JPH0885727A - Decorative plate material from silk and its production - Google Patents

Abstract

PURPOSE: To obtain a plate material for traditional tortoiseshell work usable in place of a hawksbill shell, whose import has been prohibited. CONSTITUTION: This material is a laminate of sheets made from a compsn. contg. silk fibroin and polyvinylpyrrolidone having a mol.wt. of 500,000 or higher and is produced by a process comprising the step of casting and drying an aq. soln. contg. silk fibroin, polyvinylpyrrolidone, and glyceral (1), the step of removing glyceral from the resultant sheet (2), the step of adding an aq. fibroin soln. to the sheet (3), and the step of stacking at least 4 pieces of the sheet and bonding the sheets under stretching with a hot press (4). Step 2 may be conducted after step 3 or 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel plate material which can be used as a tortoise shell substitute material and a method for producing the same. More specifically, the present invention provides a plate-shaped material having physical properties that enables traditional tortoiseshell crafting, thereby providing an alternative material to the turtle shell, which is a kind of sea turtle, that is, the tortoise shell material. .

[0002]

2. Description of the Related Art Traditional tortoiseshell handicraft work is characterized in that the tortoise shell material is bent and worked by utilizing the thermoplasticity peculiar to the tortoise shell when heating the tortoise shell material in a humidified state. Such thermoplasticity in a moisture-containing state is not found in ordinary synthetic resins. The tortoise shell work needs to be easy to bend and hard to bend when humidified and heated, and the molded product needs to have appropriate hardness and transparency as a decorative product.

The tortoise shell can be said to be a kind of protein resin, but as an artificial protein resin, a casein resin composed of milk protein, that is, casein is known. However, even if the physical properties of the casein resin were improved, there were drawbacks such as less thermoplasticity in the humidified state and weak bending strength compared with the physical properties of the tortoise shell, and tortoise shell work was impossible. Therefore, the present inventors have changed from silk fibroin (hereinafter abbreviated as fibroin), which is a silk protein, to a decorative material having a tortoise shell property, high transparency, moderate hardness and bending strength in a humidified state. An attempt has been made to produce a suitable and beautiful laminated plate-like material, and already, "a novel laminated plate-like material and its manufacturing method (application number 4-
187288) ", and" a novel plate-shaped material having a tortoise shell physical property and a method for producing the same (application number 4-35118).
5) ”, we have filed an invention application for a plate-like material that can be replaced with a tortoise shell that has thermoplasticity when it contains water, and a method for producing the same.
The present invention has been made for the purpose of providing a material and a manufacturing method thereof that can further satisfy the physical property requirements as a substitute for the tortoise shell.

[0004]

The physical properties of the material required for the tortoise shell work are beautiful transparency, decorative properties capable of surface polishing, thermoplasticity in a humidified state, and difficulty in breaking. Further, it is more preferable if pattern unevenness can be formed in the molded body. However, in the method of the patent already submitted, when the molecular weight of fibroin is low, it is difficult to form a fibroin sheet, and the plate-shaped material obtained by laminating the fibroin sheet also tends to be brittle.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that 10% or less of polyvinylpyrrolidone is added to and mixed with fibroin, and then an aqueous solution containing glycerin is sufficiently added. After degassing and defoaming, cast and dry to form a sheet. Next, this sheet is washed with water to remove glycerin, then an aqueous solution of fibroin is added and laminated, and hot pressing is carried out to adhere while stretching and drying. By this, it was found that a material having a tortoiseshell physical property having appropriate hardness and transparency can be formed while preventing brittleness, and the present invention has been completed based on this finding.

In the present invention, a transparent plate-like material capable of tortoise-working can be obtained by laminating and adhering sheets comprising the above-mentioned components by hot pressing while stretching. In order to ensure sufficient adhesion, the fibroin aqueous solution is added prior to hot pressing to further improve the adhesive effect. Of the above components, fibroin is the main component and is an essential material for developing thermoplasticity in a wet state. Polyvinylpyrrolidone is necessary to increase the strength of the sheet and prevent brittleness. Glycerin is indispensable for improving the film-forming property during sheet preparation. In order to keep the hardness of the laminate proper, this glycerin needs to be removed when the laminate is completed.
For that purpose, it is most convenient to cast and dry a mixed aqueous solution of two components to form a sheet, and then deglycerinate the sheet by washing with water, and the stretchability of the laminated sheet during hot pressing due to water absorption by this washing with water. And adhesion are also improved. Polyvinylpyrrolidone is a water-soluble polymer, but it is sandwiched between fibroins that have been beta-structured and made water-insoluble, and they do not elute even during washing with water.

This sheet obtained by mixing polyvinylpyrrolidone has high transparency because polyvinylpyrrolidone is compatible with fibroin, and has high strength because of the high molecular weight of polyvinylpyrrolidone. further,
By adding polyvinylpyrrolidone to the plate-shaped material obtained by laminating, a plate-shaped material having the same hardness as the tortoise shell and improved water resistance and brittleness can be obtained. The present invention will be described in detail below, but the mixing ratio, temperature, number of layers, etc. are not limited to this range.

The ratio of polyvinylpyrrolidone to fibroin is preferably 10% or less. If it is more than this, the adhesion between the sheets in the hot press will be reduced. Further, the ratio of glycerin to fibroin is preferably 10 to 100%, and if it is out of this range, the film-forming property of the sheet is deteriorated.
The concentration of the fibroin aqueous solution is preferably 3 to 5%. An aqueous solution containing these three components is cast, and the temperature is 30 to 90 ° C.
Dry to obtain a sheet. This sheet is washed with water, deglycerined, added with a 3 to 5% aqueous fibroin solution, laminated with four or more sheets, and hot-press bonded at 50 to 200 ° C. to obtain a laminated sheet having a thickness of several millimeters. By drying this laminated sheet, a plate-shaped material having a tortoiseshell physical property is obtained.

In order to form the above-mentioned sheet well, an antifoaming agent or a surfactant can be added to the raw material aqueous solution. Further, for the purpose of coloring and imparting other physical properties, ultrafine gold particles, dyes / pigments, fibers, polymers and the like can be added during the sheet production. Also, a plate-shaped material having a tortoiseshell pattern inside can be obtained by drawing a tortoiseshell pattern spot on a sheet by an appropriate method and then stacking the layers.

[0010]

EFFECTS OF THE INVENTION By preparing the novel material of the present invention by the production method of the present invention, it is possible to provide a plate-like material which can be used as a traditional tortoiseshell handicraft in place of the hawk turtle. Since the importation ban on Taimai was determined by the Washington Convention, there is an urgent need to develop a material that can be replaced with a tortoiseshell, and the present invention responds to this.

[0011]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example 1 A 5% aqueous solution of fibroin having a molecular weight of 40,000 or 90,000,
A reagent grade polyvinylpyrrolidone having a molecular weight of 700,000 and glycerin were prepared. An aqueous solution was mixed and adjusted so that polyvinyl pyrrolidone was 5% and glycerin was 35% with respect to fibroin, and then filtered with a 150-mesh filter cloth.
Octyl alcohol as an antifoaming agent was poured onto these filtrates on the liquid surface, and then sufficiently degassed under reduced pressure. This mixed solution was cast on a glass vat and blow-dried at 50 ° C. for 4 hours to obtain a sheet having a thickness of about 100 μm.

After washing this sheet with water to deglycerin, add an aqueous solution of fibroin, stack 10 sheets, degas under reduced pressure to remove bubbles between the sheets, and 100 ° C. for 2 minutes at 90 ° C.
Hot pressing was performed at kg / cm ² to obtain a laminated sheet. Further, this laminated sheet was dried at 90 ° C. for 1 hour to obtain a plate-shaped material. The properties of these samples are shown in Table 1, showing comparative examples without the addition of polyvinylpyrrolidone. In addition, Example 1 and Comparative Example 1 used fibroin having a molecular weight of 40,000, and Example 2 and Comparative Example 2 used fibroin having a molecular weight of 90,000.

[Table 1]

As is clear from this table, a sheet having high strength can be formed only when the aqueous solution of polyvinylpyrrolidone is added to the aqueous solution of fibroin, and the laminated plate also has sufficient hardness, which is a substitute material for the tortoise shell. Meets the requirements of. By the way, the Vickers hardness of the Taimai shell was 20 to 30 (200 gram load). Water absorption (leaving in water at 20 ° C. for 24 hours) was also less in the example, and it seems that it can withstand long-term storage.

Example 2 A laminate was prepared under the same conditions as in Example 1 using an aqueous fibroin solution having a molecular weight of 90,000 and polyvinylpyrrolidone having a molecular weight of 100,000 (comparative example) and 700,000 (example).
The strength of the laminated plate is shown in Table 2.

[Table 2]

As is clear from Table 2, it was found that by using polyvinylpyrrolidone having a high molecular weight, a laminated material having a high bending strength can be obtained.

Example 3 A 5% aqueous solution of fibroin having a molecular weight of 90,000 and glycerin were prepared. Also, polyvinylpyrrolidone having a molecular weight of 700,000, polyvinyl alcohol having a molecular weight of 500,000, and a molecular weight of 30
Thousands of polyethyleneimine and vinyl acetate emulsions were prepared. 10 of each for fibroin
%, And the aqueous solution was mixed and adjusted so that glycerin became 35%, and then filtered through a 150-mesh filter cloth.
This mixed solution was cast on a glass vat and blow-dried at 50 ° C. for 4 hours to obtain a sheet having a thickness of about 100 μm.

Among these sheets, with polyvinyl alcohol and vinyl acetate emulsion, a transparent sheet was not obtained, but only a cloudy one was obtained. With polyethyleneimine, needle-like crystals were sometimes formed in the sheet. Only in the case of polyvinylpyrrolidone, transparent sheets were always obtained. From this, it was found that polyvinylpyrrolidone is most suitable for producing a transparent laminated plate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication C08L 39:06) (72) Inventor Masafumi Nishiyama 2-3-3 Hananomiyacho, Takamatsu City, Kagawa Prefecture Shikoku Institute of Industrial Technology (72) Inventor Takashi Endo 2-3-3 Hananomiya-cho, Takamatsu-shi, Kagawa Inside Shikoku Institute of Industrial Technology (72) Inventor Fumaki Koga 2 Nakamachi, Nagasaki-shi, Nagasaki No. 23 Japan Bekko Association

Claims (2)

[Claims] 1. A plate-like material having a tortoiseshell physical property, which is obtained by laminating sheets having a composition containing silk fibroin and polyvinylpyrrolidone having a molecular weight of 500,000 or more. 2. A fibroin aqueous solution is added to a sheet obtained by casting and drying a mixed aqueous solution of silk fibroin, polyvinylpyrrolidone, and glycerin, and four or more sheets are laminated and hot-press stretch-bonded, and at any stage. The method for producing a plate-shaped raw material according to claim 1, further comprising the step of removing glycerin with.