JPH0713187B2 - Gelatin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Technical Field of the Invention The present invention relates to a gelatin composition having a gelatin film, which is fragile and weak and has improved defects such as "stickiness" due to moisture absorption.

B. Prior art and its problems Gelatin is well known as a material for binders and microcapsules of photographic emulsions because of its reversible sol-gel transition ability with temperature and excellent protective colloidal property. Widely used for pharmaceutical applications. In addition, researches on gelatin and modification studies have been reported mainly for photographic gelatins in enormous amounts and many results have been reported.

However, since gelatin is an electrolyte, its film is fragile and weak in strength like general polyelectrolytes, and at the same time, it is highly sensitive to humidity, and it has the drawback of producing "stickiness" on the surface under high humidity. , These improvements are strongly desired.

It has also been attempted to fit various water-soluble polymers for the purpose of modifying the strength of gelatin, but in general, the compatibility is poor at the time of mixing, and the strength becomes lower than that of gelatin itself by mixing. In many cases, satisfactory results have not been obtained. In particular, polyvinyl alcohol polymers are polymers that give the strongest film in terms of strength among various water-soluble polymers, but they have poor compatibility with gelatin and cannot achieve their purpose even when mixed. Is the current situation. Therefore, in order to improve the strength of the film by mixing a water-soluble polymer with gelatin, it is a prerequisite that the compatibility of both is good at the time of mixing, but at the present time it is highly soluble in water that is well compatible with gelatin. There are very few molecules.

C. Structure, Purpose, and Effect of the Present Invention As a result of intensive investigations by the present inventors in view of such circumstances, a polyvinyl alcohol-based polymer (hereinafter referred to as PVA-based polymer)
, A water-soluble or water-dispersible block copolymer containing another component, an acrylic polymer having an ionic group or an acrylamide polymer having an ionic group introduced, is well compatible with gelatin and is transparent. The inventors have found that a film having good properties can be provided, and that the disadvantages of the gelatin film, which are brittle and weak, and "stickiness" associated with moisture absorption are improved, and have completed the present invention.

As described above, the gelatin composition of the present invention has poor compatibility with conventional gelatin and cannot be used as a mixture with gelatin.
It is excellent as a film that has good compatibility with the A-type polymer and has good transparency, strength, and no stickiness due to moisture absorption. Of course, the reversible sol-gel transition ability with temperature, which is the most characteristic feature of gelatin, is not impaired by the addition of the block copolymer.

Gelatin is a water-soluble or water-dispersible block copolymer containing the PVA polymer of the present invention as a component and an acrylic polymer having an ionic group or an acrylamide polymer having an ionic group introduced as another component. It is well compatible with PV by the electrostatic interaction between the ionic group which is an amino acid residue in gelatin and the ionic group in the block copolymer.
It is considered that this is because the dispersibility of the A type polymer portion in gelatin is improved.

D. More Detailed Description of the Invention An acrylic polymer having an ionic group or an acrylamide polymer having an ionic group introduced therein, which is a component of the gelatin composition of the present invention and contains a PVA-based polymer as a component. The water-soluble or water-dispersible block copolymer as the other component,
Although it can be produced by various arbitrary methods, as shown in the examples of the present invention, PVA having a mercapto group at the terminal obtained by saponifying a polyvinyl ester polymer having a thiol ester group at the terminal is obtained. Most preferred is a method of producing a radically polymerizable monomer having an ionic group in the presence of a system polymer by radical polymerization.

(Japanese Patent Application No. 58-61746 and Japanese Patent Application No. 58-62673) The detailed method is described below.

First of all, the PVA-based polymer having a mercapto group at the terminal is obtained by polymerizing a vinyl monomer mainly composed of vinyl ester monomers in the presence of thiol acid to saponify the polyvinyl ester-based polymer by a conventional method. can get.

The thiol acid used herein includes an organic thiol acid having a -COSH group. Examples thereof include thiol acetic acid, thiol propionic acid, thiol butyric acid, and thiol valeric acid. Among them, thiol acetic acid is most preferable because of its degradability.

The vinyl ester may be any vinyl ester that can be radically polymerized. Examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate, vinyl laurate, vinyl stearate, and the like. Among them, vinyl acetate is the most polymerizable and preferred.

Polymerization of vinyl monomers mainly composed of vinyl esters such as vinyl acetate in the presence of thiol acid is carried out in the presence of a radical polymerization initiator, a bulk polymerization method, a solution polymerization method, a pearl polymerization method,
Although any method such as an emulsion polymerization method can be used, the solution polymerization method using methanol as a solvent is industrially most advantageous. The amount and method of addition of the thiol acid present in the polymerization to the polymerization system are not particularly limited and should be appropriately determined depending on the physical properties of the intended polyvinyl alcohol polymer. As a polymerization method, a known method such as a batch method, a semi-continuous method or a continuous method can be adopted.

As the radical polymerization initiator, known radical polymerization initiators such as 2,2′-azobisisobutyronitrile, benzoyl peroxide, and carbonate carbonate can be used, but 2,2′-azobisisobutyronitrile and the like can be used. Azo initiators are preferable because they are easy to handle. Radiation, electron beam, etc. can also be used. The polymerization temperature is preferably selected from the range of 30 to 90 ° C, although it is desirable to adopt an appropriate temperature depending on the kind of the initiator used. After polymerization for a predetermined period of time, unpolymerized vinyl esters are removed by a usual method to obtain a polyvinyl ester polymer having a thiolate ester group at the terminal.

The polyvinyl ester-based polymer thus obtained is saponified by a conventional method, but it is usually advantageous to carry out the copolymer as an alcohol solution, especially a methanol solution. As the alcohol, not only an anhydride but also a small amount of a water-containing alcohol may be used according to the purpose, and an organic solvent such as methyl acetate or ethyl acetate may be optionally contained. The saponification temperature is usually selected from the range of 10 to 70 ° C. As the saponification catalyst, alkaline catalysts such as sodium hydroxide, potassium hydroxide, sodium methylate, and potassium methylate are preferable, and the amount of the catalyst used is appropriately determined depending on the degree of saponification, the amount of water, and the like. It is desirable to use a molar ratio of 0.001 or more, preferably 0.002 or more. On the other hand, if the amount of alkali is too large, it becomes difficult to remove the residual alkali from the polymer, and the polymer is colored, which is not preferable, and it is desirable that the molar ratio be 0.2 or less.

This saponification reaction saponifies the terminal thiol ester of the polyvinyl ester polymer having a thiol ester group at the end and the vinyl ester bond in the main chain, so that the polymer end becomes a mercapto group and the main chain becomes vinyl alcohol. The degree of saponification of the vinyl ester unit in the main chain can be changed according to the purpose of use, but is not particularly limited as long as it is 50 mol% or more, preferably 70 mol% or more. The polymer separated after the saponification reaction can be usually obtained as a white powder by purifying by a known method such as washing with methanol, removing residual alkali, impurities such as alkali metal salt of acetic acid, and drying. .

Next, a method of radically polymerizing a monomer having an ionic group in the presence of a PVA polymer having a mercapto group at the terminal will be described. As the polymerization method, generally known methods such as bulk polymerization, solution polymerization, pearl polymerization,
Although emulsion polymerization and the like can be adopted, it is preferable to carry out the polymerization in a solvent capable of dissolving the PVA polymer, for example, a medium mainly containing water or dimethyl sulfoxide. As the polymerization process, any of a batch method, a semi-batch method and a continuous method can be adopted.

Radical polymerization to obtain a block copolymer is carried out by a conventional radical polymerization initiator such as 2,2'-azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, diazopropyl peroxycarbonate, potassium persulfate. It can be achieved by using a compound suitable for the polymerization system from among ammonium persulfate, etc., but in the case of polymerization in an aqueous system, the mercapto group at the PVA end and potassium bromate, potassium superfluate, ammonium persulfate are used. It is also possible to initiate redox with an oxidizing agent such as hydrogen peroxide. Among these, potassium bromate does not generate a radical alone under ordinary polymerization conditions, but only by the redox reaction with the mercapto group at the PVA end. Since it decomposes and generates radicals, it is particularly preferable for the synthesis of the block copolymer of the present invention. It is an agent.

When radical polymerization is carried out in the presence of the PVA-based polymer having a mercapto group at the end of the present invention, it is important and desirable that the polymerization system is acidic. This is because when the mercapto group is basic, the rate of ionic addition to and disappearance from the double bond of the monomer is large, and the polymerization efficiency is significantly reduced.
It is desirable to carry out at pH 4 or less.

The PVA-based polymer as referred to in the present invention refers to a polymer containing 20 mol% or more of vinyl alcohol units, preferably 50 mol% or more, and more preferably 70 mol% or more. Examples of the monomer component include vinyl acetate, vinyl formate, vinyl propionate, vinyl versatate, ethylene, propylene, (meth) acrylic acid and salts thereof, itaconic acid, maleic acid, fumaric acid and salts thereof, 2-acrylamidopropane. It is acceptable to include sulfonic acid and its salt, (meth) acrylamidopropyltrimethylammonium chloride and the like. The degree of polymerization is not particularly limited as long as it is in the range of 10 or more and 3500 or less.

One component of the gelatin composition of the present invention is a water-soluble or water-containing PVA polymer as one component and an acrylic polymer having an ionic group or an acrylamide polymer having an ionic group introduced as another component. Regarding the dispersible block copolymer, other components other than the PVA polymer component are not particularly limited as long as they are an acrylic polymer having an ionic group or an acrylamide polymer having an ionic group introduced, for example, Homopolymers or copolymers of acrylic acid, methacrylic acid, 2-acrylamidopropanesulfonic acid, and their metal salts and ammonium salts such as dimethylaminoethyl (meth) acrylate and (meth) acrylamidopropyltrimethylammonium chloride, or the above Ionic monomers and acrylamide, methacrylamide, N, N-dimethyl ac Ruamido, N- vinylpyrrolidone, (meth) acrylate, (meth) acrylate, a radical etc. (co) by connexion configured copolymer polymerizable nonionic monomers.

Among the above radical (co) polymerizable ionic monomers,
In particular, monomers containing carboxyl groups (including metal salts and ammonium salts) such as acrylic acid and methacrylic acid, or monomers containing sulfonic acid groups (including metal salts and ammonium salts) such as 2-acrylamidopropanesulfonic acid. However, among the nonionic monomers which can be copolymerized with these ionic monomers, especially acrylamide, methacrylamide, N, N-dimethylacrylamide, N-vinylpyrrolidone, etc., are acrylic polymers or ionic groups having ionic groups. It is preferable as a monomer constituting the acrylamide polymer introduced with. The amount of ionic groups in the ionic polymer is 0.5 mol% or more, preferably 1 mol% because it interacts with gelatin molecules.
Or more, more preferably 2 mol% or more.

The weight ratio of the PVA-based polymer formed in the block copolymer to the ionic polymer which is another component is not particularly limited, but 0.2 ≦ (PVA-based polymer) / (ionic polymer) ≦ 50 More preferably, when 0.3 ≦ (PVA polymer) / (ionic polymer) ≦ 40, the compatibility with gelatin is excellent and the gelatin composition aimed at by the present invention can be obtained.

The composition of the gelatin composition of the present invention is not particularly limited except that it contains gelatin and the above block copolymer.
The material such as photographic emulsion and microcapsules is appropriately determined according to the purpose of use, but the weight mixing ratio of gelatin and the block copolymer is especially the former / latter = 10 / 90-9.
9/1 is preferable, and the former / latter = 20/80 to 90/10 is particularly preferable. In addition, the inclusion of polyvinyl alcohol, other water-soluble polymers, and the like, other than the block copolymer component, causes no problem as long as the object of the present invention is achieved without impairing the compatibility.

The present invention will be described in detail below with reference to examples. In addition, "%" and "part" in Examples mean "% by weight" and "part by weight", respectively.

Examples 1 to 8 and Comparative Examples 1 to 8 (b) Preparation of Block Copolymer Polyvinyl alcohol having a mercapto group at the terminal (saponification degree = 98.7 mol%, [HS] = 1.46 × 10 ⁻⁵ eq / g) ) after the distilled water 420 parts was boiled dissolved by adding to 100 parts, was cooled to room temperature, the pH was adjusted to 3.0 with 1N-H ₂ SO _4. Then, 10 parts of acrylic acid monomer was added and dissolved, and after substitution with titanium, the temperature was raised to 70 ° C., and an initiator aqueous solution prepared by dissolving 0.38 part of K ₂ S ₂ O _{8 in} 20 parts of distilled water was added to carry out polymerization. Started. After stirring and polymerizing at 70 ° C for 3 hours, the mixture was cooled to room temperature, and polyvinyl alcohol-
An aqueous solution of polyacrylic acid block copolymer was obtained. Adjust the pH to 5.
The concentration was adjusted to 5 and the concentration was 17.3%. The viscosity at 20 ° C was 4500 cp. This block copolymer will be referred to as block copolymer A.

Block copolymers B to J were prepared in the same manner as described below.
The composition and concentration pH are summarized in Table 1.

(B) Properties of film obtained by casting a gelatin composition A 10% aqueous solution of gelatin (Kanto Kagaku Reagent) and 10% aqueous solution of the water-soluble polymer shown in Table 2 were mixed in equal amounts at 50 ° C.
After sufficiently stirring and mixing at a temperature of not higher than 0 ° C., the mixture was cast onto a polyester film so as to obtain a film having a thickness of 20 μm, and air-dried at room temperature to obtain a film. The obtained film was subjected to the following tests, and the results are summarized in Table 2.

Test 1; Compatibility was judged by observing the presence or absence of phase separation and observing transparency.

The evaluation was made in three levels: ○: completely transparent, △: slightly cloudy, and ×: phase-separated.

Test 2; The films that were evaluated as ◯ or Δ in Test 1 were compared in tear strength. The judgment was evaluated in three grades of O, C, and X. As a control, the results for a film made of gelatin alone are also shown.

○ means strong and supple, △ means slightly weak, and × means weak and fragile.

Test 3: With respect to the film which was judged as ◯ or Δ in Test 1, after the temperature and humidity were adjusted to 20 ° C. and 95% RH, the film surface was rubbed with a finger to compare the “stickiness” of the film surface. The judgment was evaluated in three grades of O, C, and X. As a control, the results for a film made of gelatin alone are also shown.

○ means that there is no stickiness at all, △ means that there is some stickiness, and × means that there is considerable stickiness.

Comparative Example 9 Phosphoric acid-modified PVA (polymerization degree 1750, saponification degree 98.5 mol%) in which 2.0 mol% of 2-acryloyloxyethyl phosphate group was randomly introduced by copolymerization instead of the block copolymer A of Example 1. In the same manner as in Example 1 except that
A film of phosphoric acid-modified PVA and gelatin was prepared, and the compatibility of the obtained film was determined. The results are shown in Table 2.

As is clear from Table 2, the water-soluble polymer mixed with gelatin has a PVA polymer as one component, and an acrylic polymer having an ionic group or an acrylamide polymer having an ionic group introduced as another component. Only when it is a water-soluble or water-dispersible block copolymer, the obtained film has good transparency, strong tear strength, and little "stickiness" due to moisture absorption.

Poly (acrylamide / acrylic acid) of Comparative Example 8 = 95/5
The random copolymer of (1) is well compatible with gelatin to give a transparent film, but both the strength of the film and the "stickiness" due to moisture absorption tend to be the same as those of the film containing gelatin alone. No excellent effect was obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takuji Okaya 1621 Sakai Aoe-cho, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. (56) References JP-A-54-133543 (JP, A)

Claims (1)

[Claims] 1. A water-soluble or water-dispersible block copolymer containing a polyvinyl alcohol polymer as one component and an acrylic polymer having an ionic group or an acrylamide polymer having an ionic group introduced as another component. A gelatin composition comprising a coalesce and gelatin.