POLYVINYL ACETAL RESIN

Abstract

The present invention provides a polyvinyl acetal resin that has an excellent dispersing property and enables the production of a formed article having high mechanical strength. Provided is a polyvinyl acetal resin having a water absorption per unit area of 2 mg/cm.sup.2 or greater and 50 mg/cm.sup.2 or less when formed into a film having a thickness of 10 .Math.m.

Claims

1. A polyvinyl acetal resin having a water absorption per unit area of 2 mg/cm.sup.2 or greater and 50 mg/cm.sup.2 or less when formed into a film having a thickness of 10 .Math.m.

2. The polyvinyl acetal resin according to claim 1, having an average degree of polymerization of 200 to 5,000.

3. The polyvinyl acetal resin according to claim 1, having an acetal group content of 1 to 50 mol%.

4. The polyvinyl acetal resin according to claim 1, which is an acetalized product of a polyvinyl alcohol resin having a degree of saponification of 75 mol% or greater.

5. A slurry composition comprising: the polyvinyl acetal resin according to claim 1; magnetic material powder; and a solvent.

Description

DESCRIPTION OF EMBODIMENTS

[0102] The present invention is more specifically described in the following with reference to, but not limited to, examples.

Example 1

(Production of Polyvinyl Acetal Resin)

[0103] An amount of 500 g of a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 350 cm.sup.-1) was added to 2,500 g of pure water and stirred at a temperature of 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution was added 10 g of hydrochloric acid having a concentration of 35% by weight. The solution temperature was cooled to 5° C., and 75 g of acetaldehyde was added. This temperature was maintained to perform acetalization reaction. The solution was then maintained at a solution temperature of 65° C. for five hours to complete the reaction, and 40 g of an aqueous sodium hydroxide solution was added for neutralization reaction, whereby a polyvinyl acetal resin was obtained.

[0104] The obtained polyvinyl acetal resin was subjected to .sup.13C-NMR (nuclear magnetic resonance spectroscopy) to measure the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, and the acetyl group content.

[0105] The obtained polyvinyl acetal resin was also subjected to IR measurement using HORIBA FT-720 (produced by Horiba, Ltd.) to measure the hydroxy group half-width. Table 1 shows the results.

[0106] After the measurement of the hydroxy group half-width, the hydroxy group content measured by .sup.13C-NMR was divided by the hydroxy group half-width to calculate the hydroxy group half-width in terms of mol%.

Example 2

[0107] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 345 cm.sup.-1) was used. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 3

[0108] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 345 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 7.0 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 4

[0109] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 380 cm.sup.-1) was used, and that 15.0 g of butyraldehyde was added instead of acetaldehyde. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 5

[0110] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 370 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 110 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 6

[0111] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 90 mol%, average degree of polymerization 600, hydroxy group half-width 335 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 7.0 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 7

[0112] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 90 mol%, average degree of polymerization 4,500, hydroxy group half-width 345 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 75 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 8

[0113] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 345 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 115 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 9

[0114] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 95 mol%, average degree of polymerization 600, hydroxy group half-width 345 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 110 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Example 10

[0115] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 82 mol%, average degree of polymerization 600, hydroxy group half-width 345 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 60 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

(Comparative Example 1)

[0116] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 335 cm.sup.-1) was used. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

(Comparative Example 2)

[0117] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 335 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 140 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

(Comparative Example 3)

[0118] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 88 mol%, average degree of polymerization 600, hydroxy group half-width 335 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 5 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

(Comparative Example 4)

[0119] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 92 mol%, average degree of polymerization 600, hydroxy group half-width 345 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 6 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

(Comparative Example 5)

[0120] A polyvinyl acetal resin was obtained as in Example 1 except that a polyvinyl alcohol resin (degree of saponification 90 mol%, average degree of polymerization 600, hydroxy group half-width 470 cm.sup.-1) was used, and that the amount of acetaldehyde added was changed to 75 g. The measurements performed as in Example 1 showed that the acetal group content (acetoacetal group content, butyral group content), the hydroxy group content, the acetyl group content, the hydroxy group half-width, and the hydroxy group half-width in terms of mol% were as shown in Table 1.

Evaluation

[0121] The polyvinyl acetal resins obtained in the examples and the comparative examples were evaluated as follows. Table 1 shows the results.

Measurement of Water Absorption Per Unit Area and Water Absorption Rate

[0122] Each of the polyvinyl acetal resins obtained in the examples and the comparative examples was formed into a film having a thickness of 10 .Math.m by a doctor blade method, dried at 70° C. for three hours, and then left to stand in an environment at a temperature of 20° C. and a humidity of 55% for one hour or longer. The weight A of the film was then measured.

[0123] Subsequently, a main surface of the film was exposed to warm water vapor having a temperature of 50° C. Exposure to water vapor was terminated when waterdrops appeared on the surface of the film. The weight B of the film was then measured. The water absorption was calculated by subtracting the weight A from the weight B. The water absorption per unit area was calculated by dividing the water absorption by the exposed area.

[0124] The exposed area in the examples and the comparative examples herein was 40 cm.sup.2.

[0125] Further, the time from the start to the termination of the exposure to water vapor (exposure time) was measured. The value of the weight of the film per unit area divided by the exposure time was calculated as the water absorption rate.

Dispersing Property Test (Ferrite Dispersing Property)

(Production of Slurry Composition)

[0126] To 50 g of the obtained polyvinyl acetal resin were added 21.4 g of ion-exchanged water, 28 g of ferrite as magnetic material powder, and 0.6 g of glycerol as a plasticizer. After stirring at 1,200 rpm for 1.5 hours using a disperser produced by PRIMIX Corporation, deaeration was performed at 1,000 rpm for 30 minutes using Thinky Mixer produced by Thinky Corporation. Thus, a slurry composition was produced. The ferrite used was Ni-Cu-Zn ferrite.

(Measurement of Particle Size Distribution)

[0127] To the obtained slurry composition were added 5 g of ethanol and 5 g of toluene. They were stirred to produce an evaluation solution.

[0128] The evaluation solution was then subjected to particle size distribution measurement using a laser diffraction-type particle size distribution analyzer (produced by HORIBA, Ltd., “LA-910”) to determine the D50 particle size of the magnetic material powder. The D50 particle size after the solution was left to stand at 23° C. for one week was also measured in the same manner. The rate of change in D50 particle size was calculated and evaluated in accordance with the following criteria. [0129] A: A rate of change of less than 30% [0130] B: A rate of change of 30% or greater and less than 60% [0131] C: A rate of change of 60% or greater and less than 100% [0132] D: A rate of change of 100% or greater

Adhesiveness to Substrates

(Production of Resin Sheet)

[0133] The obtained polyvinyl acetal resin was applied using a coater to a release-treated PET film to give a dried thickness of 15 .Math.m and dried at 70° C. for 120 minutes to produce a resin sheet.

[0134] The obtained resin sheet was applied to various substrates (SPCC, PET, and PC) to give a dried thickness of 20 .Math.m and then dried to provide adhesiveness measurement samples.

[0135] The adhesiveness of the obtained measurement samples was evaluated using a cross-cut test specified in JIS K 5400.

Stress at Upper Yield Point, Strain at Break, and Stress at Break

(Sheet Strength)

[0136] The stress at the upper yield point (MPa), the strain at break (%), and the stress at break (MPa) of the obtained resin sheet were measured in conformity with JIS K 7113 using a tensile tester (AUTOGRAPH AGS-J produced by Shimadzu Corporation) at a tensile speed of 20 mm/min.

TABLE-US-00001 Slurry composition Evaluation Polyvinyl acetal resin Ferrite dispersing property Adhesiveness to substrates Resin sheet evaluation Average degree of polymerization Acetoacetal group content (mol%) Butyral group content (mol%) Hydroxy group content (mol%) Hydroxy group half-width (cm.sup.-1) Hydroxy group half-width in terms of mol% (mol%/cm.sup.-1) Acetyl group content (mol%) Water absorption (mg/cm.sup.2) Water absorption rate (mg/cm.sup.2.Math. min) Particle size distribution SPCC PET PC Stress at upper yield point (MPa) Stress at break (MPa) Strain at break (%) Example 1 600 30.0 0 58.0 315 0.184 12 3.5 0.4 A 10 6 4 80 100 260 Example 2 600 30.0 0 58.0 310 0.187 12 5.0 0.5 A 10 6 4 70 95 290 Example 3 600 3.0 0 85.0 300 0.283 12 10.0 1.1 B 10 4 4 60 80 310 Example 4 600 0.0 3.5 84.5 330 0.256 12 5.0 0.6 C 10 4 4 100 90 220 Example 5 600 43.0 0 45.0 320 0.141 12 2.5 0.3 A 10 8 6 85 105 300 Example 6 600 3.0 0 87.0 290 0.293 10 48.0 3.5 B 10 4 4 60 75 230 Example 7 4500 30.0 0 60.0 310 0.194 10 5.2 0.4 C 10 4 4 125 135 350 Example 8 600 45.0 0 43.0 300 0.143 12 3.2 0.3 B 10 8 6 80 100 305 Example 9 600 30.0 0 65.0 300 0.217 5 12.0 1.3 B 10 6 4 100 90 230 Example 10 600 24.0 0 58.0 300 0.193 18 9.5 0.8 C 10 6 4 65 100 300 Comparative Example 1 600 30.0 0 58.0 275 0.211 12 1.9 0.2 D 10 4 4 50 70 200 Comparative Example 2 600 55.0 0 33.0 280 0.118 12 1.8 0.1 D 10 6 6 45 55 170 Comparative Example 3 600 0.5 0 87.5 270 0.324 12 1.5 0.1 D 10 4 4 105 110 30 Comparative Example 4 600 0.8 0 91.2 310 0.294 8 52.0 4.5 D 8 2 2 115 125 10 Comparative Example 5 600 30.0 0 60.0 425 0.141 10 1.8 0.2 D 10 4 4 130 135 105

INDUSTRIAL APPLICABILITY

[0137] The present invention can provide a polyvinyl acetal resin that has an excellent dispersing property and enables the production of a formed article having high mechanical strength.