KR0157175B1 - Process of preparing plastic film - Google Patents

Abstract

The present invention relates to a method for producing a polymer film. Preparing a polymer resin sheet containing a polyolefin resin and a polyester resin having a sulfonic acid metal salt derivative having an acid value of 1.0 mgKOH / g or less, longitudinally stretching the polymer sheet obtained in the step, and longitudinal stretching in the step The polymer film prepared by transversely stretching the film under the following conditions and then performing heat treatment is excellent in physical properties such as apparent density, surface resistance, breaking strength, thermal shrinkage. In addition, the process was excellent in terms of the frequency of breakage was greatly reduced.

Here, Tg: glass transition temperature (° C) of the polyester resin

Ts: transverse stretching temperature (℃)

Th: Heat treatment temperature (℃)

t: heat treatment time (sec)

Description

Manufacturing method of polymer film

The present invention relates to a method for producing a polymer film, and more particularly, to a method for producing a polymer film which is excellent in light weight and texture, and has good antistatic properties and printability and can be used as a paper substitute.

Polyolefin-based films containing inorganic particles have been used as a substitute for paper used in calendars, advertising papers, high-quality packaging, etc., but they have recently been replaced by polyester films due to poor mechanical strength, heat resistance, oil resistance, and numerical stability.

Polyester is chemical and physically stable, high mechanical strength, excellent heat resistance, durability, chemical resistance, electrical insulation, etc. are widely used in medical and various industrial products. In particular, polyethylene terephthalate has excellent properties such as elastic modulus, dimensional stability, planarization, and the like, and is widely used in various graphic arts as well as magnetic recording media, capacitors, packaging, photographic films, labels, and the like. In recent years, various magnetic cards (credit and communication cards), labels, printer award papers, barcode printer award papers, posters, calendars, maps, dust-free papers, display boards, white boards, photo papers, copy papers, special papers, etc. It is used.

However, the polyester film is excessively stiff and poor in texture, and differs from paper in terms of transparency and color, and has a problem in that the density of the polyester itself is high.

Therefore, various methods have been developed to have a polyester-like texture and light weight while maintaining its excellent properties.

That is, JP-A-62-243120 and JP-A 2-206622 disclose a method of adding inorganic particles to polyester, but adding a large amount of inorganic particles does not reduce the weight of the original polyester. have.

Japanese Laid-Open Patent Publication No. 58-50625 discloses a method for reducing the weight of polyester by blending a blowing agent. However, when the blowing agent is blended, there is a problem in that bubbles are poor in dispersibility and difficult to control particle size.

Further, Japanese Laid-Open Patent Publication No. 57-49648 discloses a method in which fine pores are formed on the film surface and inside by blending and stretching a polyolefin resin in polyester to simultaneously seek surface properties and light weight. However, the film produced by the above method does not have good heat resistance of polyolefin, so the amount of oligomer produced during extrusion molding is increased, and thermal aging is caused, resulting in poor mechanical properties. Information may be lost when used as a use. In addition, the method simply dry mixes the two kinds of resins to be mixed, resulting in uneven mixing and breaking of the film during the film forming and stretching process.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polymer film having low apparent density and excellent texture in consideration of the above problems and excellent in antistatic properties and printability.

In order to achieve the above object, the present invention provides a polymer resin sheet containing a polyolefin-based resin and a polyester resin having a sulfonic acid metal salt derivative having an acid value of 1.0 mgKOH / g or less. There is provided a method for producing a polymer film comprising the step of stretching and laterally stretching the film longitudinally stretched in the above step under the following conditions, and then subjecting to heat treatment.

Here, Tg: glass transition temperature (° C) of the polyester resin

Ts: transverse stretching temperature (℃)

Th: Heat treatment temperature (℃)

t: heat treatment time (sec)

In the present invention, by adding a polyolefin resin and an antistatic agent to the polyester resin and by appropriately controlling the stretching conditions and heat treatment conditions, it is possible to obtain a polymer film having a low apparent density and excellent texture, antistatic properties and printability while improving processability. A method is provided.

Hereinafter, the present invention will be described in detail.

First, a mixture of polyester and polyolefin resin to which a sulfonic acid metal salt derivative is added is heated and melted at a temperature equal to or higher than the melting point of the polyester resin, and then extruded and cooled in the form of a film on a cooling drum including a die to obtain an unstretched sheet. The resultant unstretched sheet is passed between rollers having different rotational speeds and stretched 2 to 4 times in the film advancing direction, wherein the temperature of the sheet conveying roller is preferably maintained at Tg + 10 to Tg + 50 ° C., and the stretched sheet is gradually cooled to room temperature. Must be cooled.

Subsequently, the uniaxially stretched film is transferred to a tenter, and then both ends of the film are gripped with a clip and primaryly stretched in a direction perpendicular to the traveling direction of the film. The film of the present invention is produced by heat-treating the obtained stretched film at a temperature below the melting point, and then trimming both ends of the film through a take-up roll and winding up in a winder.

In the present invention, in the biaxial stretching and heat treatment by melt-extrusion of a mixture of a polyester resin and a polyolefin resin containing a sulfonic acid metal salt derivative, the temperature and time are satisfied simultaneously with the formulas (1), (2) and (3). Adjusting so as to produce a light weight film having an apparent density of 0.8 to 1.2 g / cc.

In other words, the stretching temperature in the lateral direction should satisfy the conditions of Tg + 20 ° C to Tg + 60 ° C. If it is below Tg + 20 ° C, breakage occurs and the incidence of defects in the process increases. This is because the number of pores becomes smaller, resulting in a higher specific gravity.

The heat treatment temperature should be maintained such that Th-Ts is in the range of 80 to 110 ° C., which is lower than 80 ° C., resulting in poor numerical stability of the final film. This is because the specific gravity of the final film increases.

In addition, even if the heat treatment temperature satisfies Equation (2), the heat treatment time should be adjusted so that (Th-Ts) / t remains within the range of 4 to 30, which is less than 4, resulting in poor numerical stability of the final film. In the case of excess, the specific gravity of the final film is increased.

In this invention, polyester polycondenses the acid component which has aromatic dicarboxylic acid as a main component, and the glycol component which has alkylene glycol as a main component. Specific examples of the aromatic dicarboxylic acid include dimethyl terephthalate, tphthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid and diphenyl. Ether dicarboxylic acid, anthracenedicarboxylic α, β-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid, and the like, preferably dimethyl terephthalate or terephthalic acid. Specific examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, hexylene glycol, and the like, and preferably ethylene glycol.

The polyester of the present invention is a homopolyester of at least 70 parts by weight of polyethylene terephthalate, and may be copolymerized within 30 parts by weight. Specific examples of the copolymerization components include diol compounds such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylene glycol, 1,4-cyclohexanedimethanol, 5-sodium sulfolezocin, adipic acid, Dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, and polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid.

In addition, in the polyester, known additives such as polycondensation catalysts, dispersants, electrostatic agents, crystallization accelerators, nucleating agents, antiblocking agents and the like may be added within a range that does not impair the effects of the present invention. . In addition, at least one selected from the group consisting of barium sulfate, titanium dioxide, silicon dioxide, calcium carbonate, magnesium oxide and talc may be added as the inorganic filler, and the amount thereof is preferably within 20% by weight based on the polyester resin. This is because when the weight is more than 20% by weight with respect to the polyester resin, the mechanical properties of the film are lowered and a lighter weight film cannot be obtained.

In the present invention, the sulfonic acid metal salt derivative uses an acid value of 1.0 mg KOH / g or less and represented by the formula (4) as an antistatic agent. The proper amount of the sulfonic acid metal salt derivative is 0.01 to 1.0% by weight based on the polyester resin, which is less than 0.01% by weight, only fine bubbles are generated on the surface of the film, which greatly reduces the physical properties of the film and improves antistatic properties. This is because the effect is insignificant, and when it exceeds 1.0% by weight, decomposition of the polyester occurs, which greatly reduces the mechanical properties of the film. Preferably it is 0.02-0.5 weight%.

The sulfonic acid metal salt derivative usable in the present invention is preferably at least one selected from the group consisting of potassium octylbenzenesulfonate, potassium nonylbenzenesulfonate and potassium undecylbenzenesulfonate. The sulfonic acid metal salt derivative is excellent in heat resistance, and the polymer film to which the sulfonic acid metal salt derivative is added has an excellent adhesion to the coating liquid due to an increase in surface tension. In addition, there is a characteristic to remove the static electricity that adversely affects the magnetic card and the like, which is rapidly spreading in recent years.

When the polyolefin-based resin in the present invention is mixed with polyester and extruded and stretched, fine pores are formed on the film surface and inside due to poor compatibility between the two resins. By using such a property, the surface property and the weight reduction of a film can be pursued simultaneously.

In order for the pores produced in the matrix to have a uniform size and distribution, the melt index of the polyolefin should be between 1.0 and 25 (g / 10 minutes), preferably 2.5 to 15 (g / 10 minutes). This is because if the melt index is less than 1.0, the pores are formed too large, so that the distribution of the pores is poor, the pores protrude to the surface, and the film thickness and appearance are very poor, which also adversely affects the mechanical properties of the film. In addition, when it exceeds 25, since the molecular weight and viscosity of an olefin are too low, it is difficult to form pores inside a film, and the objective lightweight film cannot be obtained.

The mixing ratio of the polyolefin resin is preferably 5 to 35% by weight, preferably 8 to 25% by weight based on the total polymer resin. The polyolefin resin is preferably at least one selected from the group consisting of polyethylene, polypropylene and polymethylpentene. In addition, the biaxial stretching may be performed while mixing the polyester resin and the polyolefin resin through a direct extruder, but in order to increase the mutual dispersibility of the two resins, the primary mixed resin may be manufactured by compounding, followed by melt extrusion to biaxial stretching. It is preferable to make it.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not necessarily limited thereto.

Various performance evaluation on the film and process produced in Examples and Comparative Examples of the present invention was carried out by the following method.

1) apparent density

A density gradient tube consisting of carbon tetrachloride and normal heptane was maintained at 25 ° C. and measured by ups and downs.

2) Antistatic Characteristics (Antistatic Resistance, Surface Resistance Measurement)

Surface resistance was measured using an insulation resistance meter of Hewlett-Packard, USA (20 ° C, relative humidity 65%, applied voltage 500V, unit Ω).

3) Breaking Strength (Using Instron): The tensile strength of the film was measured according to ASTM D 882.

4) Fairness

The number of breaks generated during the film production process during daily production was measured and classified according to the following criteria.

A: less than 1 time, B: 1 to 3 times, C: more than 3 times

5) Numerical stability

After leaving for 30 minutes in an oven at 150 ° C., the changed length was measured and evaluated by calculating the heat shrinkage.

Example 1

Dimethyl terephthalate and ethylene glycol were added in a 1 to 2 equivalent ratio, and a polyethylene terephthalate monomer (bis-2-hydroxyethyl terephthalate) was produced by a transesterification reaction, and the average particle diameter was 0.5 탆 and a cubic crystal structure compared to the polyester resin. 16 g of phosphorus titanium dioxide and 0.64 g of octylbenzenesulfonate were added thereto, followed by a polycondensation reaction to prepare a polyester resin having an intrinsic viscosity of 0.610 dl / g. Then, the obtained polyester resin and 80 g of polypropylene resin having a melt index of 4.5 (80% by weight of polyester resin and 20% by weight of polypropylene based on the total polymer resin) were prepared at an initial inlet temperature of 245 ° C, a final outlet temperature of 260 ° C, and a discharge temperature of 275 ° C. Compounding was mixed under the conditions of to prepare a primary mixed resin. The obtained mixed resin was remelted, extruded through a T-die and quenched on a cooling drum to obtain an unstretched sheet, which was stretched 3.5 times in the longitudinal direction at 95 ° C, and then 3.8 times in the transverse direction at 110 ° C. Then, the film stretched in the transverse direction was heat treated at 200 ° C. for 5 seconds to prepare a biaxially stretched film of the present invention.

Various characteristics of the film were specified and shown in Table 1, which had excellent physical properties with an apparent density of 1.06 g / cc, a surface resistance of 101 ² GPa, a film breaking strength of 18.2 kg / mm2, and a thermal shrinkage rate of 1.5%.

Example 2

In the same manner as in Example 1, the addition amount of the various additives and the polypropylene resin was changed by stretching, heat treatment temperature and heat treatment time within the scope of the present invention as shown in Table 1 to produce a film. The physical properties and processability of the film thus produced were generally good.

Comparative Example 1-10

In the same manner as in Example 1, but the addition amount and stretching of the various additives and polypropylene resin, the heat treatment temperature and heat treatment time to deviate from the present invention as shown in Table 1 to prepare a film. The film thus produced was generally poor in physical properties and processability as shown in Table 1.

As can be seen from the above, the polymer film produced according to the method of the present invention is excellent in physical properties such as apparent density, surface resistance, breaking strength, heat shrinkage. In addition, the process was excellent in terms of the frequency of breakage was greatly reduced.

Claims (5)

Preparing a polymer resin sheet containing a polyolefin resin and a polyester resin having a sulfonic acid metal salt derivative having an acid value of 1.0 mgKOH / g or less; Longitudinal stretching the polymer sheet obtained in the step; And transversely stretching the longitudinally stretched film under the following conditions, and then subjecting the film to heat treatment. Here, Tg: glass transition temperature of the polyester resin (° C) Ts: transverse stretching temperature (° C) Th: heat treatment temperature (° C) t: heat treatment time (sec) The method according to claim 1, wherein the general formula of the sulfonic acid metal salt derivative is represented by the following formula (4). R1 is an alkyl group having 5 to 20 carbon atoms, Me is one selected from the group consisting of Li, Na, K and Mg. The method of claim 1, wherein the sulfonic acid metal salt derivative is added in an amount of 0.01 to 1.0 wt% based on the polyester resin. The method of claim 1, wherein the polyolefin-based resin is at least one selected from the group consisting of polyethylene, polypropylene, and polymethylpentene having a melt index of 1.0 to 25 (g / 10 minutes). The method of claim 1, wherein the polyolefin resin is added in an amount of 5 to 35% by weight based on the total polymer resin.