JPH08252823A - Manufacture of nonflammable biodegradable plastic - Google Patents

Abstract

PURPOSE: To realize the giving of nonflammability to a plastic by a method wherein molding is carried out under the condition that at least either one of an aluminum hydroxide powder and a magnesium hydroxide powder is added to pellets made of a biodegradable plastic stock. CONSTITUTION: As a means for making a plastic nonflammable, Al(OH)3 or Mg(OH)2 is mixed with stock so as to absorb the heat developing at the burning of the plastic, resulting in resolving and, at the same time, generating water and showing nonflammability due to its heat absorbing action and the generation of water. However, since nonflammability, biodegradability, mechanical properties and the like have mutually contradictory relationships and added hydroxide molecules are coordinated so as to surround the spherulitic structures of the biodegradable plastic, the biodegradability lowers. As a result, by carrying out the molding of the plastic under the condition that the mixing percentage of at least either one of an Al(OH)3 powder and a Mg(OH)2 powder is set to be 30-50wt.%, the physical properties and nonflammability necessary for the plastic can be maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a biodegradable plastic having flame retardancy. Since plastics do not rot when buried in the soil and generate high heat and harmful gas when burned, this treatment is a major problem in terms of maintaining the global environment. Biodegradable plastics have been paid attention to as a breakthrough measure, and have been put into practical use until now mainly for disposable items such as daily sundries, hygiene products, play products.

On the other hand, regarding electrical products, there is a desire to make the casing and the like of biodegradable plastics to facilitate the treatment after collection. When used as electrical products, Japanese Industrial Standards ( JIS) and UL (Under-writer)
It is necessary to meet the flame-retardant standard set in the Laboratory standard, and current biodegradable plastics cannot support it.

[0003]

2. Description of the Related Art Biodegradable plastics are defined in the natural world as plastics that are decomposed into low molecular weight compounds by the involvement of microorganisms. The biodegradable plastics currently in practical use are the following three types. Can be roughly divided into Microorganism-produced polyester Chemically-synthesized polymer compound This is a natural polymer utilization product. This is polyester synthesized by microorganisms, for example,
A polyester composed of 3-hydroxybutyrate (abbreviation 3HB) or 3-hydroxyvalerate (abbreviation 3HV) is used, and a random copolymer of both [P (3HB-
3HV)] has already been commercialized.

Further, is capable of being divided into polyester and polylactic acid, the former uses polyester obtained by condensing dicarboxylic acid and dihydric alcohol, and the latter uses lactic acid fermentation of glucose to produce lactic acid. ,next,
Lactide is cyclized to give lactide, and then lactide is subjected to ring-opening polymerization to produce polylactic acid.

In addition, a natural polymer such as starch or modified polyvinyl alcohol is used as a raw material, and vegetable oil or the like is used as a plasticizer and made into a resin. When these plastics are buried in soil, they are decomposed into low molecular weight compounds by the action of microorganisms such as actinomycetes and Alcaligenes that inhabit the soil, and eventually carbon dioxide (CO ₂ ) , Ammonia (NH ₃ ) and water (H ₂ O)
Becomes a fertilizer for plants.

However, none of the biodegradable plastics that have been put into practical use at present are flame retardant.

[0007]

The biodegradable plastics currently in practical use do not have flame retardancy. Therefore, it is an issue to impart flame retardancy and expand its application to electrical products.

[0008]

[Means for Solving the Problems] The above-mentioned problems are solved by forming pellets made of a biodegradable plastics raw material into aluminum hydroxide [Al (OH) ₃ ] powder or magnesium hydroxide [Mg
This can be solved by adding at least one of (OH) ₂ ] powder and molding.

[0009]

[Function] As a means for making plastics flame-retardant, a flame-retardant agent having a halogen atom, for example, halogenated phthalic anhydride, brominated polyol, etc. is generally added to the raw material to generate when the plastics burn. The flame retardant is decomposed by the heat generated, and the halogen gas generated at that time interrupts the supply of oxygen (O ₂ ). However,
Halogen gas is not a preferable method because it is harmful to the human body.

The inventor has paid attention to a method of incorporating Al (OH) ₃ or Mg (OH) ₂ into the raw material as a means for making plastics flame-retardant. (For example, JP-A-63-183960 and JP-A-63-198212) In this method, the heat generated when the plastics are burned is absorbed by these materials and decomposed, and water (H ₂ O) is generated.
And shows flame retardancy due to the endothermic action and the generation of water.

2Al (OH) ₃ → Al ₂ O ₃ + 3H ₂ O − 73 kcal (1) However, the problem in adding such a flame retardant is that the flame retardant is proportional to the amount added. The properties are conspicuous, and the physical properties such as biodegradability and mechanical properties are deteriorated and there is a contradictory relationship.

That is, it is considered that the added hydroxide molecules are coordinated so as to surround the spherulite structure of the biodegradable plastics, resulting in a decrease in biodegradability. Therefore, in the present invention, at least one of Al (OH) ₃ powder and Mg (OH) ₂ powder is added in a range that maintains the physical properties and flame retardancy required by plastics, and molding is performed. Good results could be obtained by setting the mixing ratio to about 30%.

Next, an injection molding method (Injecti
On-mold) is often used, but biodegradable plastics generally have a low melting point and are easily decomposed, so in order not to impair biodegradability, treat them at a temperature near the melting point of the plastics in the shortest possible time. According to the experiment, the residence time in the cylinder of the kneading machine is 3 seconds or less, the residence time in the cylinder of the injection molding machine is 7 seconds or less, and the melting temperature is higher than the melting temperature of the plastics. Good results could be obtained by keeping the temperature within + 30 ° C.

[0014]

【Example】

Example 1 As the biodegradable plastics, pellets of an aliphatic polyester (product name Bionore, product number # 1020, Showa High Polymer) belonging to a chemically synthesized polymer compound were used, and as Al (OH) ₃ , the purity was 99.8%. Particle size 5 ~ 10μm
The mixing ratio of the two is 90:10 to 50:50.
It changed into 5 steps.

As the kneading conditions, a Labo Plastomill (Toyo Seiki) is used as the kneading machine, and the nozzle temperature is 11
5 to 120 ° C, torque 4 to 6 kg, residence time within 3 seconds, and injection conditions are injection molding machine (product name).
(JC-25SS, Japan Steel Works) using an injection temperature of 134-144.
℃, injection time 7 seconds, cooling temperature 20-40 ℃, cooling time 15-20
Sec, performed under conditions of injection pressure ^{300 ~450 kgf / cm 2, 60} × 20
A test piece of × 2 mm was prepared.

Then, the test piece was used to measure the mechanical properties and flame retardancy (according to JIS A1321). The method is to hold the test piece vertically and place the gauze on the lower side of the test piece 305 mm, heat the lower end of the test piece with a casverner for 10 seconds to ignite, and then continue burning, or The purpose of this test is to investigate whether or not the gauze burns after the burned and melted drops fall onto the gauze. 1. Mechanical Properties Al (OH) ₃ Content Tensile Yield Stress (kgf / mm ² ) Specified Bending Strength (kgf / mm ² ) 0% 2.9 2.1 10% 2.8 2.2 20% 2.5 2.3 30% 2.4 2.8 40% 2.2 3.0 50% 2.2 2.8 From these results, it can be seen that the tensile yield stress gradually decreases and the flexural strength gradually increases and saturates as the content of the flame retardant increases. 2. Flame-retardant test Content of Al (OH) ₃ Situation after separation of flame Situation of ignition on gauze 0% Continue to burn 10% Continue to burn 20% Continue to burn 30% Continue to burn 30% Do not burn 40% Do not burn No 50% extinguished No ignition This result shows that at least 30% of Al (OH) ₃ must be contained to have flame retardancy. 3. Effect of kneading temperature and injection molding temperature on biodegradability The above-mentioned aliphatic polyester (Product name: Bionore, Product number: # 10)
(20, Showa High Polymer) containing 30% of Al (OH) ₃ and changing the kneading temperature and injection molding temperature to make a test piece, which was buried in soil for 100 days and biodegraded. The sex was measured. The melting temperature of Bionore # 1020 is 114 ° C. Conditions with low processing temperature (kneading temperature 115-120 ℃, injection temperature 134-144 ℃) ・ ・ ・ ・ ・ ・ ・ 10% reduction in weight High-processing condition ( Kneading temperature 125-140 ℃, injection temperature 160-170 ℃) ・ ・ ・ ・ ・ ・ 2% reduction in weight From these results, in order not to impair biodegradability It is understood that the molding temperature should be kept as low as possible.

[0017]

EFFECTS OF THE INVENTION By implementing the present invention, it is possible to impart flame retardancy to biodegradable plastics. For that purpose, it is necessary to add about 30% by weight of Al (OH) ₃ powder or Mg (OH) ₂ powder. In addition, molding must be performed at a temperature as close as possible to the melting temperature of plastics.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C08K 3/20 KJR C08K 3/20 KJR 3/26 KAD 3/26 KAD // C08L 67/04 LPM C08L 67 / 04 LPM

Claims (2)

[Claims] 1. A method for producing a flame-retardant biodegradable plastics, which comprises adding at least one of aluminum hydroxide powder and magnesium hydroxide powder to a pellet made of a raw material of biodegradable plastics, and molding. 2. The method for producing a flame-retardant biodegradable plastics according to claim 1, wherein the content of the aluminum hydroxide powder or the magnesium hydroxide powder is 30 to 50% by weight.