KR101684891B1 - Polyketone resin for an airtight container for keeping food - Google Patents

Abstract

The present invention relates to a food-sealed container made of a polyketone copolymer, and has an advantage of being excellent in hermeticity, gas barrier, anti-corruption, freshness maintenance and durability.

Description

TECHNICAL FIELD The present invention relates to a polyketone resin for an airtight container,

More particularly, the present invention relates to a polyketone resin for a hermetically sealed container which is made of a polyketone copolymer and is excellent in hermeticity, gas barrier property, anti-corruption, freshness maintenance and durability.

In general, meat products such as ham, sausage, and bacon, and fermented foods such as fruit, vegetables, and kimchi are packaged and preserved at the time of distribution and at home by food sealed containers or films such as various plastic containers and glass containers .

Since the food hermetically sealed container used in the above-described uses is in direct contact with various foods, it must be harmless to food and should not generate any reaction due to contact with food.

However, when various food products are stored using such food sealed container products, strains such as various bacteria, fungi, and bacteria are introduced into the food sealed container from the outside, and due to various strains flowing into the product, There is a problem that the food stored in the food-sealed container made of the material is corrupted.

In addition, since the food-sealed container is simply made of a plastic product, the durability of the entire product is lowered, which causes problems such as being easily damaged by carelessness of the consumer. In addition, And the sealing power is lowered, and the food stored in the food sealed container is corrupted.

In addition, since the hermetically sealed container for food is made of polypropylene (PP), it is relatively free from environmental hormones, etc., and the freshness of the stored food is kept and the preservation period is lowered. There was a problem that it was not enough.

In addition, there has been a problem that the durability of the food hermetically sealed container deteriorates as a whole when the food hermetically sealed container is deteriorated in its original shape and condition or deformed when used for a long period of time.

Therefore, it is important to develop a food-sealed container of a new material which is easy to maintain the hermeticity, gas barrier property, corruption prevention and freshness of the stored food, and has improved durability.

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention provides a polyketone resin for a food-sealed container of a novel material which is excellent in hermeticity, gas barrier, anti-corruption, freshness maintenance and durability by developing a food- .

In order to achieve the above object, the present invention provides a food-sealed container for storing various foods therein, wherein the food-sealed container comprises a polyketone copolymer comprising repeating units represented by the following formulas (1) and (2) Characterized in that the food-sealed container

[Chemical Formula 1]

- (CH2CH2-CO) x-

(2)

- (CH2CH (CH3) -CO) y-

(x and y are mol% of each of the formulas (1) and (2) in the polymer and y / x is 0.03 to 0.3) as means for solving the problems.

Wherein the polyketone copolymer comprises a catalyst composition comprising a palladium compound, an acid having a pKa value of 6 or less, and a bidentate compound of phosphorus; Preparing a mixed solvent (polymerization solvent) comprising methanol and water; Conducting the polymerization in the presence of the catalyst composition and the mixed solvent to prepare a linear terpolymer of carbon monoxide, ethylene and propene; And removing the remaining catalyst composition from the linear terpolymer with a solvent to obtain a polyketone resin.

Wherein the polyketone copolymer has an intrinsic viscosity (LVN) of from 1.0 to 2.0 dl / g as measured by HFIP (hexa-fluoroisopropano) at 25 DEG C, wherein the food sealed container has ASTM D256, 1/4 inch And the Izod impact strength measured by the thickness specimen is 10 kJ / m ² or more. The oxygen permeability is 0.01 cc / pack.day or less at a relative humidity of 90% in a container manufactured to a thickness of 2.5 mm.

The food hermetically sealed container of the present invention is made of a polyketone polymer and is excellent in hermeticity, gas barrier, anti-corruption, freshness retention, and durability by preventing degeneration and shape deformation.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. However, the present invention is not intended to limit the scope of the present invention. The present invention will be described in detail with reference to the following non-limiting examples.

In describing the present invention, the terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

The present invention relates to a food sealed container excellent in hermeticity, gas barrier property, anti-corruption, freshness retention and durability, and which is made of a polyketone copolymer composed of a repeating unit represented by the following formulas (1) and (2) .

[Chemical Formula 1]

- (CH2CH2-CO) x-

(2)

- (CH2CH (CH3) -CO) y-

(x and y are mol% of each of the formulas (1) and (2) in the polymer and y / x is 0.03 to 0.3)

The polyketone copolymer of the present invention is a linear alternating structure and substantially contains carbon monoxide per one molecule of unsaturated hydrocarbon. Ethylenically unsaturated hydrocarbons suitable for use as precursors of polyketone polymers have up to 20 carbon atoms, preferably up to 10 carbon atoms. Ethylenically unsaturated hydrocarbons can also be selected from the group consisting of ethene and alpha-olefins such as propene, 1-butene, iso-butene, 1- hexene, 1- octene, , Or an aryl aliphatic group containing an aryl substituent on another aliphatic molecule, particularly containing an aryl substituent on an ethylenically unsaturated carbon atom. Examples of aryl aliphatic hydrocarbons in ethylenically unsaturated hydrocarbons include styrene, p-methyl styrene, p-ethyl styrene and m-isopropyl styrene. The polyketone polymer preferably used in the present invention is a copolymer of carbon monoxide and ethene or a second ethylenically unsaturated hydrocarbon having carbon monoxide, ethene and at least three carbon atoms, in particular alpha-olefins such as propene Is a terpolymer.

 When the polyketone terpolymer is used as the main polymer component of the blend of the present invention, there are at least two units containing an ethylene moiety in each unit containing the second hydrocarbon moiety in the terpolymer. It is preferable that the number of units containing the second hydrocarbon moiety is from 10 to 100.

In another embodiment, the polyketone polymer is a copolymer comprising repeating units represented by the general formulas (1) and (2), and y / x is preferably 0.03 to 0.3. When the value of the y / x value is less than 0.03, there is a limit in that the meltability and processability are inferior. When the value of y / x is more than 0.3, the mechanical properties are poor. Further, y / x is more preferably 0.03 to 0.1.

- [- CH2CH2-CO] x- (1)

- [- CH2 --CH (CH3) - CO] y - (2)

In addition, the melting point of the polymer can be controlled by controlling the ratio of ethylene to propylene in the polyketone polymer. For example, when the molar ratio of ethylene: propylene: carbon monoxide is adjusted to 46: 4: 50, the melting point is about 220 ° C, while the melting point is adjusted to 235 ° C when the molar ratio is adjusted to 47.3: 2.7: 50.

Particularly preferred are polyketone polymers having a number average molecular weight of from 100 to 200,000, especially from 20,000 to 90,000, as measured by gel permeation chromatography. The physical properties of the polymer are determined according to the molecular weight, depending on whether the polymer is a copolymer or a terpolymer and, in the case of a terpolymer, the properties of the second hydrocarbon part. The melting point of the total of the polymers used in the present invention is 175 ° C to 300 ° C, and generally 210 ° C to 270 ° C. The intrinsic viscosity (LVN) of the polymer measured by HFIP (hexafluoroisopropyl alcohol) at 60 DEG C using a standard tubular viscosity measuring apparatus is 0.5 dl / g to 10 dl / g, preferably 0.8 dl / g to 4 dl / g, And more preferably 1.0 dl / g to 2.0 dl / g. If the intrinsic viscosity is less than 0.5 dl / g, the mechanical properties are deteriorated. If the intrinsic viscosity exceeds 10 dl / g, the workability is deteriorated.

On the other hand, the molecular weight distribution of the polyketone is preferably 1.5 to 2.5, more preferably 1.8 to 2.2. When the ratio is less than 1.5, the polymerization yield decreases. When the ratio is 2.5 or more, the moldability is poor. In order to control the molecular weight distribution, it is possible to adjust proportionally according to the amount of the palladium catalyst and the polymerization temperature. That is, when the amount of the palladium catalyst is increased or when the polymerization temperature is 100 ° C or higher, the molecular weight distribution becomes larger.

The polyketone copolymer of the present invention is polymerized through liquid phase polymerization in which carbon monoxide and olefin are carried out in an alcohol solvent through a catalyst composition comprising a palladium compound, an acid having 6 or less PKa and phosphorus of this phosphorus compound. The polymerization temperature is preferably from 50 to 100 ° C. and the reaction pressure is from 40 to 60 bar. The polymer is recovered through filtration and purification processes after polymerization, and the remaining catalyst composition is removed with a solvent such as alcohol or acetone.

As the palladium compound, palladium acetate is preferable, and the amount of the palladium compound to be used is preferably 10 ^-3 to 10 ^-1 mole. Specific examples of the acid having a pKa value of 6 or less include trifluoroacetic acid, p-toluenesulfonic acid, sulfuric acid, and sulfonic acid. In the present invention, trifluoroacetic acid is used and its amount is preferably 6 to 20 equivalents based on palladium. ((2,2-dimethyl-1,3-dioxane-5,5-diyl) bis (methylene)) bis (bis (2-methoxyphenyl) phosphine) is preferable as the two- , And the amount to be used is preferably 1 to 1.2 equivalents based on palladium.

Hereinafter, the polymerization process of the polyketone copolymer will be described in detail.

The polymerization of the polyketone copolymer of the present invention is carried out in the presence of an organometallic complex catalyst comprising (a) a Group 9, 10 or 11 transition metal compound and (b) a ligand having an element of Group 15, Is prepared by terpolymerizing carbon monoxide and ethylenic and propylenically unsaturated compounds in the medium.

The (a) Group 9, Group 10 or Group 11 transition metal compound may be a complex of cobalt or ruthenium, a carbonate, a phosphate, a carbamate or a sulfonate, and specific examples thereof include cobalt acetate, cobalt acetyl Acetate, ruthenium acetate, ruthenium trifluoroacetate, ruthenium acetylacetate, ruthenium trifluoromethanesulfonate. Nickel, or palladium, carbonates, phosphates, carbamates, and sulfonates, and specific examples thereof include nickel acetate, nickel acetylacetate, palladium acetate, palladium trifluoroacetate, palladium chloride, bis (Diethylamine) palladium, palladium sulfate, complexes of copper or silver, carbonates, phosphates, carbamates, sulfonates and the like, and examples thereof include copper , Copper trifluoroacetate, copper acetylacetate, acetic acid silver, trifluoroacetic acid silver, silver acetylacetate, trifluoromethanesulfonic acid and the like.

Among them, a palladium compound, particularly palladium acetate, is preferable in terms of yield of polyketone and molecular weight.

Examples of the ligand having an atom of Group 15 of (b) include (bis (2,2-dimethyl-1,3-dioxane-5,5-diyl) bis (methylene) ) Phosphine), 2,2'-bipyridyl, 4,4'-dimethyl-2,2'-bipyridyl, 2,2'-biphenyl- Bis (diphenylphosphino) propane, 1,4-bis (diphenylphosphino) butane, 1,3-bis [di (2-methoxyphenyl) phosphine] propane, 1,3-bis [di (2-isopropyl) Bis (diphenylphosphino) benzene, 1,2-bis (diphenylphosphino) benzene, 1,2-bis (diphenylphosphino) Bis [(di (2-methoxyphenyl) methyl] benzene, 1,2-bis [ Sulfonate sodium-phenyl) phosphino] methyl] benzene, 1,1'-bis (diphenylphosphino) ferrocene, 2- Phosphines such as 2,2-dimethyl-1,3-bis [di (2-methoxyphenyl) phosphino] And the like.

Among them, preferred ligands (b) having a Group 15 element are phosphorus ligands having an atom of Group 15, and particularly preferred ligands in terms of the yield of polyketone are ((2,2-dimethyl- Di (2-methoxyphenyl) phosphine), 1,3-bis [di (2-methoxyphenyl) phosphino] Bis [di (2-methoxyphenyl) phosphino] methyl] benzene in view of the molecular weight of the polyketone and 2-hydroxy- Propane, 2,2-dimethyl-1,3-bis [di (2-methoxyphenyl) phosphino] propane and, in view of safety without requiring an organic solvent, (3-dioxane-5,5-diyl) bis (methylene)) bis (bis (2- methoxyphenyl) phosphine), 1,3- ) Phosphino] propane, 1,2-bis [[di (2-methoxy-4-sulfonic acid sodium- phenyl) phosphino] methyl] benzene, A ((2,2-dimethyl-1,3-dioxane-5,5-diyl) bis (methylene)) bis (bis (2-methoxyphenyl) phosphine).

The liquid medium is preferably a mixed solvent of an alcohol (for example, methanol) and water, and is subjected to liquid phase polymerization in the mixed solvent to produce a linear terpolymer. As the mixed solvent, a mixture of 100 parts by weight of methanol and 2 to 10 parts by weight of water Can be used. If the content of water in the mixed solvent is less than 2 parts by weight, a ketal may be formed to lower the heat stability in the process. If the amount is more than 10 parts by weight, the mechanical properties of the product may be deteriorated.

When the polyketone of the present invention is polymerized, benzophenone may be added as needed. The amount of benzophenone to be added is such that (a) the molar ratio of benzophenone to the ninth, tenth or eleventh transition metal compound and 1: 5-100, preferably 1: 40-60. If the molar ratio of the transition metal to the benzophenone is less than 1: 5, the effect of improving the intrinsic viscosity of the produced polyketone is unsatisfactory. If the molar ratio of the transition metal to the benzophenone exceeds 1: 100, .

(a) The amount of the Group 9, Group 10 or Group 11 transition metal compound to be used varies depending on the kind of the ethylenically unsaturated compound to be selected and other polymerization conditions, But is usually 0.01 to 100 mmol, preferably 0.01 to 10 mmol, per liter of the reaction volume of the reaction zone. The capacity of the reaction zone means the liquid phase capacity of the reactor. The amount of the ligand (b) to be used is not particularly limited, but is usually 0.1 to 3 mol, preferably 1 to 3 mol, per 1 mol of the transition metal compound (a).

Examples of the ethylenically unsaturated compound copolymerized with carbon monoxide include ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, -Olefins such as hexadecene and vinylcyclohexane; Alkenyl aromatic compounds such as styrene and? -Methylstyrene; But are not limited to, cyclopentene, norbornene, 5-methylnorbornene, 5-phenylnorbornene, tetracyclododecene, tricyclododecene, tricyclo undecene, pentacyclopentadecene, pentacyclohexadecene, Cyclic olefins such as tetracyclododecene; Vinyl halides such as vinyl chloride; And acrylic acid esters such as ethyl acrylate and methyl acrylate. Of these, preferred ethylenically unsaturated compounds are? -Olefins, more preferably? -Olefins having 24 carbon atoms, and most preferably ethylene.

The ternary copolymerization of carbon monoxide, the ethylenically unsaturated compound and propene is carried out in the presence of an organometallic complex catalyst comprising a ligand (b) having an element of group 9, group 10 or group 11 transition metal compound (a) and group 15 element , Wherein the catalyst is produced by contacting the two components. Any method may be employed as the method of contacting. That is, the solution may be prepared as a solution in which two components are premixed in a suitable solvent, or the two components may be supplied separately to the polymerization system and contacted in the polymerization system.

As the polymerization method, a solution polymerization method using a liquid medium, a suspension polymerization method, a vapor phase polymerization method in which a small amount of a polymer is impregnated with a high concentration catalyst solution, and the like are used. The polymerization may be either batchwise or continuous. The reactor used for the polymerization may be a known reactor as it is, or may be processed. The reaction temperature and the reaction pressure in the polymerization are suitably in the range of 50 to 100 ° C and 40 to 60 bar, respectively. The resulting polymer is recovered through filtration and purification processes after polymerization, and the remaining catalyst composition is removed with a solvent such as alcohol or acetone.

The obtained polyketone polymer is extruded by an extruder. The extrusion temperature is preferably 230 to 260 DEG C, and the screw rotation speed is preferably in the range of 100 to 300 rpm. If the extrusion temperature is less than 230 캜, kneading may not occur properly, and if the extrusion temperature exceeds 260 캜, problems related to the heat resistance of the resin may occur. If the screw rotation speed is less than 100 rpm, smooth kneading may not occur.

Hereinafter, the constitution and effects of the present invention will be described in detail with reference to specific examples and comparative examples, but these examples are merely for the purpose of understanding the present invention more clearly and do not limit the scope of the present invention. The present invention will be described in detail with reference to the following non-limiting examples.

Example 1

Catalysts formed from palladium acetate, trifluoroacetic acid and ((2,2-dimethyl-1,3-dioxane-5,5-diyl) bis (methylene)) bis (bis (2-methoxyphenyl) A linear alternating polyketone terpolymer of carbon monoxide and ethylene and propene was prepared in the presence of the composition. In the above, the content of trifluoroacetic acid with respect to palladium is 11 times the molar ratio, and the two stages of the first stage at a polymerization temperature of 80 ° C and the second stage at 84 ° C are carried out. The molar ratio of ethylene to propene in the polyketone terpolymer prepared above was 46 to 4. The melting point of the polyketone terpolymer was 220 占 폚, the LVN measured at 25 占 폚 with HFI P (hexa-fluoroisopropano) was 1.2 dl / g, the MI index was 60 g / 10 min and the MWD was 2.0.

The prepared polyketone terpolymer was fed into a twin screw extruder of L / D32 and D40 and extruded through melt kneading at a temperature of 240 DEG C and a screw rotation speed of 250 rpm.

Example 2

Catalysts formed from palladium acetate, trifluoroacetic acid and ((2,2-dimethyl-1,3-dioxane-5,5-diyl) bis (methylene)) bis (bis (2-methoxyphenyl) A linear alternating polyketone terpolymer of carbon monoxide and ethylene and propene was prepared in the presence of the composition. In the above, the content of trifluoroacetic acid with respect to palladium is 10 times the molar ratio, and the two stages of the first stage at a polymerization temperature of 78 占 폚 and 84 占 폚 are carried out. The molar ratio of ethylene to propene in the polyketone terpolymer prepared above was 46 to 4. The melting point of the polyketone terpolymer was 220 占 폚, the LVN measured at 25 占 폚 by HFIP (hexa-fluoroisopropano) was 1.4 dl / g, the MI index was 45 g / 10 min and the MWD was 2.0.

The prepared polyketone terpolymer was fed into a twin screw extruder of L / D32 and D40 and extruded through melt kneading at a temperature of 240 DEG C and a screw rotation speed of 250 rpm.

Example 3

(Bis (2-methoxyphenyl) phosphine) produced from bis (bis (2-methoxyphenyl) phosphine) palladium acetate, trifluoroacetic acid and bis A linear alternating polyketone terpolymer of carbon monoxide and ethylene and propene was prepared in the presence of the catalyst composition. In the above, the content of trifluoroacetic acid with respect to palladium is 9 times the molar ratio, and the two stages of the first stage at a polymerization temperature of 74 deg. C and the second stage at 84 deg. The molar ratio of ethylene to propene in the polyketone terpolymer prepared above was 46 to 4. The melting point of the polyketone terpolymer was 220 占 폚, the LVN measured at 25 占 폚 by HFIP (hexa-fluoroisopropano) was 1.6 dl / g, the MI index was 20 g / 10 min and the MWD was 2.0.

The prepared polyketone terpolymer was fed into a twin screw extruder of L / D32 and D40 and extruded through melt kneading at a temperature of 240 DEG C and a screw rotation speed of 250 rpm.

Example 4

Catalysts formed from palladium acetate, trifluoroacetic acid and ((2,2-dimethyl-1,3-dioxane-5,5-diyl) bis (methylene)) bis (bis (2-methoxyphenyl) A linear alternating polyketone terpolymer of carbon monoxide and ethylene and propene was prepared in the presence of the composition. In the above, the content of trifluoroacetic acid with respect to palladium is 10 times the molar ratio, and the two stages of the first stage at a polymerization temperature of 78 占 폚 and 84 占 폚 are carried out. The molar ratio of ethylene to propene in the polyketone terpolymer prepared above was 46 to 4. The melting point of the polyketone terpolymer was 220 占 폚, the LVN measured at 25 占 폚 by HFIP (hexa-fluoroisopropano) was 1.4 dl / g, the MI index was 45 g / 10 min and the MWD was 1.8.

The prepared polyketone terpolymer was fed into a twin screw extruder of L / D32 and D40 and extruded through melt kneading at a temperature of 240 DEG C and a screw rotation speed of 250 rpm.

Example 5

Catalysts formed from palladium acetate, trifluoroacetic acid and ((2,2-dimethyl-1,3-dioxane-5,5-diyl) bis (methylene)) bis (bis (2-methoxyphenyl) A linear alternating polyketone terpolymer of carbon monoxide and ethylene and propene was prepared in the presence of the composition. In the above, the content of trifluoroacetic acid with respect to palladium is 10 times the molar ratio, and the two stages of the first stage at a polymerization temperature of 78 占 폚 and 84 占 폚 are carried out. The molar ratio of ethylene to propene in the polyketone terpolymer prepared above was 46 to 4. The melting point of the polyketone terpolymer was 220, the LVN measured at 25 with HFIP (hexa-fluoroisopropano) was 1.4 dl / g, MI (Melt inde x) was 45 g / 10 min and MWD was 2.2.

The prepared polyketone terpolymer was mixed and charged into a twin-screw extruder of L / D32 and D40, and extruded through melt-kneading at a temperature of 240 DEG C and a screw rotation speed of 250 rpm.

Comparative Example

The procedure of Example 1 was repeated using polypropylene as a material of Lotte Chemical Co. instead of the polyketone copolymer.

Property evaluation

The prepared pellets of the above Examples were injection-molded to prepare food-sealed containers. The durability and airtightness of the food-sealed containers were evaluated in the following manner. The results are shown in Table 1 below.

1. Evaluation of durability: Moldings prepared from Examples and Comparative Examples were evaluated for Notched Izod impact strength against ASTM D256, 1/4 inch thick specimens at room temperature.

2. Evaluation of tightness

1) Oxygen permeability test: A food sealed container made of 2.5 mm in thickness was placed in an oxygen permeability measuring device (Mocon, OX-TRAN 2/20), and stabilized with nitrogen for 24 hours at 23 ° C. and 90 RH% After the roughness, the oxygen permeability until the amount of oxygen permeation reaches the equilibrium state is measured

Item  Example 1 Example 2 Example 3  Example 4 Example 5 Comparative Example Impact strength
(kJ / m2) 12 14 16 11 13 7 Oxygen permeability
(cc / pack.day) 0.0075  0.0061 0.0046 0.0060  0.0067 0.152

As shown in Table 1, in Examples 1 to 5, the durability (excellent impact strength of 10 kJ / m ² or more) and hermeticity (oxygen permeability of 0.01 to 0.001 cc / pack.day excellent) And it has proved to be suitable for use as a food sealed container.

Claims (5)

A food sealed container for storing various foods therein,
The sealed container has a Notched Izod impact strength of 10 kJ / m ² or more as measured by ASTM D256, 1/4 inch thick specimen at room temperature,
The oxygen-permeability of the food-sealed container is from 0.01 to 0.001 cc / pack.day at 23 DEG C and 90RH%
The food-sealed container is made of a polyketone copolymer composed of repeating units represented by the following chemical formulas (1) and (2)
The ligand of the catalyst composition used in the polymerization of the polyketone is bis (methylene) bis (bis (2-methoxyphenyl) phosphine Pin)
Wherein the polyketone copolymer has an intrinsic viscosity of 1.0 to 2.0 dl / g and a molecular weight distribution of 1.5 to 2.5.
[Chemical Formula 1]
- (CH2CH2-CO) x-
(2)
- (CH2CH (CH3) -CO) y-
(x and y are mol% of each of the formulas (1) and (2) in the polymer and y / x is 0.03 to 0.3)
The method according to claim 1,
Wherein the polyketone copolymer comprises a catalyst composition comprising a palladium compound, an acid having a pKa value of 6 or less, and a bidentate compound of phosphorus;
Preparing a mixed solvent (polymerization solvent) comprising methanol and water;
Conducting the polymerization in the presence of the catalyst composition and the mixed solvent to prepare a linear terpolymer of carbon monoxide, ethylene and propene;
Removing the remaining catalyst composition from the linear terpolymer with a solvent to obtain a polyketone resin;
Are sequentially manufactured.
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