KR102563871B1 - The high-efficiency reinforced thermoplastics comprised of comprise of milled cellulose fibers - Google Patents

Abstract

The present invention relates to a high-efficiency fiber-reinforced thermoplastic resin composition in which a small amount of milled lyocell fiber is mixed with a thermoplastic resin to improve physical properties, and the high-efficiency fiber-reinforced thermoplastic resin composition according to the present invention is an eco-friendly composite material Thus, by including the lyocell fiber powder in the thermoplastic resin, it is possible to maximize the physical properties while improving the productivity of the kneading process even without using long fibers. In particular, even with the addition of a small amount of lyocell of 0.1 to 30 wt%, the elastic modulus can be improved while maintaining the same level of flexural strength and tensile strength.

Description

The high-efficiency fiber-reinforced thermoplastic resin composition comprising finely divided cellulose fibers {The high-efficiency reinforced thermoplastics comprised of comprising of milled cellulose fibers}

The present invention relates to a high-efficiency fiber-reinforced thermoplastic resin composition comprising finely divided cellulose fibers having improved physical properties and performance by mixing a small amount of milled lyocell fiber with a thermoplastic resin.

Cellulose-based carbon fabrics have good flexibility, low thermal conductivity, and ultra-high temperature abrasion resistance, so they are mainly used as high-temperature insulation materials in the aerospace field, such as rocket nozzles and missile warheads. Rayon fiber is mainly used as a precursor, but since chemicals harmful to the human body such as sulfuric acid (H ₂ SO ₄ ) and carbon disulfide (CS ₂ ) are used in fiber manufacturing, manufacturing facilities are gradually being reduced. Research on eco-friendly Lyocell, which can replace rayon, is increasing. Compared to existing rayon fibers, Lyocell has a simple manufacturing process, is harmless to the environment and human body, and has excellent shape stability.

Lyocell is a 　fiber made from natural pulp and amine oxide hydrate, and has excellent 　fiber　characteristics such as tensile and tactile properties compared to regenerated fibers, but does not generate any contaminants in the production process, and the amine used Oxide-based solvents are recyclable and biodegradable when discarded, so they are used in various fields as eco-friendly fibers.

In addition, natural fibers such as lyocell have lower tensile strength and tensile modulus than conventional glass fibers, which have been widely used as reinforcing fibers for polymer resins, so it is difficult to expect dramatic improvements in mechanical properties. The density (1.2~1.5 g/cm ³ ) is relatively lower than that of glass fiber (2.5 ~ 2.6 g/cm ³ ), so it is possible to obtain the physical properties of a composite material comparable to glass fiber in terms of specific strength and specific modulus, thus developing lightweight materials. expected to be very useful.

Regarding reinforcing fibers or composite materials of polymer resin, Korean Patent Publication No. 2014-0080481 discloses a fiber-reinforced resin composition comprising a resin-impregnated long fiber bundle including (A) a thermoplastic resin and (B) rayon fiber, ( The rayon fibers of component B) have a fiber diameter of 5 to 30 μm and an X-ray orientation of 86% or more, and the resin-impregnated long fiber bundle has a 2,000 to 30,000 Disclosed is a fiber-reinforced resin composition in which a molded product having a light weight and high mechanical strength is obtained by impregnating and integrating the bundled thermoplastic resin of component (A) in a melted state and then cutting it into a length of 3 to 30 mm.

In addition, Korean Patent Publication No. 2017-0139108 discloses a fiber-reinforced thermoplastic resin composition containing continuous reinforcing fibers such as glass fibers, carbon fibers, or aramid fibers and a thermoplastic resin, wherein the thermoplastic resin is a cyano group-containing vinyl monomer and an aromatic-based resin. A fiber-reinforced thermoplastic resin composition comprising a copolymer of vinyl monomers is disclosed.

However, since the above methods use long fiber bundles, it is difficult to disperse the fibers due to mutual agglomeration of the fibers, so it is difficult to input a uniform amount. In the case of composite materials using continuous fibers, the manufacturing process is very inconvenient and molding There is a problem that the process cost increases due to poor performance.

Accordingly, it is necessary to develop a composite material having improved physical properties without aggregation of fibers and a simple manufacturing process by mixing with a thermoplastic resin.

Republic of Korea Patent Publication No. 2014-0080481 Republic of Korea Patent Publication No. 2017-0139108

An object of the present invention is to provide a high-efficiency fiber-reinforced thermoplastic resin composition containing finely divided cellulose fibers whose physical properties and performance are improved by mixing a small amount of lyocell fibers with a thermoplastic resin.

In addition, it is intended to provide a high-efficiency fiber-reinforced thermoplastic resin composition capable of maximizing physical properties while improving productivity in a kneading process even without using long fibers by including milled lyocell fiber.

In order to solve the above problem,

In one embodiment, the present invention

thermoplastic resin; And it provides a high-efficiency fiber-reinforced thermoplastic resin composition comprising milled lyocell fiber.

The thermoplastic resin may be polypropylene, polylactic acid, or polyamide 6.

The lyocell fiber powder may contain 0.1 to 30 wt%.

The lyocell fiber powder may have a fiber length of 0.1 to 3.0 mm and an aspect ratio of 3 to 200.

In addition to the thermoplastic resin, polylactic acid may be further included.

The high-efficiency fiber-reinforced thermoplastic resin composition may further include 0.3 phr or more of a hydrolysis inhibitor or an antioxidant.

The high-efficiency fiber-reinforced thermoplastic resin composition may further include 0.5 wt% or more of CaCO ₃ or CaO as a dehumidifying functional filler.

The high-efficiency fiber-reinforced thermoplastic resin composition may further include 3 wt% or more of maleic anhydride-grafted polypropylene resin.

The high-efficiency fiber-reinforced thermoplastic resin composition according to the present invention is an eco-friendly composite material, and by including milled lyocell fiber in the thermoplastic resin, it can maximize the physical properties while improving the productivity of the kneading process without using long fibers. there is. In particular, even with the addition of a small amount of lyocell of 0.1 to 30 wt%, the elastic modulus can be improved while maintaining the same level of flexural strength and tensile strength.

In addition, unlike thermosetting resins, the thermoplastic resin of the high-efficiency fiber-reinforced thermoplastic resin composition according to the present invention is eco-friendly because it can be repeatedly softened, molded, and reused by applying heat and pressure due to its molecular structure, and Lyocell is rayon ), it is an eco-friendly material that can replace conventional rayon fibers, has a simple manufacturing process, is harmless to the environment and human body, and has excellent shape stability.

Figure 1 shows the volume fraction conversion calculation method for the resin used in an embodiment of the present invention.
2 is a photograph of a continuous fiber mixer (bumbury's mixer) kneading and a high-efficiency fiber-reinforced thermoplastic resin composition in an embodiment of the present invention.
3 is a photograph of the Bumbury mixer kneading of lyocell fiber powder and a high-efficiency fiber-reinforced thermoplastic resin composition in an embodiment of the present invention.
Figure 4 shows (a) thermal decomposition characteristics and TGA curves of lyocell fabrics and (b) heat shrinkage behavior and TMA curves of lyocell fibers [Polymer (Korea), Vol. 42, no. 1, p. 125-132 (2018)].
5 is a photograph of a molded article of a high-efficiency fiber-reinforced thermoplastic resin composition for each thermoplastic resin in an embodiment of the present invention [(a) PP/Lyocell fiber powder, (b) PLA/Lyocell fiber powder, (c) PA6/ PLA/Lyocell fiber powder].
Figure 6 shows the modulus vs. the high-efficiency fiber-reinforced thermoplastic resin composition of PA6/PLA/Lyocell fiber powder in an embodiment of the present invention. It is a graph showing modulus vs. density.
7 is a graph showing Young's modulus by density in an embodiment of the present invention.
8 is a graph of flexural strength versus density of a high-efficiency fiber-reinforced thermoplastic resin composition with PP/Lyocell fiber powder in an embodiment of the present invention.
Figure 9 shows the flexural strength vs. of the PA6/PLA/Lyocell fiber powder high-efficiency fiber-reinforced thermoplastic resin composition in an embodiment of the present invention. It is a graph showing density.
10 shows tensile strength and flexural strength vs. high-efficiency fiber-reinforced thermoplastic resin compositions of PLA/Lyocell fiber powder and PLA/Lyocell fiber having various length distributions in an embodiment of the present invention. It shows the lyocell fiber length.
Figure 11 shows the tensile strength vs. PLA/Lyocell fiber high-efficiency fiber-reinforced thermoplastic resin composition having various length distributions in an embodiment of the present invention. It shows the lyocell fiber length.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present invention, the term "comprises" or "has" is intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

In manufacturing a composite material by mixing lyocell with a general-purpose resin in order to utilize the high specific modulus and specific strength of lyocell fiber, in general, the larger the aspect ratio, the greater the improvement in physical properties of the composite material. This can be maximized when using fibers. Therefore, as a type of lyocell, continuous fibers, staples and chopped fibers with a length of 5 to 100 mm or less are usually mainly used.

However, there are problems in that the manufacturing process of such continuous fiber composites and composite materials using staple fibers is very inconvenient, poor formability, excessively high process cost, and especially high production cost of lyocell raw materials. .

In addition, compared to glass fibers, Lyocell fibers have a characteristic of bending due to lower straightness when dispersed, so even if the aspect ratio of the fibers increases, the positive effect on the physical properties is lowered, and the fiber reinforcement efficiency is lowered, and the decomposition temperature of the Lyocell fibers Although it is generally said to be 300 ℃ or more, in most cases there is a problem that thermal decomposition starts around 200 ℃.

The present invention relates to a high-efficiency fiber-reinforced thermoplastic resin composition that can effectively solve the above problems.

Hereinafter, the present invention will be described in detail.

The present invention is a thermoplastic resin; And it provides a high-efficiency fiber-reinforced thermoplastic resin composition comprising milled lyocell fiber.

The high-efficiency fiber-reinforced thermoplastic resin composition according to the present invention is an eco-friendly composite material, and by including milled lyocell fiber in the thermoplastic resin, it can maximize the physical properties while improving the productivity of the kneading process without using long fibers. there is. In particular, even with the addition of a small amount of lyocell of 0.1 to 30 wt%, the elastic modulus can be improved while maintaining the same level of flexural strength and tensile strength.

The thermoplastic resin may be polypropylene (PP), polylactic acid (PLA), or polyamide 6 (PA6).

In addition to the thermoplastic resin, polylactic acid may be further included. More specifically, when polypropylene or polyamide 6 is used as the thermoplastic resin, polylactic acid may be further included. By further including the polylactic acid, the elastic modulus can be improved, and the processing temperature can be lowered when processing the high-efficiency fiber-reinforced thermoplastic resin composition, thereby preventing deterioration during high-temperature molding of the thermoplastic resin. For example, the thermoplastic resin may be polypropylene, polylactic acid, polyamide 6, polypropylene and polylactic acid, or polyamide 6 and polylactic acid.

In addition to the thermoplastic resin, 5 to 50 wt% of polylactic acid may be further included. For example, the polylactic acid may further contain 8 to 50 wt%, 8 to 40 wt%, or 35 to 50 wt%.

The thermoplastic resin may contain 30 to 99.9 wt%, which is a value excluding the polylactic acid additionally included.

The lyocell fiber powder may contain 0.1 to 30 wt%. For example, the lyocell fiber powder is 0.1 to 20 wt%, 0.1 to 10 wt%, 0.1 to 5 wt%, 0.5 to 30 wt%, 0.5 to 20 wt%, 0.5 to 10 wt% or 0.5 to 5 wt% %, and by including a small amount, the cost ratio can be improved, and the specific modulus and specific strength can be maximized.

The lyocell fiber powder may have a fiber length of 0.1 to 3.0 mm and an aspect ratio of 3 to 200. For example, the fiber length is 0.1 to 2.5 mm, 0.1 to 2.0 mm, 0.1 to 1.0 mm, 0.5 to 3.0 mm, 0.5 to 2.0 mm, 0.5 to 1.0 mm, 1.0 to 3.0 mm, 1.0 to 2.0 mm, or 2.0 to 2.0 mm. 3.0 mm, and the aspect ratio may be 3 to 150, 3 to 100, 3 to 50, 5 to 200, 5 to 100, 5 to 50, 10 to 200, 10 to 100 or 50 to 100.

In the high-efficiency fiber-reinforced thermoplastic resin composition according to the present invention, the lyocell fiber powder has excellent stress resistance of the remaining fiber length, so that it can exhibit appropriate physical properties even without using long fibers, and the productivity of the kneading process of the high-efficiency fiber-reinforced thermoplastic resin composition While improving the physical properties can be improved.

The high-efficiency fiber-reinforced thermoplastic resin composition may further include 0.3 phr or more of a hydrolysis inhibitor or an antioxidant. The thermoplastic resin has a processing temperature of about 190 to 260 ° C. At this processing temperature, the physical properties and appearance can be further improved by adding the hydrolysis inhibitor or antioxidant in consideration of the improvement of the interface and the generation of decomposition radicals at high temperatures. can For example, the hydrolysis inhibitor or antioxidant may be further included in an amount of 0.3 to 1.0 phr.

The high-efficiency fiber-reinforced thermoplastic resin composition may further include 3 wt% or more of maleic anhydride-grafted polypropylene resin. For example, the maleic anhydride-grafted polypropylene resin may further contain 3 to 7 wt% or 5 wt%. Physical properties and appearance can be further improved by adding the maleic anhydride-grafted polypropylene resin, and properties can be improved by increasing the interfacial adhesion with glass or carbon fiber when manufacturing a composite material of the high-efficiency fiber-reinforced thermoplastic resin composition. there is.

The high-efficiency fiber-reinforced thermoplastic resin composition may further include 0.5 wt% or more of CaCO ₃ or CaO as a dehumidifying functional filler.

Unlike thermosetting resins, the thermoplastic resin of the high-efficiency fiber-reinforced thermoplastic resin composition according to the present invention is eco-friendly because it can be repeatedly softened, molded, and reused by applying heat and pressure due to its molecular structure. It is an eco-friendly material that can be replaced and has a simple manufacturing process compared to conventional rayon fibers, is harmless to the environment and human body, and has excellent shape stability.

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

Example

Preparation Example 1: Physical properties of materials

1) Lyocell fiber properties

In this example, Lyocell fiber powder manufactured by Hyosung Co., Ltd. having a fiber density of 1.5 g/cm ³ , a fiber diameter of 10 to 15 μm, and a fiber powder length of 100 to 250 μm was used.

In this embodiment, J-150 of Lotte Chemical was used for polypropylene (PP), and Luminy LX575, a high-temperature, high-viscosity product of Total-Corbion for film extrusion, was used for polylactic acid (PLA). and polyamide 6 (PA6), a product of Hyosung Co., Ltd., which has a relative viscosity of 2.24, was used.

Preparation Example 2: Calculation of proper content of lyocell fiber

The volume fraction conversion calculation method for the resin used is shown in FIG. 1, and the expected physical property comparison constants of the composite composition for each base resin are shown in Table 1 below.

- The proper fiber fraction is to be calculated in the range where physical mixing is possible based on the volume fraction and the fiber fraction (usually 5 to 30%) of conventional composite materials for injection/extrusion.

- When considering the results of physical property analysis of the tested composite material, it is necessary to convert the volume fraction in order to evaluate based on the rule of mixture

- In experiments using Direct LFT (Direct long-fiber thermoplastic), 10 and 20 wt%, which are easy to produce without problems during feeding and injection into the extruder, were decided.

- In the case of milled fiber, chopped fiber, and yarn fiber using a Ribbon Blender Mixer, kneading is performed at 30wt% and 60wt%

[Table 1]

Experimental Example 1: Analysis of dispersion and distribution ability of thermoplastic resin fibers according to Lyocell milled fiber, chopped fiber, and Lyocell long-fiber-reinforced thermoplastic composite (LFT)

As a result of analyzing the torque change according to the temperature and kneading time of Bumbury's mixer [Bumbury's mixer (haake rheomix os)], the torque increased rapidly as the fiber length increased, and the fiber elongation and toughness were high. Shear scissoring (cutting of fibers by shear force in the kneading process) did not occur well during input.

As a result, the aggregation between the continuous fibers was very severe, confirming the difficulty in dispersing the fibers, and pictures of kneading of the continuous fibers in a bumbury's mixer and a high-efficiency fiber-reinforced thermoplastic resin composition are shown in FIG. 2 .

It was found that this agglomeration phenomenon rapidly increased as the length of the fiber increased, and as the length of the fiber increased, the expected reinforcing effect could not be fully expressed, but rather acted as an obstacle to physical properties. The same phenomenon was also shown in the physical property results according to the fiber mixing fraction,

In other words, even if the fraction of fiber increases, it is difficult to realize the expected physical properties, and rather, a phenomenon of increasing physical properties more than expected in a small amount of fiber powder. 3 shows photographs of Lyocell fiber powder kneading with a Bumbery mixer and a high-efficiency fiber-reinforced thermoplastic resin composition.

For the above reasons, in the case of fiber powder, it is easier to induce stable dispersion of fibers than long fibers, and the change (attenuation) of torque over time during kneading was relatively small because the fiber breakage during the mixing process was relatively small.

Experimental Example 2: Derivation of a solution to the feeding problem for each property of lyocell fiber

In the case of lyocell fiber with a length of 5 to 10 mm, unlike milled fiber, it is difficult to manufacture a composite material through a continuous mixing process due to severe cotton aggregation as if it had gone through an open fiber process. As a result of referring to previous studies using cell long fibers, it was found that all of them used a fiber-fiber or fiber-powder mixing and dispersing process through carding/opening. When using this process, it is good to maintain a high aspect ratio, but it is difficult to expect improvement in the physical properties of the composite resin through the ideal mixing between fibers and resin. However, in the case of lyocell fiber, the elongation is not small and the toughness is high, so the attenuation of the fiber length during the kneading process is relatively small. In this way, since the characteristics of high shear scissoring resistance of fibers were understood, in the case of Lyocell having such characteristics, using a Bumbury mixer, etc. provides process convenience and fiber dispersion that can solve the difficulty of fiber input. It was found that the optimization of physical properties through optimization was also greatly advantageous. Through this, it was possible to mix the fiber content up to 60%.

Experimental Example 3: Analysis of Process Characteristics of Lyocell Fiber

1) Moisture content and drying conditions of Lyocell fiber

Referring to Table 2 below, the moisture content of the fiber powder contained about 6% of moisture, so it was low compared to chopped fiber (7%) and continuous fiber (10%), and all fibers had an initial 110 After drying at ° C for 3 hours, the experiment was conducted while storing at 80 ° C (dew point -60 ° C) in a turnvection drying air circulation method.

Wittmann DRYMAX Aton2 F7 dryer, dried under conditions of 110 ° C (dew point -60 ° C) and 80 ° C (dew point -60 ° C), and the moisture content was calculated by comparing the mass before and after drying.

[Table 2]

2) Thermal decomposition characteristics and temperature control during compounding

The characteristics of lyocell fiber were described in a preceding paper [Polymer (Korea), Vol. 42, no. 1, p. 125-132 (2018)].

Figure 4 shows (a) thermal decomposition characteristics of lyocell fabric, TGA curve and (b) heat shrinkage behavior of lyocell fiber, TMA curve [Polymer (Korea), Vol. 42, no. 1, p. 125-132 (2018)].

Referring to FIG. 4, the thermal decomposition characteristics of the lyocell fabric through the TGA curve show that the equivalent product used in this example, lyocell, loses about 1 to 2% in weight after 100 ° C and starts thermal decomposition from around 270 ° C to about It decreased rapidly to 390 °C. The heat shrinkage characteristics through the TMA curve showed about 2% heat shrinkage from 30 to 160℃ (cause: caused by the removal of water molecules), and after slightly expanding at 200℃ or higher, the original dimensions were maintained, and at around 280℃ Dimensional shrinkage occurred due to the onset of thermal decomposition. The final heat shrinkage rate showed a shrinkage rate of 27% around 320 ℃, and the heat shrinkage behavior of TMA was consistent with the weight loss behavior of TGA.

Therefore, for the application to prepare for the experiment in this example, a full-fledged weight loss occurred around 320 ° C., but a steady weight loss was shown even at 300 ° C. or less. At this time, the weight loss is not large, but moisture and gas with high vapor pressure form pores between the molding reinforcement and the interface, and oxidative radical acids generated during the thermal decomposition of carbohydrates (generated as cellulose-based carbohydrates are decomposed) Acetic acid or formic acid, etc.) can reduce physical properties and corrode equipment. Therefore, the lower the molding temperature, the better, and the experiment was conducted to maintain at least 200 ℃ or less.

Experimental Example 4: Analysis of process characteristics of high-efficiency fiber-reinforced thermoplastic resin compositions for each thermoplastic resin (PP, PA6, PLA)

1) PP (poly propylene)/Lyocell fiber powder

Since the molding temperature of PP is 190 to 200 ° C, there was no molding defect problem due to the processing temperature. Physical properties and appearance were further improved by adding anhydride-grafted polypropylene (MAH-PP) resin.

2) PLA (ploy lactic acid) / lyocell fiber powder

It was molded at 190 ° C, which is the processing temperature of PLA, and despite an excessive amount of antioxidants, after adding 20 wt% Lyocell, severe browning and generation of acid gas significantly increased, making it difficult to obtain a good molded product.

3) PA6 (poly amide 6)/Lyocell fiber powder

As a result of attempting injection based on PA6 with a relative viscosity of 2.2, which is usually injected at 230℃ or higher and a maximum of 260℃, as a result of injection as a black boiled viscous liquid as if lyocell was carbonized, in order to lower the injection temperature A stable, high-efficiency fiber-reinforced thermoplastic resin composition maintaining an ivory color was obtained by performing injection at 215° C. by dry blending with 20 wt% PLA.

Pictures of molded products of the high-efficiency fiber-reinforced thermoplastic resin composition for each thermoplastic resin are shown in FIG. 5 [(a) PP/Lyocell fiber powder, (b) PLA/Lyocell fiber powder, (c) PA6/PLA/Lyocell fiber powder].

Instability factors such as hydrolysis and carbonization of resin and generation of acid gas due to thermal decomposition of lyocell were confirmed. As a solution to this problem, stable mixing of resin that can induce a drop in processing temperature to prevent deterioration during molding at high temperatures was found. It is possible to secure formability.

Experimental Example 5: Analysis of measurement data

1) Lyocell fiber powder content/density measurement for each resin used/comparison with theoretical calculation values

Figure 6 shows the modulus vs. PA6 / PLA / Lyocell fiber powder high efficiency fiber-reinforced thermoplastic resin composition. It is a graph showing modulus vs. density, and Table 3 shows the density measurement values for each lyocell fiber powder content/used resin.

As shown in FIG. 6 and Table 3, when comparing Tensile/Flexural modulus by density, it was confirmed that PP-based MAH-PP, PLA addition, etc. showed a value higher than expected in terms of specific elastic modulus. In particular, it was found that the improvement effect by the PP/PLA mixture was very excellent. In terms of the elastic modulus value alone, the PLA-based high-efficiency fiber-reinforced thermoplastic resin composition showed the highest value, but the deviation was also significantly large. This seems to be the result of maintaining the characteristics of PLA, which is highly crystalline.

[Table 3]

2) Comparison of bending properties by lyocell fiber content

Table 4 below shows the flexural modulus (FM) and flexural strength (FS) for each lyocell fiber content.

7 is a graph showing Young's modulus by density, and FIG. 8 is a graph of flexural strength versus density of a high-efficiency fiber-reinforced thermoplastic resin composition made of PP/Lyocell fiber powder.

Referring to FIGS. 7 and 8 , Young's modulus values were plotted for each density and compared with trends in elastic modulus of a virgin resin to which lyocell was not added. As a result, it was confirmed that the performance of improving the specific strength was significantly higher when using a low content of lyocell or in a PP/PLA blended high-efficiency fiber-reinforced thermoplastic resin composition.

[Table 4]

3) Measurement results of flexural strength by lyocell fiber content

9 is an example of the present invention, Tensile / Flexural strength vs. PA6 / PLA / Lyocell fiber powder high-efficiency fiber-reinforced thermoplastic resin composition. It is a graph showing density.

As shown in FIG. 9, when comparing the flexural strengths of only the groups using the PLA/PA6 resin, a section in which the elastic modulus increases linearly with the density was found. In this section, the crystallinity retention ratio of PLA was There is a difference, and accordingly, it is considered to be a section showing a linear increase in flexural strength.

The effect of improving the flexural strength and tensile strength according to the increase in the content of lyocell fiber was not remarkable, and the change in tensile strength was large when a small amount of lyocell fiber was used (1 to 10 wt%). showed no additional physical property improvement effect.

In the case of the tensile and flexural strength of the PLA/Lyocell fiber powder high-efficiency fiber-reinforced thermoplastic resin composition, it was found that the strength rather decreased when the amount of Lyocell fiber increased from 1 wt% to 10 to 20 wt%.

4) Measurement results of tensile strength by lyocell fiber content

Table 5 below shows the results of measuring tensile strength (TS) for each lyocell fiber content.

Referring to Table 5, the tensile strength also exhibited generally the same trend as previously observed in the flexural strength. It is believed that this is a result of the difficulty in controlling the factors of deterioration in physical properties due to interference with crystal formation of PLA, interference with dispersion of lyocell fibers, and generation of decomposition gas, rather than the reinforcing effect obtained by increasing the content of a small amount of lyocell fiber. do.

[Table 5]

5) Specific strength and specific modulus of elasticity by lyocell fiber content

Referring to Table 6 below, even in comparison of specific strength and specific modulus, the most efficient results were obtained when a small amount of lyocell fibers were contained.

[Table 6]

6) Measurement of tensile strength and flexural strength by fiber length of lyocell fiber

Compared to the physical properties of the lyocell fiber powder obtained above, staple fibers and thermoplastic fibers were kneaded between fibers in a carding process, and high-efficiency fiber-reinforced thermoplastic resin compositions obtained by melting and mixing them Experiments by fiber length The results were compared.

It contained the same amount of lyocell fibers of 20 wt%, and all specimens were molded through injection molding.

10 shows tensile strength and flexural strength vs. 20 wt % lyocell fiber high-efficiency fiber-reinforced thermoplastic resin composition having various length distributions based on PLA. It shows the lyocell fiber length.

As shown in FIG. 10, as a result of comparing the tensile strength of the high-efficiency fiber-reinforced thermoplastic resin compositions having fiber lengths of 0.1 mm, 6 mm, 30 mm, and 60 mm, they show a similar level regardless of the length of the fiber, and the bending In the case of strength, the shorter the length of the fiber, the higher the value.

The reason for this unexpected result is that Lyocell fiber has high toughness and does not easily undergo stress fracture, so the longer the fiber length, the more the aggregation of the fiber, which hinders dispersion and poor networking of the reinforcing fibers in the composite material. It is judged to be because it becomes, and in particular, in the case of lyocell, unlike glass fiber or carbon fiber, etc., it was found that the length of the remaining fiber after injection is easily maintained long. That is, in the case of glass fiber, the average length of remaining fibers is less than about 3 mm even if LFT is injected, and in the case of carbon fiber, it is only about 5 to 1/10 of glass fiber.

That is, in the case of lyocell, it was found that the stress resistance of the remaining fiber length was excellent, so that appropriate physical properties could be exhibited even without using long fibers. That is, it is understood that using the lyocell fiber powder as it is can achieve maximization of physical properties while improving the productivity of the kneading process.

7) Comparison of tensile strength by fiber content of Lyocell fiber composite specimens by compression molding

11 is a graph showing tensile strength vs. PLA/Lyocell fiber-reinforced thermoplastic resin compositions having various length distributions and PLA/Lyocell continuous fibers in an embodiment of the present invention. It shows the lyocell fiber length, and Table 9 below shows the measurement result values.

As shown in Figure 11 and Table 7, when comparing the physical properties by content according to the length, it can be seen that the improvement in tensile strength is not large, unlike expected. Even when tested with 50 wt% of Lyocell continuous fiber, considering that the tensile strength is 95 MPa, it is not possible to express a tensile strength of 60 to 70 MPa through 1 to 20 wt% of PLA/Lyocell fiber powder. It was found to be a very effective result.

[Table 7]

Claims (8)

In the high-efficiency fiber-reinforced thermoplastic resin composition,
thermoplastic resin; and
Contains milled lyocell fiber,
The lyocell fiber powder contains 1 to 10 wt%,
The lyocell fiber powder has a diameter of 10 to 15 μm and a length of 100 to 250 μm,
By further including 5 to 50 wt% of polylactic acid in addition to the thermoplastic resin, the modulus of elasticity is improved, and when processing the high-efficiency fiber-reinforced thermoplastic resin composition, the processing temperature can be lowered to prevent deterioration during high-temperature molding of the thermoplastic resin. A high-efficiency fiber-reinforced thermoplastic resin composition.
According to claim 1,
The thermoplastic resin is a high-efficiency fiber-reinforced thermoplastic resin composition, characterized in that polypropylene, polylactic acid, or polyamide 6.
delete delete delete According to claim 1,
A high-efficiency fiber-reinforced thermoplastic resin composition, characterized in that it further comprises 0.3 phr or more of a hydrolysis inhibitor or antioxidant.
According to claim 1,
A high-efficiency fiber-reinforced thermoplastic resin composition further comprising 0.5 wt% or more of CaCO ₃ or CaO as a dehumidifying functional filler.
According to claim 1,
A high-efficiency fiber-reinforced thermoplastic resin composition, characterized in that it further comprises 3 wt% or more of maleic anhydride-grafted polypropylene resin.