JP2019034994A - Hygroscopic antibacterial resin composition and molded body - Google Patents

Abstract

To provide a moisture absorbing antibacterial resin composition capable of molding a molded body having antibacterial effect at a low addition amount since deterioration of a substrate resin is low and dispersibility of antibacterial agent is good, and the molded body.SOLUTION: The above described problem is solved by a moisture absorbing antibacterial resin composition containing shell burning calcium (A) having average particle diameter of 3 to 20 μm and time till moisture absorbing amount reaches equilibration under temperature of 23°C, humidity 50%RH environment of 65 to 130 hrs, and a thermoplastic resin (B), and a molded body by molding the moisture absorbing antibacterial resin composition.SELECTED DRAWING: None

Description

  The present invention relates to a hygroscopic antibacterial resin composition that can be used in a molded product that can suppress odor and bacterial growth.

  In Japan, the emergence of Escherichia coli O-157 and MRSA has further enhanced awareness and interest in hygiene, and attention has been focused on antibacterial products in the food hygiene and medical fields. In order to impart an antibacterial function to a plastic molded body, a method of kneading an antibacterial agent into plastic is used, and many antibacterial agents are used. There are organic and inorganic antibacterial agents, and organic antibacterial agents are more effective than inorganic antibacterial agents, are easy to process and cost less, but are less durable. On the other hand, an inorganic antibacterial agent is inferior in immediate effect to an organic antibacterial agent, but is excellent in sustainability and has a low influence on the human body. Therefore, many inorganic antibacterial agents are used in food-related products and products that come into contact with the human body.

  Examples of the inorganic antibacterial agents include supported antibacterial agents in which metals such as silver, copper, and zinc having antibacterial properties are supported on an inorganic carrier such as zeolite and silica alumina, and calcium hydroxide and calcium oxide (patents) References 1, 2). Supported antibacterial agents are widely used from the viewpoint of safety and durability, but they react with additives such as metal ions and catalyst residues in the resin, antioxidants, antistatic agents, etc. May change color. Therefore, an unexpected problem occurs due to the blending in the plastic molded body. On the other hand, although calcium hydroxide and calcium oxide do not show discoloration due to the reaction with the additive, they require deterioration promotion of the base resin due to high basicity and increase in the amount added due to difficult dispersion, resulting in a decrease in physical properties. Therefore, Patent Document 3 discloses a synthetic resin molded product in which a calcined powder mainly composed of calcium oxide obtained by calcining shells at a high temperature is dispersed.

JP 2008-001557 A JP 2017-030842 A JP 2010-195013 A

  Calcium oxide reacts with water to become calcium hydroxide and exhibits antibacterial properties.However, when kneaded with resin, it partially absorbs moisture in the feeder, and the resin deteriorates due to high temperature during extrusion. Trigger. In addition, when calcium oxide is partially hydrated, calcium oxide aggregates even if extrusion is performed, so that the amount added is increased in order to obtain an effect. Therefore, there has been a problem of deterioration of physical properties.

  An object of the present invention is to provide a hygroscopic antibacterial resin composition and a molded article that can form a molded article having a highly durable antibacterial effect, little deterioration of the base resin, and good dispersibility of the antibacterial agent. .

  As a result of intensive studies in order to solve the above problems, the present inventors have found that the above-described problems can be solved by using a specific shell-shell calcined calcium and a thermoplastic resin. The present invention has been made based on this finding.

  That is, the present invention relates to shell calcined calcium (A) having an average particle diameter of 3 to 20 μm, a temperature of 23 ° C., and a humidity of 50% RH in which the time until moisture absorption reaches equilibrium is 60 to 130 hours, It is a hygroscopic antibacterial resin composition containing a plastic resin (B).

  According to the present invention described above, processing is performed with calcined shell calcium (A) having an average particle size of 3 to 20 μm, a temperature of 23 ° C., and a humidity of 50% RH in which the time until moisture absorption reaches equilibrium is 60 to 130 hours. In addition to being able to suppress hydration reaction at the time, and to suppress aggregation and deterioration of the base resin, antibacterial properties were improved in a small amount. As a result, the molded article using the hygroscopic antibacterial resin composition has an effect of having high antibacterial properties while maintaining the physical properties of the substrate.

  According to the present invention, since the base resin is hardly deteriorated and the dispersibility of the antibacterial agent is good, it is possible to provide a hygroscopic antibacterial resin composition and a molded body that can form a molded body having an antibacterial effect with a low addition amount.

  The hygroscopic antibacterial resin composition of the present invention has an average particle size of 3 to 20 μm, a temperature of 23 ° C., and a humidity of 50% RH. And a thermoplastic resin (B). With this hygroscopic antibacterial resin composition, a molded body can be obtained by extrusion molding, injection molding or the like. This molded body is preferably used for food packaging materials, films, medical films and the like.

  In the present invention, calcined calcium shell is an antibacterial agent effective against bacteria such as Escherichia coli, Salmonella, Pseudomonas aureus, MRSA, O-157, Vibrio parahaemolyticus, Legionella, Trichophyton, and Norovirus. It also has a deodorizing effect on acidic odorous substances such as hydrogen sulfide and isovaleric acid. Shell-calcined calcium is obtained by baking shells such as oysters, scallops, turban shells, and clams at high temperatures. Among them, scallop shells are mainly composed of calcium carbonate, accounting for 90% or more of the composition. The main component of scallop shells is similar to limestone and industrial calcium carbonate, and no harmful substances such as mercury and cadmium are found. Furthermore, since the amount of waste reaches several hundred thousand tons per year, it is preferable from the viewpoint of recycling. The antibacterial agent of the present invention is shell calcined calcium obtained by calcining a shell, and by calcining, carbon dioxide is released from calcium carbonate which is the main component of the shell and becomes calcium oxide. Calcium oxide in the molded body reacts with water to form calcium hydroxide, and exhibits antibacterial properties due to the basicity of calcium hydroxide. Furthermore, radicals are generated when reacting with water, and it is thought that strong reactivity attacks the cell walls of bacteria and exerts stronger antibacterial properties. Shell-calcined calcium (A) has a large difference in reaction with water compared to mineral-derived calcium oxide. The mineral system reacts violently and generates heat up to around 300 ° C., whereas the shell calcined calcium reacts mildly with water and generates heat only up to about 90 ° C. Therefore, the base resin is less deteriorated and can be used as a safe antibacterial agent.

In the present invention, the average particle size of the calcined shell calcium (A) is 3 to 20 μm. Composition by absorption of moisture before forming a molded product by having a mean particle size of 3 to 20 μm, a temperature of 23 ° C. and a humidity of 50% RH in a range of 60 to 130 hours until the amount of moisture absorption reaches equilibrium. And the accompanying aggregation can be suppressed. Furthermore, immediate effect of antibacterial effect can be expected. Preferably it is 3-15 micrometers, More preferably, it is 5-15 micrometers. In addition, the time until the moisture absorption reaches equilibrium is preferably 70 to 120 hours, more preferably 70 to 110 hours.
In addition, an average particle diameter averages the particle diameter (for example, about 20 particles) which can be observed from the enlarged image (for example, 1000 times-10,000 times) of a scanning electron microscope. A known particle shape such as a spherical shape or an ellipsoid shape can be used as the particle shape of the shell-fired calcium (A). The average particle diameter in the case where the shell calcined calcium (A) particles have an aspect ratio (major axis / minor axis) averages the major axis.
In addition, the determination of the time until the amount of moisture absorption reaches equilibrium under a temperature of 23 ° C. and a humidity of 50% RH has reached equilibrium when the change in weight is 1.0% or less after 24 hours from the base time. Shall.

  The calcining temperature of the shell calcined calcium (A) is preferably 900 ° C. or higher and 1 hour or longer, more preferably 900 ° C. or higher and 2 hours or longer. If it is less than 900 degreeC, baking will not be completed completely and there exists a possibility that a calcium carbonate may remain partially.

A conventionally known thermoplastic resin can be used for the thermoplastic resin (B) of the present invention.
Specific examples include polyethylene, polypropylene, vinyl chloride resin, ethylene vinyl acetate copolymer, ABS and the like. Among these, polyethylene, polypropylene, and ABS are preferable from the viewpoint of processability and mechanical properties.
The melting point of the thermoplastic resin (B) is preferably 100 to 170 ° C, and more preferably 110 to 150 ° C. By being in this range, the resin can be easily degassed without applying an excessive heat history during extrusion processing, and the hydration reaction of the calcined shell shell calcium is suppressed, so that resin degradation can be reduced.

Further, the hygroscopic resin composition of the present invention has a surface of the thermoplastic resin (B1) as a main component, shell calcined calcium (A), and a thermoplastic resin (B2) different from the thermoplastic resin (B1). Both of these are preferably a hygroscopic resin composition obtained by physical adsorption at 90 to 140 ° C. and then melt-kneading.
That is, the time until the amount of moisture absorption reaches equilibrium in the environment of an average particle diameter of 3 to 20 μm, a temperature of 23 ° C., and a humidity of 50% RH on the surface of the thermoplastic resin (B1) as the main component is 60 to 130 hours. A hygroscopic resin composition in which the calcined shell calcium (A) and the thermoplastic resin (B2) different from the thermoplastic resin (B1) are both physically adsorbed at 90 to 140 ° C. and further melt-kneaded. It is preferable that it is a manufacturing method.
Here, the main component means a resin having the largest content among the resins constituting the resin composition. For example, when two kinds of resins are contained, the resin composition is formed. In the total amount (100% by weight) of the resin component used in the above, it means a resin containing 50% by weight or more, preferably a resin containing 70% by weight or more.

  At this time, it is preferable that the thermoplastic resin (B1) as the main component is a thermoplastic resin having a melting point of 100 to 170 ° C. Further, as the thermoplastic resin (B2) different from the thermoplastic resin (B1) as the main component, a known thermoplastic resin can be used, but low molecular weight polyethylene and polypropylene are preferable, and a molecular weight of about 2000 to 10000 is preferred. A thermoplastic resin having (MW) is more preferable. Moreover, it is preferable that melting | fusing point is 5-30 degreeC lower than a thermoplastic resin (B1). As a result, only the thermoplastic resin (B2) is melted without melting the thermoplastic resin (B1) as a main component at the time of pre-stirring, so that physical adsorption with the shell calcined calcium is performed on the surface of the thermoplastic resin (B1). The more dispersible the calcined shell calcium is.

  In addition, the blending amount of the thermoplastic resin (B2) is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the thermoplastic resin (B1) from the viewpoint of uniform surface coating. More preferably, it is 5 to 15 parts by weight.

  In the present invention, the average particle diameter (D) and the molded body thickness (d) of the calcined shell calcium (A) preferably satisfy the formula (1) 1 / 2D ≦ d ≦ 50D. The deodorant and antibacterial effects are due to the alkalinity of calcium hydroxide obtained by hydration of shell calcined calcium. Therefore, after the shell calcined calcium in the resin is hydrated, the effect is obtained by contact with bacteria or odorous substances. Therefore, when the average particle diameter is close to the molded body thickness, hydration and contact are likely to occur, and deodorization and antibacterial effects are more likely to be obtained. However, if the thickness of the molded body is too thin than the average particle diameter, the mechanical properties may be deteriorated. Therefore, D ≦ d ≦ 30D is more preferable, and 2D ≦ d ≦ 20D is more preferable. From the viewpoint of hydration and contact of the calcined calcium shell, a preferable range of the molded body thickness is 5 to 300 μm, more preferably 5 to 200 μm.

The molded article of the present invention can be produced by molding a hygroscopic antibacterial resin composition as described above.
The compounding amount of the calcined shell shell calcium and the thermoplastic resin contained in the molded body varies depending on the use and the thickness of the molded body, but the calcined shell calcium (A) is 0.5 to 5 with respect to 100 parts by weight of the thermoplastic resin (B). It is preferable to mix | blend a weight part, More preferably, it is 0.5-3 weight part, Especially preferably, it is 1.0-3 weight part.

  The method for producing the hygroscopic resin composition of the present invention is preferably produced as a pellet-shaped master batch in which shell calcined calcium (A) is blended at a high concentration. Master batch can be manufactured by melt-kneading shell calcined calcium (A) and thermoplastic resin (B) and further forming into pellets, from the viewpoint of preventing aggregation of shell calcined calcium and moisture absorption before melt kneading, The calcined calcium (A) is physically adsorbed on the surface of the thermoplastic resin (B) together with a thermoplastic resin different from the thermoplastic resin (B) at 90 to 140 ° C., and then melt-kneaded to absorb the hygroscopic antibacterial resin. It is preferred to obtain a composition. Here, the physical adsorption method before melt-kneading is preferably a high-speed shear mixer, such as a Henschel mixer or a super mixer. The calcined shell calcium (A) is preliminarily dispersed in the hygroscopic antibacterial resin composition as a master batch, and then blended (melted) with a diluted resin rather than blending a considerable amount contained in the molded body at the time of molding. When a desired molded body is manufactured by kneading, it becomes easy to uniformly disperse the shell calcined calcium (A) in the molded body. Specifically, the masterbatch preferably contains 20 to 120 parts by weight of calcined shell calcium (A) per 100 parts by weight of the thermoplastic resin (B). The melt-kneading is preferably performed using, for example, a single-screw kneading extruder, a twin-screw kneading extruder, or a tandem twin-screw kneading extruder. Moreover, although the melt kneading temperature changes with kinds of thermoplastic resin (B), it is about 150-250 degreeC normally.

  The hygroscopic antibacterial resin composition of the present invention can contain an antioxidant, a light stabilizer, a dispersant and the like as optional components other than the calcined shell shell calcium (A) and the thermoplastic resin (B).

  The hygroscopic antibacterial resin composition of the present invention can be used as a molded article such as a film or a sheet. These molded products can be molded using a T-die film molding machine, an inflation film molding machine, a calender roll molding machine or the like.

  The hygroscopic antibacterial resin composition of the present invention is preferably, for example, a food film, a food bag, a cooking glove, or a medical film.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. Hereinafter, “part” means “part by weight” and “%” means “% by weight”.

  Moreover, the average particle diameter of shell-calcined calcium and the measuring method of hygroscopicity are as follows.

<Average particle size of calcined shell calcium>
The average particle diameter is an average of 20 particles by a magnified image of 1,000 times with a scanning electron microscope. Further, the average particle diameter when the particle shape of the calcined shell calcium (A) has an aspect ratio (major axis / minor axis) is the average of the major axis.

<Hygroscopicity of calcined calcium shells>
The time until the amount of moisture absorption reached equilibrium in a temperature 23 ° C., humidity 50% RH environment was measured by the following method.
Under a temperature of 23 ° C. and a humidity of 50% RH, shell calcined calcium was weighed so as to be approximately 3 g thin and flat in a petri dish (φ100 mm), and the weight was measured at regular intervals. If the change in weight was 1.0% or less after 24 hours from the weight measurement, the equilibrium was reached.

  The raw material used for an Example and a comparative example is shown below. Although the example of the manufacturing method of calcination shell calcium is shown below, it cannot be overemphasized that a manufacturing method is not limited to the following method.

[Production Example 1 of calcined shell shell calcium]
After the shell was washed with water and dried, a coarsely crushed shell with a particle size of about 10 mm was obtained using a coarse pulverizer. Next, the coarsely crushed shell was filled in a ceramic container and baked at 1000 ° C. for 2 hours with a baking device, and then the baked product was obtained with a fine pulverization device to obtain shell-calcined calcium (A-1) having an average particle diameter of 5 μm.

  By changing the baking conditions of the shell-calcined calcium (A-1) to obtain shell-calcined calcium and changing the pulverization conditions, the shell-calcined calcium (A-2) to (A-) having the average particle diameters shown in Table 1 are obtained. 8) was produced.

  Table 1 shows the time until the average particle size and moisture absorption of the calcined shell calcium reached equilibrium.

<Thermoplastic resin>
(B-1) Polyethylene (Suntech LD 2270, melting point 113 ° C., manufactured by Asahi Kasei Chemicals Corporation)
(B-2) Polypropylene (Prime Polypro J226T melting point 141 ° C., manufactured by Prime Polymer Co., Ltd.)
(B-3) Low molecular weight polyolefin (high wax NL800, melting point 103 ° C., manufactured by Mitsui Chemicals)
(B-4) Low molecular weight polyolefin (high wax NP056 melting point 132 ° C., manufactured by Mitsui Chemicals, Inc.)

[Example 1]
60 parts by weight of thermoplastic resin (B-1) and 40 parts by weight of calcined shell shell calcium (A-1) are put into a single screw extruder (manufactured by Ikekai Co., Ltd.) through separate supply ports and melt-kneaded at 190 ° C. A pellet-like hygroscopic antibacterial resin composition (masterbatch) was obtained using a pelletizer.

  3.1 parts by weight of the obtained master batch and 100 parts by weight of the thermoplastic resin (B-1) are melt-kneaded, and a film is formed at a temperature of 210 ° C. using a T-die film forming machine (manufactured by Toyo Seiki Co., Ltd.). Molding was performed to obtain a molded body as an antibacterial film.

[Examples 2 to 7]
An antibacterial film was obtained by carrying out in the same manner as in Example 1 except that the raw materials and blending amounts of Example 1 were changed as described in Table 2.

[Example 8]
After mixing 50 parts by weight of thermoplastic resin (B-1), 10 parts by weight of thermoplastic resin (B-3) and 40 parts by weight of calcined calcium shell (A-2) at 105 ° C. for 5 minutes with a high-speed stirrer. The obtained preliminary mixture was put into a single screw extruder (manufactured by Ikegai Co., Ltd.) and melt kneaded at 190 ° C., and a pellet-like hygroscopic antibacterial resin composition (master batch) was obtained using a pelletizer.

  3 parts by weight of the obtained master batch and 97 parts by weight of the thermoplastic resin (B-1) are melt-kneaded, and film forming is performed at a temperature of 210 ° C. using a T-die film forming machine (manufactured by Toyo Seiki Co., Ltd.). To obtain an antibacterial film.

[Examples 9 to 11]
An antibacterial film was obtained in the same manner as in Example 8, except that the raw materials and blending amounts of Examples 9 to 11 were changed as described in Table 2.

[Comparative Examples 1-6]
Comparison was made in the same manner as in Example 1 except that the calcined shell calcium (A-1) and the thermoplastic resin (B) of Example 1 were changed to the compositions and blending amounts (parts by weight) shown in Table 3. The antimicrobial film of Examples 1-6 was obtained.

[Comparative Example 7]
Except that the calcined shell calcium (A-2) was hydrated in advance to obtain calcium calcined shell shell calcium (AC-1), and the composition and blending amount (parts by weight) shown in Table 3 were changed. In the same manner as in Example 1, an antibacterial film was obtained.

[Reference Examples 1 and 2]
Reference was made in the same manner as in Example 1 except that the calcined shell calcium (A-1) and the thermoplastic resin (B) of Example 1 were changed to the compositions and blending amounts (parts by weight) shown in Table 3. The antimicrobial films of Examples 1 and 2 were obtained.

[Reference Example 3]
Without using an antibacterial agent, only the thermoplastic resin (B) listed in Table 3 was used to form a film at a temperature of 210 ° C. using a T-die film molding machine (manufactured by Toyo Seiki Co., Ltd.) to obtain a film. .

  The obtained antimicrobial film or hygroscopic antimicrobial resin composition was evaluated according to the following criteria. The evaluation results are shown in Table 4.

<Antimicrobial properties>
The obtained antibacterial film was evaluated in accordance with JIS Z 2801: 2010 “Antimicrobial processed product—antibacterial test method / antibacterial effect”. A test bacterial solution (Staphylococcus aureus or Escherichia coli) is inoculated on the surface of the film cut into 5 cm squares, and the coated film is placed on the surface to be adhered. This was stored at 35 ° C. for 24 hours, and the number of viable bacteria per 1 cm ^{2 of} the specimen was measured.

<Tensile strength>
A press sheet was produced at 210 ° C. using the obtained master batch, and a No. 2 dumbbell tensile test piece was produced from the press sheet (thickness 1 mm). Then, it left still for 24 hours in temperature 23 degreeC and humidity 50% RH environment, and measured the breaking strength with the tensile tester.
As a comparison, No. 2 dumbbell tensile test pieces made of only the same resin as the obtained masterbatch, each containing no shell calcined calcium or the like, were prepared, and the strength at break was measured. The breaking strength was evaluated according to the following criteria.
It can be said that the higher the retention rate, the less the resin deteriorates.

A: Compared to the tensile strength at break of only thermoplastic resin not containing calcined shell calcium,
Retention rate 80% or more ○: Compared to the tensile strength at break of only thermoplastic resin not containing calcined shell calcium,
Retention ratio 70 to less than 80% Δ: Compared to the tensile strength at break of only a thermoplastic resin not containing calcined shell shell calcium,
Retention rate 40 to less than 70% x: Compared to the tensile strength at break of only a thermoplastic resin not containing calcined shell shell calcium,
Retention rate less than 40%

<Dispersibility>
The hygroscopic antibacterial resin composition was passed through a single screw extruder so that the amount of calcined shell calcium was 1 kg, and the dispersibility was evaluated by increasing the resin pressure in the extruder. Since the resin pressure rises due to the adhesion of calcined calcium shells to the wire mesh (mesh size 130 μm) installed at the tip of the single screw extruder, the smaller the resin pressure rise, the better the dispersibility, and the evaluation was based on the following criteria: .

A: Resin pressure rise is 2 MPa or less B: Resin pressure rise exceeds 2 MPa, 5 MPa or less Δ: Resin pressure rise exceeds 5 MPa, 15 MPa or less X: Resin pressure rise exceeds 15 MPa

  From the results of Table 4, Examples 1 to 11 obtained excellent antibacterial properties, tensile strength, and dispersibility in all evaluation items. In the present invention, by using shell calcined calcium having an average particle size of 3 to 20 μm, a temperature of 23 ° C., and a humidity of 50% RH in an environment where the amount of moisture absorption reaches equilibrium is 60 to 130 hours. Results superior in antibacterial properties, tensile strength and dispersibility were obtained compared with calcium oxide or calcium hydroxide.

Claims (4)

  Calcined shell shell calcium (A) having a mean particle size of 3 to 20 μm, a temperature of 23 ° C., and a humidity of 50% RH in an amount of 60 to 130 hours until the moisture absorption reaches equilibrium, and a thermoplastic resin (B) A hygroscopic antibacterial resin composition comprising:   2. The hygroscopic antibacterial resin composition according to claim 1, wherein the thermoplastic resin (B) has a melting point of 100 to 170 ° C. 3. A method for producing a hygroscopic antibacterial resin composition comprising shell calcined calcium (A) and a thermoplastic resin (B),
The thermoplastic resin (B) includes a thermoplastic resin (B1) and a thermoplastic resin (B2),
On the surface of the thermoplastic resin (B1) as the main component, the time until the moisture absorption reaches equilibrium in an environment with an average particle diameter of 3 to 20 μm, a temperature of 23 ° C., and a humidity of 50% RH is 60 to 130 hours. A hygroscopic resin composition in which shell calcined calcium (A) and a thermoplastic resin (B2) different from the thermoplastic resin (B1) are both physically adsorbed at 90 to 140 ° C. and then melt-kneaded. Production method. The average particle size (D) of the shell-calcined calcium (A) and the thickness (d) of the molded body satisfy the following formula (1) and 100 parts by weight of the thermoplastic resin (B), The molded article formed by molding the hygroscopic antibacterial resin composition according to claim 1 or 2, wherein

Formula (1) 1 / 2D <= d <= 50D