阅读说明：本技术 热塑性共聚物组合物和使用其制造的模制品 (Thermoplastic copolymer composition and molded article manufactured using the same ) 是由 崔盛闻 安炯玟 金奎怜 徐茂松 金正祐 郭旻瀚 金大喆 于 2020-08-03 设计创作，主要内容包括：本发明提供一种热塑性共聚物组合物,其能够改善低噪音性能而机械性能不劣化,所述组合物用于制造模制品,例如用作汽车部件的等速万向节保护罩。本发明的组合物包含：聚酯弹性体；包含二氧化硅和由化学式1表示的硅氧烷类聚合物的添加剂；和聚丁二醇。根据本发明,基于100重量份的所述聚酯弹性体,所述添加剂的含量为1重量份至4重量份,并且基于100重量份的所述聚酯弹性体,所述聚丁二醇的含量为3重量份至10重量份。(The present invention provides a thermoplastic copolymer composition capable of improving low noise properties without deterioration of mechanical properties, which is used for manufacturing molded articles, such as constant velocity joint boots used as automobile parts. The composition of the present invention comprises: a polyester elastomer; an additive comprising silica and a siloxane-based polymer represented by chemical formula 1; and polybutylene glycol. According to the present invention, the additive is contained in an amount of 1 to 4 parts by weight based on 100 parts by weight of the polyester elastomer, and the polybutylene glycol is contained in an amount of 3 to 10 parts by weight based on 100 parts by weight of the polyester elastomer.)

1. A thermoplastic copolymer composition comprising:

a polyester elastomer;

polybutylene glycol; and

an additive comprising silica and a siloxane-based polymer represented by chemical formula 1,

wherein the content of the additive is 1 to 4 parts by weight based on 100 parts by weight of the polyester elastomer:

[ chemical formula 1]

Wherein R is₁To R₈Each independently is an alkyl group having 1 to 10 carbon atoms, and n is an integer of 100 to 10,000.

2. The thermoplastic copolymer composition of claim 1, wherein the polyester elastomer is present in an amount of 80 to 95 weight percent, based on the total weight of the thermoplastic copolymer composition.

3. The thermoplastic copolymer composition of claim 1, wherein the polybutylene glycol is present in an amount of 3 to 8 parts by weight, based on 100 parts by weight of the polyester elastomer.

4. The thermoplastic copolymer composition according to claim 1, wherein the content of the siloxane-based polymer represented by chemical formula 1 in the additive is 1 to 4 parts by weight based on 1 part by weight of the silica.

5. The thermoplastic copolymer composition of claim 1, wherein the weight average molecular weight of the polytetramethylene glycol is from 2,000 to 5,000 g/mol.

6. The thermoplastic copolymer composition of claim 1, wherein the silica is fumed silica.

7. The thermoplastic copolymer composition of claim 1, further comprising a polyalkylene terephthalate.

8. The thermoplastic copolymer composition of claim 7, wherein the polyalkylene terephthalate is polybutylene terephthalate.

9. The thermoplastic copolymer composition of claim 7, wherein the polyalkylene terephthalate is present in an amount of 3 to 8 parts by weight, based on 100 parts by weight of the polyester elastomer.

10. The thermoplastic copolymer composition of claim 1, wherein the polyester elastomer is obtained by polycondensing a polyester with a polyether.

11. The thermoplastic copolymer composition of claim 10, wherein the polyester is polyethylene terephthalate (PET), poly (1, 3-trimethylene terephthalate) (PTT), polybutylene terephthalate (PBT), or combinations or copolymers thereof.

12. The thermoplastic copolymer composition of claim 10, wherein the polyether is Polyethylene Ether Glycol (PEG), polypropylene ether glycol (PPG), polytetramethylene glycol (PTMG), polytetramethylene ether glycol (PTMEG), or combinations or copolymers thereof.

13. The thermoplastic copolymer composition according to claim 1, wherein the melt flow index of the thermoplastic copolymer composition is 18g/10min or less when the melt flow index is measured under conditions of 230 ℃ and 10kg according to ISO1133, and the number of cycles at which noise of 75dB or more is generated is 34 or more when the number of cycles at which noise of 75dB or more is generated is measured under conditions at which the bending angle of a test specimen is 40 ° using a noise meter.

14. The thermoplastic copolymer composition of claim 1, wherein the thermoplastic copolymer composition exhibits a gloss reduction of 70% or more when comparing the gloss measured under the condition of a 60 ° reflection angle after being left at room temperature for one week after injection with the gloss measured under the condition of a 60 ° reflection angle immediately after injection.

15. A molded article comprising the thermoplastic copolymer composition of any one of claims 1 to 14.

16. The molded article of claim 15, wherein the molded article is a constant velocity joint boot.

Technical Field

[ Cross-reference to related applications ]

This application claims priority from korean patent application No.10-2019-0099672 filed at 14.08.2019 and korean patent application No.10-2020-0095350 filed again at 30.07.2020 at the korean intellectual property office, the disclosures of each of which are incorporated herein by reference.

The present invention relates to a thermoplastic copolymer composition, and more particularly, to a thermoplastic copolymer composition capable of providing a noise reduction effect, which is used to manufacture molded articles such as constant velocity joint boot (constant velocity joint boot).

Background

The constant velocity joint is a vehicle component mounted between a transmission and tires, and functions to uniformly transmit power generated by an engine to the tires through the transmission so that the two tires rotate at an equal speed.

Such constant velocity joints are coated with an excessive amount of grease serving as a lubricant, and are covered with a rubber boot to prevent the grease from leaking out. That is, the boot for the constant velocity joint is used to protect the constant velocity joint and grease from foreign matter. Generally, the protective cover is manufactured by extrusion molding of rubber or polyester resin.

Meanwhile, when power is transmitted to the tire through the constant velocity joint while the constant velocity joint rotates, noise may be generated due to friction between surfaces of the corrugations formed in the boot. At this time, if the bottom of the automobile is contaminated by foreign substances such as water, brine, or sand, noise generated due to friction between the surfaces of the corrugations inside the protective cover is further increased, generating loud noise of 90dB or more. Therefore, when manufacturing the protective cover, various lubricants are added to reduce noise.

Amide-based, montan-based, or olefin-based monomer waxes are often used as lubricants, but these components are poorly compatible with polyester elastomers as the main component of the boot. Therefore, when a small amount of wax is added, the lubricating effect may not be significant. On the other hand, when an excessive amount of wax is added, surface defects, deterioration of mechanical properties, and the like may be caused due to the migration phenomenon.

Therefore, an attempt has been made to reduce noise generation due to friction or contamination by adding an organic substance such as polyalkylene glycol, but even in this case, noise generation cannot be effectively reduced.

Therefore, it is required to develop a material capable of effectively reducing noise generated in the constant velocity joint boot.

[ related art documents ]

[ patent document ] (patent document 0001) JP 1997 177971A

Disclosure of Invention

Technical problem

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to improve the surface properties of a constant velocity joint boot in terms of uniformity without deterioration of mechanical properties, thereby effectively improving the noise reduction performance and the sound insulation performance of the constant velocity joint boot.

It is another object of the present invention to provide a thermoplastic copolymer composition capable of improving low noise properties without deterioration of mechanical properties, which is used for manufacturing molded articles such as constant velocity joint boots.

Technical scheme

According to one aspect of the present invention, there is provided a thermoplastic copolymer composition comprising: a polyester elastomer; polybutylene glycol; and comprising silicon dioxide (SiO)₂) And an additive of a siloxane-based polymer represented by chemical formula 1, wherein the content of the polytetramethylene glycol is 3 to 8 parts by weight based on 100 parts by weight of the polyester elastomer, and the content of the additive is 1 to 4 parts by weight based on 100 parts by weight of the polyester elastomer:

[ chemical formula 1]

Wherein R is₁To R₈Each independently is an alkyl group having 1 to 10 carbon atoms, and n is an integer of 100 to 10,000.

According to another aspect of the present invention, there is provided a molded article manufactured using the thermoplastic copolymer composition.

Advantageous effects

The thermoplastic copolymer composition according to the present invention comprises, as a main component, a polyester elastomer and a polybutylene glycol having excellent compatibility with the polyester elastomer. Therefore, when a molded article is manufactured using the composition according to the present invention, the soft property of the molded article can be enhanced, thereby minimizing the generation of noise due to mechanical friction. In addition, since the composition of the present invention includes silicon dioxide (SiO) for increasing the exudation rate of polytetramethylene glycol₂) And additives for siloxane-based polymers, thus in molded articlesFor example, in the constant velocity joint boot, noise due to friction or contamination can be effectively reduced.

Furthermore, since the composition of the present invention further comprises a polyalkylene terephthalate, when the composition of the present invention is used to manufacture a molded article particularly requiring hardness and tensile strength, such as a constant velocity joint boot, the mechanical properties of the molded article can be improved.

Drawings

Fig. 1 includes images showing the surface condition of test specimens manufactured using the thermoplastic copolymer compositions according to examples 1 and 2 of the present invention or the thermoplastic copolymer compositions according to comparative examples 2 and 3 after the test specimens were left for 1 week;

fig. 2 shows a state in which the hollow molded article was mounted on a noise meter at a bending angle of 40 ° to measure the number of cycles of generating noise of 75dB or more.

Detailed Description

The terms and words used in the present specification and the appended claims should not be construed as limited to general or dictionary meanings, but should be construed to have meanings and concepts matching the technical spirit of the present invention in order to describe the present invention in the best way.

Hereinafter, the present invention will be described in more detail to help understanding the present invention.

The thermoplastic copolymer composition according to one embodiment of the present invention comprises: a polyester elastomer (a); polybutylene glycol (b); and comprising silicon dioxide (SiO)₂) And an additive (c) of a siloxane-based polymer.

In the thermoplastic copolymer composition of the present invention, the polyester elastomer (a) has advantages of both a thermoplastic resin excellent in moldability and a rubber excellent in flexibility and elastic recovery ability, and thus can be used as a material for parts of automobiles, for example, constant velocity joint boots. In the technical field of the present invention, the polyester elastomer (a) may be referred to as a thermoplastic polyester elastomer (TPEE).

The polyester elastomer can be obtained by polycondensing polyester and polyether. Polyesters are units that constitute the hard segments of the elastomer and may be derived from aromatic dicarboxylic acids and aliphatic diols. For example, the polyester may include polyethylene terephthalate (PET), poly (1, 3-trimethylene terephthalate) (PTT), polybutylene terephthalate (PBT), or combinations or copolymers thereof. In addition, the polyether is a unit constituting a soft segment of the elastomer, and may include, for example, Polyethylene Ether Glycol (PEG), polypropylene ether glycol (PPG), polytetramethylene glycol (PTMG), polytetramethylene ether glycol (PTMEG), or a combination thereof or a copolymer thereof.

The polyester elastomer is the main component of the thermoplastic copolymer composition of the present invention and may be contained in an amount of 80 to 99% by weight, for example, 90 to 98% by weight, based on the total weight of the polyester elastomer (a), the polytetramethylene glycol (b) and the additive (c).

The polyester elastomer may be present in an amount of 80 to 95 wt%, preferably 85 to 95 wt%, more preferably 85 to 90 wt%, based on the total weight of the thermoplastic copolymer composition. Within this range, the balance of physical properties and hardness may be excellent.

Unless otherwise defined in the specification, the total weight of the thermoplastic copolymer composition refers to the sum of the weights of all components contained in the thermoplastic copolymer composition.

The thermoplastic copolymer composition of the present invention may comprise polytetramethylene glycol (PTMG) (b). The polytetramethylene glycol is a component that imparts a soft property to a molded article manufactured using a composition comprising a polyester elastomer, and is used to minimize noise generation due to mechanical friction in the molded article. Specifically, the polytetramethylene glycol has excellent compatibility with the polyester elastomer, and thus can be uniformly dispersed in the polyester elastomer resin. In this case, as time goes by, the polytetramethylene glycol uniformly dispersed in the polyester elastomer resin slowly leaks to the surface of the molded article (resin). Meanwhile, a constant velocity joint boot is mounted on a drive shaft of a vehicle to protect the constant velocity joint from the external environment and to prevent grease from being exposed to the outside when rotating. In the case of the conventional constant velocity joint boot, surface friction is continuously generated during rotational movement, resulting in occurrence of surface damage. However, according to the present invention, the leaked polytetramethylene glycol can reduce the surface friction of the polyester elastomer molded article, thereby preventing damage to the constant velocity joint boot and reducing noise generation.

The content of the polybutylene glycol may be 3 parts by weight to 8 parts by weight, specifically 3 parts by weight to 5 parts by weight, based on 100 parts by weight of the polyester elastomer. That is, in order to reduce surface friction of a molded article manufactured using the thermoplastic copolymer composition and to apply the molded article to a constant velocity joint boot, it is necessary to contain 3 parts by weight or more of polytetramethylene glycol. In this case, noise reduction performance (sound insulation performance) can be achieved. In addition, in order to prevent deterioration of mechanical properties of the molded article and deterioration of moldability due to excessive bleeding, the content of the polytetramethylene glycol may be 8 parts by weight or less.

In one embodiment of the invention, the Weight Average Molecular Weight (WAMW) of the polytetramethylene glycol can be from 2,000g/mol to 5,000g/mol, specifically from 2,500g/mol to 3,500 g/mol. Within this range, the surface bleeding rate can be easily controlled. Specifically, when the molecular weight exceeds 2,000g/mol, the bleeding rate is significantly increased, thereby preventing mold contamination and defects during molding. When the molecular weight is 5,000g/mol or less, the bleeding rate of the polytetramethylene glycol is prevented from being significantly reduced. When the bleeding rate is significantly reduced, the polytetramethylene glycol cannot sufficiently leak to the surface of the molded article, making it difficult to achieve the purpose of reducing the surface friction.

Unless otherwise defined in the present specification, the weight average molecular weight can be measured by gel permeation chromatography (GPC, Waters Breeze). As a specific example, Gel Permeation Chromatography (GPC) may be performed using an eluent prepared by mixing chloroform and chlorophenol in a volume ratio of 10:1 (chloroform: chlorophenol), and the measured value may be calculated as a relative value based on the value of a Polystyrene Standard (PS) sample.

Further, in the thermoplastic copolymer composition of the present invention, Silica (SiO) is contained₂) And the additive (c) of the siloxane-based polymer can increase the bleeding rate of the polytetramethylene glycol, thereby improving the use of heatDuctility of molded articles made from the plastic copolymer composition. For example, when the molded article is applied to a constant velocity joint boot, noise reduction performance can be maximized.

More specifically, the siloxane-based polymer may be Polydimethylsiloxane (PDMS) having a chemical structure represented by the following chemical formula 1.

[ chemical formula 1]

In chemical formula 1, R₁To R₈Each independently is an alkyl group having 1 to 10 carbon atoms, and n is an integer of 100 to 10,000.

In chemical formula 1, R₁To R₈Preferably each independently an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. In this case, the noise reduction performance may be excellent.

In addition, in chemical formula 1, n is preferably an integer of 500 to 10,000, more preferably an integer of 1,000 to 10,000, still more preferably an integer of 5,000 to 10,000, and most preferably an integer of 5,000 to 7,500. Within this range, the noise reduction performance may be excellent.

When the siloxane-based polymer is contained in the composition containing the polyester elastomer, in a molded article manufactured using the composition, the polytetramethylene glycol may leak uniformly, and the bleeding rate of the polytetramethylene glycol may increase. That is, in order to increase the bleeding rate of the polytetramethylene glycol, for example, a method of decreasing the molecular weight of the polytetramethylene glycol to be added may be used. In this case, however, as described above, problems associated with workability, such as mold contamination and defects, may occur during molding, and bleeding of the polytetramethylene glycol in the molded article may not even be achieved. When a siloxane-based polymer having excellent compatibility with a polyester elastomer is added to a composition, uniform and rapid bleeding of polytetramethylene glycol can be achieved in a molded article manufactured using the composition.

In addition, the additive (c) may further comprise twoSilicon oxide (SiO)₂)。

For example, the silica may be fumed silica (fumed silica). The silicone-based polymer contained in the additive (c) exists as a liquid polymer at room temperature. Therefore, in terms of storage, transportation, and ease of incorporation into the composition, it is preferable that the siloxane-based polymer and silica are prepared in a particulate form and added to the composition. In this case, the silicone-based polymer and silica can be uniformly dispersed in the polyester elastomer composition. In addition, the fumed silica may contain a high molecular weight chain structure. In this case, entanglement between several polymers in the composition can be caused, thereby improving the mechanical properties of the composition and molded articles produced using the composition.

The content of the additive (c) containing silica and a siloxane-based polymer, which can exert the above-described functions, may be 1 to 4 parts by weight, specifically 1.5 to 3.0 parts by weight, based on 100 parts by weight of the polyester elastomer. The content of the additive may be 1 part by weight or more in order to achieve the intended effect of the additive. In particular, in order to prevent the decrease in hardness and the peeling, the content of the additive may be 4 parts by weight or less.

In one embodiment of the present invention, in the additive (c) comprising silica and a siloxane-based polymer, the content of the siloxane-based polymer may be 1 to 4 parts by weight, specifically 1.5 to 3.0 parts by weight, based on 1 part by weight of silica. When the content of the silicone-based polymer exceeds 1 part by weight based on 1 part by weight of the silica, the bleeding rate of the polytetramethylene glycol increases. Meanwhile, in order to prevent the reduction of durability due to the reduction of hardness of the molded article, the siloxane-based polymer may be used in an amount of 4 parts by weight or less based on 1 part by weight of silica.

In addition, the thermoplastic copolymer composition of the present invention may further comprise a polyalkylene terephthalate, for example, polybutylene terephthalate (PBT), in order to improve mechanical properties, such as hardness, of the molded article. In the case of a molded article manufactured using a thermoplastic copolymer composition further comprising a polyalkylene terephthalate, it is possible to prevent a decrease in hardness, thereby improving durability. Thereby, mechanical damage to the surface of the molded article can be minimized. Therefore, when the molded article is used as a constant velocity joint boot, noise reduction performance can be improved.

The content of the polyalkylene terephthalate may be 3 to 8 parts by weight, specifically 3 to 5 parts by weight, based on 100 parts by weight of the polyester elastomer.

When the polyalkylene terephthalate is used in an amount of less than 3 parts by weight, based on 100 parts by weight of the polyester elastomer, the hardness-improving effect may not be significant. When the amount of the polyalkylene terephthalate exceeds 8 parts by weight, the hardness is excessively increased, resulting in a decrease in the elasticity of the molded article. As a result, noise reduction performance (sound insulation performance) may be reduced.

Further, the thermoplastic copolymer composition of the present invention may additionally comprise various additives such as a compatibilizer, an ionomer, a heat stabilizer, a light stabilizer, a lubricant, and a carbon black pigment, as required.

The compatibilizer is a chain extender and is used to adjust the viscosity of the polymer composition. For example, the compatibilizer may include a glycidyl-modified ethylene-octene copolymer (EOR-GMA). The glycidyl-modified ethylene-octene copolymer may be an ethylene-octene copolymer graft-modified with glycidyl methacrylate. In this case, the graft content of glycidyl methacrylate is 8 to 20% by weight.

In addition, ionomers are used to increase melt tension (improve product formability) and chemical resistance and enhance abrasion resistance, and may include, for example, Surlyn 8920(Dupont Co.), which is a sodium-based ionomer.

The thermal stabilizer is used to inhibit or prevent thermal decomposition of the thermoplastic copolymer composition when the composition is mixed or molded at high temperatures. For example, the heat stabilizer may include amine, phenol, or phosphite based heat stabilizers without limitation.

As the light stabilizer, an ultraviolet absorber or a Hindered Amine Light Stabilizer (HALS) which suppresses decomposition by exposure to ultraviolet rays can be used. The ultraviolet absorber may include a hydroxybenzophenone-based or benzotriazole-based ultraviolet absorber without being limited thereto. In addition, the hindered amine light stabilizer may include a mixture of bis (1,2,2,6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6, 6-pentamethyl-4-piperidyl sebacate without being limited thereto.

Lubricants may include amides, montan waxes, and olefinic monomeric waxes.

Each of various additives may be used in a content range not to impair the inherent physical properties of the thermoplastic copolymer composition of the present invention, and, for example, may be used in an amount of 0.1 to 5% by weight or 0.1 to 3% by weight, based on the total weight of the composition.

The thermoplastic copolymer composition of the present invention can be prepared by mixing the above-mentioned components by heating and melting, and can be pelletized. In this case, the melt mixing temperature may be appropriately determined in consideration of the melting point of the polyester elastomer. For example, melt mixing can be performed at 200 ℃ to 300 ℃, specifically at 200 ℃ to 270 ℃.

The thermoplastic copolymer preferably has a melt flow index (g/10min) of 18g/10min or less, more preferably 17g/10min or less, still more preferably 16g/10min or less, when measured according to ISO1133 (conditions of 230 ℃ and 10 kg). As a specific example, the thermoplastic copolymer has a melt flow index of from 5g/10min to 18g/10min, preferably from 10g/10min to 18g/10min, more preferably from 12g/10min to 18g/10min, still more preferably from 14g/10min to 17g/10min, and most preferably from 15g/10min to 16g/10 min. Within the range, injection molding properties may be excellent.

The hardness (shore D) of the thermoplastic copolymer is preferably 33 or more when measured according to ISO 868. As a specific example, the thermoplastic copolymer has a hardness of 33 to 40, preferably 33 to 38, more preferably 33 to 37. Within the range, the balance of hardness properties and physical properties may be excellent.

When the tensile strength (MPa) is measured according to ISO527, the tensile strength of the thermoplastic copolymer is preferably 15MPa or more. As a specific example, the thermoplastic copolymer has a tensile strength of 15MPa to 25MPa, preferably 15MPa to 20MPa, more preferably 15MPa to 16 MPa. Within the range, the balance of strength and physical properties may be excellent.

When the tensile elongation (%) is measured according to ISO527, the tensile elongation of the thermoplastic copolymer is preferably 260% or more, more preferably 270% or more, and still more preferably 277% or more. As a specific example, the thermoplastic copolymer has a tensile elongation of 260% to 290%, preferably 270% to 290%, more preferably 275% to 285%, and still more preferably 275% to 280%. Within the range, the balance of mechanical properties and physical properties may be excellent.

When the number of cycles of generating noise of 75dB or more is measured using a noise meter under the condition that the bending angle of the sample is 40 °, the number of cycles of generating noise of 75dB or more in the thermoplastic copolymer is preferably 34 or more, more preferably 38 or more, still more preferably 41 or more, and most preferably 42 or more. As a specific example, the number of cycles in the thermoplastic copolymer is 34 to 45. Within the range, the balance of noise reduction effect and physical properties may be excellent.

When the friction coefficient is measured while moving a 10kg ball tip by 30mm on a 100X 2mm square specimen, the friction coefficient of the thermoplastic copolymer is 0.05 or less, more preferably 0.045 or less, still more preferably 0.042 or less, and most preferably 0.040 or less. Within the range, the noise reduction effect may be excellent.

When the gloss is measured at a reflection angle of 60 ° after being left at room temperature for one week after injection, the gloss of the thermoplastic copolymer is 5 or less, more preferably 3 or less, and still more preferably 1 or less. Within this range, the noise reduction performance may be excellent.

When the gloss measured under the condition of a reflection angle of 60 ° after leaving at room temperature for one week after injection is compared with the gloss measured immediately after injection, the gloss reduction rate of the thermoplastic copolymer is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. Within this range, the noise reduction performance may be excellent.

The thermoplastic copolymer composition of the present invention described above can be used to produce molded articles such as constant velocity joint boots by extrusion molding. In this case, the molded article may have improved softness while maintaining mechanical properties, thereby reducing noise generated due to friction, contamination, etc. during rotation.

Accordingly, the present invention additionally provides a molded article manufactured using the thermoplastic copolymer composition.

In addition, the number of cycles at which noise of 75dB or more is generated in the molded article is measured in the following manner.

(1) After the molded article was mounted to a noise meter at a bending angle of 40 °, it was rotated at 150 rpm. The mounted state is shown in fig. 2. At this time, the measurement was performed under the condition that noise of 75dB or less was generated at room temperature.

(2) 25g of a steel stock containing 15% by weight of calcium chloride (CaCl)₂) And 15% by weight of calcium hydroxide (Ca (OH)₂) The aqueous solution of (3) was sprayed for 30 seconds.

(3) 10g of sand having a particle size of 0.8mm to 1.2mm was dropped for 10 seconds.

(4) Idling was performed for 60 seconds.

(5) Repeating the processes (2) to (4).

(6) Performing the above process once corresponds to one cycle, and one cycle takes 100 seconds in total.

When noise of 75dB or more is generated in any one cycle, the rotation is maintained, and when the noise lasts for 3 minutes or more, the cumulative number of cycles is regarded as the number of cycles in which noise of 75dB or more is generated, and recording is performed.

The present invention may include a constant velocity joint boot for an automobile, wherein the number of cycles at which noise of 75dB or more is generated is preferably 40 to 80 when measured in the above manner.

Hereinafter, the present invention will be described in more detail with reference to the following preferred examples. However, these examples are provided for illustrative purposes only, and should not be construed as limiting the scope and spirit of the present invention. In addition, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Examples 1 to 4 and comparative examples 1 to 7

The compositions of the components shown in the following table 1 were melted and mixed at 230 ℃ using a twin-screw extruder and pelletized to prepare thermoplastic copolymer resin compositions. Here, the compositions of the components used in examples and comparative examples are as follows.

First, a polyester elastomer is prepared by polycondensing polybutylene terephthalate and polybutylene glycol. In this case, the melt flow index was 20g/10min (230 ℃, 2.13kg) and polytetramethylene glycol (PTMG) (K-PTG, BASF Co.) having a weight average molecular weight of 3,000g/mol was used.

Further, to prepare the additive (c), 2.34 parts by weight of Polydimethylsiloxane (PDMS), as a siloxane-based polymer having a chemical structure represented by chemical formula 1, in which n is 6,000, and 1 part by weight of fumed silica (geniopast Pellets, Wacker Co.) were mixed into particles and compounded.

KT-20(Shenyang Ketong Plastic Co.) was used as a compatibilizer and Surlyn 8920(DuPont Co.) was used as an ionomer. In addition, a mixture prepared by mixing 0.5 wt% of Naugard 445 and 0.5 wt% of Songnox 1010 was used as a heat stabilizer, 0.2 wt% of Chimassorb 944 was used as a light stabilizer, and a mixture prepared by mixing 0.3 wt% of OP WAX and 0.3 wt% of LC104N was used as a lubricant. Carbon black EC300J was used as the carbon black pigment.

The prepared composition was vacuum-dried at 85 ℃ for 4.5 hours, and then injection-molded at 230 ℃ to prepare a 100mm × 100mm × 2T square plate specimen for measuring tensile strength, tensile elongation, hardness, and the like. Hollow molded articles for measuring the number of cycles generating noise of 75dB or more were prepared.

Experimental example 1

Physical properties of the thermoplastic copolymer composition samples manufactured in examples 1 to 4 and comparative examples 1 to 7 were measured according to the following methods, and the results are shown in the following tables 1 and 2.

1) Melt flow index (g/10 min): the melt flow index of the test specimens was measured according to the ISO1133 test standard (at 230 ℃ C. and 10 kg).

2) Hardness (shore D): the Shore D hardness of the test specimens was measured according to the ISO868 test standard.

3) Tensile strength (MPa) and tensile elongation (%): tensile strength (MPa) and tensile elongation (%) of the test specimens were measured according to ISO 527-2-5A test standard.

4) Number of noise generation cycles: the number of cycles at which the molded article generates noise of 75dB or more was measured.

[ Table 1]

[ Table 2]

Referring to tables 1 and 2, in the case of examples 1 to 4 of the present invention, which relate to molded articles manufactured using a thermoplastic copolymer composition comprising polytetramethylene glycol and an additive comprising a siloxane-based polymer and silica, the number of noise generation cycles (the number of cycles for noise lasting 3 minutes or more) was 35 to 42, exhibiting excellent performance in terms of noise generation. That is, due to the presence of the additive containing the siloxane-based polymer and silica, the bleeding rate of the polytetramethylene glycol increases, which imparts ductility (smoothness) to the surface of the molded article. As a result, the noise reduction performance of the molded article is improved. On the other hand, in the case of the molded article (comparative example 1) manufactured using the composition not containing polytetramethylene glycol, the noise lasted for 3 minutes or more in the second cycle, indicating that the molded article did not exhibit the noise reduction effect. In addition, in the case of the molded article (comparative example 2) manufactured using the composition containing the polytetramethylene glycol but not containing the additive of the siloxane-based polymer and the silica, the number of noise generation cycles was 17, and a noise reduction effect was not exhibited as compared with the examples. These results show that the bleeding rate of the polytetramethylene glycol is further increased due to the presence of the additive comprising a siloxane-based polymer and silica, which is effective in reducing the surface friction of the molded article.

Meanwhile, in the case of examples 1 and 2 and comparative examples 3 to 5, when a certain amount of polybutylene terephthalate (PBT) was added, the number of noise generation cycles of the molded article was slightly reduced, and the hardness property of the molded article was improved. However, when an excess of PBT is added, the hardness and melt flow index are adversely affected.

In the case of comparative example 6, when a small amount, for example, 0.5 parts by weight of an additive comprising a siloxane-based polymer and silica was added, the noise reduction effect of the molded article was not properly exhibited as compared with example 2. In the case of comparative example 7 in which an excessive amount of the additive comprising the siloxane-based polymer and silica was added, the noise reduction performance of the molded article was exhibited, but the hardness performance was lowered. In particular, the very high melt flow index results in the molded article flowing down during molding.

Experimental example 2

Fig. 1 shows the surface condition of the test specimens manufactured according to examples 1 and 2 and comparative examples 2 and 3, in which the same amount of PTMG was used in the thermoplastic copolymer composition, after the test specimens were left for 1 week.

As shown in fig. 1, under the condition of using the same amount of PTMG, in the case of example 1 in which an additive containing silica and a silicone-based polymer was added and in the case of example 2 in which PBT was additionally added, no gloss was observed on the surface of the sample. On the other hand, in the case of comparative examples 2 and 3 in which silica and a siloxane-based polymer were not added, gloss was observed on the surface of the sample. These results show that the silica and silicone-based polymers used in examples 1 and 2 increase the bleeding rate of PTMG to such an extent that the surface gloss of the sample disappears. In addition, these results show that when the phenomenon is applied to molded articles such as constant velocity joint boots, a noise reduction effect is achieved in a noise test.

Experimental example 3

The friction coefficient and gloss of the thermoplastic copolymer composition samples manufactured in example 2 and comparative example 3 were measured using the following methods, and the results are shown in table 3 below.

5) Coefficient of friction: the coefficient of friction was measured while moving a spherical tip having a weight of 10kg by 30mm on a square sample of 100X 2 mm.

6) Gloss: gloss was measured using a gloss meter (TC-108DPA, Tokyo Denshoku Co.) at a reflection angle of 60 deg..

[ Table 3]

Referring to table 3, the thermoplastic copolymer composition containing an additive according to the present invention (example 2) had a very small friction coefficient, indicating excellent frictional noise resistance, compared to comparative example 3 containing no additive. In addition, the thermoplastic copolymer composition containing an additive according to the present invention (example 2) did not have a significant difference in gloss immediately after injection, compared to comparative example 3 containing no additive. However, when comparing the gloss after 1 week of standing at room temperature after injection, in example 2, the gloss was significantly reduced. On the other hand, in comparative example 3, the glossiness was not significantly reduced. These results show that the additive (c) used in example 2 increases the bleeding rate of PTMG to such an extent that the surface gloss of the injected sample disappears. It can be seen that surface bleeding of PTMG in the constant velocity joint boot results in noise reduction.