JPS5982939A - Production of hydrogel - Google Patents

Abstract

PURPOSE:To obtain a gel which is highly elastic and flexibility and does not freeze in the freezing chamber of a refrigerator by cooling and solidifying an aq. soln. contg. PVA and water soluble polyhydric alcohol having specific performance respectively at specific concn. then subjecting the soln. to vacuum dehydration. CONSTITUTION:An aq. soln. which contains PVA of >=98mol% rate of saponification and 800-1,500 average degree of polymn., and a water soluble polyhydric alcohol of 2-6C having 2-6 hydroxyl groups in a molecule, and is adjusted to 8-25wt% and 1-40wt% respectively in the concn. of the PVA and the water soluble polyhydric alcohol is cooled and solidified at <-5 deg.C; thereafter the soln. is subjected to vacuum dehydration at 5wt%-95wt% dehydration rate. The resulting hydrogel is highly elastic and flexible and does not freeze in the freezing chamber of a refrigerator. The gel is insoluble in water or hot water and exhibits no tackiness. The hydrogel is used as a substitute for an ice pillow, ice bag, etc. utilizing such properties.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydrogels, and particularly provides a method for producing cold gels from polyvinyl alcohol with excellent properties not found in conventional hydroegels.

Various cooling gels have already been proposed under the names of cooling gel, cold preservation gel, cold heat transfer medium, colloidal refrigerant, cold preservation device, cold preservation composition, and ice pillow that does not require ice. It is put into practical use. However, as illustrated below, all of them have problems in product properties or manufacturing methods.

(1) As a simple method for producing water-containing (hydro)gel for cold storage,
It is famous for its production of agar gel. That is, 80-94℃
After completely dissolving agar equivalent to 0.1wt% or more, for example 1~]Qwt%, in boiling or boiling water, leave to cool to room temperature to form a hydrous gel (with a water content of about 90~99wt%). hydrogel) can be easily obtained. but,
After cooling this gel in the ice chamber of the refrigerator, use it as a cold storage gel.
For example, when used as an ice pillow or ice bag substitute, agar gel has poor elasticity and is extremely brittle, so it gives the human body a foreign body sensation, and the gel disintegrates during use, making it difficult to feel comfortable. Far from it. In addition, in the case of ice compartment odor in the refrigerator, the freezing temperature can be lowered by soaking agar in an antifreeze solution such as ethylene glycol or propylene glycol, or by cooling a heated aqueous solution containing both embedding and antifreeze solution. However, the gel thus obtained is also brittle and easily disintegrated, making it unsuitable for use in pillows and other cold storage gels.

(2) It has long been well known that when boric acid (or borax solution) or borax (or borax solution) is added to an aqueous polyvinyl alcohol solution, gelation occurs immediately. It is soft and can be easily torn into pieces by simply pinching it with your fingertips.It also has the disadvantage of syneresis (separation of water contained in it) during repeated use (Japanese Patent Publication No. 11210/1983).

Polyvinyl Alcohol Contains Borax Gel in the Refrigerator (Freezer)
By cooling in an ice chamber, the water in the gel freezes, and in order to completely avoid the resulting hardening of the gel, monohydric alcohol, polyhydric alcohol, sucrose, or sucrose is added to the polyvinyl alcohol aqueous solution. A method of gelatinizing with borax after addition has been proposed, but in this case, the strength of the gel is rather reduced, and there is also the problem that syneresis occurs during repeated use (Japanese Patent Publication No. 19602/1973).

Another method for completely lowering the freezing point of polyvinyl alcohol/borax gel is to immerse the gel in an antifreeze solution such as ethylene glycol or propylene glycol; In addition to further weakening and losing its shape,
Antifreeze solutions such as methanol, ethanol, and acetone also have the disadvantage that the gel collapses.

The present inventor has conducted research to develop a method for safely and stably producing a water-insoluble gel with excellent mechanical properties, which does not easily freeze in a refrigerator (freezer) or ice chamber, using an aqueous solution of polyvinyl alcohol. , the knowledge that by completely cooling, solidifying, and vacuum dehydrating (drying) an aqueous solution or suspended aqueous solution containing polyvinyl alcohol and water-soluble polyhydric alcohol, a solid gel that is highly elastic and flexible and is difficult to freeze can be obtained. and a method for producing a cooling gel (Japanese Patent Application No. 56-134311) and a head cooling gel for preventing hair loss due to side effects of anticancer drugs (Japanese Patent Application No. 77502-1983).
) was submitted as.

That is, these include polyvinyl alcohol with a saponification degree of 95 molar coefficient or more and an average degree of polymerization of 1,500 or more, and a water-soluble polyhydric alcohol having 2 to G carbon atoms and having 2 to 6 hydroxyl groups in the molecule, and the concentration of the polyvinyl alcohol and the water-soluble polyhydric alcohol is 2.5 to 2.5, respectively.
An aqueous solution adjusted to IQwt% and 20 to 80wt%,
Cooling gel that is characterized by being cooled and solidified to a temperature lower than -6°C, and then subjected to vacuum dehydration with a dehydration rate (weight reduction rate of the cooled and solidified product) of 5 wt% or more and 95 wt% or less. provided a manufacturing method.

By gelling an aqueous solution or suspended aqueous solution containing polyvinyl alcohol and the water-soluble polyhydric alcohol, a gel that is highly elastic and flexible and does not freeze even in a freezer icebox was obtained.

Furthermore, this gel is completely different from the gel of an aqueous polyvinyl alcohol solution in that it is insoluble in water or hot water and exhibits no stickiness.

That is, a new gel has been provided that is completely different from the knowledge regarding the conventional gelling of an aqueous polyvinyl alcohol solution by cooling, or the gelling of a conventionally known aqueous polyvinyl alcohol solution by chemical treatment.

Because the gel itself has a feel similar to living tissue, it can be used as a highly elastic ice pack, such as an ice pillow or an ice bag substitute. Therefore, in order to prevent hair loss due to the side effects of anticancer drugs, we molded it into the shape of a head cooling helmet and wore it directly on the head (without filling or enclosing it in a vinyl chloride bag, etc.). Can be placed in close contact.

As a result of further research into the performance of this gel, the present inventor found that in the preparation of a mixed aqueous solution of polyvinyl alcohol and water-bathable polyhydric alcohol, the concentration of polyvinyl alcohol was kept at 8 to 25 wt%, and the polyhydric alcohol Adjust the concentration to 1 to 40 wt%, pour it into a container of the desired shape, and then subject it to cooling, solidification, vacuum, and partial dehydration. ，
Hydrogels of the desired shape can be obtained even from polyvinyl alcohols with less than 500% polyvinyl alcohol, and in addition, as in the case of the above-mentioned application, a wider variety of polyvinyl alcohols can be utilized, thereby providing elasticity, flexibility, and stiffness. The present invention was completed based on the discovery that it is possible to provide a variety of different hydrogels. That is, in the present invention, the average polymerization of polyvinyl alcohol is 1tso.

J::, less than 1,500, and the polyvinyl alcohol concentration in the hydrogel production raw stone aqueous solution is 8 to 25 wt%,
It is characterized by having a polyhydric alcohol concentration of ~4Qwt%.

The degree of saponification of polyvinyl alcohol used in the present invention is 98
It contains at least 99 moles φ, preferably at least 99 moles φ.

The average degree of polymerization of polyvinyl alcohol used in the present invention is 8
00s, above, less than 1,500. Average degree of polymerization 300
~500, only a viscous liquid or a soft gel is produced, and in order to overcome this, the polyvinyl alcohol concentration in this case is, for example, 26 wt%, or even 50 wt%.
%, a rigid gel with low moisture content and poor elasticity is produced, which is brittle and easy to break. It is not possible to obtain a rich hydrogel with excellent mechanical strength. Therefore, in the present invention, the average degree of polymerization is 8
Using polyvinyl alcohol of 00 or more and less than 1,500, for example, the average degree of polymerization that is usually commercially available], 4
Polyvinyl alcohol such as 00.1, 100.1,000, etc. can be used as is.

In the present invention, first, an aqueous solution containing polyvinyl alcohol and a water-soluble polyhydric alcohol is prepared. The concentration of polyvinyl alcohol is 8 to 25 wt%, preferably 10
~l 5wt%. As in the present invention,
In order to use polyvinyl alcohol with a relatively low average degree of polymerization, as described above, the polyvinyl alcohol degree is 18.
wt% or more 25wt%, preferably IQwt% or more 20
It is better to increase it to wt%.

In the present invention, prior to forming a gel, a water-soluble polyhydric alcohol as a freezing point depressant is dissolved in the polyvinyl alcohol aqueous solution. This is useful for preventing the hydrogel of the present invention from quickly freezing and becoming hard when it is left in an ice-making compartment of a household refrigerator.

The water-soluble polyhydric alcohol having 2 to 6 hydroxyl groups in the molecule used in the present invention usually has 2 to 6 carbon atoms.
A polyhydric alcohol of about 6 is used. Examples of the freezing point depressant include ethylene glycol. The freezing point of pure ethylene glycol is -16°C, but for example, the freezing point of an aqueous solution with a concentration of IQwt of 19 wt% is
They are -3°C and -8°C, respectively. This freezing point lowering effect is not limited to ethylene glycol, but also 1,2-propylene glycol (furopylene glycol) (10 wt% substitution
-3℃), i,3-propylene glycol (10wt%
substitution, -3°C), glycerin (10 wt% substitution, -1°C)
〉, 2-methyl-2,4-bentanediol (IQwt
It is also found in water-soluble polyhydric alcohols such as 10% substitution, -2°C), which lower the curing temperature of the gel to below 10°C. Furthermore, the freezing points of a 16-19 wt% aqueous solution of glucose and a 10-15 wt% aqueous solution of sucrose are -2°C and -0.5°C to -1°C, respectively. Furthermore, 0.8 to 1.8 wt% aqueous solution of glucose, 0.1 wt% of sucrose
The freezing point of ~1wt% aqueous solution is -Sail]~-0, respectively.
2°C and -0.01°C, and even with these relatively small amounts of polyhydric alcohol, a certain degree of freezing point lowering effect can always be obtained. Depending on the internal storage temperature and storage time),
The amount of polyhydric alcohol used as a freezing point depressant is 1 to 4.
It can be selected as appropriate in the range of 0wt%.

The water-soluble polyhydric alcohol of the present invention includes 1, 2-7, which is already permitted to be added in large quantities to foods in Japan.
'Robylene glycol (propylene glycol), glycerin, D-sorbitol most preferred.

The above-mentioned various water-soluble polyhydric alcohols are
It is embedded in the gel and has some effect on preventing the gel from air drying and hardening. As for the usage amount, the above-mentioned Toshi, Hydro
Depending on the pre-cooling temperature of the gel, an arbitrary value of 40 wt% or less can be selected, taking into consideration the freezing point lowering effect of the water-soluble polyhydric alcohol. However, if the amount of polyhydric alcohol used is small,
That is, if it is less than 1Qwt%, the air-drying prevention effect of the hydrogel of the present invention is also significantly reduced. Alternatively, for example, use it as is (without packaging) for about 1 hour during the administration of the anticancer drug described below, and then store it in a sealed container or polyethylene bag. It is better to apply

In the present invention, in order to prepare an aqueous solution containing polyvinyl alcohol and water-soluble polyhydric alcohol, in addition to adding and dissolving hevolivinyl alcohol in water and water-soluble polyhydric alcohol, it is also possible to prepare the aqueous solution containing polyvinyl alcohol and water-soluble polyhydric alcohol in advance. It is possible to adopt a method such as dissolving the alcohol kffl and then mixing polyhydric alcohol (or its aqueous solution) therein. 1-4
0wt% [Adjust. In these cases, since polyvinyl alcohol is poorly soluble in solvents other than water, it often takes a state in which transparent microgel particles are dispersed in an aqueous solution containing a water-soluble polyhydric alcohol (transparent suspended aqueous solution state). However, if this were the case, there would be no problem in implementing the non-initiation.

In the present invention, an aqueous solution or suspended aqueous solution containing the polyvinyl alcohol and water-soluble polyhydric alcohol is injected into a desired mold. A highly concentrated aqueous solution of polyvinyl alcohol exceeding %
cP (2Q°C), but by warming it to 60°C, its viscosity decreases to 2,0OOcP. Therefore, when handling the high concentration polyvinyl alcohol aqueous solution suitable for the present invention, it is preferable to maintain the aqueous solution at a high temperature below the total room temperature, if necessary. In the present invention, after pouring a mixed aqueous solution of polyvinyl alcohol and polyhydric alcohol into the mold, the solution is cooled, solidified, and molded.

In this case, the aqueous solution (or suspended aqueous solution) is cooled to a temperature below the white/opaque (freezing) temperature.

For example, the freezing (white antifreeze acclimatization) temperature of a 15 wt% aqueous solution of polyvinyl alcohol with an average degree of polymerization of 1,400 is 12
℃, but often leads to supercooling, -4 to -5℃
Even in this case, it does not freeze or harden and remains transparent.
), the normal frozen state (-2.5°C) develops within 30 minutes. A freezing temperature of -1.5°C (-4 to -5°C when supercooled) is also observed for a 10 wt% aqueous solution of polyvinyl alcohol with a degree of polymerization of 1.100.

Due to the coexistence of polyhydric alcohol in these aqueous solutions,
The freezing temperature is further lowered, for example, when the glycerin concentration is 19wt.
%, polyvinyl alcohol (degree of polymerization 1,400) a
The freezing temperature of an aqueous solution of 1i8wt% is -5℃ (at supercooling -
10°C). As described above, the freezing temperature of the aqueous solution in the present invention depends on the degree of polyvinyl alcohol concentration, the concentration, the type of polyhydric alcohol, and the coexisting concentration.
In any case, in the present invention, it is necessary to cool the aqueous solution containing polyvinyl alcohol to a temperature sufficient to freeze it.

In the present invention, after the above-mentioned cooling treatment, the material is vacuum dehydrated without being melted. As the dehydration rate (rate of weight loss of the cooled and solidified gel) increases, the mechanical strength of the gel also improves, but if we consider its normal use as a hydrogel, it is especially important to increase the dehydration rate to create a strong gel. It is not necessary to obtain a dehydration rate of 5 to 95 wt%, preferably io to 3
Qwt%, more preferably 25 to 70wt%, from the viewpoint of flexibility of the gel. The vacuum dehydration referred to here is 1. Dehydration under reduced pressure', and the degree of reduced pressure A is not particularly limited, for example, 2 mmHg or less, preferably 1 m
It can be carried out at mHg or less, and further at 0.1 w% or less. This dehydration step cannot be omitted. That is, c
Unless step n is carried out, the gel of the present invention, which is highly elastic and has excellent mechanical strength, cannot be obtained, and as dehydration progresses, the gel strength increases, and various properties such as non-adhesiveness and water resistance significantly deteriorate. Although improved, this partial dehydration treatment is essential to the present invention. However, in the present invention, there is no need to perform sufficient dehydration (drying) treatment as seen in freeze-drying of injectable liquids or freeze-drying of water-containing foods such as coffee, milk, fruit juice, and noodles, and partial dehydration treatment as described above is not required. Well, the purpose of the present invention has been fully achieved,
As described above, since the gel strength increases as dehydration progresses, the amount of dehydration can be selected depending on the desired gel strength. In any case, this partial dehydration treatment is essential to the present invention and has extremely important significance.
Moreover, a hydrogel with high water content and excellent mechanical strength cannot be obtained.

The gel of the present invention has a feel similar to that of living tissue, so it can be used as a highly elastic ice pack, such as an ice pillow or ice bag substitute, and exhibits a fresh feel and konjac-like elasticity. Ru.

The gel of the present invention can be used as an ice pillow or ice bag substitute as described above, and can also be used as a head cooling gel used to prevent alopecia as a side effect of cancer chemotherapy. This head cooling gel is suitable for use for the purpose of preventing hair loss caused by administering anticancer drugs to cancer patients.
Da, uno--nycin) or daunorbin 7
(Daunorubicin) or Adriamycin (14-hydroking unorubicin) (14-hydr
Oxy daunorubicin, doxorub
Prevention of severe hair loss as a side effect of drugs such as icin)
It can be of great utility in deterrence. Among these, adriamycin is often considered an important anticancer drug because it shows particularly excellent therapeutic effects against a wide range of cancers.
It should be noted that it is also well known that it is extremely toxic. For example, when Adriamycin All 2511 is administered, more than 90% of patients suffer from alopecia, and the loss of hair caused by this causes a great deal of mental pain to the patients, and also due to patients' lack of understanding of modern medicine. This also poses serious problems that can lead to distrust in medical care.

The cause of this hair loss appears to be that antibiotics administered into the body are absorbed into the hair tissue, and with the intention of completely suppressing this absorption rate, the metabolism of living cells is significantly reduced (2
Efforts have been made to cool hair cells to about 5°C. The administered antibiotic reaches the head after a few minutes,
Since it leaves the head within 30 to 40 m1n and is hardly detected in the bloodstream of the head thereafter, a specific method of cooling the head for about 40 minutes after administration has been sought.

In other words, there is the method of wrapping an ice pack around the head, the method of helmets made of sponge impregnated with a large amount of cold water, and in history, for example, the hollow part of a hat molded from a hollow polyvinyl chloride bag.
Attempts have been made to encapsulate jelly, agar, polyvinyl alcohol/borax gel, etc. However, with the ice pack method, water and ice flow down to the bottom of the bag wrapped around the head due to gravity and become unevenly distributed, making it difficult to cool the entire head uniformly.Also, sponge helmets do not retain water. lacking in ability,
There are practical difficulties, such as a large amount of cold water leaking and dripping. In the method of enclosing a high water content gel as a cooling medium into the hollow part of a hollow cap made of a polyvinyl chloride bag, conventionally known high water content hydrogels are all fluid (polyvinyl alcohol, borax gel, calcium chloride gel, etc.). Methyl cellulose gel) or a soft or brittle solid (agar, jelly, carrageenan, alginate gel), which makes it difficult to maintain its shape (helmet shape), and also has a lack of elasticity, making it difficult to adhere to the head. . In order to prevent the cooling medium from deforming and becoming unevenly distributed, perforations were made vertically and horizontally over the entire surface of the hollow bag type helmet (many small sections were created) to prevent the internal filling from moving. An attempt was also proposed to provide a large number of independent vesicles (small inner chambers) and enclose a cooling medium in each (Japanese Patent Application Laid-Open No. 1983-401.07). Because it is missing, it does not cover the entire surface of the head, creating gaps, so it lacks practical value.

As a measure to prevent hair loss as a side effect of Adriamain, a method has been proposed in which a rubber band is tightened all over the scalp and then it is thrown, but if consideration is given to the cruel pain caused to the patient by applying external pressure to the head, , this attempt is also not at all desirable.

The problem with the above-mentioned head cooling system is that it is necessary to use a cooling material with appropriate properties, that is, a high water content gel (hydro gel) that has rubber-like elasticity and mechanical strength IW that can maintain the shape of the helmet. This is due to something that cannot be done manually.

According to the present invention, a head cooling gel can be created by injecting an aqueous solution or suspended aqueous solution containing the polyvinyl alcohol and water-soluble polyhydric alcohol into a mold for molding a helmet, cooling, solidifying, and molding.

In this case, the shape of the helmet should not only cover the entire head hair, but also cover the armpits (i.e. the hair on the left and right sides of the head).
Furthermore, it is nice that it can cover the eyebrows as well, so it is inappropriate to be used as a mere helmet for work sites or a batter's helmet in baseball, or as a mold for molding helmets used for driving motorcycles, playing ice hockey, etc. , a helmet made of the gel of the present invention can be easily manufactured by making desired modifications.

In the present invention, the helmet-like gel thus obtained is immediately wrapped in a reed (that is, without being packaged or sealed in a bag made of polyvinyl chloride, polyethylene, polypropylene, etc.) into a head-cooling helmet I. The feel of the hydrogel of the present invention can be directly transmitted to the head, and since this hydrogel has high elasticity, it can always provide sufficient adhesion to a wide range of head sizes and shapes. sex is achieved. In other words, compared to the case where a bag made of polyvinyl chloride or rubber is applied to a bag made of polyvinyl chloride or rubber, a hydrogel with a konjac-like (or guzumochi-like) feel can be applied to the head. It is clear that the present invention, which directly adheres to the skin, is much more in line with ergonomic treatment principles.

According to the invention, as a raw material for the production of hydrogel.

The average degree of polymerization of the polyvinyl alcohol was 8o.

It is possible to select less than 1,500 and use various commercially available polyvinyl alcohols.

In the present invention, since polyvinyl alcohol with a relatively low degree of polymerization is used, a hydrogel particularly rich in flexibility and elasticity can be obtained, and when used for the purpose of keeping the head of cancer patients cool, it has a particularly soft texture. The polyvinyl alcohol concentration in the present invention is selected to be in the high range (15 to 25 wt%), which is suitable for patients who prefer soft hydrogels, but also when a hydrogel that tightly adheres to the head is desired. By doing so, there is an advantage that the objective can be achieved.

Examples of the present invention will be described below.

Example 1 Saponification degree: 99.5 molar ratio, average degree of polymerization: 1,400.4%
Aqueous solution viscosity (20°C) 230P polyvinyl alcohol 210g (water content 7wt%), glycerin], OO
A suspended aqueous solution consisting of 1,390 g of water (water content: 8 wt%) was subjected to pressurized steam sterilization at 120°C x 35 m1n, and then stirred in a sterile room to uniformly dissolve it, thereby producing 11 wt% of polyvinyl alcohol, A water-soluble tj containing 5 wt% of glycerin was obtained.

1,900 g of this water@liquid was pre-steam-sterilized in a stainless steel mold for molding a helmet (helmet depth: approx. 21 C1yr, outer diameter: approx. 17 Cn+).

Thickness: approx. 2 on)-\ Injected, left to cool at -20°C for 9 hours, and immediately vacuum dehydrated to remove 220 gt of water (dehydration rate: 12
wt%) and then allowed to stand at room temperature to melt.

The helmet thus obtained was highly elastic and flexible, and had sufficient mechanical strength to allow it to be put on and taken off as a helmet. This was stored in a fully refrigerated refrigerator, and when the temperature reached 0°C, it was placed on the head of a child (8 years old) and the child was placed in a supine position. After 8 m1, the scalp temperature reached 20 to 22°C. ,
It was then kept at 20-25°C for 38 min.

Example 2 Polyvinyl alcohol (saponification degree 99°] molar ratio, average polymerization degree 1, viscosity of 1.00.4% aqueous solution (20°C)),
5 cP) powder (water content 7 wt%), 100 g of glycerin, and 1,458 g of water.
Aqueous solution of 20 wt% polyvinyl alcohol and 5 wt% glycerin was obtained by applying pressure steam sterilization at 0 ° C.
Here, butyl para-hydroxybenzoate l Q Q
11I (equivalent to 50 p, I)m) and sulfuric acid furanomine powder (equivalent to 5,000 ppm) were dissolved.

This aqueous solution was added to the Helmets I made of stainless steel.
・Molding mold (helmet depth approx. 23c1n1 outer diameter approx. 2
0 clrt, thickness approx. 2c171) at -35°C.
After leaving to cool at 91x, immediately vacuum dehydrate f: apply, moisture 210
g was completely removed (dehydration rate: 1 Qwt%), and then allowed to stand at room temperature to melt.

The resulting helmet was highly elastic and flexible, and had sufficient mechanical strength to be repeatedly put on and taken off as a helmet.Also, even after being left in a refrigerator ice compartment for one hour, no freezing or hardening was observed. , the original flexibility and elasticity were retained.

This was left at room temperature, and when the temperature reached 0°C, it was placed on the head of an adult and the patient was placed in a horizontal supine position. After 9 minutes,
Scalp temperature reached 21-23℃, then 37 min
During this period, the temperature was maintained at 21-25°C.

Example 3 430 g of polyvinyl alcohol (water content 7 wt%) with a saponification degree of 99.5 molar and an average polymerization degree of 1,000.4 having an aqueous solution viscosity (20°C:) of 11 cP, 175 g of glycerin
A suspended aqueous solution consisting of 0.35 g of n-butyl s-para-hydroxybenzoate, 17.5 g of rested colistin powder, and 2,800 g of water was subjected to pressurized steam sterilization at 120° C. x 25 m:Ln, and then stirred in a sterile room, By uniformly dissolving polyvinyl alcohol 12wt.
%, chrycerin 5wt%, n-butyl hydroxybenzoate 1100pp, colistin sulfate 5,000pp
A ppm aqueous solution was obtained. This aqueous solution 3,400 g-z
, Helmet mold made of Nutenless steel (
Helmet depth approx. 26 cng outer diameter approx. 22 c/rlz
, approximately 2 crrr thick) at -25°C.
After cooling, it was immediately completely dehydrated to remove 325 g of water (
(dehydration rate: 9.5 wt%), and then allowed to stand at room temperature to melt.

The resulting helmet is highly elastic and flexible, and has sufficient mechanical strength to allow it to be put on and taken off as a helmet.
It did not become rigid and retained its original flexibility and elasticity.

This was left at room temperature, and when the temperature reached 0℃, it was placed on the adult's head and the head was placed in a supine position. After 8 m1n, the scalp chamber reached 21 to 23℃, and then for 38 min. 2
The temperature was maintained at 1-25°C.

Example 4 Saponification degree: 99.5 molar, average polymerization degree: 1,100.4 (aqueous solution viscosity (20°C))], 5 cP polyvinyl alcohol 340 g (water content 7 wt%), 500 g of fluoropylene gellicol, and water 1, 1 in a suspended aqueous solution consisting of 170 g
The mixture was subjected to pressure steam sterilization at 20° C. x 30 ml, and then stirred in a sterile room to uniformly dissolve it, thereby obtaining an aqueous solution containing 16 wt% polyvinyl alcohol and 25 wt% propylene glycol.

This aqueous solution 2 Ky'x was injected into a helmet mold, and after being left to cool at -45°C, it was immediately subjected to vacuum dehydration to remove 230 g of water (dehydration rate: l 2 wt%),
Next, it was allowed to stand at room temperature to melt.

The helmet thus obtained was highly elastic and flexible, and had sufficient mechanical strength to allow it to be put on and taken off as a helmet. This was placed in an ice storage cabinet, and when the temperature reached 0°C, it was placed on the head of an adult and the patient was placed in a supine position.
After n, the scalp temperature reached 20-22℃, then 38℃
The temperature was maintained at 20-25°C for min.

Example 5 Polyvinyl alcohol 160 g, water 2,650 g, water 2,650 g, sulfuric acid paromomycin y
(paromo-mycin sulfate)
120'CX25ml1n in a suspension mixed aqueous solution of 16g of powder
The mixture was sterilized with pressure steam, then stirred in a sterile room to dissolve it uniformly to obtain an aqueous solution containing 10 wt % polyvinyl alcohol, 5 wt % glycerin, and 5,000 ppm of acid concentration. Ta. 9 to this aqueous solution 3.1, and a helmet molding mold (helmet depth approx. 25c1z1, outer diameter approx. 22ttn, thickness approx. 2c).
771), left to cool at -40°C for 6 hours, and immediately subjected to vacuum dehydration to remove 200 g of water (dehydration rate: 6-5
wt%) and then left to thaw at room temperature.

The helmet thus obtained was highly elastic and flexible, and had sufficient mechanical strength to allow it to be put on and taken off as a helmet.
No freezing or stiffness was observed, and the original flexibility and elasticity were maintained. This was left at room temperature, and when it reached 0°C, it was placed on the head of an adult and the adult was placed in a semi-prone position. After 9 m1n, the scalp temperature U reached 21-23°C, and then 39°C.
The temperature was maintained at 21-25°C for 20 minutes.

Example 6 Saponification degree 99.5 mol%, average polymerization degree 1,300. 4
Aqueous solution viscosity (20°C) 200g of polyvinyl alcohol of 20 CP was dissolved in 1,260gK of water, 44g of propylene glycol was mixed therewith, and polyvinyl/L/
A mixed aqueous solution containing 7/l/col concentration of 12 wt% and 3 wt% of flopylene glycol was obtained. This was poured into a mold for helmet molding, left to cool for 8 hours at -20°C, and immediately subjected to vacuum dehydration to remove 200 g of moisture (dehydration rate: 1
3 wt%) and then allowed to stand at room temperature to melt.

The helmet thus obtained was highly elastic and flexible, and also had sufficient mechanical strength to allow it to be put on and taken off as a helmet.

This was placed in an ice storage cabinet, and when O'CK was reached, it was placed on the adult's head and the adult was placed in a supine position. After 8 m1n, the scalp temperature reached 20 to 22°C, and after that, the scalp temperature reached 20 to 22°C for 33 min.
The temperature was maintained at 0-25°C. The composition of this helmet was 15 wt% polyvinyl alcohol, 3 wt% propylene glycol, and 82 wt% water.

Comparison Example 1 In Example, 1,900 B of an aqueous solution of polyvinyl alcohol and glycerin was poured into a mold for molding a helmet, and then allowed to cool at -40°C for 24 hours, without performing the partial dehydration operation of the present invention. , leave to thaw at room temperature.

When the molded body is taken out of the mold, it is so soft that it cannot be stood upright on a desk, and the sleeves are extremely sticky, making it extremely uncomfortable to wear when forced to wear it, and making it hard to hold when putting it on and taking it off. It was confirmed that it was easy to fall off and was easily damaged.

That is, the usefulness of the cold shoulder J/vacuum partial dehydration operation of the present invention is obvious.

Claims (1)

[Claims] Saponification degree is 98 molar or more, average polymerization degree is 800 or more, 1.
．． 500-6j4 polyvinyl alcohol, containing a water-soluble polyhydric alcohol having 2 to 6 carbon atoms and having 2 to 6 hydroxyl groups in the molecule, and the concentration of the polyvinyl alcohol and the water-soluble polyhydric alcohol is , 8~25w each
t% and an aqueous solution adjusted to 1 to 40 wt% is cooled and solidified at a temperature lower than -5°C, and then subjected to vacuum dehydration to a dehydration rate of 5 wt% or more and 95 wt% or less. Hydrogel manufacturing method.