JPH0157141B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyester composition for injection molding, and its purpose is to provide a composition suitable for injection molding that has an improved crystallization rate by incorporating a specific compound. Polyesters, particularly polyethylene terephthalate, polybutylene terephthalate, etc., have excellent properties and are useful as materials for fibers, films, and other molded products, and are widely used industrially. However, such polyesters have a slow crystallization rate when used as injection molded products that are not oriented, such as fibers or films, requiring a low molding cycle or raising the mold temperature, and it is necessary to further improve the physical properties. Therefore, it is common practice to use crystallization nucleating materials and accelerators. Examples include talc, benzophenone, and higher fatty acid salts. Polyester for injection molding is generally blended with a crystallization nucleating agent (usually several microns to several tens of microns in diameter) during the compounding process in which reinforcing materials such as glass fibers and flame retardants are blended together. It is being Therefore, the dispersion of the nucleating agent is often insufficient, or the effect of the mixture is not fully expressed.
Therefore, it was necessary to use about 1% by weight of the nucleating agent. Therefore, in order to eliminate such drawbacks, the present inventors have made extensive studies and found that by finely dispersing the nucleating agent, the nucleating agent effect can be realized even in a relatively small amount, and the uniformity of physical properties can also be increased. reached. That is, the present invention provides a method for producing a polyester composition for injection molding, which comprises blending a crystal nucleating agent with an average particle size of 0.8μ or less into a polyester containing aromatic dicarboxylic acid as the main acid component and alkylene glycol as the main glycol component. This is related to. The term "polyester" used in the present invention refers to a polyester containing an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component. Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diephenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. Examples include acids. Among these, terephthalic acid is particularly preferred. Examples of the alkylene glycol include alkylene glycols having 2 to 10 carbon atoms, such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, and hexamethylene glycol. Of these,
Particularly preferred are ethylene glycol and tetramethylene glycol. Any method can be used to produce the polyester comprising the aromatic dicarboxylic acid component and glycol component. For example, to explain polyethylene terephthalate consisting of a terephthalic acid component and an ethylene glycol component, terephthalic acid and ethylene glycol may be directly esterified, dimethyl terephthalate and ethylene glycol may be transesterified, or terephthalic acid and ethylene oxide may be esterified. a first step reaction in which a glycol ester of terephthalic acid and/or a low polymer thereof is produced by reacting with
It is most commonly produced by a second stage reaction in which the reaction products of the first stage undergo a polycondensation reaction. The above polyester may be copolymerized or blended with a small amount (usually 20 mol % or less and/or 20 weight % or less) of a third component for various modification purposes. Such third components include, in addition to the aromatic dicarboxylic acids and alkylene glycols, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, aromatic dioxy compounds, alicyclic glycols, aliphatic glycols containing aromatic nuclei, and polyalkylene glycols. , aliphatic oxyacids, aromatic oxyacids, and functional derivatives thereof; polyethers, polyamides, polycarbonates, polyolefins, etc. are exemplified. Furthermore, the polyester may contain a trifunctional or higher functional compound or a monofunctional compound as long as it is considered to be substantially chain-like. In addition, it may contain catalysts and stabilizers, and if necessary, reinforcing materials such as glass fiber, carbon, pigments such as titanium oxide, dyes, antioxidants, light stabilizers, lubricants, mold release agents, etc.
The inclusion of plasticizers, dispersants, flame retardants, flame retardant aids, fillers, etc. is not only acceptable, but may also be preferable in some cases. The crystallization nucleating agent to be blended in the present invention includes organic and inorganic compounds, such as talc, clay, kaolin, asbestos, silicates, benzophenone, acetylacetone metal chelate,
Examples include metal benzoates, metal terephthalates, metal montanates, esters of montanate, and salts and esters of higher fatty acids and higher alcohols. Such a nucleating agent generally has a particle size of several microns to several tens of microns, but in the present invention, it needs to be dispersed in the polymer with a particle size of 0.8 microns or less. If it exceeds 0.8μ, no dramatic effect can be expected compared to the conventional technology. Preferably it is 0.5μ or less. Any method can be used to reduce the diameter of the nucleating agent to 0.8μ or less. For example, if the material does not melt at the temperature used for compounding or molding with resin, the nucleating agent may be used as is or together with the resin in a hammer mill.
The methods used include pulverizing with a pin mill, vibration mill, etc., dispersing it in a liquid in which the nucleating agent is not soluble, and pulverizing it with a colloid mill, sand grinder, homogenizer, etc., and then applying it to a decanter to cut off coarse particles. . In order to blend such a pulverized nucleating agent into polyester, it is preferable that the polyester has a low clay content, and when the nucleating agent is blended at the stage of transesterification reaction, a uniformly dispersed product can be obtained. When a nucleating agent is blended at the stage of a polyester polymerization reaction or when a nucleating agent is blended during compounding, partial aggregation of the nucleating agent tends to occur, so the effect of the nucleating agent (improvement of crystallization rate) cannot be fully expressed. Further, the amount of the nucleating agent added is usually sufficient in the range of 0.1 to 0.5% by weight. The molded product obtained by injection molding the polyester composition in which the nucleating agent is finely dispersed can be uniformly crystallized with a small amount of nucleating agent compared to conventional injection molded products, and there is no variation in the physical properties of the molded product. It has the great advantage of being less expensive. The present invention will be explained in more detail with reference to Examples below. In the present invention, the inherent clay of the polymer was calculated from the value measured at 35°C using orthochlorophenol as a solvent. Moreover, all parts represent parts by weight. ΔT, which represents the crystallization rate, was determined by the following method. △T=Tcd−Tci Examples 1 to 4 and Comparative Example 1 The various nucleating agents listed in Table 1 were made into a 20% ethylene glycol dispersion, and this was ground in a colloid mill to obtain the average particle diameter as listed in the table. Shattered into pieces. Put 194 parts of dimethyl terephthalate, 124 parts of ethylene glycol, and 0.141 parts of calcium acetate into a reaction kettle, and after transesterification at 120 to 240°C, add the ethylene glycol slurry of the above nucleating agent to 0.5 parts of dimethyl terephthalate. Add 0.066 parts of phosphorous acid and antimony trioxide in an amount equal to % by weight.
0.087 part was added and a high vacuum reaction was carried out at 285°C for about 190 minutes. The intrinsic viscosity of the obtained polymers was around 0.64. 70 parts of this polymer was blended with 30 parts of glass fiber (10 μm diameter, cut length approximately 5 mm), and the compound was injection molded at a cylinder temperature of 280°C and a mold temperature of 140°C. The properties of the molded product obtained were as shown in Table 1. For comparison, the same table shows the case where 0.5% by weight of commercially available talc without being crushed was blended at the time of compounding.

[Table] Example 5 and Comparative Examples 2 to 4 In place of the crystallization nucleating agent and amount listed in Table 1 in Example 1, those listed in Table 2 were added, and the compound was prepared in the same manner as in Example 1. This was then injection molded. It was found that the crystallinity and physical properties of the obtained molded article depended on the particle size of the crystallization nucleating agent, and that the crystallization rate (ΔT) exceeded 40°C when the average particle size was 0.8μ or less. When a finely dispersed crystallization nucleating agent was used, the physical properties of the molded article were uniform. The results are shown in Table 2.

[Table] Example 6 and Comparative Examples 5 to 6 The results of molded articles of polyester compositions when talc was added at the times shown in Table 3 instead of after the transesterification reaction in Example 1. Various physical properties are shown in the same table. It was found that when the addition time was late, there was not much difference in the crystallization rate, but a difference appeared in the tensile rate and its dispersion. Therefore, it can be said that it is not preferable to add a nucleating agent at the time of compound production or at the end of the polymerization reaction when the melt viscosity increases.

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Claims (1)

[Claims] 1 Reacting dicarboxylic acids mainly consisting of aromatic dicarboxylic acids or their ester-formable derivatives with glycols mainly consisting of alkylene glycols or their ester-forming derivatives to produce glycol esters of dicarboxylic acids and/or low polymers thereof. and then polycondensation of the product to produce polyester, it is recommended to add 0.1 to 0.5% by weight of a crystal nucleating agent with an average particle size of 0.8μ or less at the transesterification stage or before the polymerization reaction. A method for producing a polyester composition for injection molding.