JPH0464328B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a thermoplastic resin composition containing a high concentration of a metal compound, which is blended into raw polyester to improve the thickness accuracy and productivity of polyester films. Regarding the manufacturing method. [Prior art] Biaxially oriented polyester films, especially polyethylene terephthalate, have excellent mechanical properties, electrical properties, chemical resistance, dimensional stability, etc., and are therefore used for magnetic tapes, capacitors, and packaging. It is used as a base material in many fields such as plate making, electrical cutting, and photographic film. Incidentally, in recent years, the requirements for film quality have become increasingly strict, and in the field of magnetic tapes, for example, reducing the long-term waviness of the base film, that is, improving the thickness accuracy, has become an indispensable condition. For this purpose, for example, as described in Japanese Patent Publication No. 37-6142, when a sheet-like material melted and extruded from an extrusion die is rapidly cooled in a rotating cooling drum, an electrostatic charge is applied to the surface of the sheet-like material. It is known that the so-called electrostatic cooling method, in which the cooling surface is brought into close contact with the cooling surface, is effective. However, in this electrostatic application cooling method, when the speed of the rotating cooling drum is increased for the purpose of increasing productivity, the adhesion between the sheet material and the cooling drum decreases, and so-called bound bubbles are generated. This is unacceptable as a quality characteristic required for the product. It is generally known that the higher the specific resistance of raw material polyester when it is melted, the more likely it is that these bound bubbles will occur. There is a method of adding and containing a metal compound during the production of polyester. However, according to the knowledge of the present inventors, when attempting to reduce the resistivity during melting using such a method, in order to ensure the effect, it is necessary to add a considerably large amount of metal compound during polyester production. However, in this case, the compound is exposed to high temperatures for a long time, which often promotes the formation of by-product diethylene glycol bonds, resulting in poor thermal stability. Additionally, polymerization time is often delayed and unwanted particles are formed in the polyester. In view of the above circumstances, the present inventors proposed an effective method for modifying polyester to which the electrostatic cooling method cannot be effectively applied, in Japanese Patent Application Laid-Open No. 18534/1983. The method proposed in this application is a method in which 0.01 to 1% by weight of a metal salt of an aliphatic monocarboxylic acid or an aliphatic dicarboxylic acid is added to the polyester in a step before melt extrusion when producing a polyester film. If such a method is adopted, the thickness accuracy of the film can be improved to a preferable degree using the electrostatic cooling method without impairing heat resistance, transparency, and color tone. [Problems to be Solved by the Invention] By the way, when blending such a metal compound into polyester, in order to improve the uniformity of the blend and the operability, it is necessary to avoid directly blending the metal compound with polyester and to prepare it in advance at a high concentration. Preferably, a method is used in which a thermoplastic resin composition containing a so-called master chip is produced, and the chip is blended with a polyester chip. However, other difficulties are often encountered when attempting to employ such master chip methods. This is because these metal compounds act aggressively on the base thermoplastic resin, such as polyester, especially in the molten state, often leading to a decrease in the molecular weight of the thermoplastic resin, an increase in coloration, and even the formation of insoluble foreign substances. However, this tendency is particularly noticeable at the stage of master chip production, that is, in a state where a high concentration of metal compounds is contained, and in extreme cases, it becomes difficult to form chips. [Means for Solving the Problems] As a result of the inventors' efforts to improve these drawbacks, it has been found that these drawbacks can be overcome if the master chip is manufactured under conditions in which the metal compound is not completely melted. The present invention was completed based on the discovery that it is possible to solve this problem and to stably obtain high-quality master chips. That is, the present invention, when producing a master chip for blending a polyester film containing a metal compound with a melting point of 120 to 290°C, involves melting and molding the metal compound under conditions that do not at least completely melt the metal compound. The present invention relates to a method for producing a master chip, characterized in that it contains a compound in an amount of 0.1 to 30% by weight. The present invention will be explained in more detail below. Polyester as used in the present invention is obtained by using terephthalic acid or its ester-forming derivatives, such as dimethyl terephthalate and ethylene glycol, as main starting materials, performing an esterification or transesterification reaction, and then performing a polycondensation reaction. Although it refers to polyester, a part of it may be replaced with another third component. For example, part of the acid component may be replaced with isophthalic acid, naphthalene dicarboxylic acid, p-hydroxybenzoic acid, adipic acid, sebacic acid, or lower alkyl esters thereof, and part of the glycol component may be replaced with trimethylene glycol, It may be replaced with hexamethylene glycol or the like. In any case, what is polyester as used in the present invention?
It refers to a polyester in which 80 mol% or more, preferably 90 mol% or more, of ethylene terephthalate units. Since polyester is usually formed into a film at a temperature of about 290°C, in the present invention, the melting point of the metal compound finally blended and contained in the polyester must be 290°C or lower and 120°C or higher. If the melting point of the metal compound exceeds 290° C., it will not melt at all or will not melt sufficiently during the melt extrusion process, so that the original purpose of improving the electrical conductivity of polyester will not be fully achieved. On the other hand, if the melting point is too low, the difference from the film-forming temperature is too large, which tends to cause decomposition or deterioration, which will have an adverse effect on the film. Examples of metal compounds that meet these requirements and are suitable for use in the present invention include metal salts of aliphatic monocarboxylic acids or dicarboxylic acids having about 4 to 30 carbon atoms, especially lithium salts, sodium salts, potassium salts, magnesium salts, etc. Examples include one or more compounds selected from salts, manganese salts, zinc salts, calcium salts, aluminum salts, and the like. In particular, the effects of the present invention are effectively exhibited in the case of magnesium salts, manganese salts, zinc salts, and calcium salts. Examples of more specific metal compounds include magnesium palmitate, manganese palmitate, zinc palmitate, magnesium stearate, zinc stearate, potassium oleate, sodium oleate, magnesium oleate, zinc oleate, and magnesium sebacate. , manganese sebacate, etc., but are not limited to these, of course. A feature of the present invention is that when producing a master chip containing a high concentration of such a metal compound, the master chip is melt-molded under conditions such that the metal compound is at least completely melted. In other words, it is preferable to manufacture the master chip at a molding temperature lower than the melting point of the metal compound to be contained. In this case, the thermoplastic resin serving as the matrix is determined by the combination with the melting point of the metal compound contained therein, and of course one having a softening temperature lower than the melting point of the metal compound is selected. Examples of thermoplastic resins that can be used in the present invention include polyester, polyamide, polycarbonate, polystyrene, polyethylene, polypropylene, and polybutylene, which have a softening temperature of less than 290°C. Among these, polyester resins are selected from isophthalic acid, naphthalene dicarboxylic acid, adipic acid, sebacic acid, diethylene glycol, trimethylene glycol, tetramethylene glycol, etc. because of their good compatibility after blending with master chips. Copolymerized polyethylene terephthalate containing one or more copolymer components or polybutylene terephthalate containing or not containing a copolymer component is preferably used. In order to embody the technical idea of the present invention, it is preferable to select a temperature between the melting point of the metal compound and the softening point of the thermoplastic resin as the molding temperature of the master chip, but in practice this is not necessarily the case. Not done. This is because, depending on conditions such as the type and scale of the molding machine, operating conditions, or the content of the metal compound, it is often the case that even if the resin temperature deviates from this range, only a portion of the metal compound will melt and it will not be practical. This is because molding may be possible without any problems. In any case, the feature of the present invention is that molding is performed under conditions that do not at least completely melt the metal compound to be contained, and as long as the purpose is not impaired, there is no restriction on the molding temperature etc. . The concentration of the metal compound in the master chip thus obtained is preferably 0.1 to 30% by weight, preferably 1 to 15% by weight, and more preferably 2 to 10% by weight. If this value is less than 0.1% by weight, a large amount of masterbatch must be blended to lower the resistivity during melting of the polyester, which reduces its significance and also reduces the surface roughness, slipperiness, etc. of the resulting film. Characteristics change significantly,
On the other hand, if this value exceeds 30% by weight, even with the method of the present invention, molding is often difficult and the amount blended is too small, which tends to result in non-uniform dispersion. The amount of metal compound in the polyester composition used for film formation after blending with the master chip is 0.005 to 3 parts by weight, preferably 0.01 to 1 part by weight, from the viewpoint of the effect during electrostatic application cooling, molecular weight reduction of the film, thermal stability, etc.
The amount is preferably 0.02 to 0.2% by weight, more preferably 0.02 to 0.2% by weight. In the present invention, after the amorphous sheet-like material is formed using the electrostatic cooling method, a normal stretching process can be used. That is, methods such as sequential biaxial stretching or simultaneous biaxial stretching in the longitudinal and transverse directions and heat treatment at 160 DEG C. to 240 DEG C. can be used (for example, the method described in Japanese Patent Publication No. 30-5639). [Effects of the Invention] As detailed above, according to the present invention, by adopting molding conditions that take advantage of the below melting point of the metal compound and thermoplastic resin, the electrostatic application cooling method can be effectively applied. Master chips containing a large amount of metal compounds for application can be stably obtained and have great utility value. [Examples] The present invention will be explained in more detail below based on Examples and Comparative Examples. In the examples and comparative examples, "parts" indicate "parts by weight." The measurement method used is shown below. (1) Measurement of specific viscosity 1 g of polymer or film is mixed with phenol/
It was dissolved in 100 ml of tetrachloroethane (50/50 weight ratio) and measured at 30.0°C. (2) Color Tone The b value, which is an index of the yellowness of the polymer or film, was measured using a photoelectric color difference meter (TC-5D type) manufactured by Tokyo Denshoku. The larger the b value, the stronger the yellowish tinge. (3) Specific resistance during melting According to the method described in JP-A-57-190040. That is, after melting polyester at 285° C., a DC voltage of 3 KV is applied, and the specific resistance immediately after application is taken as the specific resistance at the time of melting. Example 1 After uniformly mixing 2 parts of manganese sebacate, which has a melting point of 259°C when measured with a differential calorimeter, and 98 parts of polyethylene terephthalate copolymerized with 10 mol% isophthalic acid and a melting point of 242°C, Kobe Steel, Ltd. Co., Ltd. vertical plastic extruder (KOBE-TEC, VE-125
-20 type) was used to produce a masterbatch. At this time, the set temperature of the cylinder is 250℃, and 10
It was extruded into strands at a rate of Kg/hour and then pelletized, and the pellets could be molded without any problems. The master chips were cloudy, indicating that the manganese sebacate was not completely melted. Also, its specific viscosity is 1.71 and b value is 2.7
Both values were satisfactory. These results are shown in Table 1 along with other Examples and Comparative Examples. Next, to confirm the effect of the master chip,
The sheet was formed into a film using the electrostatic cooling method. That is, after an esterification reaction using terephthalic acid and ethylene glycol as starting materials,
Polyethylene terephthalate with a specific viscosity of 1.78 and a specific resistance when melted of 9×10 ⁸ Ω-cm obtained by adding 0.03 part of antimony trioxide and 0.01 part of phosphoric acid.
2 parts of the masterbatch was mixed with 100 parts to obtain a polyester composition for film formation. The specific resistance of this composition when melted was 5×10 ⁷ Ω-cm, which was sufficiently low. Next, the composition was extruded into a sheet from an extruder at 290° C. and an amorphous sheet was formed using an electrostatic cooling method. The conditions for applying static electricity at this time are as follows. That is, a tungsten wire with a diameter of 0.1 mm was used as a positive electrode, and this wire was stretched on the upper surface of a rotating cooling drum in a direction perpendicular to the flow of the sheet, and a DC voltage of about 10 KV was applied to it. After obtaining the amorphous sheet, it was stretched 3.0 times in the longitudinal direction and 3.5 times in the transverse direction, and the extrusion rate and roughness of the rotary cooling body were adjusted so that a biaxially stretched film with a thickness of 15 μm was always obtained. The relationship between the speed of the rotary cooling body and the bound bubbles was observed. The speed of the rotating cooling body
Although the speed was gradually increased from 20 m/min, no bound bubbles were generated even at 40 m/min, and the biaxially stretched film obtained at this time had small unevenness in thickness and was sufficiently satisfactory. The biaxially stretched film had a specific viscosity of 1.70 and a b value of 2.7, which were at a level that caused no practical problems. Comparative Example 1 A polyester film having a thickness of 15 μm was obtained in exactly the same manner as in Example 1, except that polyester without master chips was used as the polyester raw material for film formation. When the rotating cooling body speed reached 31 m/min, trapped bubbles were observed, but the speed was further increased to 40 m/min.
The polyester film obtained at this time had polka dot-like defects on the surface and had a large thickness unevenness, making it unsuitable for practical use. Examples 2 and 3 and Comparative Examples 2 and 3 Master chips were manufactured in the same manner as in Example 1, except that the master chip manufacturing conditions were changed as shown in Table 1. When the method of the present invention is adopted, it is possible to smoothly obtain a high-quality masterbatch, and as a result, an excellent polyester film can be obtained with good productivity. When this method is adopted, it is difficult to manufacture the masterbatch itself, and the molecular weight decreases and the b value increases significantly, and even when the masterbatch is blended to obtain a polyester film, breakage often occurs, making smooth operation difficult. 【table】

Claims (1)

[Claims] 1. When producing a master chip containing a metal compound, the metal compound has a melting point of 120 to 290°C,
is a metal salt of an aliphatic monocarboxylic acid or dicarboxylic acid, and the thermoplastic resin composition serving as the matrix has a softening temperature lower than the melting point of the metal compound,
The metal compound is melt-molded under conditions that do not melt at least completely, and the metal compound is
A method for producing a master chip to be blended into a raw material polyester used for producing a polyester film by an electrostatic cooling method, the content being 30% by weight.