JP3135270B2 - Transparent polyester film, sheet and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film and sheet having high crystallinity and excellent transparency, and a method for producing the same.

[0002]

2. Description of the Related Art Aromatic polyesters represented by polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) have excellent heat resistance, balance between mechanical strength and gas permeability. Due to its excellent physical properties, it is widely used as engineering plastics in a wide range of fields. Of these polyesters, PBT exhibits high crystallinity and thus can be said to exhibit the above-mentioned excellent properties.However, it cannot be used for applications requiring transparency because of its high crystallinity. Was. In addition, since the crystallization rate of PET is low, it is relatively easy to obtain a low-crystalline transparent film by rapidly cooling the molten polymer.
In this state, mechanical strength, gas permeability resistance, and the like are insufficient. Therefore, it is necessary to promote crystallization by annealing.
However, if the annealing temperature is increased in order to increase the crystallization efficiency, the opacity becomes cloudy. If the crystallization efficiency is increased by an additive such as a nucleating agent, transparency is lost due to the additive itself. Further, a polymer having high crystallinity can be obtained by gradually cooling from a molten state, but a product having high transparency cannot be obtained due to scattering of visible light by spherulites.

[0003]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have used an aromatic copolyester into which a specific comonomer unit has been introduced as a raw material polyester, and By treating the film and sheet obtained therefrom under specific conditions, it has been found that a film or sheet having high crystallinity and not losing transparency without being whitened even under a heating atmosphere can be provided. It has been completed. That is, the present invention relates to the present invention, wherein 5 to 30 mol% of the repeating units are combined with isophthalic acid and / or orthophthalic acid or an ester-forming derivative thereof with 1,4-
Copolymerized polyester resin consisting of ester units with butanediol, and the remaining repeating units mainly consisting of ester units of terephthalic acid or its ester-forming derivative and 1,4-butanediol (provided that the comonomers and
Using an alkylene oxide adduct of hydroquinone
The film or sheet obtained by melt-molding is rapidly cooled to prepare a film or sheet having a low crystallinity, and aged at a temperature selected so that the following formula (1) is obtained.
By performing the heat treatment at a temperature within the range of (2) and the following formula (3), the relative crystallinity is increased by 20% or more, and the haze value is 20%.
%; And a method for producing a transparent polyester film and sheet characterized by maintaining a haze value of 20% or less even after heat treatment at 120 ° C. It is. Formula (1) T _a ≦ T _cc (° C.) Formula (2) T _g ≦ T _b ≦ T _m −2 (° C.) Formula (3) T _b > T _a (° C.) (where _Ta : aging temperature ( ℃) T _b : heat treatment temperature (℃) T _cc : heating rate by differential thermal analysis based on JIS K7121
The resin measured at 10 ° C. / min cold crystallization temperature (℃) T _g: heating rate by differential thermal analysis method based on JIS K7121
Glass transition temperature (° C) of resin measured at 10 ° C / min _Tm : Heating rate by differential thermal analysis based on JIS K7121
(Melting point of resin measured at 10 ° C./min (° C.)) Starting material compounds necessary for forming the copolymerized polyester constituting the present invention will be described step by step. First, starting material compounds required for forming a terephthaloyl group Is terephthalic acid and a derivative thereof, and examples thereof include one or more selected from dialkyl esters or diacylated products. Preferred among these are terephthalic acid and its dialkyl esters, and particularly preferred is dimethyl terephthalate. The oxyalkyleneoxy group forming the butylene terephthalate unit of the copolymerized polyester constituting the present invention is introduced by using 1,4-butanediol as a monomer material.
Examples of the raw material compound that forms the isophthaloyl group or the orthophthaloyl group, which is the most characteristic structural unit of the copolymerized polyester constituting the present invention, include isophthalic acid and its derivatives, and orthophthalic acid and its derivatives. , Dialkyl esters or diacylated products. Of these, preferred are isophthalic acid and its dialkyl ester, or orthophthalic acid and its dialkyl ester, and particularly preferred are dimethyl isophthalate and dimethyl orthophthalate. The value of the molar fraction ratio of the isophthaloyl group or the orthophthaloyl group to all the structural units is 0.05 to 0.0 for the isophthaloyl group or the orthophthaloyl group alone, and for both.
It is necessary to be 30 and particularly preferably 0.1 to 0.25
It is. If the above value is less than 0.05, it is difficult to prepare a film or sheet having a low degree of crystallinity and excellent transparency because the crystallization rate is too high, and particularly, a sheet having a thickness of 0.5 mm or more is prepared. In this case, 0.1 or more is preferable. or,
If it is larger than 0.30, the physical properties such as the mechanical strength and gas permeability of the film or sheet and the heat resistance are reduced.

[0004] In producing the copolymerized polyester, a small amount of other components other than the above-mentioned essential starting materials can be used according to the intended use. Examples of other components used herein include diphenic acid, aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, adipic acid, aliphatic dicarboxylic acids such as sebacic acid, and 1,4-cyclohexanedicarboxylic acid. Alicyclic dicarboxylic acids and dialkyl esters or diacylates thereof , 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, 4,4′-diphenol, 4,4 ′
-[1,4-phenylenebis (1-methylethylidene)]
Aromatic dihydric phenols such as bisphenol, bis (4-hydroxyphenyl) ether and 2,6-dihydroxynaphthalene and their adducts of 2 to 4 moles of ethylene oxide, 2 moles of adduct of propylene oxide, ethylene glycol, 1,3-propane Aliphatic diols such as diols, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,10-decanediol, 1,4
-Cyclohexanediol, alicyclic diols such as 1,4-cyclohexanedimethanol, trifunctional or higher polyfunctional compounds such as trimethyl trimesate, trimethyl trimellitate, trimethylolpropane and pentaerythritol, stearyl alcohol, o-benzoyl benzoate Monofunctional compounds such as acids, polyalkylene glycols such as polybutylene glycol, and the like can be mentioned, and one or more of these can be used.

The copolymerized polyester resin constituting the present invention preferably satisfies the following formula (4).
When ΔHc is larger than 35 (J / g), it becomes difficult to prepare a film or sheet having a low crystallinity, and the effect of the present invention is significantly lost. Particularly preferably, 0 ≦ Δ
Those satisfying Hc ≦ 30 (J / g) are preferable. Equation (4) ΔHc ≦ 35 (J / g) (However, ΔHc is the cooling heat of crystallization (J / g) when the resin melted at 240 ° C. is cooled at a cooling rate of −500 ° C./min by differential thermal analysis. g).) These copolymerized polyesters can be prepared by a conventionally known condensation reaction,
It can be produced by interfacial polycondensation, melt polymerization, solution polymerization, or the like utilizing a transesterification reaction. Further, by using a solid-phase polymerization method in which the obtained resin is subjected to a heat treatment under reduced pressure or in the presence of an inert gas, a product having a higher degree of polymerization can be obtained.

As a method for forming a film or a sheet from a molten resin, a T-die method or an inflation method can be used, but the T-die method is preferable. From the viewpoint of moldability, it is desirable that the intrinsic viscosity of the copolymerized polyester resin is 0.7 or more. Here, the intrinsic viscosity is a value measured in orthochlorophenol at 25 ° C. In addition, in the method of the present invention, it is necessary to quench rapidly after extrusion to temporarily form a low crystallized film or sheet.

If the thickness of the film or sheet is mentioned, if the thickness of the film or sheet is large, only the surface of the film or sheet tends to be transparent by rapid cooling, and the inside tends to be gradually cooled and whitened. When the thickness of the film or sheet is too small, the mechanical strength of the film or sheet itself is not exhibited, and the excellent effect in practical use is reduced. Therefore, when a preferable range of the thickness of the film or sheet is specified by a numerical value, it is 0.01 to 2.5 mm, more preferably 0.02 to 1 mm. In addition, film,
After manufacturing the sheet, uniaxial or biaxial stretching may be performed to a predetermined thickness.

In the present invention, after preparing the film and the sheet, the film and the sheet are aged at a temperature selected so as to obtain the following formula (1). This is performed by a method of immersing a film or sheet in a heat medium of a predetermined temperature such as hot water, a method of throwing into a dryer of a predetermined temperature, a method of blowing hot air, or a method of radiant heat such as infrared rays. . Equation _{(1) T a ≦ T cc} (℃) ( where, T _a: the aging temperature T _cc: heating rate by differential thermal analysis method based on JIS K7121
(Cold crystallization temperature (° C.) of resin measured at 10 ° C./min) If the aging temperature is higher than T _cc (° C.), the film or sheet becomes cloudy due to rapid crystallization, which is not preferable. The time required for aging depends on the content of isophthaloyl or orthophthaloyl groups in the copolymerized polyester resin, the aging temperature, and the thickness of the film or sheet. A longer ripening time is required as the content of the isophthaloyl group or the orthophthaloyl group is higher, the aging temperature is lower, or the thickness of the film or sheet is larger. On the other hand, if the aging temperature is low, aging for an extremely long time is required, which is not preferable in terms of productivity and the like, and the aging temperature is preferably 30 ° C or higher.
The film or sheet is aged at a temperature selected so as to satisfy the above formula (1), and is further heat-treated at a temperature within the range of the following formulas (2) and (3). Equation (2) T _g ≦ T _b ≦ T _m −2 (° C.) Equation (3) T _b > T _a (° C.) (However, T _b : heat treatment temperature (° C.) T _g : differential thermal analysis based on JIS K7121 Heating rate by method
Glass transition temperature of resin measured at 10 ° C / min (° C) _Tm : Heating rate by differential thermal analysis based on JIS K7121
(Melting Point of Resin Measured at 10 ° C./min (° C.)) A particularly preferred temperature range is T _g + 5 ≦ T _b ≦ T _m −10 (° C.). When _Tb is lower than the glass transition temperature, the time required for the heat treatment becomes too long, which is not preferable. Conversely, when the temperature is increased, the processing time can be shortened, but when the temperature is too close to the melting point, partial melting due to uneven heat treatment occurs. Is not preferred. By performing such a treatment, the relative crystallinity of the film or sheet is improved by 20% or more while maintaining transparency, and thereafter, the transparency and high crystallinity are stably maintained. For example, as shown in Example 1 below, 54.9%
Has a relative crystallinity of 20% or more by aging and heat treatment, has a high crystallinity of 92%, and is transparent.

In the present invention, it is desirable to prepare a film or sheet having a low crystallinity once, and then to increase the relative crystallinity (CR) of the film or sheet by 20% or more by aging and heat treatment. If the preferred relative crystallinity of the conductive film or sheet is specified, CR is 70% or more. That is, if the relative crystallinity of the film or sheet is less than 70%, advantages based on crystallinity such as gas permeability resistance, heat resistance, and surface hardness are not exhibited, and the crystallinity of the final product is 70% or more. Those are practically desirable, and according to the present invention, such films and sheets can be provided. Here, the relative crystallinity is a value determined by a DSC measurement method described later.

Further, since the transparency of a film or sheet greatly depends on the smoothness of its surface, when high transparency is required, it is desirable that the press plate or the cooling roller is as smooth as possible. However, the film,
When a profound feeling is required for the sheet, it is possible to make the surface of the film or sheet irregular so as to reduce the transparency. If the haze value of a film or sheet subjected to these treatments exceeds 20%, the advantage based on transparency is lost. Therefore, defining a preferable range for the transparency of the transparent film or sheet, the haze value is 20%. Less than, 120
It is practically desirable to maintain a haze value of 20% or less even after heat treatment at ℃, and according to the present invention, it has become possible to provide such a film or sheet. In the composition of the present invention, other thermoplastic resins and inorganic fillers can be supplementarily used depending on the purpose as long as the effects of the present invention are not impaired.

[0011]

As described above, the highly crystalline transparent film or sheet made of the specific resin obtained by the present invention is:
A melt-formed film or sheet is quenched to prepare a transparent film or sheet having a low degree of crystallinity, which is heat-treated after aging to increase the degree of crystallinity without impairing the transparency. Has excellent effects. 1) The resin has high heat resistance, maintains a haze value of 20% or less without deteriorating transparency even under high temperature conditions of about 120 ° C, and has excellent gas barrier properties and heat shrink resistance due to its high crystallinity. It is suitable for packaging food for cooking range. 2) Since transparency is imparted without impairing the mechanical properties, it can be used for a window glass protective film and the like.

[0012]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
The main measurement conditions of the characteristic values are as follows. (1) Melting point, cold crystallization temperature, glass transition temperature Measured at a heating temperature of 10 ° C./min by differential thermal analysis (DSC) based on JIS K7121. (2) Heat of crystallization during quenching The resin melted at 240 ° C by differential thermal analysis was cooled at a cooling rate of -500 ° C / min, and the heat of cooling crystallization [ΔHc (J /
g)] was measured in a helium atmosphere. (3) Relative crystallinity A film or sheet is cut out into a sample for DSC measurement and DS
This was performed using a C apparatus. The calculation of the relative crystallinity is based on the following equation. CR = [(ΔHm− | ΔHcc |) / | (ΔHc) _HOMO |] × 100 (%) (However, ΔHm; heat of crystal fusion measured by heating at 10 ° C./min ΔHcc; heating measured at 10 ° C./min Heat of transition of the cold crystallization peak due to (ΔHc) _HOMO ; heat of crystallization by measuring the temperature of the unmodified PBT homopolymer from the molten state at 10 ° C / min.) In order to determine the relative crystallinity inherent in the sample for melting, the absolute value of the heat of transition (ΔHcc) of the cold crystallization peak is subtracted from the heat of crystal fusion (ΔHm). (4) Haze value A film or sheet was cut out and measured based on JIS K7105. (5) Oxygen permeability A film or sheet was cut out and measured based on JIS K7126. (6) Haze value and relative crystallinity after heating A film or sheet is cut out, put into a blow dryer at a temperature of 120 ° C for 10 minutes, and the haze value is determined based on JIS K7105. The relative crystallinity was determined.

Production Example 1 (Synthesis of Polyester A) 277.8 parts by weight of dimethyl terephthalate, 30.9 parts by weight of dimethyl isophthalate, and 286.4 parts by weight of 1,4-butanediol were stirred together with a predetermined amount of a transesterification catalyst, tetrabutyl titanate, and a stirrer and distilled. After charging into a reactor equipped with an outlet tube and sufficiently purging with nitrogen, the temperature was raised to 160 ° C. under normal pressure, and stirring was started. Further, the temperature was gradually increased, and methanol as a by-product was distilled off. When the temperature reaches 240 ° C,
The pressure in the reactor was gradually reduced, and stirring was continued at a pressure of 0.1 torr for 2.0 hours to obtain a copolymerized polyester resin having an intrinsic viscosity of 0.94. Introduction rate of dimethyl isophthalate is determined by ¹ H-NMR measurement using hexa full fluoroisoquinolin Pas Nord -d ₂ solvent. Subsequently, the polyester resin was pelletized and subjected to solid phase polymerization under a nitrogen stream to obtain a high polymerization degree polyester having an intrinsic viscosity of 1.38. The properties of the obtained polyester were evaluated as described above. Table 1 shows the results. Production Examples 2 and 3 (Polyesters B and C) Melt polymerization and solid phase polymerization were carried out in the same manner as in Production Example 1 except that the addition amounts of dimethyl terephthalate and dimethyl isophthalate were changed to the values shown in Table 1, and various compositions were obtained. A ratio of the copolymerized polyester resin was obtained. The properties of the obtained polyester were evaluated in the same manner as in Production Example 1. Table 1 shows the results.

Production Example 4 (Synthesis of Polyester D) 247.7 parts by weight of dimethyl terephthalate, 61.9 parts by weight of dimethyl orthophthalate, 280.1 parts by weight of 1,4-butanediol, and 6.1 parts by weight of 1,3-propanediol were added to a predetermined amount of an ester. The mixture was charged into a reactor equipped with a stirrer and a distilling tube together with the exchange catalyst, tetrabutyl titanate. After sufficiently replacing the atmosphere with nitrogen, the temperature was raised to 160 ° C. under normal pressure, and stirring was started.
Further, the temperature was gradually increased, and methanol as a by-product was distilled off. When the temperature reached 240 ° C, the pressure inside the reactor was gradually reduced, and stirring was continued at a pressure of 0.1 torr for 2.5 hours.
A copolymerized polyester resin having an intrinsic viscosity of 0.88 was obtained. The introduction ratio of dimethyl orthophthalate was determined by ¹ H-NMR measurement using hexafluoroisopropanol-d ₂ as a solvent. Subsequently, the polyester resin was pelletized and subjected to solid-phase polymerization under a nitrogen stream to obtain a high polymerization degree polyester having an intrinsic viscosity of 1.20. The properties of the obtained polyester were evaluated in the same manner as in Production Example 1. Table 1 shows the results.

Comparative Production Example 1 (Polyester E) Melt polymerization and solid phase polymerization were carried out in the same manner as in Production Example 1 except that the addition amounts of dimethyl terephthalate and dimethyl isophthalate were changed to the values shown in Table 1, to obtain a copolymerized polyester. Obtained. The properties of the obtained polyester were evaluated in the same manner as in Production Example 1. Table 1 shows the results.

Comparative Production Example 2 (Polyester F) Melt polymerization and solid phase polymerization were carried out in the same manner as in Production Example 1 except that the addition amounts of dimethyl terephthalate and dimethyl orthophthalate were changed to the values shown in Table 1, to obtain a copolymerized polyester. Obtained.
The properties of the obtained polyester were evaluated in the same manner as in Production Example 1. Table 1 shows the results.

Comparative Production Example 3 (Polyester G) Dimethyl terephthalate and 1,4-butanediol are shown in Table 1.
The polymer was melt-polymerized and solid-phase polymerized at the monomer ratios shown in Table 1 to obtain polybutylene terephthalate resin (PBT). The properties of the obtained polyester were evaluated in the same manner as in Production Example 1. Table 1 shows the results.

Examples 1 to 4 and Comparative Examples 1 to 3 In order to clarify differences in film and sheet characteristics due to differences in the raw material polyester, quenching conditions from a molten state,
Polyesters A to G were evaluated while keeping the film and sheet thickness, aging conditions and heat treatment conditions constant. That is, 24
Extruding the molten polymer at 0 ° C from a T-die onto a cooling roll at 25 ° C, adjusting the extrusion speed so that the thickness of the film and sheet becomes 0.15mm, melt-molding the film, quenching conditions for the sheet, film and sheet Of the same thickness. These films and sheets were aged in a constant temperature bath at 40 ° C. for 20 minutes, and then placed in a dryer at 100 ° C. for 10 minutes for heat treatment. The transparency and crystallinity of these films and sheets,
Table 2 shows the evaluation results of the gas permeability resistance.

Examples 5 and 6, Comparative Example 4 A film was prepared in the same manner as in Example 3 except that the aging temperature was changed.
A sheet was prepared and evaluated. Table 3 shows the results.

Examples 7 and 8, Comparative Example 5 Films and sheets were prepared and evaluated in the same manner as in Example 3 except that the heat treatment temperature was changed. Table 4 shows the results.

Examples 9 and 10 Films and sheets were prepared and evaluated in the same manner as in Example 3 except that the thicknesses of the films and sheets were changed. Table 5 shows the results.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenji Hijikata 8-8 Fujimidai, Mishima City, Shizuoka Prefecture (56) References JP-A-3-223339 (JP, A) JP-A-3-1066941 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/18 C08G 63/183

Claims (6)

(57) [Claims] (1) 5 to 30 mol% of repeating units consist of ester units of isophthalic acid and / or orthophthalic acid or an ester-forming derivative thereof and 1,4-butanediol, and the remaining repeating units are mainly terephthalic acid. Or a copolymerized polyester resin comprising an ester unit of an ester-forming derivative thereof and 1,4-butanediol
(However, alkylene of hydroquinone as a comonomer
Excluding those using oxide adduct) to quench the melt molded film or sheet to prepare a film or sheet of low crystallinity, after aging at a temperature chosen as a following formula (1), A method for producing a transparent polyester film or sheet, further comprising heat-treating at a temperature within the range of the following formulas (2) and (3). Formula (1) T _a ≦ T _cc (° C.) Formula (2) T _g ≦ T _b ≦ T _m −2 (° C.) Formula (3) T _b > T _a (° C.) (where _Ta : aging temperature ( ℃) T _b : heat treatment temperature (℃) T _cc : heating rate by differential thermal analysis based on JIS K7121
The resin measured at 10 ° C. / min cold crystallization temperature (℃) T _g: heating rate by differential thermal analysis method based on JIS K7121
Glass transition temperature (° C) of resin measured at 10 ° C / min _Tm : Heating rate by differential thermal analysis based on JIS K7121
Melting point of resin measured at 10 ℃ / min (℃) 2. The process for producing a transparent polyester film or sheet according to claim 1, wherein the heat of crystallization of the copolymerized polyester resin satisfies the following formula (4). Equation (4) ΔHc ≦ 35 (J / g) (However, ΔHc is determined by the differential thermal analysis method, and the resin cooled at 240 ° C. is cooled at a cooling rate of −500 ° C./min. g).) 3. The method for producing a transparent polyester film or sheet according to claim 1, wherein the film or sheet is formed by a T-die method. 4. The method for producing a transparent polyester film or sheet according to claim 1, wherein the relative crystallinity of the film or sheet is increased by 20% or more by aging and heat treatment, and the haze value is maintained at 20% or less. 5. A transparent polyester film or sheet obtained by the production method according to claim 1, which maintains a haze value of 20% or less even at a heat treatment at 120 ° C. 6. The film or sheet has a thickness of 0.01 to 2.5 mm.
The transparent polyester film or sheet according to claim 5, which is: