TW202225209A - Modified ethylene-vinyl alcohol-based copolymer, method for manufacturing the same, and molded article including the same - Google Patents

Abstract

This invention relates to modified ethylene-vinyl alcohol-based copolymer, a method for manufacturing the same, and a molded article including the same. Specifically, according to one embodiment of the invention, there is provided modified ethylene-vinyl alcohol-based copolymer, comprising ethylene-derived first repeat units; vinyl alcohol-derived second repeat units; and tetraethyl orthosilicate(TEOS)-derived third repeat units.

Description

Modified ethylene/vinyl alcohol-based copolymer, method for producing the same, and molded article including the same

The present invention relates to a modified ethylene-vinyl alcohol-based copolymer, a method for producing the same, and a molded article including the same. Cross-reference of related application(s)

This application claims Korean Patent Application No. 10-2020-0134426 filed with the Korean Intellectual Property Office on October 16, 2020 and Korean Patent Application No. 10-2021-0127979 filed on September 28, 2021 The disclosures of these cases are hereby incorporated by reference in their entirety.

Ethylene-vinyl alcohol (EVOH) has excellent gas barrier properties, transparency, mechanical properties, and the like, and thus is widely used as a material for films, sheets, home meal replacement containers, and the like.

However, due to the presence of hydroxyl groups (-OH groups) in the molecule, ethylene-vinyl alcohol exhibits high gas barrier properties in the dry state, but under humid conditions, water vapor is absorbed and the gas permeability increases rapidly.

To compensate for such moisture-sensitivity, a method of co-extrusion of ethylene-vinyl alcohol with polyolefin (PO) to make multilayer molded articles, a method of preparing ethylene-vinyl alcohol using polyfunctional starters followed by saponification, etc. The method of vinyl acetate (EVA).

However, in the case of co-extrusion of polyolefins having a process window incompatible with ethylene-vinyl alcohol, gelation may occur to deteriorate processability, mechanical properties, etc., or fisheyes may be formed on the surface ( fish eye), streaks, etc., thus reducing the appearance quality of the molded article.

Meanwhile, in the case of using a multifunctional initiator, suitable comonomers, polymerization conditions, etc. should be found, and when the polymerized EVA-based copolymer is saponified under unsuitable conditions, the process efficiency may be reduced.

[technical problem]

An object of the present invention is to increase molecular weight, complex viscosity and viscoelasticity by controlling the structure of the ethylene-vinyl alcohol-based copolymer, and to improve the processability, mechanical properties, etc. of molded articles. [Technical solutions]

Specifically, according to an embodiment of the present invention, a modified ethylene-vinyl alcohol-based copolymer is provided, which comprises: a first repeating unit derived from ethylene; a second repeating unit derived from vinyl alcohol; The third repeating unit of tetraethyl silicate (TEOS).

According to another embodiment of the present invention, there is provided a method for producing a modified ethylene-vinyl alcohol-based copolymer of an embodiment, which comprises reacting the ethylene-vinyl alcohol-based copolymer with tetraethyl orthosilicate step.

According to yet another embodiment, there is provided a molded article including the modified ethylene-vinyl alcohol-based copolymer of an embodiment. [Beneficial effect]

Compared with the ethylene-vinyl alcohol-based copolymer that does not contain the third repeating unit, the modified ethylene-vinyl alcohol-based copolymer of a specific example can have high molecular weight, complex viscosity and viscoelasticity, but also has excellent flexibility, Rigidity and melt strength.

In addition, the production method of a specific example corresponds to the preparation of ethylene-vinyl alcohol-based copolymers followed by post-modification, and does not require introduction of catalysts, solvents, etc., so low-cost and high-efficiency process operations can be realized, And the quality of the final product is diversified according to the quality of the ethylene-vinyl alcohol-based copolymer.

In addition, since the molded article of a specific example includes the modified ethylene-vinyl alcohol-based copolymer having excellent flexibility, rigidity, and melt strength, it may have excellent processability and mechanical properties.

The terminology used herein is used to describe specific examples only, and is not intended to limit the present invention. Singular expressions include their plural expressions unless explicitly stated or obvious from the context that this is not the case. As used herein, the terms "comprising", "provided with" or "having" etc. are intended to specify the presence of features, numbers, steps, structural elements or combinations thereof of the practice, and they are not intended to exclude one or more other features, The presence or addition of numbers, steps, structural elements, or combinations thereof.

While the invention is capable of various modifications and of various forms, specific embodiments will be illustrated and described in detail below. However, it should be understood that these are not intended to limit the present invention to the specific disclosure, and that the present invention includes all modifications, equivalents or substitutions without departing from the spirit and technical scope of the present invention.

Hereinafter, specific examples of the present invention will be described in detail. Modified ethylene - vinyl alcohol copolymer

According to a specific example of the present invention, a modified ethylene-vinyl alcohol-based copolymer is provided, comprising: a first repeating unit derived from ethylene; a second repeating unit derived from vinyl alcohol; The third repeating unit of ethyl ester (TEOS).

Compared with the ethylene-vinyl alcohol-based copolymer that does not contain the third repeating unit, the modified ethylene-vinyl alcohol-based copolymer can have high molecular weight, complex viscosity and viscoelasticity, but also has excellent flexibility, rigidity and melting point. body strength.

Specifically, a modified ethylene-vinyl alcohol-based copolymer of one specific example can be produced by reacting an ethylene-vinyl alcohol-based copolymer with tetraethyl orthosilicate.

In this regard, the first repeating unit and the second repeating unit may be derived from an ethylene-vinyl alcohol-based copolymer, respectively, and the third repeating unit may be derived from tetraethylorthosilicate.

In this reaction, tetraethyl orthosilicate can act as a crosslinking agent. Specifically, tetraethyl orthosilicate mediates partial cross-linking within ethylene-vinyl alcohol-based copolymer molecules, as well as cross-linking between different ethylene-vinyl alcohol-based copolymer molecules, and may increase the final product (i.e., , the molecular weight of modified ethylene-vinyl alcohol copolymer).

In particular, long chain branches (LCBs) can be generated by cross-linking between different ethylene-vinyl alcohol-based copolymer molecules, thereby enhancing the flexibility, rigidity and melt strength of the final product, and ultimately improving Processability and mechanical properties of molded articles.

Hereinafter, a specific example of the modified ethylene-vinyl alcohol-based copolymer will be described in detail. repeating unit

As described above, the first repeating unit and the second repeating unit may be derived from the reactant ethylene-vinyl alcohol-based copolymer.

。 [化學式2]

。 In this regard, the first repeating unit may be represented by the following Chemical Formula 1, and the second repeating unit may be represented by the following Chemical Formula 2: [Chemical Formula 1]

. [Chemical formula 2]

.

Meanwhile, the third repeating unit may be derived from tetraethyl orthosilicate, a cross-linking agent, and may have an oxidation number of 1 to 4 according to the degree of reaction with the ethylene-vinyl alcohol-based copolymer.

[化學式3-2]

[化學式3-3]

[化學式3-4]

。 In this regard, the third repeating unit may include one or more repeating units selected from the following Chemical Formulas 3-1 to 3-4: [Chemical Formula 3-1]

[Chemical formula 3-2]

[Chemical formula 3-3]

[Chemical formula 3-4]

.

At the same time, in the inclusion of alkyl polyether silicates having one or more alkyl substituents (rather than all alkoxy-substituted silicates (such as Chemical formula 3 and Chemical formula 3-1 to 3-4)) In the case of modified EVOH as the third repeating unit, the free volume may increase due to the long alkyl polyether chain and may cause defects in the formation of the crystal structure by the plasticizing effect and interaction with vinyl alcohol groups . Also, in the case of using additives containing mercapto groups, alkyl polyether silicates having one or more alkyl substituents can form disulfide groups by oxidation reaction due to heat, and thus may form undesired groups the structural unit. In addition, because the thiol group has higher acidity than the alcohol group, in the presence of an alkaline catalyst such as sodium hydroxide, a thiolate may be formed instead of an alkoxide, and thus may not be formed Structural units derived herein. Molar amount of repeating unit

In a specific example of the modified ethylene-vinyl alcohol-based copolymer, the function of the first repeating unit is to increase mechanical properties and processability, and the function of the second repeating unit is to increase gas barrier properties.

Therefore, in the modified ethylene-vinyl alcohol-based copolymer of a specific example, if the molar amount of the first repeating unit is reduced, the processability may be reduced, and if the molar ratio of the second repeating unit is reduced, the gas barrier may be reduced Properties may be reduced.

Considering this trend, the molar ratio of the first repeating unit and the second repeating unit in a specific example of the modified ethylene-vinyl alcohol-based copolymer can be controlled at 20:80 to 40:60, specifically 25:75 to 35:65, eg, within the range of 30:70 to 33:67.

The molar ratio of the first repeating unit and the second repeating unit in the modified ethylene-vinyl alcohol-based copolymer of a specific example can be the same as that of the first repeating unit and the second repeating unit in the reactant ethylene-vinyl alcohol-based copolymer. The mol ratio is the same. Therefore, the first repeating unit in the final product modified ethylene-vinyl alcohol-based copolymer can be controlled by controlling the molar ratio of the first repeating unit and the second repeating unit in the reactant ethylene-vinyl alcohol-based copolymer and the molar ratio of the second repeat unit.

In a specific example of the modified ethylene-vinyl alcohol-based copolymer, the function of the third repeating unit is to increase the molecular weight, the cross-linked structure and the long-chain branch in the molecule, and to improve the flexibility, rigidity and melt strength of the final product , and ultimately improve the processability and mechanical properties of the molded article.

Therefore, as the content of the third repeating unit in the modified ethylene-vinyl alcohol-based copolymer of a specific example is decreased, the molecular weight, the cross-linked structure in the molecule, and the long-chain branching may be decreased. However, as the content of the third repeating unit increases, a gel may instead be formed and the processability may be deteriorated.

Taking into account such trends, in a specific example of the modified ethylene-vinyl alcohol-based copolymer, the content of the third repeating unit can be controlled to be based on 100 mol parts of the second repeating unit, 1 to 10 mol. parts, specifically in the range of 1.5 to 7 mol parts (eg, 2 to 4 mol parts).

The content of the third repeating unit in the modified ethylene-vinyl alcohol-based copolymer of a specific example (based on 100 moles of the second repeating unit) can be related to the amount of the introduced crosslinking agent (based on 100 moles). The hydroxyl group (-OH group) in the reactant ethylene-vinyl alcohol-based copolymer is the same. Therefore, by controlling the introduction amount of the crosslinking agent (based on 100 mole parts of the hydroxyl group (-OH group) in the reactant ethylene-vinyl alcohol-based copolymer), the final product modified ethylene-ethylene can be controlled. The content of the third repeating unit in the alcohol-based copolymer.

In the total amount (100 mol %) of the modified ethylene-vinyl alcohol-based copolymer, 25 to 35 mol % of the first repeating unit and 0.5 to 7 mol % of the third repeating unit may be included, and the second repeating unit may be Included in the remaining amount.

This comprehensively takes into account the molar ratio of the first repeating unit and the second repeating unit in the modified ethylene-vinyl alcohol-based copolymer, as well as the content of the third repeating unit (based on 100 mole parts of the second repeating unit as a basis ).

For example, in the total amount (100 mol %) of the modified ethylene-vinyl alcohol-based copolymer, 29 to 32 mol % of the first repeating unit and 1 to 3 mol % of the third repeating unit may be included, and the second repeating unit may be included Units can be included in the remainder.

Here, the "remaining amount" regarding the content of the second repeating unit means [total amount of the modified ethylene-vinyl alcohol-based copolymer (100 mol%) - (total sum of repeating units excluding the second repeating unit)].

Specifically, in the case where only the first to third repeating units are contained in the modified ethylene-vinyl alcohol-based copolymer, the content of the second repeating unit may be [total amount of the modified ethylene-vinyl alcohol-based copolymer ( 100 mol%) - (content of the first repeating unit + content of the third repeating unit)].

Also, in the case where the modified ethylene-vinyl alcohol-based copolymer includes other repeating units (for example, the fourth repeating unit) in addition to the first to third repeating units, the content of the second repeating unit may be [modified The total amount of ethylene-vinyl alcohol-based copolymers (100 mol%) - (the content of the first repeating unit + the content of the third repeating unit + the content of the fourth repeating unit)].

In EVOH, as the ethylene content corresponding to the first repeating unit is reduced, it may have properties similar to poly(vinyl alcohol) (PVA), and the relatively flexible ethylene structure may be reduced, thus making processability worse. Conversely, as the vinyl alcohol structural unit increases, Tg and Tm may increase, and if the ethylene content is reduced to a very low level, Tm may become higher than the decomposition temperature, thus making processing difficult.

Meanwhile, the modified ethylene-vinyl alcohol-based copolymer may further include a heterogeneous repeating unit in addition to the first repeating unit, the second repeating unit, and the third repeating unit.

The heterogeneous repeating unit may be derived from the reactant ethylene-vinyl alcohol-based copolymer. Specifically, when a monomer mixture including a vinyl-based monomer, a vinyl carboxylate-based monomer B, and a heterogeneous monomer is polymerized to prepare an ethylene-vinyl acetate (EVA)-based copolymer, which is then saponified to prepare an ethylene-vinyl acetate (EVA)-based copolymer In the case of a vinyl alcohol-based copolymer, the heterogeneous repeating unit may be further included together with the first repeating unit and the second repeating unit. When such an ethylene-vinyl alcohol-based copolymer is reacted with a crosslinking agent, a modified ethylene-vinyl alcohol-based copolymer containing a heterogeneous repeating unit in addition to the first repeating unit and the second repeating unit can be obtained.

Modified ethylene-vinyl alcohol-based copolymers with various qualities can be provided depending on the kind and content of the heterogeneous repeating unit. Wherein, the type and content of the heterogeneous repeating unit can be in accordance with the technical knowledge known in the technical field. Weight Average Molecular Weight and Molecular Weight Distribution

The modified ethylene-vinyl alcohol-based copolymer may have a high molecular weight compared to the unmodified ethylene-vinyl alcohol-based copolymer.

Specifically, the modified ethylene-vinyl alcohol-based copolymer may have a weight average molecular weight of 100,000 to 200,000 g/mol and a molecular weight distribution (MWD; Mw/Mn) of 1.0 to 3.0.

However, if the molecular weight of the modified ethylene-vinyl alcohol-based copolymer is too low, film production may be problematic, and if it is too high, processability problems may arise. At the same time, as the weight average molecular weight of the modified ethylene-vinyl alcohol-based copolymer increases, the molecular weight distribution tends to become wider, and if the molecular weight distribution becomes wider, a processability problem may arise.

Taking into account such trends, the weight average molecular weight of the modified ethylene-vinyl alcohol-based copolymer can be controlled at 100,000 g/mol or more, 110,000 g/mol or more, or 120,000 g/mol or more, and 200,000 g/mol or more. g/mol or less, 190,000 g/mol or less, or 180,000 g/mol or less. Also, the molecular weight distribution of the modified ethylene-vinyl alcohol-based copolymer can be controlled to be 1.0 or higher, 1.3 or higher, or 1.5 or higher, and 3.0 or lower, 2.5 or lower, or 2.0 or lower.

Among them, the weight average molecular weight and molecular weight distribution of the final product modified ethylene-vinyl alcohol-based copolymer can be controlled by controlling the molecular weight of the reactant ethylene-vinyl alcohol-based copolymer, the introduction amount of the crosslinking agent, and the reaction time. Method for producing modified ethylene - vinyl alcohol-based copolymer

According to another specific example of the present invention, there is provided a method for producing a modified ethylene-vinyl alcohol-based copolymer, which comprises making the ethylene-vinyl alcohol-based copolymer and tetraethyl orthosilicate (TEOS) in a range of 50 to The steps of the reaction in the temperature range of 100°C.

By reacting the ethylene-vinyl alcohol-based copolymer with tetraethyl orthosilicate in the reaction temperature range, a partial crosslinking in the ethylene-vinyl alcohol-based copolymer molecule and the interaction between different ethylene-vinyl alcohol-based copolymer molecules are formed. cross-linking between them, and finally the modified ethylene-vinyl alcohol-based copolymer as one specific example described above can be obtained.

The production method of a specific example corresponds to the preparation of the ethylene-vinyl alcohol-based copolymer followed by subsequent modification, and does not require introduction of catalysts, solvents, etc., so low-cost operation and high-efficiency process can be realized.

Also, depending on the quality of the reactant ethylene-vinyl alcohol-based copolymer, the quality of the final product can be diversified. The quality of the reactant ethylene-vinyl alcohol-based copolymer can be determined by the molar ratio of the first repeating unit and the second repeating unit, the type and content of the additionally included repeating unit, and the like.

Hereinafter, the characteristics of the manufacturing method of one specific example will be described in detail, but the overlapping description with the specific example described above will be omitted. Reaction conditions

The reaction of a specific example can be carried out in a temperature range in which the ethylene-vinyl alcohol-based copolymer and tetraethyl orthosilicate can react, specifically 50 to 100° C., more specifically 60 to 90° C., for example, 70 to 80° C. °C.

On the contrary, at a temperature lower than 50°C, for example, at a room temperature of 20 to 30°C, the ethylene-vinyl alcohol-based copolymer and tetraethyl orthosilicate can be simply mixed without reacting.

The reaction of a specific example may be performed for a period of time during which the ethylene-vinyl alcohol-based copolymer and tetraethyl orthosilicate may react, specifically 2 to 30 hours, more specifically 3 to 27 hours, for example, 4 to 24 hours .

When other conditions (such as reaction temperature) are the same, as the reaction time is prolonged within the above range, partial crosslinking and long chain branching in the molecule may increase. However, if the reaction time is too long, a gel may instead be formed and the processability may be deteriorated.

Meanwhile, the reaction of a specific example can be carried out with stirring at a speed of 50 to 400 rpm, specifically 100 to 300 rpm, for example, 150 to 250 rpm.

When other conditions are the same, as the stirring speed is increased within the above range, partial cross-linking and long-chain branching in the molecule may increase. However, if the stirring speed is excessively increased, a gel may instead be formed and the processability may be deteriorated. post-processing

In the reaction product, impurities such as a catalyst for preparing the reactant ethylene-vinyl alcohol-based copolymer and the like may remain. In order to remove them, after the reaction ends, the reaction product may be further washed; and the step of drying the washed reaction product.

In the raw ethylene-vinyl alcohol-based copolymer, the catalyst used in the production process may remain as an impurity. Impurity catalysts may remain even after reaction with tetraethyl orthosilicate and may not be removed until the washing procedure.

Specifically, the reaction product can be soaked in distilled water for a sufficient time, and then a filter can be used to separate the solid/liquid, and the separated solid can be left at room temperature or dried by heating in an oven.

More specific washing and drying conditions can be in accordance with technical knowledge generally known in the technical field to which the invention pertains. Reactant

As explained above, the first repeat in the final product modified ethylene-vinyl alcohol-based copolymer can be controlled by controlling the molar ratio of the first repeating unit and the second repeating unit in the reactant ethylene-vinyl alcohol-based copolymer The molar ratio of the unit to the second repeat unit.

In this regard, the molar ratio of the first repeating unit and the second repeating unit in the reactant ethylene-vinyl alcohol-based copolymer can be controlled to be 20:80 to 40:60, specifically 25:75 to 35:65, for example , within the range of 30:70 to 33:67.

In addition, the modified ethylene- The content of the third repeating unit in the vinyl alcohol-based copolymer.

In this regard, based on 100 mol parts of hydroxyl groups (-OH groups) in the reactant ethylene-vinyl alcohol-based copolymer, the introduction amount of the cross-linking agent can be controlled at 1 to 10 mol parts, specifically: 1.5 to 7 moles, eg, in the range of 2 to 4 moles.

Meanwhile, a commercially available product may be used as the reactant ethylene-vinyl alcohol-based copolymer, or it may be prepared by itself.

In the latter case, before the reaction of a specific example, it may further include polymerizing a monomer mixture comprising a vinyl-based monomer and a vinyl carboxylate-based monomer to prepare an ethylene-vinyl acetate (EVA)-based copolymer; and A step of saponifying ethylene-vinyl acetate to prepare an ethylene-vinyl alcohol-based copolymer.

The preparation procedure and saponification procedure of ethylene-vinyl acetate can be in accordance with the technical knowledge generally known in the technical field to which the invention belongs. Hereinafter, procedures known in the technical field to which the invention pertains will be partially described.

The preparation procedure of ethylene-vinyl acetate can be carried out by common polymerization methods, in particular, can be carried out using a free radical initiator in a solvent.

When the polymerization is carried out, the introduction amount of the vinyl-based monomer and the vinyl carboxylate-based monomer can be determined in consideration of the content of the repeating units derived from each compound in the finally prepared copolymer. Specifically, it can be introduced in a molar ratio of 20:80 to 40:60, specifically 25:75 to 35:65, for example, 30:70 to 33:67. Also, when reacted at the above molar ratio, the content of the repeating units derived from ethylene in the prepared ethylene-vinyl acetate-based copolymer can be optimized, and thus the hygroscopicity of the polymer can be reduced and prevented from being exposed to high humidity environments lower gas barrier properties.

The monomer mixture may further comprise heterogeneous monomers. In this case, in the prepared ethylene-vinyl acetate and the final modified ethylene-vinyl alcohol-based copolymer, a heterogeneous repeating unit may be further included. The type and content of the heterorepetitive unit can be based on technical knowledge generally known in the technical field to which the invention pertains.

As initiators, radical initiators, mention may be made of, for example, azo compounds such as 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azo Azodiisobutyronitrile, 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis-(2-methylisobutyric acid peroxydicarbonate, such as, bis-(4-tert-butylcyclohexyl peroxydicarbonate), dicyclohexyl peroxydicarbonate, bis(2-ethylhexyl peroxydicarbonate) ) two second butyl ester, diisopropyl peroxydicarbonate, etc.; peroxides, such as, acetyl peroxide, lauryl peroxide, dilaurin peroxide, didecyl peroxide, dioctyl peroxide etc.; and mixtures of two or more of these and the like may be used.

The initiator may be contained in an amount of 0.001 to 1 mol part, more specifically 0.001 mol part or more, based on 100 mol parts of the total monomer mixture comprising the vinyl-based monomer and the vinyl carbonate-based monomer , or 0.01 mol part or more, and 1 mol part or less or 0.1 mol part or less are introduced. When introduced in the above content range, the polymer can be produced with excellent efficiency.

As for the solvent, those having high solubility of the monomer compound can be used. Specifically, alcohols such as methanol, ethanol, propanol, isopropanol, tert-butanol, n-amyl alcohol, etc.; ketones such as methyl ethyl ketone, acetone, etc.; or selenium can be mentioned , such as dimethyl sulfoxide, etc.; and a mixture of two or more of them and the like can be used. Among them, an alcohol exhibiting more excellent solubility can be used, and more specifically, tertiary butanol can be used.

The solvent may be present in an amount of 30 to 60 parts by weight, more specifically 30 parts by weight or more, or 40 parts by weight, based on 100 parts by weight of the total monomer mixture comprising the vinyl-based monomer and the vinyl carboxylate-based monomer parts or more, and 60 parts by weight or less, or 50 parts by weight or less are introduced. When introduced in the above content range, the monomer can be completely dissolved, and a polymer can be prepared with excellent polymerization efficiency.

The polymerization reaction of the monomer mixture comprising the vinyl monomer and the vinyl carboxylate monomer may be at 50 to 80°C, more specifically at 50°C or higher, or 60°C or higher, and 80°C or lower , or at 70°C or lower. When the reaction is carried out within the above-mentioned temperature range, there is no fear that the polymerization efficiency will deteriorate (deteriorate) due to unreacted or excessively reacted.

The ethylene-vinyl acetate-based copolymer is prepared by the polymerization procedure, and by controlling the monomer content and preparation conditions in the preparation procedure, the prepared copolymer can exhibit optimized weight average molecular weight, molecular weight distribution and derived from ethylene The content of the structural unit, etc.

Specifically, the ethylene-vinyl acetate-based copolymer may have 90,000 to 350,000 g/mol, more specifically 100,000 g/mol or more, or 110,000 g/mol or more, and 150,000 g/mol or less, A weight average molecular weight of 140,000 g/mol or less, or 130,000 g/mol or less. Also, the molecular weight distribution (MWD) can be 1.0 to 3.0, more specifically 1.0 or higher, 1.3 or higher, or 1.5 or higher, and 3.0 or lower, 2.5 or lower, or 2.0 or lower. In addition, the content of repeating units derived from ethylene may be 20 mol% or more, 25 mol% or more, or 30 mol% based on the total repeating units in 100 mol% of the ethylene-vinyl acetate-based copolymer. mol% or more, and 40 mol% or less, 35 mol% or less, or 33 mol% or less. Because the copolymer has a high weight average molecular weight, a narrow molecular weight distribution, and an optimized content of repeating units derived from olefins, it can maintain excellent mechanical properties while exhibiting better gas barrier properties when making films.

More specifically, the copolymer of an olefin and a vinyl carboxylate compound may be an ethylene-vinyl acetate copolymer satisfying the above properties.

The ethylene-vinyl acetate copolymer can be hydrolyzed by a saponification reaction and converted into an ethylene-vinyl alcohol-based copolymer.

Hydrolysis can be carried out by introducing alkaline materials or bases such as caustic soda. The copolymer of olefin and vinyl carboxylate compound is hydrolyzed by the saponification reaction caused by the introduction of an alkaline substance, and the repeating units derived from the vinyl carboxylate compound in the copolymer can be partially or completely converted into hydroxyl group-containing compounds the repeating unit.

Based on 100 moles of ethylene-vinyl acetate copolymer, the basic material may be 5 to 15 moles, more specifically 5 moles or more, or 7 moles or more, and 15 The content of mol parts or less, or 12 mol parts or less is introduced. If the content of the alkaline substance is less than 5 mol parts, hydrolysis may not occur sufficiently, and if the content of the alkaline substance is more than 15 mol parts, excessive waste water may be generated in the process of removing the catalyst, and if the content of the alkaline substance is more than 15 mol parts Insufficient catalyst removal may result in discoloration or unevenness of the film.

The basic substance can be dissolved in an alcohol solvent such as methanol and introduced as a solution so as to increase the reaction efficiency.

Also, the hydrolysis can be performed at a temperature of 50 to 70°C, more specifically 50°C or higher, or 60°C or higher, and 70°C or lower, or 65°C or lower. When carried out within the above temperature range, hydrolysis can sufficiently occur at an appropriate reaction rate. molded object

According to yet another embodiment of the present invention, there is provided a molded article including the modified ethylene-vinyl alcohol-based copolymer of an embodiment.

A specific example of the molded article exhibits the characteristic gas barrier properties of ethylene-vinyl alcohol based copolymers, and thus, can be used in various applications such as films, sheets, containers, fibers, etc., where gas barrier properties are required.

In particular, since the molded article of a specific example includes a modified ethylene-vinyl alcohol-based copolymer having excellent flexibility, rigidity, and melt strength, it may have excellent processability and mechanical properties.

In particular, according to ASTM 412, the molded article may have a tensile strength of 50 to 100 Mpa, in particular 55 to 95 Mpa, for example, 60 to 90 Mpa, and 2,000 to 3,000 Mpa at 300% elongation, in particular A tensile stress of 2,030 to 2,700 Mpa, for example, 2,050 to 2,500 Mpa.

Molded articles having excellent processability and mechanical properties can be used for packaging materials such as food packaging films, etc., sheets, cosmetic containers, gasoline tank containers, and the like.

Molded articles can be produced by common molding methods, such as injection molding, compression molding, extrusion molding, and the like. Among them, as for extrusion molding, a T-die method, a blow molding method, a pipe extrusion method, a wire extrusion method, a release die extrusion method, an inflation method, etc. can be mentioned, and a vinyl alcohol-based copolymer can also be performed Co-extrusion molding with other thermoplastic resin layers.

When manufacturing the molded article, well-known additives such as reinforcing materials (such as glass fibers, carbon fibers, etc.), colorants, stabilizers (such as hydrotalcite), foaming agents, desiccants, thermoplastic resin, etc.

Membrane articles can be used alone, for example, in the form of films, as coatings on substrates, or in multilayer structures with other films.

Hereinafter, the action and efficacy of the present invention will be described in more detail through specific embodiments of the present invention. However, these embodiments are provided only as an illustration of the present invention, and are not intended to limit the scope of rights of the present invention. Example 1 ( modified EVOH)

An ethylene vinyl alcohol (EVOH) solution was prepared. The EVOH solution contained 5 wt% EVOH and the remaining amount of methanol. Also, EVOH had a weight average molecular weight (Mw) of 120,000 g/mol, a molecular weight distribution (MWD) of 1.7, a content of repeating units derived from ethylene in the copolymer of 32 mol %, and a hydroxyl group (—OH group) of 68 mol %. )content.

In an autoclave with a capacity of 500 mL, 365 g of EVOH solution and 3.3 g of tetraethyl orthosilicate (TEOS) cross-linking agent were introduced. The introduction amount of the crosslinking agent corresponds to 4 mol parts based on 100 mol parts of hydroxyl groups (—OH groups) of EVOH in the EVOH solution.

After the introduction of the reactants, the reaction was carried out at 75° C. with stirring at a stirring speed of 200 rpm for 24 hours.

After the reaction was completed, the product cooled to room temperature was put into 2 L of distilled water and washed for 2 hours, and then solid/liquid separation was performed using a reduced pressure filter.

The solid material separated by solid/liquid separation was dried in a vacuum oven at 50° C. for 24 hours, thus finally obtaining the modified EVOH of Example 1. Example 2 ( change reaction time )

A modified EVOH was produced by the same method as in Example 1, but the reaction time was changed to 4 hours. Example 3 ( change the content of crosslinking agent TEOS )

A modified EVOH was produced by the same method as in Example 1, except that 0.83 g of TEOS corresponds to 1 mol part of the hydroxyl group (-OH group) of EVOH in the EVOH solution based on 100 mol parts. Content import. Example 4 ( change the content of crosslinking agent TEOS )

A modified EVOH was produced by the same method as in Example 1, except that 1.65 g of TEOS corresponds to 2 mol parts of the hydroxyl group (-OH group) of EVOH in the EVOH solution based on 100 mol parts. Content import. Comparative Example 1 (EVOH)

In Comparative Example 1, EVOH itself was used without being treated with a crosslinking agent.

Among them, EVOH is the same as that used in Example 1 (Mw: 120,000 g/mol, MWD: 1.7, content of repeating units derived from ethylene: 32 mol%, content of -OH groups: 68 mol%). Comparative Example 2 ( using 1,2- butylene oxide crosslinking agent )

A modified EVOH was produced by the same method as in Example 1, except that 1.14 g corresponds to 4 mol parts based on 100 mol parts of hydroxyl groups (-OH groups) of EVOH in the EVOH solution, 1,2-Butylene oxide was introduced instead of TEOS as a crosslinking agent.

For reference, in Examples 1 to 4 and Comparative Examples 1 and 2, the ethylene content, the introduction amount of the crosslinking agent (based on 100 mole parts of the hydroxyl group (-OH group) of EVOH before the reaction), the reaction time and the reaction temperatures are summarized in Table 1 below. 【Table 1】 Ethylene content in EVOH before reaction cross-linking agent Reaction time temperature reflex type Import volume Example 1 32 mol% TEOS 4 moles 24 hours 75℃ Example 2 32 mol% TEOS 4 moles 4 hours 75℃ Example 3 32 mol% TEOS 1 mole 24 hours 75℃ Example 4 32 mol% TEOS 2 moles 24 hours 75℃ Comparative Example 1 32 mol% - - - - Comparative Example 2 32 mol% 1,2-Butylene oxide 4 moles 24 hours 75℃ Experimental example 1

For the EVOH of Comparative Example 1 and the modified EVOH of Examples 1 to 4 and Comparative Example 2, the content of repeating units derived from ethylene, weight average molecular weight (Mw), molecular weight distribution (MWD; Mw/Mn), melt Complex viscosity and viscoelasticity.

The specific evaluation method is as follows. (1) Content of repeating units derived from ethylene

， n(乙烯)是衍生自乙烯之重複單元之莫耳量，n(VAc)是衍生自乙酸乙酯之重複單元之莫耳量， I _0.74-2.1ppm是出現在0.74至2.1 ppm處之峰面積之積分值，以及 I _4.78ppm是出現在4.78 ppm處之峰面積之積分值。 (2) 重量平均分子量 (Mw) 和分子量分布 (MWD ； Mw/Mn) Using 1 H NMR (Bruker Avance III HD 700 Mhz) as an analytical instrument, the sample was dissolved in a tetrahydrofuran solvent (THF-d8), and then the 1 H-NMR spectrum was measured at room temperature. 4 protons of ethylene monomer and 5 protons of vinyl acetate (VA) monomer appear at peaks at 0.74 to 2.1 ppm, and 1 proton of VA monomer appears at 4.78 ppm, and the copolymerization was calculated using the following Mathematical Equation 1 Content (mol%) of repeating units derived from ethylene: [Mathematical formula 1] Content of repeating units derived from ethylene (mol%)=[r/(r+1)] × 100 In formula 1 , r=

, n(ethylene) is the molar amount of repeating units derived from ethylene, n(VAc) is the molar amount of repeating units derived from ethyl acetate, I _0.74-2.1 ppm is the peak occurring at 0.74 to 2.1 ppm The integrated value of the area, and I _4.78 ppm is the integrated value of the area of the peak that occurs at 4.78 ppm. (2) Weight average molecular weight (Mw) and molecular weight distribution (MWD ; Mw/Mn)

The weight average molecular weight (Mw) and molecular weight distribution (MWD; Mw/Mn) measured using gel permeation chromatography (GPC) under the following conditions are shown in Table 2. <Measurement conditions> Measurement equipment: Agilent GPC (Agulent 1200 series, USA) String: Connected PL Mixed B Solvent: DMF / 0.05M LiBr (filtered at 0.45 μm) Sample concentration: ~1 mg/mL (100 μl injection) Flow rate: 1.0 ml/min Column temperature: 65℃ Detector: Waters Refractive Index Detector (Waters 2414 RID) Standard: Polystyrene (PS) (calibrated by cubic function)

Among them, as for the polystyrene standard, 6 kinds having molecular weights (g/mol) of 9,600/31,420/113,300/327,300/1,270,000/4,230,000 were used. -data processing:

1) A sample of the copolymer was dissolved in dimethyl sulfoxide (DMSO) at a concentration of 2.0 mg/ml and filtered through a 0.45 μm syringe filter. 2) Inject the sample solution to obtain a GPC chromatogram. 3) Inject the standard solution to obtain a GPC chromatogram. 4) Obtain the calibration curve and formula from the chromatogram of the standard solution, and substitute the residence time of the sample solution into the formula to obtain the weight-average molecular weight and number-average molecular weight of the sample. The molecular weight distribution (Mw/Mn) was calculated from the measured weight average molecular weight (Mw) and number average molecular weight (Mn). The results are shown in Table 2 below and Figures 1 and 2. (3) Melt complex viscosity and viscoelasticity

The complex viscosity and viscoelasticity were measured when the sample was placed in the sample jar of a rheometer (AR2000EX Peltier plate, TA Instruments Corp.), heated to 190° C. and melted, and then gradually increased in angular shear, and the results are shown in Fig. in Figures 3 and 4. 【Table 2】 Ethylene content Mw MWD Example 1 32mol% 176,000 g/mol 1.98 Example 2 32mol% 128,000 g/mol 1.56 Example 3 32mol% 126,000 g/mol 1.60 Example 4 32mol% 142,000 g/mol 1.78 Comparative Example 1 32mol% 121,000 g/mol 1.66 Comparative Example 2 32mol% 149,000 g/mol 1.85

In Table 2, "ethylene content" means in each of the final products of Comparative Examples 1, 2, Examples 1 to 4 (ie, EVOH of Comparative Example 1, modified EVOH of Examples 1 to 4, and Comparative Example 2) ethylene content.

As can be seen from Table 2, the EVOHs of Examples 1 to 4 have high weight average molecular weights compared to the EVOH of Comparative Example 1.

1 and 2, it can be seen that EVOH modified by TEOS (Examples 1 and 2) has high melt complex viscosity and viscoelasticity compared with unmodified EVOH (Comparative Example 1).

Therefore, the high melt complex viscosity and viscoelasticity in Examples 1 and 2 are generated by the reaction of EVOH with a cross-linking agent (TEOS), resulting from partial cross-linking in EVOH molecules and cross-linking between different EVOH molecules , and the resulting molecular weight increases.

In particular, the high gradient melt complex viscosity in Examples 1 and 4 results from long chain branching (LCB) through cross-linking between different EVOH molecules.

At the same time, in Examples 1 and 2 in which the introduction amount of the crosslinking agent is the same, the modified EVOH of Example 1 with a longer reaction time has a higher molecular weight and a wider molecular weight distribution, and a higher melt complex Viscosity and viscoelasticity.

Therefore, it can be seen that when the introduction amount of the cross-linking agent is the same, as the reaction time becomes longer, the partial cross-linking in the EVOH molecule and the cross-linking between different EVOH molecules increase, and especially the cross-linking between different EVOH molecules increases. Long chain branching (LCB) is further increased by cross-linking between them.

Also, among Examples 1, 3 and 4 in which the amount of the crosslinking agent introduced was different, it was confirmed that Example 1 having a higher TEOS content had a higher molecular weight and a broader molecular weight distribution. Likewise, under the same reaction conditions, as the amount of cross-linking agent introduced became larger, the partial cross-linking in EVOH molecules and the cross-linking between different EVOH molecules increased, and especially by the cross-linking between different EVOH molecules This further increases long chain branching (LCB). Experimental example 2

For the EVOH of Comparative Example 1 and the modified EVOH of Examples 1 and 2, the mechanical properties were evaluated according to ASTM 412 and the results are described in Table 3 below.

Specifically, using a hot press tester, the sample was press-molded with 20 tons at 180° C. for 5 minutes, thereby producing a press film.

Using an air-driven film cutter (product name: Air-Cut, MJC-150-S30-10, manufacturing company: Myung Ji Tech), the extruded film was cut to obtain a sample in the form of a dog bone in which UTM measurement could be performed.

Three points of the specimen were designated and their average thickness was measured and entered into Universal Test Machine 4204 (Instron) according to ASTM 412. Set the grip-to-grip distance to 70mm, and measure the tensile strength and tensile stress at 300% elongation (300% modulus) when the specimen is cut at a speed of 100 mm/min . 【table 3】 Tensile Strength Modulus (300%) Example 1 69.3 Mpa 2,340 Mpa Example 2 62.9 Mpa 2,070 Mpa Example 3 58.3 Mpa 2,010 Mpa Example 4 64.7 Mpa 2,130 Mpa Comparative Example 1 56.9 Mpa 1,940 Mpa Comparative Example 2 46.4 Mpa 927 Mpa

According to Table 3, the film samples comprising the modified EVOH of Examples 1 to 4 had high tensile strength and modulus compared to the EVOH of Comparative Example 1 and the modified EVOH of Comparative Example 2.

Increased molecular weight, and in particular increased long-chain branching, by reaction of EVOH with a cross-linking agent (TEOS), and thus improved flexibility, rigidity and melt strength of modified EVOH, and improved processing of film samples comprising it sexual and mechanical properties.

Also, it can be confirmed that in the case where modified EVOH is used as a crosslinking agent, those containing repeating units derived from orthosilicate such as TEO are not used, but, for example, use such as Comparative Example 2 In the case of 1,2-epoxybutane, the tensile strength and modulus were conversely deteriorated compared with unmodified EVOH.

In the case of 1,2-butylene oxide, the ethyl chain structural unit is inserted into the vinyl alcohol structural unit, and when the vinyl alcohol structural unit forms a crystal structure by intermolecular force such as hydrogen bonding, the ethyl group The chain structure can cause defects, as well as plasticizing effects due to the increased free volume of the ethyl chain. Due to such properties, Tg and Tm may decrease, resulting in inhibition of interactions, and thus may decrease modulus and tensile strength. Although a cross-linking agent is used in the present disclosure to induce an increase in intermolecular bonds, 1,2-butylene oxide is not a cross-linking mediator. Also, 1,2-epoxybutane should use an acid catalyst during the reaction, which is different from the present disclosure.

That is, it was confirmed that none of the modified EVOH had improved processability and mechanical properties compared to EVOH.

Meanwhile, in Examples 1 and 2 with the same amount of crosslinking agent introduced, the film samples including the modified EVOH of Example 1 with a longer reaction time had higher tensile strength and modulus.

Therefore, it can be seen that when the introduction amount of the cross-linking agent is the same, as the reaction time is longer, the partial cross-linking in the EVOH molecule and the cross-linking between different EVOH molecules increase, and especially the cross-linking between different EVOH molecules increases. Crosslinking increases long chain branching (LCB) and further improves the processability and properties of this membrane sample.

Also, in Examples 1, 3 and 4 with the same reaction time, the film samples including the modified EVOH of Example 1 with higher TEOS crosslinker content had higher tensile strength and modulus. This is because as the TEOS content increases, more long chain branches (LCBs) are generated by the cross-linking between EVOH molecules, and the processability and properties of the film samples are further improved. in conclusion

Putting the results of Experimental Examples 1 and 2 together, it can be seen that the polymer structure can be controlled by inducing partial cross-linking in the molecule through the reaction of EVOH and a cross-linking agent (TEOS) and generating long chain branches (LCB). .

Such modified EVOH provides flexibility and rigidity to films including it, and results in increased melt strength, thereby improving film processability and properties.

Meanwhile, although commercially available EVOH was used for the experiments in this paper, the reaction of EVOH with the cross-linking agent (TEOS) may correspond to the modification after the preparation of EVOH.

Therefore, modified EVOH having various qualities can be easily developed by changing EVA production conditions, EVOH production conditions (such as conditions for producing EVOH by saponification of EVA, etc.), and post-treatment conditions.

Also, after preparing EVOH by saponification of EVA, a post-process in which the same cleaning agent is used and the solvent is recovered without additional introduction of a catalyst or solvent is performed, and thus the cost of the entire process can be reduced, and the process can be efficiently operated .

[Fig. 1] shows the GPC analysis results of Comparative Example 1 and Example 1. [Fig.

[ Fig. 2 ] shows the results of GPC analysis of Comparative Example 1 and Example 2. [Fig.

[Fig. 3] shows the results of complex viscosity analysis of Examples 1 and 2. [Fig.

[Fig. 4] shows the results of viscoelastic analysis of Examples 1 and 2. [Fig.

Claims (19)

A modified ethylene-vinyl alcohol-based copolymer, comprising: a first repeat unit derived from ethylene; a second repeat unit derived from vinyl alcohol; and The third repeat unit is derived from tetraethyl orthosilicate (TEOS). The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein the first repeating unit is represented by the following Chemical Formula 1: [Chemical Formula 1]

. The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein the second repeating unit is represented by the following chemical formula 2: [Chemical formula 2]

. The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein the third repeating unit comprises one or more repeating units selected from the following chemical formulae 3-1 to 3-4: [chemical formula 3-1]

[Chemical formula 3-2]

[Chemical formula 3-3]

[Chemical formula 3-4]

. The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein the molar ratio of the first repeating unit to the second repeating unit is 20:80 to 40:60. The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein the third repeating unit is included in an amount of 1 to 10 mol parts based on a total of 100 mol parts of the second repeating unit. The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein based on the total amount (100 mol%) of the modified ethylene-vinyl alcohol-based copolymer, the first repeating unit is 25 to 35 mol% The content of the third repeating unit is included in the content of 0.5 to 7 mol %, and the second repeating unit is included in the remaining amount. The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein the modified ethylene-vinyl alcohol-based copolymer has a weight average molecular weight of 100,000 to 200,000 g/mol. The modified ethylene-vinyl alcohol-based copolymer of claim 1, wherein the modified ethylene-vinyl alcohol-based copolymer has a molecular weight distribution (MWD; Mw/Mn) of 1.0 to 3.0. A method for producing a modified ethylene-vinyl alcohol-based copolymer, comprising: a step of reacting the ethylene-vinyl alcohol-based copolymer and tetraethyl orthosilicate (TEOS) in a temperature range of 50 to 100°C. The method of claim 10, wherein the reaction is carried out in a temperature range of 60 to 90°C. The method of claim 10, wherein the reaction is carried out for 2 to 30 hours. The method of claim 10, wherein the reaction is carried out with stirring at a speed of 50 to 400 rpm. The method of claim 10, wherein the ethylene-vinyl alcohol-based copolymer comprises a first repeating unit derived from ethylene and a second repeating unit derived from vinyl alcohol in a molar ratio of 20:80 to 40:60. The method of claim 10, wherein during the reaction, based on 100 mol parts of hydroxyl groups (-OH groups) in the ethylene-vinyl alcohol-based copolymer, 1 to 10 mol parts by weight of the original Tetraethyl silicate has reacted. The method of claim 10, further comprising the following steps after the reaction: washing the reaction product; and The washed reaction product was dried. A molded article comprising the modified ethylene-vinyl alcohol-based copolymer as claimed in claim 1. The molded article of claim 17, wherein the molded article has a tensile strength according to ASTM 412 of 50 to 100 MPa. The molded article of claim 17, wherein the molded article has a tensile stress of 2,000 to 3,000 Mpa at 300% elongation according to ASTM 412.

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