Polyetylene terephthalate resin composition

Abstract

[Problem] To provide a polyethylene terephthalate resin composition which can be molded under substantially the same conditions as those for a polybutylene terephthalate resin, wherein the crystallization speed of the polyethylene terephthalate resin composition in a single resin system can further be adjusted. [Solution] In the polyethylene terephthalate resin composition, 0.01-2.0 parts by weight of an organic carboxylic acid metal salt (C) is contained in a composition obtained by blending 0.01-1.0 parts by weight of fumed silica (B) with 100 parts by weight of a polyethylene terephthalate resin (A), wherein 0.1-2.0 parts by weight of bamboo charcoal (D) having an average particle diameter of 30 μm or less is further blended with said composition.

Description

Polyethylene terephthalate resin composition

[0001] The present invention relates to a polyethylene terephthalate resin composition having a controlled crystallization rate.

[0002] Polyethylene terephthalate resin, a type of thermoplastic semi-aromatic polyester resin, is a resin with a good balance of mechanical properties, transparency, chemical resistance, aroma retention, cold resistance, recyclability, and economy, and is used in large quantities, mainly in fibers, films, sheets, and thin-walled products obtained by processing these, such as clothing, plastic bags, food containers, and beverage bottles. In recent years, with the expansion of beverage bottle production in particular, horizontal recycling, in which beverage bottles are collected and regenerated through processes such as washing, and then expanded into beverage bottle products, is gaining momentum from an environmental perspective.

[0003] Polyethylene terephthalate resin was invented in 1949, and production has expanded to the present day, primarily for textiles. Although it has a high melting point of 250-260°C, most of its use is in textiles and water bottles, which are used at room temperature. As production and usage increase, it would be desirable from an environmental perspective to recycle polyethylene terephthalate resin and convert it into products that take advantage of its high melting point, in line with the SDGs.

[0004] However, while polyolefins, polyamide resins, polyacetals, and other resins are widely used in injection molding, polyethylene terephthalate resin products are rarely used in injection molding. The reason for this is that, despite being a crystalline resin, its crystallization rate is significantly slower than that of other crystalline resins such as polyolefins and polyamides, making it unsuitable for molding thick-walled products obtained by injection molding, extrusion molding, press molding, and other methods. Glass fiber-reinforced polyethylene terephthalate resins, containing 10 parts by weight of glass fiber (preferably 30-50 parts by weight), have a high melting point among engineering resins, so the mold temperature during injection molding is set to 130-150°C. Even so, it takes 3-5 minutes for the resin to be ejected. While molding can sometimes be done at a water-cooled mold temperature of 30-60°C, the ejected product must be fitted into a correction jig and subjected to an annealing process to eliminate warpage. Ultimately, molding polyethylene terephthalate resin has the drawback of requiring a long total cycle.

[0005] Polybutylene terephthalate resin was introduced in 1970 with the aim of dramatically improving the crystallization rate of polyethylene terephthalate resin. Compared to polyethylene terephthalate resin, it crystallizes approximately three times faster under the same cooling conditions. Even with glass fiber reinforcement, it can be molded at mold temperatures of 70-90°C, resulting in a short molding cycle. It boasts excellent electrical and mechanical properties, chemical resistance, dimensional stability, and colorability. It is widely used in a variety of parts, particularly internal mechanisms, in the electrical and electronics fields, particularly connectors; automotive and industrial machinery fields, such as door handles; office equipment such as personal computers; home appliance housings; and housing materials. The length (n) of the alkyl group that undergoes condensation polymerization with terephthalic acid is 4 for polybutylene terephthalate resin, compared to 2 for polyethylene terephthalate resin, making molecular chain rotation easier and resulting in faster crystallization.

[0006] Although polybutylene terephthalate resin has expanded its market share in the field of molded products, it faces challenges in material recycling. Most products are compound materials made from glass fiber alone or in combination with inorganic fillers. In the case of connectors, for example, the concentration of glass fiber and inorganic filler compounded varies depending on the connector shape and application. Colors range from black to multicolored. Furthermore, halogen-based flame retardants are the norm, and non-halogen flame retardants are mixed in, making separation difficult even when products are collected. Recycled polybutylene terephthalate resin can only be produced by in-process blending of the same or similar grades.

[0007] On the other hand, polyethylene terephthalate resin has a large market size. A system for sorting and collecting used beverage bottles from the city has been established, and the resin has characteristics such as nearly identical quality in terms of intrinsic viscosity (IV) value. If this advantage could be utilized to enable polyethylene terephthalate resin to have a crystallization rate similar to that of polybutylene terephthalate, it would be extremely significant in preventing global warming and wasting resources. However, this was not possible with conventional technology.

[0008] Furthermore, polybutylene terephthalate resin, which replaced polyethylene terephthalate resin, has a crystallization rate that is too fast, causing problems in some applications. This is particularly true for glass fiber-reinforced materials, which can result in poor product appearance after injection molding. When glass fiber-reinforced polybutylene terephthalate resin is injected into a mold, the glass fibers in contact with the mold surface do not shrink, but the matrix polybutylene terephthalate rapidly crystallizes and shrinks in volume, resulting in the glass fibers floating on the surface. Even when a paint is applied, the roughness of the base affects the paint's reflection, resulting in poor paint reflection.

[0009] As a countermeasure, a polystyrene-based amorphous resin or a polyethylene terephthalate resin with a slow crystallization rate is usually blended. It is known that blending polybutylene phthalate resin with polyethylene phthalate resin causes transesterification under certain elapsed time and temperature conditions, resulting in a decrease in heat resistance. For this reason, polyethylene terephthalate resin is required to have a crystallization rate similar to that of polybutylene terephthalate resin, while polybutylene terephthalate resin has a crystallization rate that is too fast. It would be a major advance if polyethylene terephthalate alone could achieve the moldability and physical properties of a blend of polybutylene terephthalate and polyethylene terephthalate. However, such control technology has not existed until now.

[0010] An object of the present invention is to develop a polyethylene terephthalate resin composition that can be molded under conditions, such as mold temperature and cooling cycle, that are approximately equivalent to those of polybutylene terephthalate resin, for example, in injection molding, and further to develop a polyethylene terephthalate resin composition whose crystallization rate can be adjusted as a single resin system, without blending polyethylene phthalate resin to improve the appearance of glass fiber or carbon fiber reinforced materials, which is caused by the excessively fast crystallization rate of polybutylene terephthalate.

[0011] Research into improving the crystallization rate of polyethylene terephthalate resin has been ongoing since the resin's inception. Patent Document 1 presents the results of evaluation of crystallization nucleating agents in polyethylene terephthalate resin, melt-extruded to which 1.0 wt.% of various nucleating agents was added, based on optical measurements of the crystallization induction period, crystallization half-time, and intrinsic viscosity. Examples of ineffective substances include Zn powder and Al powder. Examples of metal oxides include Fe2O3, TiO2, MnO2, SiO2, and Fe3O4. Examples of inorganic substances include Na2CO3, K2CO3, CaCO3, Zn2CO3, and Mg2CO3. Examples of clay substances include kaolin, acid clay, celite, and clay. Examples of organic substances include sodium oxalate, sodium benzoate, sodium phthalate, and sodium naphthalenesulfonate. Crystalline polymers such as polypropylene and nylon are considered ineffective. Substances that have been shown to be effective include graphite, carbon black, ZnO, MgO, CaSiO2, talc, calcium oxalate, calcium benzoate, magnesium stearate, calcium tartrate, and zinc salicylate.

[0012] Patent Document 2 presents the results of measuring the crystallization temperature using the DSC method for samples containing 2.0 wt% of various crystallization nucleating agents. The sample was melted in a nitrogen stream at 300°C for 10 minutes and then cooled at a rate of 10°C / min. The crystallization temperature was determined as the exothermic peak. A high exothermic peak temperature and a sharp exothermic curve (due to crystallization) indicate a fast crystallization rate. However, while a high exothermic peak temperature and crystallization rate are relevant when comparing materials of the same type, they are meaningless when comparing different materials, such as polypropylene resin. When comparing materials of the same type, it is important to compare both the sharpness of the exothermic curve and the calorific value, which reflects the degree of crystallization. According to this document, inorganic substances with broad exothermic curves (i.e., lacking crystallization nucleating ability) include talc, TiO2, SiO2, K2CO3, and CaCO3. Organic compounds include sodium terephthalate (potassium and calcium), lithium benzoate, and aluminum benzoate. Lithium terephthalate, potassium benzoate, and sodium stearate are listed as compounds with sharp exothermic curves.

[0013] In Patent Documents 1 and 2, some compounds are said to be ineffective, while others are said to be effective, and it is clear that they are not clearly organized. In Patent Documents 1 and 2, the compounds with the same chemical formula as the fumed silica used in the present invention described later, SiO ２ In all the evaluation results, SiO ２ It is described that the effect of accelerating the crystallization rate of polyethylene terephthalate resin by the method is low.

[0014] Patent Document 3 discloses a technique for adding fumed silica to polyethylene terephthalate resin. It states that adding 0.01 to 1.0 wt. % of ultrafine silica particles with an average particle size of 70 nm or less ensures transparency of the container obtained by thermoforming the sheet and also provides slip properties. "Transparency" means that the sheet is not crystallized. This indicates that, until the present invention, it was not known that fumed silica could crystallize polyethylene terephthalate resin.

[0015] Japanese Patent Publication No. 44-7542 Publication No. 47-14502 Japanese Patent Publication No. 4-136063

[0016] An object of the present invention is to provide a polyethylene terephthalate resin composition that can be molded under conditions substantially equivalent to those for polybutylene terephthalate resin, and further to provide a polyethylene terephthalate resin composition that allows adjustment of the crystallization rate in a single resin system.

[0017] The polyethylene terephthalate resin composition of the present invention comprises a composition obtained by blending 100 parts by weight of polyethylene terephthalate resin (A) with 0.01 to 1.0 part by weight of fumed silica (B), and 0.01 to 2.0 parts by weight of an organic carboxylic acid metal salt (C). The polyethylene terephthalate resin composition of the present invention comprises a composition obtained by blending 100 parts by weight of polyethylene terephthalate resin (A) with 0.01 to 1.0 part by weight of fumed silica (B) and 0.1 to 2.0 parts by weight of bamboo charcoal (D) having an average particle size of 30 μm or less, and 0.01 to 2.0 parts by weight of an organic carboxylic acid metal salt (C).

[0018] The polyethylene terephthalate resin (A) according to the present invention is a recycled polyethylene terephthalate resin. The organic metal carboxylate (C) according to the present invention is a metal benzoate and a metal stearate. When the polyethylene terephthalate resin (A) according to the present invention is a recycled polyethylene terephthalate resin, the organic metal carboxylate (C) is a metal benzoate and a metal stearate.

[0019] The present invention comprises blending 60 to 10 wt% of glass fibers with 40 to 90 wt% of a polyethylene terephthalate resin composition. When the polyethylene terephthalate resin (A) according to the present invention is a recycled polyethylene terephthalate resin, the polyethylene terephthalate resin composition comprises blending 60 to 10 wt% of glass fibers with 40 to 90 wt% of the polyethylene terephthalate resin composition. The polyethylene terephthalate resin composition of the present invention is a polyethylene terephthalate resin composition having a difference between the crystallization peak temperature and the melting peak temperature measured by a differential scanning calorimeter of 45°C or less. The measurement conditions for the differential scanning calorimeter are as follows: the polyethylene terephthalate resin is heated to 300°C at a heating rate of 10°C / min in a nitrogen atmosphere to melt, held for 5 minutes, and then cooled to 70°C at a cooling rate of 10°C / min, from which the crystallization peak temperature is determined from the crystallization exothermic curve; the polyethylene terephthalate resin is then held at 70°C for 5 minutes, after which it is heated to 280°C at a heating rate of 10°C / min, from which the melting peak temperature is determined from the melting endothermic curve.

[0020] The polyethylene terephthalate resin composition of the present invention has a fast crystallization rate, excellent moldability, and higher heat resistance than polybutylene terephthalate resin. The fumed silica used as a crystallization accelerator in the present invention is ultrafine, and the amount added is very small. The amounts of organic carboxylic acid metal salt and bamboo charcoal powder used as a crystallization rate adjuster are also small, so molded products can be obtained with little deterioration in mechanical properties or thermal stability during processing. Furthermore, a polyethylene terephthalate resin composition containing 40 to 90% by weight of a resin composition and 60 to 10% by weight of glass fiber has mechanical strength and thermal properties equivalent to or greater than those of glass fiber-reinforced polybutylene terephthalate resin.

[0021] The polyethylene terephthalate resin composition of the present invention will be described in detail below with reference to examples. The scope of the present invention is not limited by these examples. The polyethylene terephthalate resin (A) used in the present invention is a polycondensate or copolymer containing the same as the main component, consisting of terephthalic acid or its ester-forming derivative as the dicarboxylic acid component and ethylene glycol or its ester-forming derivative as the diol component. It is produced by a known method and has a high melting point of 240 to 260°C. The molecular weight varies depending on the application, but the intrinsic viscosity (IV value) is 0.5 to 0.6 for fibers, around 0.7 for sheets for packaging containers, and 0.7 to 1.2 for bottles. The present invention is applicable to polyethylene terephthalate resins of any intrinsic viscosity.

[0022] Here, recycled polyethylene terephthalate resin can be obtained by crushing and using polyethylene terephthalate resin generated during the manufacturing process, such as off-spec products or trimmings from sheet molding, or by processing collected polyethylene terephthalate resin for reuse. In the case of polyethylene terephthalate resin, much of it is collected after being distributed in the market as food packaging sheets and beverage bottles. In the case of beverage bottles, collected products from the market are classified and sorted by contamination level. Foreign matter contamination is monitored using infrared spectroscopy to select only polyethylene terephthalate resin. Bottle caps, which are made of polyethylene or polypropylene, are removed, and labels are also peeled and separated. The material is then cut into flakes using a mechanical cutter.

[0023] Next, the flakes are washed with a specified alkaline solution to separate out any contaminants present in the market. They are then neutralized, washed with water, and vacuum-dried before being shipped as flakes. Alternatively, they are melt-extruded in an extruder to achieve the same pellet size as virgin polyethylene terephthalate resin. The molecular weight is reduced by heat and light during the molding process and in the market. In such cases, methods such as solid-phase polymerization are used to adjust the degree of polymerization. Additionally, molecular weight (intrinsic viscosity (IV) value) can be adjusted by blending with polyethylene terephthalate resin with a higher IV value, or by reacting with a chain extender in the extruder to increase the IV value.

[0024] The present invention can be applied to any recycled polyethylene terephthalate resin. In general, rather than directly blending with a high-IV polyethylene terephthalate resin, it is preferable in terms of dispersion to prepare a high-concentration masterbatch using a polyethylene terephthalate resin with a slightly lower molecular weight (IV value of 0.5 to 0.7) and blend it with a high-IV polyethylene terephthalate resin. The present invention can also be applied when recycled polyethylene terephthalate resin is used as an alloy resin material. In such cases, the fast crystallization rate of the polyethylene terephthalate resin is sometimes preferred, and the present invention can be applied. The present invention can ensure improved molding cycles for polymer alloys with high strength, precision, and high impact resistance, such as polyphenylene ether resin, polyphenylene sulfide resin, polystyrene resin, and ABS (acrylonitrile butadiene styrene) resin.

[0025] The fumed silica (B) used in the present invention is dry silica (fumed silica, pyrogenic silica) obtained by the combustion reaction of a silicon compound. Dry methods for producing silica include flame hydrolysis, arc fusion, and plasma fusion, but the currently predominant industrial production method is flame hydrolysis. In flame hydrolysis, a silicon compound, particularly a silicon halide, generally a silicon chloride, usually purified silicon tetrachloride, is produced by burning and hydrolyzing it in a high-temperature (usually 1000°C or higher) oxygen and hydrogen flame. Because the gas mixture containing vaporized silicon tetrachloride (boiling point 59°C) is homogeneous, the silica produced in this manner is in the form of an aerosol consisting of highly uniform, uniform, high-purity amorphous silica particles, which appears as a mist, hence the name fumed silica.

[0026] Fumed silica (B) is produced by a known dry process. Compared to other silicas, non-fumed silica has extremely small primary particles ranging from several nanometers to several tens of nanometers, and these primary particles aggregate together in a beaded pattern to form nano-sized secondary particles. These particles are characterized by extremely strong cohesive forces.

[0027] The fumed silica used in the present invention has an extremely fine particle size, which is strongly related to its strong cohesion. Primary particles with a diameter of approximately 5 to 50 nm aggregate into a string-like structure due to interparticle hydrogen bonding and entanglement caused by silanol groups on the surface, forming aggregates with particle diameters of approximately 100 to 400 nm, which become secondary particles. The secondary particles then gather together to form bulky agglomerated particles.

[0028] The fumed silica used in the present invention may be hydrophilic or hydrophobic. When using hydrophilic fumed silica, particularly when using it to prepare a masterbatch of polyethylene terephthalate resin and high-concentration hydrophilic fumed silica, a silane coupling agent may be used in combination. Fumed silica has extremely low hygroscopicity compared to other amorphous silicas, and since the amount added in the present invention is extremely small, it has little effect on the polyethylene terephthalate resin.

[0029] In Japan, fumed silica is manufactured at the Yokkaichi Plant, for example, and many grades are sold by Nippon Aerosil Co., Ltd. In addition, some fumed silica grades have passed the U.S. Food and Drug Administration (FDA), making them suitable for a wide range of applications.

[0030] The amount of fumed silica added is in the range of 0.01 to 1.0 part by weight relative to 100 parts by weight of polyethylene terephthalate resin. If the amount added is less than 0.01 part by weight, the crystallization promoting effect cannot be obtained, and even if the amount added exceeds 1.0 part by weight, the effect does not improve proportionally, and the crystallization promoting effect reaches a plateau.

[0031] The organic carboxylic acid metal salt (C) used in the present invention is a metal salt of a carboxylic acid (or a derivative thereof) having a hydrocarbon group of 2 to 30 carbon atoms and belonging to Groups 1 and 2 of the Periodic Table. Here, the hydrocarbon group includes, for example, an alkyl group and a cyclic hydrocarbon group having a cyclo or benzozene ring. Among these, alkyl and aryl groups are preferred. Specific examples of metal stearates include sodium stearate, potassium stearate, magnesium stearate, lithium stearate, and calcium stearate. Specific examples of metal montanates include sodium montanate and magnesium montanate. Specific examples of aromatic carboxylic acid metal salts include sodium benzoate, potassium benzoate, calcium benzoate, and lithium terephthalate. Among organic carboxylic acid metal salts, sodium stearate and potassium stearate are preferred, and among aromatic carboxylic acid metal salts, sodium benzoate and potassium benzoate are particularly preferred.

[0032] In the present invention, these organic carboxylic acid metal salts may be used alone or in combination of two or more. These organic carboxylic acid metal salts have been studied in the past as nucleating agents for polyethylene terephthalate, but their crystallization rates have not yet reached the same level as those of polybutylene terephthalate resins that can replace them.

[0033] The amount of organic carboxylic acid metal salt added is preferably 0.01 to 2.0 parts by weight per 100 parts by weight of polyethylene terephthalate resin. If the amount is less than 0.01 part by weight, the effect as a crystallization accelerator is insufficient, and even if the amount exceeds 2.0 parts by weight, the effect is the same and it is wasted.

[0034] Bamboo charcoal (D) is a bamboo charcoal powder with an average particle size of 30 μm or less. The bamboo species used as raw material are not particularly limited, but include Madake (Madake), Moso Bamboo (Moso Bamboo), Azatake (Azatake), Metake (Me-bamboo), Kurochiku (Black Bamboo), Hotei Bamboo (Hotei Bamboo), Shihochiku (Four-sided Bamboo), Touchiku (Tang Bamboo), Kumazasa (Kuma Sasa), Kushima Sasa (Kuril Sasa), and Miyakozasa (Miyako Sasa). These bamboos are heat-treated, crushed, and classified in an earthenware kiln, rotary kiln, or double kiln system at temperatures above 600°C, preferably above 800°C. There is also edible bamboo charcoal. It is treated at high temperatures until lignin is decomposed and burned to the point where no residue remains. The average particle size of bamboo charcoal varies depending on the furnace conditions, but is generally 10 μm or less for edible use and 25 μm for industrial use. It can be used as a crystallization promoter in the present invention.

[0035] The amount of bamboo charcoal blended is 0.1 to 2.0 parts by weight per 100 parts by weight of polyethylene terephthalate resin. Preferably, it is 0.05 to 2.0 parts by weight. Less than 0.1 parts by weight is ineffective, and blending in excess of 2.0 parts by weight does not affect the effect. In fact, it makes the black color darker, which can be an obstacle to color matching.

[0036] The reasons why bamboo charcoal is preferred for its use are: 1) it is convenient for adjusting the crystallization rate, and 2) it has an antistatic effect when blending fumed silica with resin, stabilizing the kneading process. The reason for 1) is that, as mentioned above, the crystallization rate of polybutylene terephthalate is very fast, which can lead to a deterioration in appearance, especially in glass fiber reinforced materials. As a countermeasure, bamboo charcoal can be added to a low concentration blend of fumed silica to adjust the crystallization rate.

[0037] The inventors turned their attention to bamboo charcoal while investigating composite resins containing biomaterials. They had thought that combining it with recycled polyethylene terephthalate would be environmentally friendly, but they were surprised to find that bamboo charcoal also had a crystallization-promoting effect. When recycled polyethylene terephthalate without bamboo charcoal was mixed in a Plastomill mixer, a molten substance resembling starch syrup flowed out of the mixer. However, when bamboo charcoal was mixed in, the molten substance did not flow, and crystallization progressed immediately after it was scraped out of the mixer and exposed to room temperature.

[0038] Melt-kneading is carried out using a known kneading device widely used in the production of thermoplastic resin compositions. Specific kneading devices include Brabender mixers, Banbury mixers, single-screw extruders, twin-screw extruders, rolls, kneaders, etc. Among these, melt-kneading using a twin-screw kneader is preferred due to its industrial cost efficiency and excellent shear-kneading capabilities. Furthermore, it is even more preferable if the twin-screw extruder is equipped with multiple feed ports and raw material supply devices (feeders). Depending on the raw material form, feeder supply accuracy, kneading order, etc., it is possible to feed each component independently without premixing, or to premix only some components and feed them. Furthermore, using a masterbatch containing fumed silica, organic carboxylic acid metal salt powder, or bamboo charcoal powder is also preferred because it can reduce the deterioration of the working environment due to powder scattering and dust generation and has excellent powder dispersion effects.

[0039] To improve physical properties, inorganic fillers or reinforcing materials such as mica, talc, clay, graphite, calcium carbonate, calcium sulfate, titanium oxide, glass beads, glass fiber, and carbon fiber may be blended into the polyethylene terephthalate resin composition of the present invention, provided that the objectives of the present invention are not impaired. Glass fiber is particularly preferred because it can impart high strength and toughness, high heat resistance including low creep at high temperatures, and excellent performance in terms of abrasion resistance, chemical resistance, and dimensional stability. In the present invention, 60 to 10 wt% of glass fiber is blended with 40 to 90 wt% of the polyethylene terephthalate resin composition. The blending ratio is determined taking into account the strength, heat resistance, and other properties of the desired product. A range of 15 to 50 wt%, with 30 wt% as the center, is preferred.

[0040] Various additives may also be blended within the scope of not impairing the features of the present invention. Specific examples include various antioxidants such as hindered phenols, various heat stabilizers such as phosphites, various release agents such as olefin waxes and fatty acid esters, dispersants, thickeners, plasticizers, antiblocking agents, phenolic antibacterial and antifungal agents, anionic, cationic, and nonionic antistatic agents, colorants, etc., and a plurality of these additives may also be blended.

[0041] The polyethylene terephthalate resin composition of the present invention can be molded by a conventional molding method using a molding machine for general thermoplastic resins. When conventional glass fiber reinforced polyethylene terephthalate is injection molded, the mold temperature is set to 130°C to 150°C, but the present invention makes it possible to mold the composition under the same mold temperature conditions of 80 to 100°C as for polybutylene resin.

[0042] The present invention will now be described in more detail with reference to examples. The raw materials used in the examples and comparative examples are as follows: (A) Polyethylene terephthalate resin: crushed flakes from recycled beverage bottles, manufactured by Kyoei Sangyo Co., Ltd., IV value 0.68; (B) Fumed silica: Aerosil RY200L, manufactured by Nippon Aerosil Co., Ltd., surface treated with dimethylpolysiloxane, primary particle diameter 12 nm, specific surface area 100±20 m ２ / g (C) Organic carboxylic acid metal salts Sodium benzoate: Reagent, Fujifilm Wako Pure Chemical Industries, Ltd. Sodium stearate: Reagent, Fujifilm Wako Pure Chemical Industries, Ltd. (D) Bamboo charcoal: Bamboo charcoal powder (edible bamboo charcoal fine powder) from Taketan no Sato (Miyazaki Prefecture) Average particle size 5.46 μm (median size 5.21 μm) Particle size measurement: Laser diffraction / scattering particle size distribution measurement device LA-950V2, manufactured by Horiba, Ltd. Polybutylene terephthalate resin: Novaduran 5010R5, manufactured by Mitsubishi Chemical Corporation

[0043] <Crystallization Temperature and Melting Temperature Measurement> Crystallization temperature was measured by thermal analysis. Using a Shimadzu Corporation DSC-60 differential scanning calorimeter, a sample was melted in a nitrogen stream at 300°C for 5 minutes, then cooled at a rate of 10°C / min. The crystallization onset temperature, peak crystallization temperature, and end crystallization temperature were determined when the sample crystallized within the time period up to 70°C. The sample was then held at 70°C for 5 minutes, then heated at a heating rate of 10°C / min. The melting onset temperature, peak crystallization temperature, and end crystallization temperature were determined when the sample melted within the time period up to 280°C. Generally, the crystallization rate is measured by measuring the distance (H) from the crystallization peak relative to the crystallization onset temperature and crystallization end temperature range (W) on a chart, with a larger H / W ratio indicating a faster crystallization rate. The problem with chart measurements is that there is a considerable degree of human error, so this should only be used as a guide. Similarly, the degree of crystallization is sometimes expressed as the area ratio of the crystalline region, but this is not recommended for polyethylene terephthalate resins due to the ambiguity of the amorphous region area. Therefore, in the case of crystalline resins, it is generally believed that a large difference between the melting point and crystallization temperature means that a large proportion of the resin can crystallize, and that this has a nucleating agent effect.Since both the crystallization peak and melting peak are displayed digitally and there is no artificial judgment involved, the temperature difference between the melting peak temperature and the crystallization peak temperature was evaluated as the crystallization promotion effect.

[0044] <Observation of mold release and crystallization during press molding> Press moldability was evaluated using two mini test presses manufactured by Toyo Seiki Seisakusho Co., Ltd., using the following method. (Hot pressing process) The resin was filled into a brass mold measuring 85 mm x 50 mm x 2 mm thick, and covered from the top and bottom with ferromagnetic plates (stainless steel gloss plates). The resin was pressed at a temperature of 270 ° C, for 6 minutes, and at a pressure of 3 MPa for 1 minute. (Cooling pressing process) The resin was set and pressed for 10 seconds in a press heated to 140 ° C, and then transferred to a water-cooled press and pressed at 3 MPa. The adhesiveness of the pressed resin was checked when peeling it from the ferromagnetic plate. Strong adhesiveness indicates poor crystallization.

[0045] A piece of 50 mm x 25 mm x 0.3 mm was cut from the sheet obtained through the pressing process, placed on a U-shaped box of a stainless steel U-shaped heat resistance evaluation jig with a support distance of 30 mm, and placed in a heating oven at 220°C to observe deformation.

[0046] To 100 parts by weight of polyethylene terephthalate resin, 0.1 parts by weight of fumed silica, 0.3 parts by weight of sodium benzoate, and 0.4 parts by weight of sodium stearate were added, and the mixture was melt-kneaded for 10 minutes at 280°C and 100 rpm using a Labo Plastomill 4C150 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to prepare a kneaded sample. The front cylinder block of the Plastomill device was removed, and the molten polyethylene terephthalate resin was sampled. Upon removal of the cylinder block, the molten material turned white, confirming a rapid crystallization rate. Regarding the cooling time and demolding during press molding, it was confirmed that the press mold could be removed after 15 seconds of cooling. Next, the heat resistance of the press-molded product at 220°C was evaluated, and the product did not fall off the jig even after 30 minutes. The results of differential scanning calorimetry (DSC) are summarized in Table 1. In Table 1, polyethylene terephthalate resin is referred to as "PET resin" and polybutylene terephthalate resin is referred to as "PBT resin."

[0047] The temperature difference between the melting peak temperature and the crystallization peak temperature of the resin composition of Example 1 is 34.1° C. The temperature difference of the polybutylene terephthalate resin (PBT resin) given as a reference example is 34.6° C., which shows that the polyethylene terephthalate resin composition of Example 1 has approximately the same crystallization rate as the polybutylene terephthalate resin.

[0048]

[0049] A kneaded sample was prepared under the same conditions as in Example 1, except that the amount of fumed silica added was 0.5 parts by weight. In this example, after kneading, the front cylinder block of the Plastomill apparatus was removed and an attempt was made to sample the molten polyethylene terephthalate resin, but it instantly turned white. Crystallization progressed during hot press molding, and the resin showed no deformation when removed from the mold. The heat resistance of the press-molded product was then evaluated at 220°C, and it did not fall off the jig even after 30 minutes.

[0050] The resin composition of Example 2 has a temperature difference between the melting peak temperature and the crystallization peak temperature of 33.5° C. The temperature difference of the polybutylene terephthalate resin (PBT resin) given as a reference example is 34.6° C., so the polyethylene terephthalate resin composition of Example 2 is faster than the polybutylene terephthalate resin.

[0051] A kneaded sample was prepared under the same conditions as in Example 1, except that the amount of fumed silica added was 0.05 parts by weight, the amounts of sodium benzoate and sodium stearate were 0.3 and 0.4 parts by weight, respectively, and bamboo charcoal powder was 0.5 parts by weight. In this example, too, after kneading, the front cylinder block of the Plastomill device was removed and the molten polyethylene terephthalate resin was sampled. The color of the molten material containing the bamboo charcoal powder was black, but crystallization had progressed during sampling. Crystallization progressed during hot press molding, and the resin did not deform when removed from the mold. The heat resistance of the press-molded product was evaluated at 220°C, and it did not fall off the jig even after 30 minutes.

[0052] The resin composition of Example 3 has a temperature difference between the melting peak temperature and the crystallization peak temperature of 39.5° C. The temperature difference for the polybutylene terephthalate resin (PBT resin) given as a reference example is 34.6° C., which demonstrates that in fields where a slower crystallization rate is required for polybutylene terephthalate resin depending on the application, it is possible to adjust the crystallization rate using polyethylene terephthalate resin alone.

[0053] A 70% by weight mixture consisting of 100 parts by weight of polyethylene terephthalate resin, 0.5 parts by weight of fumed silica, 0.3 parts by weight of sodium benzoate, and 0.4 parts by weight of sodium stearate was fed from the main hopper of a co-rotating twin-screw kneading extruder HK-25D (manufactured by Parker Corporation), and 30% by weight of glass fiber (CS 3PE-044S, manufactured by Nitto Boseki Co., Ltd.) was fed from the side feeder of the extruder. The kneading conditions were as follows: cylinder temperature 250°C, screw rotation speed 150 rpm, feed rate 7.0 / hour. The molten strand extruded from the die was cooled on a belt conveyor equipped with three air-cooling fans and cut into pellets using a pelletizer.

[0054] The distance from the cooling belt conveyor to the pellet cutter was 1.100 mm, and it was observed that the molten strands began to crystallize approximately halfway along the belt conveyor. The strands did not droop down to the pellet cutter. The results of differential scanning calorimetry (DSC) of the pellets of Example 4 are shown in Table 2. In Table 2, polyethylene terephthalate resin is referred to as "PET resin." As shown in Table 2, the temperature difference between the melting peak temperature and the crystallization peak temperature was 37.31°C.

[0055] Next, the pellets were pre-dried at 120°C for 6 hours and then injection-molded using an injection molding machine (electric injection molding machine NEX140, manufactured by Nissei Plastic Industrial Co., Ltd., clamping force 140 tf, screw diameter 40φ full-flight screw). The injection molding and mold conditions were as follows: cylinder set temperature 270°C, mold set temperature 85°C, injection pressure 93 MPa, injection time 2.3 seconds. The mold used was a JIS K 7139 Type A (4 mm thick, double-cavity multipurpose test piece). Under these conditions, 30 shots were molded with cooling times of 30, 20, and 15 seconds, and the molded products were successfully removed without any problems.

[0056] The flexural modulus and flexural stress of the molded product were determined using a bending test according to JIS K 7171;2016 (Shimadzu Corporation Autograph AGX-50kNV, load cell capacity 50 kN, speed 2 mm / min). The flexural modulus and flexural stress are shown in Table 2. Furthermore, the heat distortion temperature was measured according to JIS K7179-1,2 2015 (Toyo Seiki Co., Ltd. HDT testing equipment) using a test starting temperature of 30°C, a heating rate of 120°C / hour, and a flexural stress of 1.80 MPa to determine the temperature at which the deflection reached 0.34 mm. The results are shown in Table 2.

[0057] Example 1 showed that injection was possible at a mold temperature of 85°C, whereas conventional molding of glass fiber reinforced polyethylene phthalate required a mold temperature of 130-150°C. The cooling time was shortened. The physical properties of the molded product were higher than those of polybutylene terephthalate.

[0058] A 70% by weight mixture consisting of 100 parts by weight of polyethylene terephthalate resin, 0.5 parts by weight of fumed silica, 0.3 parts by weight of sodium benzoate, 0.4 parts by weight of sodium stearate, and 0.1 parts by weight of bamboo charcoal powder was blended with 30% by weight of glass fiber. A product was obtained by the same kneading and injection molding as in Example 4. The temperature difference between the melting peak temperature and the crystallization peak temperature in differential scanning calorimetry (DSC) was 36.72°C. In this example, products were obtained without any problems when the cooling and removal time from injection molding was 30, 20, or 15 seconds. The flexural modulus, flexural stress, and heat distortion temperature are shown in Table 2. It was found that the addition of bamboo charcoal powder resulted in a favorable heat distortion temperature.

[0059]

[0060] Comparative Example 1: The polyethylene phthalate used in Example 1 was melt-mixed in a Plastomill at 280°C and 100 rpm for 10 minutes. When the front cylinder block of the Plastomill was slid open to remove it, the molten polyethylene terephthalate resin dripped from the gap like a syrup. The molten material was transparent. During press molding, the molded product was soft and insufficiently crystallized. The molded product adhered to the mold and ferroelectric plate, causing deformation of the sheet molded product upon removal from the mold. A stable removal time of 240 seconds was required. The heat resistance of the resulting press-molded product at 220°C was evaluated, showing that it fell off within 15 seconds of being set in the jig. The temperature difference between the melting peak temperature and the crystallization peak temperature in differential scanning calorimetry (DSC) was 62.7°C, indicating an extremely slow crystallization rate.

[0061] Comparative Example 2: 0.05 parts by weight of fumed silica was added to 100 parts by weight of polyethylene terephthalate resin, and the mixture was melt-kneaded for 10 minutes at 280°C and 100 rpm using a Labo Plastomill to prepare a kneaded sample. The sample was crystallized upon removal from the Plastomill. It was found that even a small amount of added silica promotes the crystallization of polyethylene terephthalate resin. The heat resistance of the resulting press-molded product at 220°C was evaluated, and it did not fall off even 30 minutes after being set in the jig. The temperature difference between the melting peak temperature and the crystallization peak temperature in differential scanning calorimetry (DSC) was 48.4°C, which is lower than that of polybutylene terephthalate resin (PBT resin). The DSC and other results for Comparative Examples 1 and 2 are summarized in Table 1.

[0062] Comparative Example 3: The same experiment as in Example 4 was conducted, except that 70% by weight of polyethylene terephthalate resin was fed from the main hopper of the co-rotating twin-screw kneader and 30% by weight of glass fiber was fed from a side feeder. The strands were drawn down from the air-cooled belt conveyor by gravity. The temperature difference between the melting peak temperature and the crystallization peak temperature in differential scanning calorimetry (DSC) was 54.76°C. These pellets were injection molded in the same manner as in Example 5. A cooling time of 30 seconds did not result in sufficient solidification when the mold was opened, and the test pieces adhered to the mold. Therefore, a mold release agent was applied between each shot. However, it was determined that a 30-second cooling time was not sufficient. Therefore, an extension to 120 seconds yielded similar results.

[0063] Therefore, while adjusting the holding pressure, samples were taken within the range that could be removed within a 50-second cooling time. After removal, the test pieces were left at room temperature and humidified for one week, and the test pieces were annealed at 130°C for three hours. The flexural modulus, flexural stress, and heat distortion temperature were measured. The results are shown in Table 2. The heat distortion temperature without annealing was a very low 80.8°C, and even with the annealing treatment, it was 195°C, which is lower than in Examples 4 and 5.

[0064] [Reference Examples] As reference examples for Examples 1 and 2, polybutylene terephthalate resin (PBT resin) was press-molded in the same manner as in Example 1, and the press moldability and heat resistance of the pressed sheet were evaluated. The sheet molded product was deformed when removed from the mold. The heat resistance evaluation of the obtained press-molded product at 220°C showed that it fell off 10 seconds after being set in the jig. The results of differential scanning calorimetry (DSC) are shown in Table 1, and showed that the melting temperature was lower than that of polyethylene terephthalate and the sheet could not withstand the heat resistance test.

[0065] As described above, the polyethylene terephthalate resin composition of the present invention has a fast crystallization rate, excellent moldability, and high heat resistance, making it completely different from conventional polyethylene terephthalates. Although polyethylene terephthalate has a high melting point, it is not widely used in industrial fields where heat resistance is required. This is due to its extremely slow crystallization rate, which makes it less suitable for injection molding, which is often used for industrial parts, and its low heat resistance. Polyester is widely used in textiles and water bottles, but in addition to horizontal expansion, upcycling of these materials is also required from a global environmental perspective. The value of using this invention is enhanced by the fact that raw materials can be procured from the abundant textile and bottle recycling markets.

Claims

1. A polyethylene terephthalate resin composition comprising 0.01 to 1.0 part by weight of fumed silica (B) and 0.01 to 2.0 part by weight of an organic carboxylic acid metal salt (C) based on 100 parts by weight of a polyethylene terephthalate resin (A).

2. A polyethylene terephthalate resin composition comprising 0.01 to 1.0 part by weight of fumed silica (B) and 0.1 to 2.0 parts by weight of bamboo charcoal (D) having an average particle diameter of 30 μm or less, and 0.01 to 2.0 part by weight of an organic carboxylic acid metal salt (C) based on 100 parts by weight of a polyethylene terephthalate resin (A).

3. The polyethylene terephthalate resin composition according to any one of claims 1 or 2, wherein the polyethylene terephthalate resin (A) is a recycled polyethylene terephthalate resin.

4. The polyethylene terephthalate resin composition according to any one of claims 1 or 2, wherein the organic carboxylic acid metal salt (C) is a benzoic acid metal salt and a stearic acid metal salt.

5. The polyethylene terephthalate resin composition according to claim 3, wherein the organic carboxylic acid metal salt (C) is a benzoic acid metal salt and a stearic acid metal salt.

6. A polyethylene terephthalate resin composition comprising 60 to 10 parts by weight of glass fiber based on 40 to 90 parts by weight of the resin composition according to any one of claims 1 or 2.

7. A polyethylene terephthalate resin composition comprising 60 to 10 parts by weight of glass fiber based on 40 to 90 parts by weight of the resin composition according to claim 3.

8. A polyethylene terephthalate resin composition having a difference between the crystallization peak temperature and the melting peak temperature in a differential scanning calorimeter of 45°C or less. The measurement conditions of the differential scanning calorimeter are as follows: under a nitrogen atmosphere, the polyethylene terephthalate resin is melted by heating at a heating rate of 10°C / min to 300°C, held for 5 minutes, then cooled to 70°C at a cooling rate of 10°C / min, and the crystallization peak temperature is determined from the crystallization exothermic curve. Next, after holding at 70°C for 5 minutes, the melting peak temperature is determined from the melting endothermic curve by heating at a heating rate of 10°C / min to 280°C. The polyethylene terephthalate resin composition according to any one of claims 1 or 2.

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