KR101701568B1 - Thermoplastic polymer film and manufacturing method thereof - Google Patents

Abstract

According to the present invention, since lignin has thermoplastic properties, melt processing is possible, and extrusion and injection can be performed in the production of a film.
It is expected that the demand for biodegradable film can be increased because it can be applied to bags for garbage bag, food packaging, agriculture film, and food packaging film by producing an eco-friendly biodegradable film capable of melt processing.
In addition, blending with existing polymers can increase the environmental friendliness and reduce the cost of materials by using lignin obtained from waste.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a thermoplastic resin film containing lignin,

The present invention relates to a lignin-containing thermoplastic resin film and a method for producing the same.

Lignin, together with cellulose and hemicellulose, constitutes the substantive component of wood and is a polymer of phenylpropanoid present in association with carbohydrates other than cellulose. The chemical structure is a dendritic structure obtained by complicated polymerization using three kinds of phenylpropanoids as constituent units.

Therefore, its chemical structure is not clear, but it is presumed to be between C ₁₈ H ₂₄ O ₁₁ and C ₄₀ H ₄₅ O ₁₈ . Lignin is contained in 25-30% of conifer and 20-25% in hardwood. It is obtained as a by-product in biomass production, Kraft pulp process and so on.

For example, black liquor is waste produced in the process of delignification of wood in the kraft pulping process. Lignin residue, hemicellulose, inorganic compound, etc. are dissolved in the liquid phase in this black solution. Lignin can be extracted from such black liquor.

About 100 million tons / year of black liquor is produced as a by-product in the world, and the disposal of black liquor is very difficult because of its high cost and environmental pollution. The amount of lignin contained in this black liquid is estimated to be very high, about 30 million tons / year.

Currently, more than 99% of the lignin extracted from the world is burning, and only about 1% of lignin is used as a carrier for pesticides, additives for concrete, surfactants, adsorbents, fertilizers, rubber additives, have. However, since lignin is not a thermally stable thermoplastic polymer as a physical additive, its application is not expanded and only a small amount of lignin is utilized at the research level.

The lignin extracted from the black liquor is obtained as a bronze powder. The extracted natural lignin is a thermosetting polymer and has no thermoplastic properties. Even if the temperature rises, the solid lignin maintains a solid state, so melt processing is impossible.

When the extracted lignin is heated, the lignin is discolored into a black powder. That is, when heated, it is not melted, it generates odor and smoke, and remains as a powder. Also, the extracted natural lignin contains molecules with low molecular weight, so when approaching 100 ℃, smoke and odor are generated. Furthermore, since the extracted natural lignin has hydrophilicity, it is not compatible with general polymers, and even when kneaded with a general polymer, excellent physical properties are hardly obtained. Therefore, it is very difficult to produce a lignin-based film through a melting process.

On the other hand, in order to prevent direct sunlight including ultraviolet rays and infrared rays from being irradiated to the room, products for preventing exposure to ultraviolet rays and infrared rays by attaching various blocking films to windowpanes such as automobiles and buildings have been developed and put into practical use . Such a barrier film itself not only shields ultraviolet rays and infrared rays but also functions to complement the mechanical strength of the window glass, to prevent glass fragments from splashing when the window glass is broken, and to protect privacy when applying a colored film And the like.

Examples of such a film include a method of applying a coating resin and a dye diluted with a solvent and an ultraviolet absorber to the cross section of the polyester film, and the like. However, the method of containing a dye has a problem that the ultraviolet ray shielding efficiency is limited to 15 to 25% and the thermal efficiency is also inferior. In the method of containing the ultraviolet ray blocking agent, a process of adding the ultraviolet ray blocking agent is added, There is an increasing problem.

Therefore, researches on films that can block ultraviolet rays by utilizing cheap and eco-friendly materials are being continued.

An object of the present invention is to provide an environmentally friendly thermoplastic resin film which is low in ultraviolet transmittance and can be used for various purposes by using a cheap and environmentally friendly raw material.

The present invention provides a thermoplastic resin film containing modified lignin and having a transmittance of 50% or less with respect to light having a wavelength of 400 nm or less.

The present invention also provides a method for producing a thermoplastic resin film, comprising the steps of: preparing a pellet by melt mixing and extruding a thermoplastic resin and modified lignin with an extruder; and stretching the pellet to prepare a film.

The present invention can dramatically increase the economical efficiency and utility value of a film that can be converted into modified lignin through chemical reaction and improve the compatibility with general polymers to produce a film that can be subjected to a melting process. Specifically, since an eco-friendly biodegradable film capable of melt processing can be produced, it can be used for a trash bag, a household goods package, an agricultural film, a food packaging film, and the like.

Further, the thermoplastic resin film according to the present invention is eco-friendly and excellent in ultraviolet ray shielding effect. In particular, the use of lignin obtained from waste is expected to reduce the cost of materials and increase the environmental friendliness.

Figure 1 is a photograph of a film prepared by varying the content of acetylated lignin.
FIG. 2 is a graph showing the results of measurement of the weight loss of the film produced in the examples using a thermogravimetric analysis (TGA). FIG.
3 is a graph showing mechanical properties of a specimen of Example 1 prepared by varying the content of modified lignin.
FIG. 4 shows the results of comparing the modulus of the specimen of Example 1 using DMA (Dynamic Mechanical Analyzer) analysis.
5 shows the results of measurement of the transmittance of the film produced in the examples.
FIGS. 6 to 9 are graphs showing the relationship between the transmittance and the wavelength measured in FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Natural lignin is a thermosetting polymer with a three-dimensional network structure. It does not have a thermoplastic property. Even if the temperature rises, it does not melt, but generates smoke and odor and remains as a powder. Since lignin contains molecules with low molecular weight, smoke and odor are generated when they approach 100 ° C. Moreover, since lignin has a very large number of hydroxyl reactors, it is not compatible with general polymers, It is difficult to obtain physical properties and it is difficult to melt-process the film.

The present invention solves these problems and provides a thermoplastic resin film excellent in biodegradability and excellent in ultraviolet ray shielding effect based on cheap and environmentally friendly lignin.

Specifically, the film according to the present invention is a thermoplastic resin film containing modified lignin and having a transmittance of 50% or less with respect to light having a wavelength of 400 nm or less.

In particular, the thermoplastic resin film according to one embodiment has a transmittance of 40% or less for light of 400 nm wavelength, a transmittance of 30% or less for light of 300 nm wavelength, and a transmittance of 20% or less for light of 200 nm wavelength .

Also, the thermoplastic resin film according to an embodiment has a ratio (q / p) of a slope (q) of a transmission curve for light with an area wavelength of 300 to 800 nm and a slope (p) of a transmission curve for light with a wavelength of 200 to 300 nm, May be 0.05 or more, preferably 0.1 or more, and may be 10 or less.

In addition, the thermoplastic resin film may have a transmittance that satisfies the following formula (1) for light having a wavelength in the range of 300 nm to 800 nm.

[Equation 1]

y = a ₁ x + b ₁

Wherein, x is the wavelength (nm), y is a transmittance (%), a ₁ is a constant of 0.03 to 0.09, b ₁ is in the 30 to 10 constant.

The film according to one embodiment also has a transmittance that satisfies the following equation (2) for light having an area wavelength of 200 to 300 nm.

&Quot; (2) "

y = a ₂ x + b ₂

Wherein, x is the wavelength (nm), y is a transmittance (%), a ₂ is a constant of 0.003 to 0.5, b ₂ is in the -60 to 10 constant.

The thermoplastic resin film according to the present invention contains modified lignin, and ultraviolet rays and visible light transmittance (or blocking rate) exhibit a specific tendency as described above.

According to one embodiment, the modified lignin may be acetylated lignin or a thermoplastic lignin condensation polymer.

First, the acetylated lignin may be prepared by reacting lignin with acetic anhydride, and the acetylation method may be used without limitation as long as it is known in the art. The substitution of the hydroxyl group of the lignin with the acetyl group can reduce the hydrophilicity of the lignin, improve the dispersibility with other polymers, and prevent self-aggregation due to hydrogen bonding during blending, It can be blended with a resin to form a film.

According to one embodiment, the acetylated lignin can be obtained by dissolving lignin obtained by drying the black solution in pyridine, adding acetic anhydride thereto and reacting at room temperature, slowly dropping the resulting reaction mixture into water, washing and drying .

More specifically, the concentration of lignin dissolved in the pyridine can be from about 0.01 to about 1 g / ml, or from about 0.05 to about 0.5 g / ml. The time for dissolving lignin in pyridine is preferably gradually progressed at room temperature for 0.5 to 2 hours. Acetic anhydride may be added in an amount of about 0.1 to 10 parts by weight, or about 1 to 5 parts by weight, based on 1 part by weight of lignin. The acetylation reaction after the addition of acetic anhydride can proceed for 12 to 36 hours at room temperature. The reaction mixture is preferably precipitated by slowly dropping in cold water at a temperature lower than room temperature, for example, about 10 ° C or below, or about 5 ° C or about 0 ° C, and the precipitate obtained by a conventional separation process such as filtration Can be washed and dried to obtain acetylated lignin.

The acetylation degree of lignin is preferably about 50% or more. Specifically, for example, the number of hydroxyl groups contained in the lignin molecule differs depending on the molecular weight, and when the molecular weight of the lignin obtained through the crafting process is in the range of about 2,000 to 3,000, it has about 15 to 20 hydroxyl groups Of these, about 7 or more hydroxyl groups are preferably acetylated.

On the other hand, the thermoplastic lignin-condensation polymer may be obtained by reacting a lactone compound with lignin as disclosed in Korean Patent No. 10-1336465 filed and filed by the present applicant and International Application No. PCT / KR2013 / 008095.

Specifically, an intermediate is prepared by reacting a lactone-based compound with lignin, and the intermediate is subjected to an ester condensation reaction with a reactant having two or more acid reactors selected from dichloroacid, acid dianhydride, and divalent acid to obtain a thermoplastic lignin- Can be manufactured. Since details of the above-mentioned patent of the present applicant are disclosed, a detailed description thereof will be omitted here.

According to one embodiment, the thermoplastic resin film may comprise from about 1 to about 50 weight percent modified lignin, based on the total weight of the film. Preferably, from about 2 to about 40 weight percent, or from about 3 to about 35 weight percent, or from about 3 to about 30 weight percent, or from about 4 to about 30 weight percent, or from about 5 to about 25 weight percent, By weight of modified lignin.

The thermoplastic resin is not particularly limited as long as it is a commercial resin capable of forming a film by melt processing. Examples of the thermoplastic resin include polypropylene, polyethylene, polyphenylene sulfide, polyvinyl chloride, polyethylene terephthalate, nylon, polyurethane, polycarbonate, And may be selected from the group consisting of polystyrene, polyvinyl alcohol, polyvinyl acetate, poly (meth) acrylate, polylactic acid, polyvinylidene chloride, and mixtures thereof. Particularly, it is preferable to produce a film by kneading polyethylene such as low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) together with modified lignin.

According to a preferred embodiment, the weight average molecular weight of the thermoplastic resin may be about 4,000 or more and about 600,000 or less, but it is not limited thereto and may be used as long as it has a molecular weight enough to be processed into a film.

It may further contain other organic or inorganic additives such as fillers, flame retardants, antistatic agents, nucleating agents, colorants, lubricants, anti-blocking agents and plasticizers and the like which are conventionally used in the art depending on the physical properties required for the film. In particular, it can be used for blending by using eco-friendly hemp fibers, fibers obtained from natural materials such as bamboo fibers, and cellulose fibers as reinforcing agents in order to improve mechanical properties and flame retardancy.

Examples of the inorganic additive include hydrogen compounds, oxides, oxygen acids, hydrides, halides, sulfates, nitrates, carbonates, nitrates and metal complexes (coordination compounds). Examples of the carbonaceous materials include graphite, Nanotubes, and carbon black. Examples of the metal include sodium, magnesium, potassium, calcium, and the like. However, the present invention is not limited thereto, and various materials can be used in consideration of the use of the composite material and the process conditions.

The thermoplastic resin film as described above can be produced by a conventional thermoplastic film resin production process. Specifically, the thermoplastic resin and the modified lignin may be melt-mixed and extruded by an extruder to produce a pellet, and the extruded pellet may be stretched to produce a film.

The thermoplastic resin and modified lignin can be melt-mixed at a weight ratio of 50 to 99: 50 to 1, and melt mixing can be performed at a temperature of about 110 to 250 ° C using a twin-screw extruder. It is preferred to make the blend in pellet form using a twin-screw extruder.

The twin-screw extruder can be of any type that is conventional in the art to which the present invention pertains, and therefore the constitution thereof is not particularly limited. However, in order to produce a lignin melt having a higher homogeneity, the biaxial extruder preferably comprises about 7 to 12 blocks, and the ratio of the length / diameter (L / D) of each block is about 2 to 6 . The temperature condition of the biaxial extruder may be determined in consideration of other process conditions such as the thermal properties of the lignin raw material used, the rotation speed of the screw, the discharge speed of the melt, and preferably about 60 to 200 ° C, It is preferable to adjust the temperature of each block constituting the extruder independently in the range of about 60 to 200 DEG C in accordance with the characteristic of the corresponding section. In order to sufficiently melt / knead the powdery lignin, the screw rotation speed of the biaxial extruder is preferably about 120 rpm or more, more preferably about 120 to 500 rpm.

The pellets produced using the twin-screw extruder can be re-blended and melted at a temperature of about 110 to 250 ° C and processed into sheet form through the T-die. The sheet may be stretched to produce a film having desired thickness and physical properties.

The sheet thickness can be about 15 to 400 microns and can be uniaxially or biaxially stretched at a stretch ratio of about 1 to 25. [

Films according to one embodiment have a thickness of about 100 microns or less and can be used without limitation in all applications used in film applications.

Hereinafter, the embodiments of the present invention will be described more specifically. However, the present invention is not limited thereto.

Preparation Example 1 Preparation of acetylated lignin

1 g of lignin was completely dissolved in 10 ml of pyridine solution at room temperature for 1 hour. Then, 3.5 g of acetic anhydride was added slowly, and the mixture was reacted for 24 hours with stirring. The resulting reaction mixture was slowly dropped into water maintained at 0 占 폚 to form a precipitate. The precipitate was filtered, washed, and dried to obtain 1.2 g of acetylated lignin.

Production Example 2 Production of Thermoplastic Lignin Concentrate Polymer

[CO] / [OH] lignin, followed by the addition of caprolactone (CL) to the lignin solution so that the [CL] / [OH] lignin, SC) solution was mixed with the lignin-based polycaprolactone at room temperature. Triethylamine (TEA) (TEA / SC molar ratio 1) was added slowly while vigorously stirring the mixture. The reaction mixture was maintained at 120 < 0 > C, filtered, washed with water and dried.

The lignin-condensation polymer thus prepared had a weight average molecular weight of 10,500 and a glass transition temperature of 143 占 폚. The melt viscosity at 180 DEG C was confirmed to be less than 10,000 Pa.s.

≪ Example 1 >

The modified lignin prepared in Preparation Examples 1 and 2 was mixed with low density polyethylene (LG Chem, LB7500) in the weight ratio composition shown in Table 1, dried in an oven at 80 ° C for 3 hours, and then melt-mixed extruded at 150 ° C with an extruder To prepare pellets. The pellets thus prepared were dried at 80 DEG C for 3 hours, remultiplexed at 200 DEG C and uniaxially stretched 8 times through a T-die to obtain a film having a thickness of 50 mu m.

division Low density polyethylene (PE) Modified lignin PE 100 0 LPE5 95 5 LPE10 90 10 LPE20 80 20

2 is a photograph of a film using acetylated lignin prepared in Production Example 1 as a modified lignin. It was confirmed that even if the content of acetylated lignin was 20 wt%, film processing was possible.

2 is a graph showing the weight loss of the film according to the content of acetylated lignin using a thermogravimetric analysis (TGA) method. From the above results, even if the content of modified lignin is increased up to 20 wt%, it is found that a general melting process is possible with a 2 wt% decomposition temperature of 330 ° C. In the graph,% represents the modified lignin content based on the total weight of the film.

3 is a graph comparing the mechanical properties of the film specimens prepared in Example 1 by varying the content of modified lignin.

FIG. 4 is a dynamic mechanical analyzer (DMA) analysis graph showing that when the modified lignin content according to the present invention is variously varied, the elastic modulus of the specimen prepared with modified lignin is higher than that of pure LDPE Able to know.

5 shows the results of measuring the transmittance of the film according to the acetylated lignin content. The transmittance was measured using a UV-VIS / NIR (ultraviolet-visible light / near-infrared spectrometer). The results of FIG. 5 are shown in Table 2.

division 200 nm 250 nm 300 nm 350 nm 400 nm 500 nm 600 nm 700 nm 800nm PE 1.935 61.195 70.543 75.709 77.970 80.541 81.955 82.869 83.545 LPE5 1.063 21.791 26.544 32.487 37.953 45.647 53.004 58.655 62.980 LPE10 0.679 13.337 16.748 21.271 26.316 34.537 42.785 49.090 53.938 LPE20 0.005 0.347 0.488 0.707 1.529 5.025 10.685 16.199 20.903

As can be seen from FIG. 5, in the case of a film (PE) containing no modified lignin at all, the transmittance increases sharply in the wavelength range of 200 to 300 nm (i.e., the cut-off rate decreases), whereas a predetermined amount of modified lignin (LPE5, LPE10, LPE20), the transmittance is gradually increased, that is, the blocking rate is maintained to some extent. In particular, a film containing 20% of modified lignin can be confirmed to have a blocking rate of almost 99% up to 400 nm.

Specifically, as can be seen from Figs. 6 to 9, the transmittance according to the wavelength range exhibits the following relational expression.

200-300 nm
Slope p 300-800 nm
Slope q Slope change (q / p) PE y = 0.69x-127 y = 0.023x + 67.3 0.033 LPE5 y = 0.255x-47.2 y = 0.072x + 7.6 0.28 LPE10 y = 0.16x-29.9 y = 0.076x-4.6 0.48 LPE20 y = 0.0048x-0.9 y = 0.043x-14.6 8.96

In the equation of Table 3, x is the wavelength (nm) and y is the transmittance (%).

From the above results, it can be seen that the film containing modified lignin according to the present invention has a transmittance that satisfies the following formula (3) for light having an area wavelength of 300 to 800 nm.

 &Quot; (3) "

y = a ₃ x + b ₃

Wherein, x is the wavelength (nm), y is a transmittance (%), a ₃ is a constant of 0.03 to 0.09, b ₃ is a constant of -20 to 10.

Further, it can be seen that the light having a wavelength in the range of 200 nm to 300 nm has a transmittance satisfying the following expression (4).

&Quot; (4) "

y = a ₄ x + b ₄

X is a wavelength (nm), y is a transmittance (%), a ₄ is a constant of 0.003 to 0.5, and b ₄ is a constant of -50 to 0.

As described above, according to the present invention, when approaching 100 ° C., smell and smoke are generated, and the lignin which is discolored into a black powder and does not melt and remains in a solid state is chemically modified to enhance compatibility with the polymer resin, Since the physical properties of the film are comparable to those of the general commercial polymeric resin film, it is expected to contribute to the cost reduction of the industrial film. Further, since the film thus produced has excellent ultraviolet shielding effect, it can be used for various purposes .

Claims (12)

Dissolving lignin in pyridine at a concentration of 0.01 to 1 g / ml;
Stirring the lignin dissolved in the pyridine to a content ratio of acetic anhydride of 0.1 to 10 parts by weight based on 1 part by weight of lignin to prepare acetylated lignin;
Mixing the thermoplastic resin with 1 to 20% by weight of the acetylated lignin so that the total weight of the composition is 100% by weight;
Mixing and extruding the blend with an extruder to produce a pellet; And
And extruding the pellets followed by stretching to produce a film,
The degree of acetylation of the acetylated lignin is 50% or more,
Wherein the film has a transmittance of 50% or less with respect to light having a wavelength of 400 nm or less. The method according to claim 1,
Wherein the transmittance to light of 400 nm wavelength is 40% or less, the transmittance to light of 300 nm wavelength is 30% or less, and the transmittance to light of 200 nm wavelength is 20% or less. The method according to claim 1,
Wherein a ratio (q / p) of a slope (q) of a transmittance curve to a light having an area wavelength of 300 nm to 800 nm and a slope (p) of a transmittance curve of the light having an area wavelength of 200 to 300 nm is 0.05 or more. . The method according to claim 1,
And having a transmittance that satisfies the following formula (1) with respect to light having a wavelength in the range of 300 nm to 800 nm:
[Equation 1]
y = a ₁ x + b ₁
Wherein, x is the wavelength (nm), y is a transmittance (%), a ₁ is a constant of 0.03 to 0.09, b ₁ is in the 30 to 10 constant. The method according to claim 1,
And having a transmittance that satisfies the following formula (2) for light having an area wavelength of 200 to 300 nm:
&Quot; (2) "
y = a ₂ x + b ₂
Wherein, x is the wavelength (nm), y is a transmittance (%), a ₂ is a constant of 0.003 to 0.5, b ₂ is in the -60 to 10 constant. delete delete delete The method according to claim 1,
The thermoplastic resin may be at least one selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyvinyl chloride, polyethylene terephthalate, nylon, polyurethane, polycarbonate, polystyrene, polyvinyl alcohol, polyvinylacetate, poly (meth) Polyvinyl chloride, polyvinylidene chloride, and mixtures of two or more thereof. delete The method of claim 1,
Wherein the thickness of the film is 400 占 퐉 or less. delete

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