JPH04298538A - Polyester film - Google Patents

Abstract

PURPOSE:To provide a polyester film having a uniform surface and excellent heat stability, running properties and transparency. CONSTITUTION:A polyester film containing 0.001-5wt.% silica particles obtained from silica particles which have 1-30 silanol groups per nm<2> and a mean particle diameter of 0.1-5mum and in which 30-70% of the silanol groups are blocked with a silane coupling agent.

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 trying to manufacture a film that takes full advantage of its transparency, the film has to be carefully processed in terms of passability in the manufacturing process, post-processing processes such as coating and vapor deposition, and handling of the product itself. Drivability is particularly required, but 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/nm2, in which 30 to 70% of the total silanol groups are blocked by treatment with a silane coupling agent. The average particle size is 0.
．． A polyester film characterized by containing 0.001 to 5% by weight of silica particles of 1 to 5 μm.

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, the dicarboxylic acid component includes, for example, isophthalic acid, terephthalic acid,
One of 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.

The feature of the present invention is that the particles blended into the polyester film are obtained from silica particles having a specific amount of silanol groups, 30 to 70% of the total silanol groups.
The point is that silica particles blocked by a silane coupling agent are used. As a method for producing such particles, a so-called wet method, that is, a method using a medium mainly composed of water, can be used. For example, calcium silicate is first produced by reacting sodium silicate with calcium salts such as calcium hydroxide. After that, it is decomposed with mineral acid or carbon dioxide gas, etc., and particles containing silica as a main component are synthesized.

[0012] The silica particles obtained by this method are
Usually, the specific surface area (BE
It is a porous silica particle having a method (T 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 of 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.

However, the present inventors have been able to improve this drawback by sealing more than a certain percentage of silanol groups by treatment with a silane coupling agent, and also improve the dispersibility of particles in polyester. We also found that it can be improved. The silane coupling agent used in the present invention usually has the chemical formula YRSiX3 (
Y is an organic functional group such as a vinyl group, methacrylic group, epoxy group, or amino group, R is an alkyl group, Si is silicon, and X is a hydrolyzable group such as a chloro group, an alkoxy group, or an acetoxy group). Examples include vinyltriethoxysilane, vinyltrichlorosilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc. It is not limited to.

[0014] In the treatment with a silane coupling agent, 0.1 to 10% by weight of the silane coupling agent is generally dispersed in water or alcohol, and if necessary, the mixture is heated and stirred. By this, the silanol groups of the silica particles can be blocked. In the present invention, 30 to 70% of the total silanol groups, preferably 4
Silica particles with 0 to 60% blocked by a silane coupling agent are used. If the blocking rate is less than 30%, the dispersibility and thermal stability of the particles in the polyester will be poor, which is not preferable. When the blocking rate exceeds 70%, silica particles and ethylene glycol are not compatible with each other, making it difficult to blend them into polyester as an ethylene glycol slurry.

The number of silanol groups on the surface of the silica particles before silanolization is 1 to 30/nm2, preferably 5.
It is in the range of ~15 pieces/nm2. The number of silanol groups is 1
If the number is less than 2 silanol groups/nm2, it will not be dispersed in water or alcohol, resulting in inconvenience when blocking silanol groups. Furthermore, if the number of silanol groups exceeds 30/nm2, the dispersibility in water or alcohol will deteriorate.

[0016] The average particle diameter of the silica particles blended into the polyester film of the present invention is 0.1 to 5 μm, preferably 0.1 to 5 μm.
．． It is in the range of 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.

[0019] If necessary, other particles such as kaolin, talc, calcium carbonate, aluminum oxide, or crosslinked polymer particles may be used in combination as long as they do not impair the spirit of the present invention. .

[0020]

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: 1
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 silanol blocking rate was calculated using the following formula.

[0022]

[Math 1]

(2) 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.

(3) 1 g of limiting viscosity polymer is mixed with phenol/tetrachloroethane = 50
/50 (weight ratio) dissolved in 100 ml of mixed solvent, 3
Measured at 0.0°C.

(4) 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.

[0026]

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

(5) 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, and 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 measurements were performed at a temperature of 23°C ± 1°C and a humidity of 50% ±
The test was carried out in a 5% atmosphere.

(6) 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 attached at all Rank B: A small amount attached Rank C: A small amount (more than rank B) attached Rank D: Extremely large amount attached

(7) Number of coarse protrusions Weigh accurately 10 mg of the sample, sandwich it between 18 x 18 mm cover glasses, and heat press at 280-290°C to form a sample with a diameter of about 1
A 0 mm film was prepared, and this film was observed with a phase contrast microscope (100 times magnification), and the number of coarse protrusions with a maximum length of 10 μm or more was counted.

(8) Transparency Film haze was measured according to JIS-K61714 using a sphere-splitting turbidity meter NDH-20D manufactured by Nippon Denshoku Industries.

Example 1 [Preparation of slurry] 100 parts of water was added to 10 parts of silica particles having an average particle size of 0.80 μm and a number of silanol groups of 8.0/nm2.
1 part and 0.05 part of a silane coupling agent vinyltriethoxysilane were added and stirred at 60°C for 1 hour to block the silanol groups of the particles (the blocking rate of silanol groups was 54.5%). The particles were then separated by filtration and dried to obtain a powder.

[0032] 90 parts of ethylene glycol was added to 10 parts of the particle powder obtained as described above, and the mixture was heated at 10,000 rpm-6 using a homomixer (manufactured by Tokushu Kika Kogyo, TK Homomixer).
The mixture was dispersed for 0 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 parts of magnesium acetate tetrahydrate are placed in a reactor, heated to raise the temperature, and methanol is distilled off to carry out transesterification reaction to start the reaction. The temperature was raised to 230° C. in 4 hours, and the transesterification reaction was substantially completed. Next, after adding 3 parts of the above slurry, 0.0 parts of ethyl acid phosphate was added.
When 0.04 part of antimony trioxide was added to carry out a polycondensation reaction, polyethylene terephthalate having an intrinsic viscosity of 0.660 was obtained in 4 hours and 10 minutes.

After drying, the obtained polyester was melt-extruded at 290°C to form an amorphous sheet, which was then stretched 3.5 times in the machine direction at 90°C and 3.7 times in the transverse direction at 110°C, and then stretched at 21°C.
Heat treatment was performed for 3 seconds to obtain a film with a thickness of 15 μm.
Its characteristics were evaluated. The results showed that the polymerizability, thermal stability, etc. were good, and the film properties were also very good.

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, an initial number of silanol groups of 8.0/nm2, and a blocking rate of silanol groups of 57.0% were used. After 4 hours and 5 minutes, polyethylene terephthalate with an intrinsic viscosity of 0.662 was obtained. Further, a film was obtained in the same manner as in Example 1, and its properties were evaluated.

Example 3 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, an initial number of silanol groups of 7.0/nm2, and a blocking rate of silanol groups of 65.0% were used. After 4 hours and 2 minutes, polyethylene terephthalate with an intrinsic viscosity of 0.665 was obtained. Further, a film was obtained in the same manner as in Example 1, and its properties were evaluated.

Comparative Example 1 A polycondensation reaction was carried out in the same manner as in Example 1, except that silica particles with an average particle size of 0.80 μm, an initial number of silanol groups of 7.0/nm2, and a blocking rate of silanol groups of 0% were used. After 5 hours and 30 minutes, polyethylene terephthalate with an intrinsic viscosity of 0.651 was obtained. Further, a film was obtained in the same manner as in Example 1, and its properties were evaluated. Polyethylene terephthalate had poor polymerizability, thermal stability, etc., and the resulting film had many coarse protrusions and poor transparency.

Comparative Example 2 A polycondensation reaction was carried out in the same manner as in Example 1, except that silica particles with an average particle diameter of 1.25 μm, an initial number of silanol groups of 8.0/nm2, and a blocking rate of silanol groups of 15% were used. After 5 hours and 5 minutes, polyethylene terephthalate with an intrinsic viscosity of 0.650 was obtained. Further, a film was obtained in the same manner as in Example 1, and its properties were evaluated. Polyethylene terephthalate had poor polymerizability, thermal stability, etc., and the resulting film had many coarse protrusions and poor transparency.

Comparative Example 3 A polycondensation reaction was carried out in the same manner as in Example 1, except that silica particles with an average particle size of 1.25 μm, an initial number of silanol groups of 8.0/nm2, and a blocking rate of silanol groups of 85% were used. After 4 hours and 5 minutes, polyethylene terephthalate with an intrinsic viscosity of 0.665 was obtained.

A film was also obtained in the same manner as in Example 1, and its properties were evaluated. Polyethylene terephthalate had good polymerizability, thermal stability, etc., but it was difficult to make the particles into an ethylene glycol slurry, and the presence of coarse particles in the slurry resulted in a film with many coarse protrusions and poor transparency. It was also bad. The results obtained above are summarized in Table 1 below.

[0041]

[Table 1]

[0042]

[Effect of the invention] The film of the present invention has a uniform surface,
It has excellent thermal stability, runnability, and transparency, and can be applied to a variety of 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 to 70% of the total silanol groups are blocked by treatment with a silane coupling agent, are A polyester film characterized by containing % by weight.