DD294951B5 - Process for the preparation of modified ethylene-vinyl acetate copolymers - Google Patents

Description

The process according to the invention can be advantageously carried out by dividing the total amount of the solution of sodium methoxide in methanol required for the modification into two portions, and with the first dosage 0.014 to 0.04 mol of sodium methylate dissolved in 0.3 to 1.0 mol of methanol. in each case based on mol of vinyl acetate of the ethylene-vinyl acetate copolymer to be modified, and in the second dosage 0.005 to 0.03 mol of sodium, dissolved in 0.25 to 0.8 mol of methanol, in each case based on mol of vinyl acetate to be modified ethylene-vinyl acetate Copolymer, and in the second dosage 0.005 to 0.03 mol of sodium, dissolved in 0.25 to 0.8 mol of methanol, in each case based on mol of vinyl acetate of the ethylene-vinyl acetate copolymer to be modified, is used.

The modification of the ethylene-vinyl acetate copolymer takes place in extrusion machines, preferably in twin-screw extruders. The extruders must have two or more metering points for injecting the modifiers into the plastic melt. Following the modification reaction, degassing is required. Extruders with several degassing points are advantageous, wherein preferably at least one degassing point is located between the dosing points. Instead of the first modifier dosage, the ethylene-vinyl acetate copolymer must be melted. The distance from the first modifier dosage to the second modifier dosage or a first degassing, if it is between the two dosing, is an L / D ratio of at least 8 and the distance from the second Modifizordordosierung to the first and second degassing is a L / D ratio of at least 5. Injecting the modifiers at the appropriate metering points into the plastic melt takes place independently, optionally at different volumetric flow rates, and optionally differing in the concentration of sodium alkoxide. As modifiers, solutions of sodium alcoholates of C ₂ to Cs alcohols in the corresponding alcohol can also be used.

You can continue to contain low levels of sodium hydroxide. The ethylene-vinyl acetate copolymers to be modified are variable in their vinyl acetate content and have a melt index (at 463K and 21.2N) of a20g / 10min, preferably> 50g / 10min. Surprisingly, it has been found that the melt indices of the modified ethylene-vinyl acetate copolymers at the same concentration of sodium methylate in the plastic melt, regardless of the respective methanol concentration in the plastic melt, in the multiple dosing of the modifiers are higher than in the single dose. In addition, the Alkoholysegrade the modified ethylene-vinyl acetate copolymers at the same total concentration of the reactants in the plastic melt with multiple dosing of the modifiers are higher than in the single dose. When using the multiple dosing, the Natriummethylatkonzentration in the plastic melt can be lowered so that higher melt indices are adjustable at defined Alkoholysegraden the modified ethylene-vinyl acetate copolymers, which is particularly advantageous at high Alkoholysegraden.

As a result of the multiple dosing of the modifiers, brighter products are also obtained, in particular when degassing is interposed. Downstream of the extruder may be one or more static mixers, which are useful for the homogeneity of the modified ethylene-vinyl acetate copolymers, and which may optionally be followed by a degassing device. The products according to the invention are obtained with a melt index in the range between 0.1 to 30 g / 10 min (463 K, 21.2 N).

embodiments Determination of the melt index

The determination of the melt index is carried out according to TGL 25244 or DIN 53735.

Determination of degree of alcoholysis

The degree of alcoholysis is the percentage of reacted vinyl acetate based on the vinyl acetate content of the unmodified ethylene-vinyl acetate copolymer. The vinyl acetate content of the unmodified and the modified ethylene-vinyl acetate copolymer is determined by completely saponifying the products with an excess of ethanolic potassium hydroxide solution and by titrating back the excess liquor.

test equipment

According to TGL 8418/7, additionally hydrochloric acid pa C _(H ci) = 0,5 mol / l and alkali blue, ethanolic solution 1 %.

execution

About 1 g of the sample is weighed on the analytical balance with a maximum uncertainty of 0.001 g and then placed in a 300 ml flask. Add 20ml of xylene and some boiling stones. Thereafter, the sample is dissolved by heating. After cooling, 20 ml KOH С ( _КО ні = 0,5 mol / l) are added to the solution and the solution is refluxed for 3 hours After saponification, the reflux condenser is rinsed with 20 ml ethanol, and after re-boiling, the solution receives some Dropwise addition of 1% strength ethanolic alkali blue solution is followed by titration with ethanolic HCl C (hcd ⁼ 0.5 mol / l) dropwise to blue color change in the same way.

Vinyl acetate content in%

a = consumption of KOH in ml

b = consumption of KOH by both titration in ml

F = factor of KOH

E = weight in mg

example 1

An ethylene-vinyl acetate copolymer having a vinyl acetate content of 32.5% by weight and a melt index of 150 g / 10 min (463K, 21.2 N) is metered into the feed zone of a twin-screw extruder via a weighfeeder. The twin-screw extruder has an L / D ratio of 43. The extrusion and the modification of the ethylene-vinyl acetate copolymer is carried out at heating zone temperatures of 393 K to 463 K, a screw speed of 150 min " ¹ and a product throughput of 30 kg / h.

After a L / D ratio of 12, the dosage of methanolic sodium methylate solution is used as a modifier. The sodium content of the solution is 1.0% by weight in%. The amount of modifier injected corresponds to a molar ratio of sodium methoxide to vinyl acetate of the ethylene-vinyl acetate copolymer of 0.014 and a ratio of methanol to vinyl acetate of 1.0.

After an L / D ratio of 22, volatile components are removed from the plastic melt by means of vacuum degassing. At an L / D ratio of 30, methanolic sodium methylate solution having a sodium content of 1.2 mass% is injected into the plastic melt. The modifier amount at this point corresponds to a molar ratio of sodium methoxide to vinyl acetate of the ethylene-vinyl acetate starting polymer of 0.014 and a molar ratio of methanol to vinyl acetate of 0.8. At an L / D ratio of 36, a new vacuum degassing takes place. The modified plastic strands leaving the extruder are cooled, granulated and dried. The melt index and the degree of alcoholysis of the modified copolymer are listed in the table.

Example 2 (comparative example)

An ethylene-vinyl acetate copolymer according to Example 1 is metered via a belt feeder into the feed zone of a twin-screw extruder with a total L / D ratio of 43. The temperature profile, the screw speed and the product throughput correspond to Example 1. *

After an L / D ratio of 12, the dosage of methanolic Natriummethylatlösung, which has a sodium content of 1.1 parts by weight in%. The injected amount corresponds to a molar ratio of sodium methoxide to vinyl acetate of the ethylene-vinyl acetate copolymer of 0.028 and a molar ratio of methanol to vinyl acetate of 1.8. At L / D ratios of 30 and 36, each devolatilization of the plastic melt occurs by vacuum degassing.

The cooling, granulation and drying of the modified copolymer are carried out according to Example 1. The melt index and the degree of alcoholysis of the modified copolymer are listed in the table.

Example 3

An ethylene-vinyl acetate copolymer according to Example 1 is modified according to this. The modifier used at both metering points is methanolic sodium methoxide solution with a sodium content of 2.7% by weight in%. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

Example 4 (Comparative Example)

An ethylene-vinyl acetate copolymer according to Example 1 is modified according to Example 2. The modifier corresponds to Example 3. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

Example 5

An ethylene-vinyl acetate copolymer according to Example 1 is modified according to this. The modifier used at both metering points is methanolic sodium methoxide solution with a sodium content of 3.45% by weight. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

Example 6 (comparative example)

An ethylene-vinyl acetate copolymer of Example 1 is modified according to Example 2. The modifier corresponds to Example 5. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

Example 7

An ethylene-vinyl acetate copolymer according to Example 1 is modified according to this. The modifier used at both metering points is methanolic sodium methoxide solution with a sodium content of 6.1% by weight in%. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

Example 8 (Comparative Example)

An ethylene-vinyl acetate copolymer according to Example 1 is modified according to Example 2. The modifier corresponds to Example 7. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

Examples

An ethylene-vinyl acetate copolymer according to Example 1 is modified according to this. The modifier used at the 1 .Dosierstelle methanolic sodium methoxide solution with a sodium content of 4.3 parts by mass in% and at the 2nd dosing methanolic solution of sodium methoxide with a sodium content of 1.4 parts by mass in%. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

Example 10 (Comparative Example)

An ethylene-vinyl acetate copolymer according to Example 1 is modified according to Example 2. The modifier used is methanolic sodium methoxide solution with a sodium content of 3.0% by weight. The molar ratios of the reactants and the characteristics of the modified copolymer are listed in the table.

table

1st dosage Molar ratio of the reactants ChaoNa / Vac СНзОН / Ѵас melt index alcoholysis Ex. CH ₃ ONaAZaC 2nd dosage 0,014 0.8 (G / IOmin) (%) 0,014 СНэОН / Ѵас - - 29.5 97.5 1 0.028 1.0 0.024 0.6 21.0 70.0 2 0.04 1.8 - - 0.1 98.0 3 0.064 1.0 0,022 0.43 0.05 72.0 4 0.03 1.6 - - 2.0 85.0 5 0,052 0.57 0.03 0.3 0.12 68.0 6 0.03 1.0 - - 0.15 51.0 7 0.06 0.3 0.005 0.25 0.06 45.0 8th 0.02 0.6 - - 30.0 50.0 9 0,025 0.3 21.0 39.5 10 0.55

Claims (3)

1. A process for the preparation of modified ethylene-vinyl acetate copolymers having Alkoholysegraden from 50 to 98% and improved processing behavior, wherein the modification of the copolymers by dosing solutions of sodium alcoholates in the corresponding alcohol, which optionally 0.03 to 4.45 parts by weight in% Sodium hydroxide, carried out at temperatures of 343 to 493K in an extrusion machine, characterized in that the metering of the modifier solutions into the plastic melt occurs at more than one point along the extrusion machine, with a total concentration of the reactants of 0.01 to 0.38 moles of sodium alcoholate and 0 , 5 to 2,8mol alcohol, in each case based on mol of vinyl acetate of the ethylene-vinyl acetate copolymer to be modified, is used. 2. The method according to claim 1, characterized in that solutions of sodium methoxide are used in methanol. 3. The method according to claim 1 and 2, characterized in that the total amount of required for the modification of sodium methylate solution in methanol is divided into two portions, and in the first dosage 0.014 to 0.04mol sodium, dissolved in 0.3 to 1, 0mol methanol, in each case based on mol of vinyl acetate of the ethylene-vinyl acetate copolymer to be modified, and in the second dosage 0.005 to 0.03 mol of sodium, dissolved in 0.25 too, 8mol methanol, each based on mol of vinyl acetate of the ethylene to be modified Vinyl acetate copolymer into which plastic melt is injected. Field of application of the invention The invention relates to a process for the preparation of organometallic modified ethylene-vinyl acetate copolymers having a variable property profile. Characteristic of the known state of the art It is known that modified vinyl ester-containing olefin copolymers are reacted with alcohol-containing metal alcoholates or solutions of metal alcoholates in the corresponding alcohol in the plastic melt at melting temperatures of 343 to 493 K. In this case, it is possible to obtain selectively partially or totally crosslinked products whose vinyl ester groups have been replaced by hydroxyl groups by 5 to 95% (DD 206900). The influencing of the simultaneously juxtaposed alcoholysis and crosslinking reaction takes place by varying the residence time of the alcohol in the plastic melt and by removing defined proportions of alcohol. To improve the homogeneity of ethylene-vinyl acetate copolymers modified in this way, from 03 to 4.45 parts by weight in% sodium hydroxide may be added to the modifier O (DD 243287). According to the process described, it is not possible to produce modified ethylene-vinyl acetate copolymers having a high degree of alcoholysis and a melt index which can be varied over a wide range. In particular, it is not possible. To produce copolymers having a melt index in the range of 0.1 to 30g / 10 min and a degree of alcoholysis over 75%, so that the known products are limited in their Veriteleεitbarkeit. Object of the invention The aim of the invention is the preparation of crosslinked hydroxyl-containing ethylene-vinyl acetate copolymers having improved processability. Explanation of the essence of the invention The object of the invention is to carry out the modification of ethylene-vinyl acetate copolymers with sodium alcoholates in the corresponding alcohol so that the extent of the crosslinking reaction is reduced. This object is achieved by a process for the preparation of modified ethylene-vinyl acetate copolymers having Alkoholysegraden from 50 to 98% and improved processing behavior, wherein the modification of the copolymers by metering solutions of sodium alcoholates in the corresponding alcohol, which optionally 0.03 to 4.45 % By weight of sodium hydroxide, carried out at temperatures of 343 to 493 K in an extrusion machine, dissolved by the invention according to the dosage of the modifier solutions in the plastic melt at more than one point along the extrusion machine, wherein a total concentration of the reactants from 0.01 to 0 , 08mol sodium alcoholate and 0.5 to 2.8 moles of alcohol, in each case based on mol of vinyl acetate of the ethylene-vinyl acetate copolymer to be modified, is used. As modifier solutions, solutions of sodium methylate in methanol are preferably used. "