TWI871555B - Biomass-based decomposable antibacterial masterbatch and application thereof - Google Patents

Abstract

An biomass-based decomposable antibacterial masterbatch, including: 60~80% by weight of biodegradable polymer plastic material; 10~30% leaf fiber material; 1.0~5.0% inorganic antibacterial materials; 2.0~4.5% plasticizer; 0.2~3.5% chain extender and 0.3~3.5% coupling agent. The aforementioned components are mixed and melted and blended at a temperature of 180~280℃ and then extruded to make granules, which are provided as masterbatches such as stretching, extrusion, blowing, injection or hot compression molding. An antibacterial biodegradable product is a masterbatch component described above, which is blown or co-extruded to form a sheet and then biaxially stretched. The product prepared by the present invention has antibacterial biodegradable masterbatch composition has biodegradable, bacteriostatic, excellent mechanical properties and the release of far infrared rays.

Description

Antibacterial biodegradable masterbatch and its derivatives

The present invention relates to the field of biodegradable plastic technology, and in particular to an antibacterial biodegradable masterbatch and its derivatives that are biodegradable, antibacterial, have excellent mechanical properties and release far infrared rays.

Polylactic acid (PLA) is a material with good processability among current bio-based polymers, and its biodegradability makes it one of the emerging materials that has attracted much attention. However, due to the slow crystallization rate of pure PLA resin, the large shrinkage rate of molded products, poor dimensional stability, inherent brittleness, poor processing thermal stability, and poor product durability, its application as an engineering plastic is limited. Therefore, improving the mechanical and thermal properties of PLA has become the main topic at present, and adding fiber or other reinforcing materials to strengthen PLA is one of the main methods today.

The main methods to improve the strength of PLA are currently using glass fiber reinforcement, natural fiber reinforcement, nanocomposite and filler reinforcement technologies. Natural fibers can be divided into three categories: (1) plant fibers (2) animal fibers (3) mineral fibers.

There are two types of fibers:

1. Artificial fiber, such as seaweed fiber, is a kind of fiber made by mixing sodium alginate fine particles extracted from seaweed plants with nylon or other solutions, spinning and spinning. Seaweed fiber It has excellent antibacterial effect and is currently widely used in various functional fiber fabrics, such as socks, clothing and medical antibacterial cotton.

2. Natural fibers, such as plant fibers, including:

(1) Seed fibers, such as cotton and kapok.

(2) Tough fibers, such as flax, hemp, ramie, and jute.

(3) Leaf fibers, such as Manila hemp, New Zealand hemp, Sisal hemp, Chinois hemp, and Pinus tabacum, etc.

(4) Fruit fiber, such as coconut fiber.

(5) Wood fibers, such as straw, wheat straw, and juniper.

Patent document using (5) wood fiber among the aforementioned plant fibers: Taiwan Publication No. 202243849 discloses a method for preparing a biodegradable plant fiber masterbatch, which discloses the use of any one of corn husks, corn stalks, wheat stalks, rice stalks and bamboo, or a combination of at least any two of them, as a plant fiber reinforcing filler.

Patent literature on the use of (4) fruit fibers and (5) wood fibers among the aforementioned plant fibers:

1. Taiwan Patent Publication No. 202104388 discloses a manufacturing method of an environmentally friendly polymer product and its derivatives, which discloses a method of using cereal powder, coconut shell powder, coffee grounds, rice husk powder, willow powder, bamboo powder, wood powder, bamboo charcoal powder, wipe powder, dragon fruit powder, pomegranate powder, green algae powder or leafy vegetable powder as plant fiber reinforcing fillers.

2. Taiwan Publication No. 202124594 discloses a biodegradable green biomass eco-friendly straw, which discloses the use of wood, sawdust, bamboo stems, peanut shells, water chestnut shells or a combination thereof as plant fiber reinforcing fillers.

Patent document for using (2) twill fiber, (4) fruit fiber and (5) wood fiber among the aforementioned plant fibers: Taiwan Publication No. 202007608 discloses a biodegradable composition, which discloses a method of using at least one of sugarcane fiber, bamboo fiber, coconut fiber, hemp fiber, palm shell fiber, coffee grounds, sake dregs, wheat dregs, cotton, rice stalks, rice husks, corn stalks, starch, bamboo shoots or wood powder as a plant fiber reinforcing filler.

The above-mentioned research literature on toughened fibers: K.Oksman, M.Skrifvars and J.F.Selin, et al. used a twin-screw extruder to produce PLA/flax composite sheets containing 30-40% flax fibers. The strength of the composite sheets was about 50% higher than that of polypropylene/flax composite sheets, and the addition of 30% flax fibers increased the rigidity modulus of PLA from 3.4GPa to 8.4GPa. [K.Oksman, M.Skrifvars and J.F.Selin, "Natural Fibers as Reinforcement in Polylactic Acid (PLA) Composites", Composites Science and Technology, Vol.63, pp.1317-1324, (Reinforcement of Natural Fibers in Polylactic Acid (PLA) Composites in Composites Science and Technology)].

H.L.Seung and W.Siqun et al. added low concentration (0.65%) of lysine-based diisocyanate (LDI) as a coupling agent during the kneading process of PLA/bamboo fiber to improve the tensile strength, water resistance and interfacial adhesion of the composite material. When the bamboo fiber was increased to 30%, the tensile strength of the dumbbell specimen of the material increased by 44% from 29MPa, but the elongation at break in these studies did not improve significantly. 〔H.L.Seung and W.Siqun, "Biodegradable Polymers/Bamboo Fiber Biocomposite with Bio-based Coupling Agent", Composites: Part A, Vol.37, pp.80-91, 2006. (Biodegradable polymer/bamboo fiber biocomposite with bio-based coupling agent)〕.

B.X.Li from National Taiwan University of Science and Technology used 4,4-diphenylmethane diisocyanate (MDI) as a crosslinking agent for polylactic acid and added silicon dioxide to cut the sheet to explore the thermal and mechanical properties of the finished product. When MDI/PLA reached the optimal amount of 0.0025g/2g, the crystallization temperature of PLA could be increased from 53℃ to 64℃, and the tensile strength could be increased from 4.9MPa by about 6%, and the elongation at break could be increased from the original 3% to 5%. 〔B.X.Li, “Effect of the Addition of 4,4-methylene Diphenyl Diisocyanate and Silicate on the Thermal and Mechanical Properties of Polylactide”, National Taiwan University of Science and Technology, Polymer Engineering, 2008.〕。

Y.F.Huang from Tunghai University in Taiwan used melt intercalation to prepare PLA and polymethylmethacrylate (PMMA) transparent composites, and added Paraloid(TM) BPM-515, a new transparent toughening agent, to enhance the impact strength of PLA and the composite. The study showed that increasing the toughening agent to 10% can increase the toughness of PLA by 22%.

Combining the above patent documents and research documents, it can be seen that adding fiber, plasticizer or crosslinking agent has the effect of increasing the toughness of polylactic acid. Its advantage is that it does not need to go through chemical crosslinking or grafting reactions, but can only be prepared by rapid physical mixing.

In view of the fact that the above patent documents do not use leaf fiber and polylactic acid (PLA) biodegradable plastic technology, the inventor feels that it is not perfect, so he has exhausted his mind to carefully study and overcome it. With his many years of accumulated experience in this industry, he has further developed an antibacterial biodegradable masterbatch. The antibacterial biodegradable masterbatch consists of leaf fiber materials, biodegradable polymer plastics, natural inorganic antibacterial materials and additives. After mixing according to the proportion of each component, it is melt-blended at a temperature of 180~280℃ and then extruded into granules. As long as the proportion of each component is adjusted, it can be applied to lamination (paper tableware inner film), blown bag (handbag), biaxial stretching (protective film, food packaging), injection and hot pressing processes to replace PE, PP, PET, PS and PC. The products made by the present invention have improved mechanical properties (bending strength and pulling strength) and antibacterial effects (increased antibacterial activity value), and can be decomposed by microorganisms after recycling without leaving any harmful substances to pollute the environment.

The main purpose of the present invention is to provide an antibacterial biodegradable masterbatch and its derivatives that are environmentally friendly, low-cost, antibacterial and have excellent mechanical properties.

In order to achieve the above-mentioned purpose of the present invention, the technical means adopted are: providing an antibacterial biodegradable masterbatch, which is made of the following components: biodegradable polymer plastic; leaf fiber material; inorganic antibacterial material and additives.

In order to achieve environmental biodegradability, the present invention uses polyhydroxyalkanoate (PHA) or polylactic acid (PLA) as biodegradable polymer plastics, which can be used alone or in combination.

Biodegradable plastics are currently made by taking starch from corn or cassava, fermenting it to produce lactic acid, and then chemically polymerizing it to make the plastic raw material polylactic acid. Many scientists are now studying the use of microorganisms, such as certain molds, yeasts, and bacteria, to produce polyhydroxyalkanoates (PHA) compounds. Compared with polylactic acid (PLA) biodegradable plastics, the toughness and heat resistance of PHA plastic products are better than PLA plastics, and PHA can be 100% decomposed, so it can be used more widely. Therefore, preferably, the biodegradable polymer plastic is polyhydroxyalkanoate (PHA).

The aforementioned polyhydroxyalkanoate (PHA) has stronger toughness and heat resistance than polylactic acid, but the mass production cost of polyhydroxyalkanoate (PHA) is relatively high, while polylactic acid (PLA) is relatively cheap and has good physical properties. Therefore, in actual implementation, it is possible to consider using low-cost polylactic acid (PLA) as a degradable polymer plastic.

The content of polylactic acid (PLA) and polyhydroxyalkanoate (PHA) used in the embodiments of the present invention is not particularly limited, as long as the product can show good composite material properties. The preferred content is 60-80%, and more preferably 65-75%.

In the embodiment of the present invention, the polylactic acid (PLA) is obtained from Taiwan Plastics &Polymers; the polyhydroxyalkanoate (PHA) is selected from Japan KANEKA Corporation , and the tensile strength is 40-60MPa (the tensile strength can be increased by 20-40% (about 80-95MPa) after adding reinforcing fibers).

In order to obtain a certain tensile strength of the product, the present invention uses leaf fiber material as a plastic (biodegradable polymer plastic) reinforcement material. Leaf fiber is obtained from the leaves or sheaths of plants.

There are two types of fiber:

1. Artificial fiber: For example, seaweed fiber, which is a kind of fiber made by mixing sodium alginate fine particles extracted from seaweed plants with nylon or other solutions, spinning and spinning. Seaweed fiber has excellent antibacterial effect and is currently widely used in various functional fiber fabrics, such as socks, clothing and medical antibacterial cotton.

2. Natural fiber: such as plant fiber, which includes: (1) seed fiber (2) veneer fiber (3) leaf fiber (4) fruit fiber (5) wood fiber. Among them, (3) leaf fiber is fiber obtained from the leaves or leaf sheaths of plants, such as pineapple leaf fiber, banana leaf fiber, sisal fiber, ramie fiber, hemp fiber, abaca fiber, etc.

The leaf fiber materials applicable to the present invention are pineapple leaf fiber and carbonized pineapple leaf fiber, which can be used alone or in combination. According to research, pineapple leaf fiber has the characteristics of soft fiber and high strength. Therefore, in the present invention, the leaf fiber material is preferably pineapple leaf fiber.

There is no particular restriction on the content of the leaf fiber material used in the present invention, as long as the product can show good tensile strength. Preferably, the leaf fiber material content is 10-30%, more preferably 15-25%.

In addition, the addition of leaf fiber materials in the present invention can also reduce the amount of biodegradable polymer materials (polyhydroxyalkanoate PHA and polylactic acid PLA), thereby achieving the purpose of reducing costs.

The leaf fiber material used in the embodiment of the present invention is extracted from any one of the pineapple fiber materials obtained by Taiwan Patent TWI593841 (electrochemical extraction method of plant fiber), Taiwan Patent Application No. 111127603 (a method for extracting fiber from plants into particles using acid oxidation and electrolysis) and Taiwan Patent Application No. 111127801 (a method for extracting fiber from plants into particles using freeze-thaw method) approved by the inventor Huang Silun, and is provided by the inventor Huang Silun.

The advantages of the leaf fiber material (pineapple leaf fiber) provided by the inventor are as follows: (1) Pineapple leaf fiber has the characteristics of low cost, soft fiber and high strength. (2) Since the cellulose extracted from pineapple leaves and polylactic acid (or polyhydroxyalkanoate) plastic are natural materials, they can replace the huge and difficult to decompose plastic straws, films and other products in the past. It is a good natural recovery recycling material for reducing environmental harm. (3) It comes from natural plants and is applied to nature. The recycling resource is convenient, and pineapple fiber has excellent water absorption and air permeability. (4) It can reduce the carbon footprint emissions and carbon tax issues of related subsequent products.

According to research reports, carbonized fibers can release far-infrared rays of 8 to 15 μm , which can generate a large number of negative ions and have the effects of disinfection, sterilization and air purification.

In order to enable the present invention to release negative ions and far-infrared rays, carbonized pineapple leaf fibers are used in the leaf fiber material of the present invention.

In the above invention, in order to obtain a product with a certain antibacterial effect, natural degradable antibacterial materials such as organic natural chitosan and inorganic oyster shell powder can be used. Organic natural chitosan has the advantages of natural environmental protection and high safety, but short life, high price and poor heat resistance. Inorganic oyster shell powder has the advantages of natural environmental protection, high safety, long life, low price and good heat resistance. Therefore, the present invention adds natural environmental inorganic material calcined oyster shell powder as an inorganic antibacterial material.

According to research, calcined oyster shell powder has the ability to inhibit Staphylococcus aureus, Escherichia coli, Listeria, Salmonella, Opuntia, Micrococcus luteus, Aspergillus niger and Penicillium cordiformis.

Because oyster shells are roasted at 1300℃ and become calcium oxide, when they come into contact with water, they become calcium hydroxide with oxygen ions, which converts the oxygen in the water into active oxygen. It is a strong alkaline with a pH value of 13. Active oxygen has a strong bactericidal effect and the sterilization speed is very fast. According to research literature, oyster shell powder calcined at 800℃ and 1000℃ has a good antibacterial effect on Escherichia coli and Staphylococcus aureus.

The composition of calcined oyster shells is calcium oxide (CaO) at 54.6%~68%, followed by _CO2 at 43.5%. When heated, the total surface area of oyster shells increases. When the temperature is above 700℃, calcium oxide will change to produce calcium oxide and carbon dioxide. When the temperature is above 900℃, the amount of calcium oxide (CaO) produced reaches the maximum.

Furthermore, the possible antibacterial effect of calcined oyster shell powder is due to the high pH value and the change of super-oxidation reduction potential (ORP). The most suitable pH value for microbial growth is 7.0. When the pH value is greater than 11, microorganisms can hardly grow. Aerobic microorganisms can only grow when the super-oxidation reduction potential (ORP) is positive. The super-oxidation reduction potential (ORP) range for their optimal growth is +200mV~820mV. When the oyster shell is heated to above 800℃, the pH value = 12.18 and ORP = -302.4mV. As the calcination temperature increases, the pH value of the aqueous solution will be higher. As for the excess oxidation-reduction potential (ORP), its negative value will also become larger as the temperature rises. This environment is not conducive to bacterial growth.

In addition, after calcination, oysters will be converted into 54.6%~68% calcium oxide (CaO), with a pH value >12, which is a strong alkaline substance. Its solubility in water is quite low, about 1.29g/L at 20°C. Calcium oxide will generate active oxygen under the induction of hydroxyl groups (OHgroup), among which common active oxygen includes superoxide anion (O ^2- ), peroxyhydrogen radical (HOO ^. ) and hydrogen peroxide (H ₂ O ₂ ), all of which have strong oxidizing ability. In other words, when calcium oxide dissolves in water to form calcium hydroxide [Ca(OH) ₂ )] solution, active oxygen will also be generated.

From the above, we can see that the primary mechanism of calcined oyster shell powder's antibacterial effect is that it can create an environment that is not suitable for bacterial growth under the "strong alkali" of high pH value, thereby achieving the purpose of antibacterial effect. In addition to "strong alkali", calcium oxide is the special and main antibacterial component in calcined oyster shell powder.

The calcined worm shell powder used in the present invention preferably has a content of 1.0-5.0%, more preferably 2.0-4.0%.

The roasted oyster shell powder used in the present invention is roasted and then ground into a particle size of 63~75 microns (μm) (between 200~300 meshes).

In addition, the addition of burnt oyster shell powder inorganic antibacterial material in the present invention can improve the thermal stability of PLA composite materials.

In the above invention, the auxiliary agent includes a solubilizer, a chain extender and a coupling agent.

In order to make biodegradable polymer plastics and leaf fiber materials have better compatibility, the present invention uses diester of adipate as a cold-resistant solubilizer. Diester of adipate (DAIFATTY-101) itself is biodegradable and has excellent compatibility with polylactic acid, and has high plasticizing efficiency. Adding diester of adipate can make polylactic acid (PLA) obtain an elongation of about 300%, which can improve the toughness of polylactic acid products and accelerate the decomposition of discarded products by microorganisms.

Preferably, the content of adipic acid diester is 2.0~4.5%, more preferably 2.0~4.0%.

In order to improve the chemical and mechanical properties of the product, the present invention uses trihydroxymethylpropane (TMP) as a chain expander. PLA is a semi-crystalline polymer. Due to its extremely slow crystallization rate and fast cooling rate in conventional processing technology, it often becomes amorphous after processing, causing the product to become hard and brittle, with poor impact resistance and poor flexibility. Trihydroxymethylpropane has good anti-crystallization properties. As a chain expander for PLA, it can improve the strength and flexibility of the product.

Preferably, the trihydroxymethylpropane (TMP) content is 0.2~3.5%, more preferably 0.2~3.0%.

Furthermore, in order to increase the tensile strength of fibers and polymer plastics, the present invention adds aminopropyltrimethoxysilane (APS) as a coupling agent. Silane coupling agents can hydrolyze the interface between inorganic and organic raw materials to form a bonded bonding layer, improve the interaction between organic polymers and inorganic substrates and fillers, and thus improve the physical and mechanical properties of the product such as surface tension, flexural strength, compressive strength and tensile strength. Its unique molecular structure can give plastics better elasticity and tensile properties. In addition, adding aminopropyltrimethoxysilane as a coupling agent can make leaf fibers and calcined oyster shell powder obtain higher dispersibility in plastics (biodegradable polymer plastics), and improve the mechanical properties of the product.

Preferably, the aminopropyltrimethoxysilane (APS) content is 0.3-3.5%, more preferably 1.0-3.0%.

In addition to the above ingredients, commonly used modifiers in the field, such as ultraviolet absorbers, antistatic agents, flame retardants, lubricants, colorants, anti-wear agents and antioxidants, can be appropriately added to the antibacterial biodegradable masterbatch of the present invention. They can be used alone or in combination. Since these modifiers are known raw materials, they should be well known to those with common knowledge in the technical field to which the present invention belongs, and they are not the main components of the present invention and will not be described in detail.

The modifier used in the present invention can be added in an amount of 0.1~0.5% according to the environmental requirements of use.

An antibacterial biodegradable product, characterized in that the product is made from the antibacterial biodegradable masterbatch of the present invention, wherein the product includes a biaxially stretched polyhydroxyalkanoate film (BOPHA), a straw, disposable tableware, a packaging bag, a packaging paper or a packaging box.

The aforementioned antibacterial biodegradable product is produced using processes such as lamination (paper tableware inner film), blown bags (handbags), biaxial stretching (protective film, food packaging), injection molding and hot pressing.

In order to clearly illustrate the purpose that the present invention can achieve, the following table shows the different components of the control group CE1~CE2 and the experimental group E1~E7 to further illustrate the efficacy and characteristics of the antibacterial biodegradable masterbatch product of the present invention.

The main raw materials used in the embodiments of the present invention are as follows:

(1) Polylactic acid (PLA): selected from Taiwan Uni-Onward Trading Co., Ltd. (UNI-ONWARD CORP), brand name SIA, product name POLYLACTIC ACID. MOLECULAR WEIGHT: 60,000, tensile strength 50MPa.

(3) Pineapple leaf fiber: selected from Feng Chia University in Taiwan (Professor Huang Silun), with an average particle size of 60~75 microns (μm).

(4) Roasted oyster shell powder: selected from Taiwan Plastic Industry Co., Ltd. - antibacterial oyster shell powder with an average particle size of 50~75 microns (μm) and a calcium oxide CaO content of 54.6%~68%.

(5) Adipic acid diester: selected from Daihachi Chemical Industry Co., Ltd., No. DAIFATTY-101.

(6) Trihydroxymethylpropane (TMP): Selected from Taiwan Uni-Onward Trading Co., Ltd. (UNI-ONWARD CORP), brand name ALD, product name TRIMETHYLOLPROPANE, 97wt%.

(7) 4,4-diphenylmethane diisocyanate (MDI): Select the product with an NCO value of 33.5% (by wt NCO groups) from GO YEN CHEMICAL INDUSTRIAL CO LTD (GYC Group).

Please refer to Table 1. The main raw materials and contents used in control groups CE1, CE2 and examples E1 to E7 are as follows:

CE1 components and weight ratio: polylactic acid (PLA) 98%, adipate diester 1.5% and trihydroxymethylpropane (TMP) 0.5%.

CE2 components and weight ratio: polylactic acid (PLA) 97%, calcined oyster shell powder 0.5%, diester of adipate 1.5%, trihydroxymethylpropane (TMP) 0.5% and aminopropyltrimethoxysilane (APS) 0.5%.

E1 components and weight ratio: polylactic acid (PLA) 55%, pineapple leaf fiber 35%, calcined oyster shell powder 0.5%, diester of adipate 1.5%, trihydroxymethylpropane (TMP) 4.0% and aminopropyltrimethoxysilane (APS) 4.0%.

E2 components and weight ratio: polylactic acid (PLA) 60%, pineapple leaf fiber 30%, calcined oyster shell powder 1.0%, diester of adipate 2.0%, trihydroxymethylpropane (TMP) 3.5% and aminopropyltrimethoxysilane (APS) 3.5%.

E3 components and weight ratio: polyhydroxyalkanoate (PHA) 65%, pineapple leaf fiber 25%, calcined oyster shell powder 2.0%, diester of adipate 2.0%, trihydroxymethylpropane (TMP) 3.0% and aminopropyltrimethoxysilane (APS) 3.0%.

E4 components and weight ratio: polyhydroxyalkanoate (PHA) 70%, pineapple leaf fiber 20%, calcined oyster shell powder 3.0%, diester of adipate 3.0%, trihydroxymethylpropane (TMP) 2.0% and aminopropyltrimethoxysilane (APS) 2.0%.

E5 components and weight ratio: polyhydroxyalkanoate (PHA) 75%, pineapple leaf fiber 15%, calcined oyster shell powder 4.0%, diester of adipate 4.0%, trihydroxymethylpropane (TMP) 1.0% and aminopropyltrimethoxysilane (APS) 1.0%.

E6 components and weight ratio: polylactic acid (PLA) 80%, pineapple leaf fiber 10%, calcined oyster shell powder 5.0%, diester of adipate 4.5%, trihydroxymethylpropane (TMP) 0.2% and aminopropyltrimethoxysilane (APS) 0.3%.

E7 components and weight ratio: polylactic acid (PLA) 85%, pineapple leaf fiber 5.0%, calcined oyster shell powder 5.0%, diester of adipate 4.5%, trihydroxymethylpropane (TMP) 0.2% and aminopropyltrimethoxysilane (APS) 0.3%.

After mixing the components and weight ratios of the above-mentioned Examples E1 to E7 and the control groups CE1 and CE2, melt blending was performed at a temperature of 180 to 280°C and then extruded by a screw machine to produce 3 sheets of plates with an average thickness of 3.5 mm (including 1 sheet of 120 mm long × 25 mm wide test piece and 2 sheets of 5 cm long × 5 cm wide test pieces), providing overall performance index tests of mechanical properties (1 sheet) and antibacterial activity values (2 sheets).

Mechanical performance test method:

Specimen type: Specimen length 120mm × width 25mm (1 piece, each piece is 3.5mm thick).

Test item: Tensile test.

Test standard: ASTM D-638. Use Instron Tester to test tensile strength (Tensile Strength), the unit is Mpa.

Antibacterial testing method:

Specimen type: Specimen length 5cm × width 5cm (2 pieces, each piece 3.5mm thick).

Antibacterial testing: Testing standard JIS Z-2801 (ISO 22196).

A

2：有抗菌效果〕；〔A

3強效抗菌〕 Antibacterial Activity Value A〔3

A

2: has antibacterial effect〕;〔A

3. Powerful antibacterial

Test strains: 1. Staphylococcus aureus (ATCC 6538P); 2. Escherichia coli (ATCC 8739); Test bacteria concentration: 2.5×10 ⁵ ~1.0×10 ⁶ CFU/mL, inhibiting the growth or reproduction of microorganisms after 24±1 hours (measuring the antibacterial activity value of the non-porous surface of the plastic specimen).

First, please refer to Table 1, in the control group:

CE1: Tensile Strength is 50MPa. The antibacterial activity against Escherichia coli (ATCC 8739) is A<2, and the antibacterial activity against Staphylococcus aureus (ATCC 6538P) is A<2, indicating no antibacterial effect.

CE2: Tensile Strength is 52MPa. The antibacterial activity A against E. coli (ATCC 8739) is 2.4 (2<A<3), and the antibacterial activity A against Staphylococcus aureus (ATCC 6538P) is 2.3 (2<A<3), showing antibacterial effect.

Please refer to Table 1 again, it can be seen that the tensile strength of Examples E1 to E7 of the present invention is better than that of the control groups CE1 and CE2. Among them:

E2: The tensile strength of 60% polylactic acid (PLA) + 30% pineapple leaf fiber is 80MPa.

E3: The tensile strength of 65% polyhydroxyalkanoate (PHA) + 25% pineapple leaf fiber is 90MPa.

E4: 70% polyhydroxyalkanoate (PHA) + 20% pineapple leaf fiber has a tensile strength of 96MPa.

E5: 75% polyhydroxyalkanoate (PHA) + 15% pineapple leaf fiber has a tensile strength of 91MPa.

E6: 80% polylactic acid (PLA) + 10% pineapple leaf fiber has a tensile strength of 85MPa. It can be seen that embodiments E3 to E5 can obtain better bending strength and tensile strength.

As shown in Table 1, E1 to E7, the purpose of adding pineapple leaf fiber in the present invention is to increase the strength of PLA or PHA. Adding a small amount may not have a good effect on heat deformation temperature, bending strength, tensile strength, etc. However, when the pineapple leaf fiber content reaches a certain proportion (such as E1 adding 35% pineapple leaf fiber), it may cause fiber entanglement and aggregation, resulting in a decrease in mechanical strength (E1 tensile strength drops to 65MPa), but the mechanical properties are still higher than the control group, which may be related to the viscosity of polylactic acid or polyhydroxyalkanoate increasing with the content, because the viscosity increases with concentration. Although the amount of biodegradable polymer plastic (PLA or PHA) added in E3~E5 increased from 65% to 75%, and the amount of pineapple leaf fiber decreased from 25% to 15%, the two contents complemented each other, so that the mechanical properties were still maintained at a considerable level. In addition, pineapple leaf fiber is less expensive than biodegradable polymer plastic (PLA or PHA), so in actual implementation, it is considered to increase the content of pineapple leaf fiber and reduce the amount of biodegradable polymer plastic, such as implementing the E2 and E3 composition ratio of 30:60 or 25:65.

Please refer to E1~E7, which respectively add 0.5%, 1%, 2%, 3%, 4%, 5% and 5% calcined oyster shell powder. It can be seen that when E1 is added at 0.5%, the antibacterial activity values A against Escherichia coli and Staphylococcus aureus are 2.6 and 2.6 (3≧A≧2), respectively, showing antibacterial effect. When E2~E7 are added at more than 1%, the antibacterial activity values A are all greater than 3 (A≧3). Therefore, the present invention has an antibacterial effect when added at 0.5%, but has a strong antibacterial effect when added at more than 1%. When added to 5%, the antibacterial activity value A is around 6. Therefore, the preferred content of the present invention is 1~5%.

The embodiments E1 to E7 in Table 1 all have better mechanical properties and antibacterial properties than the control groups CE1 and CE2. In addition, in order to provide the function of releasing far infrared rays, the present invention can add carbonized pineapple fiber to pineapple fiber to obtain the function of releasing far infrared rays. This technology is already known and does not need to be described again.

The above-mentioned embodiments are descriptions of the preferred implementation methods of the present invention and do not limit the scope of the present invention. Under the premise of not departing from the design spirit of the present invention, various modifications and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the scope of protection determined by the claims of the present invention.

Claims (6)

An antibacterial biodegradable masterbatch is characterized in that the antibacterial biodegradable masterbatch is made of the following components: 60-80% of biodegradable polymer plastic, the biodegradable polymer plastic is selected from polyhydroxyalkanoate (PHA); 10-30% of leaf fiber material, the leaf fiber material is selected from pineapple leaf fiber, carbonized pineapple leaf fiber or a combination thereof; 1.0-5.0% of inorganic antibacterial material, the inorganic antibacterial material is roasted oyster shell powder; and 5.0-9.0% of auxiliary agent. According to the antibacterial biodegradable masterbatch described in claim 1, the particle size of the roasted oyster shell powder is between 63 and 75 microns (μm). According to the antibacterial biodegradable masterbatch described in claim 1, the auxiliary agent includes: 2.0~4.5% of plasticizer, the plasticizer is diester of adipate; 0.2~3.5% of chain expander, the chain expander is trihydroxymethylpropane (TMP); and 0.3~3.5% of coupling agent, the coupling agent is aminopropyltrimethoxysilane (APS). According to the antibacterial biodegradable masterbatch described in claim 3, the additive further comprises 0.1-0.5% of a modifier, and the modifier comprises an anti-ultraviolet agent, an antistatic agent, a flame retardant, a lubricant, a colorant, an anti-wear agent, an antioxidant or a combination thereof. An antibacterial biodegradable product, characterized in that the product is made from the antibacterial biodegradable masterbatch of claim items 1 to 4. An antibacterial biodegradable product according to claim 5, wherein the product includes a biaxially stretched polyhydroxyalkanoate film (BOPHA), a straw, a disposable tableware, a packaging bag, a packaging paper or a packaging box.