DE2315039A1 - METHOD OF EMULSION COPOLYMERIZATION - Google Patents

Description

"Process for Enru-lsionscopol ^ / merisation "

The invention relates to a batch process for the emulsion copolymerization of (A) an ester of the general J formula containing hydroxyl groups:

RC (O) -Q-CH ₂ -CH (OH) -CHp-OC (O) -E ¹ ,

wherein R represents an α, β-ethylenically unsaturated group and R ^{1 represents} a group free of ethylenic unsaturation, with (B) at least one other ethylenically unsaturated monomer. Such a method is known, for example from laid-open specification 1 951 586.

In the case of copolymerizations, the comonomers usually have

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different polymerization rates, so that inhomogeneous products with inadequate properties are obtained, unless special measures are taken. So the inhomogeneity can be reduced when looking at the reaction stops before complete conversion, e.g. at 60% conversion, but this is generally natural not recommended. According to another method, the more active monomer is added to the reaction mixture in small portions during the polymerization to (US Pat. No. 2,100,900). If you want a homogeneous product with the help of this second method reach, the addition of the more active monomer must be programmed precisely; such precise programming however, presents difficulties in practice. According to a third method, the polymerization is carried out with one batch started, which leads to the desired copolymer and during the polymerization the monomers are in one added in such a proportion that the desired composition of the copolymer is maintained.

The latter method is commonly used in continuous processes, but has also been used in batch processes Working advantages, especially when the. Addition speed for the monomers roughly corresponds to the rate at which they emerge from the copolymerization mixture are consumed. It has now been found, surprisingly, that the last described, in individual Working method to be carried out in batches by means of emulsion co-polymerization of the above monomers (A) and (B) copolymers with significantly improved properties, in particular with Better shock and impact resistance can be obtained by adding a small amount of polymerization inhibitor to the reactor before adding the monomers brings in.

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The invention relates to a process for emulsion copolymerization to be carried out in individual batches of (A) an ester containing hydroxyl groups of the formula:

RC (O) -O-CH ₂ -CH (OH) -CH ₂ -OO (O) -E ¹ ,

where E represents an a, ß-ethylenically unsaturated group and E ^{1 represents} a group free of ethylenic unsaturation, with (B) at least one other ethylenically unsaturated monomer, the comonomers and the catalyst being brought to the copolymerization temperature continuously or in individual portions during the copolymerization heated Eeaktor were abandoned, which is characterized in that at the beginning of the copolymerization in the aqueous starting phase in the Eeaktor a small amount of a polymerization inhibitor is present relative to the total amount of catalyst.

The monomers (A) and (B) polymerize in the presence of one (water-soluble) free radical catalyst, such as hydrogen peroxide, potassium persulfate, cyclohexanone peroxide, dilauroyl peroxide Eedox catalysts, such as the system of iron ions and hydrogen peroxide, can also be used. The inhibitor (or retarder) reacts with an radical to form products that can no longer absorb any monomer. * Inhibitors react so quickly with the radicals that the decomposition of the inhibitor is independent of its concentration is. The copolymerization starts when all of the inhibitor has reacted with the radicals formed. Examples suitable inhibitors are benzoquinone, hydroquinone, nitro- and mtrosobenzene, toluhydroquinone, duroquinone,

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p-Dinitrobenzene and especially 4-Hydroxyanisole.

The acyl group R-C (O) - of the monomer (A) is derived from an α, β-ethylenically unsaturated carboxylic acid, e.g. acrylic, Methacrylic, crotonic, cinnamic, maleic or fumaric acid. The α, β-unsaturated monocarboxylic acids are preferred, in particular Acrylic and methacrylic acid.

The group R'-C (O) of the monomer (A) is an acyl group, those of a saturated monocarboxylic acid, e.g. para-tert-butylbenzoic acid, Butyric acid or lauric acid. The E '~ C (O) group is preferably derived from tertiary Acids, especially those of the formula:

E ₁ -C- C (O) OH

where E ^. CH -, - is and Ep and E-, alkyl groups of 1 to each 16 carbon atoms represented. Examples of such acids are pivalic acid, α, α-dimethyldecanoic acid, α, α-dimethylhexadecanoic acid and mixtures thereof. The group R'-C (O) preferably has at least 8 carbon atoms.

Examples of suitable comonomers (B) are ethylene, styrene, Vinylidene chloride, dibutyl maleate, vinyl acetate and methyl methacrylate. Vinyl chloride is preferred. Of course, two or more comonomers of type (B) with deia hydroxyl groups can be used containing ester (A) are copolymerized.

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As already noted, the copolymerization is carried out batch-wise, the temperature in the reactor in the, generally between 310 and 375 ° £ »in particular between 330 and 360 ° K is held. Under these conditions you usually have to use pressure-tight boiler, since, for example, vinyl chloride as comonomer (B) has a pressure of developed about 6 to 23 bar. By increasing the reaction temperature and / or using a chain transfer agent, such as tetrahydrofuran, the molecular weight of the copolymer can be reduced. By adding Borax or potassium carbonate can be used to control the pH of the emulsion; he is expedient in the area between 4 · and 7j, preferably between 6 and 7.

The ester (A) containing hydroxyl groups and the comonomer (B) are preferably added in a weight ratio between 10:90 and 50:50, in particular between 20:80 and 40:60. If vinyl chloride is used as the comonomer, a copolymer in which the properties are well balanced is obtained with a weight ratio between vinyl chloride and hydroxyl group-containing ester of 65:35. The desired total ratio between the monomers QO and Φ) is expediently kept constant during the continuous or portion-wise introduction into the reactor. However, fluctuations in this ratio, provided they do not exceed + or -25%, are compatible with the method according to the invention.

The monomers (A) and (B) can be fed to the reactor separately, either as such or in emulsified or emulsifiable form. However, it is advantageous if the two monomers are used with one another in the desired ratio

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mixed, supplied, with an addition in the form of a aqueous emulsion is preferred.

The monomer charge can contain the catalyst, but this is preferably introduced into the reactor in dissolved form during the polymerization, which can be carried out either continuously or in individual portions. The amount of catalyst is usually 0.1 to 5 % of the weight of the monomer. A smaller part of this amount, ie less than 50 %, can be present in the initial aqueous phase in the reactor.

According to the invention, before the monomers are introduced, a small amount of inhibitor (small in relation to the catalyst to be introduced) is present in the initial aqueous phase in the reactor. In addition, the aqueous phase can contain emulsifiers, buffers and the like. Suitable amounts of inhibitor are in the range from 0.01 to 10 mol%, preferably between 0.1 and 5 mol%, calculated on the total amount of catalyst to be introduced. The copolymers obtainable by the process according to the invention are particularly suitable for thermosetting coating compositions. To prepare such compositions, the copolymers can be mixed with a hardening resin, for example an aldehyde condensate or a diisocyanate, or with a hardening accelerator, for example para-tololsulfonic acid or with solvents, pigments, plasticizers, fillers and the like.

The invention is explained in more detail with the aid of the examples. The monomer (A) used in the examples was prepared

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by reacting a commercial product with acrylic acid. The commercial product was the glycidyl ester of a mixture of saturated monocarboxylic acids with 9 to 11 carbon atoms in the molecule, which largely (94 %) consisted of tertiary acid. In the following, for the sake of brevity, as AOiT. The designated monomer (A) therefore essentially has the following structure:

CH ₂ = CH-C (O) -Ch ₂ -GH (OH) -OH ₂ -C (O) -E ¹ ,

wherein R ¹ -C (O) - represents the acyl radical of the mentioned saturated monocarboxylic acids having 9 to 11 carbon atoms. The hydroxyl group content of the ACE product was 300 meq / 110 g. It also contained 40 ppm of 4-hydroxyanisole.

Example 1

200 g of water, 0.6 g of K ₂ CO ₅ , 2 g of K ₂ S ₂ Og, 0.8 g of emulsifier (an alkylarylsulfonate) and 6.3 4-hydroxyanisole abandoned. The mixture was heated to 343 ° K, whereupon a monomer emulsion was pumped into the reactor over the course of 4 hours. Emulsion ¹ consisted of 260 g vinyl chloride, 140 g ACE, 24 g CCl ^, 2.4 g emulsifier and 400 g water. At the same time and also within 4 hours, a solution of 2.4 g of K ₂ CO ^ and 4 g of K ₂ S ₂ Og in 240 g of water was pumped into the reactor. The reactor was under its own pressure. After everything was added over 4 hours, the reactor contents for a further hour at 343 K ^O was stirred and then cooled to room temperature. The copolymer was precipitated by adding 20 ml of HNO ^, washed with water and with a 1% solution of NaHCO ^ to neutrality of the filtrate at 300 K under ⁰

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Vacuum dried.

The copolymer thus obtained became a paint I manufactured according to the following regulation:

Copolymer 80 g

Melamine-formaldehyde condensate (commercial product) 20 g

TiO ₂ 200 g

Dibutyl tin dimaleate 0.5 g

Maleic acid "2g

Methyl isobutyl ketone (MIBK) 390 g

The paint was sprayed on and closed at 393 ° K for 30 minutes. a film die of 30yum hardened.

Example 2 (comparative experiment)

For purposes of comparison a paint II was similarly made of a copolymer obtained as above, j ^e ci ^o ch without addition of 4-hydroxyanisole to the aqueous starting mixture in Eeaktor. Prepared.

Comparative tests with the cured films gave the following results:

Paint I II

Whiteness. 89.9. 88.5

Royal hardness, s 179 175

Pencil hardness 2 H 1 H

BS impact strength, J 2.16 0.8

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Paint I II

Erichsen impact strength, mm
Resistance to xylene after 15

"after 60 min

MIBK- "after 15 min." "" After 60 min

The results of the comparative experiments show that paints can be produced with copolymers prepared according to the invention or JTilme can be obtained in which the hardness, the impact strength and the solvent resistance is improved.

2.3 1 , 0 2 H 1 H 1 H. . j? 2 II 1 H HB 1 B.

PATENT CLAIMS:

309842/0849

Claims (13)

PATENT CLAIMS 1) Process for emulsion copolymerization that can be carried out in batches of (A) a hydroxyl group-containing ester of the formula: EC (O) -O-CH ₂ -GH (OH) -CH ₂ -OO (O) -E ', where E is an a, ß-ethylenically unsaturated group and E ^{1 is} a group free of ethylenic unsaturation, with (B) at least one other ethylenically unsaturated monomer, the comonomers and the catalyst continuously or in individual portions in an on Copolymerxsati ons during the copolymerization temperature-heated reactor, characterized in that at the start of the copolymerization -in the aqueous starting phase in the reactor, a small amount of polymerization inhibitor is already present in relation to the total amount of catalyst. 2) Method according to claim 1, characterized in that - 2 309842/0849 ? 31 β η ι η net that the inhibitor is 4-hydroxyanisole. 3) Method according to claim 1 or 2, characterized in that g e k e η η indicates that the acyl group E-G (O) -O- in the hydroxy-containing ester is an acrylic acid or methacrylic acid residue is. 4) Method according to claim 1, 2 or 3> characterized in that the group - (O) C-E ' in the hydroxy-containing ester is the ester of a saturated tertiary monocarboxylic acid. 5) Method according to claim 4 ·, characterized in that the group E'-C (O) - of the hydroxy-containing Esters an acid residue of the formula: R ₁ -C- C (O) - where R. CH ^ - and ££ and. E ^ alkyl groups with ge Λ to 16 carbon atoms mean. 6) Method according to one of the preceding claims, characterized in that the group E ¹ -C (O) - of the hydroxy-containing ester has at least 8 carbon atoms. 7) Method according to one of the preceding claims, - 3 - T098A2 / 0ö4ö characterized _{2 in} that the monomer (B) is vinyl chloride. 8) Method according to one of the preceding claims, characterized in ₅ that the copolymerization between 31-0 and 375 ° ^? is carried out preferably between 330 and 36 ° I £. 9) Method according to one of the preceding claims, characterized in ₉ that the oomonomers (A) and (B) in - the - to be supplied - mixture are present in a weight ratio between 2 € k80 and 40:60. '. 10) The method according to a © ® d @ r ~ preceding .Ansprüche _} characterized in that during the continuous or the portionwise addition © to the reactor in the mixture @ a constant weight ratio between the monomers (A) and (B) is maintained » 11) Method according to one of the preceding claims, characterized in that the. Comonomers (A) and (B) mixed together in the form an aqueous emulsion indicates. ■ 1 * 2) Process according to one of the preceding claims, characterized in that the catalyst is added continuously or in portions to the reactor in an amount of 0.1 to 0.5 % of the monomer weight. 13) Method according to one of the preceding claims, - 4 - 309842/0849 characterized in that the amount of inhibitor present in the aqueous starting phase 0.01 to 10 mol%, preferably 0.1 to 5 mol%, calculated on the total amount of catalyst to be fed, amounts to. 309842/0849