JP6445774B2 - Modified polyvinyl acetal resin - Google Patents

Description

The present invention provides a modified polyvinyl acetal resin having excellent flexibility and heat resistance. Moreover, this invention provides the modified polyvinyl acetal resin which is excellent also in adhesiveness and storage stability.

The polyvinyl acetal resin is generally obtained by acetalizing polyvinyl alcohol obtained by saponifying a polyvinyl ester. The polyvinyl acetal resin has a structural unit obtained by acetalizing a structural unit derived from an adjacent vinyl alcohol with an aldehyde compound, a structural unit derived from vinyl alcohol, and a structural unit having an acetyl group that is an unsaponified portion. It is a polymer.

Polyvinyl acetal resin has excellent toughness, dispersibility in inorganic or organic powders, adhesion to various materials, transparency, and is soluble in many organic solvents. Paint such as paint, printing ink such as flexo ink or gravure ink, printed circuit board, varnish for coil wire, adhesive, ceramic binder, binder such as magnetic tape, coating material such as inkjet media or textile printing, automobile or building It is used in various applications such as an interlayer film for laminated glass used in the industry.

However, the polyvinyl acetal resin has insufficient heat stability, and when used for molding, there is a problem that it causes generation of decomposition gas and generation of a crosslinked gelled product.
In order to improve heat resistance, Patent Document 1 discloses a polyvinyl acetal resin in which the ratio of the amount of acetoacetal groups to the amount of butyral groups is 100: 0 to 10:90.
However, the polyvinyl acetal resin described in Patent Document 1 has a problem that durability at a high temperature is still insufficient, and adhesion to a resin such as PET or polyimide, or a metal foil such as a copper foil is low. .

Patent Document 2 discloses a polyvinyl alcohol-based resin composition in which deterioration due to heat treatment is suppressed and thermal stability is improved by adding a triazole-based compound.
However, the polyvinyl alcohol-based resin composition described in Patent Document 2 has a problem that the amount of hydroxyl groups is large and the flexibility of the coating film is remarkably lowered, so that the processability is lowered and the hygroscopic property of the resin is high and not suitable for long-term storage. there were.

International Publication No. 2012/043455 Pamphlet JP 2001-19819 A

An object of the present invention is to provide a modified polyvinyl acetal resin having excellent flexibility and heat resistance. Another object of the present invention is to provide a modified polyvinyl acetal resin that is also excellent in adhesiveness and storage stability.

The present invention includes a structural unit having a hydroxyl group represented by the following formula (1), a structural unit having an acetyl group represented by the following formula (2), and a structural unit having an acetal group represented by the following formula (3). And the structural unit represented by the following formula (4), the structural unit represented by the following formula (4) has a structure represented by the following formula (5), and is represented by the formula (1). the content of the repeating unit having that hydroxyl group is modified polyvinyl acetal resin is 25-4 0 mol%.

In the formula (3), ^{R 1} is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. In formula (4), R ² represents a single bond, an alkylene group or an arylene group. R ³ represents a group having a lactam ring represented by the formula (5) which may be substituted. In formula (5), X and Y each represent a single bond bonded to R ^2, and when other than a single bond, an alkyl group, a hydroxy group, a carboxyl group, an amino group, a cyano group, a nitro group, carbonyl group, an amide group, an imino group, a substituent having at least one selected from the group consisting of azo group and an ether bond, or to display the hydrogen atom, n is an integer of 0-5. However, the case where n is 3 is excluded.

As a result of intensive studies, the present inventors have found that having a specific structure can improve the flexibility and heat resistance of the polyvinyl acetal resin, and can also improve the adhesiveness and storage stability, thereby completing the present invention. I came to let you.

The modified polyvinyl acetal resin of the present invention includes a structural unit having a hydroxyl group represented by the above formula (1), a structural unit having an acetyl group represented by the above formula (2), and an acetal represented by the above formula (3). It has a structural unit having a group.
The modified polyvinyl acetal resin of the present invention can have water resistance and sheet flexibility by having these structural units.

In the modified polyvinyl acetal resin of the present invention, the content of the structural unit having a hydroxyl group represented by the above formula (1) (hereinafter also referred to as a hydroxyl group amount) is preferably 40 mol% or less.
When the amount of the hydroxyl group exceeds 40 mol%, the hygroscopicity becomes high and long-term storage becomes difficult, and a step of drying before use is necessary. In particular, in applications such as coverlays, the adhesive surface may swell due to the influence of moisture absorbed in the resin, which may cause poor contact.
A more preferable upper limit of the hydroxyl group content is 35 mol%, and a more preferable upper limit is 30 mol%.

The modified polyvinyl acetal resin of the present invention has a preferable lower limit of 0.01 mol% and a preferable upper limit of the content of the structural unit having an acetyl group represented by the above formula (2) (hereinafter also referred to as acetyl group amount). 15 mol%.
If the amount of acetyl groups is less than 0.01 mol%, the hydrogen bonding strength becomes strong, so that the resin solution has a high viscosity, and if it exceeds 15 mol%, the hydrophilicity becomes low, so it is difficult to synthesize in water. .
The minimum with said more preferable amount of acetyl groups is 0.1 mol%, and a more preferable upper limit is 10 mol%.

In the formula (3), ^{R 1} is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

In the above formula (3), when R ¹ is an alkyl group having 1 to 20 carbon atoms, examples of the alkyl group include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso -Butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group , Pentadecyl group, octadecyl group and the like. Of these, a methyl group and an n-propyl group are preferable.

In the modified polyvinyl acetal resin of the present invention, the preferable lower limit of the content of the structural unit having an acetal group represented by the above formula (3) (hereinafter also referred to as acetalization degree) is 60 mol%.
If the degree of acetalization is less than 60 mol%, the hygroscopicity becomes high and long-term storage becomes difficult, and a step of drying before use is required.
A more preferable lower limit of the degree of acetalization is 65 mol%.
In this specification, as a method for calculating the degree of acetalization, since the acetal group of the modified polyvinyl acetal resin is acetalized from two hydroxyl groups, the two acetalized hydroxyl groups are counted. The method is employed to calculate the mole percent of the degree of acetalization.

The modified polyvinyl acetal resin of the present invention has a structural unit represented by the above formula (4), and the structural unit represented by the above formula (4) has a structure represented by the above formula (5).
The modified polyvinyl acetal resin of the present invention can exhibit excellent heat resistance and flexibility by having the structural unit represented by the above formula (4), and to various substrates such as polyimide and copper foil. It is also possible to impart improved adhesion and compatibility with other resins.

In the formula (4), R ² represents a single bond, an alkylene group or an arylene group.
In the formula (4), and R ² is a single bond, those in which carbon atoms and R ³ in the main chain directly bonded.

In the formula (4), when R ² is an alkylene group, a preferred upper limit of the number of carbon atoms within the alkylene group is 20. When the number of carbon atoms of the alkylene group exceeds 20, the resin composition approaches hydrophobicity, so that it is difficult to synthesize an acetal resin that is difficult to dissolve in water.
When R ² is an alkylene group, the upper limit of the carbon number of the alkylene group is more preferably 15.

In the above formula (4), when R ² is an alkylene group, examples of the alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a pentamethylene group, a hexamethylene group, and an octamethylene group. Group, linear alkylene group such as decamethylene group, branched alkylene group such as methylmethylene group, methylethylene group, 1-methylpentylene group, 1,4-dimethylbutylene group, cyclopropylene group, cyclobutylene group, cyclohexyl And cyclic alkylene groups such as a silene group. Especially, since there are few steric hindrances, a methylene group, ethylene group, n-propylene group, n-, from the viewpoint that the reactivity with an aldehyde is high and a resin with a high degree of acetalization that can suppress hygroscopicity can be synthesized. A linear alkylene group such as a butylene group is preferred, and a methylene group and an ethylene group are more preferred.

In the formula (4), when R ² is an arylene group, preferred upper limit of the carbon number of the arylene group is 20. When the number of carbon atoms of the arylene group exceeds 20, the resin composition approaches hydrophobicity, and it is difficult to synthesize an acetal resin that is difficult to dissolve in water.
When R ² is an arylene group, the upper limit of the carbon number of the arylene group is more preferably 15.

In the above formula (4), when R ² is an arylene group, as the arylene group, for example, an aromatic hydrocarbon ring optionally having a substituent such as benzene, naphthalene, anthracene, fluorene, phenanthrene, Two hydrogen atoms are removed from a heteroaromatic hydrocarbon ring which may have a substituent such as thiophene, furan, pyrrole, benzothiophene, benzofuran, benzopyrrole, triazine, imidazole, benzimidazole, triazole, thiadiazole, thiazole, etc. And the like groups. Among them, a group formed by removing two hydrogen atoms from an aromatic hydrocarbon ring is preferable from the viewpoint of high reactivity with aldehydes and increasing the degree of acetalization, and since there are few steric hindrances, A group formed by removing a hydrogen atom is more preferable.

In said formula (4), R < ³ > represents group which has the lactam ring represented by the formula (5) which may be substituted. In formula (5), X and Y each represent a single bond bonded to R ^2, and when other than a single bond, an alkyl group, a hydroxy group, a carboxyl group, an amino group, a cyano group, a nitro group, It represents a substituent having at least one selected from the group consisting of a carbonyl group, an amide group, an imino group, an azo group and an ether bond, or a hydrogen atom. Of these, Y is preferably a single bond. By having a structure in which Y is a single bond and the nitrogen atom of the lactam ring is bonded to R ² , the crystallinity of the resin is increased, and when the sheet is formed, the strength is high. Moreover, when X and Y are other than a single bond, a hydrogen atom, an alkyl group, a hydroxy group, a carboxyl group, or an amino group is preferable, and a hydrogen atom or a hydroxy group is more preferable.
In the formula (5), the any one of the X is a single bond to bond to R ^2, and bonded to any one R ² of the carbon atoms constituting a lactam ring, a lactam The remaining carbon atoms constituting the ring are bonded to a hydrogen atom or a substituent, and Y is a single bond. The nitrogen atom forming the lactam ring and R ² are bonded to each other. It represents that the carbon atom which comprises is couple | bonded with the hydrogen atom or the substituent.
Moreover, when X and Y are other than a single bond, they may be the same or different.

In the above formula (4), when R ³ is a substituted group having a lactam ring represented by the above formula (5), examples of the substituent are the same as those exemplified for X and Y. Can be mentioned.

In said formula (5), n represents the integer of 0-5. That is, the group having a lactam ring represented by the above formula (5) is a group having a 4 to 9-membered lactam structure, and when n is 0, it represents a group having a 4-membered lactam structure. In the above formula (5), when n exceeds 5, the steric hindrance increases and the reactivity with aldehyde decreases. In the above formula (5), the preferable lower limit of n is 1, the preferable upper limit is 4, and the more preferable upper limit is 3.

Examples of the group having a lactam ring represented by the above formula (5) include groups having a β-lactam structure, a γ-lactam structure, a δ-lactam structure, an ε-lactam structure, and the like. The group having a γ-lactam structure is preferable from the viewpoint that both the reactivity with the resin and the flexibility of the resin are compatible.

In the modified polyvinyl acetal resin of the present invention, the content of the structural unit represented by the above formula (4) (hereinafter also referred to as the degree of modification) is preferably 30 mol% or less.
If the degree of modification exceeds 30 mol%, the reactivity at the time of synthesizing the polyvinyl acetal resin is remarkably lowered, the resin strength is increased, and the flexibility of the modified polyvinyl acetal resin may be lowered.
A more preferable upper limit of the degree of modification of the modified polyvinyl acetal resin of the present invention is 20 mol%, and a more preferable upper limit is 15 mol%.

The modified polyvinyl acetal resin of the present invention has a preferable lower limit of the average degree of polymerization of 150 and a preferable upper limit of 4500.
When the average degree of polymerization is less than 150, the strength of the coated film is remarkably reduced, making it difficult to handle. When the average degree of polymerization exceeds 4,500, the viscosity of the resin solution increases, so the manufacturing process time is increased and the amount of undissolved resin is increased. There is a possibility that defects will occur in the final product.
The more preferable lower limit of the average degree of polymerization of the modified polyvinyl acetal resin of the present invention is 300, and the more preferable upper limit is 3500.

As a method for synthesizing the modified polyvinyl acetal resin of the present invention, for example, polyvinyl acetate obtained by copolymerizing a monomer that is a structural unit represented by the above formula (4) and vinyl acetate is used. A method of acetalizing the saponified polyvinyl alcohol resin by a conventionally known method is exemplified. Further, a modified polyvinyl alcohol resin obtained by post-modification by reacting a compound having a lactam structure such as ε-caprolactam with a polyvinyl alcohol resin may be acetalized by a conventionally known method, or a lactam such as ε-caprolactam. A compound having a structure and an unmodified polyvinyl acetal resin may be heated and mixed at 100 ° C. in a nitrogen atmosphere, and then stannous chloride (SnCl ₂ ) may be added, followed by further heating and reaction for post-modification. .

Examples of the monomer serving as the structural unit represented by the above formula (4) include monomers having a vinyl group and a lactam structure such as vinyl lactam such as vinyl pyrrolidone, vinyl caprolactam, and vinyl piperidone. Of these, vinylpyrrolidone is preferably used.

It does not specifically limit as said acetalization reaction, It can carry out by a conventionally well-known method. For example, a method in which various aldehydes are added to an aqueous solution of polyvinyl alcohol, an alcohol solution, a water / alcohol mixed solution, or a dimethyl sulfoxide (DMSO) solution in the presence of an acid catalyst.

The aldehyde used in the acetalization reaction is not particularly limited. For example, formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde and the like. Among these aldehydes, it is preferable to use butyraldehyde alone or a combination of acetaldehyde and butyraldehyde.

The acid catalyst is not particularly limited, and either an organic acid or an inorganic acid can be used. Examples thereof include acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid, and hydrochloric acid.

In order to stop the acetalization reaction, neutralization with an alkali is preferably performed. It does not specifically limit as said alkali, For example, sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate etc. are mentioned.
Moreover, it is preferable to wash | clean the modified polyvinyl acetal resin obtained using water etc. before and after the said neutralization process. In order to prevent impurities contained in the cleaning water from being mixed, it is more preferable to perform the cleaning with pure water.

The modified polyvinyl acetal resin of the present invention can be suitably used for applications in which ordinary polyvinyl acetal resins are used. For example, ceramic molded bodies, metal pastes, heat-developable photosensitive materials, paints, inks, adhesives, A coating solution for producing a reflective sheet or the like can be obtained.

According to the present invention, a modified polyvinyl acetal resin having excellent flexibility and heat resistance can be provided. Moreover, according to this invention, the modified polyvinyl acetal resin which is excellent also in adhesiveness and storage stability can be provided.

Examples of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
As a raw material polyvinyl alcohol, polyvinyl alcohol A (average polymerization degree 2000, saponification degree 99 mol%, modification degree 1 mol%) having a structural unit represented by the following formula (6) was used.

In the reactor, 193 g of the polyvinyl alcohol A and 2900 g of pure water were added and stirred at 90 ° C. for 2 hours to completely dissolve the polyvinyl alcohol A. Thereafter, it is cooled to 40 ° C., 20 g of hydrochloric acid having a concentration of 35% by weight is added as a catalyst, then 115 g of acetaldehyde is added, the liquid temperature is cooled to 15 ° C., this temperature is maintained, and an acetalization reaction is performed. The product precipitated out. Thereafter, the liquid temperature was set to 40 ° C. and held for 3 hours to complete the reaction, neutralized with sodium hydrogen carbonate, the acetalization reaction was stopped, washed with water, and then dried to obtain a white color of the modified polyvinyl acetal resin A. A powder was obtained.

^When the composition of the obtained modified polyvinyl acetal resin A was measured using ¹ H-NMR spectrum, the amount of hydroxyl group was 25 mol%, the amount of acetyl group was 1 mol%, the degree of acetalization was 73 mol%, and the modification The degree was 1 mol%, and it was confirmed that the lactam ring was not opened. R ¹ in the above formula (3) was a methyl group.
Moreover, the average degree of polymerization of the obtained modified polyvinyl acetal resin A was 2000.

(Example 2)
Example 1 except that polyvinyl alcohol B (average polymerization degree 1000, saponification degree 99 mol%, modification degree 4 mol%) having the structural unit represented by the above formula (6) was used as the raw material polyvinyl alcohol. Similarly, white powder of modified polyvinyl acetal resin B was obtained.

^When the composition of the obtained modified polyvinyl acetal resin B was measured using ¹ H-NMR spectrum, the amount of hydroxyl group was 25 mol%, the amount of acetyl group was 1 mol%, the degree of acetalization was 70 mol%, and the modification The degree was 4 mol%, and it was confirmed that the lactam ring was not opened. R ¹ in the above formula (3) was a methyl group.
The average degree of polymerization of the obtained modified polyvinyl acetal resin B was 1000.

Example 3
Example 1 except that polyvinyl alcohol C (average polymerization degree 500, saponification degree 99 mol%, modification degree 30 mol%) having the structural unit represented by the above formula (6) was used as the raw material polyvinyl alcohol. Similarly, white powder of modified polyvinyl acetal resin C was obtained.

^When the composition of the obtained modified polyvinyl acetal resin C was measured using ¹ H-NMR spectrum, the amount of hydroxyl group was 25 mol%, the amount of acetyl group was 1 mol%, the degree of acetalization was 44 mol%, and the modification The degree was 30 mol%, and it was confirmed that the lactam ring was not opened. R ¹ in the above formula (3) was a methyl group.
Moreover, the average degree of polymerization of the obtained modified polyvinyl acetal resin C was 500.

(Example 4)
Example 1 except that polyvinyl alcohol D (average polymerization degree 1000, saponification degree 99 mol%, modification degree 4 mol%) having a structural unit represented by the following formula (7) was used as the raw material polyvinyl alcohol. Similarly, white powder of modified polyvinyl acetal resin D was obtained.

^When the composition of the obtained modified polyvinyl acetal resin D was measured using ¹ H-NMR spectrum, the amount of hydroxyl group was 25 mol%, the amount of acetyl group was 1 mol%, the degree of acetalization was 70 mol%, and the modification The degree was 4 mol%, and it was confirmed that the lactam ring was not opened. R ¹ in the above formula (3) was a methyl group.
Moreover, the average degree of polymerization of the obtained modified polyvinyl acetal resin D was 1000.

(Example 5)
Example 1 except that polyvinyl alcohol E (average polymerization degree 1000, saponification degree 99 mol%, modification degree 4 mol%) having a structural unit represented by the following formula (8) was used as the raw material polyvinyl alcohol. Similarly, white powder of modified polyvinyl acetal resin E was obtained.

^When the composition of the obtained modified polyvinyl acetal resin E was measured using ¹ H-NMR spectrum, the amount of hydroxyl group was 25 mol%, the amount of acetyl group was 1 mol%, the degree of acetalization was 70 mol%, and the modification The degree was 4 mol%, and it was confirmed that the lactam ring was not opened. R ¹ in the above formula (3) was a methyl group.
Moreover, the average degree of polymerization of the obtained modified polyvinyl acetal resin E was 1000.

( Reference Example 6)
Except for using polyvinyl alcohol F (average polymerization degree 1000, saponification degree 99 mol%, modification degree 4 mol%) having the structural unit represented by the above formula (6) as a raw material polyvinyl alcohol, and adding 100 g of acetaldehyde. In the same manner as in Example 1, a white powder of the modified polyvinyl acetal resin F was obtained.

^When the composition of the obtained modified polyvinyl acetal resin F was measured using ¹ H-NMR spectrum, the amount of hydroxyl group was 45 mol%, the amount of acetyl group was 1 mol%, the degree of acetalization was 50 mol%, and the modification The degree was 4 mol%, and it was confirmed that the lactam ring was not opened. R ¹ in the above formula (3) was a methyl group.
Moreover, the average degree of polymerization of the obtained modified polyvinyl acetal resin F was 1000.

(Comparative Example 1)
A white powder of polyvinyl acetal resin G was obtained in the same manner as in Example 1 except that unmodified polyvinyl alcohol G (average polymerization degree 1000, saponification degree 99 mol%) was used as the raw material polyvinyl alcohol.

^When the composition of the obtained polyvinyl acetal resin G was measured using ¹ H-NMR spectrum, it was confirmed that the amount of hydroxyl groups was 25 mol%, the amount of acetyl groups was 1 mol%, and the degree of acetalization was 74 mol%. did. R ¹ in the above formula (3) was a methyl group.
Moreover, the average degree of polymerization of the obtained polyvinyl acetal resin G was 1000.

(Comparative Example 2)
The same as Example 1 except that polyvinyl alcohol H (average polymerization degree 1000, saponification degree 99 mol%, modification degree 4 mol%) having a structural unit represented by the following formula (9) was used as the raw material polyvinyl alcohol. Thus, a white powder of the modified polyvinyl acetal resin H was obtained.

^When the composition of the obtained modified polyvinyl acetal resin H was measured using ¹ H-NMR spectrum, the amount of hydroxyl group was 25 mol%, the amount of acetyl group was 1 mol%, the degree of acetalization was 70 mol%, and the modification The degree was 4 mol%, and it was confirmed that the lactam ring was not opened. R ¹ in the above formula (3) was a methyl group.
The average degree of polymerization of the obtained modified polyvinyl acetal resin H was 1000.

<Evaluation>
The polyvinyl acetal resins A to H obtained in Examples 1 to 5, Reference Example 6 and Comparative Examples 1 to 2 were evaluated by the following methods. The results are shown in Table 1.

(1) Mechanical strength White powders of polyvinyl acetal resins A to H obtained in Examples 1 to 5, Reference Example 6 and Comparative Examples 1 to 2 were dissolved in an ethanol / toluene mixed solvent (mixing ratio 1: 1). Each solution was coated using a coater so that the thickness after drying was 20 μm, and then dried to obtain a resin sheet having a width of 1 cm and a length of 5 cm.
The obtained resin sheet was stretched under the condition of a tensile speed of 20 mm / min using AUTOGRAPH (AGS-J, manufactured by Shimadzu Corporation) by a method based on JIS K 7113, and the tensile modulus and the upper yield stress. The strain at break was measured. The measurement was performed using a thermostatic bath, and the tensile modulus at 25 ° C., 50 ° C., and 80 ° C., the upper yield stress, and the strain at break were measured.

(2) Resin film heat resistance The rate of change of the tensile modulus of the resin sheet obtained in “Evaluation (1) Mechanical Strength” between room temperature (25 ° C.) and 80 ° C. heating (tensile elasticity at 25 ° C. Ratio × tensile elastic modulus at 100/80 ° C.). The heat resistance was evaluated by assuming that the change rate of the tensile elastic modulus was 1000% or less, and that the change rate of the elastic modulus greater than 1000% was x.

(3) Adhesive evaluation The resin sheet obtained by “evaluation (1) mechanical strength” was obtained by using copper foil (Fukuda Metal Foil Powder Co., Ltd., CF-T8G-UN) and polyimide film (Toray DuPont, Kapton). 100H), and heated and pressurized (150 ° C., 10 kgf / cm ² , 10 minutes) using a hot press machine (MVLP500, manufactured by Meiki Seisakusho Co., Ltd.) to obtain a laminated sheet. The laminated sheet was cut into 2 cm × 5 cm, the end of the copper foil and the end of the polyimide were sandwiched between chucks, a 180 ° peel test (JIS Z 0237) was performed, and the adhesive force was measured. The adhesive strength was evaluated by ◯ indicating that the adhesive strength was 6N or more and x indicating that the adhesive strength was less than 6N.

(4) Long-term storage stability After the white powder of the polyvinyl acetal resins A to H obtained in Examples 1 to 5, Reference Example 6 and Comparative Examples 1 to 2 is vacuum dried in an environment of 60 ° C. for 5 hours, 40 After being left for 1 week in a thermo-hygrostat (manufactured by Espec Corp., CSH-111) kept at 90 ° C. and 90% RH, the moisture content in the resin was measured. Long-term storage stability was evaluated with a water content of 5 wt% or less as ○ and a water content exceeding 5 wt% as x.

According to the present invention, a modified polyvinyl acetal resin having excellent flexibility and heat resistance can be provided. Moreover, according to this invention, the modified polyvinyl acetal resin which is excellent also in adhesiveness and storage stability can be provided.

Claims (3)

A structural unit having a hydroxyl group represented by the following formula (1), a structural unit having an acetyl group represented by the following formula (2), a structural unit having an acetal group represented by the following formula (3), and the following Having a structural unit represented by formula (4),
The structural unit represented by the following formula (4) has a structure represented by the following formula (5),
Modified polyvinyl acetal resin in which the content of the structural unit having a hydroxyl group represented by the formula (1) is characterized in that it is a 25-4 0 mol%.

In Formula (3), R ¹ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. In formula (4), R ² represents a single bond, an alkylene group or an arylene group. R ³ represents a group having a lactam ring represented by the formula (5) which may be substituted. In formula (5), X and Y each represent a single bond bonded to R ^2, and when other than a single bond, an alkyl group, a hydroxy group, a carboxyl group, an amino group, a cyano group, a nitro group, carbonyl group, an amide group, an imino group, a substituent having at least one selected from the group consisting of azo group and an ether bond, or to display the hydrogen atom, n is an integer of 0-5. However, the case where n is 3 is excluded. The modified polyvinyl acetal resin according to claim 1, wherein the structural unit represented by the formula (4) is such that R ² is a linear alkylene group and Y is a single bond. Content of the structural unit represented by Formula (4) is 30 mol% or less, The modified polyvinyl acetal resin of Claim 1 or 2 characterized by the above-mentioned.