JPH04225056A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a polyester film, having homogeneous surfaces and excellent in thermal stability, runnability and transparency. CONSTITUTION:The objective polyester film is a film characterized by containing such silica particles, obtained from silica particles containing 1-30 silanol groups/nm<2> and having 0.1-5mum average particle diameter in an amount of 0.001-5wt.%. The silanol groups in an amount of >=30% based on the whole silanol groups are converted into calcium silanolate.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film containing silica particles obtained by a specific method and having excellent dispersibility, transparency and runnability.

0002

[Background Art and Problems to be Solved by the Invention] Polyester films, represented by polyethylene terephthalate, have excellent physical and chemical properties, and are used as base films for graphic arts, displays, packaging materials, and magnetic recording media. Widely used in fields such as capacitor derivatives.

However, when attempting to manufacture a film that takes full advantage of its transparency, the running of the film must be considered in terms of process passability in the manufacturing process, post-processing processes such as coating and vapor deposition, and handling of the product itself. However, this has not always been fully achieved in the past. This is often caused by friction and wear caused by high-speed contact between the film and the base material.

Conventionally, it has been known that in order to improve the running properties and abrasion resistance of a polyester film, the surface of the film can be appropriately roughened. In order to achieve this, a method has been adopted in which fine particles are present in the raw polyester, and some have been put into practical use.
It has not always been possible to satisfy these properties to a high degree.

For example, when so-called precipitated particles, which are generated from catalyst residues during polyester production, are used as fine particles, it is difficult to control the particle amount and particle size, and to prevent the formation of coarse particles. Since the fine particles are easily destroyed, running performance and wear resistance are poor, and furthermore, recycling is difficult. Another method called the addition method is when inert inorganic compound particles are added to polyester such as calcium carbonate, titanium dioxide, calcium phosphate, etc., the particles are not destroyed or deformed by stretching, and relatively steep protrusions are formed. However, since such particles have poor affinity with polyester, voids are created around the particles during stretching, resulting in a significant decrease in transparency and the particles being easily detached from the film surface. Phenomena such as the formation of white powdery substances occur.

One of the addition methods is a method using silica particles that have a relatively good affinity with polyester (for example, Japanese Patent Application Laid-Open No. 37-12150 and Japanese Patent Application Laid-Open No. 53-45369).
The method described in Publication No. 6) is known. however,
As described in JP-A No. 43-23960, silica particles have extremely poor dispersibility in polyester, so agglomeration occurs during the production of polyester, and when it is made into a film, many coarse particles appear on the surface of the film. The presence of protrusions reduces the transparency of the film. Furthermore, silica particles have the disadvantage that they reduce the polymerization rate during polyester production and the thermal stability of the resulting polymer. The reason for this is not clear, but it is thought to be due to the interaction between the silanol groups present on the surface of the silica particles and the metal compound that is the polymerization catalyst, for example, the metal compound is partially trapped.

[0007]

[Means for Solving the Problems] The present inventors have discovered that dispersibility,
As a result of extensive research in order to provide an excellent film that satisfies both running properties and transparency to a high degree and satisfies the various properties necessary for a film, we found that by using certain silica particles, we were able to achieve the above-mentioned properties. The inventors have discovered that the problem can be solved and have completed the present invention.

That is, the gist of the present invention is particles obtained from silica particles containing 1 to 30 silanol groups/nm 2 , wherein 30% or more of the total silanol groups are calcium silanolates. Diameter 0.1~5μm
The polyester film is characterized by containing 0.001 to 5% by weight of silica particles.

The present invention will be explained in more detail below. Polyester as used in the present invention refers to terephthalic acid, 2,6-
It refers to a polyester obtained using an aromatic dicarboxylic acid such as naphthalene dicarboxylic acid or its ester and ethylene glycol as main starting materials, but it may contain other third components. In this case, as the dicarboxylic acid component, for example, one of isophthalic acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, and sebacic acid can be used. Moreover, as the glycol component, one or more types of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. can be used. In any case, the polyester of the present invention refers to a polyester in which 80% or more of repeating structural units have ethylene terephthalate units or ethylene-2,6-naphthalate units.

[0010] The polyester film of the present invention refers to a polyester film that is at least uniaxially oriented and uses such a polyester as a starting material, and any known method can be used for its production. For example, after melt extruding into a sheet at 270 to 320°C,
After cooling and solidifying at 40 to 80°C to form an amorphous sheet, 8
At 0 to 130°C, it is sequentially biaxially stretched or simultaneously stretched at an area magnification of 4 to 20 times in the longitudinal and transverse directions to 160 to 2
A method of heat treatment at 50°C (for example, Japanese Patent Publication No. 30-5639)
(method described in the publication) can be used. When stretching in the longitudinal and transverse directions, stretching may be carried out in one stage each, or, if necessary, stretching may be carried out in multiple stages, or a heat treatment section for orientation relaxation may be provided between multi-stage stretching. Further, after biaxial stretching, the film may be stretched again before being subjected to the next heat treatment step. This re-stretching can be performed in either the longitudinal or lateral direction, or in both directions.

[0011] A feature of the present invention is that silica particles in which 30% or more of the total silanol groups are calcium silanolate, which are obtained from silica particles having a specific amount of silanol groups, are used as particles to be blended into the polyester film. be. The method for producing such particles is a so-called wet method, that is, a method using a medium mainly consisting of water. Decompose with mineral acid or carbon dioxide gas, etc. to synthesize particles whose main component is silica.

[0012] The silica particles obtained by this method are
Usually, the specific surface area (BET
It is a porous silica particle having a method (method) and can be preferably used because it has the ability to follow stretching in polyester, but the number of silanol groups is about 1 to 30/nm2, which is significantly higher than that in the gas phase method. If such particles are added during the polyester manufacturing process and a polymerization reaction is performed, the polymerization reaction will be delayed.

[0013] However, the present inventors have been able to improve these drawbacks by blocking more than a certain percentage of silanol groups with calcium, and also to improve the dispersibility of particles in polyester. I found out. That is, the number of silanol groups obtained by the above wet method is 1 to 30 pieces/nm2, preferably 5 to 15 pieces/nm2.
By employing a method such as ion-exchanging the silanol groups of particles/nm2 in an aqueous calcium chloride solution, the silanol groups can be converted into calcium silanolate. In this case, particles having a particle size and composition suitable for use in the present invention can be efficiently obtained. If the number of silanol groups in the silica particles to be converted into calcium silanolate is less than 1/nm2, the affinity with polyester will be poor, which is not preferable. Moreover, if it is 30 pieces/nm2 or more, the dispersibility in polyester will be poor, which is not preferable.

In the present invention, 3 out of all silanol groups
Silica particles containing 0% or more of calcium silanolate are used. If the calcium silanolate conversion rate is less than 30%, it is not preferable because the dispersibility and thermal stability of the particles in the polyester are poor. Calcium silanolate conversion rate is
Preferably it is 40% or more. The average particle size of the silica particles blended into the polyester film of the present invention is 0.1 to 5μ.
m, preferably in the range of 0.5 to 2 μm. If the average particle size is less than 0.1 μm, the running properties and abrasion resistance of the film will be insufficient, and if the average particle size exceeds 5 μm, the surface roughness of the film will become too large and the transparency of the film will deteriorate. This is not preferable as it may cause a decrease in

The amount of silica particles blended in the polyester film of the present invention is in the range of 0.001 to 5% by weight, preferably 0.01 to 1% by weight. The blending amount is 0.00
If it is less than 1% by weight, the running properties and abrasion resistance of the film will be insufficient. Moreover, if the blending amount exceeds 5% by weight, the surface roughness becomes too large, which is not preferable. In addition, the method of blending the silica particles used in the present invention into polyester, which is a raw material for film formation, is as follows:
There are no particular limitations, and any known method may be used. For example, the particles and polyester chips can be directly blended, but they can also be dispersed in ethylene glycol, which is a raw material for polyester, and prepared as an ethylene glycol slurry at any stage of the polyester manufacturing process, preferably after the esterification or transesterification reaction. , when adding at a stage before the start of the polycondensation reaction to perform the polycondensation reaction,
In particular, the effects of the present invention are maximized.

The dispersion slurry of silica particles used in the present invention can be prepared by a conventionally known method. For example, silica particles and ethylene glycol can be dispersed and adjusted using a high-speed stirrer having a plurality of shearing blades parallel to the rotating direction of the stirring blade, a homomixer, an ultrasonic disperser, or the like. Further, the dispersed slurry is preferably filtered with a filter of 1000 mesh or more in order to remove coarse particles and undispersed aggregated particles in the slurry. Further, if necessary, other particles such as kaolin, talc, calcium carbonate, aluminum oxide, crosslinked polymer particles, etc. can be used in combination as long as they do not impair the spirit of the present invention.

[0017]

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, the measurement methods and definitions of various physical properties and characteristics in the present invention are as follows. In Examples and Comparative Examples, "parts" indicate "parts by weight."

(1) Determination of silanol groups
After drying at 20°C under reduced pressure for 3 hours, it was reduced with lithium aluminum hydride in dioxane, the amount of hydrogen generated was measured by gas chromatography, and the number of silanol groups was calculated. The number of silanol groups was determined using the same method for the calcium silanolate particles. Note that the calcium silanolate conversion rate was calculated using the following formula.

[0019]

[Math 1]

(2) Calcium element content in silica particles Hydrofluoric acid was added to silica particles to dissolve them, excess hydrofluoric acid was removed by heating, and then a hydrochloric acid solution was added and quantified by atomic absorption spectrometry.

(3) Average particle size and particle size distribution The diameter (particle size) at an integrated volume fraction of 50% in the equivalent spherical distribution measured with a centrifugal sedimentation type particle size distribution analyzer (Model SA-CP3) manufactured by Shimadzu Corporation is defined as the average particle size. The diameter was taken as the diameter. (4) Intrinsic viscosity polymer 1
g was dissolved in 100 ml of a mixed solvent of phenol/tetrachloroethane = 50/50 (gravity ratio) and measured at 30.0°C.

(5) Heat stability Approximately 10 g of polymer was placed in a glass test tube with an internal capacity of 50 ml, and after drying at 160°C for 2 hours under high vacuum, the pressure was restored to 100 mmHg with nitrogen gas and the glass test tube was melted. After sealing,
Heat treatment was performed at 290°C for 2 hours, the intrinsic viscosity before and after the heat treatment was measured, and the intrinsic viscosity retention rate was determined from the following formula.

[0023]

[Math 2]

The intrinsic viscosity retention rate after heat treatment at 290°C for 2 hours was used as a measure of thermal stability.

(6) Running properties Two films cut out to a width of 15 mm and a length of 150 mm were stacked on a smooth glass plate, a rubber plate was placed on top of the films, and the contact pressure between the two films was set at 2 g/cm2. , 20
The frictional force was measured by sliding the films against each other at a rate of 5 mm/min, and the coefficient of friction at the point where the films were slid by 5 mm was determined as the coefficient of dynamic friction. The measurement was performed at a temperature of 23°C ± 1°C and a humidity of 50%.
The test was carried out in an atmosphere of ±5%.

(7) Wear characteristics Wear characteristics were evaluated based on the amount of white powder generated. The film was run for 1000 m while being in contact with a hard chrome fixing pin, and the amount of abrasion white powder adhering to the 6 mmφ hard chrome fixing pin was visually evaluated and divided into ranks as shown below. The film speed was 13 m/min, the tension was approximately 200 g, and the winding angle of the film around the pin was 135°.
And so. Rank A: Not adhered at all Rank B: A very small amount adhered Rank C: A small amount (more than rank B) adhered Rank D: Extremely large amount adhered (8) Number of coarse protrusions Accurately weigh 10 mg of sample and place it on a 18 x 18 mm cover. Place it in a glass and heat press at 280-290℃ to make it about 1 in diameter.
A 0 mm film was prepared, and this film was observed with a phase contrast microscope (100 times magnification), particles with a maximum length of 10 μm or more were measured, and the number of coarse protrusions was counted. (9) Transparency JI
Film haze was measured using a sphere-splitting turbidity meter NDH-20D manufactured by Nippon Denshoku Kogyo in accordance with S-K61714.

Example 1 (Preparation of slurry) Average particle size 0.85 μm, number of silanol groups 8.8/nm
When 120 parts of a 0.5% by weight aqueous calcium chloride solution was added to 10 parts of the silica particles prepared in Example 2, and the silanol groups on the particle surface were ion-exchanged with calcium ions while stirring, the conversion rate of calcium silanolate was 52.5%. The content was 5.5% by weight. After taking out the particles after treatment, 90 parts of ethylene glycol was added, and a homomixer (
10000r with Tokushu Kika Kogyo TK Homo Mixer)
pm - Dispersed for 60 minutes and filtered through a 1000 mesh wire mesh filter to obtain an ethylene glycol slurry.

(Manufacture of polyester) 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were heated to raise the temperature and methanol was distilled off to carry out a transesterification reaction, which was carried out for 4 hours from the start of the reaction. The temperature was raised to 230° C. over a period of time to substantially complete the transesterification reaction. Next, after adding 3 parts of the above slurry, 0.04 part of ethyl acid phosphate was added, and further 0.04 part of antimony trioxide was added to perform a polycondensation reaction, and after 4 hours and 30 minutes, the intrinsic viscosity was 0.660. of polyethylene terephthalate was obtained. After drying the obtained polyester, it was melt-extruded at 290°C to form an amorphous sheet, and then 3.
The film was stretched 5 times and 3.7 times in the transverse direction at 110° C., and heat treated at 210° C. for 3 seconds to obtain a film with a thickness of 15 μm, and its properties were evaluated.

Example 2 A polycondensation reaction was carried out in the same manner as in Example 1 except that silica particles having an average particle diameter of 1.25 μm and a number of silanol groups of 8.2/nm2 were used, and after 4 hours and 25 minutes. , polyethylene terephthalate having an intrinsic viscosity of 0.661 was obtained. Using the obtained polyester, a film was obtained in the same manner as in Example 1, and its properties were evaluated.

Example 3 Example 1 was repeated except that silica particles having an average particle diameter of 1.25 μm and a number of silanol groups of 8.2/nm2 were used, and 160 parts of a 0.5% by weight calcium chloride aqueous solution was used. When the polycondensation reaction was carried out in the same manner as above, it took 4 hours and 20
Polyethylene terephthalate with an intrinsic viscosity of 0.659 was obtained. Using the obtained polyester, a film was obtained in the same manner as in Example 1, and its properties were evaluated.

Comparative Example 1 The same procedure as in Example 1 was carried out except that silica particles having an average particle size of 0.85 μm and a number of silanol groups of 8.8/nm2 were used and were not subjected to ion exchange treatment with an aqueous calcium chloride solution. When the polycondensation reaction was carried out, the polymerization rate in the latter half of the reaction was slow, and it took 5 hours and 20 minutes to obtain polyethylene terephthalate with an intrinsic viscosity of 0.657. Using the obtained polyester, a film was obtained in the same manner as in Example 1, and its properties were evaluated.

Comparative Example 2 Average particle size 1.25 μm without ion exchange treatment with calcium chloride aqueous solution, number of silanol groups 8.2/nm
Polycondensation reaction was carried out in the same manner as in Example 1 except that silica particles No. 2 were used, but the polymerization rate in the latter half of the reaction was slow and it took 5 hours and 10 minutes to obtain polyethylene terephthalate with an intrinsic viscosity of 0.658. Using the obtained polyester, a film was obtained in the same manner as in Example 1, and its properties were evaluated.

Comparative Example 3 In Example 1, silica particles having an average particle size of 1.25 μm and a number of silanol groups of 8.2/nm2 were used, and a calcium chloride aqueous solution having a concentration of 0.1% by weight was prepared at 100% by weight.
silanolatization was carried out. Next, using the obtained particles, a polycondensation reaction was carried out in the same manner as in Example 1, and the polymerization rate in the latter half of the reaction was slow, and the intrinsic viscosity was 0.65.
It took 5 hours to obtain polyethylene terephthalate No. 7. Using the obtained polyester, a film was obtained in the same manner as in Example 1, and its properties were evaluated.

The results obtained above are summarized in Table 1 below.

[0035]

[Table 1]

As shown in Table 1, all the films of Examples 1 to 3, which are within the scope of the present invention, have excellent dispersibility, thermal stability, transparency, runnability, and abrasion resistance, and are suitable for use in, for example, graphic arts, While it is extremely useful as a base film for displays and packaging, when the silica particles are not converted to calcium silanolate or to a low degree as in Comparative Examples 1 to 3, the polymerizability is poor and the film The dispersibility, thermal stability, and transparency of particles in the film are poor.

[0037]

[Effects of the Invention] The film of the present invention has a uniform surface, excellent thermal stability, runnability, and transparency, and can be applied to various uses, and its industrial value is high.

Claims (1)

[Claims] [Claim 1] 1 to 30 silanol groups/nm2
Particles obtained from silica particles containing silica particles with an average particle size of 0.1 to 5 μm, in which 30% or more of the total silanol groups are calcium silanolate, are
A polyester film containing 1 to 5% by weight.