CS219440B1 - A method for producing an ABS resin type polymer - Google Patents

Abstract

A method of producing ABS polymer by emulsion polymerization of dinyl monomers in the presence of elastomer latex, in which, in order to increase the resulting gloss of the polymer, 30 to 65% of elastomer latex is dosed at the beginning of polymerization and the remaining 70 to 35% of elastomer latex after 30 to 70% of the monomer has been polymerized.

Description

The invention relates to the production of polymers of the ABS resin type by emulsion polymerization.

ABS copolymers are usually mixtures of 5 to 50% by weight of elastomeric polybutadiene, or its copolymers with styrene or acrylonitrile, with the glassy copolymer styrene acrylonitrile or* styrene-alphamethylstyrene acrylonitrile.

In a broader sense, ABS resins also include similar materials in which the bound butadiene in the elastomer is replaced by an alkyl acrylate with two to eight carbon atoms in the alkyl, or in which the acrylonitrile in the glassy component is partially or completely replaced by methyl methacrylate. These mixtures may have different morphology depending on the preparation method; part of the glassy polymer is usually chemically bound to the elastomeric polymer and most of the glassy polymer usually forms a continuous phase in which the elastomeric component is dispersed. A smaller part of the glassy polymer sometimes forms a secondary dispersion in the elastomeric particles. ABS polymers can be prepared by mechanical mixing of the elastomeric and glassy components, block or solution polymerization, emulsion polymerization, suspension polymerization, or emulsion-suspension polymerization.

An example of an emulsion process for preparing these polymers is US patent 3,624,183 or NSR 1,960,409. According to US 3,624,183, an ABS copolymer is prepared by grafting a mixture of 40 to 55 parts by weight of a mixture of styrene or alpha-methylstyrene with acrylonitrile onto 60 to 45 parts by weight of butadiene styrene copolymers containing 10% by weight of styrene, the resulting grafted copolymer being mixed with a separately prepared copolymer of 60 to 80 parts by weight of styrene or alpha-methylstyrene with 40 to 20 parts by weight of acrylonitrile. According to NSR 1,960,409, an elastomeric latex is prepared by emulsion copolymerization of butyl acrylate, acrylonitrile and a crosslinking monomer, e.g. allyl methacrylate, in the presence of 0.1 parts by weight of ammonium persulfate and 1.8 parts by weight of parts of sodium oleate per 100 parts by weight of monomers. The rubbery latex obtained is grafted with a styrene-acrylonitrile mixture and, before isolating the polymer, is mixed with a separately prepared latex of styrene-acrylonitrile copolymers.

In many practical applications of polymers such as ABS resins, it is desirable that the resulting product obtained after cooling the polymer melt exhibits high gloss. It is known that an increase in the gloss of the resulting product can be achieved by reducing the content of the elastomer component in the starting resin; however, at the same time, the toughness of the resulting material decreases. Similarly, in some cases, it is possible to increase the gloss at the expense of toughness by reducing the size of the elastomer particles or using an elastomer with an increased content of bound styrene or acrylonitrile. This deficiency of the known methods is eliminated by the process according to the invention.

According to the invention, ABS resin-type polymers are produced by emulsion polymerization of a mixture of vinyl polymers in the presence of an elastomer latex such that 30 to 65 wt. % of the elastomer used is present in the reaction mixture throughout the polymerization period, the remaining amount of elastomer is dosed into the reaction mixture between polymerizations of 30 to 70 wt. % of monomers from their total amount dosed into the reaction mixture throughout the polymerization period, the monomer mixture being dosed into the polymerization system either once or in multiple doses and the total monomer conversion at the end of polymerization is at least 90 wt. %. The monomer mixture can be preferably dosed in two doses such that the first part of the monomer mixture is dosed before the start of polymerization, the second part of the monomer mixture is dosed with the second part of the elastomer after polymerization of at least 70 wt. % of the monomers dosed in the first dose and the first dose of monomers is 30 to 70 wt. % of the total amount of monomers fed into the reaction mixture. The elastomer fed at the beginning of the polymerization may preferably be in the form of a latex with a particle size of 40 to 200 nm and the remaining elastomer fed after the polymerization of 30 to 70 wt. % of the monomer may preferably be in the form of a latex with a particle size of 200 to 600 nm.

As starting elastomeric latexes, latexes of polybutadiene and its elastomeric copolymers with styrene and acrylonitrile, which may optionally be modified by the presence of carboxyl groups bound to the polymer, are particularly useful. Provided that the elastomeric character of the polymer is maintained, butadiene may be partially or completely replaced by another diene monomer, in particular isoprene or chloroprene, or by an alkyl acrylate with two to eight carbon atoms in the alkyl.

The elastomer dosed at the beginning of the polymerization may preferably be a copolymer of butadiene with acrylonitrile with a particle size of 40 to 200 nm. Particle size in the sense of the present invention means the turbidimetrically determined value of the average diameter of the latex particles D _t (determination at a wavelength of 489 nm). The dosage of the monomer mixture can be carried out in a discontinuous or continuous manner. The composition of the monomer mixture, the initiation and emulsification systems used and the processing of the latex during polymerization do not differ from the commonly used procedures for the preparation of polymers of the ABS resin type when applying the process according to the invention.

The advantage of the process according to the invention is an increase in the achievable level of gloss of the polymer while maintaining good toughness, or an increase in toughness while maintaining the original level of gloss. In some cases, the process according to the invention also allows for an improvement in the economic parameters of the production* process.

Example 1

ABS latexes were prepared in a 151-liter polymerization kettle according to the following recipes (data in parts by weight, 1 part by weight = 25 g):

a) the following components were dosed into the reactor:

ingredient / recipe number 1 water 200 polybutadiene latex with particle size 270 nm (as dry matter) 15.0 sodium dodecylbenzenesulfonate 0.3 ethylenediaminetetraacetic acid 0.01 sodium formaldehyde sulfoxylate 0.02 styrene-acrylonitrile mixture in a weight ratio of 75/25 85 tert.dodecyhnercaptan 0.374

_{K2CO3 0.06}

200 200 6.0 6.0 0.3 0.15 0.01 0.01 0.02 0.02 85 40 0.374 0.184 0.06 0.06

All components except persulfate were dosed into the batch before starting the tempering, potassium persulfate was dosed after the batch was tempered to 343 K.

b) polymerization mode:

After 40 min of stirring at 343 K, a sample was taken from the reaction mixture prepared according to recipe no. 2 to determine the conversion and 9.0 parts by weight of the originally used polybutadiene latex (in dry matter) was dosed into the reaction mixture.

The monomer conversion at the time of dosing the second part of the polybutadiene latex was determined from the sample taken by weight with the result of 35%. After 50 min of mixing the batch (from the dosing of persulfate), 0.5 wt. part of potassium stearate and 5.5 wt. parts of water were dosed in all recipes, in recipe no. 3 a sample was taken to determine the monomer conversion and dosed 9.0 wt. parts of the originally used polybutadiene latex of recipe 1, 45 wt. parts of the used styrene-acrylonitrile mixture and 0.207 wt. parts of tert.dodecyl mercaptan.

The analysis of the sample taken determined the conversion of the first batch of monomers to be 87%. After 100 min of tempering at 343 K (from the addition of persulfate), an additional 0.9 wt. parts of potassium stearate and 10 wt. parts of water were added to all formulations. After 160 min of polymerization, 0.06 wt. parts of sodium formaldehyde sulfoxylate and 0.1 wt. parts of diethylhydroxyamine were added to all formulations and the conversion was determined to be 97, 96 and 97% (for formulations 1 to 3).

The latexes were filtered through a silicone mesh, vacuum demonomerized to remove unreacted monomers and precipitated with an aqueous solution of calcium chloride. After drying and granulation in a standard manner, the following physical and mechanical characteristics of the obtained polymers were determined:

3 melt flow index according to

ČSN 64 0861 (g/10 min/220 °G) 22.0 23.1 22.7 notch toughness according to CSN 64 0612 (kj/m ² ) 17.7 18.3 18.8 gloss according to ISO 2813 at an angle impact 22.5° (°/o) 42 49 51

By comparing the results obtained for recipes 2 and 3, which correspond to the process according to the invention, with the results obtained for recipe no. 1, which corresponds to the known method, it is evident that the gloss level is increased while maintaining the original values of fluidity and toughness of the polymer.

Example 2

On the same equipment as in Example 1, latexes of ABS resin polymers were prepared according to the following recipe (data given in parts by weight, 1 part by weight = 25 g)

a) the following components were dosed into the reactor:

ingredient and recipe no. 4 5 6 water 200 200 200 butadiene-acrylonitrile copolymer latex with 10 wt. % bound- of acrylonitrile in polymer and with a particle size of 326 nm (as dry matter) latex of copolymers of butadiene-acrylonitrile with 10 wt. % bound acrylonitrile in the polymer and a particle size of 110 nm 4.5 (as dry matter) latex copolymers butadiene-butyl acrylate with 15 wt. % bound acrylate and particle size 580 nm (as dry matter) mixture of styrene acrylonitrile in 5.5 5.5 4.0 mass ratio 74/26 38 38 38 tert.dodecyl mercaptan 0.180 0.186 0.210 khco ₃ 0.2 0.2 0.2 sodium dodecylbenzenesulfonate 0.3 0.3 0.5

b) the reaction mixture was heated to 343 K. At this temperature, 0.2 parts by weight of K ₂ S ₂ 'O8 was added to all formulations. After 90 min of polymerization, 0.5 parts by weight of sodium dodecylbenzenesulfonate was added to all reaction mixtures. After 110 min, 4.5 and 5.5 parts by weight of latex (in dry matter) of butadiene acrylonitrile copolymers with a particle size of 326 nm, which was used previously in formulation no. 4, and 47 parts by weight of monomer mixture styrene-acrylonitrile-tert.dodecyl mercaptan in a weight ratio of 64/26/0.49, were added to formulations 5 and 6.

After 220 min of polymerization, 0.05 parts by weight of diethylhydroxylamine and 0.05 parts by weight of sodium formaldehyde sulfoxylate were added to the batch. By determining the content of free monomers, a conversion of over 97% was found in all cases. The following values of physical and mechanical characteristics were found for the polymers obtained by precipitation of demonomerized latexes with an aqueous solution of CaCl ₂ after their processing in a standard manner.

recipe no. melt flow index according to

CSN 64 0861 (g/10 min/220 °C) 18.8 17.2 17.7 notch toughness according to ČSN 64 0612 (kj/m ² ) 22.4 23.2 21.6 gloss according to ISO 2813 at an angle impact 22.5° (%) 45 58 54

Comparing the values for recipes 5 and 6, which correspond to the process according to the invention, with the values for the polymer prepared according to recipe no. 4, which does not correspond to the process according to the invention, an increase in gloss values is again evident while maintaining toughness at practically the same level.

Claims (3)

Process for the production of an ABS resin type polymer by emulsion polymerization of a vinyl monomer mixture in the presence of a latex, an elastomer, characterized in that 30 to 65 wt. why. the elastomer used is present in the reaction mixture throughout the polymerization, the remaining amount of elastomer being metered into the reaction mixture between 30 to 70 wt. % of the total amount of monomers fed to the reaction mixture throughout the polymerization, wherein the monomer mixture is fed to the polymerization system either in single or multiple doses, and the total conversion of monomers at the end of the polymerization is at least 90% by weight. 2. The process of claim 1 wherein the monomer blend is dosed in two portions such that the first portion of the monomer blend is dispensed prior to the start of polymerization, the second portion of the monomer blend is dispensed with the second elastomer portion after polymerization of at least 70 wt. % of the monomers dosed in the first batch and the first monomer batch are 30 to 70 wt. % of the total amount of monomers fed to the reaction mixture. 3. The process according to claim 1, wherein the elastomer metered at the start of the polymerization is in the form of a latex having a particle size of 40 to 200 nm and the remaining elastomer metered after polymerization of 30 to 70 wt. % of monomers, is in the form of a latex with a particle size of 200 to 600 nm.