KR100225395B1 - Multi-layered polyester film and method for manufacturing the same - Google Patents

Abstract

In a multilayer film in which a second polyester resin layer and a third polyester resin layer are sequentially laminated on at least one surface of a first polyester resin layer, the first polyester resin layer is a poly repeating unit whose main repeating unit is ethylene terephthalate A resin layer formed of an ester, wherein the second polyester resin layer is a resin layer formed of linear low density polyethylene whose main repeating units are ethylene and alpha olefin, and the third polyester resin layer has ethylene terephthalate and iso The multilayer polyester film according to the present invention, which is a resin layer containing 0.1 to 2.5% by weight of an antistatic agent based on the copolyester of phthalate and the copolyester, has heat adhesiveness, antistatic property, and general physical properties. It is excellent and suitable for use in industry, especially packaging film.

Description

Multilayer Polyester Film and Manufacturing Method Thereof

The present invention relates to a multilayer polyester film and a method for producing the same, and more particularly, to a multilayer polyester film having heat adhesiveness and antistatic property and a method for producing the same.

As the industry diversifies, the necessity of a material capable of satisfying various applications is increasing, and thus, there is a growing interest in excellent moldability and light polymer resin. Polymer resins have various advantages according to their type, and since they can be easily manufactured into final films having desirable physical properties through processing methods such as copolymerization and coextrusion, Research and development are being actively conducted.

Among them, polyesters represented by polyethylene terephthalate (hereinafter referred to as PET) are physically and chemically stable, have high mechanical strength, and are excellent in heat resistance, durability, chemical resistance and electrical insulation, and thus are used in medical, electromagnetic, packaging, and photography. It is widely used in various industrial products such as films. In particular, the polyester resin is widely used as a packaging container or packaging film for food and beverages in that it is an environmentally friendly material having excellent hygiene, easy handling and high stability of regeneration treatment required for food packaging.

On the other hand, in order to be used as a packaging container or a packaging film, the heat sealability is generally required because the sealing property is essentially required to keep the contents of the package safe from external conditions by preventing the entry of particulates and gases. Accordingly, in order to impart heat adhesiveness to the polyester film, a method of coating or laminating an adhesive and other resins and the like to a PET film has been used in the film manufacturing process.

However, it is difficult to maintain the thermal adhesiveness of the final film at a desirable level in the method of coating the adhesive or other resin on the PET film as described above, and even if the laminating method is adopted, the whole according to the addition of the lamination process The problem of the unit cost increase of the final film caused by the complexity of the process can not be avoided, and even though the thermal adhesiveness is improved by lamination, it encounters a serious disadvantage that the inherent properties of the PET base film are weakened.

In addition, when the polyester film is used for packaging, the problem of static electricity generation should be solved. If static electricity is generated in the wrapping paper, the inner packing material sticks to the wrapping paper, thereby deteriorating the appearance or it is difficult to easily take out the contents after opening. In particular, in the case where the contents of the package are precise electronic components, serious damage may be expected in which the contents are damaged by the static electricity generated in the packaging.

Therefore, in order to solve the problem of static electricity generation, many methods related to providing antistatic property to a film have been known conventionally. The prior art is to prepare a final film having an antistatic property by injecting a material that exhibits most antistatic properties with a resin and an additive. However, in the conventional film, as the time passes, the antistatic agent included in the resin layer in the film is transferred to the surface or the other resin layer, so that the antistatic effect after the surface reaction tends to decrease. Therefore, in the case of the antistatic polyester film manufactured using the conventional method, there is a need to solve such disadvantages because it is not suitable as a film used in the field that requires long-term storage.

The technical problem to be achieved by the present invention is to provide a polyester film for packaging which is excellent in heat adhesiveness and antistatic property is maintained for a long time.

Another technical problem to be achieved by the present invention is to provide a method for producing a packaging polyester film having excellent heat adhesiveness and antistatic properties for a long time.

In order to achieve the above technical problem, in the present invention, in the multilayer film in which the second polyester resin layer and the third polyester resin layer are sequentially laminated on at least one surface of the first polyester resin layer, the first polyester number The ground layer is a resin layer formed of polyester having a main repeating unit of ethylene terephthalate, and the second polyester resin layer is a resin layer formed of linear low density polyethylene having a main repeating unit of ethylene and an alpha olefin and the third polyester number. The layer is provided with a multi-layer polyester film, wherein the main repeating unit is a resin layer comprising copolyester of ethylene terephthalate and ethylene isophthalate and 0.1 to 2.5% by weight of an antistatic agent based on the copolyester.

Hereinafter, the multilayer polyester film according to the present invention will be described in detail.

It is preferable that the said 1st polyester resin has an intrinsic viscosity of 0.5-0.7 dl / gr, and the content of ethylene terephthalate which is a repeating unit is 80 weight% or more.

The linear low density polyethylene (LLEPE) forming the second polyester resin has a density of 0.910 to 0.925 and a weight ratio of ethylene and alpha olefins, which are repeating units, of 90:10 to 92: 8. . The second polyester resin layer serves to prevent the antistatic agent described later from being transferred to the surface layer or the other resin layer, and the thickness of the second polyester resin layer is suitably about 3 to 20% based on the total film thickness. The alphaolefin is preferably any one selected from 1-butene, 1-hexene, 1-octene or 4-ethyl 1-pentene.

It is preferable that the copolymer polyester which is a repeating unit which forms the said 3rd polyester resin has the melting temperature of 185-230 degreeC, and the ethylene isophthalate content in the said copolymer polyester is 5-35 weight%. The thickness of the third polyester resin layer is preferably about 3 to 40% based on the total film thickness.

Antistatic agents included in the third polymer layer include N, N-bis (2-hydroxyethyl) alkylamine, oleic acid monoglyceride, oleic acid diglyceride, stearic acid monoglyceride, stearic acid diglyceride, polyoxyethylene sorbbi Preference is given to any one selected from carbon fatty acid esters, polyoxyalkylphenyl ethers and polyethylene glycol fatty acid esters.

In order to achieve the above another technical problem, in the present invention (A) to prepare a first polyester resin by polycondensing dicarboxylic acid having a content of terephthalic acid of 80% by weight or more and alkylene glycol of 80% by weight of ethylene glycol Step, (B) to prepare a second polyester resin formed of linear low-density polyethylene by mixing the ethylene and alpha olefin in a weight ratio of 92: 8 to 90:10, and then adding the mixture to polymerize the content, terephthalic acid content This 65 to 95% by weight of dicarboxylic acid of 5 to 35% by weight of isophthalic acid and alkylene glycol of 80% by weight of ethylene glycol is mixed and 0.1 to 2.5% by weight of the mixture based on the mixture (C) step of preparing a third polyester resin by polycondensation after adding the antistatic agent, at least of the first polyester resin layer (D) step of producing an unstretched sheet by melting and extruding the first, second and third polyester resins so that the second polyester resin layer and the third polyester resin layer are sequentially stacked on one surface thereof; Provided is a method for producing a multilayer polyester film comprising the step (E) of biaxially stretching a sheet.

Hereinafter, the manufacturing method of the multilayer polyester film by this invention is demonstrated in detail.

First, dispersants, electrostatic agents, crystallization accelerators, antiblocking agents, and inorganic lubricants are added to the dicarboxylic acid containing 80% by weight or more of terephthalic acid and the alkylene glycol containing 80% by weight or more of ethylene glycol as dispersants, electrostatic agents, crystallization accelerators, antiblocking agents, and inorganic lubricants. By combining, a first polyester resin having an intrinsic viscosity of 0.5 to 0.7 dl / gr is prepared.

At this time, an aromatic dicarboxylic acid is used as the dicarboxylic acid, and specific examples thereof include dimethyl terephthalic acid, terephthalic acid, dimethylisophthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxyethane dicarboxylic acid, and diphenyldicarboxylic acid. , Diphenyl ether dicarboxylic acid, anthracenedicarboxylic acid or alpha, beta-bis (2-chlorophenoxy) ethane-4,4-dicarboxylic acid, among which dimethyl terephthalic acid or terephthalic acid is particularly preferable.

As the alkylene glycol, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol or hexylene glycol may be used, and ethylene glycol is particularly preferable.

Next, the second polyester of linear low-density polyethylene is mixed by mixing alpha olefins with ethylene monomer in a weight ratio of 92: 8 to 90:10, and then adding and polymerizing an appropriate initiator and a heat stabilizer to the mixture. Prepare a resin.

When the content of the alpha olefin is less than 8% by weight, the so-called antistatic agent blocking property, which prevents the phenomenon of the antistatic agent from transferring to the surface layer or the other resin layer, is inferior, whereas if the content exceeds 10% by weight, the process of processing the multilayer film. There is a problem that the stability is lowered.

Subsequently, an acid component containing terephthalic acid and isophthalic acid in a weight ratio of 95: 5 to 65:35 and an alkylene glycol containing 80 wt% or more of ethylene glycol are mixed, and an antistatic agent is added in an amount of 0.1 to 2.5 weight based on the mixture. % Is added, and then a catalyst and an additive are added and polycondensed as in the case of preparing the first polyester resin to prepare a third polyester resin.

At this time, the proper amount of the antistatic agent is 0.1 to 2.5% by weight, preferably 0.15 to 2.0% by weight based on the polyester resin. If the amount of the antistatic agent is less than 0.1% by weight, fine bubbles are formed on the surface of the film, so that the physical properties of the film are deteriorated and the antistatic property is not improved. On the other hand, when the amount is more than 2.5% by weight, the polyester itself is decomposed This lowers the mechanical properties of the film.

Copolyester forming the third polyester resin is preferably the content of ethylene isophthalate of the repeating unit of 5 to 35% by weight, which is the third polyester resin when the content of ethylene isophthalate is less than 5% by weight Has a problem of poor thermal adhesion due to rapid crystallization, whereas if the isophthalate content exceeds 35% by weight, the melting temperature of the resin is lowered, which may cause process troubles during the manufacturing process of the film. Because there is.

By melt-extruding the 1st polyester resin, the 2nd polyester resin, and the 3rd polyester resin produced as mentioned above, the unstretched sheet | seat in which these three resins were laminated | stacked one by one is obtained. In the melt extrusion process, it is preferable to adjust the thickness of the second polyester resin layer to 3 to 20% based on the total thickness of the unstretched sheet, which is the thickness of the total thickness of the unstretched sheet. If it is less than 3%, the antistatic holding property and processability will be poor, whereas if it exceeds 20%, the mechanical strength of the final polyester film will be lowered and equipment trouble will occur, which makes it difficult to form the film. to be. In addition, due to an increase in the amount of the second polyester resin used, a problem arises in that the manufacturing cost is excessively increased.

The multilayer polyester film according to the present invention is then obtained by biaxially stretching at a draw ratio of 2.5 to 6 times both in the longitudinal direction and the transverse direction with respect to the unstretched sheet.

In addition to the above-mentioned main components, polycondensation catalysts, dispersants, electrostatic agents, crystallization accelerators, antiblocking agents, and inorganic lubricants may be added as additives in the manufacture of the multilayer polyester film according to the present invention. Any conventional one used in the art may be used without particular limitation.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, it is a matter of course that the scope of the present invention is not limited by the following examples and comparative examples. In the following Examples and Comparative Examples, ethylene glycol was used as the polyhydric alcohol for convenience, and the performance evaluation of the prepared final film was carried out by the following method.

(1) melting temperature

Melting temperature of the resin was measured using a differential thermal analyzer (DSC-7, Perkin Elmer Co., Ltd.), the temperature was raised to 300 ℃ to melt the sample, and then quenched and measured again at a rate of 20 ℃ / min.

(2) heat adhesive strength

The film was placed on a rod heated to 140 ° C., pressed for 1 second at a pressure of 40 psi, and the film was peeled off in the 180 degree direction. At this time, the heat-sealing characteristics showing the heat adhesion strength were evaluated by measuring the peel strength. It was also observed whether wrinkles occurred, shrinkage of the film, or cloudiness occurred in the peeling process.

(3) process stability

The breakage frequency of the film was measured for 24 hours and classified into A, B, C, and D based on the following criteria.

A: 1 time or less

B: 5 times or less

C: 10 times or less

D: more than 10 times

(4) film thickness

The thickness of each layer of the multilayer polyester film was measured using a scanning electron microscope (SEM).

(5) Antistatic

Surface resistance (unit: Ω) was measured (20 ° C, 65% relative humidity, applied voltage 500V) using Hewlett-Packard Co., Ltd. insulation resistance meter, and then the antistatic property was evaluated according to the following criteria.

Good: Surface resistance exceeds 10 ¹² Ω

Normal: 10 ¹² Ω surface resistance

Poor: Surface resistance less than 10 ¹² Ω

Example 1

Terephthalic acid and ethylene glycol were mixed in a 1: 2 equivalent ratio. After the polycondensation reaction was carried out by adding a polycondensation catalyst and a heat stabilizer to the mixture, the first polyester resin having an ultimate viscosity of 0.62 dl / gr by drying for 2 hours at 120 ° C. and 3 hours at 170 ° C. under a nitrogen atmosphere. Was prepared.

After mixing 8% of 1-butene as alpha olefin with ethylene monomer and adding an appropriate initiator and a heat stabilizer to the mixture, the reaction mixture was added at a high pressure of about 35000 psi to obtain a second poly having a density of about 0.92 g / cc. An ester resin was prepared.

Terephthalic acid and isophthalic acid were mixed with an acid component composed of a weight ratio of 85:15 and ethylene glycol in a 1: 2 equivalent ratio, and then 0.1% by weight of N, N-bis (2-hydroxyethyl) alkyl amine, an antistatic agent, was added to the mixture. A polycondensation catalyst and a heat stabilizer were added together, and a polycondensation reaction was performed to prepare a solidified copolyester resin (melting temperature: 211 ° C.) having an intrinsic viscosity of 0.60 dl / gr. The obtained resin was dried and solidified in a nitrogen atmosphere at 80 ° C. for 200 minutes, at 120 ° C. for 120 minutes, at 160 ° C. for 120 minutes, and at 182 ° C. for 350 minutes to prepare a third polyester resin having an ultimate viscosity of 0.65 (dl / g). It was.

Using a T-die equipped with two extruders and a feed block, the first polyester resin, the second polyester resin, and the third polyester resin are melted and coextruded, and then adhered to a cooling roll maintained at 30 ° C. to be unburned. The thin sheet was prepared. In this case, it adjusted so that the thickness ratio of a 1st polyester resin layer, a 2nd polyester resin layer, and a 3rd polyester resin layer might be 80:10:10. The unstretched sheet was stretched 3.5 times in the longitudinal and transverse directions, respectively, to prepare a biaxially stretched multilayer polyester film having a thickness of 30 μm and a strength of 19.4 (kgf / mm 2). As a result of measuring using the scanning electron microscope, each layer thickness of the film was 24 micrometers of 1st polyester resin layers, 3 micrometers of 2nd polyester resin layers, and 3 micrometers of 3rd polyester resin layers.

The performance about the multilayer polyester film manufactured as described above was evaluated, and the results are shown in Table 1. As shown in Table 1, the manufactured multilayer polyester film had a heat adhesive peel strength of 625 (gf / inch), no wrinkles occurred, and the evaluation result of antistatic property after 720 hours was also good. In addition, the breakage phenomenon was less than one time during the manufacturing process of 24 hours, and the apparent density, surface resistance, and film breaking strength were excellent.

Example 2-7

The amount of the alpha olefin used in the preparation of the second polyester resin, the amount of the isophthalic acid used in the preparation of the third polyester resin and the thicknesses of the second polyester resin layer and the third polyester resin layer are shown in the table. A multilayer polyester film was prepared in the same manner as in Example 1, except that it was changed as described in Example 1.

The performance on the produced film was evaluated and the results are shown in Table 1. As shown in Table 1, it can be seen that the multilayer polyester film prepared by keeping the components of the film and the manufacturing process parameters within the preferred range of the present invention is generally good in physical properties, heat adhesiveness, antistatic properties, and the like. .

Comparative Example 1-7

The amount of the alpha olefin used in the preparation of the second polyester resin, the amount of the isophthalic acid used in the preparation of the third polyester resin and the thicknesses of the second polyester resin layer and the third polyester resin layer are shown in the table. A multilayer polyester film was prepared in the same manner as in Example 1, except that it was changed as described in Example 1.

The performance on the produced multilayer film was evaluated, and the results are shown in Table 1. As shown in Table 1, in the case of the multilayer polyester film produced with the components of the film and the manufacturing process parameters adjusted out of the preferred range of the present invention, any one or more of the measured properties were found to be poor.

2nd polyester resin layer 3rd polyester resin layer Film properties Thickness fraction ¹ α-olefin content ² Thickness fraction ³ Antistatic Content ⁴ Isophthalic acid content ⁵ Melting temperature Peel strength Initial surface resistance Surface resistance after 30 days Process Stability ⁶ Anti-Eradication after 30 days ⁷ unit % weight% % weight% weight% ℃ gf / in 10 ^x Ω 10 ^x Ω - - Example 1 20 8 20 1.0 18 211 625 12 12 A Good Example 2 20 10 20 1.0 18 211 650 12 12 A Good Example 3 20 Example 4 20 8 30 1.0 18 211 620 12 12 A Good Example 5 20 8 8 1.0 18 211 610 12 12 A Good Example 6 20 8 20 1.0 12 215 500 12 12 A Good Example 7 20 8 20 1.0 25 205 630 12 12 A Good Comparative Example 1 2.5 8 20 1.0 18 211 100 12 14 A Bad Comparative Example 2 30 8 20 1.0 18 211 620 12 12 C Good Comparative Example 3 20 5 20 1.0 18 211 634 12 15 A Bad Comparative Example 4 20 20 20 1.0 18 211 610 12 12 C Good Comparative Example 5 20 8 5 1.0 18 245 40 12 12 A Good Comparative Example 6 20 8 20 1.0 8 180 20 12 12 C usually Comparative Example 7 20 8 20 1.0 40 180 - 12 12 D usually

In Table 1 above,

1. Thickness fraction ¹ : Thickness fraction of 2nd polyester resin layer with respect to the whole film

2. Content of alpha olefin ² : Content of alpha olefin relative to the second polyester resin

3. Thickness fraction ³ : Thickness fraction of the ^3rd polyester resin layer with respect to the whole film

4. Antistatic agent ⁴ : Content of antistatic agent to third polyester resin

5. Isophthalic acid content ⁵ : Content of isophthalic acid relative to the third polyester resin

6. Process stability ⁶ : The breakage frequency of the film was measured for 24 hours and denoted by A, B, C and D.

7. Antistatic property ⁷ : After rubbing the film and the film to induce static electricity, it was evaluated by measuring the amount and time of powder adhering to the powder.

As can be seen from the above, the multilayer polyester film according to the present invention is excellent in thermal adhesiveness, excellent in antistatic holding properties and general properties, and is suitable for use as an industrial, especially packaging film.

Claims (17)

In a multilayer polyester film in which a second polyester resin layer and a third polyester resin layer are sequentially laminated on at least one surface of the first polyester resin layer, The first polyester resin layer is a resin layer formed of polyester whose main repeating unit is ethylene terephthalate, The second polyester resin layer is a resin layer of linear low density polyethylene whose main repeating units are ethylene and alpha olefins. The third polyester resin layer is a multi-layer polyester, characterized in that the main repeating unit is a resin layer containing 0.1 to 2.5% by weight of an antistatic agent based on the copolyester polyester and ethylene terephthalate and isophthalate. film. The multilayer polyester film of claim 1, wherein the first polyester resin has an intrinsic viscosity of 0.5 to 0.7 dl / gr and a content of ethylene terephthalate which is a repeating unit of 80% by weight or more. According to claim 1, wherein the linear low-density polyethylene forming the second polyester resin has a density of 0.910 to 0.925, the weight ratio of ethylene and alpha olefins of the repeating unit is 90:10 to 92: 8 Polyester film. The multilayer polyester film of claim 1, wherein the alpha olefin is at least one selected from the group consisting of 1-butene, 1-hexene, 1-octene and 4-ethyl 1-pentene. The multilayer polyester film of claim 1, wherein the second polyester resin layer has a thickness of 3 to 20% based on the total film thickness. The method of claim 1, wherein the copolymer polyester which is a repeating unit for forming the third polyester resin has a melting temperature of 185 to 230 ° C and an ethylene isophthalate content of 5 to 35% by weight in the copolymer polyester. Multilayer polyester film. According to claim 1, wherein the thickness of the third polyester resin layer is a multilayer polyester film, characterized in that 3 to 40% based on the total film thickness. The antistatic agent according to claim 1, wherein the antistatic agent is N, N-bis (2-hydroxyethyl) alkylamine, oleic acid monoglyceride, oleic acid diglyceride, stearic acid monoglyceride, stearic acid diglyceride, polyoxyethylene sorbitan Multi-layer polyester film, characterized in that at least any one selected from the group consisting of fatty acid ester, polyoxyalkylphenyl ether and polyethylene glycol fatty acid ester. (A) preparing a first polyester resin by polycondensing dicarboxylic acid having a terephthalic acid content of 80% by weight or more and alkylene glycol having a content of ethylene glycol of 80% by weight; (B) preparing a second polyester resin formed of linear low density polyethylene by mixing ethylene and an alpha olefin in a weight ratio of 92: 8 to 90:10 and then adding and polymerizing the mixture; Dicarboxylic acid having 65 to 95% by weight of terephthalic acid and 5 to 35% by weight of isophthalic acid and alkylene glycol having 80% by weight of ethylene glycol are mixed, and the mixture is 0.1 to 2.5 based on the mixture. (C) step of preparing a third polyester resin by polycondensation after adding the antistatic agent by weight; An unstretched sheet is produced by melting and extruding the first, second and third polyester resins so that the second polyester resin layer and the third polyester resin layer are sequentially stacked on at least one surface of the first polyester resin layer. (D) step and A method of producing a multilayer polyester film comprising the step (E) of biaxially stretching the unstretched sheet. 10. The multilayer poly according to claim 9, wherein the first polyester resin prepared in step (A) has an intrinsic viscosity of 0.5 to 0.7 dl / gr, and an content of ethylene terephthalate in the repeating unit is 80% by weight. Method for producing an ester film. 10. The multilayer poly according to claim 9, wherein the alpha olefin used in step (B) is at least one selected from the group consisting of 1-butene, 1-hexene, 1-octene and 4-ethyl 1-pentene. Method for producing an ester film. 12. The method of claim 11, wherein the content of the alpha olefin is 8 to 10% by weight based on the second polyester resin. The method of claim 9, wherein the linear low density polyethylene prepared in step (B) has a density of 0.910 to 0.925. The dicarboxylic acid used in the steps (A) and (C) is dimethyl terephthalic acid, terephthalic acid, dimethylisophthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxyethane dicarboxylic acid, di At least one aromatic dicarboxylic acid selected from the group consisting of phenyldicarboxylic acid, diphenyletherdicarboxylic acid, anthracenedicarboxylic acid and alpha, beta-bis (2-chlorophenoxy) ethane-4,4-dicarboxylic acid. The manufacturing method of the multilayer polyester film made. The method of claim 9, wherein the alkylene glycol used in the steps (A) and (C) is at least any one selected from the group consisting of ethylene glycol, trimethyl glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and hexylene glycol Method for producing a multilayer polyester film, characterized in that one. 10. The antistatic agent according to claim 9, wherein the antistatic agent used in step (C) is N, N-bis (2-hydroxyethyl) alkylamine, oleic acid monoglyceride, oleic acid diglyceride, stearic acid monoglyceride, stearic acid diglyceride. A method for producing a multilayer polyester film, characterized in that at least one selected from the group consisting of a lide, polyoxyethylene sorbitan fatty acid ester, polyoxyalkylphenyl ether and polyethylene glycol fatty acid ester. 10. The multilayer polyester film of claim 9, wherein the melting and extruding process of step (D) is such that the thickness of the second polyester resin layer is 3 to 20% based on the total thickness of the unstretched sheet. Manufacturing method.