JPS6345687B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester resin composition suitable as a molding material with improved crystallinity, and more specifically to a novel polyester resin composition that exhibits excellent moldability at low mold temperatures and provides molded products with excellent physical properties. relating to things. 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 has not progressed. In other words, polyethylene terephthalate is an essentially crystalline polymer, but due to its slow crystallization rate, the mold temperature must be kept above 140°C, and such high mold temperatures significantly slow down the molding cycle. This has become a major negative factor in terms of productivity. In addition, if the mold temperature is set to a low temperature around 100℃, crystallization will not progress very much, resulting in a markedly poor shape stability of the molded product, and defects such as avatar-like patterns appearing on the surface of the molded product. It's coming. 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 fine 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-54-148833 and JP-A-54-150458 disclose a method of blending an epoxy compound of polyalkylene glycol with polyethylene terephthalate. It is said that this method promotes crystallization of polyethylene terephthalate at low temperatures. However, when a molding material made of this composition is subjected to injection molding, a so-called compounding agent bleed-out phenomenon is observed in which the mold surface becomes wet or the surface of the molded product becomes wet. This seems to be due to the low compatibility between polyethylene terephthalate and the epoxy compound of polyalkylene glycol, but in any case, from the standpoint of molding processing and use of molded products, there are problems such as bleed-out. At present, there is a desire to develop molding materials that are free of oxidation. 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 resin 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. , 10 to 60% by weight of reinforcing filler as component (a), and 0.5 to 60% of an epoxy compound selected from diglycidyl ether of alkylene glycol and diglycidyl ether of polyalkylene glycol as component (b).
It is characterized by containing 5% by weight. The polyester polymer that is the basis of the polyester resin composition of the present invention is a modified polyethylene terephthalate containing a compound represented by the general formula () or () before completion of polycondensation. The compound represented by the above general formula () or () must be blended during the esterification reaction, transesterification reaction, or polycondensation reaction in the manufacturing process of polyethylene terephthalate. Even if they are blended after the condensation is complete, 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. On the other hand, if the amount is too large, it may cause trouble when synthesizing modified polyethylene terephthalate, and the increase in the crystallization rate of modified polyethylene terephthalate will reach almost a saturated state, so there is no particular advantage. do not have. 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 preferable 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 used in combination with component (b), these reinforcing fillers 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 epoxy resin 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
Although component (b) is thought to have the effect of facilitating the molecular movement of the modified polyethylene terephthalate of the present invention, its essence 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 crystallization-promoting effect as described above among a vast number of compounds, and as a result, discovered epoxy resin. Epoxy resins used include alkylene glycol diglycidyl ethers such as neopentyl glycol diglycidyl ether, butylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. It is diglycidyl ether of polyalkylene glycol such as ether. The amount of component (b) above is based on the total composition weight.
The amount is 0.5 to 5% by weight, preferably 1 to 4% by weight. If this amount is less than 0.5% by weight,
It is difficult to obtain a molded product with sufficient crystallinity at a mold temperature of 100°C, and conversely, when the content exceeds 5% by weight, the physical properties deteriorate significantly. A composition using modified polyethylene terephthalate as a base polymer as described above is different from a composition using conventional unmodified polyethylene terephthalate as a base polymer, and bleed-out is not observed. From this fact, it can be seen that the modification of the present invention improves the compatibility between the epoxy compound and polyethylene terephthalate. in this way,
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, after compounding the modified polyethylene terephthalate and component (a) using an extruder, 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 depending on the use and purpose, such as antioxidants, ultraviolet absorbers,
A lubricant, a mold release agent, a flame retardant, an antistatic agent, a coloring agent, etc. can be added. 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-temperature mold around °C, and provides molded products with good shape stability. In this way, it has enabled molding in a low temperature range that was not possible 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 disodium 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℃ 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 Hg vacuum. The obtained polymer is white and has a melting point of 253-258℃.
The intrinsic viscosity was 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, melted and mixed at a cylinder temperature of 260-280-280°C, and pelletized. The obtained pellets were dried under reduced pressure at 130° C. for 5 hours and molded into ASTM No. 1 dumbbell test pieces using a Neomat 47/28 model (manufactured by Sumitomo Heavy Industries, Ltd.). Molding conditions are cylinder temperature 270-275-280℃, mold temperature 100℃, molding cycle 25 seconds, injection pressure 300~
Molded at 550Kg/ ^cm2 . (3) Mold releasability, appearance Mold releasability was determined by separation from the mold from the cavity and sprue during molding in (2) above. Also,
Appearance was judged based on surface gloss and presence or absence of avatars. 〇: Good, △: Fairly good, ×: Poor (4) Heating shrinkage rate The width dimension of the dumbbell test piece formed in (2) above is
L ₀ and the width dimension after processing at 120° C. for 15 hours in a gear oven were defined as L, and calculations were made using the following formula. Heating shrinkage rate (%) = L ₀ - L / L ₀ × 100 Example 1 Polyethylene terephthalate, 6 mm long glass chopped strands (MA429S Asahi Fiberglass Co., Ltd.) and neopentyl glycol diglycidyl ether are shown in Table 1. They were mixed in the proportions 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 1 shows that the composition of the present invention has excellent moldability as an injection molding material.

[Table] 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 diglycidyl ether of alkylene glycol and polyalkylene as component (b), based on the total weight of the composition. A polyester resin composition containing 0.5 to 5% by weight of an epoxy compound selected from glycol diglycidyl ethers.