KR102397128B1 - Functionalized cellulose nanocrystal and composites including the same - Google Patents

Abstract

The present invention relates to a surface-modified cellulose nanocrystal and a method for producing the same, and more particularly, to a cellulose nanocrystal having a surface modified with an alkyl group, characterized in that the compound represented by Formula 1 and cellulose form an ester bond will be. In addition, the present invention relates to a polymer composite material using the cellulose nanocrystal whose surface is modified with the alkyl group as an additive. When the surface-modified cellulose nanocrystals according to the present invention are used as an additive to a polypropylene composite material, the physical, chemical, and mechanical properties of the composite material can be greatly improved, and thus it is expected to be widely applied in various industrial fields.

Description

Cellulose nanocrystal with surface modification and composite material including the same

The present invention relates to a surface-modified cellulose and a method for preparing the same, and more particularly, to a cellulose nanocrystal whose surface is modified with an alkyl group. In addition, the present invention relates to a polymer composite material using the cellulose nanocrystal whose surface is modified with the alkyl group as an additive.

Nanocellulose refers to nano-micro-sized cellulose bundles and can be obtained from wood pulp or plants. Nanocellulose can be classified into cellulose nanofibers, cellulose nanocrystals, etc., cellulose nanofibers are several tens of micrometers in length, but cellulose nanocrystals are rod-shaped crystals with a length of 100 to 700 nanometers. There is a difference.

On the other hand, the surface of the cellulose nanocrystal has many hydroxyl groups, so it can be modified with various compounds to obtain desired physical properties. In the compounds grafted to these hydroxyl groups, studies are being actively conducted not only on small molecules but also on methods of replacing them with polymers.

In addition, cellulose nanocrystals are made of crystals and have strong rigidity. They can be added to other polymer matrices as additives to enhance the mechanical properties of polymer materials, and have been spotlighted as a material that can replace existing nanocomposites. there is.

However, in order for cellulose nanocrystals to become an excellent material as an additive, it needs to be effectively dispersed in a polymer material. Moreover, since the cellulose nanocrystals have hydrophilic properties due to the hydroxyl groups on the surface, in order to improve dispersibility, the surface in which a large number of hydrophilic hydroxyl groups are distributed must be modified to be hydrophobic.

In this regard, Korean Patent Application Laid-Open No. 10-2018-0104279 proposes a polymer composite in which diethylenetriamine-functionalized maleated anhydrous polypropylene is prepared and mixed with cellulose nanocrystals to introduce a polymer on the surface of cellulose nanocrystals and Japanese Patent Application Laid-Open No. 2019-520493 proposes an invention in which hydrophobicity is improved by synthesizing a styrene-modified copolymer and introducing it into cellulose.

Korean Patent Laid-Open Patent No. 10-2018-0104279 (Published on 18.09.20) Japanese Patent Application Laid-Open No. 2019-520493 (published on July 18, 19)

The surface-modified cellulose of the present invention has been devised to solve the above problems, and an object of the present invention is to provide a surface-modified cellulose in which a compound having an alkyl group and cellulose form an ester bond.

In addition, the present invention provides a method for producing the surface-modified cellulose comprising the steps of (A) forming a carboxyl group in a phenol-based compound represented by the following Chemical Formula 2; And (B) inducing an ester reaction between the product of step (A) and cellulose to modify the cellulose surface; it is another object to provide a manufacturing method comprising a.

In addition, another object of the present invention is to provide a polymer composite material comprising the surface-modified cellulose as an additive to the polymer as a base material.

The present invention may also have the object of achieving these objects and other objects that can be easily derived by a person skilled in the art from the general description of the present specification in addition to the above clear objects.

The surface-modified cellulose of the present invention is characterized in that in order to achieve the object as described above, the compound represented by the following formula (1) or an ester derivative thereof and cellulose form an ester bond, and the crystallinity of the cellulose nanocrystals is 50 or more do.

[Formula 1]

In Formula 1,

Wherein R ¹ is a linear or pulverized saturated or unsaturated hydrocarbon having 8 to 40, or 10 to 34, or 12 to 30 carbon atoms,

The R ² may be alkyl or alkenyl having 1 to 4 carbon atoms.

And, R ¹ may be a straight-chain alkyl group.

And, R ² may be ethyl or ethenyl.

And, the crystallinity of the cellulose nanocrystals may be 60 or more, or 70 or more, or 80 or more, or 85 or more.

In addition, the cellulose nanocrystals may have an aspect ratio of 1 to 50, or 2 to 40, or 5 to 30.

In addition, the cellulose nanocrystals may have an average diameter of 1 to 30 nm, or 2 to 25 nm, or 2 to 20 nm, and a length of 10 to 1000 nm, or 100 to 900 nm, or 200 to 800 nm.

In addition, the surface-modified cellulose may include 45 to 68 wt%, or 50 to 64 wt%, or 52 to 58 wt% of the carbon element among the elements constituting the surface-modified cellulose.

On the other hand, the surface-modified cellulose manufacturing method of the present invention,

(A) forming a carboxyl group in the phenol-based compound represented by the following formula (2); and

(B) modifying the cellulose surface by inducing an ester reaction between the product of step (A) and cellulose; comprising, and characterized in that the crystallinity of the cellulose nanocrystals is 50 or more.

[Formula 2]

In Formula 2,

Wherein R ¹ may be a linear or pulverized saturated or unsaturated hydrocarbon having 8 to 40, or 10 to 34, or 12 to 30 carbon atoms.

And, R ¹ may be a straight-chain alkyl group.

And, before the step (A), preparing a crystalline cellulose nanocrystal by treating the amorphous cellulose with an acid; may further include, wherein the acid may be sulfuric acid or hydrochloric acid.

In addition, in step (A), the phenol-based compound may be reacted with an acid anhydride.

And, the acid anhydride may be dicarboxylic acid anhydride, preferably succinic anhydride or maleic anhydride.

And, the crystallinity of the cellulose nanocrystals may be 60 or more, or 70 or more, or 80 or more, or 85 or more.

In addition, the cellulose nanocrystals may have an aspect ratio of 1 to 50, or 2 to 40, or 5 to 30.

And, the cellulose nanocrystals may have an average diameter of 1 to 30 nm, or 2 to 25 nm, or 2 to 20 nm, and a length of 10 to 1000 nm, or 100 to 900 nm, or 200 to 800 nm.

And, the phenol-based compound may be cardanol or reduced cardanol.

And, the phenol-based compound may be extracted from cashew nuts.

And, the step (A) may be performed at 20 to 50 ℃, or 24 to 40 ℃, or 28 to 34 ℃.

And, the step (A) may be reacted for 1 to 4 hours, or 1.4 to 3 hours, or 1.8 to 2.2 hours.

And, the step (B) may be performed at 100 to 140 ℃, or 110 to 130 ℃, or 115 to 125 ℃.

And, the step (B) may be reacted for 19 to 28 hours, or 20 to 27 hours, or 22 to 26 hours.

In addition, the step (B) may be carried out in the presence of an acid catalyst.

And, the acid catalyst may be selected from the group consisting of paratoluenesulfonic acid, sulfuric acid, Lewis acid, and mixtures thereof.

On the other hand, the polymer composite material of the present invention is characterized in that the surface-modified cellulose of the present invention is dispersed in the base polymer.

In addition, the polymer composite material may include 100 parts by weight of the base polymer and 0.1 to 25 parts by weight, or 0.5 to 20 parts by weight, or 1 to 12 parts by weight of the surface-modified cellulose.

In addition, the base polymer may be selected from the group consisting of polyolefin, polyvinyl chloride, polystyrene, and mixtures thereof.

And, the base polymer may be polyethylene, polypropylene, polyvinyl chloride, or polystyrene.

The surface-modified cellulose according to the present invention has excellent dispersibility with respect to polymers such as polypropylene, so that when used as an additive for a composite material, the mechanical properties of the composite material can be greatly improved, and the amount required to improve the physical properties can be reduced. there is.

In addition, according to the surface-modified cellulose manufacturing method of the present invention, it is economically advantageous, eco-friendly, and can modify the surface of cellulose nanocrystals in large quantities using inexpensive natural materials. Industrial application as a polymer composite material can be easily achieved.

In addition, the polymer composite material of the present invention to which the surface-modified cellulose of the present invention is added as a filler has good physical and chemical stability, and in particular, flexural strength and tensile strength are improved to exhibit excellent mechanical properties. It is very economical because the amount of additives can be reduced.

1 is a reaction scheme showing a method for producing a surface-modified cellulose according to an embodiment of the present invention.
2 is a flexural test evaluation result of a polymer composite material according to an embodiment and a comparative example of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.

However, the present invention is not limited to the specific exemplary embodiments, since the following is merely a detailed description by exemplifying specific embodiments, and since the present invention may be variously changed and may have various forms. It should be understood that the present invention includes all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In addition, in the following description, many specific details such as specific components are described, which are provided to help a more general understanding of the present invention, and it is common in the art that the present invention can be practiced without these specific details. It will be self-evident to those who have the knowledge of And, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

And, the terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

In this application, the singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as 'comprise', 'contain' or 'have' are intended to refer to the presence of a feature, component (or component), etc. described in the specification, but one or more other features or It does not mean that the component or the like is not present or cannot be added.

The present invention relates to a cellulose-based material that can be used as an additive to a composite material having a polymer as a base material, such as polypropylene. Cellulose nanocrystal (CNC), which is one of the cellulosic materials, has a hydrophilic property due to the abundance of hydroxyl groups on its surface, and thus generally has low dispersibility in polymers such as polypropylene. In order for additives (fillers) such as cellulose nanocrystals, which are added to improve the physical properties of the material, to effectively function, it can be said that dispersibility is the most important for the base material.

Accordingly, the present invention improves hydrophobicity by modifying the hydroxyl groups abundant on the surface of cellulose nanocrystals with an alkyl group through an esterification reaction in order to evenly disperse cellulose nanocrystals (CNC), which is an additive, in a base material. made it

Further, in the present invention, the cellulose nanocrystals have an average diameter of 1 to 30 nm, or 2 to 25 nm, or 2 to 20 nm, and a length of 10 to 1000 nm, or 100 to 900 nm, or 200 to 800 nm, , the aspect ratio may be 1 to 50, or 2 to 40, or 5 to 30. Such crystalline cellulose is characterized by superior mechanical properties compared to general cellulose resins or cellulose nanofibers, and the cellulose nanocrystal additive with improved hydrophobicity by modifying it is used to strengthen the physical properties of composite materials even with a small amount due to excellent interfacial properties. can contribute greatly.

In particular, the surface-modified cellulose nanocrystals of the present invention are characterized in that the compound represented by the following formula (1) and cellulose form an ester bond. In the present invention, the cellulose nanocrystal (crystalline nanocellulose) is a crystal obtained by dissociating amorphous cellulose by treating cellulose with a strong acid such as hydrochloric acid and sulfuric acid, and has very strong mechanical properties compared to cellulose resin or fibrous cellulose. It may mean a material that has and is small in size. Accordingly, the cellulose nanocrystals of the present invention may have a degree of crystallinity (%) of 50 or more, preferably 60 or more, or 70 or more, or 80 or more, or 85 or more, and may be highly crystalline cellulose nanocrystals. In addition, although there is no particular upper limit, it may preferably have a crystallinity of 99 or less, 98 or less, or 95 or less.

In the surface-modified cellulose nanocrystal of the present invention, an ester bond can be formed through an ester reaction or transesterification reaction between a hydroxyl group present on the surface of the cellulose nanocrystal and a carboxyl group of a compound represented by the following formula (1) or an ester derivative thereof. there is.

In Formula 1, R ¹ is a linear or pulverized saturated or unsaturated hydrocarbon having 8 to 40, or 10 to 34, or 12 to 30 carbon atoms, and R ² is alkyl or alkenyl having 1 to 4 carbon atoms, or ethyl or ethenyl.

The carboxylic acid compound represented by Formula 1 is characterized in that it includes a hydrocarbon chain represented by R ¹ , which is a long chain having 8 to 40 carbon atoms, or 10 to 34, or 12 to 30 carbon atoms, which reduces the hydrophobicity of cellulose. serves to improve When the carbon number of R ¹ is less than the above range, the compatibility between the cellulose nanocrystals and the base polymer is not improved, so the effect of increasing the physical properties of the composite material is insignificant. In particular, R ¹ may be a straight-chain unbranched alkyl group, and when R ¹ is an unsaturated hydrocarbon, 1 to 6, or 1 to 5, or 1 to 4, or 1 to 3 double bonds may be included. .

The surface-modified cellulose nanocrystals of the present invention may include 45 to 68 wt%, alternatively 50 to 64 wt%, or 52 to 58 wt% of the carbon element among the elements constituting the same. This is a result of the surface being modified with an alkyl group to increase the specific gravity of the carbon element.

In the surface-modified cellulose nanocrystal additive according to the present invention, the surface of the crystalline nanocellulose is functionalized with hydrophobicity, so that the dispersibility of the polypropylene as the base material can be greatly improved, and the physical properties of the composite material are excellent even when a small amount is added. can do.

On the other hand, the surface-modified cellulose manufacturing method of the present invention comprises the steps of (A) forming a carboxyl group or an ester group in a phenol-based compound represented by the following Chemical Formula 2; and (B) modifying the cellulose surface by inducing an ester reaction between the product of step (A) and cellulose nanocrystals. In this case, the cellulose nanocrystals may have a crystallinity of 50 or more.

In Formula 2, R ¹ may be a linear or pulverized saturated or unsaturated hydrocarbon having 8 to 40 carbon atoms, or 10 to 34, or 12 to 30 carbon atoms.

Hereinafter, each step will be described in detail.

First, a carboxyl group or an ester group is formed in the phenol-based compound represented by Formula 2 (step (A)). The phenol-based compound is characterized in that it has a long hydrocarbon chain, such as R ¹ , wherein R ¹ may be a straight-chain alkyl group.

The carboxyl group can be easily formed by reacting the phenol-based compound with an acid anhydride. In this case, the acid anhydride may be a carboxylic acid anhydride, preferably succinic anhydride or maleic anhydride.

In addition, the phenol-based compound may be cardanol or reduced cardanol, and cardanol can be extracted from cashew nuts, a natural material, which is economical and environmentally friendly. The reduced cardanol may mean reducing all or part of unsaturated bonds in a substituent having cardanol through a hydrogenation reaction or the like.

Specifically, the phenol-based compound may be 3-pentadecyl phenol. 3-pentadecylphenol is one of the materials in which the double bond of cardanol, the main component of cashew bark extract, has been reduced. Since the long chain of 15 carbon atoms is connected to phenol, it is suitable for hydrophobically modifying the surface. However, since phenol has too low reactivity to the esterification reaction, it undergoes a pretreatment step as in step (A) to change it to a carboxyl group.

And, the step (A) may be performed at 20 to 50 ℃, or 24 to 40 ℃, or 28 to 34 ℃. And, the step (A) may be reacted for 1 to 4 hours, or 1.4 to 3 hours, or 1.8 to 2.2 hours. When the reaction temperature is less than the above range, the reaction time is prolonged, thereby deteriorating the economic feasibility of the process, and when it exceeds the above range, side reactants may be generated. In addition, when the reaction time is less than the above range, a large amount of unreacted substances may remain, and when the reaction time is above the above range, the economic feasibility of the process may deteriorate.

In addition, when performing step (A), 4-dimethylaminopyridine (DMAP) and trimethylamine (TEA) may be further included, and methylene chloride (MC) may be used as a solvent. In addition, the method may further include washing and removing the solvent after the reaction of step (A).

As described above, the present invention provides an additive for improving the mechanical properties of polypropylene composite materials using crystalline nanocrystal (CNC) and 3-pentadecylphenol (PDP) obtained from pulp and cashew nut shell extracts, which are natural products, respectively. It contains information about the invention. As an embodiment of the present invention, the step (A) may proceed as in the first reaction of FIG. 1 .

Next, the cellulose surface is modified by inducing an ester reaction between the product (modifier) of step (A) and cellulose nanocrystals (step (B)). The esterification reaction refers to an esterification reaction or a transesterification reaction.

The present invention may further include the step of preparing a crystalline cellulose nanocrystal by treating the amorphous cellulose with an acid before the step (A), wherein the acid treatment is It may be carried out with a strong acid such as sulfuric acid or hydrochloric acid. The cellulose nanocrystals prepared in this way, the cellulose nanocrystals may have an aspect ratio of 1 to 50, or 2 to 40, or 5 to 30, and an average diameter of 1 to 30 nm, or 2 to 25 nm, or 2 to 20 nm and may have a length of 10 to 1000 nm, or 100 to 900 nm, or 200 to 800 nm. Cellulose nanocrystals as described above have excellent mechanical properties, so that when added as an additive to a polymer composite material, the mechanical properties of the polymer can be remarkably improved.

The step (B) is a step of performing an ester reaction of a carboxylic acid or an ester derivative thereof with a hydroxyl group, and can be easily carried out under an acid catalyst without generating toxic by-products, through which the cellulose nanocrystal surface is modified in large quantities can do. In particular, the step (B) may be performed in the presence of p-toluenesulfonic acid (PTSA). In this case, the acid catalyst may be selected from the group consisting of paratoluenesulfonic acid, sulfuric acid, and mixtures thereof, and a Lewis acid may be used.

And, the step (B) may be performed at 100 to 140 ℃, or 110 to 130 ℃, or 115 to 125 ℃. And, the step (B) may be reacted for 19 to 28 hours, or 20 to 27 hours, or 22 to 26 hours. If the reaction temperature is less than the above range, the esterification reaction may not proceed well. In addition, if the reaction time is less than the above range, the amount of alkyl group grafted to the surface of the cellulose nanocrystals may not be sufficient, so the improvement of the physical properties of the composite material may be insignificant, and if it exceeds the above range, economic efficiency of the process may deteriorate.

After the reaction proceeds in step (B), the product may be filtered and dried to obtain a final product. As an embodiment of the present invention, in step (B), the same reaction as in the second of FIG. 1 may be in progress.

On the other hand, the polymer composite material of the present invention is characterized in that the surface-modified cellulose of the present invention is dispersed in the base polymer. In particular, the polypropylene composite material using the modified cellulose nanocrystal according to the present invention as an additive can exhibit very good mechanical properties and thermal stability. The surface-modified cellulose nanocrystal of the present invention is economically very advantageous because it can significantly improve the physical properties of the polymer composite material even with a very low amount, which is because the dispersibility to the base polymer is very excellent by modifying the additive. .

The polymer composite material includes 100 parts by weight of the base polymer and 0.1 to 25 parts by weight of the surface-modified cellulose, or 0.5 to 20 parts by weight, or 1 to 12 parts by weight, or 1 to 10 parts by weight, or 1 to 5 parts by weight. may include wealth. When the content of the surface-modified cellulose filler is less than the above range, the physical properties of the polymer composite material cannot be sufficiently improved, whereas when it exceeds the above range, the physical properties of the polymer composite material can be rather reduced.

In addition, the base polymer may be selected from the group consisting of polyolefins such as polyethylene or polypropylene, polyvinyl chloride, polystyrene, and mixtures thereof, and in particular, the effect of the modified cellulose of the present invention on polypropylene can be maximized. there is.

On the other hand, the polymer composite material of the present invention can be prepared by a known method for producing a polymer composite material, in particular, mixing the surface-modified cellulose nanocrystals of the present invention and a polyolefin-based polymer and extruding and molding the mixture can be manufactured. The extrusion may be performed at 160 to 280 ℃, or 180 to 260 ℃, or 190 to 220 ℃, 80 to 220 rpm, 90 to 210 rpm, 95 to 200 rpm using a twin screw extruder. In addition, the molding may be performed using an injection molding machine, at 160 to 280 ℃, or 180 to 260 ℃, or 190 to 220 ℃, 20 to 40 bar, 25 to 36 bar, 28 to 32 bar.

Hereinafter, an embodiment of the present invention will be described.

[Example]

Produce Yes 1: Preparation of modifier PDPBA

After dissolving 10.845 g of succinic anhydride (SA) in 200 ml of methylene chloride (MC), it was sonicated for 30 minutes because of its low solubility. Here, 30.000 g of 3-pentadecylphenol (PDP), 13.240 g of 4-dimethylaminopyridine (DMAP), and 10.966 g of triethylamine (TEA) were added together with 25 ml of methylene chloride. This was stirred in an oil bath at 30 °C for 2 hours. After that, it was transferred to a separatory funnel, washed 3 times with 200 ml of 1 M aqueous hydrochloric acid solution, and washed 3 times with 200 ml of 1 M aqueous sodium chloride solution. After receiving the lower layer, the solvent MC was removed using a rotary evaporator. As a result of drying, 35.708 g of product was obtained. The product was named PDPBA(4-oxo-4-(3-pentadecylphenoxy)butanoic acid).

Preparation Example 2: f-CNC manufacturing

5.2 g of cellulose nanocrystals (CNC) were dispersed in 150 ml of toluene by sonication for 30 minutes. Here, 18.111 g of PDPBA prepared in Preparation Example 1 and 0.077 g of p-toluenesulfonic acid (PTSA) were dissolved therein. Then, it was put into an oil bath set at 120 °C and stirred for 24 hours. Using a Dean-Stark trap and a condenser, the water generated by the esterification reaction was controlled not to re-enter the mixed solution. After the reaction, the product was put into 600 ml of hexane, stirred for 10 extra minutes, and then f-CNC, which is modified cellulose, was filtered using a polyvinylidene fluoride (PVDF) filtration membrane having pores of 0.22 μm in size. Excess PDPBA was washed away using a sufficient amount of hexane during the filtration process. As a result of drying the solid content of the upper layer of the filtration membrane, 11.779 g of f-CNC was obtained.

Test Example 1: Elemental Analysis

Elemental analysis was performed on the modified cellulose (f-CNC) and non-cellulose nanocrystals (CNC) prepared by Preparation Example 2, and the results are shown in Table 1 below.

C (wt%) H (wt%) N (wt%) S (wt%) O (wt%) CNC 39.9 5.7 0.0 2.0 52.4 f-CNC 54.7 7.2 0.0 1.5 36.6

In the case of the modified cellulose f-CNC, the carbon content was significantly increased from 39.9 wt% to 54.7 wt%, indicating that the cellulose surface was well modified with long hydrocarbon chains.

Examples 1 to 5: Preparation of polypropylene (PP) composite material PP/f-CNC

Polypropylene (PP) in the form of granules is mixed with f-CNC prepared in Preparation Example 2, but the amount of filler f-CNC is 1 wt%, 3 wt%, 5 wt%, 10 wt%, 20 It was mixed so as to be wt%. These were extruded using a twin-screw extruder, and then pellets were produced. The temperature of the extruder was set at 190, 190, 200, 200, 200, 200, 200 ^° C from the feed to the die, and the screw was rotated at 100 rpm. The produced pellets were extruded at 150 mm/s at 200 °C and 30 bar to prepare a polypropylene composite material specimen conforming to ASTM D638 and D790. These were named as PP/f-CNC-1wt%, PP/f-CNC-3wt%, PP/f-CNC-5wt%, PP/f-CNC-10wt%, and PP/f-CNC-20wt%, respectively.

Comparative Examples 1 to 5: Preparation of polypropylene (PP) composite material PP/CNC

A polypropylene composite material was prepared in the same manner as in Example 1, but using CNC instead of f-CNC as a filler to be 1 wt%, 3 wt%, 5 wt%, 10 wt%, and 20 wt%, each mixed with PP /CNC-1wt%, PP/CNC-3wt%, PP/CNC-5wt%, PP/CNC-10wt%, PP/CNC-20wt% were named.

Test Example 2: Flexural Test

In order to evaluate the mechanical properties of the composite materials prepared by Examples 1 to 5 and Comparative Examples 1 to 5, flexural evaluation was performed with polypropylene (PP) as a control group, and the results are shown in Tables 2, 3, and 2 is the same.

Sample Flexural Modulus (MPa) Flexural Strength (MPa) pp 1432.8 ± 100.9 39.1 ± 0.7 Example 1 1454.4 ± 74.3 45.9 ± 0.6 Example 2 1499.4 ± 59.4 46.0 ± 0.4 Example 3 1604.3 ± 46.9 45.2 ± 0.7 Example 4 1448.5 ± 26.0 42.5 ± 0.1 Example 5 1291.5 ± 71.0 32.5 ± 0.4

Sample Flexural Modulus (MPa) Flexural Strength (MPa) pp 1432.8 ± 100.9 39.1 ± 0.7 Comparative Example 1 1458.3 ± 66.2 41.6 ± 0.4 Comparative Example 2 1443.7 ± 41.1 42.1 ± 0.5 Comparative Example 3 1472.6 ± 88.2 39.9 ± 0.6 Comparative Example 4 1520.3 ± 74.9 40.9 ± 0.5 Comparative Example 5 1738.6 ± 59.8 38.8 ± 0.4

The polymer composite material according to the present invention has improved flexural modulus and flexural strength by including the surface-modified cellulose. In particular, it was found that the performance as a filler of the surface-modified cellulose according to the present invention was excellent through comparison with Comparative Examples including the same amount of filler. Therefore, according to the present invention, it is possible to expect sufficient improvement in physical properties of the composite material even with the addition of a small amount of filler, thereby improving economic efficiency. However, it was confirmed that when the content of the filler was excessive as 20 wt%, the physical properties were rather deteriorated.

Preparation 3 and 4: Preparation of C12 modifier and C18 modifier

A modifier was prepared in the same manner as in Preparation Example 1, except that 3-dodecylphenol and 3-octadecylphenol were used instead of 3-pentadecylphenol to prepare a C12 modifier and a C18 modifier, respectively.

Preparation Examples 5 and 6: Preparation of C12-CNC and C18-CNC

Nanocellulose was modified in the same manner as in Preparation Example 2, but instead of PDPBA prepared in Preparation Example 1, the modifiers prepared in Preparation Examples 3 and 4 were mixed to obtain modified cellulose C12-CNC, C18-CNC, respectively.

Examples 6 to 10: Polypropylene Composite Material PP/C12-CNC Manufacturing

Prepared in the same manner as in Example 1, but using the C12-CNC prepared in Preparation Example 5 as a filler, mixed to 1 wt%, 3 wt%, 5 wt%, 10 wt%, 20 wt%, each It was named as PP/C12-CNC-1wt%, PP/C12-CNC-3wt%, PP/C12-CNC-5wt%, PP/C12-CNC-10wt%, PP/C12-CNC-20wt%.

Examples 11 to 15: Polypropylene Composite Material PP/C18-CNC Manufacturing

Prepared in the same manner as in Example 1, but using the C18-CNC prepared in Preparation Example 6 as a filler, mixing to 1 wt%, 3 wt%, 5 wt%, 10 wt%, 20 wt%, each It was named as PP/C18-CNC-1wt%, PP/C18-CNC-3wt%, PP/C18-CNC-5wt%, PP/C18-CNC-10wt%, PP/C18-CNC-20wt%.

Test Example 3: Flexural Test

In order to evaluate the mechanical properties of the composite materials prepared in Examples 6 to 15, flexural evaluation was performed together with polypropylene (PP) as a control, and the results are shown in Tables 4 and 5 below.

Sample Flexural Modulus (MPa) Flexural Strength (MPa) pp 1432.8 ± 100.9 39.1 ± 0.7 Example 6 1447.3 ± 45.6 43.7 ± 0.8 Example 7 1462.1 ± 37.0 43.8 ± 0.6 Example 8 1581.7 ± 54.3 43.9 ± 0.7 Example 9 1452.1 ± 39.7 40.3 ± 0.3 Example 10 1342.3 ± 51.8 32.0 ± 0.5

Sample Flexural Modulus (MPa) Flexural Strength (MPa) pp 1432.8 ± 100.9 39.1 ± 0.7 Example 11 1460.5 ± 58.9 46.1 ± 0.8 Example 12 1502.5 ± 58.1 46.3 ± 0.6 Example 13 1611.3 ± 48.5 45.8 ± 0.9 Example 14 1478.5 ± 37.2 44.7 ± 0.5 Example 15 1315.9 ± 60.3 35.7 ± 0.7

In the case of including cellulose nanocrystals modified with an alkyl group having more carbon number, it can be seen that the flexural modulus and bending strength are generally more improved, but even in the case of a composite material including a C12-CNC additive, a polypropylene material that does not contain an additive It can be seen that the physical properties are significantly improved compared to . However, it was confirmed that if the content of the filler was excessive as 20 wt%, the physical properties were rather deteriorated.

The polypropylene composite material according to the present invention exhibits excellent mechanical properties and contains a small amount of additives to have excellent economic feasibility, and is expected to be widely applied in various industrial fields.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments described above, and those skilled in the art can implement various modifications without departing from the gist of the present invention. Of course it is possible. Accordingly, the scope of the present invention should not be construed as being limited to the above embodiments, and should be defined by the following claims as well as the claims and equivalents.

Claims (11)

A polymer composite material characterized in that the surface-modified cellulose nanocrystals are dispersed in the base polymer,
The polymer composite material is prepared by extruding after mixing 100 parts by weight of the base polymer and 1 to 12 parts by weight of the surface-modified cellulose nanocrystals,
The surface-modified cellulose nanocrystals are characterized in that the compound represented by the following Chemical Formula 1 or an ester derivative thereof and the cellulose nanocrystals form an ester bond, and the crystallinity of the cellulose nanocrystals is 50 or more, a polymer composite material:
[Formula 1]

In Formula 1,
Wherein R ¹ is a linear or pulverized saturated or unsaturated hydrocarbon having 8 to 40, or 10 to 34, or 12 to 30 carbon atoms,
wherein R ² is —CH2-CH2-. The method according to claim 1,
The cellulose nanocrystals have an aspect ratio of 1 to 50, or 2 to 40, or 5 to 30, polymer composite material. The method according to claim 1,
The cellulose nanocrystals have an average diameter of 1 to 30 nm, or 2 to 25 nm, or 2 to 20 nm, and a length of 10 to 1000 nm, or 100 to 900 nm, or 200 to 800 nm, polymer composites. The method according to claim 1,
The surface-modified cellulose nanocrystals contain 45 to 68 wt%, or 50 to 64 wt%, or 52 to 58 wt% of the carbon element among the elements constituting the surface-modified cellulose nanocrystal, polymer composite material. The method according to claim 1,
The surface-modified cellulose nanocrystals,
(A) forming a carboxyl group or an ester group in the phenol-based compound represented by the following formula (2); and
(B) modifying the surface of the cellulose nanocrystal by inducing an ester reaction between the product of step (A) and the cellulose nanocrystal; characterized in that the crystallinity degree of the cellulose nanocrystal is 50 or more, the step (A) is a polymer composite material, characterized in that prepared by the method for producing surface-modified cellulose nanocrystals, characterized in that the reaction of the phenolic compound with succinic anhydride:
[Formula 2]

In Formula 2,
Wherein R ¹ is a linear or pulverized saturated or unsaturated hydrocarbon having 8 to 40 carbon atoms, or 10 to 34, or 12 to 30 carbon atoms. delete delete 6. The method of claim 5,
The step (B) is characterized in that carried out under an acid catalyst, a polymer composite material. delete delete The method according to claim 1,
The base polymer is a polymer composite material, characterized in that selected from the group consisting of polyolefin, polyvinyl chloride, polystyrene, and mixtures thereof.

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