent that its entire added mono-polymer can be mixed. Thus, it is a polymer in the conventional tlml of this term, such as dibuyl, trichloroethyl, propylene glycol stearate. oil, toluene or ethylene. Softener is a common lditivee that is added to polymers. In most cases this happens only at the end of the process, i.e. the plasticizer is added to the insulated polymer. In the softening process, the anticipated laeex intent after the demonstration was performed.

The actual arrangement demonomerizace process is not critical for application of the invention Practices can be applied to both continuous and batch process during which _t may к concentrating and diluting the resulting latex ·

An advantage of the process according to the invention over the known processes is to increase the rate of demonomerization at a constant temperature, or to lower the temperature at demonomerization while maintaining its rate. In both cases, energy savings can be achieved by applying the process of the invention. The shortening of the demonomerization process has a positive effect on the productivity of the equipment and reduces the aging range of the polymer during the process.

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

Example 1

Polystyrene latex with an average particle size (determined turbidimetrically) of > 246 nm and a starting free styrene content of 5% by weight, based on the polymer + monomer sum, for 60 min at 73 ° C in a 20 L stripping reactor. 24.1% of the reactor inlet temperature was 95 ° C, the reactor steam injection rate was 1.3 kg / h, ie 0.16 kg steam / kg latex / hour, the demonomerized latex stirring rate was 54 rpm. After 60 minutes of monomerization, a free styrene content of 2.0% based on the polymer + monomer sum was found. The latex dry matter remained unchanged.

. Example 2

Stripping was carried out with the same latex under the same conditions as in Example 1, but an emulsion of 9 parts by weight of butyl stearate, 1 part by weight of 2,6-di-tert-butyl-4-methylphenol, was mixed into the starting latex for 15 min before starting the stripping. 3 parts by weight of sodium dodecylbenzenesulfonate and 10 parts by weight of water per 100 parts of polymer. After 60 minutes of demonomerization, the free styrene content of the latex was found to be 1.1%, based on the sum of polymer and styrene weights. · '

Example 3

In the same stripper as in Example 1, ABS latex containing 85% styrene acrylonitrile copolymer, 15% polybutadiene, with a starting solids of 27.2% at 26.6 kPa and a steam feed rate of 1.3 kg / hr was stripped. In 60 min stripping, the styrene content was reduced from a starting 4.6% by weight to 1.41% by weight, based on the polymer + monomer sum. · On reproduction of the experiment in the presence of two parts by weight of butyl stearate and 1 part by weight of propylene glycol tetraearate in the form of a 50% aqueous emulsion with 0.5% sodium oleate, after 60 minutes of stripping, only 1.1% of free styrene was found in the latex, based on the polymer + monomer sum.

Example 4

In the stripping apparatus described in Example 1, the latex was demonomerized under vacuum, the polymer of which contained 50 parts by weight of butadiene-butyl acrylate copolymer and 50 parts by weight.

parts of polymethyl methacrylate. Initial latex of latex latex 30% and starting content of methylmethyarylate of latex 10% based on the sum of polymer and methylmastarylate masses · Latex tulle mixed with a 10: 1 vapor / nitrogen mixture at 80 ° C for 30 - Mn then an emulsion of 3 parts by weight of dibutyl phthalate and 2 parts by weight of ethylbenzene in 5 parts by weight of water was admixed to the latex. After a total crushing time of 60 Mn - 2.5% monomeric MM1 was found in the latex. otherwise, the MMA content was found in a similar experiment. 3.2%.

By comparing the results given in Examples 1 to 4, it is apparent that the process is substantially accelerated to the latex flow rate of the plasticizer.

Claims (3)

CLAIMS 1. Process for deo isolation of latexes of synthetic polymers having a glass transition temperature Tg is greater than 50 ° C, with steam or mixtures thereof with an inert gas, characterized in that - before or during the deootomination process, 0.5-10% of the mono-olefinic vapors are added to the latex. ^ k ^ c ^ \ ^ e ^ c ^ d in terms of polymer latex count · 2. A process according to claim 1, wherein the mixture is added in the form of aqueous erosion. Method according to claim 1 or 2, characterized in that part or all of the polymer stabilizer is dosed in the plasticizer for aging.