POLYETHYLENE TEREPHTHALATE RESIN MOLDING AND THE MANUFACTURING PROCESS THEREOF

Abstract: A polyethylene terephthalate resin molding characterized by the fact it is a molding molded from a polyethylene terephthalate resin composition containing a polyethylene terephthalate resin and fibrous filler, and the intrinsic viscosity of the molding measured at 25 DEG C as a 1 % solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1 exceeds 0.53.

Description: TITLE Polyethylene Terephthalate Resin Molding And The Manufacturing Process Thereof Field of the Invention The present invention relates to a polyethylene terephthalate resin molding which exhibits excellent mechanical characteristics and, at the same time, is superior in moldability, dimensional stability, appearance characteristics, heat resistance and weatherability; it also relates to the manufacturing process for the resin molding. To be precise, it relates to the moldings in which mechanical strength is particularly required, for example, polyethylene terephthalate moldings such as the moldings which have welded parts including the parts for wipers for wiping the window glasses of aiφlanes and vehicles like automobiles and electric cars; it also relates to their manufacturing process. Background Thermoplastic polyester resins, for example, polyethylene terephthalate and polybutylene terephthalate generally have excellent mechanical and electrical characteristics together with excellent characteristics in chemical resistance and heat resistance. The original characteristics of resins are further improved by adding additives like inorganic fillers to thermoplastic polyester resins for suitable applications as molding materials in wide application areas such as electrical insulation parts and automotive parts. Among the applications of such thermoplastic polyester resin compositions, the moldings that particularly require mechanical characteristics are the wipers of automobiles, electric cars and airplanes. Wipers have wiper blades and wiper arms. In the blade, the wiping part that contacts and wipes out the surface to be wiped, such as the glass surface, is formed in the longitudinal direction on the whole; at the same time, it has the body of blade in which the whole is molded to a solid molding with a resin material. The wiper blade is supported by the wiper arm. Furthermore, the base (head) that links with this arm is connected with the wiper motor through a multiple number of linking members. The wiper arm undertakes reciprocating motions as the motor is actuated, and with the motions the wiping part of the blade wipes out the surface to be wiped such as the glass surface. Particularly excellent mechanical characteristics are required for the moldings used for the wiper arm and the base (head) which supports it. Universally known is a method to add fibrous fillers such as glass fiber and carbon fiber to thermoplastic polyester resins for the purpose of improving mechanic characteristics. Nevertheless, when a large amount of fibrous fillers was added, there was a problem with impairment of moldability because of an increase in the viscosity of melted resin. Moreover, when the melt temperature was raised in order to compensate moldability, decomposition of the resin was accelerated and its molecular weight dropped. Thus, there was still a problem with inability to obtain the molding provided with the required mechanical characteristics. It is desirable to provide polyethylene terephthalate resin moldings represented by the moldings with welded parts including the parts for wipers of automobiles, electric cars and aiφlanes which have not only the significantly improved mechanical strength but also the intrinsic excellent moldability, dimensional stability, appearance characteristics, heat resistance and weatherability of the polyethylene terephthalate resin. It is also desirable to provide their manufacturing process. Summary of the Invention The present inventors investigated the correlation between intrinsic viscosities of moldings and mechanical characteristics in order to solve these problems. As a result, the present inventors uncovered that the moldings, such as parts for wipers, with intrinsic viscosities greater than a specific value had far more significantly improved mechanical characteristics than those of physical property test specimens with the same intrinsic viscosities as specified in ASTM. In one aspect, a molding is molded from a polyethylene terephthalate resin and fibrous filler, and it is characterized by the fact that the molding intrinsic viscosity measured at 25°C as a 1% solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1 exceeds 0.53. In another aspect, a molding is characterized by the fact that the above- mentioned polyethylene terephthalate resin composition contains 100 wt parts of a polyethylene terephthalate resin and 17 - 123 wt parts of fibrous filler. In yet another aspect, a molding is characterized by the fact that one of the above-mentioned polyethylene terephthalate resins is a resin the intrinsic viscosity of which exceeds 0.65 when measured at 25°C as a 1% solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1. In yet another aspect, a molding is characterized by the fact that one of the above-mentioned moldings is a molding provided with a welded part. In still yet another aspect, a molding is characterized by the fact that the above- mentioned molding provided with a welded part is a part for wipers. In yet another aspect, there is provided a manufacturing process for moldings comprising a polyethylene terephthalate resin composition, comprising (a) a process to prepare a polyethylene terephthalate resin composition by melt-kneading fibrous filler and a polyethylene terephthalate resin the intrinsic viscosity of which exceeds 0.65 when measured at 25°C as a 1% solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1; and (b) a process to use the aforementioned polyethylene terephthalate resin composition to mold a molding the intrinsic viscosity of which exceeds 0.53 when measured at 25°C as a 1% solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1. Brief Description of Drawings Figure 1 is a drawing to describe a test part for measuring the joint strength which is prepared by imagining a joint between the wiper arm and the base; it is also to describe the strength test method. Figure 2 is a drawing to describe a test part for measuring the joint strength which is prepared by imagining a joint between the wiper arm and the wiper blade; it is also to describe the strength test method. Detailed Description Of Preferred Embodiments The polyethylene terephthalate (henceforth called PET) used in the present invention includes a linear polyester obtained by condensation polymerization of an acid component with a glycol component in which used as the acid component is terephthalic acid or the ester-forming derivative thereof, and used as the glycol component is ethylene glycol; and a polyester in which part of the acid component and / or glycol component is substituted with a copolymerizable third monomer, for example, a teφolymer of terephthalic acid, ethylene glycol and a copolymerizable third monomer. Cited for the third monomer that can substitute an acid component are, for example, isophthalic acid, phthalic acid, naphthalenedicarboxylic acids, adipic acid, diphenyldicarboxylic acids and sebacic acid. Cited for the third monomer that can substitute the glycol component are propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol and bisphenols such as 2,2-bis(4- hydroxyphenyl) propane and bis (4-hydroxyphenyl) sulfonate, polyoxyalkylene glycols such as polyoxyethylene glycol, polyoxypropylene glycol and polyoxytetramethylene glycol, and oxyacids such as oxybenzoic acid and hydroxyethoxybenzoic acid. PET can be readily manufactured with the general method, for example, melt- condensation polymerization or a method to combine this method with solid phase condensation polymerization. Number average molecular weight of PET is 8000 - 50000, preferably 9000 - 45000, more preferably 10000 - 38000. The PET used in the present invention may be a PET that has any intrinsic viscosity as long as it can provide a molding the intrinsic viscosity of which exceeds 0.53 when measured at 25°C as a 1% solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1. This is because of the fact that, even if the PET with the same intrinsic viscosity is used, the intrinsic viscosity of the molding obtained varies depending on the monomer component of PET, compounding conditions of PET with other components, molding shapes and molding conditions of the molding actually used. However, it is preferable that the PET intrinsic viscosity exceed 0.65 when PET is disolved in a mixing solution of phenol and dichlorobenzene with the weight ratio of 1/1 to make a 1% solution and the solution viscosity is measured at 25°C; it is more preferable that the viscosity exceed 0.8. When a PET with such intrinsic viscosity is used to mold moldings such as parts for wipers under compounding conditions and molding conditions familiar to the industry concerned, the intrinsic viscosity of the resultant molding exceeds 0.53 when measured at 25°C as a 1% solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1. As to inorganic fillers used in the present invention, any universally known inorganic fillers can be employed. For instance, cited may be glass fiber, carbon fiber, potassium titanate, whisker, kaolin, talc and mica. The compounding ratio of inorganic fillers can be selected arbitrarily in accordance with the application of moldings such as desired mechanical characteristics and the molding shape. Generally, it is in the range of 17 - 123 wt, preferably 25 - 100 wt parts per 100 wt parts of PET. When the amount of fillers compounded is less than 17 wt parts, sufficient improvement in mechanical characteristics cannot be obtained. On the other hand, when the amount of fillers compounded exceeds 123 wt parts, the flow property of the melted composition obtained falls, causing poor moldability. Furthermore, in the case of parts for wipers such as the wiper arm, when the amount of fillers compounded is lower than 42 wt parts per 100 wt parts of PET the molding mechanical strength, particularly rigidity becomes insufficient; hence, 42 - 123 wt parts is preferable. For the puφose of improving other characteristics further, usual additives may be added to the composition used in the present invention within the range that does not impair the objective of the present invention. For instance, a flame retardant and flame retardant auxiliary may be added for the puφose of improving flame retardancy, and an antioxidant and heat stabilizer may be added for the puφose of improving heat resistance and preventing discoloration. Exemplified for other additives are a nucleating agent, lubricant, plasticizer, mold releasing agent, UV stabilizer, dye and pigment. The resin composition used in the present invention can be obtained usually by melt-blending PET, fillers and the above-mentioned additives optionally with a usual melt-mixer such as monoaxial or biaxial extruder, Banbury mixer, kneader or mixing roll. The entire or part of the components to be compounded may be supplied to the melt-mixer simultaneously or separately. The most general method is to dry-blend components in advance followed by melt-kneading with the above-mentioned melt- mixer to homogenize and forming pellets. The pellet-shaped resin composition thus prepared is usually kept in the sufficiently dried state and charged into the molding machine hopper for molding. The molding of the present invention has an intrinsic viscosity exceeding 0.53. The molding intrinsic viscosity is measured at 25°C by dissolving a sample taken from the actually molded molding in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1 to make a 1% solution. Suφrisingly, the molding with intrinsic viscosity exceeding 0.53 molded from the polyethylene terephthalate resin compositon of the present invention, especially the molding with a welded part such as the part for wipers, can be far more significantly improved in its mechanical characteristics than what is observed in the ASTM-specified dumbbell test specimen or flex test specimen that is molded from the same resin composition and has the same intrinsic viscosity. Based on the disclosure in the present specification such a molding can be readily molded with a usual method from the above-mentioned resin composition compounded with a proper compounding ratio of PET having a proper intrinsic viscosity to inorganic fillers with a common molding machine for thermoplastic resins under the molding conditions set up in accordance with the molding shape. The molding of the present invention minimizes losses in the intrinsic excellent characteristics of PET such as mechanical characteristics, heat resistance and electrical characteristics; provides excellent appearance characteristic and dimensional stability to moldings after the resin composition is molded; and, furthermore, significantly improves the molding mechanical characteristics. The present invention is able to expand the application of polyethylene terephthalate resin in the areas of automobiles, mechanical parts and electrical/electronic parts to the molding that requires improvement in strength reduction at the section where welding occurs because of molding, for example, the brake booster valve body and gear housing. Examples of Embodiment The present invention is described with the examples of embodiment in the following. The present invention, however, is not limited only to the present examples of embodiment. (Examples 1 - 5, Comparative Examples 1 - 2) Each component as shown in Table 1 was melt-kneaded with a biaxial extruder (ZSK-40 made by W&P Co.) and cooled with water to prepare pellets. The pellets obtained were molded with an (screw type) injection molding machine (JSW (Japan Seikosho K.K.)-made J100E II-P) under the conditions of mold temperature 120°C, resin temperature 280°C and molding cycle 45 sec to prepare test specimens as specified by the following testing methods. A sample taken from the test specimens obtained was dissolved in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1 to make a 1% solution, and its intrinsic viscosity was measured at 25°C as the intrinsic viscosity of the test specimen. Moreover, the test specimens obtained were used to measure stress-strain properties according to ASTM-D638, flexual modulus of elasticity and bending strength according to ASTM-790, and impact strength according to ASTM-D256. Subsequently, the pellets obtained were used to prepare test parts which structurally resembled the wiper arms shown in Figure 1 and Figure 2. A sample taken from the moldings of test parts obtained was dissolved in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1 to make a 1% solution, and the intrinsic viscosity was measured as the intrinsic viscosity of the molding. Moreover, the test part strength was measured with the following method. Measurement of Part Strength V The test part shown in Figure 1 is designed by imagining a joint between the wiper arm and the base (head) which supports the wiper arm and also is connected with the wiper motor through a multiple number of links. The test part shown in Figure 1 has a shape resembling the wiper arm, and comprises molding 1 provided with rotating axis 5 and aluminum-made base 7. Molding 1 with a shape resembling the wiper arm is 150 - 500 mm in outside dimensional length (L), 20 - 40 mm in width (W), 15 - 40 mm in height (H) and 1.5 - 5 mm in thickness (T); it has a groove-shaped cross section and a structure that is provided with a pair of side wall 3 which are connected with upper wall 2 and crossing beams (not shown in the figure) formed inside, and rotating axis 5 having a diameter of 7 - 11 mm between side wall 3. Base 7 has hinge shape 6 which receives rotating axis 5, freely rotates by hinge shape 6 and rotating axis 5 between a pair of side wall 3 in the direction peφendicular to the length (L) direction and is linked with molding 1. After base 7 was fixed with a jack, a load was applied on terminal 4 opposite to the terminal having the base of molding 1 in the direction peφendicular to the axis direction of the test part, and also peφendicular to the rotating surface. Then, load F 1 (N) at the time of rupture was measured. Load F 1 is the rupture strength of the joint between molding 1 resembling the wiper arm shape and aluminum-made base 7. Meaurement of Part Strength H The test part shown in Figure 2 is designed by imagining a joint between the wiper arm and the wiper blade mounted on the tip of the wiper arm. The test part shown in Figure 2 comprises molding 1 resembling the wiper arm shape and aluminum-made joint member 10. Molding 1 resembling the wiper arm shape is 150 - 500 mm in outside dimension length (L), 20 - 40 mm in width (W), 15 - 40 mm in height (H) and 1.5 - 5 mm in thickness (T); it has a groove-shaped cross section and a pair of side wall 3 which are connected with upper wall 2 and crossing beams (not shown in the figure) formed inside, and the tip of a pair of side wall 3 has hole 8 of 5 mm in diameter. Joint member 10 has protrusion 9 on the tip of its both sides. Joint member 10 is installed between a pair of side wall 3 of molding 1 so as to insert protrusion 9 into hole 8. After terminal 11 of molding 1 was fixed with a jack, a load was applied on joint member 10 in the direction peφendicular to the axis direction of the test part and also parallel to the rotating surface, and load F2 (N) at the time of rupture was measured. Load F2 is the rupture strength of a joint between molding 1 resembling the wiper arm shape and aluminum-made joint member 10. Moreover, in the present examples and comparative examples, the dimension of molding 1 resembling the wiper arm shape was 200 mm in L, 30 mm in W, 30 mm in H and 4 mm in T for both the test part shown in Figure 1 and the test part shown in Figure 2, and the diameter of rotating axis 5 of the test part shown in Figure 1 was 8.5 mm. Each test result of the above-mentioned is shown in Table 1. Moreover, each component in the table is shown in the following. PET: Polyethylene terephthalate from terephthalic acid and ethylene glycol the intrinsic viscosity of which is 0.87 when measured at 25°C as a 1% solution in a mixed solution of phenol and dichlorobenzene with the weight ratio of 1/1. Antioxidant: Inganox 1010 (Trade name) made by Ciba Geigy Co. Glass fiber: Chopped glass fiber PPG 3563 (Trade name) made by PPG Co. Plasticizer: Lionon DEH 40 (Trade name) made by Lion K.K. Nucleating agent: Jet Talc FFR (Trade name) made by Asada Seifun K.K. Table 1 It can be seen from Table 1 that, when the test specimen intrinsic viscosity is high, elongation and impact strength are improved; moreover, when the molding intrinsic viscosity is high the strength of the part is improved. However, the effect of intrinsic viscosity varies greatly from a test specimen to a molding. When Comparative Example 1 in which the test specimen intrinsic viscosity is 0.48 is compared with Example 5 in which the viscosity is 0.72, the degree of improvement in the test specimen is only 32% for elongation and 26% for the notched Izod impact value. As opposed to this, when the degree of improvement in the molding with a structure resembling the wiper arm was compared similarly between Comparative Example 1 and Example 5, it was confirmed that part strength V improved 38% and part strength H as high as 133%. It is evident from the present example that, when the molding intrinsic viscosity is increased from 0.53, the polyethylene terephthalate resin molding becomes superior particularly in mechanical strength in the molding resembling the wiper arm. Furthermore, it can be seen that the improvement in strength of this extent in moldings is generally a remarkable improvement that is not confirmed with dumbell test specimens and bending test specimens described in ASTM which are used for measurements of general physical properties. Therefore, it can be stated that the effect of the intrinsic viscosity of a molding, particularly a molding provided with a welded part, on mechanical characteristics of the molding, especially on strength is a very difficult phenomenon to predict. By adopting a specific intrinsic viscosity for the molding the present invention minimizes losses in the intrinsic excellent characteristics of polyethylene terephthalate resin, such as mechanical characteristics, heat resistance and electrical characteristics; provides excellent appearance characteristics and dimensional stability to the molding after the resin composition is molded; and, furthermore, can provide the molding with significantly improved mechanical characteristics. The present invention is able to expand the application of polyethylene terephthalate resin in the areas of automobiles, mechanical parts and electrical/electronic parts to the molding that requires improvement in strength reduction at the welded section, such as the part for wipers.

Claims: CLAIMS 1. A molding made from a composition comprising polyethylene terephthalate and fibrous filler, said molding having an intrinsic viscosity greater than 0.53 when measured at 25 °C as a 1% solution in a mixed solution of phenol and dichlorobenzene having a weight ratio of 1/1. 2. A molding according to Claim 1, wherein said molding comprises a part for a wiper. 3. A process for improving the strength of a molded article comprising: selecting a composition comprising fibrous filler and polyethylene terephthalate having an intrinsic viscosity greater than 0.65 when measured at 25 °C as a 1% solution in a mixed solution of phenol and dichlorobenzene having a weight ratio of 1/1 ; and forming a molded article from the composition, the molded article having an intrinsic viscosity greater than 0.53 when measured at 25 °C as a 1% solution in a mixed solution of phenol and dichlorobenzene having a weight ratio of 1/1. 4. The process of Claim 3, wherein said molded article comprises a part for a wiper.

Inventors: KOBAYASHI TOSHIKAZU, NAITOH SEIJI, KOBAYASHI, TOSHIKAZU, NAITOH, SEIJI
Applicants: DU PONT, KOBAYASHI TOSHIKAZU, NAITOH SEIJI, E.I. DU PONT DE NEMOURS AND COMPANY, KOBAYASHI, TOSHIKAZU, NAITOH, SEIJI
Application year: 2000
Main classification: C08K7
IPC codes: B60S1, C08G63, C08J5, C08K7, C08L67