JPH0812738A - Biodegradable sericin-containing polyurethane and its production - Google Patents

Abstract

PURPOSE:To obtain a biodegradable sericin-containing polyurethane excellent in mechanical and thermal properties inexpensively by reacting an organic solvent solution of sericin with a polyisocyanate. CONSTITUTION:An organic solvent solution of sericin (the organic solvent used being tetrahydrofuran, dioxane or the like which may contain a polyether or polyester polyol compound commonly used and being desirably a liquid one) is reacted with a polyisocyanate (including an aliphatic, alicyclic or aromatic polyisocyanate and a modified product thereof). Because the obtained polyurethane contains biodegradable sericin as its segment, it is biodegradable, excellent in mechanical and thermal properties, and used in the form of film, molding, fiber or the like. This polyurethane is cheap because it can be produced by using serine which is a waste product.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable polyurethane and a method for producing the same.

[0002]

2. Description of the Related Art Unlike the natural polymers that have existed since ancient times, the synthetic polymers that have been produced so far are difficult to incorporate into the natural circulation system, so that waste plastics cause deterioration of the global environment and pose a major problem. Has become.

The inventors of the present invention have been earnestly researching a method for imparting biodegradability to a synthetic polymer, and found that a polyurethane having sericin incorporated in the molecule is decomposed by microorganisms and has excellent mechanical properties. It was found to have physical properties and thermal properties.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a novel polyurethane having biodegradability and excellent physical properties and a method for producing the same.

[0005]

According to the present invention, there is provided a biodegradable polyurethane containing a segment consisting of sericin.

According to the present invention, there is provided a method for producing a biodegradable polyurethane, which comprises reacting polyisocyanate with a solution of sericin in an organic solvent.

[0007] The sericin used in the present invention is a waste by-produced during the refining of raw silk, and can be separated and recovered from the refining wastewater of raw silk.

The polyurethane of the present invention contains a segment consisting of sericin, and is produced by dissolving sericin in an organic solvent, adding polyisocyanate to the solution, and polymerizing it. To obtain a polyurethane film or resin, the polymerization product is cured by a catalyst or heating. To obtain a foam, water, a foaming agent and a catalyst are added to the polymerization product and reacted. Such a reaction method is well known in the art and can be carried out by a conventionally known method.

The polyisocyanate includes aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and modified products thereof. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, and examples of the alicyclic polyisocyanate include isophorone diisocyanate. As the aromatic polyisocyanate, for example, tolylene diisocyanate,
Examples thereof include xylylene diisocyanate, diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tris (isocyanatophenyl) thiophosphate. Examples of the modified polyisocyanate include urethane prepolymer, hexamethylene diisocyanate buret, hexamethylene diisocyanate, trimer, and isophorone diisocyanate trimer.

As an organic solvent for dissolving sericin,
Any substance that dissolves sericin such as tetrahydrofuran or dioxane may be used. In addition, a polyether-based or polyester-based polyol compound that is generally used in the past can be added and dissolved in the sericin solution.
This polyol compound also reacts with polyisocyanate.

Examples of such polyol compounds include ethylene glycol, diethylene glycol,
1,4-butanediol, 1,6-hexanediol,
Low molecular weight polyols such as neopentyl glycol, trimethylolpropane, glycerin, triethanolamine, sorbitol; polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide / propylene oxide copolymers; polycaprolactone, poly β -Methyl-δ-butyrolactone, polyesters from diols and dibasic acids, and the like. Other examples include hydroxyl group-containing liquid polybutadiene, polycarbonate diol, acrylic polyol, and the like.

In the present invention, a liquid polyol compound can be preferably used as the organic solvent for dissolving sericin. The ratio of the sericin and the polyol compound used is 1 part by weight of sericin and 0 of the polyol compound.
The proportion is -50 parts by weight, preferably 0-30 parts by weight.

The proportion of polyisocyanate used is 100 parts by weight of the total amount of sericin and the polyol compound.
The proportion is 10 to 1,000 parts by weight, preferably 10 to 900 parts by weight. In the case of obtaining a foam, water as a foaming agent is 0.1 to 20 parts by weight with respect to 100 parts by weight of the total amount of sericin, a polyol compound and diisocyanate,
It is preferably used in a proportion of 0.5 to 10 parts by weight.

According to the present invention, when a polyol compound is used as a solvent, sericin: 5 to 90% by weight, preferably 10 to 70% by weight, polyol compound: 5 to 9
A polyurethane consisting of 0% by weight, preferably 10-70% by weight, polyisocyanate 5-90% by weight, preferably 10-70% by weight, can be obtained. When a solvent other than the polyol compound is used as the solvent,
Sericin: 5 to 90% by weight, preferably 10 to 70% by weight, polyol compound: 0 to 90% by weight, preferably 1
0 to 70% by weight, polyisocyanate 5 to 90% by weight,
A polyurethane comprising preferably 10 to 70% by weight can be obtained. Generally, the weight ratio of the polyol compound / sericin in the polyurethane is in the range of 0 to 50, preferably 0 to 30, and more preferably 0 to 10.

[0015]

The polyurethane of the present invention contains microbially degradable sericin as a segment thereof,
It is biodegradable and has excellent mechanical and thermal properties. The polyurethane of the present invention is used in various forms such as films, molded products, fibers, foams, adhesives, and elastomers. Further, the polyurethane of the present invention has an advantage that the manufacturing cost thereof is low because it is manufactured using sericin which is a waste.

[0016]

Next, the present invention will be described in more detail with reference to examples. The parts shown below are parts by weight.

Example 1 Waste raw silk was boiled in boiling water of distilled water for about 3 hours, dehydrated and dried, and then filtered through a 200-mesh filter to make the particle size uniform. Next, this sericin is dissolved in polyethylene glycol (PEG) having a molecular weight of 400, 1 part by weight of this solution is added to 1 part by weight of tetrahydrofuran, and 1.5 parts by weight of diphenylmethane diisocyanate (MDI) and 0.01 part of dibutyltin laurate are added thereto. 25 parts by weight
The reaction was carried out at 0 ° C for 1 hour. The resulting reaction solution was cast on a glass plate and tetrahydrofuran was evaporated to a thickness of 0.5.
mm polyurethane film, and this film was heat-treated at 120 ° C. for 30 minutes to be cured.

The tensile test results of the film thus obtained are shown in Table 1, and the thermal analysis results thereof are shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

Example 2 Sericin was dissolved in polypropylene glycol (PPG) having a molecular weight of 400, and 1 part by weight of this solution was added with 0.01 part by weight of a silicon-based foam stabilizer, 0.01 part by weight of water as a foaming agent, and a catalyst. 0.01 part by weight of dibutyltin laurate as an ingredient, 1.5 parts by weight of MDI are further added, and
The mixture was stirred well with a homogenizer at 0 ° C. and reacted for 5 minutes. Then, it was left at room temperature overnight.

The mechanical properties of the polyurethane foam thus obtained are shown in Table 3, and its thermal properties are shown in Table 4.

[0023]

[Table 3]

[0024]

[Table 4]

The Tensileon RTA-500 manufactured by Orientec Co., Ltd. was used for the tensile test and compression test.
Thermal analysis is a differential scanning calorimeter D manufactured by Seiko Instruments Inc.
The measurement was performed using SC220C and a viscoelasticity measuring device DMS200.

Example 3 Sample No. 1 of Example 1 A test piece (30 × 5 × 0.5 mm) of the polyurethane film of 6 was prepared, and this was left in a constant temperature and humidity chamber at 28 ° C. and a humidity of 80% in soil collected from a forest. Table 1 shows the standing period and the weight reduction rate of the sample at that time. For comparison, the same type of test was performed using polyurethane (Sample No. 1) prepared from polyethylene glycol and MDI under the same conditions. The results are also shown in Table 5.

[0027]

[Table 5]

Claims (4)

[Claims] 1. A biodegradable polyurethane containing a segment consisting of sericin. 2. A method for producing a biodegradable polyurethane, which comprises reacting polyisocyanate with a solution of sericin in an organic solvent. 3. The method of claim 2 wherein said solution contains a polyol compound. 4. The method of claim 2, wherein the organic solvent is a liquid polyol compound.