DD240550A1 - METHOD FOR POLYMERIZING VINYL CHLORIDE - Google Patents

Abstract

The invention relates to a process for the polymerization of vinyl chloride by suspension polymerization, optionally in admixture with other copolymerizable monomers using known Wasserloeslicher dispersants such as cellulose ethers and partially saponified polyvinyl acetates and by known monomersloeslicher initiators by the polymerization of 0.005 to 0.5 percent by weight gesaettigte based on the monomers and / or partially unsaturated polyethylene oxide carboxylic acid esters or mixtures in which the chain length of the carboxylic acids is between 8 and 30 carbon atoms, the degree of ethoxylation is adjusted to values of 2 to 8 and the HLB value to 6.5 to 9.5 , The resulting polymers have a narrow particle size distribution rapid and uniform Weichmacheraufnahmefaehefigkeit and despite high Porositaet due to their optimum particle shape even at high K value settings on a relatively high Schuettdichte so that they allow in an economically advantageous way processing into high-quality, low-spine products ,

Description

Field of application of the invention

The invention relates to a process for the preparation of free-flowing vinyl chloride polymers having average molecular weights M _n between 22500 and 32500 corresponding to Fikentscher K values between 50 and 58 by polymerization of vinyl chloride (VC) or predominantly VC-containing monomer mixtures using known polymerization aids, such as cellulose ethers and / or partially saponified polyvinyl acetates as suspension stabilizers, fatty acid esters as emulsifiers, monomer-soluble peroxidic and / or diazo compounds as initiators and an alkyl aldehyde as chain regulator, in the temperature range between 340 and 350 K.

Characteristic of the known technical solutions

For the preparation of low calorie transparent calender films and thin-walled injection molded articles, VC polymers having molecular weights M _n below 35,000, in particular those having Fikentscher K values between 50 and 60, which are usually produced by suspension polymerization processes, are required.

In many cases, as monomer-soluble initiators diacyl peroxides and / or peroxydicarbonates, and also diazo compounds (DE 2225236, 2139680,2644202), as suspension stabilizers cellulose ethers and / or partially saponified polyvinyl acetates, which are often combined with special fatty acid ester emulsifiers (DE 170328.1946348 , 2209592, 2234038, 2653087), and also various chain-transferring substances with which the average polymer molecular weight is "down-regulated" in a targeted manner (designation as chain regulator) (Schulz, GV, et al., Z. physik., Chem. B43 [1939], 182), The range of chain regulators comprises a large number of substance classes, of which in particular thio compounds (DE 2,640,887, US 4,052,548), halogenated hydrocarbons (Stanaback, RJ, SPE 35th ANTEC Conference, Montreal, April 1977) as well as ketones and aldehydes (Thümmler , W., et al., Plastics and Rubber 30 [1983] 12,661) have gained practical importance, but while the mercaptans, halocarbons Hydrogens and -olefins due to their mostly carcinogenic and strong retarding effect or very uneven control effect, which leads to unreasonably wide molecular weight distributions in the resulting VC polymers and their unsatisfactory Thermostabiütät are very limited in their usefulness, are particularly satisfactory with aldehydes in terms of molecular weight control Results achieved. The use of aldehydes having at least 4 carbon atoms in a concentration of less than V3 of the saturation concentration in water, such as especially n-butanol (DD 125409), also in combination with cyclic 1,3-diethers (DD 131176), isobutanol (US Pat 2729627).

In contrast to the C ₄ -aldehydes, which can not be used without restrictions because of their unpleasant odor and thereby very low MAK values for use, especially when using higher regulator concentrations for products with K values <55, complex technical and technological Require measures, this disadvantage by use of C ₆ - to C-ie aldehydes (from 2-ethylbutanol to octadecanal) turned off (DE 2840334). The polymerization rates achieved and space-time yields are considerably lower in comparison to the aldehyde-free polymerization, since the generally used between 0.5 and 1.0%, based on the monomer composition ' -

Aldehydmengen have a relatively strong retarding effect. On the other hand, the regulator effect (molecular weight reduction or K-value reduction) - same weight - better molecular weight concentrations provided - the higher C ₆ - / C ₁₈ aldehydes over the lower C ₂ - / C5 aldehydes and trichlorethylene, the latter as a type of standard regulator , not or only slightly improved.

A possible technical use is the low cost of the known process according to DE 2840334 due to the compared to the regulator-free polymerization and otherwise the same polymerization and under analogous reaction conditions (same technology, same pressure-temperature regime) considerable extension of the polymerization - generally on the Three to four times - contrary.

Object of the invention

The object of the invention is to provide easily flowing VC polymers having Fikentscher K values between 50 and 58 as well as physiological safety and satisfactory thermostability by means of known, without affecting the

Reaction speed running suspension polymerization, which are particularly suitable for processing into transparent calender films of low strength and / or thin-walled injection molded products.

Explanation of the essence of the invention

- The technical task

It is an object of the invention to provide a process for the preparation of free-flowing VC polymers having average molecular weights M _n between 22500 and 32500, ie Fikentscher K values between 50 and 58, by polymerizing VC or predominantly VC-containing monomer mixtures using known polymerization auxiliaries, as cellulose ethers and / or partially saponified polyvinyl acetates as suspension stabilizers, fatty acid esters as emulsifiers, monomer-soluble peroxidic and / or diazo compounds as initiators and an alkyl aldehyde as a chain regulator to develop in the temperature range between 340 and 350K.

Features of the invention

The object is achieved according to the invention by using as aldehyde 2-ethylhexanal (EHA), optionally as a mixture with 2-ethylhexanol (EHO) in a composition of 99-50% EHA and 1-50% EHO in a concentration between 0.05 and 0 , 5Ma .-% EHA, based on the monomer composition, is used.

EHA / EHO mixtures are advantageous, on the one hand due to the chain-transferring intrinsic action of EHO with regard to M _n reduction and, on the other hand, due to the favorable influence of monomer EHO and its influence with respect to thermal stability increase of the PVC.

Within the polymerization temperature range from 340 to 350K, using EHA concentrations below 0.5% based on the monomer composition, while ensuring reaction rates or space-time yields, as achieved by means of regulator-free polymerization under conventional suspension polymerization conditions, VC polymers with a correspondingly 4-8 K value units lower average molecular weight and thus a high flowability (melt indexes MFI, 463/212 N,> 5g / 10mm) and sufficient thermal stability (stabilimeter method or other determination method according to TGL 28475/02).

embodiment

In a VC slurry polymerization autoclave equipped with an impeller agitator, a polymerization batch consisting of

10000 parts by mass (MT) of water,

2.0M hydroxypropyl methylcellulose (HPMC) with a cloud point of 341K (0.2% solution

having a viscosity of 1.774 mPa s at 293 K) - HPMC1,

2.0MT HPMC with a cloud point of 337 K (1.322 mPa-s) HPMC2,

4.0 MT partially saponified polyvinyl acetate with 28% by weight residual acetate content (viscosity of the 4% solution at 293 K)

from 4mPa-s) -PVA1,

3.0 MT sorbitan monolaurate (SML),

4.0 M sodium bicarbonate (NaHCO ₃ ) and

20.0MT 2-ethylhexanal (EHA),

submitted. After the reactor has been purged with oxygen by nitrogen, the initiator mixture

- 1.0 MT diisopropyl peroxydicarbonate (DIPP) and 2.5 MT dilauroyl peroxide (DLPO) - as well as total

7000MTVC

and heated to a reaction temperature (T _Pm ) of 343K. Keeping constant T _Pm , the polymerization is conducted with stirring over a period of 4.5 hours to a final VC conversion of 87%. After expansion of the reactor, the PVC is obtained from the suspension by known work-up technology, including VC residual monomer separation and recovery, with the following characteristics (test PVC powder according to TGIr 28475/02:

Fikentscher K-WeH (TGL 37166) 52.7

Bulk density (TGL 14074) 0.56 g / cm ³

Softener pick-up speed 10 min

(Greasy method, TGL 28475 / size 145321) flowability (TGL 160-221.14 mm nozzle) 18 g / s grain size (wet sieving, TGL 20645)

<63 / by 3.5%> 250 ^ m 0.2%

Speckle content class I

(TGL28475 / 02) (<5 fish eyes on

100 cm ^{2 of} a rolled sheet, which after 5 min. produced at 383 K)

Melt Index MFI (TGL25244; 5.5 g / 10 min.

463 K and 49 N edition)

Thermostability TS (stabilimeter method: 42 min.

10 min. Rolling at 453 K, usual stabilization by means of 2% tin compound)

Under variation of the polymerization conditions (T _Pm , _{duration of} polymerization) and in particular the formulation (dispersing system HPMC / PVA / emulsifier, initiator system, EHA concentration, EHA / EHO ratio and possible vinyl acetate fraction as comonomer), the examples listed in Table 1 are the application ranges of the procedure

to document.

In Examples Nos. 4 to 7 2MT HPMC 1,1,5 MT HPMC 3 (cloud point - 335 K;

Viscosity of the 0.2% solution at 293 K - 1.56 mPa · s), 3 MT PVA 2 (26% by mass residual acetate content;

Viscosity of a 4% solution at 293 K - 6.5 mPa · s) and 7 MT PVA 3 (34.5 wt% residual acetate content;

Density of a 25% solution at 293 K - 0.91 g / cm ³ ), in No.4, 8, 8 and 10 as an initiator combination

1.0MT dicetyl peroxydicarbonate (DCP) and 2.0MT DLPO, and nos. 9 and 10

10% by weight of vinyl acetate (VAC), based on the total monomer mass (VC plus VAC). As comparative experiments, the polymerization conditions used under No. 1 in Table 1 are selected with the following differences:

1 A - no EHA additive (also no other chain regulator used), 1 B - 11.2 MT butyraldehyde (BAI) added instead of 20.0 MT EHA (corresponds to approximately equal molar amounts of approx.

0.025 moles of aldehyde per liter of VC),

1 C - 20 MT 2-ethylhexanol (EHO) without EHA addition (about the same molar amount as 20 MT EHA),

1 D - 21 MT trichlorethylene (about 0.025 moles TCE per I VC).

Table 1

polymerization

PVC characteristics ^2>

EHA

EHO

tpm

(K)

Pm time ¹ '(h)

K-WertMFI

49 N 463 K (8/10 min.)

212N

TS (min.)

1 0.3 - 343 4.5 52.7 5.5 4.2 42 1A - - 4.2 58.3 8.3 56 1B 0,16BAI - 4.5 56.8 5.6 46 1C - 0.3 4.2 57.4 56 10 0,3TCE - 6.2 55.4 2.1 38 2 0.2 - 345 4.2 53.9 4.2 43 3 0.48 - 342 5.0 51.5 7.2 33 4 0.15 - 343 4.2 54.7 3.5 46 CJL 0.3 - 345 4.2 52.3 6.3 39 6 0.3 0.05 343 4.5 53.2 5.1 44 7 0.2 0.1 345 4.2 54.4 3.9 48 8th 0.48 0.1 341 4.8 51.3 8.3 39 9 0.15 - 342 4.5 55.8 6.5 55 10 0.3 - 344 4.5 52.9 10.8 46

1) Achieving a minimum VC turnover of 85%

Claims (1)

Invention claim: Process for the preparation of readily flowing vinyl chloride polymers having average molecular weights M _n between 22500 and 32500 corresponding Fikentscher K values between 50 and 58 by polymerization of vinyl chloride or predominantly vinyl chloride-containing monomer mixtures using known polymerization aids, such as cellulose ethers and / or partially saponified polyvinyl acetates as suspension stabilizers, fatty acid esters as Emulsifiers, monomer-soluble peroxidic and / or diazo compounds as initiators and an alkyl aldehyde chain regulator, in the temperature range between 340 and 350K, characterized in that as aldehyde 2-ethylhexanal (EHA), optionally as a mixture with 2-ethylhexanol (EHO) in a composition of 99-50% EHA and 1-50% EHO, in a concentration between 0.05 and 0.5 Ma .-% EHA, based on the monomer composition, is used.