KR20220138542A - Biodegradable bioplastic based foam sheet and use of foam-molding product using the same - Google Patents

Abstract

The present invention relates to a bioplastic-based foam sheet and to a biodegradable molded foam product using the same. The present invention provides the bioplastic-based foam sheet containing a polyhydroxyalkanoate-based polymer and optimizing compatibility between components to be suitable for manufacturing an extruded foam sheet to be extruded and foamed to have increased mechanical strength and improved biodegradation rate of polyhydroxyalkanoate-based polymers, and molded and processed and applied to the biodegradable molded foam products applied to fields including food packaging containers, industrial packaging materials, industrial materials, agricultural materials, and fishery materials.

Description

Bioplastic-based foam sheet and biodegradable molded foam product using the same

The present invention relates to a bioplastic-based foam sheet and a biodegradable molded foam product using the same. The present invention relates to a bioplastic-based foam sheet that simultaneously improves the mechanical strength and biodegradation rate of a polyhydroxyalkanoate-based polymer by extruding and foaming the composition, and a biodegradable molded foam product obtained by molding and processing the same.

As environmental pollution emerges as a serious problem that threatens the future of mankind, interest in the bioplastics industry is growing as an alternative to solve it.

The bioplastic industry refers to an industry that uses renewable biological resources such as plants, microorganisms, and enzymes to replace materials in the existing chemical industry with bio-based materials. In particular, as the number of disposable plastic waste increases worldwide due to shutdowns and the spread of non-face-to-face culture, industrial interest in biodegradable bioplastics as a substitute for non-biodegradable plastics is increasing, especially in the packaging field.

Plastic waste treatment options include incineration, recycling and biodegradation, but most of these methods pose potential problems. In order to replace these petrochemical-derived plastics, research on highly biodegradable bioplastics has been conducted, which includes plastics made by polymerizing starch, cellulose, lactic acid, and glycolic acid, and polysynthesized by microorganisms. Poly hydroxy alkanoate (hereinafter PHA) is targeted.

Among them, polyhydroxyalkanoate (PHA), a biodegradable polymer, is synthesized by soil microorganisms used as intracellular storage materials, has properties similar to synthetic plastics, and is completely decomposed into water and carbon dioxide under aerobic conditions. Therefore, it is gaining popularity as an alternative to plastics.

However, to date only significant amounts of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers are available, limiting the commercial availability of PHAs.

Although various PHAs can be processed with conventional processing equipment, it is difficult to maintain molecular weight and in some cases, lack of processability may limit commercial applications.

In addition, there is a lack of understanding of the crystallization kinetics of these polymers, and the processing of these polymers often results in long cycle times, which further limits the commercial acceptance of the polymers.

Even in biodegradable polyesters that are decomposed into water and carbon dioxide by the function of microorganisms, in the case of polyhydroxyalkanoates, particularly poly(3-hydroxyalkanoates), the slow crystallization has been pointed out as a drawback.

Patent Document 1 discloses that by mixing sugar alcohols as a nucleating agent with polyhydroxyalkanoate that is crystallized late, interaction or interface matching between many hydroxyl groups present in the sugar alcohols and ester groups of PHA by hydrogen bonding. It is reported that crystallization is promoted by effects such as epitaxial growth.

However, PHA compositions containing high levels of 3-hydroxybutyrate monomer have physical limitations such as brittleness and thermal stability problems at melt processing temperatures (eg, those used for injection molding, sheet extrusion and blown film conversion). still exist, and the resulting products may not have acceptable toughness for many applications.

Patent Document 2 is an invention related to polyhydroxyalkanoate resin foam particles having good biodegradability and poly(3-hydroxybutyrate) ( PHB) and a P3HA resin composition comprising 0.1 to 10 parts by weight of a isocyanate compound are disclosed and proposed to improve processability.

On the other hand, when crystallized at a higher rate, there is a problem that the thermoplastic material loses adhesiveness as well as the mechanical strength properties of the polymer during processing.

Accordingly, the present inventors have devised to improve the physical properties of bioplastics according to the prior industrial needs, and extruded and foamed a composition containing a polyhydroxyalkanoate-based polymer and optimizing compatibility between components to be suitable for manufacturing an extruded foam sheet. Thus, the present invention was completed by confirming the production of foam sheets that simultaneously improved the mechanical strength and biodegradation rate of the polyhydroxyalkanoate-based polymer.

Patent Document 1: Japanese Laid-Open No. 2013-231189 (published on November 14, 2013) Patent Document 2: Japanese Patent No. 5408877 (Registered on November 15, 2013)

An object of the present invention is to provide a bioplastic-based foam sheet in which a composition containing a polyhydroxyalkanoate-based polymer and compatibility between components is optimized to be suitable for manufacturing an extruded foam sheet.

Another object of the present invention is to provide a biodegradable molded foam product in which the bioplastic-based foam sheet is molded.

The present invention relates to 100 parts by weight of the polyhydroxyalkanoate-based polymer, 0.01 to 4 parts by weight of a crosslinking agent, 0.001 to 1 part by weight of a plasticizer, and A composition in which 0.01 to 4 parts by weight of a foaming nucleating agent is mixed provides a bioplastic-based foam sheet extruded and foamed.

In the present invention, the polyhydroxyalkanoate-based polymer is a polymer having a molecular weight of 100,000 to 2 million, specifically, a polymer in which the repeating structure of 3-hydroxyalkanoate is crosslinked by polymerization or E-beam. It is a polymer crosslinked by

3-hydroxyalkanoate is a polymer crosslinked by polymerization.

Specifically, the polyhydroxyalkanoate-based polymer is 3-hydroxybutyrate (3-hydroxybutyrate,), 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate (3-hydroxyheptanoate), hydroxyoctanoate (3-hydroxyoctanoate), hydroxynonanoate (3-hydroxynonanoate), hydroxydecanoate (3-hydroxydecanoate), hydroxyunde Canoate (3-hydroxyundecanoate), hydroxydodecanoate (3-hydroxydodecanoate), hydroxytridecanoate (3-hydroxytridecanoate), hydroxytetradecanoate (3-hydroxytetradecanoate), hydroxypentadecanoate ( 3-hydroxypentadecanoate), hydroxyhexadecanoate (3-hydroxyhexadecanoate), 3-hydroxyundec-10-enoate (3-hydroxyundec-10-enoate) and 3-hydroxy-5-phenylvalerate (3-hydroxyundec-10-enoate) hydroxy-5-phenylvalerate) is a homopolymer in which hydroxyalkanoates of the same type are polymerized, and a copolymer or terpolymer in which two or more types of hydroxyalkanoates of different types are polymerized.

More preferably, the polyhydroxyalkanoate-based polymer is poly-3-hydroxybutyrate (P3HB), poly-3-hydroxyvalerate (PHV), poly3- Hydroxyhexanoate (poly-3-hydroxyhexanoate, PHH), poly-3-hydroxyoctanoate (PHO), poly3-hydroxybutylate-co-3-hydroxyvalerate ( poly(3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV), poly3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), poly3 -Hydroxybutylate-co-4-hydroxybutyrate (poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly3-hydroxybutyrate-co-3-valerate (poly(3-hydroxybutyrate-co -3-valerate, PHBV), poly-3-hydroxybutyrate-co-3-hydrohexanoate (poly(3-hydroxybutyrate-co-3-hydroxyhaxanoate, PHBH), Using any one selected from the group consisting of poly 3-hydroxybutyrate-co-3-hydroxyundec-10-enoate (poly(3-hydroxyoctanoate-co-3-hydroxyundec-10-enoate, PHOU) will be.

In addition, the polyhydroxyalkanoate-based polymer of the present invention is added to the poly(3-hydroxyalkanoate (PHA)-based first polymer, thermoplastic starch (TPS), polybutylene succinate (PBS), polybutyl Lene adipate (PBA), polybutylene adipate (PBA), poly(butylene succinate co-butylene adipate) (PBSA), poly(butylene adipate co-terephthalate) (PBAT), poly (butylene adipate co-succinate co-terephthalate) (PBAST), poly(butylene succinate co-L-lactate) (PBSL), polycaprolactone (PCL), polyglycolic acid (PGA), poly At least one second polymer selected from the group consisting of vinyl alcohol (PVA), polylactic acid (PLA), polyhydroxyalkanoate and aliphatic/aromatic copolymer polyester is a blended polymer, and the second polymer is 0.01 to 90 It is contained in % by weight.

The bioplastic-based foam sheet of the present invention optimizes the biodegradability rate of the polyhydroxyalkanoate-based polymer, improves mechanical strength, and provides a composition in consideration of compatibility between components so as to be advantageous for processing the extruded foam sheet.

Furthermore, the present invention is biodegradable applied to any one selected from the group consisting of food packaging containers, industrial packaging materials, industrial materials, medical materials, medical clothing, agricultural materials and fishery materials by molding and processing the above bioplastic-based foam sheet. Molded foam products are provided.

The present invention improves the physical properties of a polyhydroxyalkanoate-based polymer, provides a composition that optimizes compatibility between components to be suitable for manufacturing an extruded foam sheet, and further accelerates the increase in mechanical strength and biodegradation rate by using the composition It is possible to provide a bioplastic-based foam sheet so that it can be decomposed.

In addition, the present invention is useful in fields including food packaging containers, industrial packaging materials, industrial materials, agricultural materials, and fishery materials by molding and processing a foam sheet containing a polyhydroxyalkanoate-based polymer with increased mechanical strength and improved biodegradation rate. can be applied

Hereinafter, the present invention will be described in detail.

The present invention relates to 100 parts by weight of a polyhydroxyalkanoate-based polymer, 0.01 to 4 parts by weight of a crosslinking agent consisting of a mixture of an extrusion reaction aid selected from organic peroxide-based, epoxy-based, and combinations thereof;

0.001 to 1 part by weight of a plasticizer and

0.01 to 4 parts by weight of the foaming nucleating agent is mixed to provide a foamed bioplastic-based foam sheet.

The bioplastic-based foam sheet of the present invention contains a polyhydroxyalkanoate-based polymer as a main component, but it can be obtained from a composition in consideration of compatibility between components so as to be suitable for improving physical properties and weaving the extruded foam sheet.

Hereinafter, the characteristics of each component will be described in detail.

1) Polyhydroxyalkanoate-based polymer

The polyhydroxyalkanoate-based polymer used in the present invention uses a polymer satisfying a molecular weight of 100,000 to 2,000,000, and a polymer in which the repeating structure of 3-hydroxyalkanoate represented by the following formula is crosslinked by polymerization Alternatively, the repeating structure of 3-hydroxyalkanoate is a polymer crosslinked by E-beam.

In the above, R is a C ₁ to C ₁₃ alkyl group, and a C ₆ to C ₁₀ aryl group.

Specifically, the polyhydroxyalkanoate-based polymer is 3-hydroxybutyrate (PHB), 3-hydroxyvalerate (PHV), 3-hydroxyhexanoate ( 3-hydroxyhexanoate), 3-hydroxyheptanoate (3-hydroxyheptanoate), hydroxyoctanoate (3-hydroxyoctanoate), hydroxynonanoate (3-hydroxynonanoate), hydroxydecanoate (3-hydroxydecanoate) , hydroxyundecanoate (3-hydroxyundecanoate), hydroxydodecanoate (3-hydroxydodecanoate), hydroxytridecanoate (3-hydroxytridecanoate), hydroxytetradecanoate (3-hydroxytetradecanoate), hydroxypenta Decanoate (3-hydroxypentadecanoate), hydroxyhexadecanoate (3-hydroxyhexadecanoate), 3-hydroxyundec-10-enoate (3-hydroxyundec-10-enoate) and 3-hydroxy-5-phenyl valence A homopolymer in which hydroxyalkanoates of the same kind selected from the group consisting of 3-hydroxy-5-phenylvalerate are polymerized, a copolymer or terpolymer in which two or more kinds of hydroxyalkanoates of different kinds are polymerized is used. .

More preferred polyhydroxyalkanoate-based polymers are poly-3-hydroxybutyrate (P3HB), poly-3-hydroxyvalerate (PHV), poly3-hydroxy Hexanoate (poly-3-hydroxyhexanoate, PHH), poly-3-hydroxyoctanoate (PHO), poly3-hydroxybutylate-co-3-hydroxyvalerate (poly(( 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), poly3-hydroxybutyrate-co-3-hydroxyhexanoate (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate, PHBH), poly3-hydroxy hydroxybutyrate-co-4-hydroxybutyrate (poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly3-hydroxybutyrate-co-3-valerate (poly(3-hydroxybutyrate-co-3 -valerate, PHBV), poly 3-hydroxybutyrate-co-3-hydrohexanoate (poly(3-hydroxybutyrate-co-3-hydroxyhaxanoate, PHBH), Using any one selected from the group consisting of poly 3-hydroxybutyrate-co-3-hydroxyundec-10-enoate (poly(3-hydroxyoctanoate-co-3-hydroxyundec-10-enoate, PHOU) will be.

In addition, the polyhydroxyalkanoate-based polymer of the present invention is added to the poly(3-hydroxyalkanoate (PHA)-based first polymer, thermoplastic starch (TPS), polybutylene succinate (PBS), polybutyl Lene adipate (PBA), polybutylene adipate (PBA), poly(butylene succinate co-butylene adipate) (PBSA), poly(butylene adipate co-terephthalate) (PBAT), poly (butylene adipate co-succinate co-terephthalate) (PBAST), poly(butylene succinate co-L-lactate) (PBSL), polycaprolactone (PCL), polyglycolic acid (PGA), poly A blend polymer in which at least one second polymer selected from the group consisting of vinyl alcohol (PVA), polylactic acid (PLA), polyhydroxyalkanoate and aliphatic/aromatic copolymer polyester is also possible, wherein the second polymer is It is preferably contained in an amount of 0.01 to 90% by weight.In this case, if the content of the second polymer is less than 0.01% by weight, the effect of improving the mechanical strength that can be expected from the blend polymer is insignificant, and when it exceeds 90% by weight, the compatibility between components There is a problem with sex.

2) crosslinking agent

For the purpose of increasing the molecular weight of the polyhydroxyalkanoate-based polymer of the present invention, a crosslinking agent performing a chain extension function is used as an additive.

In addition, it is also used for the purpose of meeting the melt index suitable for sheet extrusion.

The crosslinking agent used in the present invention is preferably an organic peroxide compound, and examples thereof include benzoyl peroxide, lauryl peroxide, dicumyl peroxide, dihexyl peroxide, butylcumyl peroxide, dibutyl peroxide, and p-methanehydride. Roperoxide, diisopropylbenzenehydroperoxide, tetramethylbutylperoxide, cumene hydroperoxide, 2,5-dimethyl-2,5-dibutylperoxyhexyne-3,2,3-dimethyl-2,3- Diphenylbutane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(4,4-di-(t-butyl) Peroxy)cyclohexyl)propane, di(2-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-dibutylperoxyhexane, hexylperoxyisopropylcarbonate, butylperoxy 2-ethylhexyl Carbonate, diisopropyl peroxydicarbonate, butylperoxyisopropyl carbonate, butylperoxymaleic acid, butylperoxy-3,5,5-trimethylhexanoate, butylperoxylaurate, butylperoxybenzoate, hexylpere Any one selected from the group consisting of oxybenzoate, butylperoxyacetate, n-butyl 4,4-di-butylperoxyvalerate, and 2,2-di-butylperoxybutane is used.

The crosslinking agent of the present invention is more preferably a mixture of an organic peroxide compound and an epoxy compound used as a conventional crosslinking agent.

The conventionally used epoxy compound is any one selected from the group consisting of bisphenol A diglycidyl ether, terephthalic acid diglycidyl ether, trimethylolpropane diglycidyl ether, and 1,6-hexanediol diglycidyl ether. There is a disadvantage in that it is expensive to use.

Accordingly, the mixed crosslinking agent of the present invention can provide an equivalent effect while reducing the content of the conventional expensive epoxy-based crosslinking agent, and can increase the melt viscosity by partially crosslinking the polymer chain. At this time, if the mixing ratio is 1 to 2% of the conventional epoxy-based compound, 0.5 to 1% of the epoxy-based compound is mixed with 0.1 to 1% of the organic peroxide-based compound and cross-linked.

The crosslinking agent of the present invention is preferably used in an amount of 0.05 to 4 parts by weight based on 100 parts by weight of the polyhydroxyalkanoate-based polymer. In this case, if the content of the crosslinking agent is less than 0.05 parts by weight, the effect of increasing the apparent molecular weight is insufficient. causes

When the polymer is crosslinked with the epoxy compound, it may further contain 0.01 to 2 parts by weight of a stabilizer and 0.01 to 2 parts by weight of a lubricant based on 100 parts by weight of the polylactic acid-based polymer composition.

In this case, the stabilizer is selected from N,N'-diisopropyl carbodiimide or N,N'-di-2,6-diisopropylphenyl carbodidiimide, and it is preferable to use a carbodiimide-based stabilizer, The melt viscosity of the polymer can be stabilized, and other metal complexes, polyvalent carboxylic acids, or mixtures thereof can be used.

3) plasticizer

Even if the polyhydroxyalkanoate-based polymer obtains an appropriate melt viscosity, when the foaming ratio is low, the moldability is poor, and additional costs such as introduction of a special molding machine to increase the moldability are added, which is not preferable.

Accordingly, the bioplastic-based foam sheet containing the polyhydroxyalkanoate-based polymer of the present invention improves the foaming ratio by adding an appropriate low-molecular-weight plasticizer.

As a preferred plasticizer used in the present invention, it should be compatible with the resin, and preferably, an organic acid or an alcohol-based metal compound or a citric acid-based compound is used.

The following compounds may be selectively used or a mixture of the following compounds may be used. Examples of the compound include aluminum stearate, magnesium stearate, zinc stearate, calcium stearate, aluminum oleate, magnesium oleate, zinc oleate, calcium oleate, aluminum palmitate, magnesium palmitate, zinc palmitate, calcium palmitate, zinc citrate, tributyl citrate, acetylcitrate In addition to triethyl and tributyl acetyl citrate, there are aliphatic polyhydric carbon esters, aliphatic polyhydric alcohol esters, and aliphatic polyhydric alcohol ethers, for example, dimethyl adipate, 2-ethylhexyl adipate, diisobutyl adipate, diisobutyl adipate, Butyl adipate, diisodecyl adipate, dibutyl sebacate, 2-ethylhexyl sebacate, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, diethylene glycol diethyl ether, diethylene glycol diethyl ether ethylene glycol butyl ether, diethylene glycol dibutyl ether, diethylene glycol ethylhexyl ether, polyoxyethylene dimethyl ether, polyoxypropylene dimethyl ether, citric acid and sodium dicarbonate mixture, calcium gluconate, and the like.

When the organic acid or alcohol-based compound and the citric acid-based compound are extruded and foamed in parallel, the size distribution of the foamed cells is uniform, and the thickness of the extruded sheet increases, thereby increasing the foaming ratio.

A preferred amount of the plasticizer to be used is 0.001 to 1 part by weight, more preferably 0.005 to 0.5 part by weight, based on 100 parts by weight of the polyhydroxyalkanoate-based polymer. At this time, when the plasticizer is used in an amount of less than 0.001 parts by weight, the effect of improving the plasticity of the molten resin or improving the expansion ratio of the expanded molded article is insufficient. On the other hand, when it exceeds 1 part by weight, there is a disadvantage in that the expanded molded article and the molded article become too flexible and thus the shape stability is poor.

4) Foaming nucleating agent

As the foaming nucleating agent used in the present invention, any one selected from the group consisting of talc, silica, calcium carbonate, calcium stearate and montmorillonite may be used, and in particular, the foaming nucleating agent may be added in the form of a master batch. have. When preparing the masterbatch, the dispersibility of the foaming nucleating agent may be adjusted by further adding a dispersing agent or the like. In addition, instead of adding the dispersant together during the preparation of the masterbatch, a dispersant may be further added separately. In this case, as the dispersant, stearic acid amide or the like may be used.

In the foam extrusion molding process, if the cell wall thickness of the foam is thin or the size and thickness of the foam cell are uneven, the tensile elongation is lowered and the wall is easily broken.

The foam sheet of the present invention more preferably contains 0.1 to 5 parts by weight of talc having a particle size of 0.5 to 7 μm with respect to 100 parts by weight of the polyhydroxyalkanoate-based polymer, so that it is not easily broken by controlling the cell thickness. A foam can be obtained.

At this time, when the talc is used in less than 0.1 parts by weight, the desired foaming ratio can be improved by 6 to 10 times, but since the size of one foam cell is too large, about 0.5 mm, the quality of the sheet product is deteriorated. On the other hand, when the talc is used in excess of 5 parts by weight, the size of the foamed cells becomes too small, or the walls of the foamed cells are broken, so that the desired foaming drainage cannot be obtained.

In addition, it is preferable to use a particle size of 0.5 to 7 μm for the talc used for the purpose of improving foamability in the present invention. Within the particle range, finer particles are preferable, and if the particle size of 7 μm is exceeded, the desired size and wall thickness of the foamed cell cannot be adjusted.

In addition, a foaming agent is press-injected into the extruder together with the polyhydroxyalkanoate-based polymer and the foaming nucleating agent, and the content of the foaming agent is 1 to 30 parts by weight, preferably 3 to 20 parts by weight. At this time, as the blowing agent, propane, isobutane, n-butane, cyclobutane, isopentane, n-pentane, cyclopentane, isohexane, n-hexane, cyclohexane, trichlorofluoromethane, dichlorodifluoromethane, chlorofluoro Romethane, trifluoromethane, 1,1,1,2-tetrafluoroethane, 1-chloro-1,1-difluoroethane, 1,1-difluoroethane, 1-chloro-1,2 and organic physical blowing agents such as ,2,2-tetrafluoroethane, and inorganic physical blowing agents such as nitrogen, carbon dioxide, argon, and air. As such, nitrogen, air, and carbon dioxide are preferable. Further, with respect to the amount of the blowing agent used, carbon dioxide is preferable from the viewpoint of obtaining expanded particles having a smaller apparent density. Moreover, like carbon dioxide and isobutane, you may use combining 2 or more types of foaming agents.

The present invention relates to 100 parts by weight of a polyhydroxyalkanoate-based polymer, 0.05 to 4 parts by weight of a crosslinking agent, 0.001 to 1 parts by weight of a plasticizer, and foaming supplying a foamed composition mixed with 0.01 to 4 parts by weight of a nucleating agent to an extruder and heating and melt-kneading to prepare a melt-kneaded product;

cooling the melt-kneaded material; and

It provides a method of manufacturing a bioplastic-based foam sheet performed as; extruding the cooled melt-kneaded product.

In the manufacturing step of the present invention, additives necessary for foaming, including the polyhydroxyalkanoate-based polymer, are the same as described above.

In the production method of the present invention, since the foamed composition containing the polyhydroxyalkanoate-based polymer has a high melting point, the crystallization temperature rises accordingly, and furthermore, if the crystallization rate is increased, the molten polymer blend composition can be produced within a short time. It crystallizes and solidifies. That is, if the melt-kneaded material discharged from the die is first solidified before being stretched and expanded in the mandrel, it is difficult to wind the foam sheet having the desired expansion ratio and thickness in a roll state.

Therefore, in the method for manufacturing an extruded foam sheet using the foam composition containing the polyhydroxyalkanoate-based polymer of the present invention, compared to a conventional composition, the die discharging the sheet and the environment near the die, the molten sheet is stretched and expanded, and The temperature of the injection air of the solidifying mandrel and the surrounding environment should be set higher than the degree to which the crystallization temperature rises. Furthermore, depending on the factory equipment and manufacturing environment, the rise width can be set to be larger depending on the temperature and humidity of the atmosphere, the flow of air, and adiabatic heat dissipation conditions.

That is, when supplying to the extruder, it is preferable that the extruder die and its ambient temperature are set to 135 to 210° C., more preferably 5 to 45 compared to conventional polyhydroxyalkanoate-based polymers having a melting point of 155 to 165° C. It is carried out at a temperature set high by °C. At this time, if the temperature is less than 135 ℃, melt kneading is difficult, and if the extrusion temperature condition exceeds 210 ℃, the melt viscosity of the polymer composition is sharply lowered, and the foamed extruded sheet cannot maintain a certain shape, so sheet sagging may occur. can

In addition, in the manufacturing method of the present invention, it is preferable to reduce or increase the temperature of the atmosphere for cooling the sheet, for example, the amount of cooling air blown from the mandrel.

The bioplastic-based foam sheet of the present invention has excellent compatibility between components, and the extruded foam sheet manufactured by increasing the crystallization rate and crystallinity by using a foaming composition containing a polyhydroxyalkanoate-based polymer has excellent heat resistance. The degree of crystallinity of the extruded foam sheet is quite high, and thus the heat resistance is excellent.

In addition, the foamed composition containing the polyhydroxyalkanoate-based polymer of the present invention has good compatibility between the components, so that the foam film is uniformly well formed and stable cells are confirmed. It is also possible to manufacture an expanded molded article with a good surface when molding.

Furthermore, the present invention is a food packaging container, industrial packaging material, industrial material, medical material, medical clothing, agricultural use by molding and processing the bioplastic-based foam sheet obtained from the foaming composition containing the polyhydroxyalkanoate-based polymer. It provides a biodegradable molded foam product that is applied to any one selected from the group consisting of materials and fishery materials.

Specifically, the foam sheet can be obtained as a molded foam product through a conventional processing method. As an example, the foam sheet is heated and softened, sandwiched between the male and female molds, and shaped in the form of a container. The method of thermoforming is mentioned. Examples of the thermoforming method include a vacuum forming method, an air pressure forming method, and a plug assisted forming method.

Therefore, the foamed composition containing the polyhydroxyalkanoate-based polymer is foamed and extruded to increase the molecular weight of the polymer to secure an appropriate melt viscosity, increase crystallinity, improve foam moldability, and obtain uniform foamed cells. , the molded foam molded product can be preferably applied to food packaging containers such as trays, cups, cup noodle containers, lunch boxes, and industrial packaging materials.

Since the foam sheet obtained from the foam composition containing the polyhydroxyalkanoate polymer of the present invention has excellent foam moldability and uniform foam cells, food packaging containers and industrial packaging materials using the same can solve the problems of the prior art. have.

In addition, the biodegradable molded foam product of the present invention can be preferably applied to fishing materials such as fishing nets, fishing lines, and buoys.

Hereinafter, the present invention will be described in more detail through examples.

These examples are for explaining the present invention in more detail, and the scope of the present invention is not limited to these examples.

<Example 1> Preparation of polyhydroxyalkanoate-based polymer-containing composition

Based on 100 parts by weight of the polyhydroxyalkanoate-based polymer, 2 parts by weight of dicumyl peroxide as a crosslinking agent, 0.05 parts by weight of diisodecyl adipate as a plasticizer and 5 μm After mixing 2 parts by weight of talc of particle size using a general mixer such as a tumbling mixer, the foam sheet is formed as follows using a tandem extruder in which the first extruder having an inner diameter of 90 mm and a second extruder having an inner diameter of 120 mm are connected. prepared. After the heating and melting temperature was maintained at 170 to 230°C based on the resin temperature, the temperature of the melt-mixed reactant was slightly decreased in the second extruder connected to the first extruder to bring the resin temperature to about 150°C. Then, it was extruded in a circular die having a cylindrical slit having a diameter of 110 mm and a slit interval of 0.5 mm to foam in a cylindrical shape, and while cooling the cylindrical foam, it was discharged in the direction of taking and extrusion to prepare a foam seat.

<Examples 2 to 15>

A foam sheet was prepared in the same manner as in Example 1, except that a mixture of 1 part by weight of bisphenol A diglycidyl ether and 0.5 parts by weight of an organic peroxide was used as a crosslinking agent.

<Comparative Example 1>

A foam sheet was prepared in the same manner as in Example 1, except that no crosslinking agent was used. For molecular weight, a weight average molecular weight based on the polystyrene polymer was selected using GPC, and the foaming ratio was calculated by measuring the specific gravity of the extruded foamed sheet.

<Examples 16-23>

Except for using 0.05 parts by weight of magnesium palmitate, calcium oleate, zinc stearate, calcium stearate, magnesium stearate, dibutyl adipate and diethylene glycol ethylhexyl ether and 0.5 parts by weight of the citric acid-based compound, the same as in Example 1 By this method, a foam sheet was prepared.

<Comparative Example 2>

A foam sheet was prepared in the same manner as in Example 1, except that a plasticizer was not used.

<Comparative Example 3>

A foam sheet was prepared in the same manner as in Example 1, except that 0.05 parts by weight of calcium stearate was used as a plasticizer, but talc was not used.

<Comparative Example 4>

A foam sheet was prepared in the same manner as in Example 1, except that 0.05 parts by weight of diethylene glycol ethylhexyl ether and 0.5 parts by weight of a citric acid-based compound were used as a plasticizer, but talc was not used.

As shown in Examples 16 to 23, when the organic acid or alcohol-based compound and the citric acid-based compound are extruded and foamed in parallel, it can be seen that the size distribution of the foam cells becomes uniform, and it can be seen that the thickness of the extruded sheet increases. The effect of increasing the magnification was confirmed.

On the other hand, as shown in Comparative Example 2, when only talc is added, the size distribution of the foamed cells is uniform to some extent, but the expansion ratio does not increase. In addition, as shown in Comparative Examples 3 and 4, when a plasticizer is added without adding talc, it can be seen that the expansion ratio is increased, but the size of the foamed cells is increased and the size distribution of the foamed cells is widened.

<Experimental Example 1> Physical property evaluation

1. Mechanical strength measurement

prepared in the above example The mechanical strength of the biodegradable bioplastic-based foam sheet extruded and foamed with a composition containing a polyhydroxyalkanoate-based polymer was measured.

2. Measurement of biodegradation rate

prepared in Examples 1 to 1 For the biodegradable bioplastic-based foam sheet extruded and foamed with a composition containing polyhydroxyalkanoate-based polymer, the crystallization rate and the degree of decomposition were visually evaluated for 20 weeks.

At this time, the evaluation criteria are marked with "○" (fast biodegradation rate), "×" (slow biodegradation rate) and "△" (relatively medium biodegradation rate) depending on whether crystallinity is observed at the completion of the 00-week evaluation period. did.

From the above results, the bioplastic-based foam sheet prepared in Examples increased the crystallization rate of the polyhydroxyalkanoate-based polymer in the final product obtained through the extrusion foam sheet process, thereby improving the biodegradation rate and improving the mechanical strength. Confirmed.

In the above, the present invention has been described in detail only with respect to the described embodiments, but it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical spirit of the present invention, and it is natural that such variations and modifications belong to the appended claims.

Claims (13)

Based on 100 parts by weight of the polyhydroxyalkanoate-based polymer,
0.01 to 4 parts by weight of a crosslinking agent consisting of a mixed form of an extrusion reaction aid selected from organic peroxide-based, epoxy-based, and combinations thereof;
0.001 to 1 part by weight of a plasticizer and
A bioplastic-based foam sheet in which a composition in which 0.01 to 4 parts by weight of a foaming nucleating agent is mixed is extruded and foamed. The bioplastic-based foam sheet according to claim 1, wherein the polyhydroxyalkanoate-based polymer has a molecular weight of 100,000 to 2,000,000. The bioplastic-based foam sheet according to claim 2, wherein the polyhydroxyalkanoate-based polymer is a polymer in which the repeating structure of 3-hydroxyalkanoate represented by the following formula is crosslinked by polymerization:

In the above, R is a C ₁ to C ₁₃ alkyl group, and a C ₆ to C ₁₀ aryl group. The method of claim 1, wherein the polyhydroxyalkanoate-based polymer is 3-hydroxybutyrate (PHB), 3-hydroxyvalerate (PHV),
3-hydroxyhexanoate, 3-hydroxyheptanoate, hydroxyoctanoate, 3-hydroxynonanoate, hydroxy Decanoate (3-hydroxydecanoate), hydroxyundecanoate (3-hydroxyundecanoate), hydroxydodecanoate (3-hydroxydodecanoate), hydroxytridecanoate (3-hydroxytridecanoate), hydroxytetradecanoate ( 3-hydroxytetradecanoate, 3-hydroxypentadecanoate, 3-hydroxyhexadecanoate, 3-hydroxyundec-10-enoate and 3 - A homopolymer in which hydroxyalkanoates of the same type selected from the group consisting of 3-hydroxy-5-phenylvalerate are polymerized, A bioplastic-based foam sheet, characterized in that it is a polymer or terpolymer. 5. The method of claim 4, wherein the polyhydroxyalkanoate-based polymer is poly-3-hydroxybutyrate (P3HB), poly-3-hydroxyvalerate (PHV), Poly-3-hydroxyhexanoate (PHH), poly-3-hydroxyoctanoate (PHO), poly3-hydroxybutylate-co-3-hydroxy poly(3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate, PHBH) , poly3-hydroxybutyrate-co-4-hydroxybutyrate (poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly3-hydroxybutyrate-co-3-valerate (poly(3-hydroxybutyrate-co-4-hydroxybutyrate) hydroxybutyrate-co-3-valerate (PHBV), poly-3-hydroxybutyrate-co-3-hydrohexanoate (poly(3-hydroxybutyrate-co-3-hydroxyhaxanoate, PHBH); Poly 3-hydroxybutyrate-co-3-hydroxyunduk-10-enoate (poly(3-hydroxyoctanoate-co-3-hydroxyundec-10-enoate, PHOU) characterized in that any one selected from the group consisting of Bioplastic-based foam sheet. According to claim 1, wherein the polyhydroxyalkanoate-based polymer is poly(3-hydroxyalkanoate (PHA)-based first polymer, thermoplastic starch (TPS), polybutylene succinate (PBS), poly butylene adipate (PBA), polybutylene adipate (PBA), poly(butylene succinate co-butylene adipate) (PBSA), poly(butylene adipate co-terephthalate) (PBAT), poly(butylene adipate co-succinate co-terephthalate) (PBAST), poly(butylene succinate co-L-lactate) (PBSL), polycaprolactone (PCL), polyglycolic acid (PGA), Bioplastic-based foam sheet, characterized in that at least one second polymer selected from the group consisting of polyvinyl alcohol (PVA), polylactic acid (PLA), polyhydroxyalkanoate and aliphatic/aromatic copolymer polyester is blended . [Claim 7] The bioplastic-based foam sheet according to claim 6, wherein the second polymer is contained in an amount of 0.01 to 90 wt%. The method according to claim 1, wherein, based on 100 parts by weight of the polyhydroxyalkanoate-based polymer, 0.01 to 2 parts by weight of a stabilizer and 0.01 to 2 parts by weight of a lubricant Bioplastic-based foam sheet, characterized in that it further contains 2 parts by weight. According to claim 1, wherein the organic peroxide-based crosslinking agent benzoyl peroxide, lauryl peroxide, dicumyl peroxide, dihexyl peroxide, butylcumyl peroxide, dibutyl peroxide, p-methane hydroperoxide, diisopropylbenzene Hydroperoxide, tetramethylbutyl peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-dibutylperoxyhexyne-3, 2,3-dimethyl-2,3-diphenylbutane, 1,1 -di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane , di(2-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-dibutylperoxyhexane, hexyl peroxyisopropyl carbonate, butyl peroxy 2-ethylhexyl carbonate, diisopropyl peroxydi Carbonate, butylperoxyisopropyl carbonate, butylperoxymaleic acid, butylperoxy-3,5,5-trimethylhexanoate, butylperoxylaurate, butylperoxybenzoate, hexylperoxybenzoate, butylperoxy Acetate, n-butyl 4,4-di-butylperoxyvalerate and 2,2-di-butylperoxybutane, characterized in that any one selected from the group consisting of a bioplastic-based foam sheet. The bioplastic-based foam sheet according to claim 1, wherein the plasticizer is selected from an organic acid, an alcohol-based compound, a metal compound, or a citric acid-based compound alone or in a mixed form. According to claim 1, wherein the foaming nucleating agent talc, silica, calcium carbonate, calcium stearate, and montmorillonite (Montmorillonite), characterized in that any one selected from the group consisting of a bioplastic-based foam sheet. The bioplastic according to claim 2, wherein the polyhydroxyalkanoate-based polymer is a polymer in which the repeating structure of 3-hydroxyalkanoate represented by the following formula is crosslinked by an E-beam. Foam sheet based:

In the above, R is a C ₁ to C ₁₃ alkyl group, and a C ₆ to C ₁₀ aryl group. The bioplastic-based foam sheet of any one of claims 1 to 12 is molded and processed to be applied to any one selected from the group consisting of food packaging containers, industrial packaging materials, medical materials, medical clothing, agricultural materials and fishing materials. Biodegradable molded foam products.