JPH0314051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved process for producing polyester to make polyester films or fibers. More specifically, the present invention relates to a method for producing linear polyester that improves the affinity of fine particles containing calcium carbonate as a main component with polyester, thereby producing films or fibers with excellent transparency and abrasion resistance. BACKGROUND OF THE INVENTION Polyester in general, and polyethylene terephthalate in particular, has excellent mechanical and chemical properties and is therefore widely used in films, fibers, and the like.
However, when producing films or fibers that take full advantage of their transparency and glitter,
In the molding and processing steps, process defects often occur. This is often due to a high coefficient of friction. Conventionally, many methods have been proposed to reduce the friction coefficient of polyester, including the presence of fine particles in polyester, but the affinity between the fine particles and polyester is insufficient, and the transparency and abrasion of films and fibers are Neither gender was satisfactory. Conventional methods for improving the surface properties of polyester include: Precipitating part or all of the catalyst used during polyester synthesis during the reaction process (internal particle precipitation method) Precipitating fine particles of calcium carbonate, silicon oxide, etc. during polymerization or polymerization Many methods have been proposed in which the particles are added later (external particle addition method). However, in the internal particle precipitation method, since the particles are metal salts of polyester components, the affinity with polyester is good to some extent, but on the other hand,
Since this method generates particles during the reaction, it is difficult to control the amount and diameter of particles and prevent the generation of coarse particles. In one method, if the particle size, amount added, etc. are appropriately selected, and fine particles from which coarse particles are removed by classification or the like are added, excellent slipperiness can be obtained. However, since the affinity between the inorganic particles and the organic component polyester is not sufficient, peeling occurs at the interface between the particles and the polyester during stretching, etc., and voids are generated. Therefore, there are problems to be solved in terms of transparency and abrasion resistance. To improve the affinity between inorganic particles and polyester, surface treatment using a coupling reaction between silane compounds or titanate compounds and inorganic particles has been proposed, but the treatment process is complicated and the effects are not as expected. Various problems arose. Purpose of the Invention In view of the above-mentioned circumstances, the present inventors made intensive studies on polyester suitable for producing films and fibers with excellent slipperiness, transparency, and abrasion resistance by including fine particles in the polymer. As a result, the film obtained by crushing calcium carbonate in the presence of a specific compound,
It was discovered that the fiber has good properties, and the present invention was achieved. Structure of the Invention The present invention provides a method for polymerizing linear polyester by crushing calcium carbonate in the presence of at least one polyvalent carboxylate selected from the group consisting of alkali metal salts and ammonium salts of polyvalent carboxylic acids. This is a method for producing polyester with excellent particle affinity, which is characterized in that it is added at any stage until completion. The unique feature of the method of the present invention is that calcium carbonate is subjected to crushing treatment in the presence of a specific compound. Although the reason for this is not clear, the interaction between the two improves the affinity of calcium carbonate with polyester, giving it excellent transparency and abrasion resistance. The polyester used in the present invention may be any material as long as it can be formed into fibers or films, such as polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-
Examples include p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, and polyethylene-2,6-naphthalene dicarboxylate. Of course, these polyesters may be homopolyesters or copolyesters, and examples of copolymer components include diethylene glycol, neopentyl glycol,
Diol components such as polyalkylene glycol, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, and 5-sodium sulfoisophthalic acid; polymer maintains substantially linear shape Examples include polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid in a range of amounts. Calcium carbonate in the present invention includes natural products and synthetic products, and crystal types of calcium carbonate include calcite, aragonite, and vaterite, and any of these may be used. Calcium carbonate contains one or more of (1) pure calcium carbonate, (2) magnesium oxide, silicon oxide, calcium hydroxide, and other compounds, and has a calcium carbonate content of 50% or more. In the present invention, the polycarboxylic acid salt is selected from the group consisting of alkali metal salts and ammonium salts of polycarboxylic acids. Examples of the polycarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, adipic acid, and acrylic acid polymers (molecular weight:
2000-7000), maleic anhydride copolymer (molecular weight: 2000-7000), and the like. Specific examples of polyvalent carboxylates include disodium terephthalate, disodium adipate, sodium polyacrylate (salt ratio: approximately 100%), and ammonium polyacrylate (salt ratio: approximately 100%).
%), polyisobutylene sodium maleate (salt ratio: approximately 100%), and the like. One or more types of these can be used. In the present invention, methods for crushing calcium carbonate in coexistence with polyvalent carboxylates include (1) a method of adding polyvalent carboxylates to calcium carbonate powder and crushing it (dry crushing method) ( 2) A method is used in which calcium carbonate and polycarboxylic acid salts are added to a dispersion medium such as ethylene glycol, water, or ethanol, and the resulting slurry is crushed after mixing (wet crushing method). The concentration of calcium carbonate in the slurry in the wet crushing method is preferably 1 to 60% by weight, more preferably 5 to 20% by weight. The mixing ratio of calcium carbonate and polyvalent carboxylate is preferably 0.1 to 30 parts by weight per 100 parts by weight of calcium carbonate, in order to improve the affinity of calcium carbonate for polyester. More preferably, it is used in a range of 0.5 to 20 parts by weight. The average particle size of calcium carbonate after crushing is preferably 5μ or less, more preferably 2μ or less.
Here, the average particle size is 50% by weight of all particles measured.
means the "equivalent spherical diameter" of the particle at the point.
"Equivalent spherical diameter" means the diameter of an imaginary sphere having the same volume as the particle, and can be calculated from electron micrographs of the particle or measurements by conventional sedimentation methods. Regarding the particle size distribution of calcium carbonate having an average particle size of 5 μm or less, it is preferable that it contains almost no coarse particles of about 10 μm or more and has a sharp distribution on the fine side. For this reason, methods such as performing a classification process before or after the crushing process are used. The addition of calcium carbonate after crushing in the presence of the polyvalent carboxylate may be carried out before the completion of polymerization of the polyester, and may be carried out at any time and by any method. The amount of calcium carbonate added to the polyester is preferably 0.01 to 5.0% by weight, more preferably 0.03 to 3% by weight. The polyester produced by the method of the present invention is effective in the fields of fiber, film, and other molding, but is particularly preferably used in the fields of microfilm, vapor-deposited film, and magnetic tape, which require transparency and abrasion resistance. Can be done. Examples Examples will be given below to specifically explain the invention. Note that "parts" in the examples mean parts by weight. Further, each characteristic value in the Examples was measured according to the following method. (1) Affinity between calcium carbonate and polyester The surface polymer of the film was removed by etching to expose calcium carbonate, and then observed under a scanning electron microscope at a magnification of 20,000 times. The affinity is expressed by the following judgment based on the ratio of the diameter of calcium carbonate (Dc) and the diameter of the void (Db). Grade 1: 1≦Db/Dc<1.5 (i.e., voids do not exist or are very small) Grade 2: 1.5≦Db/Dc<3.0 Grade 3: 3.0≦Db/Dc<4.0 (2) Film haze ASTM D1003− According to the method shown in 59T,
Measurements were made using a direct reading haze meter. (3) Abrasion evaluation The film side of a 1/2 inch wide magnetic tape was brought into contact with a 5 mmφ stainless steel SUS fixing pin (surface roughness 0.58) at an angle n-π (radian), and the film was rotated at a speed of 2 m/min. Move it back and forth for about 15cm and rub it (at this time, the tension _T1 on the entry side was 40g). After repeating this operation and measuring 20 times, visually judge the degree of scratches that have occurred on the scratched surface. At this time, it is judged in three stages: ○ if there are almost no or only a few scratches, × if many scratches occur on the entire surface, and △ if there are many scratches. Example 1 15 parts of calcium carbonate (average particle size 2.5μ) and 2 parts of sodium polyacrylate (molecular weight 6000, proportion of sodium salt 100%) were added to 85 parts of ethylene glycol (hereinafter abbreviated as EG), and mixed and stirred. After that, crushing was performed using a sand grinder (manufactured by Igarashi Kikai Seizo Co., Ltd., glass beads were used as the media) to obtain a calcium carbonate-treated product with an average particle size of 0.6 μm. Furthermore, 100 parts of dimethyl terephthalate and 70 parts of EG were transesterified in a conventional manner using 0.035 parts of manganese acetate tetrahydrate as a catalyst, and then 3.4 parts of the EG slurry of calcium carbonate obtained above was transesterified (calcium carbonate concentration: 0.5% by weight). to the polymer) was added under stirring. Thereafter, a polycondensation reaction was carried out in a conventional manner under high temperature vacuum to obtain polyethylene terephthalate with an intrinsic viscosity of 0.620. Furthermore, after drying the obtained polyester at 180℃,
It was made into a sheet using an extruder, then biaxially stretched at 90°C with a longitudinal stretch ratio of 3.5 times and a transverse stretch ratio of 4.0 times.
It was heat-set at 200°C to form a film with a thickness of 15μ. The properties of this film are shown in Table 1. In the obtained film, there were mainly no voids around calcium carbonate, and even if there were any voids, they were extremely small. The film also had good transparency and abrasion resistance. Example 2 A film with a thickness of 15 μm was obtained in the same manner as in Example 1 except that disodium terephthalate was used as the polyvalent carboxylate. Table 1 shows the physical properties of the obtained film. Example 3 Example 1 except that ammonium polyacrylate (molecular weight 6000, ammonium salt ratio 100%) was used as the polycarboxylic acid salt in Example-1.
A film with a thickness of 15 μm was obtained in exactly the same manner as above.
Table 1 shows the physical properties of the obtained film. Comparative Example 1 A film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that sodium polyacrylate was added to the slurry after crushing. The properties of this film are shown in Table 1. The voids around calcium carbonate in the obtained film were large, and the film had poor transparency and abrasion resistance. Comparative Example 2 The thickness was determined in the same manner as in Example 1 except that sodium polyacrylate was not used in Example 1.
A 15μ film was obtained. The characteristics of this film are shown below.
Shown in 1. The obtained film was inferior as in Comparative Example 1. Comparative Example 3 A film was obtained in the same manner as in Example 1 except that kaolin was used instead of calcium carbonate.
The properties of this film are shown in Table 1. The voids around the kaolin in the film were large, and the film had poor transparency and abrasion resistance. Comparative Example 4 A film was obtained in the same manner as in Example 1 except that sodium hydroxide was used instead of sodium polyacrylate. The properties of this film are shown in Table 1. The voids around the calcium carbonate in the film were large, and the film had poor transparency and abrasion resistance. Comparative Example 5 A film was obtained in the same manner as Comparative Example 4 except that the amount of sodium hydroxide was changed from 2 parts to 0.75 parts. The properties of this film are shown in Table 1. Comparative Example 6 A film was obtained in the same manner as Comparative Example 4 except that kaolin was used instead of calcium carbonate. The properties of this film are shown in Table 1. The voids around the kaolin in the film were large, and the film had poor transparency and abrasion resistance. Comparative Example 7 A film was obtained in the same manner as Comparative Example 6 except that the amount of sodium hydroxide was changed from 2 parts to 0.75 parts. The properties of this film are shown in Table 1. Comparative Example 8 15 parts of calcium aluminum silicate and 0.08 parts of sodium acetate (0.05% by weight based on the powder) were added to 85 parts of ethylene glycol (EG), mixed and stirred, and then dispersed in a colloid mill. A film was obtained by synthesizing polyester and forming a film in the same manner as in Example 1, except that the obtained slurry was added to the polyester reaction system in place of the EG slurry of calcium carbonate in Example 1. The properties of this film are shown in Table 1. This film had large voids around the calcium aluminum silicate and had poor abrasion resistance. 【table】

Claims (1)

[Scope of Claims] 1 Calcium carbonate that has been crushed in the presence of at least one polyvalent carboxylate selected from the group consisting of alkali metal salts and ammonium salts of polyvalent carboxylic acids is used to polymerize linear polyester. A method for producing a polyester with excellent particle affinity, characterized in that the polyester is added at any stage until the completion of the process. 2. Claim 1, wherein the carboxylic acid component of the polycarboxylic acid salt is at least one selected from the group consisting of phthalic acid, terephthalic acid, acrylic acid polymer, and maleic anhydride copolymer. Method for producing polyester as described in section. 3. The method for producing a polyester according to claim 1 or 2, wherein the amount of the polyvalent carboxylate salt relative to calcium carbonate is 0.1% to 30% by weight.