JP2002188011A - Molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding material consisting of a molding composition having improved productivity and usability. SOLUTION: The molding material contains gelatin powder containing a water-soluble plasticizer and produced by drying an aqueous solution containing dissolved gelatin and the water-soluble plasticizer and powder of a precondensate of urea resin produced by drying a liquid obtained by the reaction of urea with formaldehyde.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding material for a molded article composition having, for example, biodegradability and having a moisture absorbing or water absorbing ability.

[0002]

2. Description of the Related Art Generally, gelatin is used in animal connective tissue,
Known as a natural polymer obtained by thermally hydrolyzing hard protein collagen widely distributed in skin, tendon, fascia, bone, etc., it is easily soluble in water, gel-forming, hygroscopic, water-absorbing, swelling,
It has various properties such as adhesiveness. Such gelatin has a high purity because it can be obtained by directly purifying various raw materials, and is widely used as a gelling agent, a foaming agent, a binder, a capsule, a thickener and the like in the fields of food, cosmetics, and pharmaceuticals. It's being used.

[0003] On the other hand, leather waste produced as a by-product in the leather manufacturing process is difficult to purify, and the industrial gelatin (also referred to as glue) obtained therefrom contains impurities such as tanning agents. It is used as a material for match, gum tape, abrasive paper, fiber sizing material and the like. However, in recent years, there has been a surplus of industrial gelatin from by-products of leather production due to substitution by synthetic polymers for some uses and reduction in consumption of these products themselves, and development of new uses is required.

Therefore, as shown in the schematic process diagram of FIG. 3, the inventors of the present invention have proposed either an aqueous solution of gelatin, a reaction solution of a precondensate of urea resin, or a mixture of an aqueous solution of gelatin and a reaction solution of precondensate of urea resin. A molding material for a water-absorbing composition obtained by adding a water-soluble plasticizer to each of a crab or a gelatin aqueous solution and a urea resin precondensate reaction solution, and then drying the mixture, and a method for producing the same. It was proposed (Japanese Patent Application No. 2000-15249). In such a proposed technique, the gelatin in the dried product is given fluidity to enable molding of a water-absorbing composition, has water resistance, and has a deliberately controlled biodegradability and water absorption. It is contemplated that a composition is obtained.

[0005]

However, in the above-mentioned proposed technique, in order to uniformly mix the aqueous gelatin solution and the urea resin precondensate, it is necessary to dilute the gelatin concentration of the aqueous gelatin solution to lower the viscosity. The fact that it is necessary to keep the temperature in order to prevent gelatinization of the gelatin aqueous solution, and to remove unreacted formaldehyde that causes a crosslinking reaction with gelatin in the solution, the reaction solution of the urea resin precondensate must be used. It was necessary to repeat the concentration and redilution many times, and it was found that the process, time, and energy consumption were wasteful. In addition, various properties of the water-absorbing composition obtained by this proposed technique are determined at the stage of the aqueous solution or the reaction solution of both the gelatin and the urea resin precondensate, so that the range of use may be limited. understood.

[0006] Therefore, in order to spread the water-absorbing composition using gelatin widely, means for solving these problems must be devised. As described above, an object of the present invention is to provide a molding material that can be obtained more easily and that is more convenient.

[0007]

The present inventor has conducted various tests to solve the above-mentioned problems, and as a result, obtained by incorporating a water-soluble plasticizer into a network between gelatin molecules and then drying. A mixed powder of the water-soluble plasticizer-containing gelatin powder and the urea resin precondensate powder is heated under pressure during molding, thereby partially cross-linking the gelatin and the urea resin precondensate to form a composite. As a result, the present inventors have found that the above object can be achieved, thereby completing the present invention. That is, the molding material according to the present invention is a water-soluble plasticizer-containing gelatin powder obtained by drying an aqueous solution in which gelatin and a water-soluble plasticizer are dissolved, and a urea obtained by drying a reaction solution of urea and formaldehyde. And a resin precondensate powder.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic process for producing a molding material according to the present invention. First, a gelatin powder containing a water-soluble plasticizer according to the present invention is prepared as follows. That is, water in which a water-soluble plasticizer is dissolved is added to gelatin,
After swelling at 10 to 30 ° C, the mixture is heated to 50 to 60 ° C and dissolved to form an aqueous solution. The aqueous solution is dried to form a powder. By making the water-soluble plasticizer into a powder in a state of being incorporated in the network structure between gelatin molecules,
A molding material having a flowability at the time of molding is obtained in spite of being rich in gelatin.

In the present invention, the gelatin concentration in the aqueous solution is not particularly limited, but is preferably, for example, 30 to 70% by weight. If the gelatin concentration is more than 70% by weight, it takes a long time to dissolve and the lump of the raw material powder (commonly known as lumps) tends to remain in the aqueous solution. On the other hand, if the gelatin concentration is less than 30% by weight, a large amount of time and cost is required for the drying treatment, which is not preferable.

[0010] The water-soluble plasticizer used in the present invention is not particularly limited, but those having a boiling point of 150 ° C or more are preferably used. Such materials include, for example, glycerin, ethylene glycol, propylene glycol and the like. By the way, if it is a water-soluble plasticizer having a boiling point of 130 ° C. or less, it will boil at the time of molding, and the molded product will be whitened to a cloudy glass. The amount of the water-soluble plasticizer to be added is not particularly limited, but may be any amount as long as the molding material has fluidity that allows molding. For example, the amount of the water-soluble plasticizer added is gelatin 10
It can be 10 to 40 parts by weight with respect to 0 parts by weight. If the amount of the water-soluble plasticizer exceeds 40 parts by weight, the finally obtained molded article may be too soft or the water-soluble plasticizer may seep out from the surface of the molded article. 10 water-soluble plasticizers
When the amount is less than the weight part, the molding material does not flow even if the molding material is pressurized and heated at the time of molding, so that there is a possibility that a molded body having desired properties may not be obtained.

On the other hand, the reaction for obtaining the urea resin precondensate (urea-formaldehyde precondensate) according to the present invention may be a conventional method. That is, when urea and formaldehyde are subjected to an addition reaction at 30 to 100 ° C. in an alkaline range of pH 7 to 12, a reaction solution in which a urea resin precondensate is dissolved is obtained. In the present invention, the addition ratio of urea and formaldehyde may be 1 to 1.7 mol of formaldehyde per 1 mol of urea, as is commonly used. If the addition ratio of formaldehyde to urea is more than 1.7 mol, the crosslink density of gelatin by the methylol group becomes too high, and the molded article becomes brittle. Conversely, if the addition ratio of formaldehyde is less than 1 mol, crosslinking between the molecules of urea and formaldehyde is difficult, and the mechanical strength of the molded body is reduced.

When the reaction solution in which the urea resin precondensate is dissolved is concentrated and dried, a powder of the urea resin precondensate is obtained. The urea resin precondensate is water-soluble,
It is in an uncured state irrespective of whether it is dissolved or powdery in the reaction solution.

The urea resin precondensate undergoes a slight crosslinking reaction only by heating during molding, but the reaction rate is extremely slow. Therefore, a curing agent, which is an accelerator for the crosslinking reaction, is usually added. Such a curing agent may be used before drying the reaction solution containing the uncured urea resin precondensate, before mixing with the gelatin powder, or before molding the molding material of the present invention (each shown in the process diagram of FIG. 1). It may be added at any stage, or may be added in small portions at the plurality of stages. However, no matter what stage the curing agent is added, the uncured urea resin initial condensate remains until it is heated to a certain level or more.

As described above, the gelatin aqueous solution containing the water-soluble plasticizer or the reaction solution containing the uncured urea resin precondensate may be dried by using gelatin itself or the uncured urea resin precondensate. Any condition may be used as long as the material itself is not denatured, and for example, hot air drying (about 40 ° C.), freeze drying, vacuum drying, spray drying and the like can be applied. Any powder obtained by drying has a particle size according to the purpose of use of the molded article. Incidentally, the smaller the particle size of each powder is, the more a molded product having a smooth surface is obtained, and the larger the size is, the more a molded product having a rough surface is obtained. When a lump of dry solid is obtained by the above drying, it may be pulverized by a suitable pulverizer and sieved to obtain a powder having a desired particle size.

Generally, urea and formaldehyde are converted into a water-soluble urea resin precondensate (NH ₂ CONHCH ₂ OH) by the addition reaction of the following formula (1). When this urea resin initial condensate is heated during molding or the like, a water-insoluble cured product is obtained by the condensation reaction of the formula (2). NH ₂ CONH ₂ + HCHO → NH ₂ CONHCH ₂ OH (1) NH ₂ CONHCH ₂ OH + NH ₂ CONH ₂ → NH ₂ CONHCH ₂ NHCONH ₂ + H ₂ O (2)

On the other hand, in gelatin, a side chain amino group is converted into methylol by formaldehyde as shown in the following formula (3), and another amino group is crosslinked by a condensation reaction as shown in the following formula (4). Are known. In a molding material containing gelatin and a urea resin precondensate, the methylol group in the urea resin precondensate not only reacts with the above-mentioned reaction (2) but also reacts with the side chain amino group of gelatin according to the formula (5). It is recalled that such a cross-linking reaction occurs. As a result, the gelatin is imparted with water resistance, and the compounding of the molding material is completed, whereby the desired molded article is obtained. gelatin-NH ₂ + HCHO → gelatin-NHCH ₂ OH (3) gelatin-NHCH ₂ OH + NH ₂ -gelatin → gelatin-NHCH ₂ NH-gelatin + H ₂ O (4) NH ₂ CONHCH ₂ OH + NH ₂ -gelatin → NH ₂ CONHCH ₂ NH-gelatin + H ₂ O (5) In the formulas (3) to (5), “gelatin-” and “-gelatin”
Indicates a basic skeleton of a gelatin molecule or a gelatin derivative. In this case, by changing the mixing ratio of the gelatin and the urea resin precondensate, the biodegradability and water absorption of the finally obtained molded product are adjusted. The term “water absorption” used herein includes not only a water-absorbing property of absorbing and retaining liquid water, but also a moisture-absorbing property of absorbing and adsorbing gaseous water vapor.

Subsequently, in the process diagram of FIG. 1, when the gelatin powder obtained as described above and the powder of the urea resin precondensate are mixed, the powdery molding material according to the present invention is obtained. Here, the compounding ratio of the urea resin precondensate powder to 100 parts by weight of gelatin powder is preferably 200 to 10 parts by weight, more preferably 160 to 20 parts by weight. If the mixing ratio of the powder of the urea resin precondensate is less than 10 parts by weight, the water resistance of the molded body is deteriorated, while if it exceeds 200 parts by weight, both the biodegradability and the water absorption of the molded body are deteriorated.

The above-mentioned powdery molding material is pressurized and heated by a molding method such as compression molding, transfer molding or injection molding, whereby the methylol group of the urea resin precondensate and the side chain amino group of gelatin react. (See formula (5)) to form a water-insoluble cured product. The pressure and heating conditions during molding are different depending on the molding method and are not particularly limited. However, in the present invention, in order to suppress thermal denaturation of gelatin, a temperature of 130 to 160 ° C. and a pressure of 10 to 20 Mp.
a is desirable. In such molding, a compounding agent such as a release agent, a coloring agent, a filler, a reinforcing agent, a lubricant, and the like can be added to a mixture of the gelatin powder and the powder of the urea resin precondensate, if necessary.

[0019]

The present invention will be described below in more detail with reference to examples. Gelatin powder used in each example was prepared by the following method. That is, 20 g of glycerin (20 parts by weight with respect to 100 parts by weight of gelatin) was added to 100 g of water, and the mixture was added at 20 ° C.
Then, 100 g of gelatin is immersed in the liquid prepared as described above and left for 30 minutes to swell. Then, raise the temperature to 60 ° C to 40
Dissolve the gelatin to make an aqueous solution by keeping for a minute. This aqueous solution was dried in a vacuum drier at about 25 ° C. and a degree of vacuum of about 95%, and the obtained dried product was pulverized by a rotary blade pulverizer and classified by a sieve to a particle size of 300 μm or less. Thus, a gelatin powder containing glycerin in a network structure between gelatin molecules was obtained.

The powder of the urea resin precondensate used in each example was prepared by the following method. That is, urea 60 g, 37%
122 g of an aqueous formaldehyde solution (molar ratio of urea: formaldehyde = 1: 1.5) was charged, the reaction system was adjusted to pH 7.5 to 8.5 with 28% aqueous ammonia, and reacted at 50 ° C. for 1 hour to initiate the urea resin initial stage. A reaction solution containing a condensate was obtained. The reaction solution was concentrated under reduced pressure until it became a slightly white paste. Incidentally, if the reaction solution is concentrated too much, it is not preferable because it is solidified. 0.3 g (0.5 parts by weight per 100 parts by weight of urea) of ammonium imidodisulfonate was added as a curing agent to the reaction solution. Further, after this liquid was dried in a vacuum dryer at about 25 ° C. and a degree of vacuum of about 95%, the obtained dried product was pulverized by a rotary blade pulverizer and classified by a sieve to obtain a particle size. A powder of a urea resin precondensate (uncured product) having a size of 300 μm or less was obtained.

Example 1 120 g of the gelatin powder prepared above and 20 g of the urea resin precondensate powder were mixed to obtain a molding material.

Example 2 120 g of the gelatin powder prepared above and 50 g of a powder of the urea resin precondensate were mixed to prepare a molding material.

Example 3 120 g of the gelatin powder prepared above and 100 g of the urea resin precondensate powder were mixed to prepare a molding material.

Example 4 120 g of the gelatin powder prepared above and 160 g of the powder of the urea resin precondensate were mixed to obtain a molding material.

"Comparative Example" 100 g of a gelatin powder containing no glycerin, 50 g of a powder of a urea resin precondensate,
And 20 g of glycerin was mixed to obtain a molding material.

Therefore, the molding materials of Examples 1 to 4 described above were placed on a flat mold, and the temperature was 140 ° C. and the pressure was 1
40m diameter by pressing at 5MPa for 10 minutes
A disk-shaped molded product (cured product) having a thickness of about 2 mm and a thickness of about 2 mm was obtained as a test piece, and was evaluated for moisture absorption, water absorption, and biodegradability.

"Humidity absorption" means a temperature of 35 ° C. and a relative humidity of 85.
%, The weight of water contained in each test piece when each of the test pieces of Examples 1 to 4 was allowed to stand for 96 hours was expressed as a percentage of the weight of the dry test piece. And
"Water absorbency" was measured by weighing the water content of each test piece when the test pieces of Examples 1 to 4 were immersed in water at a temperature of 25 ° C for 96 hours, and weighing the percentage of the weight of the dry test piece. It was expressed by. These results are shown in Table 1 below and the graph of FIG.

[0028]

[Table 1]

From the test results of Examples 1 to 4, it can be seen that by changing the compounding ratio of the urea resin precondensate powder to the gelatin powder, the moisture absorption and water absorption according to the intended use can be adjusted.

On the other hand, in the comparative example, the glycerin added during the preparation of the molding material did not penetrate into the powder while remaining on the surface of the molding material, so that molding was not possible, and the mold surface was contaminated with glycerin. It was sticky.

On the other hand, “biodegradable” means that the “
The test pieces of Examples 1 to 4 were buried in cm, and the state change of each test piece was observed after 3 months. As a result, the test piece of Example 1 was completely decomposed and disappeared, and the test piece of Example 2 was discolored to brown, decomposed into small pieces, and had a thickness of 1/4 or less. The test piece of Example 3 turned brown (partially purple), decomposed into small pieces, and had a thickness of 以下 or less. The test piece of Example 4 retained its original shape, but pigmentation due to propagation of microorganisms was observed.

[0032]

As described above in detail, the molding material according to the present invention is a powder containing a gelatin powder containing a water-soluble plasticizer in a network structure between gelatin molecules and a powder of a urea resin precondensate. Since it is a body, it is easy to handle. Further, since the physical properties of a molded article obtained from this molding material are determined by the mixing ratio of the gelatin powder and the powder of the urea resin precondensate, various properties of the molded article can be easily adjusted. Gelatin is handled as a powder and does not require heat retention to prevent gelation. Although unreacted formaldehyde remains in the powder of the urea resin precondensate, the cross-linking reaction between gelatin and the urea resin precondensate hardly occurs because the powders are mixed. Therefore, it is not necessary to repeat the concentration and re-dilution of the urea resin precondensate reaction liquid as in the prior art. Furthermore, since it is not necessary to mix the urea resin precondensate with a dilute aqueous gelatin solution as in the prior art, the addition ratio of gelatin to the urea resin precondensate can be increased,
Gelatin-rich molded articles can be obtained industrially.
Of course, the molded article obtained from the molding material of the present invention has not less than a certain level of water resistance that does not hinder use, has biodegradability, and has a simpler method for absorbing water. Changes can be adjusted. By utilizing such properties, moisture absorbent, water absorbent, agricultural and horticultural water retention material, sealing material,
It can be greatly expected to be used for curing materials.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a molding material manufacturing method according to the present invention.

FIG. 2 is a graph showing moisture absorption and water absorption of a water-absorbing composition test piece molded from a molding material according to each example of the present invention.

FIG. 3 is a process chart for explaining a method of manufacturing a molding material according to a conventional technique.

Claims (1)

[Claims] 1. A water-soluble plasticizer-containing gelatin powder obtained by drying an aqueous solution in which gelatin and a water-soluble plasticizer are dissolved, and a urea resin precondensate obtained by drying a reaction solution of urea and formaldehyde. And a powder.