EP1622967A1

EP1622967A1 - Method for the production of powder-type ethylene vinyl alcohol mixed polymers

Info

Publication number: EP1622967A1
Application number: EP04730227A
Authority: EP
Inventors: Kurt Stark
Original assignee: Wacker Polymer Systems GmbH and Co KG
Current assignee: Wacker Polymer Systems GmbH and Co KG
Priority date: 2003-05-15
Filing date: 2004-04-29
Publication date: 2006-02-08
Also published as: WO2004101655A1; JP2006526050A; US20060258803A1; DE10321942A1; CN1832983A

Abstract

The invention relates to a method for the production of powder-type ethylene vinyl alcohol mixed polymers by radical polymerisation of ethylene and one or several vinyl esters, and optionally other monomers which can be copolymerised therewith, subsequently saponification of the thus obtained ethylene vinyl ester polymer mixture in order to form ethylene vinyl alcohol mixed polymers. The invention is characterised in that the ethylene vinyl alcohol mixed polymer is precipitated, after saponification, from the alcoholic solution by cooling according to a temperature gradient, and optionally, by the addition of water. In ethylene vinyl alcohol mixed polymers which are derived from low molecular ethylene vinyl ester mixed polymers, the average molecular weight Mw varies between 2000 - 100000 g/mol and the temperature gradient is between -0.1 DEG C/min to -10 DEG C/min. In ethylene vinyl alcohol mixed polymers which are derived from high molecular ethylene vinyl ester mixed polymers, the average molecular weight Mw is > 100000 g/mol and the temperature gradient is between -0.1 DEG C/min to -1 DEG C/min.

Description

Process for the preparation of powdery ethylene-vinyl alcohol copolymers

The invention relates to a process for the preparation of powdery ethylene-vinyl alcohol copolymers (EVOH) by radical polymerization of ethylene and. one or more vinyl esters and, if appropriate, further monomers copolymerizable therewith, subsequent saponification of the ethylene / vinyl ester copolymers thus obtained to give ethylene

Vinyl alcohol copolymers and precipitation of the saponification product.

Owing to their advantageous property profile, ethylene-vinyl alcohol copolymers are used in many applications. Ethylene-vinyl alcohol copolymers are characterized by chemical resistance, good adhesion to a wide variety of substrates, transparency, antistatic properties, oxygen-impermeable films, good thermoplastic processability, for example by means of extrusion. Because of these advantageous properties, ethylene-vinyl alcohol copolymers are used as foils and films in food packaging, for the manufacture of chemical-resistant bottles and tanks and for the protection of pipes and pipelines.

A number of processes for the production of ethylene-vinyl alcohol copolymers are known in the prior art, for example from JP-A 60-199004, JP-A 11-80263, EP-A 997250 and EP-A 1085028 Radically polymerized ethylene and vinyl acetate in alcoholic solution.

The vinyl acetate units are then saponified with an alcoholic solution of bases, for example methanolic NaOH, to vinyl alcohol. The ethylene-vinyl alcohol copolymers are isolated by extruding the copolymers into a coagulation bath, usually water or a Water / methanol mixture. The strands thus obtained are finally cut into pellets. After the pellets have dried, they can then be extruded to give the desired shaped articles.

These processes generally produce very high molecular weight ethylene-vinyl alcohol mixed polymers with a correspondingly high melt viscosity, but these can be processed without problems using extrusion. It is disadvantageous, however, that only poor yields are achieved with the saponification and the pellets have a high solvent content, which must be removed during drying. In order to obtain powdery products, the pellets would have to be ground in an additional, complex step.

It is known from ÜS-A 4100335, US-A 4104453 and ÜS-Ä 4820803 that ethylene-vinyl acetate copolymers are dispersed in water in the presence of emulsifiers or salts in the molten state, then saponified, then below the softening temperature of the saponification product can be cooled and isolated by filtration as a powder. The disadvantage here is the registration of auxiliaries which heavily contaminate the powdery end product. US-A 4719259 describes a process in which the ethylene-vinyl alcohol copolymer is precipitated with water in the form of a dough.

The object of the invention was to provide a process with which ethylene-vinyl alcohol copolymers can be obtained in powder form in a simple manner and with high purity.

The invention relates to a process for the preparation of powdery ethylene-vinyl alcohol copolymers by radical polymerization of ethylene and one or more Vinyl esters, and optionally other monomers copolymerizable therewith, subsequent saponification of the ethylene-vinyl ester copolymers obtained therewith to give ethylene-vinyl alcohol copolymers, characterized in that the ethylene-vinyl alcohol copolymer after saponification from the alcoholic solution by cooling to a temperature Gradient, and optionally addition of water, is precipitated, the temperature gradient being -0.1 ° C / in the case of ethylene-vinyl alcohol copolymers which are derived from low molecular weight ethylene-vinyl ester copolymers with a weight-average molecular weight Mw of from 2000 to 100000 g / mol. min to -10 ° C / min, and for ethylene-vinyl alcohol copolymers which are derived from high molecular weight ethylene-vinyl ester copolymers with a weight-average molecular weight Mw of> 100000 g / mol, the temperature gradient -0.1 ° C / min to - is 1 ° C / min.

The ethylene-vinyl ester polymers can be prepared in a known manner by means of radical polymerization; preferably by bulk polymerization, emulsion polymerization, suspension polymerization or by polymerization in organic solvents, particularly preferably in alcoholic solution with monohydric, aliphatic alcohols having 1 to 4 carbon atoms or mixtures thereof as solvents. Suitable solvents are, for example, methanol, ethanol, propanol,

Isopropanol and an ethanol-isopropanol mixture. The polymerization is carried out under reflux at a temperature of 35 ° C to 100 ° C. Ethylene is abs with a pressure of 10 to 90 bar. pressed. The radical initiation takes place by adding common initiators. Examples of common initiators are percarbonates such as cyclohexyl peroxidicarbonate, peresters such as t-butyl perneodecanoate or t-butyl perpivalate, peroxide initiators such as tert. -Butyl hydroperoxide, diacyl peroxides such as dilauroyl peroxide, and azo initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis- (4-methoxy-2, 4-dimethylvaleronitrile). To obtain relatively low molecular weight products, ie with a weight average molecular weight Mw of 2000 to 100000 g / mol, preferably 5000 to 60,000 g / mol, relatively large amounts of initiator are preferably used, preferably 0.2 to 1.0% by weight, particularly preferably 0.4 to 0.8% by weight, based in each case on the total weight of the comonomers without the ethylene component. In order to obtain relatively high molecular weight products, ie products with a weight average molecular weight Mw> 100000 g / mol, polymerization is preferably carried out with an initiator amount of 0.01 to 0.1% by weight, based on the total weight of the comonomers without the ethylene component.

The monomers can be initially introduced, added in total or introduced in portions and the rest can be added after the initiation of the polymerization. In a preferred embodiment, in particular for obtaining low molecular weight copolymers, the vinyl ester content is 5 to 50% by weight, particularly preferably 15 to 30% by weight, and the remaining portion is added in each case. The initiator is preferably initially charged at 5 to 50% by weight, particularly preferably 15 to 30% by weight, and the remaining portion is metered in in each case.

The molecular weight can also be adjusted in a manner known to those skilled in the art by polymerization in the presence of molecular weight regulators. Suitable regulators are, for example, alcohols such as ethanol or isopropanol, aldehydes such as acetaldehyde or propionaldehyde, mercaptans such as mercaptopropionic acid and dodecyl mercaptan, silane-containing regulators such as mercaptosilane, for example 3-mercaptopropyltrimethoxysilane. Polymerization is preferably carried out in methanol or in solvents with a high transfer rate, such as ethanol or isopropanol or mixtures thereof. The adjustment of the molecular weight can also about the temperature, the type and concentration of the initiator and the solvent content.

Suitable vinyl esters are vinyl esters of unbranched or branched carboxylic acids having 1 to 18 carbon atoms. Preferred vinyl esters are vinyl acetate, 1-methyl vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, vinyl pivalate and vinyl esters of α-branched monocarboxylic acids with 5 to 13 carbon atoms, for example VeoVa9 ^R or VeoVal0 ^R (trade name from Shell). Vinyl acetate is particularly preferred.

The ethylene content in the copolymer is generally 5 to 75 mol%, preferably 20 to 60 mol%, particularly preferably 25 to 50 mol%. Most preferred are ethylene-vinyl acetate copolymers with the ethylene proportions mentioned.

In addition to vinyl esters, one or more monomers from the group comprising methacrylic acid esters and acrylic acid esters of alcohols having 1 to 15 carbon atoms, alpha-olefin having 3 to 12 carbon atoms, dienes, vinyl aromatics and vinyl halides may also be copolymerized , Suitable monomers from the group of the esters of acrylic acid or methacrylic acid are esters of unbranched or branched alcohols having 1 to 15 carbon atoms. Preferred methacrylic acid esters or acrylic acid esters are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-, iso- and t-butyl acrylate, n-, iso- and t-butyl methacrylate, 2-ethylhexyl acrylate, norbor- nyl acrylate. Suitable alpha-olefins are, for example, propene, isobutylene, 1-butene, 1-hexene, .1-octene, 1-dodecene. Suitable dienes are 1,3-butadiene and isoprene. Styrene and vinyl toluene can be copolymerized as vinyl aromatics. From the group of vinyl halides, vinyl chloride and vinylidene chloride are preferred. The proportion of these comonomers is dimensioned such that the sum of the ethylene and vinyl ester fraction is> 50 mol% in the ethylene-vinyl ester polymer. If appropriate, functional comonomers can also be present in a proportion of preferably 0.1 to 25 mol%. Examples include ethylenically unsaturated mono- and dicarboxylic acids, preferably acrylic acid, methacrylic acid, fumaric acid, cotonic acid, itaconic acid and maleic acid; ethylenically unsaturated carboxamides and nitriles, preferably N-vinylformamide, acrylamide and acrylonitrile; Mono- and diesters of fumaric acid and maleic acid such as the diethyl and diisopropyl esters as well as maleic anhydride, ethylenically unsaturated. Sulfonic acids or their salts, preferably vinylsulfonic acid, 2-acrylamido-2-methyl-propanesulfonic acid; Alkyl vinyl ethers, vinyl ketones, N-vinyl pyrrolidone; Vinyl and methacrylic silanes such as vinyltrimethoxysilane and methacryloxypropyltrimethoxysilane; Mercaptosilane. Further examples are pre-crosslinking comonomers such as polyethylenically unsaturated comonomers, for example divinyl adi-pat, diallyl maleate, allyl methacrylate, butanediol diacrylate or triallyl cyanurate, or post-crosslinking comonomers, for example acrylamidoglycolic acid (AGA), methylacrylamidoglycolic acid, methylamide (NMA), methyl (MAGMA), (MAGMA), methyl (MA) Methylolmethacrylamide, N-methylolallyl carbamate, alkyl ethers such as the isobutoxy ether or ester of N-methylolacrylamide, N-methylol methacrylamide and N-methylolallyl carbamate.

The saponification (transesterification, hydrolysis) of the ethylene-vinyl ester copolymer is carried out in a manner known per se, for example by the kneader process or in a stirred kettle, in alkaline or acidic form, with addition of acid or base. The ethylene-vinyl ester copolymer is preferably present in alcoholic solution with monohydric, aliphatic alcohols having 1 to 4 carbon atoms or mixtures thereof as solvents. Methanol and an ethanol / isopropanol mixture are particularly preferred. The content of ethylene-vinyl ester copolymer in the solution is 20 to 85% by weight, preferably 30 to 80% by weight. The usual acidic or alkaline catalysts are used to initiate the hydrolysis. Acidic catalysts are, for example, strong mineral acids, such as hydrochloric acid or sulfuric acid, or strong organic acids, such as aliphatic or aromatic sulphonic acids. Alkaline catalysts are preferably used. These are, for example, the hydroxides, alcoholates and carbonates of alkali or alkaline earth metals. The hydroxides of lithium, sodium and potassium are preferred; sodium hydroxide is particularly preferred. The alkaline catalysts are used either in solid form (100%) or in the form of their aqueous or alcoholic solutions, preferably in alcoholic solution, and particularly preferably in the same alcohol which is used to dissolve the ethylene-vinyl ester copolymer. A methanolic solution of NaOH is most preferred. The amounts of alkaline catalyst used are generally 0.2 to 20.0% by weight, based on the ethylene-vinyl ester copolymer.

The hydrolysis is generally carried out at temperatures of from 40 ° C to ^'90 ° C, preferably 50 ° C to 85 ° C is performed. In the case of a batchwise procedure, the alcoholic polyvinyl ester solution is fed to a reaction vessel, generally a stirred tank or a kneader. The saponification is initiated by adding the catalyst solution. When the desired degree of hydrolysis is reached, generally at a degree of hydrolysis of the vinyl ester content of 85 to 100 mol%, preferably 95 to 100 mol%, the hydrolysis is stopped. The ester formed during the transesterification is preferably distilled off during the saponification reaction.

In the case of acid-catalyzed hydrolysis, termination is carried out by adding alkaline reagents. These are, for example, the hydroxides, alcoholates and carbonates of alkali or alkaline earth metals. The hydroxides of lithium, sodium and potassium are preferred; sodium hydroxide is particularly preferred. In the preferred alkaline-catalyzed hydrolysis, termination is carried out by adding acidic reagents, such as carboxylic acids or mineral acids; or neutral reagents such as carboxylic acid esters. Carboxylic acid esters such as methyl acetate or ethyl acetate are preferred, as are relatively strong carboxylic acids and mineral acids, preferably with a pKa value of less than 4.5, particularly preferably with a pKa value of less than 2.5. Suitable mineral acids are, for example, hydrochloric acid, sulfuric acid and nitric acid; Suitable carboxylic acids are, for example, acetic acid, oxalic acid, formic acid, aliphatic and aromatic sulfonic acids and halogen carboxylic acids such as mono-, di- or trichloroacetic acid.

After the saponification reaction has ended, the ethylene-vinyl alcohol copolymer formed is separated from the liquid phase by precipitation.

In the case of ethylene-vinyl alcohol copolymers, which are derived from low molecular weight ethylene-vinyl ester copolymers with a weight-average molecular weight Mw of 2000 to 100000 g / mol, preferably 5000 to 60,000 g / mol, the temperature gradient is -0.1 ° C / min to - 10 ° C / min, preferably -l ° C / min to -10 ° C / min.

In the case of ethylene-vinyl alcohol copolymers, which are derived from high molecular weight ethylene-vinyl ester copolymers with a weight-average molecular weight Mw of> 100,000 g / mol, the temperature gradient is -0.1 ° C./min to -l ° C./min, preferably - 0.1 ° C / min to -0.5 ° C / min.

In general, the mixture is cooled to a temperature which is above the Tg of the solvent-containing ethylene / vinyl alcohol copolymer, but below the melting point of the ethyl len-vinyl alcohol mixed polymer. It is preferably cooled to a temperature of 10 ° C to 35 ° C.

In a preferred embodiment, in the case of the high molecular weight ethylene-vinyl alcohol copolymers, initially with a relatively high cooling capacity, that is to say a temperature gradient from -1 ° C./min to -10 ° C./min, to a temperature of preferably 40 ° C. to Cooled 70 ° C, and then continued cooling with a lower temperature gradient from -0.1 ° C / min to -1 ° C / min, up to a temperature of 10 ° C to 35 ° C.

The precipitation of the ethylene-vinyl alcohol copolymer is preferably supported by adding water. For this, water is added during, preferably after cooling to the desired final temperature. The amount of water is generally 0.3 times to 5.0 times, preferably 0.8 to 2.5 times the amount by weight of the ethylene-vinyl ester copolymer used. The temperature of the water generally corresponds to the room temperature or the temperature of the cooled saponification batch. It can also be done in such a way that after the precipitation the alcohol content is distilled off and successively replaced with the appropriate amount of water.

The precipitated ethylene-vinyl alcohol copolymer can be separated off by filtration and is generally present with a residual moisture content of <50%. The product is usually dried, for example with hot air, and is available as a powder after drying. The grain size, determined as the mean volume diameter Dv, is 20 to 2000 μm, preferably 100 to 1000 μm. The desired grain size can be controlled by the process, that is to say via the temperature gradient during cooling and precipitation, via the addition of water and its amount, and via the stirring speed during the Crystallization. The complex melt viscosity of the products is preferably 0.5 to 100000 Pas, in particular 1 to 1000 Pas (at 180 ° C; oscillating measurement at 1 Hz with plate / plate measuring system, device: Bohlin CVO 120 HR).

In a preferred embodiment, the powder obtained is resuspended in water, optionally freed from solvent residues by distillation or stripping, and the pulverulent product is isolated by filtration. To remove alkali salts and to set the desired ash content, the powder can optionally be washed with water.

To avoid discoloration in the melt, that is to increase the thermal stability, to avoid gel bodies or fish eyes in the melt and to improve the adhesion, the powder can optionally be doped. Suitable dopants are known to the person skilled in the art: for example carboxylic acids such as acetic acid, lactic acid, ascorbic acid, citric acid, hydroxylactones; Salts such as alkali metal, alkaline earth metal salts and salts of the elements of the 3rd main group with inorganic or organic anions such as sodium, potassium, calcium and magnesium acetate; Boron compounds such as boric acid, boric acid esters (borates) and boric acid salts; further phosphorus-containing compounds, such as salts of phosphoric (1- to 3-valent) or phosphonic acid (1- to 2-valent) such as NaH ₂ P0 ₄ , Na ₂ HP0 ₄ .

The doping is preferably carried out in the course of resuspending, by adding an aqueous solution of the substances mentioned. The amounts added depend on the desired property profile.

Additives may be added to the ethylene-vinyl alcohol copolymers, for example fillers, UV absorbers, plasticizers, antioxidants, flame retardants, extenders, thermal stabilizers, thermoplastics, adhesion promoters. The ethylene-vinyl alcohol copolymers can be used for the production of films, films and laminates, for the production of moldings. Further areas of application are as coating agents, as an additive for powder coatings, as adhesives and as binders in building materials.

The advantages of this procedure can be summarized as follows:

Low molecular weight products can be obtained, and the range of molecular weights can be very wide. The low molecular weight ethylene-vinyl ester mixed polymers (Mw <100000 g / mol), especially the very low molecular weight ones with Mw <50,000 g / mol, can be converted with the process into pulverulent ethylene-vinyl alcohol mixed polymers that are easy to process. The products obtained have a homogeneous structure. The low solution viscosity leads to advantages during the polymerization: Solutions with a solids content of up to 95% can also be stirred.

There is no Tromsdorff effect. Accordingly, the conversion of vinyl acetate can be brought to almost 100%, which means very high yields, since vinyl acetate is polymerized almost completely. This requires a very easy demonomerization: vinyl acetate, which is already very well polymerized and therefore only exists in small quantities, can be removed very easily due to the low solution viscosity. The content of residual monomer vinyl acetate can be set to values of 20 pp and less. In the case of saponification, this leads to the fact that no lye is consumed by impurities and, above all, to the fact that no acetaldehyde is formed from vinyl acetate (acetaldehyde leads to a yellow discolouration of the end product EVOH in an alkaline medium through aldol condensation). Depending on the molecular weight, the solution of the low molecular weight resin can still be pumped with a very high solids content of approx. 70 to 80% and can be added to the saponification with a high percentage. This saves a lot of solvent overall. With ethylene-vinyl ester copolymers with low molecular weights, ethylene-vinyl alcohol copolymers are obtained with a very good and advantageous melt flow.

Examples:

Production of the ethylene-vinyl acetate solid resins:

Example A (high molecular solid resin): 789.45 g of methanol, 9.52 kg of vinyl acetate, 1.88 g of PPV (tertiary butyl perpivalate, 75% by weight in aliphates, 0.0148% by weight, based on VAc) were placed in a 19 liter pressure autoclave. The kettle was heated to 70 ° C. and 60 bar of ethylene were injected, which were held until the end of the reaction. The batch was then run at 70 ° C. for 7 hours to a solids content of 59.8%.

At this solids content, the mixture thickened, which means that mixing and thus the removal of the heat of reaction was no longer possible. At this point, however, the polymerization was complete because the initiator was used up.

Now 4 kg of methanol were placed in the flash tank and 4 kg of methanol were metered in, the batch was simultaneously depressurized. After the pressure had been released, the kettle was heated up for distillation, during which fresh methanol was added to the kettle every 30 minutes and corresponded to the amount distilled off (demonomerization). analysis:

Fixed content FG: 30.55% (in methanol); Viscosity (Höppler - 10% in ethyl acetate): 14.34 mPas; Acid number SZ (methanol): 5.51 mg KOH / g; Residual vinyl acetate: 55 ppm; Saponification number: 519.05, mg KOH / g; Ethylene content from ^ -NMR: 20.69% by weight (44.54 mol%); SEC M _w = 114632, M _n = 35223, polydispersity = 3.52 (note: eluent is always THF, the values are relative to polystyrene standards);

Tg of the dried resin: 0.9 ° C. Note: The Tg of ethylene-containing solid resins can be estimated very easily using the following formula (Fox equation): 1 / Tg =% by weight (Et) / 180K 4% by weight (Vac) / 316K. Theoretically, a value of 0.13 ° C is calculated here.

Example B (low molecular weight solid resin):

2250 g of ethanol, 411.29 g of isopropanol, 2.38 kg of vinyl acetate and 14.3 g of PPV (tertiary butyl perpivalate, 75% by weight in aliphatics) were placed in a 19 liter pressure autoclave. The kettle was heated to 70 ° C. and 60 bar of ethylene were injected, which were held until the monomer metering had ended. When 70 ° C was reached, the initiator metering started, which consisted of 417.22 g of ethanol and 55.63 g of PPV (tertiary butyl perpivalate, 75% by weight in aliphatic). This dosing ran over 430 min with a dosing rate of 66 g / h.

The monomer metering, which consisted of 7.15 kg of vinyl acetate, started 10 minutes after the initiator metering had started. This dosage ran over 360 min. After the end of the initiator metering, the temperature of 70 ° C. was maintained for a further 90 min. Then it was relaxed. After the pressure had been released, the kettle was heated to distillation, during which fresh methanol was added to the kettle every 30 minutes and corresponded to the amount distilled off (demonomerization and solvent exchange). analysis:

FG: 45.55% (in methanol); Viscosity (Höppler - 10% in

Ethyl acetate): 2.23 mPas; SZ (methanol): 5.05 mg KOH / g;

Residual vinyl acetate: 16 ppm; Saponification number: 425.37 mgKOH / g; Ethylene content from ^ -NMR: 30.48% by weight (57.44 mol%); SEC M _w = 23666, M _n = 8900, polydispersity = 2.66; Tg of the dried resin: -17.0 ° C.

Note: A value of -16.3 ° C is theoretically calculated here.

Production of the ethylene vinyl alcohol powder:

Example 1 (High Molecular Weight EVOH, Two Temperature Gradients): 838 g of a 35.8% strength by weight methanolic solution of an ethylene-vinyl acetate solution obtained as in Example A were placed in a 3 liter double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel). Copolymers with 36.25 mol% of ethylene and 63.75 mol% of vinyl acetate and a weight-average molecular weight Mw of 175,581 g / mol were weighed out. This solution was diluted by adding 162 g of methanol, so that a 30% by weight Solution resulted. The solution was then heated to a jacket temperature of 80 ° C. with stirring (200 rpm, paddle stirrer). After the temperature had been reached, the saponification process was started by dropwise addition of 333 g of a 9% by weight methanolic sodium hydroxide solution - corresponding to 30 g of solid NaOH = 10% by weight of the amount of solid resin. The dosing was carried out by adding two lye solutions, each 15 minutes at an interval of 30 minutes. During the metering and then for a further 1 h 40 min, a total of 800 ml of solvent mixture methyl acetate / methanol were distilled off under vacuum and replaced by methanol. The saponified solution was then cooled to 60 ° C. first, at full cooling capacity (-2 ° C./min). From then on, the mixture was slowly cooled to 30 ° C. via a temperature ramp of -0.17 ° C./min, so that the ethylene-vinyl alcohol copolymer could crystallize.

After cooling, 500 g of distilled water were added and stirred in briefly. As a result, the ethylene-containing polyvinyl alcohol was precipitated as a powder. A solid-liquid separation was then carried out using a Nutsche. The fancy, powdery solid solid was very well separated from the suspension. The filter cake was put back into the reaction vessel and washed with 1 1 dist. Water resuspended. The residual solvent was then removed by stripping at a jacket temperature of 50 ° C. and vacuum (stripping). The mixture was then cooled again to room temperature, the solid was again separated from the suspension via a suction filter and the filter cake was distilled with 2 liters. Washed water. A finely powdered EVOH with a saponification number of 0.78 mg KOH / g was obtained. analysis:

Composition from 1 H NMR: 26.56% by weight (36.25 mol%) of ethylene; 0.12 wt% VAc; 73.32 wt% VOH; DSC measurement: Tg: 56.92 ° C; Peak temperature Tm of the melting point: 179.35 ° C; Enthalpy of fusion Hm: 86.45 J / g

Particle size of the product (Coulter measurement): surface 774.2 cm ² / g; mean volume diameter Dv (mean) 821.3 μm; number average particle size Dn (mean) 0.0891 μm.

Example 2 (high molecular EVOH, single-stage cooling with a low temperature gradient):

34.6 kg of a 49.9% by weight solid resin solution of an ethylene-vinyl acetate copolymer obtained in analogy to Example A with 44.0 mol% of ethylene and 56.0 mol% of vinyl acetate and one were placed in a 120 liter double-walled, temperature-controlled reaction vessel (with distillation bridge and metering pump) average molecular weight Mw of 111794 g / mol and diluted to a solids content of 31% by adding 20.95 kg of methanol. The solution was then heated to a jacket temperature of 70 ° C. with stirring (95 rpm, anchor stirrer). After the temperature had been reached, the saponification process was started by metering in 20.31 kg of an 8.5% by weight methanolic sodium hydroxide solution, corresponding to 1.73 kg of NaOH solid = 10% by weight of the amount of solid resin r. The dosing took place within 1 h 20 min. During dosing and afterwards for 2 h 15 For a total of 31.5 kg of methyl acetate / methanol solvent mixture were distilled off under vacuum and replaced by 10 kg of methanol, ie the solution was slightly concentrated. The saponified solution was then cooled from -0.5 ° C./min to 23 ° C. using a temperature ramp. While cooling, at 60 ° C., the solution was adjusted from pH 9.4 to pH 7.3 with 300 ml of 100% acetic acid. The cooled solution was then stirred for 18 h 20 min at 23 ° C and a stirring speed of 45 rpm. After this "crystallization time" 40 kg of distilled water were added and stirred in. To remove the solvent, the suspension was then heated to a jacket temperature of 50 ° C. and distilled (stripped) with vacuum. In total, 38 kg of solvent mixture were distilled off, gradually , in portions of 10 kg distilled water was added (total 60 kg).

After cooling to room temperature, the solid-liquid separation was carried out using a suction filter with an inserted linen cloth. The powdery solid could be separated from the suspension very well (very good flow), so that the filter cake could be washed with 20 kg of distilled water without any problems.

A finely powdered EVOH with a saponification number of 28.7 mg KOH / g was obtained. Analyzes: Composition from ¹ H-NMR: 32.61% by weight (44.00 mol%) of ethylene; 4.41 wt% VAc; 62.98 wt% VOH;

DSC measurement: Tg: 51.2 ° C; Peak temperature Tm of the melting point: 164.3 ° C; Enthalpy of fusion Hm: 91.3 J / g particle size of the product (Coulter measurement): surface 223.7 cm ² / g; mean volume diameter Dv (mean) 588.5 μm; number average particle size Dn (mean) 1.55 μm.

Example 3 (Low Molecular Weight EVOH):

In a 3 liter double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel), 1084 g a 73.8% methanolic solid resin solution of the ethylene-vinyl acetate copolymer obtained in Example B with 57.44 mol% of ethylene and 42.56 mol% of vinyl acetate and an average molecular weight Mw of 23666 g / mol were weighed out. The solution was then heated to a jacket temperature of 80 ° C. with stirring (200 rpm, paddle stirrer). After the temperature had been reached, the saponification process was started by dropwise addition of 800 g of a 10% by weight methanolic sodium hydroxide solution - corresponding to 80 g of solid NaOH = 10% of the amount of solid resin. The dosing took place within 1 hour. During the metering and then for a further 1 h 15 min, a total of 763 g of methyl acetate / methanol solvent mixture were distilled off in vacuo and replaced by 343 g of methanol. The saponified solution was then cooled from -l ° C / min to 23 ° C using a temperature ramp. The EVOH crystallized (in part). While cooling, at 60 ° C., the solution was adjusted from pH 10.5 to pH 7.5 with 20 ml of 100% acetic acid. After cooling, 800 g of dist. Water added, briefly stirred in, whereby the (partially) crystalline EVOH was precipitated in the form of a powder. Then the solid-liquid separation was carried out using a Nutsche. The powdery solid was very easy to separate from the suspension. The filter cake was put back into the reaction vessel and washed with 1 1 dist. Water resuspended. Now the remaining solvent was removed (stripping) by distillation at a jacket temperature of 45 ° C. and vacuum. The mixture was then cooled again to room temperature, the solid was again separated from the suspension via a suction filter and the filter cake was distilled with 2 l of distilled water. Washed water (very good flow).

A white, finely powdered EVOH with a saponification number of 12.6 mg KOH / g was obtained. Analyzes: Composition from ^ Η NMR: 45.77% by weight (57.44 mol%) of ethylene; 1.94 wt% VAc; 52.29 wt% VOH. DSC measurement: Tg: 17.3 ° C; Peak temperature T (peak) of melting point: 125.5 ° C; Enthalpy of fusion Hm: 64.0 J / g particle size of the powdery product (Coulter measurement): surface 2316 cm ² / g; mean volume diameter Dv (mean) 217.6 μm; number average particle size Dn (mean) 1.90 μm.

Comparative Example 4 (High Molecular EVOH):

838 g of a 35.8% solid resin solution of an ethylene / vinyl acetate copolymer obtained as in Example A with 36.25 mol% of ethylene and 63.75 mol% of vinyl acetate and a weight-average molecular weight Mw were placed in a 3 liter double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel) Weighed in at 175581 g / mol. This solution was diluted by adding 162 g of methanol to give a 30% solution. The solution was then heated to a jacket temperature of 80 ° C. with stirring (200 rpm, paddle stirrer). After the temperature was reached, the saponification process was started by adding 333 g of a 9% methanolic sodium hydroxide solution dropwise - corresponding to 30 g of solid NaOH = 10% of the amount of solid resin. The dosing was carried out by adding two lye solutions, each 15 minutes at an interval of 30 minutes. During the metering and then for a further 1 h 10 min, a total of 600 ml of methyl acetate / methanol solvent mixture were replaced by methanol. The saponified solution was then cooled to 30 ° C. in the course of 25 minutes, with the cooling unit's full cooling capacity (−2 ° C./min). From a jacket temperature of approx. 38 ° C, the product plasticized in the solution to form rubber-like particles which, taken as a whole, resembled a moss-like structure. Then 500 g of dist. Water is added, briefly stirred in and then the solid-liquid separation is carried out using a suction filter. Due to the low flow, the separation was very difficult. A plasticized EVOH with a saponification number of 1.7 mg KOH / g was obtained. The very coarse particles had The structure and overall looked like a moss structure. analysis:

Composition from ¹ H-NMR: 26.54% by weight (36.25 mol%) of ethylene; 0.26 wt% VAc; 73.20 wt% VOH.

DSC measurement: Tg: 54.55 ° C; Peak temperature Tm of the melting point: 175.73 ° C; Enthalpy of fusion Hm: 68.29 J / g particle size of the product (Coulter measurement): not applicable since no powdery product was obtained.

Example 5 (low molecular weight EVOH with a high degree of purity): 724.6 g of a 69.0% strength methanolic solid resin solution of an ethylene / vinyl acetate copolymer with 56.5 mol% of ethylene obtained in analogy to Example B were placed in a 3 liter double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel) and 43.5 mol% of vinyl acetate and an average molecular weight Mw of 53463 g / mol. The solution was then heated to a jacket temperature of 60 ° C. with stirring (200 rpm, paddle stirrer). After the temperature had been reached, the saponification process was started by dropwise addition of 403 g of a 6.2% by weight methanolic sodium hydroxide solution - corresponding to 25 g of NaOH solid = 5.0% of the amount of solid resin. The dosing was carried out by adding two lye solutions, each 15 minutes at an interval of 30 minutes. After a saponification time of 5 hours, the batch was cooled from 60 ° C. to 40 ° C. with a ramp of -3 ° C./min. A (partial) crystallization of the ethylene-vinyl alcohol copolymer occurred. When the stirrer had stopped, 250 g of ethyl acetate were then added for neutralization and the mixture was briefly stirred in at 50 rpm. After the ethyl acetate had acted on for 10 minutes (without stirring), the precipitation of the crystalline ethylene-vinyl alcohol copolymer was completed by adding 500 g of water (at a temperature of 23 ° C.). A suspension with finely divided powder was obtained. The suspension was then heated to 60 ° C., stirred at 100 rpm and distilled under vacuum. 550 ml of solvent were removed and 950 ml of water were added in the course of the distillation. The suspension was then cooled to 23 ° C. using a ramp of -3 ° C./min. Then the solid-liquid separation was carried out using a Nutsche.

The residue on the suction filter was placed in a burlap sack and washed under running water for 1 hour. The washed ethylene-vinyl alcohol copolymer in a linen sack was again placed in the reaction vessel and washed with 1 l of distilled water. Water resuspended. At a jacket temperature of 60 ° C and a stirrer speed of 100 rpm, residual solvent was removed under vacuum (stripping). The mixture was then cooled again to room temperature (23 ° C.), the solid was again separated from the suspension via a suction filter and the filter cake was distilled with 2 l of distilled water. Washed water (very good flow). Finally, the product was dried in a vacuum drying cabinet. A highly pure, finely powdered, white EVOH with a saponification number of 22.1 mg KOH / g was obtained. analysis:

Composition from Hϊ-NMR: 44.5% by weight (56.5 mol%) of ethylene; 3.4% by weight vinyl acetate; 52.1% by weight of vinyl alcohol. DSC measurement: Tg: 31.1 ° C, Tm (peak) = 118.6 ° C, enthalpy of fusion Hm = 59.7 J / g; Particle size of the powdery product (Coulter measurement): surface 1775 cm ² / g; mean volume diameter Dv (mean) 405 μm; number average particle size Dn (mean) 0.103 μm.

Comparative Example 6 (low molecular weight EVOH, no cooling with temperature gradient)

As in Example 5, with the difference that immediately after the saponification, the mixture was neutralized with 250 g of ethyl acetate at a jacket temperature of 60 ° C. and then 500 g of water were added. Since the ethylene-vinyl alcohol copolymer was not yet crystallized at that time and at that time- was still in the plastic state, the addition of water led to an immediate coagulation, so that a "dough" was obtained. A powdery product could therefore not be obtained, since only a controlled cooling rate over a certain temperature ramp would have been necessary.

Example 7 (very low molecular weight EVOH):

653.6 g of a 76.5% strength methanolic solid resin solution of an ethylene-vinyl acetate copolymer obtained in analogy to Example B with 70.9 mol% of ethylene and 29.1 mol% of vinyl acetate and an average molecular weight were placed in a 3 liter double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel) Weighed in Mw of 6872 g / mol. The solution was then heated to a jacket temperature of 60 ° C. with stirring (200 rpm, paddle stirrer). After the temperature had been reached, the saponification process was started by dropwise addition of 820 g of a 6.1% by weight methanolic sodium hydroxide solution - corresponding to 50 g of solid NaOH = 10.0% of the amount of solid resin. The dosing was carried out by adding two lye solutions, each 15 minutes at an interval of 30 minutes.

After a saponification time of 3.5 hours, the batch was cooled from 60 ° C. to 23 ° C. with a ramp of -5 ° C./min. A crystallization of the ethylene-vinyl alcohol copolymer occurred. By adding 1000 g of water, the precipitation into powdery particles with the desired particle size was achieved. Finally, the solid-liquid separation was carried out using a Nutsche.

The powdery solid was very easy to separate from the suspension. The filter cake on the suction filter was washed with 2 l of water, then put back into the reaction vessel and washed with 1 l of distilled water. Water resuspended. At a jacket temperature of 50 ° C and a stirrer speed of 100 rpm, residual solvent was removed under vacuum (stripping). The mixture was then cooled again to room temperature (23 ° C.) and the solid again from the suspension via a suction filter separated and the filter cake with 2 1 dest. Washed water (very good flow). Finally the product was dried in a vacuum drying cabinet.

A finely powdered, white EVOH with a saponification number of 11.7 mg KOH / g was obtained. analysis:

Composition from ¹ H-NMR: 60.3% by weight (70.9 mol%) of ethylene; 1.8% by weight vinyl acetate; 37.9% by weight of vinyl alcohol. DSC measurement: Tg: 8.6 ° C, Tm (peak) - 100.4 ° C, enthalpy of fusion Hm = 65.2 J / g;

Particle size of the powdery product (Coulter measurement): surface 4035 cm ² / g; mean volume diameter Dv (mean) 231.7 μm; number average particle size Dn (mean) 0.105 μm.

Example 8 (very low molecular weight EVOH)

Exactly like example 7, but with a modified work-up: After the precipitation into powdery particles with the desired particle size was achieved by adding 1000 g of water, the solid-liquid separation was carried out using a Nutsche. The powdery solid was very easy to separate from the suspension.

The filter cake on the suction filter was washed with 2 l of water and then dried in a vacuum drying cabinet. The residual solvent was not removed by resuspending and vacuum distillation (stripping). A finely powdered, white EVOH with a saponification number of 26.7 mg KOH / g was obtained. analysis:

Composition from ^ -NMR: 59.6% by weight (70.9 mol%) of ethylene; 4.1% by weight vinyl acetate; 36.3% by weight of vinyl alcohol. DSC measurement: Tg: 1.3 ° C, Tm (peak) = 97.8 ° C, enthalpy of fusion Hm = 59.9 J / g;

Particle size of the powdery product (Coulter measurement): surface 4104 cm ² / g; mean volume diameter Dv (mean) 288.2 μm; number average particle size Dn (mean) 0.106 μm. Example 9 (very low molecular weight EVOH):

1091.4 g of a 73.3% methanolic solid resin solution of an ethylene-vinyl acetate copolymer obtained in analogy to Example B with 67.6 mol% of ethylene and 32.4 mol% of vinyl acetate and an average molecular weight were placed in a 3 liter double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel) Weighed in Mw of 5520 g / mol. The solution was then heated to a jacket temperature of 80 ° C. with stirring (200 rpm, paddle stirrer). After the temperature had been reached, the saponification process was started by dropwise addition of 920 g of an 8.7% by weight methanolic sodium hydroxide solution - corresponding to 80 g of NaOH solid = 10.0% of the amount of solid resin. The lye was metered in within one hour. During the saponification time of 2.5 hours, 821 g of methyl acetate / methanol solvent mixture were drawn off under vacuum and 342 g of methanol were added. After this time, the saponification was terminated by adding 25 ml of glacial acetic acid, ie the mixture was neutralized to pH = 7.2. The mixture was then cooled to 23 ° C. using a temperature ramp of -1 ° C./min, as a result of which the EVOH polymer crystallized. The precipitation was completed by adding 800 g of water. Finally, the solid-liquid separation was carried out using a Nutsche. The powdery solid was very easy to separate from the suspension. The filter cake on the suction filter was washed with 2 l of water, then put back into the reaction vessel and washed with 1 l of distilled water. Water resuspended. At a jacket temperature of 45 ° C and a stirrer speed of 100 rpm, residual solvent was removed under vacuum (stripping). The mixture was then cooled again to room temperature (23 ° C.), the solid was again separated from the suspension via a suction filter and the filter cake was distilled with 2 l of distilled water. Washed water (very good flow). Finally the product was dried in a vacuum drying cabinet. A finely powdered, white EVOH with a saponification number of 8.4 mg KOH / g was obtained. Analyzes:

Composition from ^ Η NMR: 56.65% by weight (67.6 mol%) of ethylene; 1.29% by weight vinyl acetate; 42.06% by weight of vinyl alcohol. DSC measurement: Tg: 7.9 ° C, Tm (peak) = 99.8 ° C, enthalpy of fusion Hm = 63.3 J / g;

Particle size of the powdery product (Coulter measurement): surface 1235 cm ² / g; mean volume diameter Dv (mean) 814.4 μm; number average particle size Dn (mean) 0.105 μm.

Example 10 (High Molecular EVOH):

674.2 g of a 44.5% by weight methanolic solution of an ethylene / vinyl acetate copolymer obtained in analogy to Example A with 43.72 mol% of ethylene and 56.28 mol% of vinyl acetate and. Were placed in a 3 liter double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel) a weight average molecular weight Mw of 192875 g / mol. This solution was diluted by adding 326 g of methanol to give a 30% by weight solution. The solution was then heated to a jacket temperature of 80 ° C. with stirring (200 rpm, paddle stirrer). After the temperature had been reached, the saponification process was started by dropwise addition of 330 g of a 9.1% by weight methanolic sodium hydroxide solution - corresponding to 30 g of solid NaOH = 10% by weight of the amount of solid resin. The dosing was carried out by adding two lye solutions, each 15 minutes at an interval of 30 minutes. During the dosing and then for a further 1 h 30 min, a total of 800 ml of methyl acetate / methanol solvent mixture were distilled off and 800 ml of methanol were added. The saponified solution was then cooled to 23 ° C. at a cooling rate of -0.3 ° C./min. The saponified solution was then stirred at 23 ° C. for 4 hours so that the ethylene-vinyl alcohol copolymer could crystallize. The mixture was then reheated to 40 ° C. and the powder was precipitated by adding 1000 ml of water. After cooling to room temperature, a solid-liquid separation was carried out using see made. The precipitated, powdery solid was very easy to separate from the suspension. The filter cake on the suction filter was washed with 2 l of water, then again placed in the reaction vessel and with 2 l of distilled water. Water resuspended. Now the remaining solvent was removed (stripping) by distillation at a jacket temperature of 50 ° C. and vacuum. The mixture was then cooled again to room temperature, the solid was again separated from the suspension via a suction filter and the filter cake was distilled with 2 liters. Washed water. The product was finally dried in a vacuum drying cabinet.

A finely powdered, white EVOH with a saponification number of 0.0 mg KOH / g (100% fully saponified product) was obtained. Analyzes: Composition from 1 H NMR: 33.08% by weight (43.72 mol%) of ethylene, 66.92% by weight of vinyl alcohol;

DSC measurement: Tg: 52.74 ° C, Tm (peak) = 165.3 ° C, enthalpy of fusion Hm = 87.9 J / g. Particle size of the product (Coulter measurement): surface 127.1 cm ² / g; mean volume diameter Dv (mean) 769.5 μm; number average particle size Dn (mean) 3.57 μm.

Example 11 (High Molecular Weight EVOH, Water Added During Cooling): In a 3 liter, double-walled, temperature-controlled glass reaction vessel (with distillation bridge and dropping funnel), 1020 g of a 49.0% by weight methanolic solution of an ethylene-vinyl acetate copolymer obtained as in Example A with 29.82 Weighed out mol% ethylene and 70.18 mol% vinyl acetate and a weight-average molecular weight Mw of 155247 g / mol. The solution was then heated to a jacket temperature of 70 ° C. with stirring (200 rpm, paddle stirrer). After the temperature had been reached, the saponification process was carried out by dropwise addition of 556 g of a 9.0% by weight methanolic sodium hydroxide solution, which corresponds to 50 g of NaOH solid = 10% by weight of the solid Resin quantity - started. The dosing was carried out by adding two lye solutions, each 15 minutes at an interval of 30 minutes. During the dosing of the alkali, a total of 260 ml of methyl acetate / methanol solvent mixture were distilled off and 300 ml of methanol were added.

The saponified solution was then cooled to 40 ° C. at a cooling rate of -0.2 ° C./min. 200 ml of ethyl acetate were then added for neutralization while the stirrer was at a standstill, the mixture was briefly stirred in at 50 rpm and the mixture was left to stand for 10 min without stirring. Then 1500 ml of water were added and stirred in briefly at 50 rpm. A powdery precipitation occurred. The suspension obtained was then cooled to 23 ° C. with a ramp of 0.2 ° C./min in order to complete the crystallization of the ethylene-vinyl alcohol copolymer. A solid-liquid separation was then carried out using a Nutsche. The precipitated, powdery solid was very easy to separate from the suspension.

The filter cake on the suction filter was washed with 2 1 of water, then put back into the reaction vessel and washed with 1 1 of distilled water. Water resuspended. Now the remaining solvent was removed by stripping at a jacket temperature of 45 ° C and vacuum (stripping). The mixture was then cooled again to room temperature, the solid was again separated from the suspension via a suction filter and the filter cake was distilled with 3 l of distilled water. Washed water. The product was finally dried in a vacuum drying cabinet.

A finely powdered, white EVOH with a saponification number of 9.6 mg KOH / g was obtained. Analyzes: composition of ^ -NMR: 21.13% by weight (29.82 mol%) of ethylene; 1.48% by weight vinyl acetate; 77.39% by weight vinyl alcohol; DSC measurement: Tg: 58.1 ° C, Tm (peak) = 177.4 ° C, enthalpy of fusion Hm = 67.7 J / g. Particle size of the product (Coulter measurement): surface 973.4 cm ² / g; mean volume diameter Dv (mean) 574.4 μm; number average particle size Dn (mean) 0.109 μm.

Claims

Claims:

1. Process for the preparation of powdered ethylene

Vinyl alcohol copolymers by radical polymerization of ethylene and one or more vinyl esters, and optionally further monomers copolymerizable therewith, subsequent saponification of the ethylene-vinyl ester copolymers obtained therewith to give ethylene-vinyl alcohol copolymers, characterized in that the ethylene-vinyl alcohol -Mixed polymer after saponification from the alcoholic solution by cooling with a temperature gradient, and optionally adding water, precipitating, with ethylene-vinyl alcohol copolymers which differ from low molecular weight ethylene-vinyl ester copolymers with a weight-average molecular weight Mw derive from 2000 to 100000 g / mol, the temperature gradient is -0.1 ° C / min to -10 ° C / min, and in ethylene-vinyl alcohol copolymers, which are derived from high molecular weight ethylene-vinyl ester copolymers with a weight average molecular weight Mw of> 100000 g / mol able iten, the temperature gradient is -0.1 ° C / min to -l ° C / min.

2. The method according to claim 1, characterized in that cooling is carried out to a temperature which is above the Tg of the solvent-containing ethylene-vinyl alcohol copolymer but is below the melting point of the ethylene-vinyl alcohol copolymer.

3. The method according to claim 1 or 2, characterized in that - in the high molecular weight ethylene-vinyl alcohol copolymers, first with a temperature gradient from -l ° C / min to -10 ° C / min, to a temperature of 40 ° C is cooled to 70 ° C, and then the cooling with a lower temperature gradient from -0.1 ° C / min to -l ° C / min up to a temperature of 10 ° C to 35 ° C is continued.

4. The method according to claim 1 to 3, characterized in that the precipitation of the ethylene-vinyl alcohol copolymer is supported by the addition of water.

5. The method according to claim 4, characterized in that the amount of water is 0.3 times to 5.0 times the amount by weight of the ethylene-vinyl acetate copolymer used.

6. The method according to claim 1 to 5, characterized in that the powder thus obtained is resuspended in water, solvent residues are optionally removed by distillation or stripping, and the pulverulent product is isolated by filtration.

7. ethylene-vinyl alcohol interpolymer obtainable by a process according to claims 1 to 6, with an ethylene content in the interpolymer of 5 to 75 mol%.

8. ethylene-vinyl alcohol copolymers according to claim 7 with a grain size, determined as the average volume diameter Dv, of 20 to 2000 microns.

9. ethylene-vinyl alcohol copolymers according to claim 7 or 8 with a complex melt viscosity of 0.5 to 100000 Pas (at 180 ° C; oscillating measurement at 1 Hz with plate / plate measuring system).

10. Use of the ethylene-vinyl alcohol copolymers according to claims 7 to 9 for the production of foils, films and laminates.

11. Use of the ethylene-vinyl alcohol copolymers according to claims 7 to 9 for the production of moldings.

12. Use of the ethylene-vinyl alcohol copolymers according to claims 7 to 9 as a coating agent.

13. Use of the ethylene-vinyl alcohol copolymers according to claims 7 to 9 as an additive for powder coatings.

14. Use of the ethylene-vinyl alcohol copolymers according to claims 7 to 9 as an adhesive.

15. Use of the ethylene-vinyl alcohol copolymers according to claims 7 to 9 as binders in building materials.