DD256138A1 - PROCESS FOR PREPARING POLYMERS OF VINYL CHLORIDE - Google Patents

Abstract

The invention relates to a process for the preparation of polyvinyl chloride with high Schuettdichte and good Porositaet with reduced formation of Wandansaetzen by the suspension process. The process is designed such that polysiloxane-polyoxyalkylene block copolymers are used as suspension stabilizers and in that the polymerization batch contains from 0.0001 to 0.01% by weight, based on the aqueous phase, of a mixture of water and oeleal inhibitors in a ratio of 1: 0.1 to 1: 5 are added. Shed densities of greater than 600 g / l are achieved.

Description

-2 - Ζ56Ί38

Field of application of the invention

The invention relates to a process for the preparation of polymers of vinyl chloride by free-radical polymerization of vinyl chloride and predominantly vinyl chloride-containing Mohomermusungen by the suspension process.

Characteristic of the known technical solutions

The suspension polymerization of vinyl chloride or the preparation of copolymers based on vinyl chlorides is carried out on an industrial scale in the presence of dispersants for the preparation and stabilization of the vinyl chloride / polyvinyl chloride suspension in the aqueous phase. It determines u.a. the property profile of the dispersant system, the distribution of the monomer in the aqueous phase, the morphology of the PVC grain, in particular its porosity, the particle size distribution, or the thermal stability of the polymer. For the processing of the polyvinyl chloride, particularly the bulk density and the plasticizer capacity are of crucial importance. However, both properties are related so that, generally, one size deterioration occurs in the improvement of one size.

As dispersants u.a. Cellulose ethers, as described in DE-OS 2412014, in question. Furthermore, cellulose ethers are mixed with partially hydrolyzed polyvinyl acetate (DD-PS 145539) or polyvinyl acetate (DE-AS 1142238), optionally in combination with nonionic emulsifiers (DE-OS 2945073). To achieve high porosities, additional aliphatic or aromatic hydrocarbons or alcohols are used (US Pat. No. 2875186),

It is also known, by adding long-chain fatty acids or their esters or by adding ionic or nonionic surfactants, often combined with other additives, such as reducing agent to the polymerization to increase the plasticizer receptivity (DE-OS 2385134,2151703, DE-PS 1 545 179, DE-OS 2244805.2134804).

Also described is the combination of suspension stabilizers for influencing the plasticizer receptivity (US Pat. No. 3,879,365, DE-AS 1720328, DE-OS2209592).

A polyvinyl chloride having a high bulk density, low porosity and a relatively broad particle size distribution is obtained when using styrene / maleic anhydride copolymers as a dispersant (DD-PS 13583.14358).

Furthermore, a polyvinyl chloride having a relatively high bulk density and a good porosity by addition of diallyl or triallyl compounds to the commonly used dispersants or their mixtures (DD-PS 151455).

An increase in bulk density is obtained by addition of organic or inorganic nitrites (DE-OS 1 948 358).

The known methods have the disadvantage that they affect only one size positively and the others are neglected, i. With a high bulk density, one obtains low porosities or vice versa.

Due to the large number of additives is often a deterioration of other product properties, such as. a. Take the thermal stability into account.

Object of the invention

The aim of the invention is to produce polyvinyl chloride with high bulk density and good porosity by the suspension process with reduced formation of wall deposits.

Explanation of the essence of the invention

- The technical problem which is solved by the invention

The invention has for its object to develop a process for suspension polymerization of vinyl chloride or predominantly vinyl chloride-containing monomer mixtures with reduced formation of wall deposits, which allows, in the presence of known radical-forming initiators or initiator systems to produce polymers which in addition to an increased bulk density have sufficient porosity.

Features of the invention

The object is achieved in that the suspension stabilizers polysiloxane-polyoxyalkylene block copolymers of the general formulas

RASiO / SiR¹OV / SiRAO / "- SiRAj I ffl ·d.η j) (D.

/ SiR ¹ OV _m 9 (in

G or

/ SiR "

_{n / 2} /

in which mean:

R '- identical or different lower, optionally substituted alkyl radicals; preferably methyl groups m - integer fractional numbers between 1 and 12, preferably between 2 and 5 η - integers or fractions between 30 and 250, preferably between 40 and 120 G - polyoxyalkylene glycol acetate. ole-j-alkoxylate, cyanoalkoxylate or ureate radical of the general formula - [CH ₂ I ₃ - [OCH ₂ CH ₂ ] P- [OCH ₂ CH (CH ₃ ) Iq-R '

R 'is -OCOCH ₃ , -OH, -OCH ₃ , -OC ₄ H ₉ , -OCh ₂ -CH ₂ -CN ₁ -OCONHR ", R" is alkyl or aryl radical

p, q whole or fractional numbers between 4 and 50

in concentrations between 0.001 to 0.3 wt .-% based on the aqueous phase are used and by the polymerization of 0.0001 to 0.01 wt .-% based on the aqueous phase of a mixture of water and monomer-soluble inhibitors in a ratio from 1: 0.1 to 1: 5.

As inhibitors z. As alkali nitrite, alkali metal hydrogen sulfite, alkali metal hydrogen phosphite, a-methyl styrene, a-methyl-3,4-dichlorostyrene or 2,6-di-t-butyl-p-cresol can be used.

embodiments Example 1 to 3

An oxygen-free rinse autoclave was charged with 400 parts of water, 200 parts of vinyl chloride, 0.15 parts of lauroyl peroxide, 0.1 parts of dicetyl peroxydicarbonate and 0.05 wt .-% based on the aqueous phase of polysiloxane-polyoxyalkylene block copolymers and Table 1 contained Amounts of inhibitors. Polymerization was at 63 ° C.

Example 4 to 5

An oxygen-free rinse autoclave was charged with 400 parts of water, 200 parts of vinyl chloride, 0.25 parts of dicetyl peroxydicarbonate, 0.15 parts of lauroyl peroxide and 0.05 wt .-% based on the aqueous phase of polysiloxane-Pölyoxyalkylen block copolymers and Table 1 contained Amounts of inhibitors. Polymerization was at 58 ° C.

Table 1 - concentration bulk centrifuge av. distri K-We rt Peel Example inhibitor sodium nitrite Wt .-% rel. on mass softener Grain- lungs- proportion of 2,6-di-t-butyl-p- aq. phase g / i to% by- width G cresol messerfim F sodium nitrite - 612 22.2 161 1.49 62.5 62.0 1 2,6-di-t-butyl-p 0.001 640, 19.3 167 1.48 62.3 9.1 2 cresol - 0,002 sodium nitrite 0,002 628 19.8 158 1.48 62.9 16.4 3 2,6-di-t-butyl-p- cresol 0.001 - 573 27.4 131 1.72 67.9 65.2 4 0.001 598 26.2 139 1.70 67.6 10.1 5 0,002 - mean grain diameter of the Gaussian distribution c - - Distribution width calculated according to: F - Gdg5 - grain diameter d - G - - Sum weight of the sieve fraction

Claims (1)

1. A process for the preparation of polymers of vinyl chloride by radical polymerization of vinyl chloride and predominantly vinyl chloride-containing monomer mixtures in the presence of known radical-forming initiators or initiator systems by the suspension process, characterized in that as suspension stabilizers polysiloxane-polyoxyalkylene block copolymers of the general formulas Rj ₁ SiO / SiR'07 _m / SiR ^ O J _n - SiRJ
G / SiRto_ / _m / SiR ^ O y _{n / 2} - SiR £ G ⁰ (ID / SiRi, J RJSiO / SiR 10 V _{m / 3} / SiBJO V _{a / 2} / SiR · 0
0 G Sirj in which mean: R '- identical or different lower, optionally substituted alkyl radicals; preferably methyl groups m - integers or fractions between 1 and 12, preferably between 2 and 5
η - integers or fractions between 30 and 250, preferably between 40 and 120
G - polyoxyalkylene glycol acetate ole ^ alkoxylate, cyanalkoxylat- or ureate residue of general formula - [CH ₂ ] ₃ - [OCH ₂ CH ₂ ] _p - [OCH ₂ CH (CH ₃ )] _q -R ' R '-OCOCH 2 -OH ₇ -OCH ₃₇ -OC ₄ H ₉₇ -OCH ₂ -Ch ₂ -CN ₁ -OCONHR ", R "is alkyl or aryl radical p, q whole or fractional numbers between 4 and 50 in concentrations between 0.001 to 0.3 wt .-% based on the aqueous phase are used, wherein the polymerization mixture 0.0001 to 0.01 wt .-% based on the aqueous phase of a mixture of water and monomer-soluble inhibitors in a ratio from 1: 0.1 to 1: 5.
2. The method according to item 1, characterized in that as inhibitors, inter alia Alkalinalitrit, Alkali hydrogen sulfite, alkali hydrogen phosphite, α-methyl styrene, α-methyl-3,4-dichlorostyrene or 2,6-di-tert-butyl-p-cresol can be used.