KR102577314B1 - Resin composition, method for reliability evaluation of the same, molded article containing the same and method of molded article - Google Patents

Abstract

This application provides a resin composition capable of exhibiting excellent dimensional stability, flexibility, and release properties, a method for evaluating its reliability, and a molded article manufactured therefrom.

Description

Resin composition, reliability evaluation method thereof, molded article containing the same, and method of manufacturing the molded article {RESIN COMPOSITION, METHOD FOR RELIABILITY EVALUATION OF THE SAME, MOLDED ARTICLE CONTAINING THE SAME AND METHOD OF MOLDED ARTICLE}

This application relates to a resin composition, a method for evaluating its reliability, a molded article containing the same, and a method for manufacturing the molded article.

Block-type parts (hereinafter referred to as molded products) that are repeatedly assembled and disassembled are commonly used in toys (toys), automotive products, electrical/electronic products, and office equipment. Generally, block-shaped molded products that are repeatedly assembled/separated are manufactured by injection molding polymer resin. In the case of these block-type molded products, standard specifications are set to ensure smooth assembly and separation, and if the standard specifications are not met, assembly and separation are not smooth. For example, if it is manufactured too large than the standard, it will be loose during assembly/separation, and if it is manufactured too small, it will be stiff during assembly/separation.

Therefore, in the case of block-type molded products, it is important that they are manufactured accurately according to standard specifications, and deformations such as shrinkage after molding must be minimized. For this purpose, the selection of material for the molded product is important.

Meanwhile, among injection moldability, dimensional stability, flexibility, and release property are the factors that most affect the quality of molded products. Therefore, when manufacturing molded products, it is important to select a resin material with excellent dimensional stability, flexibility, and release properties.

In order to select a material for a molded product, the dimensional stability, flexibility, and release properties of the material must be evaluated first, but the existing method of evaluating injection moldability was conducted by directly injecting the molded product. For example, flexibility and release properties were evaluated by measuring how much pressure was applied when separating the molded product from the injection machine. In addition, the dimensional stability of the molded product was evaluated by measuring the force applied during repeated assembly/separation operations after injection. Existing evaluation methods have the disadvantage of taking a lot of time because they produce separate samples from molded products and then compare and evaluate the multiple samples produced.

This application provides a resin composition capable of achieving excellent dimensional stability, flexibility, and release properties, a method for evaluating its reliability, a molded article containing the same, and a method for manufacturing the molded article.

This application relates to a method for evaluating the reliability of a resin composition. The reliability evaluation method relates to a method of evaluating the reliability of a resin composition manufactured into a molded article through injection molding. Specifically, the above evaluation method can evaluate the reliability of the molded product after molding by using the unique physical properties of the resin composition before molding.

An exemplary reliability evaluation method is a reliability evaluation method of a resin composition containing a polymer resin. The polymer resin may satisfy the following general formula 1 or have a residual stress ratio of 0.6 or less according to general formula 2.

[General Formula 1]

Te>100℃

[General Formula 2]

(RS ₁₀ /RS ₀ )×100

In the general formula 1, Te is produced by manufacturing a polymer resin into a solid specimen in the form of a film, and then sequentially increasing the temperature at a heating rate of 5℃/min from 25℃ and applying a constant force of 0.1 to 0.2N. When stretched in the longitudinal direction, it represents the temperature at which the stretching speed changes to 0.02 mm/℃ or more compared to the initial stretching speed. The force for stretching the specimen in the longitudinal direction may be 0.1 to 0.2 N, 0.12 to 0.18 N, or 0.14 to 0.16 N. For example, the specimen may be stretched in the longitudinal direction with a constant force of about 0.145 N. The solid specimen has an asymmetric shape consisting of a tenon and an end, and the term “longitudinal direction” in the above refers to the direction of the tenon. For example, a solid specimen has a predetermined length (tenon), width (end), and thickness, for example, the length is in the range of 15 mm to 50 mm, the width is in the range of 1 mm to 10 mm, and the thickness is It may range from 0.1mm to 5mm. In addition, the term “initial stretching speed” in the above refers to the stretching speed at the start of stretching. The stretching temperature can be measured using DMA (Dynamic Mechanical Analysis).

In addition, in the general formula 2, RS ₀ represents the initial residual stress of the polymer resin when 100% strain is applied to the solid specimen of the polymer resin at a temperature of 220°C, and RS ₁₀ represents 10 after applying the strain. When seconds elapse, it represents the polymer resin residual stress. In the above, the term “initial residual stress” refers to the residual stress measured at any time of 0.05 seconds, 0.03 seconds, or 0.01 seconds or less after applying the deformation. The residual stress can be measured using the Advanced Rheometric Expansion System (ARES-G2).

Polymer resin, when heated, has the physical property of deforming its shape due to external force, and at a certain temperature, the rate of shape deformation increases rapidly. The stretching temperature according to General Formula 1 refers to the specific temperature at which the deformation rate increases rapidly. In addition, the higher the stretching temperature of the polymer resin, the more excellent release properties and heat resistance can be realized in the molded product to which it is applied. Therefore, the stretching temperature of General Formula 1 can be used as an indicator to determine the flexibility and heat resistance of the molded product containing the polymer resin. there is.

In addition, polymer resins exhibit physical properties that tend to return to their original shape, similar to elastic objects, when the external force is removed. In this specification, the term “residual stress” refers to the force that causes the polymer resin to return to its original shape. In this way, the residual stress gradually decreases over time, and the residual stress ratio in General Equation 2 represents the degree of reduction of the residual stress over time. In particular, the faster the polymer resin reduces residual stress, the better dimensional stability can be realized in molded products to which it is applied. Therefore, the ratio of residual stress in General Formula 2 is an indicator for judging the dimensional stability of molded products containing polymer resin. It can be used as

In one example, the reliability evaluation method may be performed by comparing the ratio of stretching temperature and residual stress of two or more resin compositions. For example, the reliability evaluation method may compare two or more resin compositions and evaluate that the resin composition with a high stretching temperature in General Formula 1 or a low residual stress ratio in General Formula 2 has high reliability. When such a resin composition is manufactured into a block-shaped molded product that undergoes repeated assembly/separation, it can be evaluated as having excellent dimensional stability, flexibility, and release properties.

Specifically, according to the evaluation method of the present application, the lower the stretching temperature according to General Formula 1, the lower the flexibility and release properties of the molded product manufactured from the resin composition, and the higher the stretching temperature, the better the flexibility and release properties. In addition, the higher the residual stress ratio according to General Formula 2, the lower the dimensional stability of the molded product manufactured from the resin composition, and the lower the residual stress ratio, the better the dimensional stability of the molded product.

In one embodiment, the stretching temperature of the polymer resin represented by General Formula 1 may be greater than 100°C, greater than 105°C, greater than 110°C, greater than 120°C, or greater than 130°C. The upper limit of the stretching temperature is not particularly limited, but may be less than 200°C, less than 190°C, less than 180°C, or less than 170°C. For example, the stretching temperature represented by General Formula 1 may be greater than 100°C and less than 200°C.

Additionally, the residual stress ratio expressed by General Formula 2 may be 0.6 or less, 0.55 or less, or 0.50 or less. The lower limit of the residual stress ratio is not particularly limited, but may be 0.01 or more, 0.05 or more, or 0.1 or more. For example, the residual stress ratio represented by General Formula 2 may be in the range of 0.1 to 0.55.

According to the above evaluation method, it is possible to provide a resin composition that satisfies General Formula 1 or the residual stress according to General Formula 2 satisfies the above-mentioned range, and has excellent dimensional stability, flexibility, and release property depending on the application of the resin composition. A molded product that can be implemented can be provided.

In one example, the type of polymer resin is not particularly limited as long as the polymer resin realizes physical properties related to stretching temperature and residual stress. For example, the polymer resin may be a thermoplastic resin. In the present application, in order to adjust the stretching temperature represented by General Formula 1 or the ratio of residual stress represented by General Formula 2 within the above range, the type of thermoplastic resin can be appropriately selected, thereby improving dimensional stability and flexibility when manufacturing a molded product. And a resin composition with excellent release properties can be provided.

In one example, the thermoplastic resin may include one or more from the group consisting of acrylonitrile-butadiene-styrene (ABS) resin, polyalkylene terephthalate resin, polycarbonate resin, polyolefin resin, and polyphthalamide resin, Considering processability and excellent mechanical strength and durability of molded products, acrylonitrile butadiene styrene (ABS) resin may be preferable as the thermoplastic resin.

In one embodiment, the acrylonitrile butadiene styrene resin may be a copolymer of styrene-acrylonitrile copolymer (SAN) and butadiene rubber (BR). In the case of the acrylonitrile butadiene styrene resin, the necessary mechanical strength and durability can be achieved by appropriately selecting the content of the styrene-acrylonitrile copolymer and butadiene rubber and the particle size ratio of butadiene rubber within the following ranges.

For example, the content of the styrene acrylonitrile copolymer ranges from 10 to 70 parts by weight, 20 to 70 parts by weight, 40 to 70 parts by weight, or 50 to 70 parts by weight, based on 100 parts by weight of the total acrylonitrile butadiene styrene resin. can be appropriately selected within. Additionally, the content of butadiene rubber may be appropriately selected within the range of 30 to 50 parts by weight, 30 to 40 parts by weight, or 30 to 35 parts by weight based on 100 parts by weight of acrylonitrile butadiene styrene resin. Additionally, the particle size ratio of butadiene rubber (BR) may be appropriately selected within the range of 1:1 to 3:1 between large and small particle sizes.

In one embodiment, in order for the polymer resin to satisfy a specific range of variables according to the above-described General Formula 1 or 2, it is important to select the weight average molecular weight and glass transition temperature of the polymer resin within the ranges described below.

In one example, in order to satisfy the above-described General Formula 1 or 2, the weight average molecular weight of the polymer resin may range from about 10,000 to 1 million, 50,000 to 500,000, or 100,000 to 150,000. In this specification, the term “weight average molecular weight” refers to the converted value for standard polystyrene measured by GPC (Gel Permeation Chromatograph).

Additionally, the glass transition temperature of the polymer resin may be -150°C to 0°C, -120°C to -30°C, or -100°C to -50°C.

The evaluation method according to the present application determines the reliability of the heat resistance and release property of the molded product manufactured from the resin composition containing the polymer resin through whether the variables defined by the above-mentioned general formula 1 satisfy a specific range. And the reliability of the dimensional stability and heat resistance of the molded product manufactured therefrom can be determined through whether the variable defined by General Formula 2 satisfies a specific range.

This application also relates to resin compositions. The resin composition may be a resin composition evaluated to be excellent in dimensional stability, flexibility, heat resistance, and release property according to the reliability evaluation method described above.

The exemplary resin composition may include a polymer resin that satisfies the following General Formula 1 or has a residual stress ratio expressed by General Formula 2 of 0.6 or less.

[General Formula 1]

Te>100℃

[General Formula 2]

(RS ₁₀ /RS ₀ )×100

In the general formula 1, Te is produced by manufacturing a polymer resin into a solid specimen in the form of a film, and then sequentially increasing the temperature at a heating rate of 5℃/min from 25℃ and applying a constant force of 0.1 to 0.2N. When stretched in the longitudinal direction, it represents the stretching temperature at the point when the stretching speed changes to 0.02 mm/°C or more compared to the initial stretching speed.

In addition, in the general formula 2, RS ₀ represents the initial residual stress when 100% strain is applied to a solid specimen of polymer resin at a temperature of 220°C, and RS ₁₀ represents 10 after applying the strain. When seconds have elapsed, it indicates residual stress.

Additionally, the present application relates to a molded article containing the above-described resin composition. Detailed descriptions related to the resin composition are omitted below since they overlap with the above-described content. As the molded article is manufactured from a resin composition that satisfies the physical properties according to the above-described General Formula 1 and/or General Formula 2, excellent dimensional stability, flexibility, and release property can be achieved. Additionally, the molded article may include other components necessary for molding other than the above-described resin composition without limitation.

In addition, the present application relates to a method for producing a molded article by processing the above-described resin composition. Detailed descriptions related to the resin composition are omitted below since they overlap with the above-described content.

In one example, the processing may be an extrusion process, an injection process, or either an extrusion and injection process. Since this forming method is widely known, detailed description is omitted.

This application provides a resin composition with excellent dimensional stability, flexibility, and release properties through the stretching temperature and residual stress ratio of the resin composition, a method for evaluating its reliability, and a molded article manufactured therefrom.

Figure 1 is a graph showing the softening temperature of the resin composition prepared in the Examples and Comparative Examples of the present application according to General Formula 1.
Figure 2 is a graph showing the residual stress ratio of the resin composition prepared in the Examples and Comparative Examples of the present application according to General Formula 2.
Figure 3 is a graph showing the pressure at which a mark is left on a specimen according to the softening temperature according to General Equation 1.
Figure 4 is a graph showing the force applied during assembly/disassembly according to the residual stress ratio according to General Equation 2.

Hereinafter, the present invention will be described in more detail through examples according to the present invention and comparative examples not according to the present invention, but the scope of the present invention is not limited to the examples presented below.

Example

Acrylonitrile-butadiene-styrene (ABS) resin is obtained by graft polymerizing 67 parts by weight of high molecular weight styrene-acrylonitrile copolymer (SAN) and 33 parts by weight of butadiene rubber (BR) with a large particle size to small particle size ratio of 1:1. was manufactured. Using a hot press device, a solid specimen in the form of a film with a length of 20 mm, a width of 6 mm, and a thickness of 1 mm was produced from the resin.

Comparative example One

Acrylonitrile-butadiene-styrene (ABS) resin is obtained by graft polymerizing 72 parts by weight of high molecular weight styrene-acrylonitrile copolymer (SAN) and 28 parts by weight of butadiene rubber (BR) with a ratio of large and small particle diameters of 3:1. was prepared. Using a hot press device, a solid specimen in the form of a film with a length of 20 mm, a width of 6 mm, and a thickness of 1 mm was produced from the resin composition.

Comparative example 2

Acrylonitrile-butadiene-styrene (ABS) resin was made by graft polymerizing 72 parts by weight of low molecular weight styrene-acrylonitrile copolymer (SAN) and 28 parts by weight of butadiene rubber (BR) with a large particle size to small particle size ratio of 3:1. was manufactured. Using a hot press device, a solid specimen in the form of a film with a length of 20 mm, a width of 6 mm, and a thickness of 1 mm was produced from the resin.

For the solid specimens prepared in Examples and Comparative Examples, the stretching temperature of General Formula 1 and the residual stress of General Formula 2 were measured, and the results are shown in Figures 1 and 2. Referring to Figures 1 and 2, it was confirmed that the solid specimens prepared in the examples satisfied the above-described general formulas 1 and 2.

Meanwhile, the following experiment was performed to confirm the correlation between the stretching temperature and residual stress and the injection moldability of the molded product.

Experiment example - Injection moldability evaluation

One. stretching Evaluation of flexibility and release properties of molded products according to temperature

When pressure was applied to a solid specimen, the initial pressure at which marks were created had a high correlation with flexibility and release properties, and it was confirmed that the higher the initial pressure at which marks were created, the higher the flexibility and release properties were. In order to confirm the correlation between the initial pressure at which marks appear and the stretching temperature, a plurality of solid specimens with different stretching temperatures according to General Formula 1 were prepared.

Using an injection machine, the pressure was sequentially increased until marks appeared on the prepared solid specimen, and the results are shown in Figure 3. Referring to Figure 3, the higher the softening temperature according to General Equation 1, the higher the initial pressure at which marks appear. From this, it was confirmed that the higher the softening temperature, the higher the flexibility and release properties.

2. Dimensional stability evaluation according to residual stress ratio

It was confirmed that the force applied when assembling/separating a molded product is highly correlated with the dimensional stability of the molded product, and that dimensional stability is high only when the force applied during assembly/separation exceeds a certain level. In order to confirm the correlation between the force applied during assembly/separation and the ratio of residual stress, a plurality of block-shaped molded products of a male/female pair with different ratios of residual stress according to General Equation 2 and capable of assembly/separation were prepared. did.

The load applied when assembling/separating the male/female pair of block-shaped molded products was measured five times repeatedly, and the average value is shown in FIG. 4. Referring to FIG. 4, the lower the residual stress ratio according to General Equation 2, the higher the force applied during assembly/separation. From this, it was confirmed that the lower the residual stress ratio, the higher the dimensional stability.

Claims (11)

A method for evaluating the reliability of a resin composition containing a polymer resin,
The polymer resin satisfies the following general formula 1 and has a residual stress ratio of 0.6 or less according to the following general formula 2,
Release properties are evaluated from the correlation between the general formula 1 below and the initial pressure at which marks on the specimen are formed, and dimensional stability is evaluated from the correlation between the general formula 2 below and the force applied during assembly and separation of the specimen,
The above resin composition is a reliability evaluation method used for block-type molded products that are repeatedly assembled and separated:
[General Formula 1]
Te>100℃
[General Formula 2]
(RS ₁₀ /RS ₀ )×100
In the general formula 1, Te is produced by manufacturing the polymer resin into a solid specimen in the form of a film, and then sequentially increasing the temperature at a heating rate of 5℃/min from 25℃ and applying a constant force of 0.1 to 0.2N. When stretched in the longitudinal direction, it represents the stretching temperature at the point when the stretching speed changes to 0.02 mm/℃ or more compared to the initial stretching speed,
In General Formula 2, RS ₀ represents the initial residual stress when 100% strain is applied to a specimen containing the polymer resin at a temperature of 220°C, and RS ₁₀ represents 10 after applying the strain. When seconds have elapsed, it indicates residual stress. The reliability evaluation method according to claim 1, wherein the polymer resin is a thermoplastic resin. The method of claim 2, wherein the thermoplastic resin comprises at least one selected from the group consisting of acrylonitrile-butadiene-styrene (ABS) resin, polyalkylene terephthalate resin, polycarbonate resin, polyolefin resin, and polyphthalamide resin. Reliability evaluation method. The reliability evaluation method according to claim 1, wherein the polymer resin has a weight average molecular weight of 10,000 to 1,000,000. The reliability evaluation method according to claim 1, wherein the glass transition temperature of the polymer resin is within the range of -150°C to 0°C. The reliability evaluation method according to claim 1, wherein the stretching temperature according to General Formula 1 is greater than 100°C and less than 200°C. The reliability evaluation method according to claim 1, wherein the residual stress ratio according to General Equation 2 is in the range of 0.1 to 0.55. delete delete delete delete