Thermoplastic resin composition and method for producing same

Abstract

The present invention relates to a thermoplastic resin composition and a method for producing the same, and more particularly to an environmentally friendly thermoplastic resin composition that is biodegradable yet has excellent moldability and mechanical properties such as improved tensile strength and elongation, and can therefore be used as an environmentally friendly material in a variety of fields, and a method for producing the same.

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition and a method for producing the same, and more particularly to a biodegradable, environmentally friendly thermoplastic resin composition and a method for producing the same. [Background technology]

[0002] Unlike thermosetting resins, thermoplastic resins lack bonds between chains (i.e., they are not crosslinked), making them advantageous for molding and processing. The easiest way to mold and process such thermoplastic resins is to utilize the thermal properties of thermoplastic polymers. Thermoplastic polymers change from a solid to a liquid state at temperatures above their melting point, making them easy to mold into desired shapes. In industrial settings, injection molding machines are commonly used to mold such polymers. Specifically, solid thermoplastic resins are injected in the form of pellets or powder into a high-temperature injection machine, where they are melted, and then injected and spun into fibers through a die, playing an important role in various plastic molding processes.

[0003] Typically, materials such as PET (polyethylene terephthalate), PE (polyethylene), and PP (polypropylene) have been used as such thermoplastic resins. However, with recent environmental concerns, the industrial application of environmentally friendly and biodegradable materials such as PLA (polylactic acid), PGA (polyglycolic acid), PLGA (polylactic-co-glycolic acid), PCL (polycaprolactone), PBAT (polybutylene adipate terephthalate), and PA (polyamide) has become a major issue.

[0004] Biodegradable thermoplastic resins, such as PLA, are significantly harder and more brittle than existing petroleum-based plastics, limiting their application in various industrial fields. Therefore, the most common methods for achieving this are blending softer, more flexible polymers to alter the material's physical properties or incorporating nanocomposites into thermoplastic resins to enhance ductility. While the former method can enhance ductility by blending and injection molding highly ductile polymers, such as PEG, PEO, and PU, it requires blending different polymers with chain extenders during injection molding, which can present processing challenges, such as the need to consider the compatibility and thermal properties between the polymers. Furthermore, the physical properties of the blended polymers can potentially reduce the biodegradability and biocompatibility of the original thermoplastic polymer.

[0005] On the other hand, the latter method involves mixing additives such as plasticizers during injection molding to change the ductility and / or physical properties of the thermoplastic resin. This method has the advantage that a small amount of additive can induce changes in physical properties and is based on the target material, the thermoplastic resin. However, most additives are difficult to dissolve, requiring additional processes. In addition, excessive amounts of additives can cause frequent breakage during high-temperature spinning, making the spinning process difficult. In addition, post-processing is poor due to the deterioration of the physical properties of the thermoplastic resin.

[0006] Therefore, Korean Patent No. 1992492 discloses a thermoplastic cellulose derivative composition containing a cellulose ester, a plasticizer, and a hydrolysis inhibitor in order to improve the processability of a thermoplastic resin, and Korean Patent No. 01837493 discloses an oxidative biodegradable additive composition containing a cellulose composition plasticized with a sodium bisulfite plasticizer in order to provide a thermoplastic cellulose resin with improved mechanical properties.

[0007] However, these thermoplastic resins also have problems such as a lack of flexibility, which results in rough surfaces during molding and easy breakage due to external impacts. Furthermore, when mixed with existing degradable plastic raw materials to produce molded products, chemical decomposition occurs, aggregates are generated, or the resins are processed into a hard appearance, limiting the amount of inclusion.

[0008] Therefore, there is a need to develop natural polymer thermoplastic raw materials that have excellent moldability while significantly improving the mechanical properties of thermoplastic resins, such as elongation and tensile strength. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent No. 1992492 (Publication date: June 19, 2014) [Patent Document 2] Korean Patent No. 1837493 (Publication date: July 29, 2016) Summary of the Invention [Problem to be solved by the invention]

[0010] The main object of the present invention is to solve the above-mentioned problems by providing a thermoplastic resin composition that is biodegradable, has excellent moldability, and has improved mechanical properties such as tensile strength and elongation, and a method for producing the same.

[0011] Another object of the present invention is to provide an environmentally friendly molded article formed from the thermoplastic resin composition. [Means for solving the problem]

[0012] In order to achieve the above object, one embodiment of the present invention provides a thermoplastic resin composition comprising 65% by weight to 80% by weight of hydroxyethyl cellulose, the viscosity of which, when a 2% by weight aqueous solution dissolved in water is measured at 20°C using a Brookfield viscometer, is 4,000 cps to 250,000 cps, and 20% by weight to 35% by weight of glycerin.

[0013] In a preferred embodiment of the present invention, the thermoplastic resin composition may further comprise one or more additives selected from the group consisting of antioxidants, lubricants, biodegradation accelerators, and strength reinforcements.

[0014] In a preferred embodiment of the present invention, the lubricant may be one or more selected from the group consisting of sorbitol, magnesium stearate, calcium stearate, ethylene glycol, glycerol monostearate, and lecithin.

[0015] Another embodiment of the present invention provides a method for producing a thermoplastic resin composition, comprising: (a) adding 20% ​​to 35% by weight of glycerin to 65% to 80% by weight of hydroxyethyl cellulose having a viscosity of 4,000 cps to 250,000 cps to form a mixture; and (b) kneading the mixture to plasticize it.

[0016] In another preferred embodiment of the present invention, the kneading in the step (b) can be carried out at 50°C to 90°C and at 300 rpm or more.

[0017] Another embodiment of the present invention provides a molded article formed from the above-described thermoplastic resin composition.

[0018] In another preferred embodiment of the present invention, the molded product can be characterized by having a tensile strength of 4.5 MPa to 6.5 MPa measured in accordance with ASTM D638.

[0019] In another preferred embodiment of the present invention, the molded article can be characterized by having an elongation of 20 mm to 45 mm as measured in accordance with ASTM D638. [Effects of the Invention]

[0020] The thermoplastic resin composition according to the present invention has excellent moldability while being biodegradable, and also has improved mechanical properties such as tensile strength and elongation, so that it can be used as an environmentally friendly material in various fields. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a photographic image of the molded product produced in Example 3 taken with a digital camera. [Figure 2] 1 is a photographic image of the molded product produced in Example 7 taken with a digital camera. [Figure 3] 1 is a photographic image of the molded product produced in Example 10 taken with a digital camera. [Figure 4] 1 is a photographic image of the molded product produced in Comparative Example 1 taken with a digital camera. [Figure 5] 1 is a photographic image of the molded product produced in Comparative Example 4 taken with a digital camera. DETAILED DESCRIPTION OF THE INVENTION

[0022] The advantages, features, and methods for achieving the same of the present invention will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be realized in various different forms. However, the present embodiments are provided solely to complete the disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art. The present invention is defined solely by the scope of the claims.

[0023] In describing the present invention, if it is determined that a detailed description of related known techniques may obscure the gist of the present invention, the detailed description will be omitted.

[0024] When terms such as "comprise," "have," "consist," and "consist" are used in this specification, other parts may be added unless "only" is used. When elements are expressed in the singular, this includes the plural unless otherwise expressly stated.

[0025] As referred to herein, "molded article" means a material that has been formed into a certain shape, such as an extrusion, extrusion, or the like.

[0026] The features of the various embodiments of the present invention may be partially or fully combined or combined with each other, and various technical interlocking and driving mechanisms may be possible, and each embodiment may be implemented independently of the other, or may be implemented together in a related relationship.

[0027] In one aspect, the present invention relates to a biodegradable thermoplastic resin composition comprising 65% to 80% by weight of hydroxyethyl cellulose having a viscosity of 4,000 cps to 250,000 cps and 20% to 35% by weight of glycerin.

[0028] Generally, cellulose derivatives such as hydroxyethyl cellulose have a polymer structure that is composed of strong hydrogen bonds, undergoes thermal decomposition below the melting point, and is difficult to process into plastics.

[0029] Therefore, in the present invention, by adding a specific amount of glycerin to hydroxyethyl cellulose, which is a cellulose derivative and has a specific viscosity, the strong hydrogen bonds of the hydroxyl groups of the hydroxyethyl cellulose are weakened, the distance between the chains is increased, and an environment in which micro-Brownian motion is easily generated is created, thereby lowering the glass transition temperature of the hydroxyethyl cellulose and imparting flexibility to the hydroxyethyl cellulose. As a result, a natural polymer thermoplastic resin can be provided which has excellent moldability and significantly improved mechanical properties such as elongation and tensile strength.

[0030] To avoid redundancy, each of the above components will be described in the method for producing a thermoplastic resin composition described below.

[0031] In another aspect, the present invention relates to a method for producing a biodegradable thermoplastic resin composition, comprising: (a) mixing 65% by weight to 80% by weight of hydroxyethyl cellulose having a viscosity of 4,000 cps to 250,000 cps with 20% by weight to 35% by weight of glycerin; and (b) kneading the mixture to plasticize it.

[0032] In the method for producing a thermoplastic resin composition according to the present invention, first, glycerin is added to hydroxyethyl cellulose [step (a)].

[0033] Hydroxyethyl cellulose (HEC) is a water-soluble polymer component in the form of a powder that is white or pale yellowish white. Among cellulose derivatives, it has the best flame resistance and pH stability, as well as colloidal properties, water retention, and temperature resistance. It is therefore recognized as a raw material that can be used in a variety of products in various industries.

[0034] In the present invention, the hydroxyethyl cellulose may be a base resin having a viscosity of 4,000 cps to 250,000 cps, where the viscosity of the hydroxyethyl cellulose is measured at 20°C using a Brookfield viscometer on an aqueous solution (hydroxyethyl cellulose: 2 wt%) of the hydroxyethyl cellulose.

[0035] If the viscosity of the hydroxyethyl cellulose is less than 4,000 cps, the kneading property with glycerin is insufficient, which may cause problems of poor extrusion and browning, and furthermore, the glycerin may dissolve after extrusion, causing stickiness. If the viscosity exceeds 250,000 cps, the viscosity when kneaded with glycerin is too high, which may cause problems of poor extrusion, unstable extrusion operation, and browning due to carbonization.

[0036] The hydroxyethyl cellulose may be mixed in an amount of 65 to 80% by weight based on the total weight of the composition. If the hydroxyethyl cellulose content is less than 65% by weight, the glycerin content may be excessive, resulting in stickiness and difficulty in pelletizing, and the mixture may form lumps that are difficult to feed into an extruder or other device after plasticization. If the hydroxyethyl cellulose content is more than 80% by weight, the glycerin may not be sufficiently plasticized, making it impossible to produce a thermoplastic resin.

[0037] The hydroxyethyl cellulose may be used as a compatibilized product or may be prepared by preparation. Any known method in the art may be used as a method for preparing hydroxyethyl cellulose. For example, hydroxyethyl cellulose may be prepared by reacting cellulose with an alkalizing agent to obtain alkalized cellulose, and then etherifying the alkalized cellulose.

[0038] Glycerin can be obtained as a by-product when soap or fatty acids are produced from natural resins, but recently it has been synthesized by treating propylene with chlorine to produce epichlorohydrin, which is then hydrolyzed. It is used in a variety of fields, including rubber, toothpaste, cosmetics, chemicals, paints, cellophane, printing inks, and sweets.

[0039] In the present invention, the glycerin is mixed with hydroxyethyl cellulose to disrupt the strong hydrogen bonds formed by the hydroxyl groups of the hydroxyethyl cellulose, thereby increasing the distance between cellulose polymer chains and creating an environment in which micro-Brownian motion is more likely to occur. The glycerin may be added in an amount of 20 to 35% by weight based on the total weight of the composition.

[0040] If the content of glycerin is less than 20 wt % based on the total weight of the composition, the effect of interfering with the strong hydrogen bonds of the hydroxyl groups of hydroxyethyl cellulose and increasing the distance between cellulose polymer chains to create an environment conducive to micro-Brownian motion is insufficient, making it impossible to lower the glass transition temperature and impart flexibility to the resin. On the other hand, if the content exceeds 35 wt %, excessive glycerin may dissolve, causing stickiness and making pelletization difficult.

[0041] Thereafter, the mixture of hydroxyethyl cellulose and glycerin can be kneaded to plasticize it [step (b)].

[0042] The mixture can be kneaded at 50°C to 90°C and at 300 rpm or more, preferably 70°C to 90°C and at 300 rpm to 600 rpm, so as to facilitate plasticization of the hydroxyethyl cellulose. The kneading time can be appropriately adjusted depending on the content of the mixture and the degree of plasticization, and is preferably 30 to 60 minutes.

[0043] When kneading is performed under the above conditions, the glass transition temperature and melting point can be lowered so that micro-Brownian motion of hydroxyethyl cellulose is likely to occur, and therefore, even with a small amount of glycerin, the plasticization efficiency of hydroxyethyl cellulose can be improved.

[0044] The kneading may be carried out by any method, either alone using a kneader or together with extrusion, which will be described later, using an extruder.

[0045] In this case, the kneader is not particularly limited, and any kneader commonly used in the art may be used without limitation, and examples thereof include a high-speed stirrer, a mixer, and a blender.

[0046] Meanwhile, in the method for producing a thermoplastic resin composition of the present invention, additives may be further added and mixed as needed before and / or after the kneading (plasticization) step.

[0047] The additive may be one or more selected from the group consisting of antioxidants, lubricants, biodegradation promoters, and strength reinforcements, and is a component commonly used in the relevant field, and the present invention does not place any particular limitation on the selection of the additive.

[0048] Specifically, among the additives, the antioxidant serves to prevent thermal decomposition of hydroxyethyl cellulose during thermoplasticization and molding, and is a common antioxidant available in the art. Examples include tetrakismethylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)methane, tris(2,4-di-t-butylphenyl)phosphate, etc., which may be used alone or in combination.

[0049] The lubricant is used to improve the lubricating properties of the thermoplastic resin, and any ordinary lubricant that can be used in the relevant field can be used without limitation. In terms of miscibility with the thermoplastic resin composition of the present invention and lubricating properties, the lubricant may be preferably one or more selected from the group consisting of sorbitol, magnesium stearate, calcium stearate, ethylene glycol, glycerol monostearate, and lecithin.

[0050] Furthermore, the biodegradation accelerator and strength reinforcement agent can be any conventional biodegradation accelerator and strength reinforcement agent that can accelerate the biodegradation of a thermoplastic resin or reinforce the strength of the resin, and examples of the biodegradation accelerator include fatty oils such as soybean oil, castor oil, linseed oil, sunflower oil, and coconut oil; fatty acids such as caproic acid, capric acid, lauric acid, oleic acid, olenic acid, and linoleic acid; and fatty acid esters such as ethyl oleate, ethyl linoleate, and isooctylates, which can be used alone or in combination of two or more. Examples of strength reinforcement agents include glass fiber and carbon fiber.

[0051] Such additives can be selected without limitation in the amount normally used within a range that does not impair the intended physical properties of the thermoplastic resin composition of the present invention, but preferably, each additive can be independently present in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the thermoplastic resin composition of the present invention.

[0052] The method for producing a thermoplastic resin composition according to the present invention further includes an extrusion step and a cutting step of extruding and cutting the kneaded (plasticized) composition, whereby the composition can be obtained in a form that is easy to commercialize.

[0053] The extrusion step may be performed using an extruder. The extruder is not particularly limited and may be any extruder commonly used in the art. For example, a single-screw extruder having one screw or a multi-screw extruder having multiple screws may be used. In consideration of uniform mixing of materials, ease of processing, and economy, it is preferable to use a twin-screw extruder having two screws.

[0054] At this time, the temperature of the extruder may be 70°C to 200°C, preferably 130°C to 180°C, so that extrusion is carried out efficiently without decomposition of the thermoplastic resin, and the screw rotation speed of the extruder may be 20 rpm to 300 rpm, preferably 20 rpm to 200 rpm. Such extrusion conditions have the advantage that the throughput per unit time is appropriate, which allows for sufficient extrusion while providing excellent process efficiency, and does not cause problems such as thermal decomposition of the resin component.

[0055] The extrudate can be easily handled using a pelletizer or the like and cut into a form that facilitates the production of molded products, and is preferably in the form of pellets.

[0056] It is also effective that the method for producing a thermoplastic resin composition of the present invention further comprises a cooling step of cooling via a cooling water tank between the extrusion and cutting steps, and it is preferable that the cutting step is followed by a drying step of drying at 50°C to 80°C for 4 hours to 8 hours.

[0057] The thermoplastic resin composition according to the present invention thus prepared is biodegradable and has excellent elongation and tensile strength. In addition, it has excellent moldability and can be easily mixed and processed with petroleum-based thermoplastic resins, and therefore can be used as an additive in various thermoplastic resins.

[0058] In another aspect, the present invention relates to a molded article formed from the thermoplastic resin composition.

[0059] The molded article according to the present invention is formed from the thermoplastic resin composition described above, and can be manufactured into various molded articles (products) by various molding methods such as injection molding, extrusion molding, vacuum molding, casting molding, etc. Such molding methods are well known to those skilled in the art.

[0060] The molded product formed by such a molding method has, for example, a tensile strength of 4.5 MPa to 6.5 MPa and an elongation of 20 mm to 45 mm as measured according to ASTM D638, and is excellent in mechanical properties and moldability. In addition, it is biodegradable, and therefore can be usefully used in foods, electrical / electronic products, automobile parts, building materials, household goods, toys, agricultural materials, marine materials, etc.

[0061] In describing the thermoplastic resin composition of the present invention, its production method, and molded article, other conditions, equipment, etc. not explicitly described can be appropriately selected within the range commonly used in the art, and it is clearly stated that there are no particular limitations. [Example]

[0062] The present invention will be described in more detail below with reference to specific examples. The following examples are merely illustrative examples to aid in understanding the present invention, and the scope of the present invention is not limited thereto.

[0063] Example 1 As a cellulose derivative, 20% by weight of glycerin was added to 80% by weight of hydroxyethyl cellulose (Lotte Fine Chemicals, HEC B100K) with a viscosity of 100,000 cps, and the mixture was plasticized by high-speed mixing at 300 rpm for 30 minutes. After that, a strand-shaped extruder was produced using a twin-screw extruder with a screw speed of 30 rpm (main motor speed: 200 rpm to 250 rpm).

[0064] <Examples 2 to 10> The same method as in Example 1 was used, but the conditions were changed as shown in Table 1 below to produce a strand-shaped molded product.

[0065] <Comparative Examples 1 to 10> The same method as in Example 1 was used, but the conditions were changed as shown in Table 1 below to produce a strand-shaped molded product.

[0066] [Table 1]

[0067] [Experimental Example] The properties of the test pieces produced in Examples 1 to 10 and Comparative Examples 1 to 10 were measured by the following methods, and the results are shown in Table 2 below and in FIGS.

[0068] <Measurement method> (1) Measurement of moldability: The flowability of the extrudate immediately after extrusion was evaluated with the naked eye. If the extrusion was easy and the extrudate was in good condition, it was evaluated as "good," and if it was not extruded, it was evaluated as "poor," as shown in Table 2. (2) Measurement of the state of the extrudate: Immediately after the extrudate was discharged, the color, surface roughness, and stickiness of the extrudate were measured using an optical microscope (SOMETECH SV-55) at a magnification of 60 times. The results are shown in Table 2 and Figures 1 to 5. (3) Measurement of tensile strength: To measure the tensile strength of thermoplastic resins, test pieces were prepared according to ASTM D638 standard, and then the tensile strength was measured using a Universal Test Machine (UTM, Instron Model 4465). The tensile speed was 10 mm / min, and the measurement was repeated 7 times. The upper and lower limits were discarded, and the average value of 5 measurements was calculated and listed in Table 2. (4) Measurement of elongation: To measure the elongation of thermoplastic resins, test pieces were prepared according to ASTM D638 standard, and then the elongation was measured using a Universal Test Machine (UTM, Instron Model 4465). The grip distance and gauge distance were fixed at 40 mm, and the measurement was performed seven times at a speed of 10 mm / min. The upper and lower limits were discarded, and the average value of five measurements was calculated and listed in Table 2.

[0069] [Table 2]

[0070] As can be seen from Table 2 and FIGS. 1 to 5, the molded products produced in Examples 1 to 10 had good moldability, and the extruded products had excellent color and surface condition, and were also measured to have high tensile strength and elongation. On the other hand, the molded products produced in Comparative Examples 1 to 10 were either not extruded and therefore could not be measured, or even if extruded, the molded products had a rough appearance, were sticky, or suffered from browning, and had low tensile strength and elongation.

[0071] In particular, the molded products extruded in Comparative Examples 1 and 7 to 9 were not extruded because they did not melt, and the molded product extruded in Comparative Example 4 suffered from severe browning and had a rough surface. Furthermore, the molded product extruded in Comparative Example 5 suffered from severe browning and was found to have poor tensile strength, and the molded product extruded in Comparative Example 10 had good transparency but poor elongation.

[0072] Therefore, the thermoplastic resin composition according to the present invention has excellent moldability and improved mechanical properties such as tensile strength and elongation. Since the thermoplastic resin composition according to the present invention contains a cellulose derivative and glycerin as active ingredients, it can be used in an environmentally friendly manner and can be useful in various fields.

[0073] Although the present invention has been described above using limited examples and drawings, it goes without saying that the present invention is not limited thereto, and various modifications and variations can be made by those skilled in the art within the scope of the technical concept of the present invention and the equivalent scope of the following claims.

Claims

1. A thermoplastic resin composition comprising 65% by weight to 80% by weight of hydroxyethyl cellulose, the viscosity of which is 4,000 cps to 250,000 cps when an aqueous solution of the hydroxyethyl cellulose dissolved in water at 2% by weight is measured at 20°C using a Brookfield viscometer, and 20% by weight to 35% by weight of glycerin.

2. The thermoplastic resin composition according to claim 1, further comprising one or more additives selected from the group consisting of antioxidants, lubricants, biodegradation accelerators, and strength reinforcements.

3. 3. The thermoplastic resin composition according to claim 2, wherein the lubricant is at least one selected from the group consisting of sorbitol, magnesium stearate, calcium stearate, ethylene glycol, glycerol monostearate, and lecithin.

4. (a) adding 20% ​​to 35% by weight of glycerin to 65% to 80% by weight of hydroxyethyl cellulose, the viscosity of which, when a 2% by weight aqueous solution dissolved in water is measured using a Burkfield viscometer at 20°C, is 4,000 to 250,000 cps; (b) kneading the mixture to plasticize it.

5. The method for producing a thermoplastic resin composition according to claim 4, wherein the kneading in the step (b) is carried out at 50°C to 90°C and 300 rpm or more.

6. A molded article formed from the thermoplastic resin composition according to any one of claims 1 to 3.

7. The molded article according to claim 6, wherein the molded article has a tensile strength of 4.5 MPa to 6.5 MPa as measured in accordance with ASTM D638.

8. The molded article according to claim 6, wherein the molded article has an elongation of 20 mm to 45 mm as measured in accordance with ASTM D638.

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