Biodegradable coating composition for thermal adhesion and method for producing same

Abstract

To provide a biodegradable thermal adhesive coating agent composition, which is biodegradable and has superior properties and to provide a method of preparation thereof.SOLUTION: The present invention relates to a biodegradable thermal adhesive coating agent composition and a method of preparation thereof, and more specifically, it relates to a biodegradable thermal adhesive coating agent composition, which is biodegradable in order to be environment-friendly, excellent in its adhesion to substrates of various materials, such as paper, plastic, etc., stable in water resistance and viscosity change, and suitable for a production process using thermal adhesion, as well as a method of preparation thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biodegradable coating composition for thermal adhesion and a method for producing the same, and more particularly to a biodegradable coating composition for thermal adhesion that is biodegradable and environmentally friendly, has excellent adhesion to various substrates such as paper and plastic, is stable in water resistance and viscosity change, and is suitable for thermal adhesion production processes, and a method for producing the same.

[0002] The biodegradable thermal bonding composition of the present invention does not require adhesives or laminating equipment, so production costs and environmental loads are reduced, and it can be used in a variety of fields. [Background technology]

[0003] Currently, various ready-to-eat foods or disposable packaged foods are widely available, and food packaging materials are also widely used. Such food packaging materials must have appropriate barrier properties against moisture and air to maintain the freshness and flavor of food, excellent adhesion to substrates, be environmentally friendly in consideration of the environment and health, and be highly compatible with the human body. In addition to food packaging materials, various other packaging materials, such as pharmaceutical packaging materials and Ringer's solution bags, are also required to have water resistance, barrier properties, biodegradability, and environmental friendliness. However, conventional packaging materials are used as interleaving paper for films such as PE and PP plastics as thermal adhesive materials, which are non-biodegradable and therefore not environmentally friendly.

[0004] In response to the above-mentioned problems, starch-based materials have been developed as alternative materials. Although these materials are excellent in terms of recyclability and environmental friendliness, they have been pointed out to have a problem in that, as time passes after starch gelatinization, the number of hydrogen bonds between starch chains increases, which increases the viscosity of the reaction product, making it impossible to distribute the finished product.

[0005] Therefore, there is a demand for compositions that can be applied to various substrates such as paper, metal, glass, and plastic, are environmentally friendly, harmless to the human body, and have stable thermal adhesiveness, water resistance, and viscosity. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to solve the above-mentioned problems of the prior art by providing a biodegradable thermal adhesive coating composition having excellent physical properties and a method for producing the same. In particular, the present invention provides a biodegradable thermal adhesive coating composition that can be applied to various types of substrates, does not undergo aging over time, has stable viscosity, and can maintain a constant adhesive strength, and a method for producing the same. [Means for solving the problem]

[0007] To achieve the above object, the present invention provides a biodegradable coating composition for thermal adhesion, comprising thermoplastic starch (TPS), a pH adjuster, a viscosity stabilizer, a first solvent, a second solvent, and a natural resin.

[0008] The present invention also provides (a) adding a pH adjuster to a first solvent; (b) adding thermoplastic starch to the (a) solution; (c) increasing the temperature of the (b) solution; (d) adding a viscosity stabilizer to the heated (c) solution and reacting it; (e) cooling the (d) solution; (f) adding a second solvent to the cooled solution; (g) adding a natural resin to the (f) solution; (h) stirring the (g) solution and then recovering the final solution; The present invention relates to a method for producing a biodegradable coating composition for thermal adhesion, comprising the steps of: [Effects of the Invention]

[0009] The biodegradable coating composition for thermal adhesion of the present invention has the advantages of being excellent in thermal adhesive strength and durability, being capable of adjusting viscosity, and being applicable to various substrates such as paper, plastic, etc. Therefore, it is expected that it will be widely used not only as a food packaging material but also as a packaging material in various fields. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a photograph showing the liquid stability of the composition of Example 13. [Figure 2] FIG. 2(a) shows the composition of Comparative Example 1, and FIG. 2(b) is a photograph showing the liquid stability of Comparative Example 2. [Figure 3] 1 is a photograph showing the liquid stability of Comparative Example 3. [Figure 4] FIG. 4(a) is a photograph showing the water absorbency of the composition of Example 13, and FIG. 4(b) is a photograph showing the water absorbency of the composition of Comparative Example 11. [Figure 5] 1 is a photograph showing the results of peeling off the coated paper after thermally adhering the composition of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in more detail below through specific examples. The following examples are intended to describe preferred embodiments of the present invention, and the scope of the present invention should not be construed as being limited by the details of the following examples.

[0012] In the present invention, "%" means % by weight.

[0013] "Biodegradable" generally refers to a material that is broken down by the action of natural microorganisms such as bacteria, fungi, and algae, heat from the environment, moisture, or other environmental factors.

[0014] "Thermoplastic starch" means starch obtained by treating it with a plasticizer.

[0015] The present invention relates to a biodegradable thermal adhesive coating composition comprising thermoplastic starch (TPS), a pH adjuster, a viscosity stabilizer, a first solvent, a second solvent, and a natural resin.

[0016] In one embodiment, the composition comprises 7 to 25 wt% thermoplastic starch (TPS), 1 to 5 wt% pH adjuster, 0.08 to 1.0 wt% viscosity stabilizer, 3 to 20 wt% second solvent, 3 to 35 wt% natural resin, and the remainder being the first solvent.

[0017] In one embodiment, the thermoplastic starch is added in an amount of 7 to 25% by weight of the coating composition. This range provides advantageous effects in terms of achieving thermal adhesive strength and productivity. If the thermoplastic starch content is less than 7% by weight, the amount of solvent becomes relatively large, which increases the time required to dry the solvent during the process, resulting in a disadvantage in terms of productivity. If the content of the thermoplastic starch is more than 25% by weight, the viscosity becomes too high, making the process difficult to apply.

[0018] In the present invention, the starch may be mixed or combined with acrylic resins, silane hydrolysates, urethane resins, polyolefin resins, and biodegradable resins to provide adhesive properties and coating stability. Biodegradable resins may include at least one of polylactic acid (PLA), polycaprolactone (PCL), polypropylene carbonate (PPC), polyglycolic acid (PGA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), thermoplastic starch (TPS), and polyethylene carbonate (PEC). Various coating materials can be prepared by combining a hard biodegradable resin (e.g., PLA) with a soft biodegradable resin (e.g., PCL, PPC), and biodegradable films with various physical properties can be formed using these coating materials. For example, by mixing a hard biodegradable resin and a soft biodegradable resin in a solution, it is possible to form a biodegradable film that has excellent physical properties such as barrier properties, coating properties, mechanical strength, etc. Furthermore, paper coated with the biodegradable film can be used for various purposes and is environmentally friendly.

[0019] The pH adjuster is not particularly limited as long as it is an alkaline substance that promotes starch gelatinization and inhibits retrogradation, and any known material can be selected and used. In one embodiment, the pH adjuster may be any one selected from inorganic alkaline compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and sodium carbonate. The organic alkaline compound may include a primary amine, a secondary amine, a tertiary amine, or a mixture thereof. The primary amine may be any one or more selected from the group consisting of methylamine, methanolamine, ethylamine, ethanolamine, propylamine, 3-amino-1-propanol, isopropylamine, monoisopropanolamine, tert-butylamine, butylamine, hexylamine, dodecylamine, cyclohexylamine, ethylenediamine, and hexamethylenediamine. The secondary amine may be any one or more selected from the group consisting of dimethylamine, diethylamine, diethanolamine, dipropylamine, N-ethylmethylamine, N-methylpropylamine, 3-(methylamino)-1-propanol, N-isopropylmethylamine, dibutylamine, diisopropyl ... and the tertiary amine is at least one selected from the group consisting of trimethylamine, trimethanolamine, triethylamine, triethanolamine, dimethylethanolamine, N,N-dimethylpropylamine, N,N-dimethylbutylamine, 3-dimethylamino-1-propanol, N,N-dimethyldodecylamine, N,N-dimethyloctadecylamine, tripentylamine, N,N-dimethylcyclohexylamine, 3-(dimethylamino)benzyl alcohol, and N,N,N',N'-tetramethyl-1,4-butanediamine.

[0020] In particular, sodium hydroxide can be used. In one embodiment, the pH adjuster can be used in the range of 1 to 5% by weight. If it is added in an amount less than 1% by weight, the starch gelatinization action is minimal, resulting in a decrease in the retrogradation inhibitory effect. If it is added in an amount greater than 5% by weight, the coating agent contains an excess of hydrophilic substances, resulting in a coating film with poor water resistance after coating.

[0021] Viscosity stabilizers are bulky single molecules that are located in the starch chains and prevent hydrogen bonding between starch chains, suppressing viscosity increase and allowing adjustment of the viscosity to the desired level depending on the type. In addition, because they have a high carbon number and few functional groups, they can also contribute to improving water resistance.

[0022] In one embodiment, the viscosity stabilizer can be any one or more selected from the group consisting of lecithin, lysolecithin, glycerin fatty acid ester, sucrose fatty acid ester, propylene glycol fatty acid ester, whey protein isolate (9410 WPI), whey protein concentrate (8000 WPC), soy protein isolate (SPI), rice protein isolate (RPI), oat protein isolate (OPI), pea protein isolate (PPI), casein, sodium caseinate, corn protein, gelatin, wheat protein (gluten), dextrins, carrageenans, Tween 80, Tween 20, and cellulose. In one embodiment, the viscosity stabilizer can be used in the range of 0.08 to 1.0 wt%. If it is added in an amount less than 0.08 wt%, it will not be effective in preventing an increase in viscosity, and if it is added in an amount greater than 1.0 wt%, the thermal adhesiveness will decrease. In one embodiment, it is preferably used in the range of 0.1 to 0.5 wt%.

[0023] The first solvent is not limited to, but may be, for example, one or more of water, distilled water, and purified water.

[0024] The second solvent may be an alcohol having 1 to 6 carbon atoms, and may be, for example, one or more selected from the group consisting of alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, 2-amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol, and mixtures thereof.

[0025] The second solvent improves coatability and production speed of coated paper, and inhibits enzyme action to prevent spoilage when using natural-based materials.

[0026] In one embodiment, the second solvent is used in an amount of 3 to 20% by weight. When added at less than 3% by weight, there is no effect of improving coating properties and productivity, and when added at more than 20% by weight, there is a possibility of starch precipitation. In one embodiment, the amount is preferably 3 to 10% by weight.

[0027] In one embodiment, the composition of the present invention can further contain a natural resin, preferably shellac. Shellac is a type of animal resin produced by purifying or bleaching the yellow gum secreted by lac bugs and is typically used in paints and finishes. In the present invention, it is used as a coating agent to improve water resistance and antibacterial properties. In one embodiment, shellac is used in an amount of 3 to 35% by weight. When added in an amount of less than 3% by weight, the effect of improving water resistance and antibacterial properties is not achieved. When added in an amount of more than 35% by weight, shock with the starch occurs, resulting in precipitation of a mixed mass of starch and shellac, making it difficult to use as a coating agent. In one embodiment, the amount is preferably 15 to 30% by weight.

[0028] In addition to the above components, other additives may be added to the compositions of the present invention, such as dispersing aids, melt stabilizers, processing stabilizers, heat stabilizers, light stabilizers, antioxidants, heat aging stabilizers, brighteners, antiblocking agents, binders, lubricants, water-soluble polymers, fillers, etc. Dispersing aids can be used, for example, to aid in the formation of a uniform dispersion and to delay or prevent separation into component phases. Similarly, dispersing aids can also improve the aqueous dispersibility of the coating composition.

[0029] Furthermore, the present invention provides (a) adding a pH adjuster to a first solvent; (b) adding thermoplastic starch to the (a) solution; (c) increasing the temperature of the (b) solution; (d) adding a viscosity stabilizer to the heated (c) solution and reacting it; (e) cooling the (d) solution; (f) adding a second solvent to the cooled solution; (g) adding a natural resin to the (f) solution; (h) stirring the (g) solution and then recovering the final solution; The present invention provides a method for producing a biodegradable coating composition for thermal adhesion, comprising:

[0030] In step (a), a pH adjuster can be added to the first solvent while stirring using a mechanical stirrer, followed by adding thermoplastic starch in step (b), and then heating the reaction mixture to 60 to 90°C in step (c), but this is not limiting.

[0031] Then, in step (d), a viscosity stabilizer is added to the reaction solution while slowly stirring, and the reaction is allowed to proceed. The viscosity stabilizer can be added according to the content range of the type described above. The reaction can then be allowed to proceed for 1 to 4 hours, but is not limited thereto.

[0032] In step (e), the reacted solution can be cooled to room temperature.

[0033] In step (f), the second solvent is slowly added to the cooled solution while stirring, and then in step (g), the natural resin is added to the solution. Then, in step (h), the solution in step (g) is stirred, and the final solution can be recovered. The reaction can be carried out for 10 to 30 minutes, but is not necessarily limited to this.

[0034] In one embodiment, the natural resin is shellac.

[0035] In one embodiment, the prepared biodegradable thermal adhesive coating composition can be further dispersed using ultrasound, a high-pressure disperser, or a homogenizer to achieve uniform dispersion, preferably using a high-pressure dispersion method.

[0036] In one embodiment, further physical properties can be adjusted through a heating and / or pressure step, and residual solvent can be removed by a drying step.

[0037] The biodegradable coating composition for thermal bonding can be applied to a substrate at a thickness of 0.1 μm to 90 μm. The thicker the thickness, the higher the thermal bonding strength, and the thinner the thickness, the lower the cost of the manufacturing process.

[0038] The substrate to which the biodegradable thermal adhesive coating composition is applied may be, without limitation, paper, plastic, metal, or the like, and may include a functional layer between the substrate and the coating layer to impart additional physical properties. For example, a primer layer or an oxygen-barrier layer may be selectively laminated, or the primer layer and the oxygen-barrier layer may be laminated simultaneously. The primer layer or the oxygen-barrier layer may further include a step of applying the primer layer or the oxygen-barrier layer to a thickness of 1 μm to 10 μm. For example, when a coating liquid is applied to a film coated (surface-treated) with a urethane primer, the primer improves adhesion, preventing the coating layer from peeling off from the substrate film. Furthermore, the film may be further subjected to a surface treatment such as plasma or corona to improve adhesion.

[0039] In one aspect, the step of providing the biodegradable thermal adhesive coating composition on the substrate may be performed by coating the biodegradable thermal adhesive coating composition on the substrate, for example, by spray coating, spin coating, dip coating, gravure coating, microgravure coating, die coating, comma coating, knife coating, direct coating, bar coating, etc., but is not limited thereto.

[0040] The coated composition can be dried on the substrate to evaporate the solvent, using a hot air dryer at a temperature of 60 to 150°C for 1 to 5 minutes, preferably at 100°C for 2 to 3 minutes, although this is not limited thereto.

[0041] In the following, the following examples illustrate the invention without limiting its scope.

[0042] [Example 1] 88.4 g (68 wt%) of distilled water as the first solvent was stirred at 300 rpm using a mechanical stirrer, and 1.5 g (1.15 wt%) of 1N NaOH was added. Then, 10 g (7.69 wt%) of thermoplastic starch was added, and the reaction mixture was heated to 80°C. Upon reaching 80°C, stirring was continued at 500 rpm, and 0.1 g (0.08 wt%) of lecithin was slowly added. The mixture was allowed to react at 80°C for 1 hour, and then cooled. 100 g of the reaction mixture at room temperature was stirred at 1,000 rpm using a mechanical stirrer, and 10 g (7.69 wt%) of ethanol as the second solvent was slowly added. After 10 minutes of adding the ethanol, 20 g (15.38 wt%) of shellac was added. After stirring for 20 minutes, the reaction mixture was recovered. The final composition was uniformly dispersed using a high-pressure disperser (1000 bar, 3 passes) to a particle size of about 100 nm.

[0043] Example 2 ~7、10、13~14、18、20、22 ~25] A coating composition was prepared in the same manner as in Example 1, except that the components and amounts thereof were changed as shown in Table 1 below.

[0044] Comparative Examples 1 to 11 、13~21 ] In the process of Example 1, Comparative Examples 1 to 11 in Table 1 、13~21 The coating compositions were prepared in the same manner as in the composition of Example 1 except for changing the components and contents.

[0045] [Table 1]

[0046] [Comparative Example 12] After recovering the composition in the process of Example 1, the same process was followed to prepare the composition, except that the high-pressure dispersion process was not carried out.

[0047] [Experimental Example 1] Liquid stability measurement The compositions of the examples and comparative examples were stored under normal temperature and humidity conditions for 30 days, and then visually observed for stability. Figures 1(a) and 1(b) are photographs showing the liquid stability of the composition of Example 1. Figures 2(a) and 2(b) are photographs showing the liquid stability of the compositions of Comparative Example 1 and Comparative Example 2, respectively. Figure 3 is a photograph showing the liquid stability of the composition of Comparative Example 12, which was not subjected to a dispersion step.

[0048] The composition of Example 1 maintained a uniform and stable state, whereas the compositions of Comparative Examples 1 and 2 either spoiled or gelled, making them difficult to use as coating compositions. The composition of Comparative Example 12 thickened, making it unsuitable as a coating composition.

[0049] [Experimental Example 2] Viscosity measurement The viscosity of the compositions prepared in the examples and comparative examples was measured using a viscometer (Brookfield, DV2TRV) under normal temperature and humidity conditions (20±5°C, 55±5%) (spindle: No. 06, rpm: 100 rpm). The results are shown in Table 2.

[0050] [Experimental Example 3] Water absorption measurement After the base paper was firmly attached to a glass plate, approximately 1 to 2.5 g of the coating composition prepared using the compositions of the Examples and Comparative Examples was dropped onto the base paper, and the composition was applied to a uniform thickness on the base paper using a bar coater. The film coated with the composition was dried at 100°C for 2 minutes using a hot air dryer to produce coated paper. The prepared coated paper was then coated with a 100 cm 2Distilled water was poured onto the circular test piece, and after leaving it for 60 seconds, the water absorbency was evaluated by subtracting the weight before and after the test from the weight after the test. The results are shown in Table 2. Figure 4(a) is a photograph showing the water absorbency of the composition of Example 1, and Figure 4(b) is a photograph showing the water absorbency of the composition of Comparative Example 1. The composition of Example 1 was stable with no visible change, while the composition of Comparative Example 1 was observed to absorb water and cause the paper to wrinkle.

[0051] [Experimental Example 4] Measurement of thermal adhesive strength The coating agent prepared in Experimental Example 3 was applied to a thermal gradient tester (Qmesys, QM930D) with the lower heating plate set to 60°C and the upper heating plate set to 150°C. Two sheets of coated paper were placed between the plates with the coating facing up, and pressure was applied for 1 second to thermally bond them. The thermally bonded coated paper was then cut into 10 mm wide x 100 mm long pieces (thermal bonding area: 10 mm wide x 25 mm long) to prepare samples, and the adhesive strength was measured using a universal testing machine (Lloyd's, LS1). The results are shown in Table 2.

[0052] [Table 2]

[0053] As shown in Table 2, the compositions of the Examples generally exhibited properties that were effective as adhesive compositions, whereas the compositions of the Comparative Examples either spoiled or gelled and could not be applied. 7 The compositions of Examples 10, 13, 14, 20, and 22 to 25 were also evaluated as being favorable in terms of viscosity, water absorption, and adhesive strength. The viscosity of Example 6 was slightly increased, Comparative Example 13 The drying time is somewhat slow, Comparative Example 15 Has high moisture absorption, Comparative Examples 17 and 20 Shock occurs, Comparative Example 21 The thermal adhesive strength was low.

[0054] Furthermore, in Experimental Example 3, coated paper to which the composition of Example 1 was applied was thermally bonded and then peeled off, and the results are shown in Figure 5. It was found that the sealing property was so excellent that the paper broke when peeled off.

Claims

1. A biodegradable thermal adhesive coating composition comprising thermoplastic starch (TPS), a pH adjuster, a viscosity stabilizer, a first solvent, a second solvent, and a natural resin, the composition comprises 7 to 25 wt. % of thermoplastic starch, 1 to 5 wt. % of pH adjuster, 0.08 to 1 wt. % of viscosity stabilizer, 3 to 20 wt. % of second solvent, 15 to 30 wt. % of natural resin, and 39.53 to 68.00 wt. % of first solvent; the pH adjuster is at least one selected from sodium hydroxide and dimethylethanolamine (DMEA); the viscosity stabilizer is one or more selected from lecithin, whey protein, sodium caseinate, and polysorbate 80; the first solvent is at least one selected from water, distilled water, and purified water; the second solvent is ethanol; The natural resin is shellac, Dispersed by ultrasound, a high-pressure disperser or a homogenizer; Biodegradable coating composition for thermal adhesion.

2. A biodegradable coating composition for thermal adhesives, comprising thermoplastic starch (TPS), a pH adjuster, a viscosity stabilizer, a first solvent, a second solvent, and a natural resin, the composition comprises 7 to 25% by weight of thermoplastic starch, 1 to 5% by weight of a pH adjuster, 0.08 to 1% by weight of a viscosity stabilizer, 3 to 20% by weight of a second solvent, 15 to 30% by weight of a natural resin, and the balance being the first solvent; the pH adjuster is at least one selected from sodium hydroxide and dimethylethanolamine (DMEA); the viscosity stabilizer is one or more selected from lecithin, whey protein, sodium caseinate, and polysorbate 80; the first solvent is at least one selected from water, distilled water, and purified water; the second solvent is ethanol; The natural resin is shellac, Dispersed by ultrasound, a high-pressure disperser or a homogenizer; Biodegradable coating composition for thermal adhesion.

3. A packaging material comprising the composition according to claim 1 or 2 and a substrate.

4. A method for producing the biodegradable thermal adhesive coating composition according to claim 1 or 2, comprising: (a) adding the pH adjuster to the first solvent; (b) adding the thermoplastic starch to the (a) solution; (c) increasing the temperature of the (b) solution; (d) adding the viscosity stabilizer to the heated solution (c) and reacting it; (e) cooling the (d) solution; (f) adding the second solvent to the cooled solution; (g) adding the natural resin to the (f) solution; (h) stirring the (g) solution and then recovering the final solution; (i) dispersing the recovered composition after step (h) using ultrasound, a high-pressure disperser, or a homogenizer; Including, A method for producing a biodegradable thermal adhesive coating composition.

5. The method according to claim 4, wherein the temperature is increased to a range of 60 to 90°C in the step (c).

6. The method according to claim 4, wherein in step (d), after adding the viscosity stabilizer, the reaction is carried out for a period of 1 to 4 hours.

7. The method according to claim 4, wherein after the shellac is added, the reaction is carried out with stirring for 10 to 30 minutes.

8. The manufacturing method described in claim 4, wherein step (i) includes a high-pressure dispersion process using the high-pressure disperser.

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