DD294951A5 - Process for the preparation of modified ethylene-vinyl acetate copolymers - Google Patents

Abstract

The aim is the preparation of modified ethylene-vinyl acetate copolymers with improved feedability. Products with alcohol degrees of between 50 and 98% and melt indices in the range of 0.1 to 30 g / 10 min are extruded by metering solutions of sodium alcoholates in the corresponding alcohol into an extrusion machine in which the copolymer to be modified is extruded at 343 to 493 K, obtained by the dosage of the modifier solution, preferably sodium methylate in methanol, in the plastic melt in more than one place, preferably two, along the extrusion machine, wherein a total concentration of the reactants from 0.01 to 0.08 mol of sodium alcoholate and 0.5 to 2.8 mol of alcohol, in each case based on mol of vinyl acetate of the copolymer used, is used {ethylene-vinyl acetate copolymer, crosslinked, containing hydroxyl groups; processability; Melt Index; alcoholysis; sodium alcoholate; Alcohol; Dosage; Extrusion machine}

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 copolymeriim to be modified, and in the second metering 0.005 to 0.03 mol of sodium methylate dissolved in 0.25 to 0.8 mol of methimole, in each case based on mol of vinyl acetate of the ethylene compound to be modified Vinyl acetate copolymer, and in the second Dosif tion 0.005 to 0.03 moles of sodium, dissolved in 0.25 to 0.8 moles of methanol, each based on moles of vinyl acetate to be modified ethylene-vinyl acetate copolymer 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 bulk mill. 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. The ethylene-vinyl acetate copolymer must be melted at the site of the first modifier dosage. 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. Other suitable modifiers are solutions of sodium alcoholates of C ₂ to C ₆ alcohols in the corresponding alcohol.

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 2: 20g / 10min, preferably 25OgAlOmIn. 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 Plastschmelzo, are higher in the multiple dosing of modifiers 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).

Ausführungsbelsplele

Determination of melt index

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

Determination of the 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 _mi) = 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 of KOH C (kOH> = 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 of ethanol and, after boiling again, the solution is obtained A drop of a 1% strength ethanolic alkali solution is then added, followed immediately by dripping back to blue with ethanolic HCl _(H ai 0.5 mol / l) until the color changes to the same color. A blank value determination is carried out in the same way.

Vinyl acetate content in%

a = consumption of KOH in ml

b = consumption of KOH in the titrimetric blank determination in ml

F = factor of KOH

E = weight in mg

example 1

An ethylene-vinyl acetate copolymer acetate 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 modification of the ethylene-vinyl acetate copolymer is carried out at heating zone temperatures of 393K to 463K, a screw speed of 150 minutes and a product throughput of 30 kg / hr.

After an 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 copolymers are listed in the table.

Example 2 (Verglelchsbelsplel) An ethylene-vinyl acetate copolymer according to Example 1 is fed via a feeder in the feed zone of a Twin screw extruder with a total L / D ratio of 43 dosed. The temperature profile, the screw speed and

the product throughput corresponds to Example 1. "

After an L / D ratio of 12, the dosage of methanolic sodium methylate solution, which is a sodium content

of 1.1 mass%. The injected amount corresponds to a molar ratio of sodium methylate to vinyl acetate of

Ethylene-vinyl acetate copolymer of 0.028 and a molar ratio of methanol to vinyl acetate of 1.8. For L / D ratios

from 30 and 36, the removal of volatile constituents from the plastic melt takes place by vacuum degassing.

The cooling, granulation and drying of the modified copolymer is 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 (Verfllchebelsplel) An ethylene-vinyl acetate copolymer according to Example 1 is modified according to Example 2. The modifier corresponds Example 3. The molar ratios of the reactants and the characteristics of the modified copolymer are in the table

listed.

example

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 (Interlibrary play) An ethylene-vinyl acetate copolymer according to Example 1 is modified according to Example 2. The modifier corresponds Example 5. The molar ratios of the crude sands and the characteristics of the modified copolymer are in the table

listed.

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

listed.

Example 9 An ethylene-vinyl acetate copolymer according to Example 1 is modified according to this. As a modifier serves at the

1. Dosage point methanolic sodium methoxide solution with a sodium content of 4.3 parts by mass in% and at the

2. Dosage point methanolic sodium methoxide solution 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 (Companion Belsplel)

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

I.Dosierung Molar ratio of the reactants CHjONa / Vac. CHjOH / Vac melt index alcoholysis Belep. CHjONe / Vac 2nd dosage 0,014 0.8 (g / 10 min) (%) 0,014 CH, OH / Vac - - 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 _t 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 β 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 in the plastic melt takes place at more than one point along the extrusion machine, wherein a total concentration of the reactants from 0.01 to 0.08 mol of sodium and 0.5 to 2.8 mol of 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 required for the modification of sodium methylate in methanol is divided into two subsets, and in the first dosage 0.014 to 0.04 mol of sodium, 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, each based on mol of vinyl acetate to be modified ethylene-vinyl acetate copolymer, are injected into the plastic melt. Field of application & 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 493K. In this case, it is possible to obtain selectively partially or totally crosslinked products whose vinyl ester groups have been replaced by hydroxyl groups of 6 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, it is possible to add to the modifier 0.03 to 4.45 parts by weight in% sodium hydroxide (DD 243 287). 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 30 g / 10 min and a degree of alcoholysis of more than 75%, so that the known products are limited in their processability. 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 in such a way that the extent of the crosslinking reaction is reduced. This object is achieved by a Verfa.'iren for the preparation of modified ethylene-vinyl acetate copolymers having Alkoholysegraden from BO 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 parts by mass contained in% sodium hydroxide, carried out at temperatures of 343 to 493K in an extrusion machine, dissolved by the invention according to the metering of the modifier solutions in the plastic melt at more than one point along the extrusion machine, wherein a total concentration of the reactants of 0.01 to 0.08 mol of 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 methoxide in methanol are preferably used.