JP4279152B2 - Vinyl acetal polymer, production method thereof and use thereof - Google Patents

Description

  The present invention relates to a vinyl acetal polymer obtained by acetalizing a vinyl alcohol polymer obtained by saponifying a vinyl acetal polymer, particularly a vinyl ester polymer containing a monomer unit having a specific silyl group. The present invention relates to a polymer and a method for producing the same. The present invention also relates to the use of such a vinyl acetal polymer, specifically, an interlayer film for laminated glass, a binder for ceramic molding, a binder for ink or paint, and a heat-developable photosensitive material.

  It has long been known that a vinyl acetal polymer is obtained by acetalizing a vinyl alcohol polymer under acidic conditions using an aldehyde compound. Since the vinyl alcohol polymer usually has a vinyl alcohol unit and a vinyl ester unit, the vinyl acetal polymer obtained by acetalizing the vinyl alcohol polymer is the two types of monomer units. And at least three types of monomer units containing vinyl acetal units. In recent years, since various vinyl alcohol polymers have been proposed, various types of vinyl acetal polymers have become known by combining these with various aldehydes. .

  Among them, a vinyl formal polymer produced from a vinyl alcohol polymer and formaldehyde, a vinyl acetal polymer produced from a vinyl alcohol polymer and acetaldehyde, and a vinyl alcohol polymer and butyraldehyde are produced. Vinyl butyral polymers occupy a commercially important position. In particular, the vinyl butyral polymer is not only used as an interlayer film for laminated glass used for window glass of automobiles and buildings, but also various types of binders such as ceramic molding binders, photosensitive materials, and ink dispersants. Widely used in the industrial field. The vinyl butyral polymer has a hydrophilic hydroxy group and a hydrophobic butyl acetal group, and thus has both hydrophilicity and hydrophobicity, and exhibits its features in the various applications described above. In vinyl butyral polymers, the presence of hydroxy groups in the molecule plays an important role, for example, in terms of adhesion to glass and binder strength with ceramics, but it still interacts with inorganic substances. May be insufficient, and improvements are desired.

  The vinyl butyral polymer is widely used as an interlayer film for laminated glass used for window glass of automobiles and buildings. However, in recent years, the demand for improving the performance of laminated glass has been increasing. For example, when the laminated glass is exposed to a high humidity condition for a long time, there is a problem that water enters from the end of the laminated glass or whitens due to a compatibility defect with the plasticizer. In order to solve this problem, for example, a method using a special silicone oil (Patent Document 1), a method using triethylene glycol-di-2-ethylhexanoate or the like as a plasticizer (Patent Document 2), etc. Various proposals have been made. However, it is difficult to say that conventional vinyl butyral polymers sufficiently satisfy the above whitening resistance, penetration resistance of laminated glass and adhesion to glass at the same time.

  As an interlayer film for laminated glass, it has been proposed to use a vinyl acetal polymer modified with a silyl group obtained by saponification and acetalization of a copolymer of vinyl acetate and vinyltrialkoxysilane (Patent Literature). 3). However, the current situation is that the above problems cannot be sufficiently solved.

  Vinyl acetal polymer is used as a binder for molding in the process of manufacturing ceramic multilayer capacitors and ceramic electronic circuit boards in the field of ceramic molding binders. As widely used. In particular, in recent years, it has been desired to reduce the size and weight of precision electric devices such as mobile phones and notebook computers, and the electric and electronic components used in these devices are also required to be reduced in size and performance. ing.

  For example, in ceramic multilayer capacitors, small and large-capacity capacitors are desired, and attempts have been made to increase the capacity by reducing the thickness of the electrode part or ceramic part. It is important to reduce the thickness of the ceramic green sheet. Technical issues. In order to make such a thin film, it is necessary to use a ceramic powder having a small particle size as a raw material. However, if the particle size of the ceramic powder is reduced, the surface area of the ceramic powder increases and is likely to aggregate. Therefore, irregularities are generated on the surface of the ceramic green sheet, making it difficult to obtain a homogeneous ceramic green sheet. Moreover, the problem that the intensity | strength falls by thinning a sheet | seat also arises. These problems have been highlighted especially by recent miniaturization and weight reduction of electrical and electronic parts, and at the current technical level, the problems pointed out above have not been improved sufficiently. is there.

  Vinyl acetal polymers are used in the paint field, such as automotive paints, baking enamels, shop primers, wash primers, adhesive lacquers, insulating coatings on tar or nicotine, paints for plastics, nitrocellulose lacquers, paper varnishes, etc. It is used for. Further, a vinyl butyral polymer having a low solution viscosity is used as a binder for printing ink used for printing on a packaging material. This printing ink is suitable for printing on a polyolefin film, a metal foil, a cellulose acetate film, a polyamide film and a polystyrene film because of its excellent adhesion to organic and inorganic substrates.

  In recent years, in particular, printing presses are often operated at high speeds. Therefore, in order to realize high-speed operation of printing presses, printing ink has a large pigment content at a desired viscosity and is formed by printing. Even when the thickness of the coating film is small, it is said that the color strength needs to be large. Generally, in order to increase the pigment content in a printing ink, it is important to lower its solution viscosity. In order to reduce the solution viscosity of printing ink, it is conceivable to use a vinyl acetal polymer having a low polymerization degree, but a low polymerization degree vinyl produced by acetalizing a completely saponified vinyl alcohol polymer. When an acetal polymer is used, there are problems such that the aqueous solution of the vinyl acetal polymer is easily gelled and the pigment content cannot be increased.

  In order to solve these problems, for example, a method using a vinyl butyral polymer produced from a vinyl alcohol polymer having a specific degree of hydrolysis (Patent Document 4), a 1-alkylvinyl alcohol unit and 1 A method using a vinyl acetal polymer using a vinyl alcohol polymer having an alkyl vinyl acetate unit as a raw material (Patent Document 5) has been proposed. However, although a certain degree of improvement effect can be seen for these problems by these methods, a sufficient effect is not necessarily obtained.

  In addition, the heat-developable photosensitive material is particularly simple because the processing steps for development are simple and no extra chemical waste liquid is generated, as compared with conventional wet-type photosensitive materials using silver halide. It has been put to practical use in applications such as X-ray photography in the medical field. The photothermographic material is made of a silver halide that is in catalytic contact with an organic silver salt, a reducing agent, and an organic silver ion, using a film-forming binder such as a vinyl acetal polymer, a plastic film, etc. It is obtained by coating on a support.

  Conventionally, these heat-developable photosensitive materials have the storage stability of the coating solution used for the production of the heat-developable photosensitive material, the sensitivity when developing the heat-developable photosensitive material, and the storage stability of the image after development. There was a problem. So far, a method using a vinyl acetal polymer containing a specific ionic group (Patent Document 6), a method using a combination of two types of vinyl acetal polymers having specific polymerization degrees (Patent Document 7), etc. Has been proposed. However, it is difficult to say that the above problems have been sufficiently solved by these methods.

JP-A-7-314609 International Publication No. 00/018698 Pamphlet JP 58-125645 A Japanese Patent Laid-Open No. 11-349889 Special Table 2000-503341 JP 2001-2222089 A JP 2002-201215 A

  The present invention has been made to solve the above-described problems, and provides a vinyl acetal polymer having improved adhesiveness to an inorganic substance while maintaining the original characteristics of a conventional vinyl acetal polymer. It is for the purpose. In addition, using such a vinyl acetal polymer, an interlayer film for laminated glass excellent in whitening resistance, penetration resistance, and adhesion to glass and a laminated glass using the interlayer film for laminated glass are provided. Providing a ceramic molding binder in which the resulting green sheet is homogeneous and excellent in strength, providing a binder for ink or paint capable of lowering the viscosity and increasing the concentration, and a coating used for the production thereof It is also intended to provide a heat-developable photosensitive material that has excellent storage stability, sensitivity when developing a heat-developable photosensitive material, and storage stability of an image after development. is there.

（Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数である。）
で示されるシリル基を有する単量体単位を含有するビニルエステル系重合体をけん化することによって得られるビニルアルコール系重合体をアセタール化して得られるアセタール化度４５〜８０モル％のビニルアセタール系重合体であって、前記ビニルアルコール系重合体が、下記式（Ｉ）を満足し、かつビニルアルコール系重合体の中でその重合度が重量平均重合度の３倍を超える重合体の重量分率が２５重量％以下であることを特徴とするビニルアセタール系重合体を提供することによって解決される。
２０＜Ｐｗ×Ｓ＜４６０ ・・・（Ｉ）
Ｐｗ：ビニルアルコール系重合体の重量平均重合度
Ｓ：一般式（１）で示されるシリル基を有する単量体単位の含有量（モル％） The above problem is solved by the following general formula (1)

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl acetal polymer having a degree of acetalization of 45 to 80 mol% obtained by acetalizing a vinyl alcohol polymer obtained by saponifying a vinyl ester polymer containing a monomer unit having a silyl group represented by A weight fraction of a polymer that satisfies the following formula (I) and whose degree of polymerization exceeds three times the weight average degree of polymerization in the vinyl alcohol polymer: This is solved by providing a vinyl acetal polymer characterized in that is 25 wt% or less.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%)

At this time, in the vinyl alcohol polymer, it is preferable that the weight fraction of the polymer having a degree of polymerization smaller than ½ times the weight average degree of polymerization is 12% by weight or less. It is also preferable that the vinyl alcohol polymer satisfies the following formula (II) and the pH of a 4% aqueous solution thereof is 4-8.
0.1 / 100 ≦ (A−B) / (B) ≦ 50/100 (II)
A: Content of silicon atom in vinyl alcohol polymer (unit: ppm)
B: Content of silicon atom in vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed with Soxhlet extraction with methanol (unit: ppm)
Here, A and B are measured by ICP emission spectrometry after ashing the measurement sample.

  It is also preferable that the aldehyde used for the acetalization is at least one selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde and benzaldehyde, in particular butyraldehyde.

  An interlayer film for laminated glass made of the vinyl acetal polymer and a laminated glass having the interlayer film for laminated glass are preferred embodiments. A ceramic molding binder, ink or paint binder comprising the vinyl acetal polymer is also a preferred embodiment. Furthermore, a photothermographic material containing the vinyl acetal polymer is also a preferred embodiment.

（Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数である。）
で示されるシリル基を有する単量体単位を含有するビニルエステル系重合体をけん化することによってビニルアルコール系重合体を得てから、該ビニルアルコール系重合体をアセタール化する、アセタール化度４５〜８０モル％のビニルアセタール系重合体の製造方法であって、前記ビニルアルコール系重合体が、下記式（Ｉ）を満足し、かつビニルアルコール系重合体の中でその重合度が重量平均重合度の３倍を超える重合体の重量分率が２５重量％以下であることを特徴とするビニルアセタール系重合体の製造方法を提供することによっても達成される。
２０＜Ｐｗ×Ｓ＜４６０ ・・・（Ｉ）
Ｐｗ：ビニルアルコール系重合体の重量平均重合度
Ｓ：一般式（１）で示されるシリル基を有する単量体単位の含有量（モル％） Moreover, the said subject is the following general formula (1).

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl ester polymer containing a monomer unit having a silyl group represented by saponification is obtained to obtain a vinyl alcohol polymer, and then the vinyl alcohol polymer is acetalized. A method for producing an 80 mol% vinyl acetal polymer, wherein the vinyl alcohol polymer satisfies the following formula (I), and the degree of polymerization of the vinyl alcohol polymer is a weight average degree of polymerization: It is also achieved by providing a method for producing a vinyl acetal polymer characterized in that the polymer has a weight fraction of 25% by weight or less.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%)

  The vinyl acetal polymer of the present invention is excellent in adhesiveness to an inorganic substance while maintaining the characteristics inherent in the conventional vinyl acetal polymer. The interlayer film for laminated glass of the present invention is excellent in whitening resistance, penetration resistance, and adhesion to glass when exposed to a long period of time under high humidity. In the ceramic molding binder of the present invention, the obtained green sheet is homogeneous and excellent in strength. The binder for ink or paint of the present invention can have a low viscosity and a high concentration. The heat-developable photosensitive material of the present invention is excellent in storage stability of the coating solution used for its production, and also has sensitivity when developing the heat-developable photosensitive material, storage stability of the image after development, etc. Are better.

（Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数である。）
で示されるシリル基を有する単量体単位を含有するビニルエステル系重合体をけん化することによって得られるビニルアルコール系重合体をアセタール化して得られるアセタール化度４５〜８０モル％のビニルアセタール系重合体であって、前記ビニルアルコール系重合体が、下記式（Ｉ）を満足し、かつビニルアルコール系重合体の中でその重合度が重量平均重合度の３倍を超える重合体の重量分率が２５重量％以下であることを特徴とするビニルアセタール系重合体である。
２０＜Ｐｗ×Ｓ＜４６０ ・・・（Ｉ）
Ｐｗ：ビニルアルコール系重合体の重量平均重合度
Ｓ：一般式（１）で示されるシリル基を有する単量体単位の含有量（モル％） The vinyl acetal polymer of the present invention has the following general formula (1):

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl acetal polymer having a degree of acetalization of 45 to 80 mol% obtained by acetalizing a vinyl alcohol polymer obtained by saponifying a vinyl ester polymer containing a monomer unit having a silyl group represented by A weight fraction of a polymer that satisfies the following formula (I) and whose degree of polymerization exceeds three times the weight average degree of polymerization in the vinyl alcohol polymer: Is a vinyl acetal polymer characterized by being 25 wt% or less.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%)

  The silyl group-containing vinyl acetal polymer of the present invention is a product (Pw × S) of the weight average degree of polymerization (Pw) and the content of monomer units having a silyl group (S) as a raw material for producing it. ) Needs to use a silyl group-containing vinyl alcohol polymer satisfying the relationship of 20 <Pw × S <460. Pw × S preferably satisfies the relationship of 50 <Pw × S <420, more preferably 100 <Pw × S <390. When Pw × S is 20 or less, the following inconveniences occur in each application. When used as an interlayer film for laminated glass, whitening resistance, penetration resistance and adhesion to glass become insufficient. When used as a ceramic binder, the effect of improving the strength of the green sheet is insufficient. When used as a binder for ink or paint, it is difficult to achieve high concentration and low viscosity. When used as a heat-developable photosensitive material, the storage stability of the coating solution, the sensitivity when developing the heat-developable photosensitive material, or the storage stability of the image after development is lowered. In addition, when Pw × S is 460 or more, the raw material silyl group-containing vinyl alcohol polymer may not be dissolved in water unless an alkaline compound is added. Therefore, the silyl group-containing vinyl acetal heavy polymer may not be dissolved. It may be difficult to manufacture the coalescence.

  The vinyl alcohol polymer used as a raw material for producing the silyl group-modified vinyl acetal polymer of the present invention has a polymerization degree exceeding 3 times the weight average polymerization degree in the vinyl alcohol polymer. It is necessary that the weight fraction of the polymer is 25% by weight or less. Among the vinyl alcohol polymers used as a raw material for producing the vinyl acetal polymer of the present invention, the weight fraction of the polymer having a polymerization degree exceeding 3 times the weight average polymerization degree Pw is 25. The reason why inconveniences occur in each application when the weight percentage is exceeded is considered as follows.

  Among all the monomer units contained in the polymer having a silyl group, the monomer unit having a silyl group is uniformly present. Therefore, as the degree of polymerization of the polymer increases, one molecule of the polymer. The number of monomer units having a silyl group contained in is increased. And as the number of monomer units having a silyl group contained in one polymer molecule increases, the polymer is more susceptible to the influence of the silyl group. That is, a polymer having a high degree of polymerization is more susceptible to silyl groups than a polymer having a low degree of polymerization. Therefore, a silyl group-containing vinyl acetal polymer composed of a silyl group-containing vinyl alcohol polymer containing a large amount of a high degree of polymerization component contains a large amount of a polymer that is easily affected by the silyl group. Therefore, the following inconveniences occur in each application. When used for an interlayer film for laminated glass, the adhesion with glass becomes too high, so that balance with penetration resistance cannot be achieved. When used as a ceramic binder, the interaction with the ceramic powder becomes too large, making it difficult to prepare a uniform slurry. When used as a binder for ink or paint, the interaction between silyl groups becomes too large, making it difficult to achieve high concentration and low viscosity. When used as a heat-developable photosensitive material, the interaction between silyl groups becomes too large, so that the storage stability of the coating solution is lowered, and the sensitivity when the heat-developable photosensitive material is developed is lowered.

  On the other hand, the smaller the degree of polymerization of the polymer, the smaller the number of monomer units having a silyl group contained in one molecule of the polymer. The smaller the number of monomer units having a silyl group contained in one molecule of the polymer, the less likely the polymer is affected by the silyl group. That is, the effect of the silyl group is less likely to appear in a polymer having a lower degree of polymerization than in a polymer having a higher degree of polymerization. Therefore, the silyl group-containing vinyl alcohol polymer containing a large amount of the low polymerization degree component contains many polymers having a small effect of the silyl group.

  The vinyl alcohol polymer used as a raw material for producing the silyl group-containing vinyl acetal polymer of the present invention is a polymer having a polymerization degree smaller than ½ times the weight average polymerization degree Pw. The fraction is preferably 12% by weight or less. Among vinyl alcohol polymers, when the polymer weight fraction is less than ½ times the weight average degree of polymerization and the weight fraction of the polymer exceeds 12% by weight, the low degree of polymerization with little effect of silyl groups Since many components are contained, the following disadvantages may occur in each application. When used for the interlayer film for laminated glass, there is a possibility that the whitening resistance and the adhesion between the glass and the glass cannot be balanced. When used as a ceramic binder, the effect of improving the strength of the green sheet may be reduced because the interaction with the ceramic powder becomes too small. When used as a binder for ink or paint, the interaction between silyl groups becomes small, so there is a risk that it will be difficult to achieve high concentration and low viscosity. When used as a heat-developable photosensitive material, the interaction between silyl groups is small, so that the storage stability of an image after development may be lowered.

  The weight average polymerization degree (Pw) and polymerization degree distribution of the vinyl alcohol polymer used as a raw material when producing the silyl group-containing vinyl acetal polymer of the present invention are determined by, for example, GPC-LALLS measurement. Can do. That is, by re-saponifying and purifying the silyl group-containing PVA to a saponification degree of 99.5 mol% or more, and then dividing the weight average molecular weight determined by GPC-LALLS by the formula weight 44 of the vinyl alcohol monomer unit. The weight average degree of polymerization is determined. Further, the weight fraction of the polymer having a polymerization degree within a specific range can be determined from the integral polymerization degree distribution obtained from GPC-LALLS measurement.

In the vinyl alcohol polymer used as a raw material for producing the silyl group-containing vinyl acetal polymer of the present invention, the content S (mol%) of the monomer unit having a silyl group is determined before saponification. It is calculated | required from the proton NMR of the silyl group containing vinyl ester polymer which is a raw material of this. When proton NMR of the silyl group-containing vinyl ester polymer before saponification is measured here, the silyl group-containing vinyl ester polymer is purified by reprecipitation with hexane-acetone to remove unreacted silyl from the polymer. The monomer having a group is completely removed, followed by drying at 90 ° C. under reduced pressure for 2 days, and then dissolving in CDCl ₃ solvent for analysis.

  In addition, the silyl group-containing vinyl acetal polymer of the present invention is hydrolyzed to obtain a silyl group-containing vinyl alcohol polymer, and further acetylated to obtain a silyl group-containing vinyl ester polymer. The content of the monomer unit having a silyl group can also be determined by proton NMR measurement according to the above, and this value is substantially the same as the above S (mol%). An example of the preparation method of the measurement sample in this case is as follows. First, the silyl group-containing vinyl acetal polymer of the present invention is reacted with hydroxyamine hydrochloride in an alcohol solution, and the resulting reaction product is reprecipitated in a water / alcohol mixed solvent and sufficiently purified to contain a silyl group. A vinyl alcohol polymer is obtained. Subsequently, the hydroxyl group is acetylated by heating the silyl group-containing vinyl alcohol polymer in pyridine / acetic anhydride, and then reprecipitated in a water / acetone mixed solvent to be sufficiently purified. By performing drying at a temperature of 80 ° C. under reduced pressure for 3 days, a silyl group-containing vinyl ester polymer for analysis is prepared.

The vinyl alcohol polymer used as a raw material for producing the silyl group-containing vinyl acetal polymer of the present invention preferably satisfies the following formula (II).
0.1 / 100 ≦ (A−B) / (B) ≦ 50/100 (II)
A: Content of silicon atom in vinyl alcohol polymer (unit: ppm)
B: Content of silicon atom in vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed with Soxhlet extraction with methanol (unit: ppm)
Here, A and B are measured by ICP emission spectrometry after ashing the measurement sample.

  Here, in order to obtain the silicon atom content (B), a standard washing method of the vinyl alcohol polymer is a washing operation with methanol containing sodium hydroxide (1 part by weight of vinyl alcohol polymer). In contrast, 10 parts by weight of a methanol solution containing sodium hydroxide was added so that the molar ratio of sodium hydroxide to vinyl alcohol monomer units in the vinyl alcohol polymer was 0.01. The operation of boiling the mixture for 1 hour and then filtering the polymer) is repeated 5 times, followed by Soxhlet extraction with methanol for 1 week. In the above washing method, the washing operation with methanol containing sodium hydroxide and the Soxhlet extraction with methanol are performed until the silicon atom content in the vinyl alcohol polymer is almost unchanged, and this condition is satisfied. In such a range, the number of washing operations with methanol containing sodium hydroxide and the Soxhlet extraction period with methanol may be appropriately increased or decreased.

  The silicon atom content (A) of the vinyl alcohol polymer is considered to indicate the content of all silicon atoms contained in the vinyl alcohol polymer. Further, the content (B) of the silicon atom in the vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed by Soxhlet extraction with methanol is directly incorporated into the main chain of the vinyl alcohol polymer. This is considered to indicate the content of silicon atoms derived from the silyl group-containing monomer.

  In determining the silicon atom content (B), the vinyl alcohol polymer is washed with methanol containing sodium hydroxide, and at that time, the siloxane bond (—Si—O—Si—) is broken. At this time, the silyl group-containing monomer that was not directly incorporated into the main chain of the vinyl alcohol polymer and was bonded to the main chain of the vinyl alcohol polymer via a siloxane bond was obtained from the vinyl alcohol polymer. Is removed from the polymer. Therefore, the silicon atom content (B) is considered to indicate the silicon atom content in a state in which the silyl group-containing monomer not directly incorporated in the main chain of the vinyl alcohol polymer is removed. It is done. Therefore, (AB) in the above relational expression 0.1 / 100 ≦ (AB) / (B) ≦ 50/100 represents a silyl group that is not directly introduced into the main chain of the vinyl alcohol polymer. It is considered that the content of the silyl group derived from the monomer unit it has is shown.

  When the value of (AB) / (B) in the silyl group-containing vinyl alcohol polymer is large, the silyl group-containing vinyl alcohol polymer contains many monomer units having an excess silyl group. In the case where the value of (AB) / (B) in the silyl group-containing vinyl alcohol polymer is small, it is not directly introduced into the main chain of the vinyl alcohol polymer. This means that the amount of the monomer unit having a silyl group is small.

  A preferred range of (A-B) / (B) is 0.1 / 100 to 50/100, a more preferred range is 0.3 / 100 to 25/100, and a particularly preferred range is 0.4 / 100. ~ 20/100.

  When (A-B) / (B) exceeds 50/100, a siloxane bond between a monomer unit containing an excess silyl group and a silyl group-containing monomer unit incorporated in the main chain ( -Si-O-Si-) are formed in large numbers. Therefore, when the silyl group-containing vinyl acetal polymer obtained using the silyl group-containing vinyl alcohol polymer as a raw material is used for each application, the following inconvenience may occur. When used for an interlayer film for laminated glass, the adhesion with glass becomes too high, and there is a risk that the penetration resistance cannot be balanced. When used as a ceramic binder, since the interaction with the ceramic powder becomes too large, it may be difficult to prepare a uniform slurry. When used as a binder for ink or paint, the interaction between silyl groups increases, which may make it difficult to achieve high concentration and low viscosity. When used as a heat-developable photosensitive material, the interaction between silyl groups increases, so the storage stability of the coating solution may decrease, and the sensitivity when developing the heat-developable photosensitive material may decrease. There is.

  On the other hand, when (AB) / (B) is less than 0.1 / 100, a monomer unit containing an excess silyl group and a silyl group-containing monomer unit incorporated in the main chain As a result, the amount of silyl groups contained in the silyl group-containing vinyl acetal polymer is reduced. Therefore, when the silyl group-containing vinyl acetal polymer is used for each application, the following inconvenience may occur. When used for the interlayer film for laminated glass, there is a possibility that the whitening resistance and the adhesion between the glass and the glass cannot be balanced. When used as a ceramic binder, the effect of improving the strength of the green sheet may be reduced because the interaction with the ceramic powder becomes too small. When used as a binder for ink or paint, the interaction between silyl groups is small, so there is a risk that it will be difficult to achieve high concentration and low viscosity. When used as a heat-developable photosensitive material, the interaction between silyl groups is small, so that the storage stability of an image after development may be lowered. Furthermore, since the silyl group-containing vinyl alcohol polymer in which (A-B) / (B) is less than 0.1 / 100 is costly to clean at the time of production, it is not always practical from the economical aspect. Absent.

  The vinyl alcohol polymer used as a raw material for producing the silyl group-containing vinyl acetal polymer of the present invention preferably has a 4% aqueous solution having a pH of 4-8. The more preferable range of the pH of the 4% aqueous solution is 4.5 to 7, and the particularly preferable range is 5 to 6.5. When the pH of the 4% aqueous solution is less than 4, when the silyl group-containing vinyl acetal polymer obtained using the silyl group-containing vinyl alcohol polymer as a raw material is used for each application, there are the following disadvantages. May occur. When used for an interlayer film for laminated glass, the adhesion with glass becomes too high, and there is a risk that the penetration resistance cannot be balanced. When used as a ceramic binder, since the interaction with the ceramic powder becomes too large, it may be difficult to prepare a uniform slurry. When used as a binder for ink or paint, the interaction between silyl groups becomes too large, and it may be difficult to achieve high concentration and low viscosity. When used as a heat-developable photosensitive material, the interaction between silyl groups becomes too large, so that the storage stability of the coating solution is lowered, or the sensitivity when developing the heat-developable photosensitive material is lowered. There is a fear. On the other hand, when the pH of the 4% aqueous solution exceeds 8, when the silyl group-containing vinyl acetal polymer obtained using the silyl group-containing vinyl alcohol polymer as a raw material is used for each application, the following inconveniences are caused. May occur. When used for the interlayer film for laminated glass, there is a possibility that the whitening resistance and the adhesion between the glass and the glass cannot be balanced. When used as a ceramic binder, the effect of improving the strength of the green sheet may be reduced because the interaction with the ceramic powder becomes too small. When used as a binder for ink or paint, the interaction between silyl groups is small, so there is a risk that it will be difficult to achieve high concentration and low viscosity. When used as a heat-developable photosensitive material, the interaction between silyl groups is small, so that the storage stability of an image after development may be lowered.

  The vinyl ester polymer used as a raw material when producing the silyl group-containing vinyl acetal polymer of the present invention contains a monomer unit having a silyl group represented by the following general formula (1).

（Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数である。）

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)

Here, examples of the alkyl group having 1 to 5 carbon atoms represented by R ¹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, and isobutyl. Group, n-pentyl group, tert-pentyl group, isopentyl group and the like. Examples of the alkoxyl group represented by R ² include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, tert-butoxy group, pentoxy group, hexyloxy group, octyloxy group, lauryloxy group, and oleyloxy group. In addition, examples of the acyloxyl group include an acetoxy group and a propionyloxy group. These alkoxyl groups or acyloxyl groups may have an oxygen-containing substituent, and examples of the substituent include alkoxyl groups such as a methoxy group and an ethoxy group.

  The silyl group-containing vinyl alcohol polymer used in the present invention is obtained by copolymerizing a vinyl ester monomer and a monomer having a silyl group represented by the general formula (1), and saponifying the resulting vinyl ester polymer. Can be manufactured.

  The silyl group-containing vinyl alcohol polymer is obtained by combining a vinyl ester monomer and a monomer having a silyl group represented by the general formula (1) with 2-mercaptoethanol, n-dodecyl mercaptan, mercaptoacetic acid, 3- It can also be produced by copolymerization in the presence of a thiol compound such as mercaptopropionic acid and saponifying the resulting vinyl ester polymer. By this method, a vinyl alcohol polymer in which a functional group derived from a thiol compound is introduced at the terminal is obtained.

  Examples of vinyl ester monomers used in the production of such silyl group-containing vinyl alcohol polymers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, and stearic acid. Examples thereof include vinyl, vinyl benzoate, vinyl pivalate and vinyl versatate, and vinyl acetate is particularly preferable.

  As a monomer having a silyl group represented by the general formula (1) used for radical copolymerization with a vinyl ester monomer, a compound represented by the following general formula (2) or the following general formula (3) is used. Can be mentioned.

（式中、Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数であり、ｎは０〜４の整数である。）

(Wherein R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and m is (It is an integer from 0 to 2, and n is an integer from 0 to 4.)

（式中、Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、Ｒ^３は水素原子またはメチル基であり、Ｒ^４は水素原子または炭素数１〜５のアルキル基であり、Ｒ^５は炭素数１〜５のアルキレン基であるかまたは酸素原子もしくは窒素原子を含む２価の炭化水素基であり、ｍは０〜２の整数である。）

(In the formula, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and R ³ Is a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁵ is an alkylene group having 1 to ⁵ carbon atoms, or a divalent atom containing an oxygen atom or a nitrogen atom And m is an integer of 0 to 2.)

In the general formula (2) and general formula (3), examples of the alkyl group having 1 to 5 carbon atoms represented by R ¹ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, Examples include sec-butyl group, tert-butyl group, isobutyl group, n-pentyl group, tert-pentyl group, isopentyl group and the like. Examples of the alkoxyl group represented by R ² include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, tert-butoxy group, pentoxy group, hexyloxy group, octyloxy group, lauryloxy group, and oleyloxy group. In addition, examples of the acyloxyl group include an acetoxy group and a propionyloxy group. These alkoxyl groups or acyloxyl groups may have an oxygen-containing substituent, and examples of the substituent include alkoxyl groups such as a methoxy group and an ethoxy group. Examples of the alkyl group having 1 to 5 carbon atoms represented by R ⁴ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, and an isobutyl group. , N-pentyl group, tert-pentyl group, isopentyl group and the like. Examples of the alkylene group having 1 to 5 carbon atoms represented by R ⁵ include a methylene group, an ethylene group, a dimethylethylene group, a trimethylene group, a tetramethylene group, and a pentamethylene group, and an oxygen atom or a nitrogen atom. Examples of the divalent hydrocarbon group to be included include —CH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ —, —CH ₂ CH ₂ NHCH ₂ CH ₂ —, —CH ₂ CH ₂ NHCH ₂ —, —CH ₂ CH ₂ N ( _{CH 3) CH 2 CH 2 -} , - CH 2 CH 2 N (CH 3) CH 2 -, - CH 2 CH 2 OCH 2 CH 2 CH 2 -, - CH 2 CH 2 OCH 2 CH 2 -, - CH 2 CH ₂ OCH ₂ — and the like can be mentioned.

  Examples of the monomer represented by the above formula (2) include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, and allyltrimethoxy. Silane, allylmethyldimethoxysilane, allyldimethylmethoxysilane, allyltriethoxysilane, allylmethyldiethoxysilane, allyldimethylethoxysilane, vinyltris (β-methoxyethoxy) silane, vinylisobutyldimethoxysilane, vinylethyldimethoxysilane, vinylmethoxydi Butoxysilane, vinyldimethoxybutoxysilane, vinyltributoxysilane, vinylmethoxydihexyloxysilane, vinyldimethoxyhexyloxysilane, vinyl Rehexyloxysilane, vinylmethoxydioctyloxysilane, vinyldimethoxyoctyloxysilane, vinyltrioctyloxysilane, vinylmethoxydilauryloxysilane, vinyldimethoxylauryloxysilane, vinylmethoxydioleoyloxysilane, vinyldimethoxyoleyloxysilane, etc. Is mentioned.

  In the above formula (2), when a monomer having a silyl group with n of 1 or more and a vinyl ester monomer are copolymerized, the degree of polymerization of the resulting vinyl ester polymer tends to decrease. In that respect, when vinyltrimethoxysilane is copolymerized with a vinyl ester monomer, it is possible to suppress a decrease in the degree of polymerization of the resulting vinyl ester polymer, and industrial production is easy and inexpensive. Since it can be obtained, it can be preferably used.

  Examples of the monomer represented by the above formula (3) include 3- (meth) acrylamide-propyltrimethoxysilane, 3- (meth) acrylamide-propyltriethoxysilane, and 3- (meth) acrylamide-propyl. Tri (β-methoxyethoxy) silane, 2- (meth) acrylamide-ethyltrimethoxysilane, 1- (meth) acrylamide-methyltrimethoxysilane, 2- (meth) acrylamide-2-methylpropyltrimethoxysilane, 2- (Meth) acrylamide-isopropyltrimethoxysilane, N- (2- (meth) acrylamide-ethyl) -aminopropyltrimethoxysilane, (3- (meth) acrylamide-propyl) -oxypropyltrimethoxysilane, 3- (meta ) Acrylamide-propyltria Toxisilane, 2- (meth) acrylamide-ethyltriacetoxysilane, 4- (meth) acrylamide-butyltriacetoxysilane, 3- (meth) acrylamide-propyltripropionyloxysilane, 2- (meth) acrylamide-2-methylpropyl Triacetoxysilane, N- (2- (meth) acrylamide-ethyl) -aminopropyltriacetoxysilane, 3- (meth) acrylamide-propylisobutyldimethoxysilane, 2- (meth) acrylamide-ethyldimethylmethoxysilane, 3- ( Meth) acrylamide-propylmethyldiacetoxysilane, 2- (meth) acrylamide-2-methylpropylhydrogendimethoxysilane, 3- (N-methyl- (meth) acrylamide) -propyltrimethoxy Silane, 2- (N-ethyl- (meth) acrylamide) -ethyltriacetoxysilane, etc. are mentioned.

  Among these monomers, 3- (meth) acrylamide-propyltrimethoxysilane and 3- (meth) acrylamide-propyltriacetoxysilane are preferably used because they are relatively easy to manufacture industrially and can be obtained at low cost. 2- (meth) acrylamido-2-methylpropyltrimethoxysilane and 2- (meth) acrylamide-2-methylpropyltriacetoxysilane are remarkably stable to acids or alkalis, It can be preferably used.

  Examples of a method for copolymerizing a monomer having a silyl group and a vinyl ester monomer include known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these methods, a bulk polymerization method performed without a solvent or a solution polymerization method performed using a solvent such as alcohol is usually employed. When polymerizing by a bulk polymerization method or a solution polymerization method, the weight fraction of a polymer having a polymerization degree exceeding 3 times the weight average polymerization degree Pw is 25% by weight or less, and preferably the polymerization degree is a weight average polymerization. The polymerization method for obtaining the vinyl alcohol polymer of the present invention in which the weight fraction of the polymer smaller than ½ times the degree Pw is 12% by weight or less cannot be generally limited depending on the polymerization conditions and the like. From the viewpoint of suppressing the ratio of the degree component and the low degree of polymerization component, the continuous polymerization method is most preferable. As a continuous polymerization system, for example, a 1-2 tank continuous polymerization system is preferable, and a 1 tank continuous polymerization system is more preferable. In the case of the batch method, the ratio of the high polymerization degree component and the low polymerization degree component changes depending on the polymerization rate of the vinyl ester monomer, etc., and as the polymerization rate increases, the high polymerization degree component and the low polymerization degree component Since the ratio increases, it is preferable to polymerize at a relatively low polymerization rate. The suitable polymerization rate in the batch system cannot be defined unconditionally because it varies depending on the polymerization conditions and the like, but the polymerization rate of the vinyl ester monomer is preferably 10 to 80%, more preferably 15 to 50%. Examples of the alcohol used as a solvent when performing a copolymerization reaction by employing a solution polymerization method include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. Examples of the initiator used in the copolymerization reaction include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), 1,1′-azobis (cyclohexane- Azo initiators such as 1-carbonitrile) and 2,2′-azobis (N-butyl-2-methylpropionamide); peroxide initiators such as benzoyl peroxide and n-propyl peroxycarbonate A well-known initiator is mentioned. Although there is no restriction | limiting in particular about the polymerization temperature at the time of performing a copolymerization reaction, The range of 50 to 180 degreeC is suitable.

  When radically copolymerizing a monomer having a silyl group and a vinyl ester monomer, a copolymerizable monomer may be copolymerized as necessary as long as the effects of the present invention are not impaired. It can be polymerized. Examples of such monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; carboxylic acids such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, and itaconic anhydride; Derivatives thereof; acrylic acid or salts thereof, acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate; methacrylic acid or salts thereof, methyl methacrylate, ethyl methacrylate, n methacrylate Methacrylic acid esters such as propyl and isopropyl methacrylate; Acrylamide derivatives such as acrylamide, N-methylacrylamide and N-ethylacrylamide; and methacrylamides such as methacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide Body; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether; hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1,4-butanediol vinyl ether Allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, hexyl allyl ether; monomers having an oxyalkylene group; isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol Hydroxy group-containing α-olefins such as 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3-buten-1-ol; Monomers having sulfonic acid groups such as sulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyl Cationic groups such as dimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine And the like. The amount of the monomer having a silyl group and a monomer copolymerizable with the vinyl ester monomer varies depending on the purpose and use of the monomer, but all the monomers used for copolymerization are usually used. The ratio based on the monomer is 20 mol% or less, preferably 10 mol% or less.

  The vinyl ester polymer obtained by copolymerizing a monomer having a silyl group and a vinyl ester monomer is then saponified in a solvent according to a known method to give a vinyl alcohol polymer. Led.

  As a catalyst for the saponification reaction of a vinyl ester polymer, an alkaline substance is usually used. Examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. Can be mentioned. The amount of the alkaline substance used is preferably in the range of 0.004 to 0.5 in terms of a molar ratio based on the vinyl ester monomer unit in the vinyl ester polymer. It is particularly preferable that the value falls within the range. The saponification catalyst may be added all at once in the early stage of the saponification reaction, or a part thereof may be added in the early stage of the saponification reaction, and the rest may be added and added during the saponification reaction.

  Examples of the solvent that can be used for the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, diethyl sulfoxide, dimethylformamide, and the like. Among these solvents, methanol is preferably used, and in its use, the water content of methanol is preferably 0.001 to 1% by weight, more preferably 0.003 to 0.9% by weight, and particularly preferably 0.005 to 0.005%. It should be adjusted to 0.8% by weight.

  The saponification reaction is preferably performed at a temperature of 5 to 80 ° C, more preferably 20 to 70 ° C. The time required for the saponification reaction is preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours. The saponification reaction can be carried out by either a batch method or a continuous method. After completion of the saponification reaction, the remaining saponification catalyst may be neutralized as necessary, and examples of usable neutralizers include organic acids such as acetic acid and lactic acid, and ester compounds such as methyl acetate. Can do.

  The saponification degree of the silyl group-containing vinyl alcohol polymer used in the present invention is not particularly limited, but the saponification degree is preferably 80 mol% or more, more preferably 85 mol% or more, and particularly preferably 90 mol% or more. From the viewpoint of making the silyl group-containing vinyl acetal polymer favorable for various uses, the optimum saponification degree of the silyl group-containing vinyl alcohol polymer is preferably 95 mol% or more.

  The vinyl alcohol polymer obtained by the saponification reaction can be washed if necessary, and this operation adjusts the value of (AB) / (B) in the vinyl alcohol polymer described above. Useful as a means.

  Usable cleaning liquids include lower alcohols such as methanol, lower fatty acid esters such as methyl acetate, and mixtures thereof. A small amount of water or an alkali or acid is added to these cleaning liquids. May be.

  The method employed for washing the vinyl alcohol polymer is the polymerization rate when the vinyl ester monomer and the monomer having a silyl group are copolymerized, and the vinyl ester polymer obtained by the copolymerization. It differs depending on the degree of polymerization, the degree of saponification of the vinyl alcohol polymer obtained by saponifying the vinyl ester polymer, and it is difficult to uniformly define this. As one of the methods, for example, it is obtained by saponifying a copolymer of a vinyl ester monomer and a monomer having a silyl group (vinyl ester polymer) in an alcohol solution, before drying. 1 to 20 times the amount of wet alcoholic polymer impregnated with alcohol or the like, a lower alcohol such as methanol, a lower fatty acid ester such as methyl acetate, or a mixture thereof as a washing solution, The method of washing for about 30 minutes to 10 hours under the temperature condition of the boiling point of the washing liquid can be mentioned.

  The washed PVA produced by the above method is acetalized in a hydrous solvent under acidic conditions according to a known method to obtain a vinyl acetal polymer. The vinyl acetal polymer used in the present invention has an acetalization degree of 45 to 80 mol%, preferably 50 to 80 mol%, particularly preferably 60 to 80 mol%. Here, the degree of acetalization is the ratio (mol%) of the hydroxyl group of the vinyl alcohol polymer consumed as a result of the acetalization reaction of the aldehyde compound with the hydroxyl group of the vinyl alcohol polymer. The degree of acetalization can be analyzed according to the method described in JIS K6728.

  When the degree of acetalization of the vinyl acetal polymer is less than 45 mol%, it may be difficult to recover the powdered reaction product obtained when acetalizing PVA. Such inconvenience may occur. When used for an interlayer film for laminated glass, the whitening resistance of the laminated glass may be reduced. When used as a ceramic molding binder, the surface state of the ceramic green sheet may deteriorate, or the strength of the ceramic green sheet may deteriorate. When used as a binder for ink or paint, it may be difficult to obtain an ink or paint having a low solution viscosity and a high solid content ratio (high pigment content), and is formed by printing or painting. There is a risk of problems in the durability of the coating film. When used in a heat-developable photosensitive material, the storage stability of the coating solution, the sensitivity during development, or the image stability after development may be deteriorated.

If the degree of acetalization of the vinyl acetal polymer exceeds 80 mol%, the production of the vinyl acetal polymer may be difficult, or the compatibility between the vinyl acetal polymer and the plasticizer may be reduced. In addition, the following inconveniences may occur in each application.
When used for an interlayer film for laminated glass, the whitening resistance of the laminated glass edge may be lowered under high humidity. When used as a ceramic molding binder, the surface state of the ceramic green sheet may be deteriorated.

  As a method for acetalizing PVA, for example, a) The PVA is dissolved in water by heating to prepare an aqueous solution having a concentration of 5 to 30% by weight, cooled to 5 to 50 ° C., and then a predetermined amount of aldehyde And then cooling to -10 to 30 ° C and adding an acid to bring the pH of the aqueous solution to 1 or less to start the acetalization reaction, b) 5-30% by weight by dissolving the PVA in water by heating An aqueous solution with a concentration is prepared, cooled to 5 to 50 ° C, and the pH of the aqueous solution is reduced to 1 or less by adding an acid, then cooled to -10 to 30 ° C, and a predetermined amount of aldehyde is added to acetalize. Examples thereof include a method for starting the reaction.

  Examples of the aldehyde compound used in the acetalization reaction include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, benzaldehyde, and the like, and these can be used alone or in admixture of two or more. Examples of preferred aldehyde compounds are alkyl aldehydes having 4 or less carbon atoms, and benzaldehyde, with butyraldehyde being particularly preferred. Moreover, you may use together the aldehyde compound containing carboxylic acid as needed.

  Examples of the acid used in the acetalization reaction usually include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as p-toluenesulfonic acid. These may be used alone or in combination of two or more. Can be used. The time required for the acetalization reaction is usually about 1 to 10 hours, and the reaction is preferably carried out with stirring. In addition, when the acetal reaction is performed under the above-described temperature conditions, the reaction may be continued at a high temperature of about 50 to 80 ° C. if the degree of acetalization of the vinyl acetal polymer does not increase.

  The powdery reaction product obtained after the acetalization reaction is filtered and then neutralized with an aqueous alkali solution. Examples of alkali compounds used for neutralization include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, as well as amine compounds such as ammonia, triethylamine, and pyridine. After neutralizing with an alkaline aqueous solution in this way, the desired vinyl acetal polymer is obtained by washing with water and drying.

  The vinyl acetal polymer of the present invention thus produced can be used for various applications. Especially, it is used suitably for uses, such as a laminated glass interlayer film, a ceramic molding binder, an ink or paint binder, and a heat-developable photosensitive material. Hereinafter, these uses will be sequentially described.

  When the vinyl acetal polymer of the present invention is used for an interlayer film for laminated glass, a plasticizer is added to the vinyl acetal polymer. Examples of the plasticizer that can be used include triethylene glycol-di-2-ethylhexanoate, oligoethylene glycol-di-2-ethylhexanoate, and tetraethylene glycol-di n-heptanoate. Is 30 to 50 parts by weight per 100 parts by weight of the vinyl acetal polymer. When the addition amount of the plasticizer is less than 30 parts by weight, the interlayer film becomes too hard, so that the cutting property may be reduced when the interlayer film is manufactured. The plasticizer tends to bleed out.

  For the purpose of adjusting the adhesive force between the interlayer film for laminated glass and the glass, a metal salt of a carboxylic acid having 2 to 10 carbon atoms may be added to the vinyl acetal polymer. Examples of the metal salt include alkali metal salts such as sodium, potassium and magnesium or alkaline earth metal salts. The amount of the metal salt of a carboxylic acid having 2 to 10 carbon atoms to the vinyl acetal polymer is preferably 1 to 200 ppm, and more preferably 10 to 150 ppm. Moreover, you may add additives, such as a ultraviolet absorber, a light stabilizer, antioxidant, surfactant, and a coloring agent, with respect to a vinyl acetal type polymer as needed.

  As a method of producing an interlayer film for laminated glass from a vinyl acetal polymer, a predetermined amount of a plasticizer and other additives are blended into a vinyl acetal polymer and uniformly kneaded, and an extrusion method, a calendar method, a press And a method of forming a film into a sheet using a molding method such as a casting method, a casting method or an inflation method.

  The thickness of the interlayer film for laminated glass is usually 0.3 to 1.6 mm, and the interlayer film for laminated glass may be used as a single layer or may be used by laminating two or more layers.

  The method for producing a laminated glass using the interlayer film for laminated glass produced from the vinyl acetal polymer is not particularly limited. As the method, for example, a laminated glass interlayer film is sandwiched between two transparent glass plates, put into a rubber bag, preliminarily bonded at a temperature of about 70 to 110 ° C. while sucking under reduced pressure, and then an autoclave is used. A laminated glass can be obtained by performing the main bonding at a temperature of about 120 to 150 ° C. under a pressure of about 1 to 1.5 MPa.

  The glass plate that can be used for the laminated glass is not particularly limited, and examples thereof include float plate glass, polished plate glass, mold plate glass, netted plate glass, lined plate glass, heat ray absorbing plate glass, and colored plate glass. It is also possible to use a transparent resin plate such as a polycarbonate plate or a polymethyl methacrylate plate in combination with these glass plates.

  When the vinyl acetal polymer of the present invention is used as a ceramic molding binder and a ceramic powder is molded, an organic solvent is usually used. Moreover, you may use a plasticizer together in that case. Examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, n-propanol and butanol; cellsolves such as methyl cellsolve and butylcellsolve; ketones such as acetone and methylethylketone; aromatics such as toluene and xylene Hydrocarbons: Halogen-based hydrocarbons such as dichloromethane and chloroform can be used, and these can be used alone or in combination of two or more.

  Examples of plasticizers include triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di n-heptanoate, tetraethylene glycol-di n-heptanoate, etc. Of dicarboxylic acids such as dioctyl adipate, dibutyl adipate, dioctyl phthalate, dibutyl phthalate, etc., which can be used alone or in combination of two or more thereof .

Ceramic powders include metal or non-metal oxide or non-oxide powders used in the manufacture of ceramics. Specific examples thereof include Li, K, Mg, B, Al, Si, Cu, Ca, Sr, Ba, Zn, Cd, Ga, In, Y, lanthanoid, actinoid, Ti, Zr, Hf, Bi, V, and Nb. , Ta, W, Mn, Fe, Co, Ni, and other oxides, carbides, nitrides, borides, sulfides, and the like. Furthermore, when classifying specific examples of the oxide powders usually contain more metal elements referred to as double oxides from the crystal _{structure, NaNbO 3, SrZrO 3, PbZrO} 3, SrTiO 3 as taking a perovskite structure, BaZrO ₃ , PbTiO ₃ , BaTiO _3, etc. have a spinel structure, and MgAl ₂ O ₄ , ZnAl ₂ O ₄ , CoAl ₂ O ₄ , NiAl ₂ O ₄ , MgFe ₂ O _4, etc. have an ilmenite type structure. MgTiO ₃ , MnTiO ₃ , FeTiO _3, etc., and those having a garnet type structure include GdGa ₅ O ₁₂ , Y ₆ Fe ₅ O _12, etc. These ceramic powders may be used alone or as a mixture of two or more.

  A molding method suitable for molding a ceramic powder using the vinyl acetal polymer of the present invention as a ceramic molding binder is a slurry containing an organic solvent, a ceramic powder, and a vinyl acetal polymer as main components. This is a so-called sheet forming method in which a ceramic green sheet is obtained by coating the substrate on a carrier film using a blade coater, drying, and then releasing from the carrier film. In this molding method, the slurry applied on the carrier film is added with a peptizer, a plasticizer, a lubricant, etc., if necessary, in addition to the organic solvent, the ceramic powder, and the vinyl acetal polymer. It may be.

  Although the usage-amount of a vinyl acetal type polymer is suitably adjusted with the use purpose of a ceramic green sheet, it is 3-20 weight part normally with respect to 100 weight part of ceramic powder, Preferably it is 5-15 weight part.

  When ceramic powder is formed by employing the above-described forming method, the ceramic powder needs to be well dispersed in the slurry. There is no particular limitation on the method of dispersing the ceramic powder in the slurry, and various methods such as a method using a media type disperser such as a bead mill, a ball mill, an attritor, a paint shaker, a sand mill, a kneading method, a method using a three roll, etc. Can be used. In this case, as the dispersant, an anionic dispersant having a carboxylic acid group, a maleic acid group, a sulfonic acid group, a phosphoric acid group or the like in the molecule may be used in combination. The use of agents is preferred.

  The thickness of the ceramic green sheet varies depending on the purpose of use, but is usually in the range of 1 to 300 μm. Moreover, although the drying temperature at the time of drying the coating film formed on the carrier film is suitably adjusted with the thickness etc. of a ceramic green sheet, it is the range of 60-200 degreeC in general.

  The ceramic green sheet obtained by molding the ceramic powder using the vinyl acetal polymer of the present invention as a ceramic molding binder forms electrodes on various electronic components, especially ceramic green sheets, and is stacked and pressure-bonded. Thereafter, it can be suitably used for a chip-type multilayer capacitor produced by a process of simultaneously firing an electrode and a ceramic, a circuit board of an IC chip, and the like.

  When the vinyl acetal polymer of the present invention is used as a binder for ink or paint, the content of the vinyl acetal polymer in the ink or paint is preferably 1 to 35% by weight, more preferably 5 to 25% by weight. . The ink and paint may contain, for example, a solvent in addition to 5 to 25% by weight of pigment and 5 to 25% by weight of vinyl acetal polymer.

  The pigment contained in the ink or paint is not particularly limited, and various organic and inorganic pigments can be used depending on the application. Examples of the solvent used include alcohols such as ethyl alcohol and esters such as ethyl acetate.

  The binder for ink or paint comprising the vinyl acetal polymer of the present invention can be used in combination with an extender resin, an auxiliary agent and the like. The vinyl acetal polymer of the present invention can also be used simply as an additive for ink.

  When the ink or paint binder of the present invention is used, the viscosity after adding one or more pigments to the solution containing the ink or paint binder and kneading the resulting pigment paste is: The viscosity of the pigment paste is significantly lower than the viscosity predicted from the viscosity of the vinyl acetal polymer solution used, compared to the case where a conventionally known vinyl acetal polymer is used as a binder for ink or paint. The effect of doing. This means that the amount of varnish or solvent used in adjusting the viscosity of the ink or paint can be reduced and the pigment content can be increased. As a result, by using the ink or paint binder of the present invention, it is necessary for the ink or paint to increase the degree of coloring while maintaining the optimum viscosity, or to lower the viscosity without changing the degree of coloring. The required performance can be satisfied.

  The photothermographic material containing the vinyl acetal polymer of the present invention comprises a coating liquid comprising a vinyl acetal polymer, an organic silver salt and / or a photosensitive silver halide, a reducing agent and a solvent on a support. It is produced by coating and optionally crosslinking with a compound containing an isocyanate group.

  The amount of the organic silver salt used is preferably 1 to 500 parts by weight, more preferably 2 to 50 parts by weight, based on 10 parts by weight of the vinyl acetal polymer. The organic silver salt preferably has a particle size of 0.01 to 10 μm, more preferably 0.1 to 5 μm. The organic silver salt is a colorless or white silver salt that is relatively stable to light, and is reduced to a metallic silver by being reduced by a reducing agent in the temperature range of 80 ° C. or higher in the presence of photosensitive silver halide. If it is, it will not be restrict | limited in particular. Examples of such organic silver salts include 3-mercapto-4-phenyl-1,2,4-triazole, 2-mercapto-5-aminothiazole, 1-phenyl-5-mercaptotetrathiazole, 2-mercaptobenzo Silver salts of mercaptans such as thiazole, mercaptooxadiazole, mercaptotriazine; silver salts of thione compounds such as thioamide, thiopyridine, S-2-aminophenylthiosulfuric acid; aliphatic carboxylic acid, capric acid, lauric acid, myristic acid , Palmitic acid, stearic acid, behenic acid, maleic acid, fumaric acid, tartaric acid, furonic acid, linoleic acid, oleic acid, hydroxystearic acid, adipic acid, sebacic acid, succinic acid, acetic acid, butyric acid, camphoric acid, dithioacetic acid, etc. Dithiocarboxylic acid, thioglycolic acid, aromatic carvone , Silver salts of organic carboxylic acids such as aliphatic carboxylic acids having a thione carboxylic acid or thioether group; silver salts of imidazoles such as 2-mercaptobenzimidazole, silver salts of tetrazaindene; silver-containing metal amino alcohols, organic Examples thereof include silver salts of aliphatic carboxylic acids, and silver behenate is particularly preferably used.

  The amount of photosensitive silver halide used is preferably from 0.0005 to 0.2 parts by weight, more preferably from 0.01 to 0.2 parts by weight, based on 100 parts by weight of the organic silver salt. The photosensitive silver halide is not particularly limited as long as it reacts with an organic silver salt to form silver halide, but a silver halide containing iodine ions is preferable from the viewpoint of reactivity. Examples of the silver halide include silver bromide, silver iodide, silver chloride, silver chlorobromide, silver iodobromide, silver chloroiodide and the like.

  The organic silver salt and the photosensitive silver halide can be used in combination. In this case, the photosensitive silver halide may act catalytically on the organic silver salt. The method of bringing the photosensitive silver halide into contact with the organic silver salt is not particularly limited, but the photosensitive silver halide forming component acts on a solution or dispersion of the organic silver salt prepared in advance or a film containing the organic silver salt. And a method of converting a part of the organic silver salt to silver halide.

  0.0001-3 weight part is preferable with respect to 100 weight part of organic silver salt, and, as for the usage-amount of a reducing agent, 0.01-1 weight part is more preferable. Although it does not specifically limit as a reducing agent, According to the kind of organic silver salt to be used, it selects suitably. Examples of reducing agents include substituted phenols, bisphenols, naphthols, bisnaphthols, polyhydroxybenzenes, di- or polyhydroxynaphthols, di- or polyhydroxynaphthalenes, hydroquinones, hydroquinone monoethers, ascorbic acid Alternatively, derivatives thereof, reducing sugars, aromatic amino compounds, hydroxyamines, hydrazines, phenidones, hindered phenols and the like can be mentioned. Among these, a photodegradable or heat decomposable reducing agent is preferable, and hindered phenols are preferable. Further, a photodegradable reducing agent and a photodegradation accelerator may be used in combination, or a coating agent may be used in combination to inhibit the reaction between the organic silver salt and the reducing agent.

  The solvent used for preparing the coating solution for producing the photothermographic material is not particularly limited as long as it dissolves the vinyl acetal polymer of the present invention. Examples of the solvent include ketones such as diethyl ketone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as methyl acetate, ethyl acetate, and propyl acetate. The amount of water contained in the solvent should be as small as possible.

  To prepare a coating solution using a vinyl acetal polymer, an organic silver salt and / or a photosensitive silver halide, a reducing agent and a solvent, for example, these components are dispersed for 12 hours or more using a ball mill or the like. Thereafter, a reducing agent is added to this and further dispersed for about several hours.

As a method of applying the obtained coating liquid on the support, a conventionally known coating method is employed. Examples thereof include a method using a wire bar and a method using a blade coater. The coating amount of the coating liquid is preferably 0.1 to 5 g / m ^{2 and} more preferably 0.3 to ³ g / m ² as the silver dispersion amount in the coating film. When the application amount of the coating liquid is less than 0.1 g / m ^2, the density of the image after development may be lowered, and even if it exceeds 5 g / m ² , the density of the image after development is not improved.

  There are no particular restrictions on the support on which the coating liquid is applied, for example, polyesters such as polyethylene terephthalate and polyethylene naphthalate; carbonates such as polycarbonate; olefins such as polyethylene and polypropylene; cellulose such as cellulose triacetate and cellulose diacetate Acetals such as polyvinyl acetal; resin films such as halogen-containing polymers such as polyvinyl chloride and chlorinated polypropylene; metal plates such as aluminum; glass and paper.

  To the heat-developable photosensitive material, a color toner may be added as another additive. In order to form a black image, a black colorant is added, and in order to form a color image, a color coupler, a leuco dye, or the like is added. If necessary, a photosensitizer may be further added to the heat-developable photosensitive material.

  The vinyl acetal polymer of the present invention is a component contained in a lacquer in addition to uses such as an interlayer film for laminated glass, a binder for ceramic molding, a binder for ink or paint, and a heat-developable photosensitive material. Or a crosslinking reaction with urea-based resins, melamine-based resins, and epoxy-based resins.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following examples and comparative examples, “parts” and “%” mean weight basis unless otherwise specified.

I. Silyl group-containing vinyl alcohol polymer PVA was produced by the following method, and the degree of saponification, the content of monomer units having a silyl group, the weight average degree of polymerization, and the content of silicon atoms were determined.

[Saponification degree of PVA]
The degree of saponification of PVA was determined by the method described in JIS-K6726.

[Content of monomer unit having silyl group contained in PVA]
The vinyl ester polymer before saponification was purified by reprecipitation with hexane-acetone to completely remove the monomer having unreacted silyl groups from the polymer, followed by drying at 90 ° C. under reduced pressure for 2 days. Using a sample dissolved in a CDCl ₃ solvent as a measurement sample, the content of the monomer unit having a silyl group contained in PVA was determined using a 500 MHz proton NMR measurement apparatus (JEOL GX-500).

[Weight average polymerization degree of PVA]
A sample obtained by saponifying PVA to a saponification degree of 99.5 mol% or more was used as a sample, and a weight average molecular weight was determined by a LALLS (low angle laser light scattering photometer) method. Measurement was performed at 23 ° C. using a GPC224 type gel permeation chromatograph (Waters) connected with three TSK-gel-GMPWxL (manufactured by Tosoh Corporation) as a column. In the measurement, 0.08 M Tris buffer (pH 7.9) was used as a solvent, and an R-401 differential refractometer, 8X (Waters) was used as a detector. In order to obtain the absolute molecular weight of the sample, a KMX-6 type low angle laser light scattering photometer (Chromatix) is connected for measurement, and the weight average molecular weight obtained as a result of the measurement is expressed as a formula weight 44 of vinyl alcohol monomer units. The value obtained by dividing by was used as the weight average polymerization degree. The weight fraction of the polymer having a degree of polymerization exceeding 3 times the weight average degree of polymerization and the weight fraction of a polymer having a degree of polymerization smaller than ½ times the weight average degree of polymerization are obtained by the above measurement. Obtained from the obtained integral polymerization degree distribution.

[Content of silicon atom contained in PVA]
The content of silicon atoms contained in PVA was determined using an ICP emission analyzer IRIS AP manufactured by Jarrel Ashe according to the method described above.

PVA1a
A polymerization tank equipped with a stirrer, a temperature sensor, a chemical addition line, a polymerization liquid take-out line and a reflux condenser is charged with 2500 parts of vinyl acetate, 1656 parts of methanol, and 752 parts of a methanol solution containing 2% by weight of vinyltrimethoxysilane (VMS). After charging and replacing the system with nitrogen under stirring, the internal temperature was raised to 60 ° C. To this system, 20 parts of methanol containing 0.1 part of 2,2′-azobis (4-methoxy-2,4-dimethoxyvaleronitrile) (AMV) was added to initiate the polymerization reaction. From the start of polymerization, polymerization was carried out while adding 100 parts of a methanol solution containing 2% by weight of VMS. At the same time, a methanol solution containing 0.13% by weight of AMV was added into the system at a rate of 23 parts / hour, and a polymerization reaction was carried out for 4 hours until the solid content concentration in the system reached 25%. From the time when the concentration of solids in the system reaches 25%, vinyl acetate 625 parts / hour, methanol 414 parts / hour, methanol solution 188 parts / hour containing 2% VMS, and AMV 0.13% While the methanol solution was added to the system at a rate of 23 parts / hour, the polymerization reaction was carried out while continuously taking out the polymerization solution from the system so that the liquid level in the polymerization tank was constant. When 4 hours had elapsed from the start of addition, the polymerization solution was recovered. By introducing methanol vapor into the recovered liquid, unreacted vinyl acetate monomer was driven off to obtain a methanol solution containing 40% vinyl ester polymer. The solid content concentration in the system at the time when the polymerization solution was recovered was 25%.

  For a methanol solution containing 40% of this vinyl ester polymer, the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.02, and the solid content concentration of the vinyl ester polymer is 35 wt. %, Methanol and a methanol solution containing 10% by weight of sodium hydroxide were added in this order under stirring, and the saponification reaction was started at 40 ° C.

  Immediately after the saponification reaction has progressed, a gelled product is formed and removed from the reaction system and pulverized. Then, methyl acetate is added to the pulverized product when 1 hour has elapsed since the start of the saponification reaction. The PVA neutralized and swollen with methanol was obtained. To the PVA swollen with methanol, 6 times the amount of methanol (six times the bath ratio) of methanol was added, washed under reflux for 1 hour, and then dried at 65 ° C. for 16 hours to obtain PVA.

  The obtained PVA had a vinyltrimethylsilane unit content of 0.50 mol%, a saponification degree of 98.5 mol%, and a weight average polymerization degree of 580. The weight fraction of the polymer having a degree of polymerization exceeding 3 times the weight average degree of polymerization is 19.9% by weight, and the weight fraction of a polymer having a degree of polymerization smaller than 1/2 the weight average degree of polymerization is 9.1. % By weight. Moreover, the value of (AB) / (B) calculated | required according to the analysis method of silicon atom content contained in the above-mentioned PVA is 10.9 / 100, and pH of 4% PVA aqueous solution is 6.0. there were.

PVA2a
Except for changing the amounts of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 1, PVA2 was synthesized by the same method. Table 4 shows the results of analysis on the obtained PVA.

PVA3a
In a polymerization tank 1 equipped with a stirrer, a temperature sensor, a chemical addition line, a polymerization liquid take-out line and a reflux condenser, and a polymerization tank 2 equipped with the same equipment, 2000 parts of vinyl acetate, 2352 parts of methanol, vinyltrimethoxysilane ( After adding 600 parts of a methanol solution containing 2% by weight of VMS) and replacing the system with nitrogen under stirring, the internal temperature was raised to 60 ° C. 20 parts of a methanol solution containing 0.05 part of 2,2′-azobis (4-methoxy-2,4-dimethoxyvaleronitrile) (AMV) is added to the polymerization tank 1 and the polymerization tank 2, respectively, and the polymerization reaction is carried out. Started. Polymerization was carried out while adding 80 parts of a methanol solution containing 2% by weight of VMS at a rate of 150 parts / hour from the start of polymerization to each polymerization tank. At the same time, a methanol solution containing 0.13% by weight of AMV was added to the polymerization tank 1 and the polymerization tank 2 at a rate of 4 parts / hour, and the polymerization reaction was continued for 4 hours until the solid content in the system reached 10%. went. Thereafter, the polymerization tank 1 was charged with 500 parts / hour of vinyl acetate, 588 parts / hour of methanol, 150 parts / hour of a methanol solution containing 2% of VMS, and 4 parts / hour of a methanol solution containing 0.13% of AMV. In the polymerization tank 2, the polymerization liquid is continuously taken out from the polymerization tank 1 and fed to the polymerization tank 2 so that the liquid level in the polymerization tank becomes constant. The polymerization reaction was carried out while continuously taking out the polymerization solution so that the liquid level inside was constant. In addition, when feeding the polymerization liquid taken out from the polymerization tank 1 to the polymerization tank 2, methanol containing 0.13% of AMV was added at a rate of 8 parts / hour.

  When 4 hours have elapsed from the start of the feed, when the solid content in the polymerization tank 1 is 10% and the solid content in the polymerization tank 2 is 24%, the polymerization solution is recovered from the polymerization tank 2 and recovered. By introducing methanol vapor into the resulting liquid, unreacted vinyl acetate monomer was driven off to obtain a methanol solution containing 40% vinyl ester polymer.

  For a methanol solution containing 40% of this vinyl ester polymer, the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.02, and the solid content concentration of the vinyl ester polymer is 35 wt. %, Methanol and a methanol solution containing 10% by weight of sodium hydroxide were added in this order under stirring, and the saponification reaction was started at 40 ° C.

  Immediately after the saponification reaction has progressed, a gelled product is formed and removed from the reaction system and pulverized. Then, methyl acetate is added to the pulverized product when 1 hour has elapsed since the start of the saponification reaction. The PVA neutralized and swollen with methanol was obtained. To the PVA swollen with methanol, 6 times the amount of methanol (six times the bath ratio) of methanol was added, washed under reflux for 1 hour, and then dried at 65 ° C. for 16 hours to obtain PVA.

  The obtained PVA had a vinyltrimethylsilane content of 0.50 mol%, a saponification degree of 98.2 mol%, and a weight average polymerization degree of 590. The weight fraction of a polymer having a degree of polymerization exceeding 3 times the weight average degree of polymerization is 22.2% by weight, and the weight fraction of a polymer having a degree of polymerization smaller than 1/2 the weight average degree of polymerization is 10.2. % By weight. Moreover, the value of (AB) / (B) calculated | required according to the analysis method of silicon atom content contained in the above-mentioned PVA is 9.6 / 100, and pH of 4% PVA aqueous solution is 6.0. there were.

PVA4a
PVA3a except that the amount of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction were changed as shown in Table 2. PVA4 was synthesized by the same method. Table 4 shows the results of analysis on the obtained PVA.

PVA5a
A 6 L separable flask equipped with a stirrer, a temperature sensor, a dropping funnel and a reflux condenser was charged with 1050 parts of vinyl acetate, 2056 parts of methanol, and 394 parts of a methanol solution containing 2% by weight of vinyltrimethoxysilane. Was replaced with nitrogen, and the internal temperature was raised to 60 ° C. To this system, 20 parts of methanol containing 1.3 parts of 2,2′-azobisisobutyronitrile was added to initiate the polymerization reaction. The polymerization reaction was carried out for 4 hours while adding 30 parts of a methanol solution containing 2% by weight of vinyltrimethoxysilane to the system from the start of the polymerization, and the polymerization reaction was stopped at that time. The solid concentration in the system at the time when the polymerization reaction was stopped was 15.2%. Subsequently, methanol vapor was introduced into the system to drive off unreacted vinyl acetate monomer, thereby obtaining a methanol solution containing 40% vinyl ester polymer.

  For a methanol solution containing 40% of this vinyl ester polymer, the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.02, and the solid content concentration of the vinyl ester polymer is 35 wt. %, Methanol and a methanol solution containing 10% by weight of sodium hydroxide were added in this order under stirring, and the saponification reaction was started at 40 ° C.

  Immediately after the saponification reaction has progressed, a gelled product is formed and removed from the reaction system and pulverized. Then, methyl acetate is added to the pulverized product when 1 hour has elapsed since the start of the saponification reaction. The PVA neutralized and swollen with methanol was obtained. To the PVA swollen with methanol, 6 times the amount of methanol (six times the bath ratio) of methanol was added, washed under reflux for 1 hour, and then dried at 65 ° C. for 16 hours to obtain PVA.

  The obtained PVA had a vinyltrimethylsilane content of 0.50 mol%, a saponification degree of 98.5 mol%, and a weight average polymerization degree of 560. The weight fraction of a polymer having a degree of polymerization exceeding 3 times the weight average degree of polymerization is 19.9% by weight, and the weight fraction of a polymer having a degree of polymerization smaller than 1/2 the weight average degree of polymerization is 9.9. % By weight. Moreover, the value of (AB) / (B) calculated | required according to the analysis method of silicon atom content contained in the above-mentioned PVA is 10.9 / 100, and pH of 4% PVA aqueous solution is 6.0. there were.

PVA 6a-9a
Except for changing the amount of vinyl acetate and methanol, the type and amount of monomer having silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 3. Various PVA (PVA6a-9a) was synthesize | combined by the method similar to PVA5a. Table 4 shows the results of analysis on the obtained PVA.

PVA10a
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA10a was synthesized in the same manner as PVA1a except that the reaction was performed. Table 4 shows the results of analysis on the obtained PVA.

PVA11a
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA11a was synthesized in the same manner as PVA2a except that the reaction was performed. Table 4 shows the results of analysis on the obtained PVA.

PVA12a
PVA12a was synthesized by the same method as PVA2a except that the washing operation with methanol was omitted. Table 4 shows the results of analysis on the obtained PVA.

PVA13a
PVA13a was synthesized in the same manner as PVA2a, except that a washing operation by Soxhlet extraction using methanol was added before neutralizing the PVA obtained by the saponification reaction with methyl acetate. Table 4 shows the results of analysis on the obtained PVA.

PVA14a
PVA2a, except that instead of methyl acetate, neutralization was carried out using 5 times the number of moles of acetic acid sodium hydroxide used in the saponification reaction, followed by washing with methanol (6 times the bath ratio) at room temperature for 1 hour. PVA14a was synthesized by the same method. Table 4 shows the results of analysis on the obtained PVA.

PVA15a
PVA15a was synthesized by the same method as PVA2a except that neutralization with methyl acetate was not performed, and washing with methanol (bath ratio 6 times) was performed at room temperature for 1 hour. Table 4 shows the results of analysis on the obtained PVA.

PVA16a
PVA16a was synthesized by the same method as PVA1a except that the washing operation with methanol was omitted. Table 4 shows the results of analysis on the obtained PVA.

PVA17a
PVA17a was synthesized in the same manner as PVA1a, except that a washing operation by Soxhlet extraction using methanol was added before neutralizing the PVA obtained by the saponification reaction with methyl acetate. Table 4 shows the results of analysis on the obtained PVA.

PVA18a
PVA1a, except that instead of methyl acetate, neutralization was carried out using 5 times the molar number of acetic acid sodium salt used in the saponification reaction, followed by washing with methanol (6 times the bath ratio) at room temperature for 1 hour. PVA18a was synthesized by the same method as described above. Table 4 shows the results of analysis on the obtained PVA.

PVA19a
PVA19a was synthesized by the same method as PVA1a except that neutralization with methyl acetate was not performed, and further washing with methanol (bath ratio 6 times) was performed at room temperature for 1 hour. Table 4 shows the results of analysis on the obtained PVA.

PVA 1b and 2b
Except for changing the amounts of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 1, PVA1b and 2b were synthesized by the same method. Table 5 shows the results of analysis of the obtained PVA.

PVA 3b and 4b
PVA3a except that the amount of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction were changed as shown in Table 2. PVA3b and 4b were synthesized by the same method. Table 5 shows the results of analysis of the obtained PVA.

PVA 5b and 6b
Except for changing the amount of vinyl acetate and methanol, the type and amount of monomer having silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 3. PVA5b and 6b were synthesized by the same method as PVA5a. Table 5 shows the results of analysis of the obtained PVA.

PVA7b
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA7b was synthesized in the same manner as PVA1b except that the reaction was performed. Table 5 shows the results of analysis of the obtained PVA.

PVA8b
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA8b was synthesized in the same manner as PVA2b except that the reaction was performed. Table 5 shows the results of analysis of the obtained PVA.

II. Synthesis of vinyl acetal polymer 480 g of PVA (PVA-1a) was put into 5520 ml of water, the temperature of the solution was raised to 90 ° C. with stirring and dissolved, then cooled to 30 ° C., 20% 400 g of concentrated hydrochloric acid aqueous solution was added. Thereafter, the mixture was cooled to 14 ° C., and 267 g of butyraldehyde was added dropwise over 10 minutes to initiate the reaction. After performing the reaction at 14 ° C. for 40 minutes, the temperature was increased to 65 ° C. at a temperature increase rate of about 0.6 ° C./min, and maintained at 65 ° C. for 300 minutes. Thereafter, the reaction solution was cooled to room temperature, the precipitated particulate matter was filtered off, and this was sufficiently washed with water. The obtained product was put into a 0.3% sodium hydroxide solution and neutralized by heating to 70 ° C. Subsequently, the alkaline compound was removed by washing with water, and then the product was dried. A vinyl acetal polymer (VAP-1a) was thus obtained. When the degree of acetalization of the obtained vinyl acetal polymer was analyzed according to the method described in JIS K6728, it was 70.2 mol%.

  Various vinyl acetal polymers (VAP-2a to VAP-23a and VAP-1b to VAP-12b) were synthesized in the same manner as VAP-1a except that the reaction conditions were changed to those shown in Tables 6 to 7. did. The analytical values of each vinyl acetal polymer are shown in Tables 6 to 7.

Example 1 (Manufacture of laminated glass)
50 parts of magnesium acetate and 40 parts of triethylene glycol-di-2-ethylhexanoate were added to 100 parts of vinyl acetal polymer (VAP-2a), and roll kneading was performed at 70 ° C. for 5 minutes. Subsequently, a 0.7 mm thick plasticized film was obtained by press molding at 170 ° C. and 5 MPa. The obtained plasticized film was sandwiched between two glass plates (thickness 2.5 mm, width 300 mm, length 300 mm), put into a rubber bag, depressurized to 15 mmHg, deaerated for 15 minutes, and then 100 ° C. And after 20 minutes of vacuum pressing to perform temporary adhesion, the rubber bag was taken out. Subsequently, main bonding was carried out for 15 minutes at 130 ° C. and 1.5 MPa using an autoclave. About the laminated glass thus obtained, the whitening state of the peripheral edge of the laminated glass is evaluated by the following method, the penetration resistance is evaluated by a steel ball drop test, and further the adhesion of the plasticized film to the glass plate Sex was evaluated by the Pummel value. The evaluation results are shown in Table 8.

[State of whitening of peripheral edge of laminated glass]
The laminated glass was left in an atmosphere of 80 ° C. and 95% RH for 1 month, and then the whitening distance from the edge was measured. In addition, the whitening distance measured the distance of the part whitened continuously from the edge part of a laminated glass as whitening distance, and evaluated the state of whitening according to the following references | standards.
A: Whitening distance from the end is less than 1 mm B: Whitening distance from the end is 1 mm or more and less than 5 mm C: Whitening distance from the end is 5 mm or more

[Penetration resistance]
The edge of the laminated glass was fixed to the support frame and held horizontally, and a 2.26 kg steel ball was allowed to fall freely onto the center of the test piece. The drop height was changed in units of 0.5 m, and the maximum drop height at which penetration of the steel ball was prevented in 50% of the number of tests was measured by repeated tests at a constant height. This test was performed while maintaining the temperature of the laminated glass at three temperatures of -20 ° C, 20 ° C and 40 ° C. It means that it is excellent in penetration resistance, so that the value of fall height is large.

[Panmel value]
The laminated glass was allowed to stand at a temperature of −18 ° C. for 1 hour or longer and then smashed with a hammer having a head weight of 1 pound until the particle size of the glass became 6 mm or less. The broken glass piece was shaken off, and the degree of exposure (%) of the plasticized film was evaluated by the Pummel value according to the following criteria. The larger the Pummel value, the better the adhesion of the plasticized film to the glass plate.
Exposure level of plasticized film (%) Pummel value
100 0
90 1
85 2
60 3
40 4
20 5
10 6
5 7
2 or less 8

Examples 2-12
For laminated glass when the vinyl acetal polymer (VAP-4a, VAP-6a, VAP-7a, VAP-9a, VAP-11a to VAP-15a, VAP-22a, VAP-23a) shown in Table 6 is used. About the intermediate film, it carried out similarly to Example 1, and evaluated the whitening state of the laminated glass peripheral part, penetration resistance, and a Pummel value. The evaluation results are shown in Table 8.

Comparative Examples 1-6
Regarding the interlayer film for laminated glass in the case of using the vinyl acetal polymer (VAP-2b, VAP-4b, VAP-5b, VAP-8b, VAP-10b, VAP-12b) shown in Table 7, Example 1 and Similarly, the whitening state, penetration resistance and pummel value of the peripheral edge of the laminated glass were evaluated. The evaluation results are shown in Table 8.

  From the results shown in Table 8, the interlayer film for laminated glass using the vinyl acetal polymer of the present invention is excellent in whitening resistance, penetration resistance and adhesion to a glass plate at the edge of the laminated glass. I understand. In particular, the vinyl alcohol polymer used as a raw material satisfies the formula (I), and among the vinyl alcohol polymers, the weight fraction of the polymer having a polymerization degree exceeding 3 times the weight average polymerization degree is 25. The weight fraction of a polymer having a weight fraction of less than ½% and a degree of polymerization of less than ½ times the weight average degree of polymerization is less than 12% by weight, further satisfying formula (II), and When a vinyl acetal polymer having a degree of acetalization of 60 mol% to 80 mol% obtained by acetalizing a vinyl alcohol polymer having a pH of 4 to 8% aqueous solution (VAP-2a, VAP- 4a, VAP-6a, and VAP-7a) are excellent in balance in whitening resistance, penetration resistance and adhesion to the glass plate at the edge of the laminated glass.

  On the other hand, from the results shown in Table 8, the interlayer film for laminated glass using the vinyl acetal polymer that is outside the scope of the present invention is particularly suitable for the whitening resistance, penetration resistance, and adhesion to the glass plate at the edge of the laminated glass. It can be seen that these balances are significantly inferior.

Example 13 (Production of ceramic green sheet)
100 parts of barium titanate powder with an average particle size of 0.2 μm as ceramic powder, 10 parts of vinyl acetal polymer (VAP-1a), 3 parts of dioctyl phthalate as plasticizer, 60 parts of toluene, 60 parts of isopropanol Was mixed and pulverized with 500 parts of zirconia balls (diameter 2 mm) for 16 hours by a ball mill, and then defoamed under reduced pressure to prepare a ceramic slurry. The ceramic slurry was applied on a polyethylene terephthalate film (PET film) for release by a doctor blade method, dried at 105 ° C. for 5 minutes, and then released from the PET film to obtain a ceramic green sheet having a thickness of 5 μm. .

  About the obtained ceramic green sheet, the surface state was evaluated by the following method, and the strength was further measured by the following method. Table 9 shows the evaluation results and the measurement results.

[Ceramic green sheet surface condition]
Using an optical microscope, the state of the surface of the ceramic green sheet was observed and evaluated according to the following criteria.
A: There is no unevenness due to voids or aggregated particles, and it is homogeneous.
B: Although there is no void, unevenness due to a very small amount of aggregated particles is observed.
C: Both voids and irregularities due to aggregated particles are observed.

[Strength of ceramic green sheet]
A ceramic green sheet was punched into 40 mm × 100 mm, and the toughness of the green sheet was measured with an autograph DCS-100 manufactured by Shimadzu (chuck interval: 30 mm, tensile speed: 10 mm / min., Measurement temperature 20 ° C.). In addition, the ratio (times) when the average value which measured 5 times about one sample was made into the toughness value (kgf * mm), and the toughness value (kgf * mm) obtained in the comparative example 7 was set to 1.0 Asked.

Examples 14-23
Regarding ceramic green sheet when vinyl acetal polymer (VAP-3a, VAP-5a, VAP-8a, VAP-10a, VAP-16a to VAP-21a) shown in Table 6 is used as a ceramic molding binder In the same manner as in Example 13, the surface state of the ceramic green sheet was evaluated, and the strength of the ceramic green sheet was measured. Table 9 shows the evaluation results and the measurement results.

Comparative Examples 7-12
For the ceramic green sheet when the vinyl acetal polymer (VAP-1b, VAP-3b, VAP-6b, VAP-7b, VAP-9b, VAP-11b) shown in Table 7 is used as a ceramic molding binder In the same manner as in Example 13, the surface state of the ceramic green sheet was evaluated, and the strength of the ceramic green sheet was measured. Table 9 shows the evaluation results and the measurement results.

  From the results shown in Table 9, the ceramic green sheet obtained when the vinyl acetal polymer of the present invention is used as a binder for ceramic molding has a good sheet surface state and is excellent in terms of sheet strength. I understand that

  In particular, the vinyl alcohol polymer used as a raw material satisfies the formula (I), and among the vinyl alcohol polymers, the weight fraction of the polymer having a polymerization degree exceeding 3 times the weight average polymerization degree is 25. The weight fraction of a polymer having a weight fraction of less than ½% and a degree of polymerization of less than ½ times the weight average degree of polymerization is less than 12% by weight, further satisfying formula (II), and When a vinyl acetal polymer having a degree of acetalization of 60 mol% to 80 mol% obtained by acetalizing a vinyl alcohol polymer having a pH of 4 to 8% aqueous solution is used (VAP-1a, VAP- 3a and VAP-5a) are significantly superior in the state of the surface of the ceramic green sheet and the strength of the ceramic green sheet.

  On the other hand, from the results shown in Table 9, the interlayer film for laminated glass using the vinyl acetal polymer outside the scope of the present invention used the vinyl acetal polymer outside the scope of the present invention as a binder for ceramic molding. It can be seen that the ceramic green sheet obtained in this case is particularly inferior in the balance between the surface state of the ceramic green sheet and its strength.

Example 24 (Preparation of pigment dispersion)
After preparing ethanol solutions of several types of vinyl acetal polymers (VAP-1a) with different solid content concentrations, and measuring the outflow time of these solutions with a DIN 4 mm cup (DIN 53211/23 ° C.), the outflow time was 20 seconds. 400 g of an ethanol solution of a vinyl acetal polymer (VAP-1a) having a controlled concentration was prepared. To this ethanol solution, 100 g of pigment (Hostaperm Blue B 2G) was added, and the mixture was homogenized and kneaded with glass beads for 30 minutes while cooling to prepare a pigment dispersion. For the obtained pigment dispersion, the viscosity of the pigment dispersion and the amount of pigment that can be contained in the pigment dispersion were measured by the following methods. Table 10 shows the measurement results.

[Viscosity of pigment dispersion: Cup outflow time]
Using a sieve, the pigment dispersion mill base was separated from the beads, and the outflow time was measured with a DIN 6 mm cup (DIN 53211/23 ° C.).

[Pigment content in pigment dispersion]
The pigment dispersion used for measuring the cup outflow time was diluted with ethanol so that its Heppler viscosity at 23 ° C. was 10 mPa · s, and the pigment content contained in the solution was calculated. In addition, pigment content was shown by the ratio (times) when the pigment content measured in the comparative example 13 was set to 1.0.

Examples 25-34
About the pigment dispersion obtained using the vinyl acetal polymer (VAP-3a, VAP-5a, VAP-8a, VAP-10a, VAP-16a to VAP-21a) shown in Table 6, the same as in Example 24 The viscosity of the pigment dispersion and the amount of pigment that can be contained in the pigment dispersion were measured. Table 10 shows the measurement results. In addition, pigment content was shown by the ratio (times) when the pigment content measured in the comparative example 13 was set to 1.0.

Comparative Examples 13-18
The pigment dispersion obtained using the vinyl acetal polymer (VAP-1b, VAP-3b, VAP-6b, VAP-7b, VAP-9b, VAP-11b) shown in Table 7 was used in the same manner as in Example 24. The viscosity of the pigment dispersion and the amount of pigment that can be contained in the pigment dispersion were measured. Table 10 shows the measurement results. In addition, pigment content was shown by the ratio (times) when the pigment content measured in the comparative example 13 was set to 1.0.

  From the results shown in Table 10, when the vinyl acetal polymer of the present invention is used as a binder for inks and paints, it is excellent in that a high concentration and low viscosity can be achieved from the results of outflow time and pigment content. I understand that. In particular, the vinyl alcohol polymer used as a raw material satisfies the formula (I), and among the vinyl alcohol polymers, the weight fraction of the polymer having a polymerization degree exceeding 3 times the weight average polymerization degree is 25. The weight fraction of a polymer having a weight fraction of less than ½% and a degree of polymerization of less than ½ times the weight average degree of polymerization is less than 12% by weight, further satisfying formula (II), and When a vinyl acetal polymer having a degree of acetalization of 60 mol% to 80 mol% obtained by acetalizing a vinyl alcohol polymer having a pH of 4 to 8% aqueous solution is used (VAP-1a, VAP- 3a, VAP-5a, VAP-10a) are significantly superior in these respects.

  On the other hand, it can be seen from the results shown in Table 9 that when a vinyl acetal polymer made from a vinyl alcohol polymer outside the scope of the present invention is used, these points are inferior.

Example 35 (Preparation of coating solution for heat-developable photosensitive material)
10 parts by weight of vinyl acetal polymer (VAP-1a), 11 parts by weight of silver behenate and 85 parts by weight of methyl isobutyl ketone were mixed at room temperature for 12 hours using a ball mill, and then N-lauryl-1-hydroxy-2- 0.5 parts by weight of naphthamide was added and mixed again at room temperature for 12 hours using a ball mill to obtain a coating solution.

  About the obtained coating liquid, the storage stability was evaluated by the following method. Moreover, the heat developability and the image stability after development of the heat-developable photosensitive material obtained using the coating solution were evaluated by the following methods. The evaluation results are shown in Table 11.

[Storage stability of coating liquid]
The coating solution was allowed to stand indoors under fluorescent light irradiation at 25 ° C. for 1 week, and the degree of coloring was visually evaluated according to the following criteria.
A: No change B: Very slight change but almost no problem C: Coloring is observed

[Heat developability]
Using a blade coater, the coating solution was applied onto polyethylene terephthalate so that the coating thickness after drying was 8 μm and dried, and 0.4 parts by weight of N, N-dimethyl-p-phenyleneamine / lead sulfate Then, a solution comprising 2 parts by weight of polyvinylpyrrolidone and 30 parts by weight of methanol was applied in the same manner so that the coating thickness after drying was 1.5 μm and dried to obtain a photothermographic material.

Using the resulting photothermographic material, a 250-watt high-pressure mercury lamp was exposed from a distance of 25 cm through a gradation pattern film for 0.5 mm second, and then contacted with a metal plate heated to 125 ° C. for 4 seconds for development. did. The thermal developability was visually evaluated according to the following criteria.
A: No fogging and high sharpness B: Slight fogging is observed, but sharpness is relatively good C: Fog is recognized and sharpness is inferior

[Image stability after development]
When the obtained developed image was exposed to a white light for 1 week, the stability of the image was visually evaluated according to the following criteria.
A: Image pattern contrast is not disturbed B: Image pattern contrast is slightly disturbed but relatively good C: Image pattern contrast is disturbed

Examples 36-45
Using the vinyl acetal polymer (VAP-3a, VAP-5a, VAP-8a, VAP-10a, VAP-16a to VAP-21a) shown in Table 6 in the same manner as in Example 35, preservation of the coating solution Stability, heat developability of the heat developable photosensitive material and image stability after development were evaluated by the following methods. The evaluation results are shown in Table 11.

Comparative Examples 19-24
Using vinyl acetal polymers (VAP-1b, VAP-3b, VAP-6b, VAP-7b, VAP-9b, VAP-11b) shown in Table 7 and Table 18, in the same manner as in Example 35, coating The storage stability of the solution, the heat developability of the heat-developable photosensitive material and the image stability after development were evaluated by the following methods. The evaluation results are shown in Table 11.

  From the results shown in Table 11, when the vinyl acetal polymer of the present invention is used as a heat developable photosensitive material, the storage stability of the coating solution, the heat developability of the heat developable photosensitive material, and the image stability after development. It turns out that it is excellent in terms of sex. In particular, the vinyl alcohol polymer used as a raw material satisfies the formula (I), and among the vinyl alcohol polymers, the weight fraction of the polymer having a polymerization degree exceeding 3 times the weight average polymerization degree is 25. The weight fraction of a polymer having a weight fraction of less than ½% and a degree of polymerization of less than ½ times the weight average degree of polymerization is less than 12% by weight, further satisfying formula (II), and When a vinyl acetal polymer having a degree of acetalization of 60 mol% to 80 mol% obtained by acetalizing a vinyl alcohol polymer having a pH of 4 to 8% aqueous solution is used (VAP-1a, VAP- 3a, VAP-5a, VAP-10a) are significantly superior in these respects.

  On the other hand, it can be seen from the results shown in Table 9 that when a vinyl acetal polymer made from a vinyl alcohol polymer outside the scope of the present invention is used, these points are inferior.

  As described above, the vinyl acetal polymer of the present invention is remarkably superior in performance in each application as compared with the conventional vinyl acetal polymer.

  The laminated glass obtained by using the interlayer film for laminated glass obtained by using the vinyl acetal polymer of the present invention is excellent in the whitening resistance of the end portion, the penetration resistance, and the adhesion to the laminated glass.

  When the vinyl acetal polymer of the present invention is used as a ceramic molding binder, a ceramic green sheet having a good surface condition and excellent strength can be produced.

  When the vinyl acetal polymer of the present invention is used as a binder for ink or paint, the ink or paint has a low solution viscosity, a high solid content ratio (high pigment content), and sufficient ink dispersibility. Can be manufactured. The ink or paint obtained in this way has a high pigment content at a desired viscosity and the color strength is high even when the thickness of the coating film formed by printing is thin. Since it has excellent features such as large size, it can be suitably used for a printing machine that operates at high speed.

  The heat-developable photosensitive material obtained using the vinyl acetal polymer of the present invention is excellent in heat-developability and image stability after development, and is a coating solution prepared in the production of the heat-developable photosensitive material. Is excellent in storage stability.

Claims (11)

The following general formula (1)

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl acetal polymer having a degree of acetalization of 45 to 80 mol% obtained by acetalizing a vinyl alcohol polymer obtained by saponifying a vinyl ester polymer containing a monomer unit having a silyl group represented by A weight fraction of a polymer that satisfies the following formula (I) and whose degree of polymerization exceeds three times the weight average degree of polymerization in the vinyl alcohol polymer: Is a vinyl acetal polymer, characterized in that it is 25% by weight or less.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%) 2. The vinyl acetal polymer according to claim 1, wherein, in the vinyl alcohol polymer, a weight fraction of a polymer having a degree of polymerization smaller than ½ times a weight average degree of polymerization is 12% by weight or less. The vinyl acetal polymer according to claim 1 or 2, wherein the vinyl alcohol polymer satisfies the following formula (II), and the pH of a 4% aqueous solution thereof is 4-8.
0.1 / 100 ≦ (A−B) / (B) ≦ 50/100 (II)
A: Content of silicon atom in vinyl alcohol polymer (unit: ppm)
B: Content of silicon atom in vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed with Soxhlet extraction with methanol (unit: ppm)
Here, A and B are measured by ICP emission spectrometry after ashing the measurement sample. The vinyl acetal polymer according to any one of claims 1 to 3, wherein the aldehyde used for the acetalization is at least one selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, and benzaldehyde. . The vinyl acetal polymer according to claim 4, wherein the aldehyde used for the acetalization is butyraldehyde. The following general formula (1)

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl ester polymer containing a monomer unit having a silyl group represented by saponification is obtained to obtain a vinyl alcohol polymer, and then the vinyl alcohol polymer is acetalized. A method for producing an 80 mol% vinyl acetal polymer, wherein the vinyl alcohol polymer satisfies the following formula (I), and the degree of polymerization of the vinyl alcohol polymer is a weight average degree of polymerization: A method for producing a vinyl acetal polymer, wherein the polymer has a weight fraction of 25% by weight or less.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%) An interlayer film for laminated glass comprising the vinyl acetal polymer according to any one of claims 1 to 5. A laminated glass having the interlayer film for laminated glass according to claim 7. A ceramic molding binder comprising the vinyl acetal polymer according to any one of claims 1 to 5. A binder for ink or paint comprising the vinyl acetal polymer according to any one of claims 1 to 5. A heat-developable photosensitive material containing the vinyl acetal polymer according to claim 1.