JPS6321704B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester composition suitable as a molding material with improved crystallinity, and more specifically,
The present invention relates to a novel polyester composition that exhibits excellent moldability at low mold temperatures and provides molded articles with excellent physical properties. Polyethylene terephthalate has excellent heat resistance, chemical resistance, and electrical properties, and is used in many products as fibers and films. However, when used as an injection molded product in plastic applications, polyethylene terephthalate is subject to many restrictions in its molding process due to its unique crystallization behavior.
Therefore, despite its other excellent properties, its use is severely limited. That is, polyethylene terephthalate is an essentially crystalline polymer, but due to its slow crystallization rate, the mold temperature is
It is necessary to maintain the mold temperature above ℃, and such a high mold temperature significantly lengthens the molding cycle, which is a major negative factor in terms of productivity. Also, if the mold temperature is set to a low temperature around 100℃,
Crystallization does not proceed very well, resulting in significantly poor shape stability of the molded product, and there are drawbacks such as avatar-like patterns appearing on the surface of the molded product. Various countermeasures have been proposed in the past in order to improve these drawbacks. For example, Japanese Patent Publication No. 44-7542 discloses a method of increasing the crystallization rate by incorporating about 0.2 to 2% by weight of a nucleating agent consisting of inorganic particles, of which talc is a typical example. Furthermore, Japanese Patent Publication No. 48-4097 discloses a method of blending an alkali metal salt of an organic carboxylic acid. However, although the nucleating agents blended in these methods have the effect of increasing the crystallization rate of polyethylene terephthalate at around 200°C, this effect is hardly observed in the low temperature range, and as a result, these compositions When used as a molding material, the mold temperature still needs to be at a high temperature of 140°C or higher. Further, JP-A-54-158452 discloses a composition in which polyethylene terephthalate is blended with glass fiber, an ionomer, and neopentyl glycol dibenzoate. Such a compounding composition promotes the crystallization of polyethylene terephthalate at low temperatures, but when a molding material made of this composition is subjected to injection molding, so-called mold deposits are observed that occur in the mold cavity. In addition, defects such as resin burning occurring when the molten resin temperature exceeds 275°C have been observed. The cause of such defects is thought to be the low compatibility between the compounding agents ionomer and neopentyl glycol dibenzoate and polyethylene terephthalate, but in any case, it is even more difficult to improve moldability. The current situation is that improvements are desired. The inventors conducted intensive research to solve the above-mentioned drawbacks of polyethylene terephthalate, and as a result, they arrived at the composition of the present invention. That is, the polyester composition according to the present invention has the general formula

[expression] or

[Formula] (In the above formula, M and M' are the same or different alkali metals, and n and m are 1 or 2.) Modified polyethylene terephthalate is blended with a compound represented by the following formula before completion of polycondensation. , based on the total weight of the composition, 10 to 60% by weight of reinforcing filler as component (a) and 1 to 10% by weight of aromatic carboxylic acid ester as component (b). The polyester polymer which is the basis of the polyester composition of the present invention is a modified polyethylene terephthalate blended with a compound represented by the general formula () or () before the polycondensation is completed. The formulation of the compound represented by the above general formula () or () is as follows:
In the production process of polyethylene terephthalate, it is necessary to perform it during any of the esterification reaction, transesterification reaction, or polycondensation reaction, and even if it is blended after the completion of polycondensation of polyethylene terephthalate, the object of the present invention will not be achieved. This is supported by the fact that the crystallization rate does not increase significantly when the compound represented by the general formula () or () is blended after the completion of polycondensation of polyethylene terephthalate. General formula () or () used in the present invention
Examples of compounds represented by are p-phenolsulfonic acid disodium, 2-naphthol-6-sulfonic acid disodium, 2-naphthol-8-sulfonic acid disodium, resorcinol-4,6-disulfonic acid tetrasodium, 2,3 -Naphthalene diol-6
- Examples include trisodium sulfonate. Further, the amount of these compounds added to the polyethylene terephthalate is preferably 0.5 to 5% by weight based on the weight of the modified polyethylene terephthalate.
If this amount is small, the crystallization rate of the modified polyethylene terephthalate will not be sufficiently high. In addition, if the amount is too large, it may cause trouble when synthesizing modified polyethylene terephthalate.
Further, since the increase in the crystallization rate of the modified polyethylene terephthalate reaches almost a saturated state, there is no particular advantage. The polyethylene terephthalate used in the present invention is a homopolymer or a copolymer containing at least 70% ethylene terephthalate repeating units. Further, it is desirable that the modified polyethylene terephthalate has an intrinsic viscosity of 0.4 or more as determined from an o-chlorophenol solution. Examples of the reinforcing filler as component (a) used in the present invention include fibrous inorganic substances such as glass fiber, carbon fiber, and asbestos fiber, and non-fibrous inorganic substances such as talc and mica. When these reinforcing fillers are used in combination with component (b), they have the effect of imparting shape stability to molded products made from this composition, and at the same time, they can improve heat resistance and mechanical properties. It also produces other effects. A particularly preferred example of these reinforcing fillers is glass fiber. In addition, the amount of these reinforcing fillers is 10 to 60% by weight based on the total weight of the composition, and preferably,
15 to 55% by weight. If it is less than 10% by weight, the provision of shape stability is insufficient, and if it exceeds 60% by weight, brittleness increases and practical value decreases. The aromatic carboxylic acid ester used as component (b) in the present invention has the function of promoting crystallization of the above-mentioned modified polyethylene terephthalate over a wide temperature range. These components (b) are thought to have the effect of facilitating the molecular movement of the modified polyethylene terephthalate of the present invention, but their true nature is not necessarily clear. In any case, by blending these components (b) with the modified polyethylene terephthalate of the present invention, a composition that can be molded even at a mold temperature of around 100°C is obtained. It has been shown to act as a promoter that can crystallize in a temperature range. The inventors searched for a compound exhibiting the above-mentioned crystallization promoting effect among a vast number of compounds, and as a result, discovered aromatic carboxylic acid ester. Aromatic carboxylic acid esters used include ethylene glycol dibenzoate, propylene glycol dibenzoate, butylene glycol dibenzoate, neopentyl glycol dibenzoate, 1,6-hexadiol dibenzoate,
Benzoic acid diesters of alkylene glycols such as neopentyl glycol bis(p-tert.-butylbenzoate), benzoic acid diesters of polyalkylene glycols such as diethylene glycol dibenzoate, triethylene glycol dibenzoate, dipropylene glycol dibenzoate, and benzoic acid. Benzoic acid esters such as butyl, isoamyl benzoate, phenyl benzoate,
Also suitable are ethyl salicylate, phenyl salicylate, and the like. Particularly preferred examples among these are benzoic acid diesters of polyalkylene glycols and benzoic acid diesters of alkylene glycols. The amount of component (b) above is 1% based on the total weight of the composition.
The amount is from 2 to 10% by weight, preferably from 2 to 8% by weight. If this amount is less than 1% by weight, it will be difficult to obtain a molded product with sufficient crystallinity at a mold temperature of 100°C, and if it exceeds 10% by weight, mold deposits will occur and other problems may occur in the molding process. It will not cause any trouble. The composition using the modified polyethylene terephthalate of the present invention as a base polymer as described above has improved moldability, unlike the composition using conventional unmodified polyethylene terephthalate as a base polymer. As described above, the object of the present invention can only be achieved based on the combination of the modification method and the properties and blending amounts of components (a) and (b). The composition of the present invention can be prepared by any conventional method. For example, modified polyethylene terephthalate and component (a) may be compounded using an extruder, and then component (b) may be dry blended during molding, or all components may be compounded simultaneously using an extruder. The composition of the present invention may contain various additives, such as antioxidants, ultraviolet absorbers, lubricants, mold release agents, flame retardants, antistatic agents, colorants, etc., depending on the use and purpose. . The composition of the present invention thus obtained can be used not only for molding in high-temperature molds but also for
It shows excellent moldability even when molded in a low-humidity mold around ℃, and provides molded products with good shape stability. In this way, it has enabled molding in a low temperature range that was impossible with conventional polyethylene terephthalate, and together with its inherent heat resistance and chemical resistance, it has expanded the field of polyethylene terephthalate as an industrial resin. is big. The present invention will be explained below using examples. In addition,
In the examples, the production of modified polyethylene terephthalate, molding of test pieces, and evaluation were carried out in the following manner. (1) Production of modified polyethylene terephthalate 2000 parts of dimethyl terephthalate, 1420 parts of ethylene glycol, disodium p-phenolsulfonate (or sodium 2-naphthol-6-sulfonate)
50 parts, manganese acetate 1.0 parts, antimony trioxide 1.0
A portion of the methanol was charged into a reactor, and transesterification was carried out at 190°C for 3 hours under a nitrogen stream to distill off most of the methanol.
The polycondensation reaction was carried out at 270° C. for 4 hours under a vacuum of 1.5 g. The obtained polymer was white, had a melting point of 253-258°C, and an intrinsic viscosity of 0.60. (2) Forming of test piece Predetermined amounts of the modified polyethylene terephthalate obtained by the method of (1) and other compounding agents were weighed and mixed in a rotating drum blender. Next, add this to 40mmφ
The mixture was charged into the hopper of a vented extruder and melted and mixed at a cylinder temperature of 260-280-280°C to form pellets. The obtained pellets were dried under reduced pressure at 130°C for 5 hours,
Uses Neo Matsutto 27/48 type manufactured by Sumitomo Heavy Industries, Ltd.
ASTM No. 1 dumbbell test pieces were molded. Molding conditions are cylinder temperature 270-275-280℃, mold temperature
100℃, molding cycle 25 seconds, injection pressure 300~550
Molded at Kg/ ^cm2 . (3) Appearance of mold releasability Mold releasability was determined by separation from the mold from the cavity and sprue during molding described in (2) above. Also,
Appearance was judged based on surface gloss and presence or absence of avatars. ○: Good △: Fairly good × Poor (4) Heating shrinkage rate The width dimension of the dumbbell test piece molded in (2) above is
L ₀ and the width dimension after processing at 120° C. for 15 hours in an open gear were defined as L, and the calculation was performed using the following formula. Heating shrinkage rate (%) = L ₀ - L / L ₀ × 100 Example 1 Polyethylene terephthalate, a glass chopped trundle with a length of 6 mm (“MA 429S” Asahi Fiber Glass Co., Ltd.) and triethylene glycol dibenzoate were listed. -1 were blended in the ratio shown and subjected to molding. The molded product obtained was evaluated for its releasability, appearance, and heat shrinkage rate, and the results are shown in Table 1. All composition ratios are in percent by weight.

[Table] The effects of the present invention are clear from Table 1, but to add a supplementary explanation regarding the heat shrinkage rate, polyethylene that is not modified with the compound represented by the general formula () or () of the present invention The heat shrinkage rate of a molded product obtained from a composition containing terephthalate and 30% glass fiber at a mold temperature of 140°C was 0.20, so this level of shrinkage rate does not pose any practical problems. Conceivable. Example 2 Using the various (b) components shown in Table 2, resin compositions were produced in the same manner as in Example 1, and their moldability was examined. The results are shown in Table-2.

[Table] From Tables 1 and 2 of Examples, it is clear that the composition of the present invention has excellent moldability and shape stability, and is said to open up new uses for polyethylene terephthalate resin. It will be understood that this has great practical value.

Claims (1)

[Claims] 1 A compound represented by the general formula [Formula] or [Formula] (In the above formula, M and M' are the same or different alkali metals, and n and m are 1 or 2.) To the modified polyethylene terephthalate mixed before completion of polycondensation, 10 to 60% by weight of reinforcing filler as component (a) and 1 to 10% of aromatic carboxylic acid ester as component (b), based on the total weight of the composition. A polyester composition containing % by weight. 2. The composition according to claim 1, wherein the aromatic carboxylic acid ester is an alkylene glycol or a diester of polyalkylene glycol. 3. The composition according to claim 2, wherein the aromatic carboxylic acid is benzoic acid.