JP2015025042A - Polyvinyl acetal resin for adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl acetal resin for an adhesive that is used for an adhesive for use in adhesive bonding of a printed circuit board with a copper foil or the like and is excellent in mechanical strength and adhesiveness.SOLUTION: The polyvinyl acetal resin for an adhesive has a constitutional unit having a hydroxyl group, a constitutional unit having an acetyl group, a constitutional unit having an acetal group and a constitutional unit having an ethylene oxide group. The ratio of the constitutional unit having a hydroxyl group is 15-65 mol% based on the total of the polyvinyl acetal resin and the ratio of the constitutional unit having an ethylene oxide group is 3-12 mol% based on the total of the polyvinyl acetal resin.

Description

The present invention relates to a polyvinyl acetal resin for adhesives excellent in mechanical strength and adhesiveness.

In general, printed circuit boards used for IT-related materials are made by laminating a metal foil such as copper foil on a resin base material such as PET by using an adhesive, and then etching the metal foil. Thus, it can be obtained by forming a desired printed circuit made of a metal foil. In recent years, highly flexible flexible substrates made of polyimide or the like have attracted attention.

As an adhesive for adhering the base material and copper foil or the like, it has been conventionally represented by an adhesive composition mainly composed of polyvinyl acetal resin represented by polyvinyl butyral resin, phenol resin, epoxy resin, melamine resin and the like. Adhesive compositions mainly composed of a thermosetting resin are widely used.

Patent Document 1 describes a modified polyvinyl acetal resin in which a predetermined amount of an alkylene oxide having 2 to 12 carbon atoms is added to a hydroxyl group in a polyvinyl acetal resin as a resin that can also be used as an adhesive.
However, the modified polyvinyl acetal resin described in Patent Document 1 has a problem that the adhesiveness to a resin such as PET or polyimide or a metal foil such as a copper foil is insufficient.

JP 2009-001631 A

An object of this invention is to provide the polyvinyl acetal resin for adhesives excellent in mechanical strength and adhesiveness.

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 ratio with respect to the whole polyvinyl acetal resin for adhesives of the structural unit represented by following formula (1) which has a structural unit represented by following formula (4) is 15-65 mol%, and is shown below. The ratio with respect to the whole polyvinyl acetal resin for adhesives of the structural unit represented by Formula (4) is a polyvinyl acetal resin for adhesives which is 3-12 mol%.

式（３）中、Ｒ^１は、水素原子又は炭素数１〜２０のアルキル基を表す。

In Formula (3), R ¹ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

式（４）中、Ｒ^２は、エチレンオキサイド基を有する基を表す。
以下、本発明を詳述する。

In formula (4), R ² represents a group having an ethylene oxide group.
The present invention is described in detail below.

The polyvinyl acetal resin for adhesives of the present invention has a structural unit having a hydroxyl group represented by the following formula (1).
By having a structural unit having a hydroxyl group represented by the following formula (1), it is possible to enhance the adhesion to the substrate.

The lower limit of the proportion of the structural unit represented by the above formula (1) with respect to the entire polyvinyl acetal resin for adhesives of the present invention is 15 mol%, and the upper limit is 65 mol%. When the proportion of the structural unit having a hydroxyl group represented by the above formula (1) is less than 15 mol%, the water-solubility of the polyvinyl acetal resin for adhesives is lowered, and at the same time, the synthesis becomes extremely difficult. In particular, the solubility in polar solvents used for adhesives is significantly reduced.
As for the ratio of the structural unit having a hydroxyl group represented by the above formula (1), a preferable lower limit is 20 mol% and a preferable upper limit is 60 mol%.

The polyvinyl acetal resin for adhesives of the present invention has a structural unit having an acetyl group represented by the following formula (2).
By having a structural unit having an acetyl group represented by the following formula (2), the viscosity of the adhesive composition containing the polyvinyl acetal resin for adhesives of the present invention can be lowered, and handling of the adhesive composition Can be improved.

As for the ratio of the structural unit which has an acetyl group represented by the said Formula (2) with respect to the whole polyvinyl acetal resin for adhesive agents of this invention, a preferable minimum is 0.01 mol% and a preferable upper limit is 30 mol%. When the proportion of the structural unit having an acetyl group represented by the above formula (2) is less than 0.01 mol%, the viscosity of polyvinyl alcohol as a raw material becomes high and the synthesis becomes extremely difficult, and exceeds 30 mol%. And the viscosity stability of the adhesive composition containing the polyvinyl acetal resin for adhesive may be lowered.
As for the ratio of the structural unit which has an acetyl group represented by the said Formula (2), a more preferable minimum is 0.5 mol% and a more preferable upper limit is 20 mol%.

The polyvinyl acetal resin for adhesives of the present invention has a structural unit having an acetal group represented by the following formula (3).
By having the structural unit having an acetal group represented by the following formula (3), the flexibility of the resin and the adhesion to the substrate can be improved.

式（３）中、Ｒ^１は、水素原子又は炭素数１〜２０のアルキル基を表す。
なかでも、合成が容易であることから、上記式（２）中のＲ^１は、メチル基又はプロピル基であることが好ましい。

In Formula (3), R ¹ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.
Among them, since the synthesis is easy, R ¹ in the formula (2) is preferably a methyl group or a propyl group.

The preferable lower limit of the degree of acetalization is 35%, and the preferable upper limit is 85%. If the degree of acetalization is less than 35%, the flexibility of the polyvinyl acetal resin for adhesives may be reduced and adhesion may be reduced. If the degree of acetalization exceeds 85%, synthesis becomes extremely difficult. The solubility in polar solvents used for adhesives may be significantly reduced.
A more preferable lower limit of the degree of acetalization is 40%, and a more preferable upper limit is 80%.
In the present specification, the degree of acetalization means the ratio of the number of acetalized hydroxyl groups in the number of hydroxyl groups of polyvinyl alcohol which is a raw material of the polyvinyl acetal resin for adhesives of the present invention.
The proportion (mol%) of the structural unit having an acetal group represented by the above formula (3) with respect to the entire polyvinyl acetal resin for adhesives of the present invention is the above-mentioned acetalization to the hydroxyl group amount (mol%) of polyvinyl alcohol as a raw material. It can be calculated by multiplying the degree (%).
As for the ratio of the structural unit which has an acetal group represented by the said Formula (3) with respect to the whole polyvinyl acetal resin for adhesives of this invention, a preferable minimum is 26 mol% and a preferable upper limit is 85 mol%.

The polyvinyl acetal resin for adhesives of the present invention has a structural unit represented by the following formula (4).
By having a structural unit represented by the following formula (4), the polyvinyl acetal resin for adhesives of the present invention reduces the influence of interactions such as hydrogen bonding between the polyvinyl acetal resins and is flexible as an adhesive composition. Sex can be imparted.

式（４）中、Ｒ^２は、エチレンオキサイド基を有する基を表す。

In formula (4), R ² represents a group having an ethylene oxide group.

The ratio of the structural unit represented by the above formula (4) to the whole polyvinyl acetal resin for adhesives of the present invention, that is, the lower limit of the degree of modification in the polyvinyl acetal resin for adhesives of the present invention is 3 mol%, and the upper limit is 12 mol%. It is. When the proportion of the structural unit represented by the above formula (4) is less than 3 mol%, the adhesive property to the base material of the polyvinyl acetal resin for an adhesive is significantly reduced. It becomes difficult to acetalize the modified polyvinyl alcohol, which is a raw material for the polyvinyl acetal resin.
As for the ratio of the structural unit represented by the above formula (4), a preferred lower limit is 5 mol% and a preferred upper limit is 10 mol%.
In addition, in this specification, the ratio of the structural unit represented by the above formula (4) to the whole polyvinyl acetal resin for adhesive is the ratio of the structural unit represented by the above formula (4) to the whole modified polyvinyl alcohol as a raw material. It can be obtained from the ratio. Moreover, in this specification, the modified degree of modified polyvinyl alcohol means the average value calculated | required from the modified degree of each modified polyvinyl alcohol in modified polyvinyl alcohol which is a mixture.

R ² is not particularly limited as long as it has an ethylene oxide repeating unit, and examples thereof include a structure having a linear, branched, or cyclic hydrocarbon group in addition to the ethylene oxide repeating unit.

More specifically, examples of the structural unit represented by the above formula (4) include a structural unit represented by the following formula (5).
Since it has a structural unit represented by the following formula (5), it reduces the influence of hydrogen bonding between polyvinyl acetal resins, and the thermal motion of the polyvinyl acetal resins becomes more active, so when used as an adhesive composition Can be given flexibility.

式（５）中、Ｒ^３は炭素数０〜６の直鎖状又は分枝状の炭化水素基を表し、ｎは１〜２０の整数を表す。

In Formula (5), R ³ represents a linear or branched hydrocarbon group having 0 to 6 carbon atoms, and n represents an integer of 1 to 20.

When n in said Formula (5) is an integer of 1-20, the polyvinyl acetal resin for adhesives of this invention is synthesize | combined from the polyvinyl alcohol which has a structural unit represented by said Formula (5) as a raw material. be able to.
As for n in the said Formula (5), it is more preferable that it is an integer of 7-20. When n in the above formula (5) is an integer of 7 to 20, the ratio of hydroxyl groups in the whole polyvinyl acetal resin becomes lower, and the influence of hydrogen bonding due to hydroxyl groups between the polyvinyl acetal resins is further reduced. Thereby, since the thermal motion of the polyvinyl acetal resin becomes active, when used as an adhesive composition, it exhibits better adhesion to a resin such as PET or polyimide, or a metal foil such as a copper foil. be able to.
A more preferred upper limit of n in the above formula (5) is 15, a particularly preferred lower limit is 10, and a particularly preferred upper limit is 12. Note that n is an integer.

When R ³ in the above formula (5) is a linear or branched hydrocarbon group having 0 to 6 carbon atoms, the polyvinyl acetal resin for adhesives of the present invention can be synthesized. R ³ in the above formula (5) is more preferably a linear or branched hydrocarbon group having 0 to 4 carbon atoms, and is a linear hydrocarbon group having 0 to 2 carbon atoms. More preferably.

The minimum with a preferable average polymerization degree of the polyvinyl acetal resin for adhesives of this invention is 150, and a preferable upper limit is 4000. When the average degree of polymerization is less than 150, the mechanical strength of the adhesive composition containing the polyvinyl acetal resin for adhesive may be lowered, and when it exceeds 4000, the adhesive composition containing the polyvinyl acetal resin for adhesive is contained. The viscosity stability of the product may decrease.
The more preferable lower limit of the average degree of polymerization of the polyvinyl acetal resin for adhesives of the present invention is 200, the more preferable upper limit is 3,500, the still more preferable lower limit is 300, the still more preferable upper limit is 3000, and the particularly preferable upper limit is 1200.
In the present specification, the average degree of polymerization of the polyvinyl acetal resin for adhesives can be determined from the average degree of polymerization of the modified polyvinyl alcohol as a raw material. In the present specification, the average degree of polymerization of the modified polyvinyl alcohol means a value calculated from the degree of polymerization and the mixing ratio of each modified polyvinyl alcohol when a plurality of modified polyvinyl alcohols having different degrees of polymerization are used. .

The polyvinyl acetal resin for adhesives of the present invention is preferably produced using polyvinyl alcohol having a structural unit represented by the above formula (4).
As a method for producing a polyvinyl acetal resin having an ethylene oxide group, a polyvinyl alcohol not having an ethylene oxide group is acetalized to form a polyvinyl acetal resin, and then an ethylene oxide group is introduced by adding a compound having an ethylene oxide group and a metal catalyst. The method of doing is mentioned. However, in such a method, since the obtained polyvinyl acetal resin contains a large amount of catalyst-derived metal ions, there is a problem that turbidity occurs when it is dissolved in a solvent to form an adhesive composition. Moreover, unevenness is easily generated when the adhesive composition is applied to the substrate, and it is difficult to maintain a uniform adhesive force to the substrate. Furthermore, when the obtained polyvinyl acetal resin is used in an adhesive composition for electronic components, the quality of the electronic components may be deteriorated by energizing the bonded portion.
On the other hand, when the polyvinyl acetal resin is produced using the modified polyvinyl alcohol having the structural unit represented by the above formula (4), it is not necessary to use a metal catalyst, and the metal content of the obtained polyvinyl acetal resin for an adhesive is obtained. Are very few. Therefore, when the polyvinyl acetal resin for adhesives of the present invention is used in an adhesive composition, it is possible to obtain an adhesive composition having high transparency and having a uniform adhesive force to a substrate. Moreover, when the polyvinyl acetal resin for adhesives of this invention is used for the adhesive composition for electronic components, a reliable electronic component can be obtained.

As a manufacturing method of the polyvinyl acetal resin for adhesives of the present invention, 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 the above formula The method of acetalizing the modified polyvinyl alcohol which has a structural unit represented by (4) is mentioned.
Moreover, the polyvinyl acetal resin for adhesives of the present invention comprises a polyvinyl alcohol having a structural unit having a hydroxyl group represented by the above formula (1) and a structural unit having an acetyl group represented by the above formula (2). It can also be obtained by acetalization and then copolymerization with a modified polyvinyl alcohol having a structural unit represented by the above formula (4).
The acetalization can be performed, for example, by adding various aldehydes to the aqueous solution, alcohol solution, water / alcohol mixed solution, or dimethyl sulfoxide (DMSO) solution of the modified polyvinyl alcohol in the presence of an acid catalyst. it can.
Thereafter, in order to stop the acetalization reaction, neutralization with an alkali is preferably performed. 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.

As the acid catalyst, inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid and organic acids such as formic acid, acetic acid and paratoluenesulfonic acid can be used.

The aldehyde 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 them, it is preferable to use acetaldehyde or butyraldehyde alone or use acetaldehyde and butyraldehyde in combination.

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.

In the modified polyvinyl alcohol having the structural unit represented by the above formula (4), the preferable lower limit of the degree of saponification is 75 mol%, and the preferable upper limit is 99.9 mol%. When the above range is exceeded, the solubility of the raw material polyvinyl alcohol resin is lowered, and the acetalization reaction may be difficult.

As for the polyvinyl acetal resin for adhesives of this invention, the minimum with a preferable glass transition temperature is 20 degreeC, and a preferable upper limit is 60 degreeC. If the glass transition temperature of the polyvinyl acetal resin for adhesives of the present invention is less than 20 ° C, long-term storage stability may be lowered, and if it exceeds 60 ° C, sufficient adhesiveness may not be obtained. In the polyvinyl acetal resin for adhesives of the present invention, the lower limit of the glass transition temperature is more preferably 25 ° C, the more preferable upper limit is 55 ° C, and the further preferable upper limit is 52 ° C.
When the glass transition temperature of the polyvinyl acetal resin for adhesives of the present invention is 52 ° C. or less and the average polymerization degree is 150 to 1200, it is particularly preferable because of excellent adhesion to polyethylene terephthalate (PET) and copper foil.

The composition of the polyvinyl acetal resin for adhesives of the present invention can be determined, for example, by nuclear magnetic resonance spectrum ( ¹ H-NMR). The average polymerization degree and saponification degree can be measured by a method according to JIS K6726-1994. The glass transition point (Tg) can be measured by, for example, a differential scanning calorimeter (using a DSC-6200R, manufactured by Seiko Denshi Kogyo Co., Ltd., at a heating rate of 10 ° C./min, in accordance with JIS K7121). .

The polyvinyl acetal resin for adhesives of the present invention can be used in an adhesive composition.
By using the polyvinyl acetal resin for adhesives of the present invention, water can be used as a solvent instead of an organic solvent, which is preferable from the viewpoint of environmental pollution, toxicity, risk of explosion accidents, and the like.

The adhesive composition containing the polyvinyl acetal resin for adhesives of the present invention further includes a curable resin such as an organic solvent, water, and an epoxy resin, or a phenol resin, a nitrile butadiene rubber, a polyamide resin, It is preferable to contain a polymer compound such as a polyimide resin, a polyurethane resin, a polyolefin resin, a polyester resin, and a bismaleimide triazine resin. In addition, if necessary, curing agents, flame retardants, effect accelerators, antioxidants, coupling agents, thickeners, leveling agents, antifoaming agents, inorganic fillers such as silica, calcium carbonate, hydrotalcite, etc. The additive may be contained.

Examples of the organic solvent include ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol and butanol; and aromatic solvents such as toluene and xylene. As a single solvent, or two or more kinds can be used as a mixed solvent.

The content of the organic solvent with respect to the entire adhesive composition is preferably 70% by weight or less. By making content with respect to the whole adhesive composition of the said organic solvent into such a range, the adhesiveness of an adhesive composition can be improved.

The content of water with respect to the entire adhesive composition is preferably 70% by weight or less. By making content with respect to the whole said adhesive composition of water into such a range, the adhesiveness of an adhesive composition can be improved.

The said adhesive composition can be dried and a dry body can be obtained. The remaining amount of the organic solvent with respect to the entire dried body is preferably 10% by weight or less, and the remaining amount of water with respect to the entire dried body is preferably 10% by weight or less. By setting the remaining amount of the organic solvent and water in such a range, the adhesiveness of the dried body obtained by drying the adhesive composition can be improved.

ADVANTAGE OF THE INVENTION According to this invention, the polyvinyl acetal resin for adhesives excellent in mechanical strength and adhesiveness 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
The modified polyvinyl alcohol has a structural unit represented by the above formula (5), R ³ has 0 carbon atoms, n is 10, and is represented by the above formula (5) for the entire modified polyvinyl alcohol. Polyvinyl alcohol having a constituent unit ratio (degree of modification) of 10 mol% was used. The modified polyvinyl alcohol had an average polymerization degree of 500 and a saponification degree of 89 mol%.

In the reactor, 193 g of the modified polyvinyl alcohol (average polymerization degree 500, saponification degree 89 mol%) and 2900 g of pure water were added and stirred at 90 ° C. for 2 hours to completely dissolve the modified polyvinyl alcohol. Then, 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 n-butyraldehyde is added, the liquid temperature is cooled to 15 ° C., and this temperature is maintained to carry out the acetalization reaction. And the reaction product was precipitated. Thereafter, the liquid temperature was set at 40 ° C. and held for 3 hours to complete the reaction, neutralized with sodium hydrogen carbonate, the acetalization reaction was stopped, and after washing with water and drying, the polyvinyl acetal resin for adhesives A white powder was obtained.

^When the composition of the obtained polyvinyl acetal resin for adhesives was measured using a ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) (hydroxyl group amount) was 24 mol%, The proportion of the structural unit having an acetyl group represented by the above formula (2) is 1 mol%, the degree of acetalization is 73%, the structural unit having an acetal group represented by the above formula (3) (of the formula (3) The proportion of R ¹ is a propyl group is 64.97 mol%, and the structural unit represented by the above formula (5) (in formula (5), R ³ has 0 carbon atoms and n is 10 The ratio (degree of modification) was 10 mol%.
The average degree of polymerization of the obtained polyvinyl acetal resin for adhesive was 500, and the glass transition temperature was 33 ° C.
The glass transition temperature was measured according to JIS K 7121 using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC-6200R) at a heating rate of 10 ° C./min.

(Example 2)
The modified polyvinyl alcohol has a structural unit represented by the above formula (5), R ³ has 0 carbon atoms, n is 10, and is represented by the above formula (5) for the entire modified polyvinyl alcohol. For adhesives, in the same manner as in Example 1, except that a modified polyvinyl alcohol having a structural unit ratio (degree of modification) of 5 mol%, an average degree of polymerization of 500, and a saponification degree of 94 mol% was used. A white powder of polyvinyl acetal resin was obtained.

^When the composition of the obtained polyvinyl acetal resin for adhesives was measured using a ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) (hydroxyl group amount) was 27 mol%, The proportion of the structural unit having an acetyl group represented by the formula (2) is 1 mol%, the degree of acetalization is 71%, and the structural unit having an acetal group represented by the formula (3) (of the formula (3) The proportion of R ¹ is a propyl group is 66.74 mol%, and the structural unit represented by the above formula (5) (in formula (5), R ³ has 0 carbon atoms and n is 10 ) Was 5 mol%.
Moreover, the average degree of polymerization of the obtained polyvinyl acetal resin for adhesives was 500, and the glass transition temperature was 52 ° C.

Example 3
The modified polyvinyl alcohol has a structural unit represented by the above formula (5), R ³ has 0 carbon atoms, n is 10, and is represented by the above formula (5) for the entire modified polyvinyl alcohol. For the adhesive, in the same manner as in Example 1, except that a modified polyvinyl alcohol having a constitutional unit ratio (degree of modification) of 5 mol%, an average degree of polymerization of 1700, and a saponification degree of 90 mol% was used. A white powder of polyvinyl acetal resin was obtained.

^When the composition of the obtained polyvinyl acetal resin for adhesives was measured using a ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) was 26 mol%, and the above formula (2 ) Is 5 mol%, the degree of acetalization is 71%, the structural unit having an acetal group represented by the above formula (3) (R ^{1 in} formula (3) is propyl And the structural unit represented by the above formula (5) (in the formula (5), R ³ has 0 carbon atoms and n is 10). The ratio was 5 mol%.
Moreover, the average degree of polymerization of the obtained polyvinyl acetal resin for adhesives was 1700, and the glass transition temperature was 54 degreeC.

Example 4
The modified polyvinyl alcohol has a structural unit represented by the above formula (5), R ³ has 0 carbon atoms, n is 10, and is represented by the above formula (5) for the entire modified polyvinyl alcohol. A modified polyvinyl alcohol having a constitutional unit ratio (modification degree) of 10 mol%, an average polymerization degree of 500, and a saponification degree of 89 mol% was used.
In the reactor, 255 g of the modified polyvinyl alcohol and 2700 g of pure water were added and stirred at 90 ° C. for 2 hours to completely dissolve the modified polyvinyl alcohol. Then, it cooled to 45 degreeC, 20 g of hydrochloric acid with a density | concentration of 35% was added as a catalyst, and it cooled to 35 degreeC. Next, 18.8 g of acetaldehyde was added and stirred at 35 ° C. for 5 hours to conduct an acetalization reaction to obtain a transparent reaction solution.
While stirring the obtained transparent reaction solution, 66 g of a 10% by weight sodium hydroxide aqueous solution was added for neutralization, and then cooled to 20 ° C. to obtain a transparent polyvinyl butyral resin solution for adhesive.

^When the composition of the obtained polyvinyl acetal resin for adhesives was measured using ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) was 55 mol%, and the above formula (2 The proportion of the structural unit having an acetyl group represented by 1) is 1 mol%, the degree of acetalization is 38%, the structural unit having an acetal group represented by the above formula (3) (R ^{1 in} formula (3) is propyl And the structural unit represented by the above formula (5) (in the formula (5), R ³ has 0 carbon atoms and n is 10). The ratio was 10 mol%.
The average degree of polymerization of the obtained polyvinyl acetal resin for adhesive was 500.

(Comparative Example 1)
A white powder of polyvinyl acetal resin for adhesives as in Example 1 except that polyvinyl alcohol having an average polymerization degree of 800 and a saponification degree of 98 mol% and not modified with an ethylene oxide group was used as the polyvinyl alcohol. Got.

^When the composition of the obtained polyvinyl acetal resin for an adhesive was measured using ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) was 30 mol%, and the above formula (2 ) Is 2 mol%, the degree of acetalization is 69%, the structural unit having an acetal group represented by the above formula (3) (R ^{1 in} formula (3) is propyl Group) was 67.62 mol%, and the proportion of the structural unit having an ethylene oxide group was 0 mol%.
Moreover, the average polymerization degree of the obtained polyvinyl acetal resin for adhesives was 800, and the glass transition temperature was 67 degreeC.

(Comparative Example 2)
A white powder of polyvinyl acetal resin for adhesives as in Example 1 except that polyvinyl alcohol having an average polymerization degree of 1700 and a saponification degree of 99 mol% and not modified with an ethylene oxide group was used as the polyvinyl alcohol. Got.

^When the composition of the obtained polyvinyl acetal resin for adhesives was measured using ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) was 32 mol%, and the above formula (2 ) Is 1 mol%, the degree of acetalization is 67%, the structural unit having an acetal group represented by the above formula (3) (R ^{1 in} formula (3) is propyl Group) was 66.33 mol%, and the proportion of structural units having an ethylene oxide group was 0 mol%.
Moreover, the average degree of polymerization of the obtained polyvinyl acetal resin for adhesives was 1700, and the glass transition temperature was 71 degreeC.

(Comparative Example 3)
As the modified polyvinyl alcohol, the modified polyvinyl alcohol used in Example 1 was used without performing an acetalization reaction.

^When the composition of the obtained polyvinyl alcohol was measured using a ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group (hydroxyl amount) represented by the above formula (1) was 89 mol%, and the above formula (2 ) Is 1 mol%, the degree of acetalization is 0%, the proportion of the structural unit having an acetal group represented by the above formula (3) is 0 mol%, and the above The proportion of the structural unit represented by the formula (5) (in the formula (5), R ³ has 0 carbon atoms and n is 10) was 10 mol%.
The average degree of polymerization of the obtained polyvinyl alcohol was 500.

(Comparative Example 4)
The modified polyvinyl alcohol has a structural unit represented by the above formula (5), R ³ has 0 carbon atoms, n is 10, and is represented by the above formula (5) for the entire modified polyvinyl alcohol. For the adhesive, in the same manner as in Example 1, except that a modified polyvinyl alcohol having a structural unit ratio (modification degree) of 2 mol%, an average polymerization degree of 1700, and a saponification degree of 97 mol% was used. A white powder of polyvinyl acetal resin was obtained.

^When the composition of the obtained polyvinyl acetal resin for adhesives was measured using a ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) was 25 mol%, and the above formula (2 ) Is 1 mol%, the degree of acetalization is 74%, the structural unit having an acetal group represented by the above formula (3) (R ^{1 in} formula (3) is propyl And the structural unit represented by the above formula (5) (in the formula (5), R ³ has 0 carbon atoms and n is 10). The ratio was 2 mol%.
Moreover, the average polymerization degree of the obtained polyvinyl acetal resin for adhesives was 1700, and the glass transition temperature was 58 degreeC.

(Comparative Example 5)
The modified polyvinyl alcohol has a structural unit represented by the above formula (5), R ³ has 0 carbon atoms), n is 10, and is represented by the above formula (5) for the whole modified polyvinyl alcohol. In the same manner as in Example 1, except that a modified polyvinyl alcohol having a proportion (modification degree) of 2 mol%, an average polymerization degree of 500, and a saponification degree of 93 mol% was used. A white powder of polyvinyl acetal resin was obtained.

^When the composition of the obtained polyvinyl acetal resin for adhesives was measured using a ¹ H-NMR spectrum, the proportion of the structural unit having a hydroxyl group represented by the above formula (1) was 26 mol%, and the above formula (2 ) Is 5 mol%, the degree of acetalization is 72%, the structural unit having an acetal group represented by the above formula (3) (R ^{1 in} formula (3) is propyl And the structural unit represented by the above formula (5) (in the formula (5), R ³ has 0 carbon atoms and n is 10). The ratio was 2 mol%.
Moreover, the average polymerization degree of the obtained polyvinyl acetal resin for adhesives was 500, and the glass transition temperature was 56 degreeC.

<Evaluation>
The adhesive composition was manufactured using the polyvinyl acetal resin or polyvinyl alcohol obtained by the Example and the comparative example.

(Manufacture of adhesive composition)
To the polyvinyl butyral resins obtained in Examples 1 to 4 and Comparative Examples 1, 2, 4 and 5, 80 g of a mixed solvent in which ethanol and toluene were mixed at a ratio of 1: 1 as a solvent was added to obtain an adhesive composition. . The obtained adhesive composition was 19.6% by weight of polyvinyl butyral resin, 80% by weight of solvent, and 0.4% by weight of water.
In Comparative Example 3, 20 g of the obtained modified polyvinyl alcohol was dissolved in 80 g of water to obtain an adhesive composition. The obtained adhesive composition was 20% by weight of polyvinyl alcohol, 0% by weight of solvent, and 80% by weight of water.

The following evaluation was performed about the obtained adhesive composition. The results are shown in Table 1.
In Table 1, the amount of hydroxyl group (mol%) and the degree of modification (mol%) are respectively the ratio of the structural unit represented by the formula (1) to the whole polyvinyl acetal resin or polyvinyl alcohol, and the formula (4). Represents the percentage of the structural unit represented.

(1) Adhesiveness with base material Each of the polyvinyl acetal resins obtained in Examples and Comparative Examples or the adhesive composition containing polyvinyl alcohol is dried so as to have a thickness of 20 μm using a coater. After coating on the substrate, the dried product was obtained by drying. The residual amount of the solvent with respect to the entire dried product was 0.5% by weight.
Then, thermocompression bonding was performed for 10 seconds under the conditions of 80 ° C. and 0.2 MPa to obtain a pressure-bonded body. About the obtained pressure-bonded body, peel strength (g / g) when the resin sheet was peeled from the substrate at a speed of 7 mm / sec by using an adhesive force measuring device during heating (manufactured by Fujikopian, FCL011 type). cm ³ ) was measured.
As the base material, a release-treated square polyethylene terephthalate (PET) film having a side of 0.8 cm and a thickness of 50 μm, a side of 0.8 cm and a thickness of 2.6 μm of a square polyimide film, and a side of 0 μm A square copper foil having a thickness of 0.8 cm and a thickness of 2.1 μm was used.

(2) Mechanical strength The polyvinyl acetal resin obtained in Examples and Comparative Examples, or an adhesive composition containing polyvinyl alcohol was applied using a coater so that the thickness after drying was 20 μm. Then, the resin sheet of width 1cm and length 5cm was obtained by drying.
About the obtained resin sheet, it extended | stretched on the conditions of the tensile speed of 20 mm / min using AUTOGRAPH (AGS-J, Shimadzu Corp. make) by the method based on JISK7127, and elongation at break (%) It was measured.

ADVANTAGE OF THE INVENTION According to this invention, the polyvinyl acetal resin for adhesives excellent in mechanical strength and adhesiveness can be provided.

Claims (7)

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 ratio with respect to the whole polyvinyl acetal resin for adhesives of the structural unit represented by following formula (1) is 15-65 mol%,
The ratio of the structural unit represented by the following formula (4) to the entire polyvinyl acetal resin for adhesive is 3 to 12 mol%, and the polyvinyl acetal resin for adhesive is characterized in that

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 group having an ethylene oxide group. The polyvinyl acetal resin for adhesives according to claim 1, wherein the structural unit represented by the formula (4) is a structural unit having an ethylene oxide group represented by the following formula (5).

In Formula (5), R ³ represents a linear or branched hydrocarbon group having 0 to 6 carbon atoms, and n represents an integer of 1 to 20. N of Formula (5) is an integer of 7-20, The polyvinyl acetal resin for adhesives of Claim 2 characterized by the above-mentioned. 4. The polyvinyl acetal resin for adhesives according to claim 1, wherein the glass transition temperature is 60 ° C. or lower. 5. The polyvinyl acetal resin for adhesives according to claim 1, wherein the average degree of polymerization is 150 to 4000. 6. The polyvinyl acetal resin for adhesives according to claim 1, wherein the degree of acetalization is 35 to 85%. It manufactures using the polyvinyl alcohol which has a structural unit represented by the said Formula (4), The polyvinyl acetal resin for adhesives of Claim 1, 2, 3, 4, 5 or 6 characterized by the above-mentioned.