KR19990065052A - Coextruded heat-adhesive polymer film and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a coextruded heat-adhesive polymer film and a method for manufacturing the same, wherein the polycarboxylic acid is polycondensed with dicarboxylic acid containing 80% by weight or more of terephthalic acid and alkylene glycol containing 80% or more by weight of ethylene glycol to have an ultimate viscosity of 0.5. Preparing a first polymer resin having a ratio of 0.7 to 0.7 dl / gr, dicarboxylic acid containing terephthalic acid and isophthalic acid at a ratio of 90:10 to 75:25 by weight, and alkylene glycol containing 80 wt% or more of ethylene glycol. Polycondensation to prepare a second polymer resin having a melting temperature of 190 to 220 ° C., melting and extruding the first polymer resin and the second polymer resin to produce an unstretched sheet, and totally stretching the unstretched sheet. Longitudinal stretching of at least three stages so as to achieve a 3.5 times or less of crystallinity and 15 J / g or more of crystallization energy, and transverse stretching of the longitudinally stretched film, followed by Melt point of the point to the first polymer resin-the co-extruded heat-adhesive polymer film of the present invention prepared by the method comprising the step of heat treatment for 3 to 10 seconds at a temperature in the range of 20 ℃ high temperature multi-stage stretching and setting the appropriate heat treatment temperature As it has excellent low temperature thermal adhesiveness and excellent mechanical properties, it is very useful as a packaging and industrial material.

Description

Coextruded heat-adhesive polymer film and manufacturing method thereof

The present invention relates to a coextruded heat-adhesive polymer film and a method for manufacturing the same, and specifically, by varying the density of both surfaces of the film through coextrusion and high temperature multistage stretching, excellent mechanical properties and heat-adhesiveness at a low temperature below 100 ° C It relates to a co-extruded polymer film and a method for producing the same that can be used as a packaging material exhibiting excellent properties.

As the industrial structure becomes more complex, as the necessity of a material capable of satisfying various applications increases, there is a growing interest in excellent moldability and light polymer resin. In particular, research and development on this has been actively conducted due to the advantage that the various polymer resins having advantages in different physical properties can be made into a final film having excellent physical properties through a processing method such as copolymerization, co-extrusion.

Among them, polyester resins include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, etc. In particular, polyethylene terephthalate (hereinafter referred to as PET) is physicochemically stable, has high mechanical strength, heat resistance, durability, Due to its excellent chemical resistance and electrical insulation, it is widely used in various industrial products such as medical, electromagnetic, packaging, and photographic film. In particular, it is widely used as a packaging container or packaging film for food containers, beverage containers, etc., because it has some hygienic properties required for food packaging, high stability during regeneration for environmental protection, and easy handling. However, in order to be used for applications requiring heat adhesiveness, a process of coating or laminating an adhesive or other resin on a PET film in a manufacturing process requires a process of providing heat adhesiveness.

However, it is difficult to maintain the adhesion improving effect of the final film only by coating with an adhesive or other resin, and in the case of lamination, even if the thermal adhesiveness is improved, the process is complicated and requires an additional process called lamination. Although the cost of the film is high, it is not preferable in terms of economics, and heat adhesiveness is imparted, but there is also a problem that the inherent properties of the polyester resin as the base film are weakened.

Accordingly, the present invention provides excellent mechanical properties while having thermal bonding properties at low temperatures by manufacturing different surface densities of films made by simultaneously forming a heat-bonding layer and a polyester substrate through co-extrusion, high temperature multi-stretching and heat treatment at a specific temperature. Its purpose is to provide a film that can be used in various ways for various purposes.

1 is a schematic diagram of a three stage longitudinal drawing apparatus used in the present invention. In Figure 1, 1 to 3 rolls are preheating rolls, 4 rolls are the first stage stretching rolls, 5 rolls are the cooling rolls, 6-7 rolls are the second stage preheating rolls, 8 rolls are the second stage stretching rolls, and 9 rolls are The third stage stretching rolls and rolls 10 to 11 are cooling rolls, and 4 ', 5', 8 ', 9', and 10 'are roll rolls.

In order to achieve the above object, in the present invention, in the coextruded polymer film composed of a first polymer resin layer and a second polymer resin layer formed on at least one surface thereof, the first polymer resin layer has an extreme viscosity of 0.5 to 0.7. dl / gr and formed of a polyester having an ethylene terephthalate content in the main repeating unit of 80% by weight or more, and the second polymer resin layer has a melting temperature in the range of 190 to 220 ° C and repeats the ethylene terephthalate and ethylene isophthalate repeating units. There is provided a coextruded polymer film, characterized in that it is formed from copolyesters having a weight ratio in the range of 90:10 to 75:25.

In the present invention, the step of polycondensing dicarboxylic acid containing at least 80% by weight of terephthalic acid and alkylene glycol containing at least 80% by weight of ethylene glycol to prepare a first polymer resin having an ultimate viscosity of 0.5 to 0.7dl / gr And polycondensation of dicarboxylic acid containing terephthalic acid and isophthalic acid at a ratio of 90:10 to 75:25 by weight, and alkylene glycol containing 80% by weight or more of ethylene glycol, thereby obtaining a second polymer resin having a melting temperature of 190 to 220 ° C. Preparing a non-stretched sheet by melt co-extrusion of the first polymer resin and the second polymer resin, so that the unstretched sheet has a total longitudinal draw ratio of 3.5 times or less and a crystallization energy of 15 J / g or more. Longitudinal stretching at least three stages and transversely stretching the longitudinally stretched film, and then at a temperature ranging from the melting point of the second polymer resin to the melting point of the first polymer resin-20 ° C. The method of producing a coextruded polymer film comprising the step of heat treatment of 3 to 10 seconds is provided.

Hereinafter, the present invention will be described in more detail.

The coextruded polymer film of the present invention includes a first polymer resin layer and a second polymer resin layer, wherein the first polymer resin used in the first polymer resin layer contains dicarboxylic acid and ethylene glycol containing 80 wt% or more of terephthalic acid. Is prepared by polycondensation of an alkylene glycol containing at least 80% by weight in the presence of a dispersant, an electrostatic agent, a crystallization accelerator, an antiblocking agent and / or an inorganic lubricant as conventional catalysts and additives, and the obtained resin has an intrinsic viscosity of 0.5 Suitably in the range from 0.7 dl / gr.

At this time, an aromatic dicarboxylic acid is used as the dicarboxylic acid, and specific examples thereof include dimethyl terephthalate, terephthalic acid, dimethylisophthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxyethane dicarboxylic acid, and diphenyldicarboxylic acid. , Diphenyl ether dicarboxylic acid, anthracene dicarboxylic acid, α, β-bis (2-chlorophenoxy) ethane-4,4-dicarboxylic acid, and the like. Among these, dimethyl terephthalate and terephthalic acid are preferable. In addition, as the alkylene glycol, ethylene glycol, trimethylene glycol, tetramethyl glycol, pentamethylene glycol, hexamethylene glycol or hexylene glycol may be used, and ethylene glycol is preferable.

The second polymer resin used in the second polymer resin layer of the present invention is an alkylene glycol containing at least 80% by weight of a dicarboxylic acid component and ethylene glycol containing terephthalic acid and isophthalic acid in a ratio of 90:10 to 75:25 weight ratio. Is a copolyester prepared by mixing and polycondensing by adding a catalyst and an additive as in the case of preparing the first polymer resin.

In forming the copolyester as the second polymer resin, the content of the repeating unit of ethylene isophthalate in the main repeating unit is preferably 10 to 25% by weight, and if the content of ethylene isophthalate is less than 10% by weight, the second Crystallization of the polymer resin proceeds rapidly, resulting in poor thermal adhesion, whereas when the content exceeds 25% by weight, the melting temperature of the resin is lowered and deteriorates in the feed block during coextrusion with the first resin layer to produce a film. It may cause process troubles such as breakage. The second polymer resin preferably has an intrinsic viscosity value in the range of 0.6 to 0.75 dl / gr.

The unstretched sheet formed of two layers may be obtained by melt coextrusion using the first polymer resin and the second polymer resin prepared as described above. The thickness of the second polymer resin layer in the coextrusion process is adjusted to 10 to 40%, preferably 15 to 30% with respect to the total thickness of the unstretched sheet.

Subsequently, the polyester unstretched sheet (F) was preheated in rolls 1 to 3 using a three-stage longitudinal drawing apparatus as illustrated in FIG. 1, and then first stretched and cooled in rolls 4 and 5, respectively. After preheating again on rolls 6 to 7, the second stage longitudinal stretching between rolls 8 and 9, and the third stage longitudinal stretching between rolls 9 and 10 were carried out to finish the longitudinally stretched sheet F '. Manufacture.

In the present invention, each longitudinal drawing in the three-stage longitudinal drawing process is carried out in a draw ratio of 1.5 to 2.5 times at a temperature in the range of 120 to 130 ℃, so that the total longitudinal draw ratio is 3.5 times or less. The total longitudinal draw ratio is defined as the product of the longitudinal draw ratios in each step in the longitudinal direction.

Moreover, it is preferable to make the crystallization energy of a longitudinal stretch sheet into 15 J / g or more by performing high temperature multistage longitudinal stretch of three or more steps as mentioned above. The crystallization energy of 15 J / g or more means that the energy generated in the process of crystallization is above a certain level, and implies that the orientation determination of the coextruded longitudinally stretched sheet is below a certain level. If the crystallization energy is less than 15 J / g, the orientation determination proceeds less, resulting in reduced break and nonuniform stretching in the subsequent stretching process.

On the other hand, when the multi-stage longitudinal drawing conditions of three or more stages are not satisfied, there is a problem in that the total longitudinal drawing ratio is 3.5 times or less and the crystallization energy cannot be 15 J / g or more in the longitudinal drawing process.

The longitudinally stretched sheet is stretched 2.5 to 4 times in the transverse direction at a temperature in the range of 110 to 140 ° C, and the melting point of the second polymer resin to the melting point of the first polymer resin-a temperature in the range of 20 ° C, preferably After heat treatment at a temperature of 220 ° C. or higher for 3 to 10 seconds, preferably 5 to 7 seconds, and then quenching to obtain a heat adhesive film of the present invention.

In the manufacture of the heat-adhesive co-extruded polymer film of the present invention, in order to give low-temperature heat-adhesive properties to the film, the crystallization of the second polymer resin layer is suppressed to the maximum to lower the glass transition temperature of the heat-adhesive layer, and also to support the first polymer. It is preferable that a resin layer has a stable crystallization structure.

After the biaxial orientation, thermal crystallization occurs during the heat treatment process, and the rate of thermal crystallization of the first resin layer and the second resin layer is different, so that the crystallization of the first resin layer proceeds rapidly and the second resin layer is formed at a temperature above the melting point. As the surface is heated, the alignment crystals are released. In the heat treatment step, the density of the first polymer resin layer is preferably 1.39 or more, and the surface density of the second polymer resin layer is preferably 1.36 or less.

According to this method, the density of both sides of the film is changed so that the coextruded polymer film of the present invention has excellent thermal properties while maintaining excellent mechanical properties.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to the following Examples. Performance evaluation of the film was carried out in the following manner.

(1) melting temperature

The melting temperature of the resin was measured using a differential thermal analyzer (DSC-7, Perkin Elmer). The temperature was raised to 300 ° C. to melt the sample, followed by quenching, and then raising the temperature at a rate of 20 ° C./min. .

(2) Heat adhesiveness (peel strength)

The thermal adhesion was evaluated by placing the film on a rod heated to 140 ° C., pressing it for 1 second at a pressure of 40 psi, and then performing a 180 degree peeling test to measure the peel strength.

(3) Adhesion start temperature

The film was placed on the rod while the heated rod temperature was changed, and the film was pressed at a pressure of 40 psi for 1 second, and then subjected to a 180 degree peeling test.

(4) number of breaks

The number of breaks occurring during the transverse stretching process of the polyester film 72 hours was measured.

(5) film thickness

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

(6) crystallization energy

The crystallization energy of the longitudinally stretched sheet was measured at a temperature increase rate of 20 ° C./min through a differential calorimeter (DSC, Perkin Elmer).

(7) sheet density

It was measured using a density gradient tube according to ASTMD 1505.

(8) surface density

The absorption peak intensity of the trans-conformation of ethylene glycol in the copolyester structure was measured using a FTS-60 FT-IR AIR apparatus from DigiLab.

Example 1

After terephthalic acid and ethylene glycol were mixed in a 1: 2 equivalent ratio, a polycondensation catalyst and a thermal stabilizer were added to the mixture to carry out a polycondensation reaction, and then, under nitrogen atmosphere, about 2 hours at 120 ° C. and about 3 hours at 170 ° C. By drying, a polyester resin as a first polymer resin having an intrinsic viscosity of 0.62 dl / gr 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 a polycondensation catalyst and a heat stabilizer were added to the mixture, followed by a polycondensation reaction to give an intrinsic viscosity of 0.66. A solidified copolyester resin (melting temperature: 200 ° C.) of dl / gr was prepared. The resin was dried under a nitrogen atmosphere at about 80 ° C. for about 200 minutes, at 120 ° C. for about 120 minutes, and at 182 ° C. for about 180 minutes to prepare a second polymer resin.

Chips of the first polymer resin having an intrinsic viscosity of 0.62 dl / g and the second polymer resin having a diameter of 0.66 g / l are 20m using two extruders and a feed block equipped with a feed block having a thickness ratio of 80:20. It melt-extrudes at the sheet | seat shaping | velocity rate / min, adheres to a 30 degreeC cooling roll, and obtains an unoriented coextrusion sheet.

The unstretched sheet was stretched 3.5 times in the longitudinal direction and 3.5 times in the transverse direction using a high temperature multistage stretching apparatus, followed by heat treatment at 220 ° C. for 5 seconds to obtain a biaxial thickness of 20 μm and a strength of 19.4 kgf / mm ² . A stretched coextruded polymer film was obtained. In this case, the thickness of the coextruded film was 16 μm in the first polymer resin layer and 4 μm in the second polymer resin layer when measured using a scanning electron microscope (SEM).

The characteristics of the longitudinally stretched sheet and the polymer film prepared as described above were evaluated according to the evaluation method described above, and the results are shown in Table 1.

As shown in Table 1 below, the thermal adhesive peel strength of the polymer film prepared in this example was 650 gf / inch, and the bonding start temperature was 90 ° C., and the thermal bonding property was relatively low. The surface density of the second resin layer (heat adhesive layer) surface was 1.351 and the density of the first resin layer (PET) surface was 1.392.

Example 2

A polymer film was manufactured in the same manner as in Example 1, except that the film was prepared by heating the heat setting temperature at 240 ° C. to 20 ° C. in Example 1, and then the properties of the film were evaluated in the same manner as in Example 1, followed by the following results. Table 1 shows.

Example 3

In Example 1, except that the film was manufactured by lowering the total draw ratio to 2.86, the polymer film was prepared in the same manner as in Example 1, the properties of the film were evaluated in the same manner as in Example 1, and the results are shown in Table 1 below. Indicated.

From the following Table 1, when various components and manufacturing process parameters for the heat-adhesive film of the present invention maintain values within the preferred ranges defined above, the polymer film produced under these conditions is characterized in terms of physical properties and low temperature heat-adhesive properties. It can be seen that it is generally good.

Comparative Example 1

A polymer film was prepared in the same manner as in Example 1 except that the total longitudinal draw ratio was 4.0, and the crystallization energy of the longitudinally stretched sheet was 15 J / g or less. In this case, the orientation crystallization at the time of longitudinal stretching progresses to the adhesion start temperature of 105 ° C., resulting in poor low temperature adhesion properties and an increase in the number of breaks, resulting in poor processability. These results are shown in Table 1.

Comparative Example 2

The thermal crystallization of the second polymer resin layer at the time of heat setting was carried out as a result of evaluating the film properties by producing the polymer film in the same manner as in Example 1 except that the heat setting temperature was lowered at 180 ° C which is below the melting point of the second polymer resin in Example 1. Due to the increase in the surface density, there was no thermal adhesion of the laminated film. These results are shown in Table 1.

Comparative Example 3

In Example 1, the film was prepared under the same conditions and the film properties were evaluated, except that the roll temperature during drawing was lowered to lower the crystallization energy of the longitudinally stretched sheet. These results are shown in Table 1.

As can be seen from the above, according to the present invention, in the co-extruded film composed of PET / copolymer PET, it is a packaging and industrial material having excellent low temperature thermal adhesiveness and excellent mechanical properties at the same time by setting high temperature multi-stage stretching and proper heat treatment temperature. Very useful film can be produced.

Claims (5)

In the coextruded polymer film comprising a first polymer resin layer and a second polymer resin layer formed on at least one side thereof, the first polymer resin layer has an ultimate viscosity of 0.5 to 0.7 dl / gr and an ethylene tere of the main repeating unit. The second polymer resin layer, formed from a polyester having a phthalate content of 80% by weight or more, has a melting temperature in the range of 190 to 220 ° C and an ethylene terephthalate and ethylene isophthalate repeating unit in a range of 90:10 to 75:25 weight ratio. A coextruded polymer film formed from copolyester. The method of claim 1, The thickness of the second polymer resin layer is 10 to 40% of the total polymer film thickness, characterized in that the film. Polycondensing dicarboxylic acid containing at least 80% by weight of terephthalic acid and alkylene glycol containing at least 80% by weight of ethylene glycol to prepare a first polymer resin having an intrinsic viscosity of 0.5 to 0.7 dl / gr; terephthalic acid and isophthalic acid Preparing a second polymer resin having a melting temperature of 190 to 220 ° C. by polycondensing dicarboxylic acid containing 90:10 to 75:25 by weight and an alkylene glycol containing 80% by weight or more of ethylene glycol, Melt co-extruding the first polymer resin and the second polymer resin to produce an unstretched sheet, wherein the unstretched sheet is stretched in three or more stages so that the total stretch ratio is 3.5 times or less and the crystallization energy is 15 J / g or more. And transversely stretching the longitudinally stretched film, followed by heat treatment for 3 to 10 seconds at a temperature ranging from a melting point of the second polymer resin to a melting point of the first polymer resin at -20 ° C. Method of producing a coextruded polymer film comprising the step of. The method of claim 3, wherein And in the melt coextrusion step, the thickness of the second polymer resin layer is 10 to 40% of the total polymer film thickness. The method of claim 3, wherein And performing the heat treatment so that the surface density of the first polymer resin layer is 1.39 or more and the surface density of the second polymer resin layer is 1.36 or less.