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GB1593341A - Process for the hydrolysis of ethylene/vinyl acetate copolymers - Google Patents

Process for the hydrolysis of ethylene/vinyl acetate copolymers Download PDF

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Publication number
GB1593341A
GB1593341A GB47378A GB47378A GB1593341A GB 1593341 A GB1593341 A GB 1593341A GB 47378 A GB47378 A GB 47378A GB 47378 A GB47378 A GB 47378A GB 1593341 A GB1593341 A GB 1593341A
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Prior art keywords
vinyl acetate
weight
copolymer
ethylene
methanol
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BASF SE
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BASF SE
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    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00Chemical modification by after-treatment
    • C08F8/12Hydrolysis
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2800/00Copolymer characterised by the proportions of the comonomers expressed
    • C08F2800/20Copolymer characterised by the proportions of the comonomers expressed as weight or mass percentages
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2810/00Chemical modification of a polymer
    • C08F2810/50Chemical modification of a polymer wherein the polymer is a copolymer and the modification is taking place only on one or more of the monomers present in minority

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Description

(54) PROCESS FOR THE HYDROLYSIS OF ETHYLENE/VINYL ACETATE COPOLYMERS (71) We, BASF AKTIENGESELL SCHAFT, a German Joint Stock Company of 6700 Ludwigshafen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement: The present invention relates to a process for the hydrolysis of ethylene/vinyl acetate copolymers.
In this process, an ethylene/vinyl acetate copolymer which contains from 12 to 40 per cent by weight of vinyl acetate and from 60 to 88 per cent by weight of ethylene as copolymerized units, the sum of the percentages by weight being 100, and which has a melt index of from 0.1 to 400 g/10 min, is hydrolyzed in a monohydric alcohol of 1 to 4 carbon atoms or in a mixtures of two or more of these alcohols, by means of an akali metal hydroxide or alkali metal alcoholate.
This generally results in hydrolysis of from 10 to 99 per cent, preferably from 50 to 99 per cent, of the hydrolyzable ester groups of the copolymerized vinyl acetate units.
It is known that such a hydrolysis reaction produces copolymers which in addition to ethylene and vinyl acetate contain vinyl alcohol as copolymerized units.
The literature discloses processes in which ethylene and vinyl acetate are copolymerized by a free radical mechanism in a liquid homogeneous phase which essentially comprises ethylene, vinyl acetate and a solvent, for example methanol or tert.-butanol. After removing the unconverted vinyl acetate the ethylene/vinyl acetate copolymers formed are partially hydrolyzed in solution, using alkaline catalysts.
Processes have also been disclosed in which ethylene/vinyl acetate copolymers are dissolved and then partially hydrolyzed in a homogeneous phase by means of alkali metal hydroxides or alkali metal alcoholates.
However, all these processes suffer from the disadvantage that the hydrolysis products have to be separated from the solvents used, by means of a relatively expensive and trouble-some process.
According to the present invention there is provided a process for the hydrolysis of an ethylene/vinyl acetate copolymer which contains from 12 to 40 per cent by weight of vinyl acetate and from 60 to 88 per cent by weight of ethylene as copolymerized units, the sum of the percentages by weight being 100 in every case, and which has a melt index of from 0.1 to 400 g/10 min, by reaction of the ethylene/vinyl acetate copolymer with an alkali metal hydroxide or alkali metal alcoholate in a monohydric alcohol of 1 to 4 carbon atoms or a mixture of two or more such alcohols, wherein the ethylene/vinyl acetate copolymer is hydrolyzed for a residence time of 1 to 30 hours, in the form of solid particles having diameters of from 0.1 to 8 mm suspended in from 1 to 5 parts by weight of the alcohol or alcohol mixture per part by weight of copolymer, at a temperature below the softening point of the copolymer and in the presence of from 1 to 20 g per kg of copolymer of a low molecular weight compound containing one or more basic nitrogen atoms.
By means of the present invention it is possible to obtain a homogeneous and colorless hydrolysis product in a technically simple and economical manner.
In a preferred embodiment, the copolymer particles have a diameter of from 1 to 5 mm.
In a particularly preferred embodiment methanol is employed as the alcohol. In another preferred embodiment, the hydrolysis is carried out in the presence of from 2 to 15 g per kg of copolymer of the compound containing one or more basic nitrogen atoms, preferably a hydroxylam monium salt.
The ethylene/vinyl acetate copolymers to be hydrolyzed are disclosed in the literature and may be manufactured by conventional processes. For example, they may be obtained by copolymerizing ethylene with vinyl acetate at pressures of from 1 ,000 to 3,000 bars and at from 150 to 400 C in the presence of free radical polymerization initiators. The conventional ethylene/vinyl acetate copolymers contain from 12 to 40 per cent by weight of vinyl acetate and from 60 to 88 per cent by weight of ethylene as copolymerized units, the sum of the percentages by weight always being 100. The melt index of the copolymers is from 0.1 to 400 g/10 min, preferably from 1 to 200 g/10 min, measured according to ASTM D 1238-65 T at 19() C under a load of 2.16 kp. The softening point of the copolymers is from about 35 to 1000C and is defined as the temperature at which the copolymers begin to exhibit viscous flow. Viscous flow is characterized by a drop in the modulus of shcar to values no longer measurable by a torsional vibration test. The temperature dependence of the modulus of shear is determined by a torsional vibration test as described in DIN 53,445.
Hydrolysis of the ethylene/vinyl acetate copolymers means scission of the hydrolyzable ester groups of the copolymerized vinyl acetate units, to give hydroxyl groups.
During the hydrolysis, generally from 10 to 99, preferably from 50 to 99, per cent by weight of the ester groups of the copolyme- rized vinyl acetate units undergo scission, resulting in a copolymer which contains vinyl alcohol as copolymerized units in addition to ethylene and vinyl acetate copolymerized units. The hydrolysis of ethylene/vinyl acetate copolymers is a conventional process in polymer chemistry. In this process, the ethylene/vinyl acetate copolymer is dissolved and reacted with alkali metal hydroxides, e.g. sodium hydroxide or potassium hydroxide, or with alkali metal alcoholates, e.g. sodium methylate or ethylate or potassium methylate or ethylate, so as to undergo the above scission. After the hydrolysis, the hydrolyzed copolymer obtained still remains in solution in the solvent employed and must be separated from the latter, for example by evaporating the solvent. Such a process is described in, for example, German Patent 1203,958.
Using a process within the invention, the ethylene/vinyl acetate copolymer is hydrolyzed whilst suspended in the form of solid particles in a limited amount of an alcohol of 1 to 4 carbon atoms as the reaction medium.
For this purposc, copolymer particles having particle sizes of from 0.1 to 8 mm, preferably from 1 to 5 mm, are suspended in from 1 to 5, preferably from 3 to 5, parts by weight of alcohol per part by weight of copolymer and are hydrolyzed with an alkali metal hydroxide or alkali metal alcoholate.
Accordingly, in the present process the copolymer particles are not dissolved in a solvent, but suspended or dispersed, in a more or less finely divided form, in the reaction medium. The temperature of the latter is from 30 to 95"C and is selected so that it is always below the softening point of the copolymer particles present in the reaction mixture, and so that these particles do not undergo solution.
Suitable reaction media are monohydric alcohols of 1 to 4 carbon atoms and mixtures of these alcohols in which the copolymers to be employed according to the invention are insoluble under the selected reaction conditions. The use of methanol is particularly advantageous in respect of economy and of the properties of the products obtained.
Suitable hydrolytic agents are alkali metal hydroxides, e.g. NaOH and KOH, and alkali metal methylates and ethylates, e.g.
sodium methylate and potassium ethylate.
The hydrolytic agents may be employed in excess, in the stoichiometric amount, or in less than the amount which stoichiometrically corresponds to the copolymerized vinyl acetate. They may be added as solids or as a solution in alcohol, all at once, in portions or continuously. When using NaOH or KOH, it has proved particularly advantageous to employ amounts equivalent to the amount of vinyl acetate to be hydrolyzed. The desired degree of hydrolysis can be obtained particularly readily in this way.
The main reaction products formed in addition to the hydrolyzed copolymers are the corresponding acetates; a small amount of methyl acetate is also formed. In the case of, for example, sodium methylate, the hydrolysis of the ethylene/vinyl acetate copolymers in the main occurs via a transesterification mechanism which involves the formation of methyl acetate. The sodium methylate in this case acts as a catalyst.
However, as a rule methanol contains small proportions of water, which reacts with sodium methylate to give NaOH and methanol, so that some sodium methylate is consumed, the amount depending on the water content of the methanol and of the copolymer. The use of from 1/20 to 1/3 of the stoichiometric amount of sodium methylate has therefore proved particularly advantageous.
The hydrolysis may be carried out at temperatures up to the softening point of the alcohol-saturated copolymer, which softening point depends on the degree of hydrolysis. Since the softening points of the hydrolyzed copolymers are higher than those of the ethylene/vinyl acetate copolymers employed, the reaction temperature can be raised in the course of the reaction.
Preferably, the reaction is carried out at from 50 to 90"C.
When hydrolyzing the ethylene/vinyl acetate copolymers, the latter are preferably employed in the form of granules. A residence time of the reactants in the reaction zone of from 1 to 30 hours, is required to enable the reaction medium to penetrate into the granules. The residence time depends on the size of the granules, the reaction temperature, the amount of copolymerized vinyl acetate units and the desired degree of hydrolysis.
From 1 to 20 g, per kg of copolymer, of one or more low molecular weight compounds containing one or more basic nitrogen atoms eg. h droxylammonium salts, hydrazinium salts for example the sulfates or chlorides), butylamines or ethylenediamine, are added to the reaction mixture.
In a particularly preferred embodiment, from 2 to 15 g of one or more hydroxylammonium salts are added to the reaction mixture per kg of copolymer. By adding the stated amount of these agents it is possible greatly to reduce the amount of alcohol otherwise required to produce colorless products, for example so that instead of from 3 to 8 parts by weight of methanol being required for best results per part by weight of copolymer from 1 to 5 parts by weight are now adequate. Furthermore, the reaction takes place more rapidly because of the resulting higher concentration of the hydrolytic agent, so that overall a substantial increase in the output of hydolyzed product per unit volume can be achieved.
The advantage achieved by means of the invention is in particular that the partially or completely hydrolyzed ethylene/vinyl acetate copolymer may be isolated in a technically simple and economical manner, for exammple by sieving or centrifuging, since the original particle shape has been retained during hydrolysis.
The outstanding property of the hydrolyzed ethylene/vinyl acetate copolymers manufactured by a process within the invention is that the colorless hydrolysis products exhibit a surprising and completely unexpected homogeneity, so that the virtually speck-free films having a thickness of about 5 m can be produced from such products.
Embodiments of the invention will now be described with reference to nonlimitative Examples.
Example 1 A 1 liter stirred autoclave is charged with 150 g of granules, of 1.5 mm diameter, of an ethylene/vinyl acetate copolymer containing 30% by weight of copolymerized vinyl acetate units and having a melt index (190"C/2.16 kg) of 20g/10 min, together with 450 g of methanol (containing 700 ppm of water), with 5.7 g of sodium methylate, which amount is equivalent to 1/5 of the vinyl acetate units, and 0.6 g of hydroxylammonium chloride. The temperature is raised to 85"C in the course of 6 hours and is left thereat for 3 hours. The granules are filtered off, washed with a little methanol, extracted for 4 hours with 450 g of methanol at 650C and then dried at 70"C under reduced pressure. 129 g of a colorless hydrolysis product containing 17.5% by weight of vinyl alcohol units and 1.2% by weight of vinyl acetate units are obtained; the melt index (190"C/2.16 kg) is 16 g/10 min.
Example 2 A 2 liter flask equipped with a stirrer and reflux condenser is charged with 400 g of granules, of 2 mm diameter, of an ethylene/ vinyl acetate copolymer containing 35% by weight of copolymerized vinyl acetate units and having a melt index (190"C/2.16 kg) of 112 g/10 min, together with 800 g of methanol (methanol:granules ratio = 2:1), 109 g of 85% strength KOH and 2 g of hydroxylammonium chloride. The reaction temperature is kept for 1.5 hours at 550C and is then raised to the reflux temperature. After a total time of 10 hours the granules are filtered off, washed with a little methanol and then extracted for 4 hours with 800 g of methanol under reflux. After drying at 70"C under reduced pressure, 334 g of completely colorless hydrolysis product containing 20.9% by weight of vinyl alcohol units and 1.4% by weight of vinyl acetate units are obtained; the melt index (190"C/2.16 kg) is 43 g/10 min.
Example 3 A 1 liter stirred autoclave is charged with 150 g of granules, of 3 mm diameter, of an ethylene/vinyl acetate copolymer containing 28.5% by weight of copolymerized vinyl acetate units and having a melt index 1900 C/2.16 kg) of 5 g/10 min, together with 450 g of methanol (methanol:granules ratio = 3:1), 21 g of 97% strength NaOH and 0.9 g of hydroxylammonium chloride. The temperature is raised to 90"C in the course of 3 hours and kept thereat for 8 hours. The granules are filtered off, washed with a little methanol and then extracted for 4 hours with 450 g of methanol in the autocalve at 90"C. After drying at 70"C under reduced pressure, 129 g of completely colorless hydrolysis product containing 15.9% by weight of vinyl alcohol units and 1.8% by weight of vinyl acetate units are obtained; the melt index (190"C/2.16 kg) is 5.6 g/10 main.
WHAT WE CLAIM IS: 1. A process for the hydrolysis of an ethylene/vinyl acetate copolymer which con
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. be raised in the course of the reaction. Preferably, the reaction is carried out at from 50 to 90"C. When hydrolyzing the ethylene/vinyl acetate copolymers, the latter are preferably employed in the form of granules. A residence time of the reactants in the reaction zone of from 1 to 30 hours, is required to enable the reaction medium to penetrate into the granules. The residence time depends on the size of the granules, the reaction temperature, the amount of copolymerized vinyl acetate units and the desired degree of hydrolysis. From 1 to 20 g, per kg of copolymer, of one or more low molecular weight compounds containing one or more basic nitrogen atoms eg. h droxylammonium salts, hydrazinium salts for example the sulfates or chlorides), butylamines or ethylenediamine, are added to the reaction mixture. In a particularly preferred embodiment, from 2 to 15 g of one or more hydroxylammonium salts are added to the reaction mixture per kg of copolymer. By adding the stated amount of these agents it is possible greatly to reduce the amount of alcohol otherwise required to produce colorless products, for example so that instead of from 3 to 8 parts by weight of methanol being required for best results per part by weight of copolymer from 1 to 5 parts by weight are now adequate. Furthermore, the reaction takes place more rapidly because of the resulting higher concentration of the hydrolytic agent, so that overall a substantial increase in the output of hydolyzed product per unit volume can be achieved. The advantage achieved by means of the invention is in particular that the partially or completely hydrolyzed ethylene/vinyl acetate copolymer may be isolated in a technically simple and economical manner, for exammple by sieving or centrifuging, since the original particle shape has been retained during hydrolysis. The outstanding property of the hydrolyzed ethylene/vinyl acetate copolymers manufactured by a process within the invention is that the colorless hydrolysis products exhibit a surprising and completely unexpected homogeneity, so that the virtually speck-free films having a thickness of about 5 ssm can be produced from such products. Embodiments of the invention will now be described with reference to nonlimitative Examples. Example 1 A 1 liter stirred autoclave is charged with 150 g of granules, of 1.5 mm diameter, of an ethylene/vinyl acetate copolymer containing 30% by weight of copolymerized vinyl acetate units and having a melt index (190"C/2.16 kg) of 20g/10 min, together with 450 g of methanol (containing 700 ppm of water), with 5.7 g of sodium methylate, which amount is equivalent to 1/5 of the vinyl acetate units, and 0.6 g of hydroxylammonium chloride. The temperature is raised to 85"C in the course of 6 hours and is left thereat for 3 hours. The granules are filtered off, washed with a little methanol, extracted for 4 hours with 450 g of methanol at 650C and then dried at 70"C under reduced pressure. 129 g of a colorless hydrolysis product containing 17.5% by weight of vinyl alcohol units and 1.2% by weight of vinyl acetate units are obtained; the melt index (190"C/2.16 kg) is 16 g/10 min. Example 2 A 2 liter flask equipped with a stirrer and reflux condenser is charged with 400 g of granules, of 2 mm diameter, of an ethylene/ vinyl acetate copolymer containing 35% by weight of copolymerized vinyl acetate units and having a melt index (190"C/2.16 kg) of 112 g/10 min, together with 800 g of methanol (methanol:granules ratio = 2:1), 109 g of 85% strength KOH and 2 g of hydroxylammonium chloride. The reaction temperature is kept for 1.5 hours at 550C and is then raised to the reflux temperature. After a total time of 10 hours the granules are filtered off, washed with a little methanol and then extracted for 4 hours with 800 g of methanol under reflux. After drying at 70"C under reduced pressure, 334 g of completely colorless hydrolysis product containing 20.9% by weight of vinyl alcohol units and 1.4% by weight of vinyl acetate units are obtained; the melt index (190"C/2.16 kg) is 43 g/10 min. Example 3 A 1 liter stirred autoclave is charged with 150 g of granules, of 3 mm diameter, of an ethylene/vinyl acetate copolymer containing 28.5% by weight of copolymerized vinyl acetate units and having a melt index 1900 C/2.16 kg) of 5 g/10 min, together with 450 g of methanol (methanol:granules ratio = 3:1), 21 g of 97% strength NaOH and 0.9 g of hydroxylammonium chloride. The temperature is raised to 90"C in the course of 3 hours and kept thereat for 8 hours. The granules are filtered off, washed with a little methanol and then extracted for 4 hours with 450 g of methanol in the autocalve at 90"C. After drying at 70"C under reduced pressure, 129 g of completely colorless hydrolysis product containing 15.9% by weight of vinyl alcohol units and 1.8% by weight of vinyl acetate units are obtained; the melt index (190"C/2.16 kg) is 5.6 g/10 main. WHAT WE CLAIM IS:
1. A process for the hydrolysis of an ethylene/vinyl acetate copolymer which con
tains from 12 to 40 per cent by weight of vinyl acetate and from 60 to 88 per cent by weight of ethylene as copolymerized units, the sum of the percentages by weight being 100 in every case, and which has a melt index of from 0.1 to 4()() g/lO min, by reaction of the ethylene/vinyl acetate copolymer with an alkali metal hydroxide or alkali metal alcohol ate in a monohydric alcohol of l to 4 carbon atoms or a mixture of two or more such alcohols. wherein the ethylene/vinyl acetate copolymer is hydrolyzed for a residence time of 1 to 3() hours, in the form of solid particles having diameters of from 0. l to 8 mm suspended in from 1 to 5 parts by weight of the alcohol or alcohol mixture per part by weight of copolymer, at a temperature below the softening point of the copolymer and in the presence of from 1 to 20 g per kg of copolymer of a low molecular weight compound containing one or more basic nitrogen atoms.
2. A process as claimcd in claim 1, wherein the copolymer particles have a diameter of from l to 5 mm.
3. A process as claimed in claim 1 or claim 2, wherein the copolymer particles are suspended in methanol, for the hydrolysis.
4. A process as claimed in any one of the preceding claims, wherein there is partial hydrolysis of the hydrolysable ester groups of the copolymer.
5. A process as claimed in any one of the preceding claims wherein the low molecular weight compound containing one or more basic nitrogen atoms is a hydroxylammonium or hydrazinium salt, a butylamine or ethylenediamine.
6. A process as claimed in claim 5, wherein a hydroxyl-ammonium salt is used in an amount of from 2 to 15 g per kg of copolymer.
7. A process as claimed in any of the preceding claims, wherein the copolymer has a melt index of from 1 to 200 g/10 min and a softening point of from 35 to 1000C.
8. A process for hydrolysing an ethylene/vinyl acetate copolymer carried out substantially as described in any of the foregoing Examples.
9. An at least partially hydrolyzed ethylene/vinyl acetate copolymer when obtained by a process as claimed in any of the preceding claims.
10. A copolymer as claimed in claim 9, in which from 50 to 99 per cent of the vinylic units are vinyl alcohol units.
GB47378A 1977-01-08 1978-01-06 Process for the hydrolysis of ethylene/vinyl acetate copolymers Expired GB1593341A (en)

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DE19772700607 DE2700607C2 (en) 1977-01-08 1977-01-08 Process for the partial saponification of ethylene-vinyl acetate copolymers

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GB1593341A true GB1593341A (en) 1981-07-15

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BE (1) BE862732A (en)
DE (1) DE2700607C2 (en)
FR (1) FR2376878A1 (en)
GB (1) GB1593341A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8301740A (en) * 1982-05-25 1983-12-16 Kuraray Co PROCESS FOR PREPARING A SOAPY PRODUCED ETHYL VINYL ACETATE COPOLYMER

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD243287A1 (en) * 1985-12-16 1987-02-25 Leuna Werke Veb METHOD FOR PRODUCING MODIFIED ETHEN-VINYL ACETATE COPOLYMERS
EP3181597A1 (en) * 2015-12-15 2017-06-21 Evonik Degussa GmbH Preparation method of poly(vinyl alcohol) and of an ethylene-vinylalcohol copolymer

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2862916A (en) * 1955-08-22 1958-12-02 Celanese Corp Production of polyvinyl alcohol
GB1095204A (en) * 1966-01-07 1967-12-13 Monsanto Chemicals Production of polymers containing hydroxyl groups
DE1595376A1 (en) * 1966-01-18 1970-04-23 Stockhausen & Cie Chem Fab Process for the production of disperse, completely or partially saponified ethylene-vinyl acetate copolymers
DE1809757A1 (en) * 1968-11-19 1970-05-21 Du Pont Suspension alcoholysis of ethylene vinyl ester copoly- - mers

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8301740A (en) * 1982-05-25 1983-12-16 Kuraray Co PROCESS FOR PREPARING A SOAPY PRODUCED ETHYL VINYL ACETATE COPOLYMER

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FR2376878B1 (en) 1983-03-11
FR2376878A1 (en) 1978-08-04
BE862732A (en) 1978-07-06
DE2700607A1 (en) 1978-07-13
DE2700607C2 (en) 1982-10-14
JPS5385888A (en) 1978-07-28

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