JPH05239233A - Polyester film - Google Patents

Abstract

PURPOSE:To provide a film excellent in heat resistance and color tone and improved in electrostatic castability. CONSTITUTION:This film is made from a polyester comprising aX10<-4>mol, per mol of the total acid component of polyethylene terephthalate, of a potassium compound (e.g. potassium acetate), bX10<-4>mol of a compound of the formula (wherein M is Na, Li, NH4 or K; and R1 and R2 are each hydrogen, 1-8C alkyl or phenyl) (e.g. sodium sulfoisophthalate) and cX10<-4>mol of a phosphorus compound (e.g. triethyl phosphate), satisfying the formulas: 0.1<=a<=10, 0.1<=b<=10, 0.1<=c<=10, 2.0<=a+b<=10, 0.2<=a/b<=4.0, 0.15<=c/(a+b)<=1.5, and having an intrinsic viscosity of 0.5 or above.

Description

Detailed Description of the Invention

[0001]

The present invention is excellent in heat resistance and color tone,
In addition, the present invention relates to a polyester film having improved castability by electrostatic application.

[0002]

2. Description of the Related Art Today's industrially used polyester, especially polyethylene terephthalate, has a high degree of crystallinity and a high softening point and is excellent in strength, chemical resistance, heat resistance, weather resistance and electric insulation resistance. It exhibits excellent properties and is widely used industrially for fibers, films, and various molded products.

When polyester is used in various industrial fields, it is required to have excellent heat resistance, operability, slipperiness in the final product, transparency, and color tone, and to maintain a preferable surface morphology. ing. Further, particularly in film applications, it is required that the following castability by electrostatic application is excellent.

That is, the polyester film is usually
It is obtained by extruding polyester into a sheet form with a melt extruder and then biaxially stretching it in both longitudinal and transverse directions simultaneously or sequentially, but it is usually the extrusion port in order to make the film thickness uniform and not to lose the transparency of the film. A sheet-like material melt-extruded from gold is applied a high voltage to the sheet-like material between the rotating cooling drums to deposit an electrostatic charge on the surface of the unsolidified sheet-like material, and the sheet is grounded to the surface of the cooling drum. A method of rapidly cooling while closely contacting (hereinafter referred to as an electrostatically applied casting method) is adopted. When the film thickness of a polyester film is constant, the casting speed is rate-determining, and a method of increasing the casting speed is extremely important for improving productivity.

As the properties required of the polyester for films as described above, broadly speaking, both (a) heat resistance for improving operability and (b) electrostatic castability for improving productivity are essential. It is said that improvement of such points,
At present, much effort is being made to improve it.

In order to improve the castability by electrostatic application,
A method of adding a metal salt having a positive charge to polyester is generally used, but sodium salts such as sodium acetate and potassium salts such as potassium acetate cause transparency of the film due to precipitation of particles insoluble in the polyester. It is not preferable because it lowers the temperature, and compounds of magnesium and manganese have been conventionally used.

For example, Japanese Patent Publication No. 56-15730 and Japanese Patent Laid-Open No.
As disclosed in JP-A-55-84322, by adding an appropriate amount of a compound of magnesium or manganese and an alkali metal compound or a phosphorus compound to cause polycondensation, the specific resistance of the molten polyester is lowered and the electrostatic applicability is reduced. There are ways to improve. In this case, a tentative result was seen in terms of improving the castability by electrostatic application. However, magnesium compounds, manganese compounds, and the like all have a catalytic action for the esterification reaction and polycondensation reaction of polyester, and may serve as a catalyst for the thermal decomposition reaction of polyester in some cases.

Usually, as a problem during film production, the polymer is deteriorated by heat at the polymer retention portion during film formation, and the deteriorated polymer causes a large amount of unevenness due to bubbles in the film or coloring. Although there is a problem, these compounds having a polymerization catalytic action also accelerate the deterioration reaction of this polymer, which causes a problem that the operability is significantly impaired.

[0009]

As described above, it has heretofore been considered very difficult to produce a polyester for a film which is excellent in transparency, color tone, castability by electrostatic application and heat resistance. The present invention provides a polyester film that is excellent in transparency, color tone, castability by electrostatic application, and heat resistance.

[0010]

[Means for Solving the Problems] That is, the present invention comprises terephthalic acid and ethylene glycol as main components, and a compound of the following structural formula with a potassium compound a × 10 ⁻⁴ mol per mol of all acid components. Is a polyester containing b × 10 ⁻⁴ mol, a phosphorus compound c × 10 ⁻⁴ mol, and an amount satisfying the following formulas and having an intrinsic viscosity of 0.5 or more. To do.

[0011]

[Chemical 2] (Wherein, M is _{Na, Li, NH 4, K} , R 1, R 2 is hydrogen, an alkyl group having 1 to 8 carbon atoms, a phenyl group) 0.1 ≦ a ≦ 10 0.1 ≦ b ≦ 10 0.1 ≦ c ≦ 10 2.0 ≤a + b ≤10 0.2 ≤a / b ≤4.0 0.15 ≤c / (a + b) ≤1.5

The present invention will be described in detail below. The film of the present invention comprises a potassium compound, a compound represented by the above formula (hereinafter referred to as SIP component) and a phosphorus compound in the above formula to
It is composed of polyester added to satisfy all of the above.

The polyester referred to in the present invention refers to polyethylene terephthalate produced mainly from terephthalic acid and ethylene glycol.
Called PA. ) May contain a dicarboxylic acid component such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl sulfone dicarboxylic acid, adipic acid, and sebacic acid in an amount of about 30 mol%, and ethylene glycol (hereinafter referred to as EG). A glycol such as tetramethylene glycol, neopentyl glycol, or 1,4-cyclohexanedimethal may be contained as a part of about 30 mol%.

The potassium compound referred to in the present invention refers to a carboxylic acid salt of potassium, specifically, potassium acetate, potassium propionate, potassium stearate, potassium benzoate and the like, and potassium acetate is particularly preferable.

The addition amount of [0015] Potassium compounds, relative to the acid component 1 mol of constituting the polyester, 0.1 × 10 ^-4 mol or more, it is necessary to add 10 × 10 ^-4 mol, 0.1 × 10 ^-4
If it is less than the molar amount, the effect of substantially lowering the specific resistance is not exhibited. Further, when it is added in excess of 10 × 10 ⁻⁴ mol, the transparency of the polymer is deteriorated when the polymer is polymerized, and the reaction rate of the polycondensation reaction is slowed, which is not substantial.

As the SIP component, 3,5-di (carbo-
β-Hydroxyethoxy) benzene sulfonate sodium, potassium 3,5-di (carbo-β-hydroxyethoxy) benzene sulfonate, lithium 3,5-di (carbo-β-hydroxyethoxy) benzene sulfonate, 5-sodium sulfo Dimethyl isophthalate, 5-potassium dimethyl sulfoisophthalate, dimethyl 5-lithium sulfoisophthalate, dimethyl 5-sodium sulfoterephthalate, 5-sodium sulfoisophthalic acid, 5-sodium sulfoterephthalic acid, 2,5-di (carbo- Examples thereof include sodium β-hydroxyethoxy) benzenesulfonate and the like, and sodium 3,5-di (carbo-β-hydroxyethoxy) benzenesulfonate (hereinafter referred to as SIPG) and dimethyl 5-sodium sulfoisophthalate (hereinafter referred to as SIPM). .) It is preferred.

The SIP component is added in an amount of 0.1 × 10 ^-4 mol or more, 10 or more with respect to 1 mol of the acid component constituting the polyester.
× 10 ^-4 mol need to be added, is less than 0.1 × 10 ^-4 mol, without effect expression of allowed to drop substantially over the specific resistance, the melt viscosity of the addition of more than 10 × 10 ^-4 mol polymer Is high and the thermal stability is reduced, which is not preferable.

The sum of the amounts of the potassium compound and SIP component added is 2 with respect to 1 mol of the acid component constituting the polyester.
× 10 ^-4 mol or more, it is necessary to add 10 × 10 ^-4 mol, without effect allowed to drop substantially over the resistivity of expression is less than 2 × 10 ^-4 mol, exceed 10 × 10 ^-4 mol Is not preferable because the thermal stability of the polymer is lowered.

The addition amounts of the potassium compound and the SIP component are
,, ~ It is not enough to satisfy the formula. It is essential that the molar ratio a / b of the number of moles a of the potassium compound and the number of moles b of the SIP component to be added is 0.2 or more and 4.0 or less with respect to 1 mole of the acid component constituting the polyester. When a / b is less than 0.2, the content rate of the diethylene glycol component in the polyester (hereinafter abbreviated as D%) becomes high, and when a / b exceeds 4.0, internal particles of potassium compound are precipitated in the polyester. Then, the transparency of the film deteriorates, which is not preferable.

The phosphorus compound referred to in the present invention refers to phosphoric acid, phosphorous acid and their derivatives, specifically, phosphoric acid, phosphorous acid, phosphoric acid-n-butyl phosphate, phosphoric acid-di-i. −
There are propyl, mono-i-propyl phosphate, monooctyl phosphate, dioctyl phosphate, trimethyl phosphate, triethyl phosphate, dibutylhydrogenene phosphite, triphenyl phosphite and the like, but a phosphoric acid triester is particularly preferable. Triethyl phosphate (hereinafter referred to as PT-1) is preferably used. The amount added, 0.1 × 10 ^-4 mol or more relative to the acid component 1 mol of constituting the polyester, it is necessary to add 10 × 10 ^-4 mol, 0.1 × 10 ^-4
If it is less than 10 mol, the thermal stability of the polymer will be lowered, and if it is added in excess of 10 × 10 ⁻⁴ mol, the castability by electrostatic application will be impaired, which is not preferable.

The addition amount of the phosphorus compound is not sufficient to satisfy the formula, and the sum (a + b) of the addition number a of the potassium compound and the addition number b of the SIP component is added to 1 mol of the acid component constituting the polyester. ) And the molar ratio c / (a + b) of the added mole number c of the phosphorus compound must be 0.15 or more and 1.5 or less. If c / (a + b) is larger than 1.5, the castability and transparency for electrostatic application are impaired, which is not preferable, and if c / (a + b) is less than 0.15, heat resistance is deteriorated and both are not preferable. It is preferable to include fine particles such as an organic lubricant and an inorganic lubricant, which are added to improve the slipperiness of the film.

As the fine particles imparting lubricity, there are known inert external particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide and calcium phosphate. Stabilizer,
You may contain additives, such as a coloring agent, antioxidant, and a defoaming agent.

Further, the polycondensation reaction is carried out in the presence of a catalyst, and as the catalyst, antimony, germanium, tin, titanium, zinc, aluminum, which are generally used conventionally,
In addition to metal compounds such as magnesium, calcium, manganese, and cobalt, organic sulfonic acid compounds such as sulfosalicylic acid and o-sulfobenzoic anhydride are preferably used. The addition amount of the catalyst is the acid component 1 constituting the polyester.
1 × 10 ⁻⁵ to 1 × 10 ⁻² moles, preferably 5 ×
It is 10 ^{−5 to} 5 × 10 ⁻³ mol, optimally 1 × 10 ^{−4 to} 3 × 10 ⁻³ mol.

The SIP component, the potassium compound and the phosphorus compound are not added at the time of film formation, but are added at the time of producing the polyester polymer, and the addition timing is preferably in the initial stage of polymerization. A polymer containing the SIP component, the potassium compound and the phosphorus compound and a polymer not containing the SIP component may be blended during the film production.

The above-mentioned addition amount range is the content when formed into a film, and a master polymer having a large content of SIP component, potassium compound and phosphorus compound is polymerized in advance, and this polymer and a polymer not containing these additives are polymerized. Industrially, the method of blending the above-mentioned with the film is excellent.

[0026]

Although the reason why the polyester film of the present invention has good operability is not clear, conventionally used magnesium compounds, manganese compounds, calcium compounds, etc. all have a catalytic effect on the esterification reaction and polycondensation reaction of polyester. On the other hand, in some cases, it can be a catalyst for the thermal decomposition reaction of polyester, so that it is supplied to the extruder at the time of film production in the state of a polymer having a small number of terminal carboxyl groups, so it is decomposed while staying in the dead space. However, air bubbles are generated due to the decomposition gas of the polymer, and foreign substances are generated due to decomposition products, which significantly impairs operability.

The potassium compound such as potassium acetate added in the present invention functions as a decomposition catalyst for polyester.
Since it is much smaller than a magnesium compound or the like, it not only promotes the decomposition of the polymer but also has a great effect of reducing the specific resistance of the polymer, so that it may be added in a small amount to the polymer. Therefore, the heat resistance of the polyester is further increased. On the other hand, a sulfonate such as SIPG has a large effect of reducing the specific resistance because it is copolymerized with polyester.
Moreover, the heat resistance of the polyester is not deteriorated. Also, normally,
When the potassium compound is added to the polyester, internal particles are generated and the transparency of the film is lowered, but when used in combination with the SIP component, a polyester film excellent in transparency without generating internal particles can be obtained.

[0028]

The present invention will be described below with reference to Examples.
The present invention is not limited to this. In addition,
The characteristic values of polyester in the examples were measured as follows. Intrinsic viscosity [η] This is the value obtained from the solution viscosity measured at a temperature of 20.0 ° C using an equal weight mixture of phenol and ethane tetrachloride as a solvent. Diethylene glycol content (D%) Ethylene glycol and diethylene glycol were quantified by gas chromatography after alkaline hydrolysis of the polymer and determined as the number of moles (D%) of diethylene glycol relative to ethylene glycol. Color tone The color tone of the obtained polyester was evaluated by determining the b value using a color difference meter after molding into a granular form. The b value represents a yellow or bluish color tone (+ is yellowish, − is bluish). Unless the color tone of polyester is extremely small, the smaller the b value, the better. Film haze The obtained polymer was formed into a film having a thickness of 12 μm and measured with a Tokyo Denshoku haze meter. Heat resistance The obtained polymer was retained in a nitrogen atmosphere at 290 ° C. for 60 minutes and then discharged as a strand. The polymer was classified into the following three ranks based on the bubble generation state and the limiting viscosity retention rate, and rank 1 was evaluated as good. .. Rank 1: Generation of bubbles is small. The retention rate of the intrinsic viscosity is
98% or more. Rank 2: Generation of bubbles is moderate. The retention rate of the intrinsic viscosity is
95% or more and less than 98%. Rank 3: Many bubbles are generated. The retention rate of the intrinsic viscosity is 95
%Less than. Surface morphology The obtained polymer was formed into a film having a thickness of 12 microns, and its surface roughness was measured with a surface roughness meter manufactured by Kosaka Laboratory,
The following four ranks were classified, and rank A was rated as good. Rank A: Many irregularities of about 0.1 micron are seen. Rank B: Overall, it is close to rank A, but rough unevenness of about 0.3 micron can be seen here and there. Rank C: Although it is close to rank B as a whole, rough unevenness of about 0.5 micron can be seen here and there. Rank D: There are many irregularities exceeding 0.5 micron, and the surface is not uniform. Specific Resistance of Molten Polymer The specific resistance of the molten polymer was measured by the device shown in FIG. Polymer resistivity (R) is voltage (V), current (I)
Is read and is calculated by the following equation. R = V · S / I · l (where, 1 is the distance between electrodes (cm) and S is the surface area of the electrode (cm ² ).) This specific resistance was used as a measure of the goodness or badness of the castability by electrostatic application. Electrostatic application castability A voltage of 6 KV was applied between the die at the mouth of the extruder and the casting drum by means of an electrode placed on the top of the extruded film, and it was judged whether or not good film formation was possible at a casting speed of 43 m / min. .. 1 × specific resistance of molten polyester
When it was 10 ⁸ (Ω · cm) or less, the static electricity applied castability was generally good.

Reference Example 1 A slurry of terephthalic acid and ethylene glycol (molar ratio of ethylene glycol / terephthalic acid of 1.6) was continuously supplied to an esterification reaction apparatus in which bis (β-hydroxyethyl) terephthalate and / or its oligomer are present. The esterification reaction was carried out at 250 ° C. under atmospheric pressure for a residence time of 6 hours to continuously obtain an esterification product having an average degree of polymerization of 7.0. 100 parts by weight of this was transferred to a polymerization tank and heated to 280 ° C. to obtain 0.002 of silica having an average secondary particle size of about 2.5 μm.
In addition to 8 parts by weight, 25 × 10 ^-4 mol, 25 × 10 ^-4 mol, and 25 × 10 ^-4 mol of potassium acetate, SIPG, and PT-1 were added to 1 mol of all acid components constituting the polyester. , 2.0 × 10 ^-4 mol of antimony trioxide was added to 1 mol of the acid component as a catalyst, and pressure reduction was started to cause polycondensation reaction. As a result, [η] = 0.73 (dl / g), D% = 2.03 (Mol%) and b value = 11.5 were obtained.

Reference Example 2 A slurry of terephthalic acid and ethylene glycol (molar ratio of ethylene glycol / terephthalic acid of 1.6) was continuously fed to an esterification reactor in which bis (β-hydroxyethyl) terephthalate and / or its oligomer are present. The esterification reaction was carried out at 250 ° C. under atmospheric pressure for a residence time of 6 hours to continuously obtain an esterification product having an average degree of polymerization of 7.0. 100 parts by weight of this was transferred to a polymerization tank and heated to 280 ° C., and as a catalyst, antimony trioxide was added to 1 mol of the acid component.
2.0 × 10 ⁻⁴ mol was added, and pressure reduction was started to cause polycondensation reaction. As a result, polyester B having [η] = 0.69 (dl / g), D% = 1.58 (mol%) and b value = 4.5 was obtained. It was

Example 1 The polyester A obtained in Reference Example 1 and the polyester B obtained in Reference Example 2 were dried and then mixed in a weight ratio of A: B = 8: 92, and then mixed in a melt extruder. It was extruded into a sheet and formed into an unstretched film by the electrostatically applied casting method. After that, it is simultaneously biaxially stretched 3.3 times in the machine direction and 3.1 times in the transverse direction,
A stretched film having a thickness of 12 μ was obtained. The characteristics of this film are shown in Table 1, and are excellent in transparency and castability by electrostatic application,
It had a preferred surface morphology.

Examples 2 to 6 Stretched films were produced in the same manner as in Example 1 except that potassium acetate, SIPG and PT-1 were changed to the addition amounts shown in Table 1. The results of these stretched films are shown in Table 1.

Example 7 A slurry of terephthalic acid and ethylene glycol (molar ratio of ethylene glycol / terephthalic acid of 1.6) was continuously fed to an esterification reactor containing bis (β-hydroxyethyl) terephthalate and / or its oligomer. The esterification reaction was carried out at 250 ° C. under atmospheric pressure for a residence time of 6 hours to continuously obtain an esterification product having an average degree of polymerization of 7.0. 100 parts by weight of this was transferred to a polymerization tank and heated to 280 ° C. to obtain 0.002 of silica having an average secondary particle size of about 2.5 μm.
064 parts by weight of, relative to the total acid component to 1 mole of further constituting the polyester, potassium acetate, SIPG, respectively 2 × 10 ^-4 mol PT-1, 2 × 10 ^-4 mol, 2 × 10 ^-4 mol was added , 2.0 × 10 ^-4 mol of antimony trioxide was added to 1 mol of the acid component as a catalyst, and pressure reduction was started to cause polycondensation reaction. As a result, [η] = 0.69 (dl / g), D% = 1.60 (Mol%) and b value = 5.0 were obtained. After drying the obtained polyester, it was extruded into a sheet by a melt extruder and formed into an unstretched film by an electrostatically applied casting method. After that, it is simultaneously biaxially stretched 3.3 times in the machine direction and 3.1 times in the transverse direction,
A stretched film having a thickness of 12 μ was obtained. The characteristics of this film are shown in Table 1, and are excellent in transparency and castability by electrostatic application,
It had a preferred surface morphology.

Comparative Examples 1 to 5 Stretched films were produced in the same manner as in Example 1 except that potassium acetate, SIPG and PT-1 were changed to the compounds shown in Table 1 and the addition amounts. The results of these stretched films are shown in Table 1.

Examples 8 to 10 Stretched films were produced in the same manner as in Example 1 except that potassium acetate, SIPG and PT-1 were changed to the compounds shown in Table 1. The results of these stretched films are shown in Table 2.

Comparative Example 6 A stretched film was produced in the same manner as in Example 1 except that the compounds shown in Table 1 were used instead of potassium acetate, SIPG and PT-1. The results of these stretched films are shown in Table 2.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Figure 1]

[0040]

According to the present invention, a polyester film having excellent color tone, castability by electrostatic application and improved heat resistance was obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for measuring the specific resistance of a molten polymer. 1 is a DC high voltage generator, 2 is an electrometer, 3 is a high voltage voltmeter, 4 is a heating medium, 5 is a polymer to be measured, 6 is a cylindrical electrode, 7 is a grounded main body electrode, and 8 is an insulator. ..

[Chemical 1]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location B29K 67:00 B29L 7:00 4F C08L 67:02 (72) Inventor Junkichi Watanabe Uji City, Kyoto Prefecture Uji Hinojiri 31-3 Unitika Corporation Uji Plastic Factory

Claims (1)

[Claims] 1. A main component of terephthalic acid and ethylene glycol, a mole of potassium compound a × 10 ⁻⁴ mol, and a compound represented by the following structural formula b with respect to 1 mol of the total acid component.
× 10 ^-4 mol and phosphorus compound c × 10 ^-4 mol, the following formula ~
Polyester containing an amount that satisfies
A polyester film characterized by comprising a polyester of 0.5 or more. Embedded image (where M is Na, Li, NH ₄ , K, R ₁ and R ₂ are hydrogen, an alkyl group having 1 to 8 carbon atoms, and a phenyl group) 0.1 ≦ a ≦ 10 0.1 ≦ b ≦ 10 0.1 ≦ c≤10 2.0 ≤a + b ≤10 0.2 ≤a / b ≤4.0 0.15 ≤c / (a + b) ≤1.5