WO2015019441A1

WO2015019441A1 - Polyvinyl acetal and laminated glass interlayer comprising same

Info

Publication number: WO2015019441A1
Application number: PCT/JP2013/071343
Authority: WO
Inventors: 楠藤　健; 芳聡浅沼; 俊輔藤岡; 辻　嘉久
Original assignee: 株式会社クラレ
Priority date: 2013-08-07
Filing date: 2013-08-07
Publication date: 2015-02-12
Also published as: JPWO2015019441A1; JP5420805B1

Abstract

A polyvinyl acetal which has a degree of acetalization of 40 to 90 mol%, a content of a vinyl ester monomer unit of 0.1 to 20 mol%, and a viscosity-average polymerization degree of 200 to 5000, wherein when the polyvinyl acetal is heated for three hours at 230°C and subjected to gel permeation chromatography, a peak top molecular weight (A) measured by a differential refractive index detector and a peak top molecular weight (B) measured by an absorbance detector (measurement wavelength 280 nm) satisfy formula (1), (A-B)/A<0.60 (1), and absorbance at the peak top molecular weight (B) is 0.50×10^-3 to 1.00×10^-2. Accordingly, a polyvinyl acetal can be provided from which a film that has lower coloring due to heat and less foreign matters (undissolved fractions) can be obtained.

Description

Polyvinyl acetal and interlayer film for laminated glass containing the same

The present invention relates to polyvinyl acetal. The present invention also relates to an interlayer film for laminated glass containing the polyvinyl acetal, and a laminated glass using the interlayer film.

Polyvinyl acetal is obtained by an acetalization reaction in water under acidic conditions using polyvinyl alcohol (hereinafter sometimes abbreviated as “PVA”) and an aldehyde compound. Polyvinyl acetal films are used in various applications because they are tough and have a unique structure that has both hydrophilic hydroxy groups and hydrophobic acetal groups. Various polyvinyl acetals have been proposed. Yes. Among them, polyvinyl formal produced from PVA and formaldehyde, polyvinyl acetal in a narrow sense produced from PVA and acetaldehyde, and polyvinyl butyral produced from PVA and butyraldehyde occupy commercially important positions.

In particular, polyvinyl butyral is widely used as an interlayer film for laminated glass of automobiles and buildings, and occupies a particularly important position commercially.

On the other hand, polyvinyl acetal has a problem that it is easily colored by heating; a foreign substance (undissolved part) is likely to be generated in the polyvinyl acetal film. Various proposals have been made to solve these problems.

Patent Documents

1 and 2 describe a method for suppressing coloring of polyvinyl acetal by acetalization at a specific hydroxide ion concentration under high temperature and high pressure. Patent Document 3 describes a method of suppressing coloring of the obtained polyvinyl acetal by adding a reducing agent after neutralization by acetalization reaction. However, foreign matters were liable to occur in the film produced using the polyvinyl acetal obtained by the methods described in Patent Documents 1 to 3. Patent Document 4 describes a method of suppressing the generation of coarse particles by adjusting the concentration of the obtained resin particle slurry in the neutralization reaction after the acetalization reaction. Patent Document 5 describes a method for suppressing the generation of coarse particles by defining the relationship between an acid catalyst and a surfactant used in the acetalization reaction. However, foreign matters were likely to be generated in the film produced using the polyvinyl acetal obtained by the methods described in

Patent Documents

4 and 5. Moreover, the film was easily colored by heating. For these reasons, there is a strong demand for polyvinyl acetals in which all the above-mentioned problems are solved.

In particular, from the standpoint of recent energy saving and effective use of resources, improving the yield of the entire film manufacturing process is a very important issue. From the viewpoint of improving the yield, it is important to reuse the end material (trim) at the end of the film that is generated during film production. However, a trim in which foreign matter (undissolved part) or the like is mixed causes a defect and cannot be reused in practice. Further, when the trim is reused, the obtained film is easily colored because it receives heat history by melt extrusion molding a plurality of times. From such a point, the solution of the above-described problem is also demanded.

JP 2011-219670 A JP 2011-219671 A Japanese Patent Laid-Open No. 05-140211 JP-A-5-155915 JP 2002-069126 A

An object of the present invention is to provide a polyvinyl acetal capable of obtaining a film with little coloring due to heating and less foreign matter (undissolved content) and a method for producing the same. Moreover, it aims at providing the laminated glass using the polyvinyl acetal composition containing the said polyvinyl acetal, the intermediate film for laminated glasses which consists of the said composition, and the said intermediate film.

The above-mentioned problem is a polyvinyl acetal having an acetalization degree of 40 to 90 mol%, a vinyl ester monomer unit content of 0.1 to 20 mol%, and a viscosity average polymerization degree of 200 to 5000, which is 230 ° C. The molecular weight of the polyvinyl acetal heated for 3 hours in gel permeation chromatography (hereinafter sometimes abbreviated as GPC) and the peak molecular weight (A) measured with a differential refractive index detector and the spectrophotometric detection The peak molecular weight (B) measured with a vessel (measurement wavelength 280 nm) is the following formula (1)
(AB) / A <0.60 (1)
And a polyvinyl acetal having an absorbance at a peak molecular weight (B) of 0.50 × 10 ⁻³ to 1.00 × 10 ⁻² is solved.

However, in the GPC measurement,
Mobile phase: 20 mmol / l sodium trifluoroacetate-containing hexafluoroisopropanol (hereinafter, hexafluoroisopropanol may be abbreviated as HFIP.)
Sample concentration: 1.00 mg / ml
Sample injection volume: 100 μl
Column: Showa Denko "GPC HFIP-806M"
Column temperature: 40 ° C
Flow rate: 1 ml / min Absorbance detector cell length: 10 mm
It is.

In the GPC measurement, the peak molecular weight (A) measured with a differential refractive index detector and the peak molecular weight (C) measured with an absorptiometric detector (measurement wavelength: 320 nm) are expressed by the following formula (2).
(AC) / A <0.65 (2)
And the absorbance at the peak molecular weight (C) is preferably 0.35 × 10 ⁻³ to 4.50 × 10 ⁻³ . In the GPC measurement, the ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the polyvinyl acetal obtained by a differential refractive index detector is preferably 2.8 to 12.0.

It is preferable that the polyvinyl acetal is polyvinyl butyral.

A polyvinyl acetal composition containing the polyvinyl acetal of the present invention and a plasticizer is a preferred embodiment of the present invention. Here, the plasticizer is preferably triethylene glycol-di-2-ethylhexanoate.

An interlayer film for laminated glass made of the polyvinyl acetal composition is also a preferred embodiment of the present invention. A laminated glass formed by bonding a plurality of glass plates using the interlayer film for laminated glass is also a preferred embodiment of the present invention.

The above-mentioned problem is a method for producing the polyvinyl acetal for acetalizing polyvinyl alcohol, wherein the polyvinyl alcohol has a saponification degree of 50 to 99.99 mol%, a viscosity average polymerization degree of 200 to 5000, and an alkali metal of a carboxylic acid. Measured with a differential refractive index detector when the content of salt is 0.5% by mass or less in terms of the mass of alkali metal and the polyvinyl alcohol heated at 120 ° C. for 3 hours is measured by gel permeation chromatography. The peak top molecular weight (D) and the peak top molecular weight (E) measured with an absorptiometric detector (measurement wavelength 280 nm) are the following formula (3)
(DE) / D <0.75 (3)
And a manufacturing method characterized in that the absorbance at the peak top molecular weight (E) is 0.25 × 10 ⁻³ to 3.00 × 10 ⁻³ .

The polyvinyl acetal of the present invention can obtain a film with little coloring by heating and less foreign matter (undissolved content). A film produced using such a polyvinyl acetal has less foreign matter (undissolved content) and is less colored by heating. Therefore, since the trim etc. which generate | occur | produce when manufacturing a film using the said polyvinyl acetal etc. can be reused, a yield improves. Moreover, the interlayer film for laminated glass obtained by using the polyvinyl acetal composition containing the polyvinyl acetal has little foreign matter (undissolved content) and is less colored by heating. Therefore, a laminated glass is manufactured with high productivity by using the interlayer film for laminated glass. According to the production method of the present invention, the polyvinyl acetal can be easily produced.

In the polyvinyl acetal of Example 1, the relationship between the molecular weight and the value measured by the differential refractive index detector (RI), and the relationship between the molecular weight and the absorbance measured by the absorptiometric detector (UV) (measurement wavelength 280 nm). It is the graph which showed. In PVA-1 of Example 1, the relationship between the molecular weight and the value measured by the differential refractive index detector (RI), and the molecular weight and the absorbance measured by the absorptiometric detector (UV) (measurement wavelength 280 nm). It is the graph which showed the relationship.

The polyvinyl acetal of the present invention is a polyvinyl acetal having an acetalization degree of 50 to 85 mol%, a vinyl ester monomer unit content of 0.1 to 20 mol%, and a viscosity average polymerization degree of 200 to 5000. When the polyvinyl acetal heated at 230 ° C. for 3 hours is measured by GPC, the peak molecular weight (A) measured with a differential refractive index detector and the peak molecular weight measured with an absorptiometric detector (measurement wavelength 280 nm) (B) is the following formula (1)
(AB) / A <0.60 (1)
And the absorbance at the peak molecular weight (B) is 0.50 × 10 ⁻³ to 1.00 × 10 ⁻² .

However, in the GPC measurement,
Mobile phase: HFIP containing 20 mmol / l sodium trifluoroacetate
Sample concentration: 1.00 mg / ml
Sample injection volume: 100 μl
Column: Showa Denko "GPC HFIP-806M"
Column temperature: 40 ° C
Flow rate: 1 ml / min Absorbance detector cell length: 10 mm
It is.

In the GPC measurement in the present invention, a GPC apparatus having a differential refractive index detector and an absorptiometric detector and capable of simultaneously performing measurement by these detectors is used. The absorptiometric detector needs to be capable of measuring absorbance at a wavelength of 280 nm, and preferably is capable of simultaneously measuring absorbance at a wavelength of 280 nm and absorbance at a wavelength of 320 nm. A cell having a cell length (optical path length) of 10 mm is used as the cell of the detection unit of the absorptiometer. The absorptiometric detector may measure the absorption of ultraviolet light having a specific wavelength, or may measure the absorption of ultraviolet light having a specific range of wavelengths. The polyvinyl acetal subjected to the measurement is separated into each molecular weight component by a GPC column. The signal intensity by the differential refractive index detector is approximately proportional to the polyvinyl acetal concentration (mg / ml). On the other hand, polyvinyl acetal detected by an absorptiometric detector is only one having absorption at a predetermined wavelength. By the GPC measurement, it is possible to measure the concentration and absorbance at a predetermined wavelength for each molecular weight component of polyvinyl acetal.

HFIP containing sodium trifluoroacetate at a concentration of 20 mmol / l is used as the solvent and mobile phase used for dissolving the polyvinyl acetal measured in the GPC measurement. HFIP can dissolve polyvinyl acetal and polymethyl methacrylate (hereinafter abbreviated as PMMA). Further, by adding sodium trifluoroacetate, adsorption of polyvinyl acetal to the column filler is prevented. The flow rate in the GPC measurement is 1 ml / min, and the column temperature is 40 ° C.

In the GPC measurement, monodisperse PMMA (hereinafter referred to as standard PMMA) is used as a standard. Several types of standard PMMA with different molecular weights are measured, and a calibration curve is created from the GPC elution volume and the molecular weight of the standard PMMA. In the present invention, a calibration curve created using the detector is used for measurement by the differential refractive index detector, and a calibration curve created using the detector is used for measurement by the absorptiometric detector. Using these calibration curves, the GPC elution volume is converted into the molecular weight, and the peak top molecular weight (A) and the peak top molecular weight (B) are determined.

Before the GPC measurement, the polyvinyl acetal is heated at 230 ° C. for 3 hours. In the present invention, polyvinyl acetal is heated by the following method. In order to clearly reflect the difference in hue of the sample after the heat treatment in the difference in absorbance, the polyvinyl acetal (film) heated by pressing the polyvinyl acetal powder at 2 MPa and 230 ° C. for 3 hours. Get. The thickness of the film at this time is 600 to 800 μm, and is preferably about 760 μm, which is the thickness of a normal laminated glass interlayer film.

* A heated polyvinyl acetal is dissolved in the above-mentioned solvent to obtain a measurement sample. The concentration of polyvinyl acetal in the measurement sample is 1.00 mg / ml, and the injection volume is 100 μl. However, when the viscosity average polymerization degree of the polyvinyl acetal exceeds 2400, the excluded volume increases, and therefore the polyvinyl acetal concentration may not be measured with good reproducibility at a concentration of 1.00 mg / ml. In that case, an appropriately diluted sample (injection amount 100 μl) is used. Absorbance is proportional to the concentration of polyvinyl acetal. Therefore, the absorbance when the polyvinyl acetal concentration is 1.00 mg / ml is determined using the concentration of the diluted sample and the actually measured absorbance.

FIG. 1 shows the relationship between the molecular weight obtained by GPC measurement of polyvinyl acetal and the value measured by the differential refractive index detector, and the molecular weight and the absorptiometric detector (measurement wavelength). It is the graph which showed the relationship with the light absorbency measured by 280 nm. The GPC measurement in the present invention will be further described with reference to FIG. In FIG. 1, the chromatogram represented by “RI” is a plot of values measured by a differential refractive index detector against the molecular weight (horizontal axis) of polyvinyl acetal converted from the elution volume. In the present invention, the molecular weight at the peak position in the chromatogram is defined as peak top molecular weight (A). When there are a plurality of peaks in the chromatogram, the molecular weight at the peak position where the peak height is the highest is the peak top molecular weight (A).

In FIG. 1, the chromatogram indicated by “UV” is a plot of the absorbance measured with an absorptiometric detector (measurement wavelength 280 nm) against the molecular weight (horizontal axis) of polyvinyl acetal converted from the elution volume. is there. In the present invention, the molecular weight at the peak position in the chromatogram is defined as peak top molecular weight (B). When there are a plurality of peaks in the chromatogram, the molecular weight at the peak position where the peak height is the highest is the peak top molecular weight (B).

The polyvinyl acetal of the present invention has a peak top molecular weight (A) measured with a differential refractive index detector and a peak top measured with an absorptiometric detector (measurement wavelength 280 nm) when GPC measurement is performed by the above-described method. The molecular weight (B) satisfies the following formula (1).
(AB) / A <0.60 (1)

The peak top molecular weight (A) is a value that serves as an index of the molecular weight of polyvinyl acetal. On the other hand, the peak top molecular weight (B) is derived from a component present in polyvinyl acetal and having absorption at 280 nm. Usually, since the peak top molecular weight (A) is larger than the peak top molecular weight (B), (AB) / A becomes a positive value. As the peak top molecular weight (B) increases, (AB) / A decreases, and as the peak top molecular weight (B) decreases, (AB) / A increases. That is, when (AB) / A is large, it means that there are many components that absorb ultraviolet rays having a wavelength of 280 nm in the low molecular weight components in the polyvinyl acetal.

When (A−B) / A is 0.60 or more, as described above, the low molecular weight component contains more components that absorb ultraviolet light having a wavelength of 280 nm. In this case, it is difficult to improve the coloring of the obtained polyvinyl acetal and the foreign matter (undissolved content) in the film produced using the polyvinyl acetal in a well-balanced manner. Therefore, the reuse of film (trim etc.) is hindered. (AB) / A is preferably less than 0.55, more preferably less than 0.50.

The polyvinyl acetal of the present invention must have an absorbance (measurement wavelength of 280 nm) at a peak top molecular weight (B) of 0.50 × 10 ⁻³ to 1.00 × 10 ⁻² when GPC measurement is performed by the above-described method. There is. When the absorbance is less than 0.50 × 10 ⁻³ , foreign matter (undissolved content) in the film produced using polyvinyl acetal increases. On the other hand, when the absorbance exceeds 1.00 × 10 ⁻² , the resulting polyvinyl acetal and a film produced using the same are colored. The absorbance is preferably 1.00 × 10 ⁻³ to 8.00 × 10 ^{−3, and} more preferably 1.50 × 10 ⁻³ to 6.50 × 10 ⁻³ .

From the viewpoint of excellent balance of suppression of coloring of the obtained polyvinyl acetal and reduction of foreign matter (undissolved content) in the film produced using the polyvinyl acetal, it is measured by a differential refractive index detector in the GPC measurement. The peak top molecular weight (A) and the peak top molecular weight (C) measured by an absorptiometric detector (measurement wavelength: 320 nm) are expressed by the following formula (2).
(AC) / A <0.65 (2)
It is preferable to satisfy.

The peak top molecular weight (C) is measured in the same manner as the peak top molecular weight (B) except that the measurement wavelength in the absorptiometric detector is 320 nm. A peak top molecular weight (C) originates in the component which has absorption in 320 nm which exists in polyvinyl acetal. Usually, since the peak top molecular weight (A) is larger than the peak top molecular weight (C), (AC) / A becomes a positive value. As the peak top molecular weight (C) increases, (AC) / A decreases, and as the peak top molecular weight (C) decreases, (AC) / A increases. That is, when (AC) / A is large, it means that the low molecular weight component in the polyvinyl acetal contains many components that absorb ultraviolet light having a wavelength of 320 nm.

When (AC) / A is 0.65 or more, as described above, the low molecular weight component contains more components that absorb ultraviolet light having a wavelength of 320 nm. In this case, there is a possibility that balance between suppression of coloring of the obtained polyvinyl acetal and reduction of foreign matters (undissolved content) in a film produced using the polyvinyl acetal cannot be achieved. (AC) / A is more preferably less than 0.60, and still more preferably less than 0.55.

The polyvinyl acetal of the present invention has an absorbance (measurement wavelength of 320 nm) at a peak top molecular weight (C) of 0.35 × 10 ⁻³ to 4.50 × 10 ⁻³ when GPC measurement is performed by the method described above. Is preferred. When the absorbance is less than 0.35 × 10 ⁻³ , foreign matter (undissolved content) in the film produced using polyvinyl acetal may increase. On the other hand, when the absorbance exceeds 4.50 × 10 ⁻³ , the resulting polyvinyl acetal and a film produced using the same may be easily colored. The absorbance is more preferably 0.50 × 10 ⁻³ to 3.50 × 10 ⁻³ , and further preferably 1.00 × 10 ⁻³ to 2.50 × 10 ⁻³ .

In the polyvinyl acetal of the present invention, the ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the polyvinyl acetal obtained by a differential refractive index detector in the GPC measurement is 2.8 to 12.0. Preferably there is. Mw and Mn are determined from the chromatogram obtained by plotting the values measured by the differential refractive index detector with respect to the molecular weight of the polyvinyl acetal described above. Mw and Mn in the present invention are values in terms of PMMA.

Generally, Mn is an average molecular weight that is strongly influenced by a low molecular weight component, and Mw is an average molecular weight that is strongly influenced by a high molecular weight component. Mw / Mn is generally used as an index of molecular weight distribution of a polymer. When Mw / Mn is small, it indicates that the polymer has a small proportion of low molecular weight component, and when Mw / Mn is large, it indicates that the polymer has a large proportion of low molecular weight component.

Therefore, in the present invention, when Mw / Mn is less than 2.8, it indicates that the proportion of the low molecular weight component is small in the polyvinyl acetal. When Mw / Mn is less than 2.8, foreign matter (undissolved content) in the film produced using polyvinyl acetal may increase. Mw / Mn is more preferably 2.9 or more, and further preferably 3.1 or more. On the other hand, when Mw / Mn exceeds 12.0, it shows that the ratio of a low molecular weight component is large in polyvinyl acetal. When Mw / Mn exceeds 12.0, the obtained polyvinyl acetal or a film produced using the same may be easily colored. Mw / Mn is more preferably 11.0 or less, and even more preferably 8.0 or less.

The degree of acetalization of the polyvinyl acetal of the present invention is 40 to 90 mol%, preferably 50 to 85 mol%, more preferably 55 to 82 mol%, still more preferably 60 to 78 mol%, particularly preferably 65. ~ 75 mol%. When the degree of acetalization is less than 40 mol%, the compatibility with a plasticizer or the like decreases. Moreover, there exists a possibility that the foreign material (undissolved part) in the film manufactured using polyvinyl acetal may increase. On the other hand, when the degree of acetalization exceeds 90 mol%, the efficiency of the acetalization reaction is significantly reduced. Moreover, there exists a possibility that the polyvinyl acetal obtained and the film manufactured using it may become colored easily.

The degree of acetalization represents the ratio of the acetalized vinyl alcohol monomer unit to the total monomer units constituting the polyvinyl acetal. Among the vinyl alcohol monomer units in the raw material PVA, those that are not acetalized remain in the resulting polyvinyl acetal as vinyl alcohol monomer units.

The viscosity average polymerization degree of the polyvinyl acetal of the present invention is represented by the viscosity average polymerization degree of the raw material PVA measured according to JIS-K6726. That is, after re-saponifying and purifying PVA to a saponification degree of 99.5 mol% or more, it can be obtained from the intrinsic viscosity [η] measured in water at 30 ° C. by the following equation. The viscosity average polymerization degree of PVA and the viscosity average polymerization degree of polyvinyl acetal obtained by acetalizing it are substantially the same.
P = ([η] × 10000 / 8.29) ^{(1 / 0.62)}

The viscosity average polymerization degree of the polyvinyl acetal of the present invention is 200 to 5,000. When the viscosity average degree of polymerization is less than 200, practical strength of polyvinyl acetal cannot be obtained. Therefore, the strength of the film produced using polyvinyl acetal is insufficient. Moreover, it becomes difficult to industrially manufacture PVA used for manufacture of such a polyvinyl acetal. The viscosity average degree of polymerization is preferably 250 or more, more preferably 300 or more, and still more preferably 400 or more. On the other hand, when the viscosity average degree of polymerization exceeds 5000, the melt viscosity becomes too high and molding becomes difficult. The viscosity average degree of polymerization is preferably 4500 or less, more preferably 4000 or less, and further preferably 3500 or less.

When the polyvinyl acetal of the present invention is used for a laminated glass interlayer film, the viscosity average polymerization degree is preferably 500 to 5000, more preferably 800 to 3500, and further preferably 1000 to 2500. When the degree of polymerization is less than 500, there is a possibility that sufficient strength as an interlayer film for laminated glass cannot be obtained. On the other hand, when the viscosity average polymerization degree exceeds 5000, the melt viscosity becomes too high and film formation becomes difficult.

The content of the vinyl ester monomer unit of the polyvinyl acetal of the present invention is 0.1 to 20 mol%, preferably 0.3 to 18 mol%, more preferably 0.5 to 15 mol%. More preferably, it is 0.7 to 13 mol%. When the content of the vinyl ester monomer unit is less than 0.1 mol%, the polyvinyl acetal cannot be stably produced and the film cannot be formed. On the other hand, when the content of the vinyl ester monomer unit exceeds 20 mol%, the obtained polyvinyl acetal and a film produced using the polyvinyl acetal may be easily colored.

The content of monomer units other than acetalized monomer units, vinyl ester monomer units and vinyl alcohol monomer units in the polyvinyl acetal of the present invention is preferably 20 mol% or less, more preferably Is 10 mol% or less.

The polyvinyl acetal of the present invention is usually produced by acetalizing PVA.

The saponification degree of the raw material PVA is preferably 80 to 99.99 mol%, more preferably 82 to 99.7 mol%, still more preferably 85 to 99.5 mol%, and most preferably 87 to 99.3 mol%. Mol%. If the degree of saponification is less than 80 mol%, there is a risk that foreign matter (undissolved content) in the film produced using polyvinyl acetal will increase, and the resulting polyvinyl acetal and the film produced using it will be colored. May be easier. On the other hand, when the degree of saponification exceeds 99.9 mol%, PVA may not be produced stably. The degree of saponification of PVA is measured according to JIS-K6726.

Examples of vinyl ester monomers used for the production of raw material PVA include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and versa. Examples thereof include vinyl tick acid, and vinyl acetate is particularly preferable.

The raw material PVA can also be produced by polymerizing vinyl ester monomers in the presence of thiol compounds such as 2-mercaptoethanol, n-dodecyl mercaptan, mercaptoacetic acid, 3-mercaptopropionic acid, and saponifying the resulting polyvinyl ester. You can also By this method, PVA in which a functional group derived from a thiol compound is introduced at the terminal is obtained.

Examples of the method for polymerizing the 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 the methods, a bulk polymerization method performed without a solvent or a solution polymerization method performed using a solvent such as alcohol is usually employed. In terms of enhancing the effect of the present invention, a solution polymerization method in which polymerization is performed together with a lower alcohol is preferable. The lower alcohol is not particularly limited, but an alcohol having 3 or less carbon atoms such as methanol, ethanol, propanol and isopropanol is preferable, and methanol is usually used. When performing the polymerization reaction by the bulk polymerization method or the solution polymerization method, the reaction can be carried out by either a batch method or a continuous method. Examples of the initiator used in the polymerization reaction include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), 2,2′-azobis (4-methoxy). Azo initiators such as -2,4-dimethylvaleronitrile); organic peroxide initiators such as benzoyl peroxide, n-propyl peroxycarbonate, peroxydicarbonate, etc., within a range that does not impair the effects of the present invention. Known initiators may be mentioned, and organic oxide-based initiators having a half-life of 10 to 110 minutes at 60 ° C. are particularly preferable, and peroxydicarbonate is particularly preferable. There is no particular limitation on the polymerization temperature for carrying out the polymerization reaction, but a range of 5 ° C to 200 ° C is suitable.

When the vinyl ester monomer is radically polymerized, a copolymerizable monomer can be copolymerized as necessary as long as the effects of the present invention are not impaired. Examples of such a monomer 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 acid 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 methacrylamide derivatives 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-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 a sulfonic acid group 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 Monomers having vinyl; vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethyl Monomers having a silyl group such as toxisilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, 3- (meth) acrylamide-propyltrimethoxysilane, 3- (meth) acrylamide-propyltriethoxysilane Etc. The amount of monomers that can be copolymerized with these vinyl ester monomers varies depending on the purpose and application of use, but is usually based on all monomers used for copolymerization. The ratio is 20 mol% or less, preferably 10 mol% or less.

PVA can be obtained by saponifying the polyvinyl ester obtained by the above method in an alcohol solvent.

As the catalyst for the saponification reaction of polyvinyl ester, an alkaline substance is usually used, and examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. The amount of the alkaline substance used is preferably in the range of 0.002 to 0.2, in the range of 0.004 to 0.1, in terms of molar ratio based on the vinyl ester monomer unit of the polyvinyl ester. It is particularly preferred that 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, and dimethylformamide. Of these solvents, methanol is preferably used. At this time, the water content of methanol is preferably adjusted to 0.001 to 1% by mass, more preferably 0.003 to 0.9% by mass, and particularly preferably 0.005 to 0.8% by mass.

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

The alkaline substance containing an alkali metal added during the saponification reaction is usually neutralized by an ester such as methyl acetate generated by the progress of the saponification reaction, or neutralized by a carboxylic acid such as acetic acid added after the reaction. At this time, an alkali metal salt of a carboxylic acid such as sodium acetate is formed. As will be described later, in the present invention, the raw material PVA preferably contains an alkali metal salt of carboxylic acid in an amount of 0.5% by mass or less in terms of the mass of the alkali metal. In order to obtain such PVA, the PVA may be washed after saponification.

Examples of the cleaning liquid used in this case include a lower alcohol such as methanol, a solution composed of 100 parts by weight of the lower alcohol and 20 parts by weight or less of water, and a solution composed of the lower alcohol and an ester such as methyl acetate produced in the saponification step. It is done. The content of the ester in the solution composed of the lower alcohol and the ester is not particularly limited, but is preferably 1000 parts by mass or less with respect to 100 parts by mass of the lower alcohol. The amount of the cleaning liquid added is preferably 100 parts by mass to 10000 parts by mass, more preferably 150 parts by mass to 5000 parts by mass with respect to 100 parts by mass of the gel obtained by saponification and swollen with PVA by alcohol. Part by mass to 1000 parts by mass is more preferable. When the addition amount of the cleaning liquid is less than 100 parts by mass, the alkali metal salt amount of the carboxylic acid may exceed the above range. On the other hand, when the addition amount of the cleaning liquid exceeds 10,000 parts by mass, the improvement of the cleaning effect by increasing the addition amount cannot be expected. Although there is no particular limitation on the washing method, for example, a step of adding a gel (PVA) and a washing solution into a tank and stirring or standing at 5 to 100 ° C. for about 5 to 180 minutes and then removing the liquid is performed. A batch method that repeats until the content of the alkali metal salt is within a predetermined range may be mentioned. Further, there is a continuous method in which PVA is continuously added from the top of the column at the same temperature and for the same time as the batch method, and a lower alcohol is continuously added from the bottom of the column, and the two are brought into contact with each other.

The raw material PVA preferably contains an alkali metal salt of carboxylic acid. The content is preferably 0.50% by mass or less, more preferably 0.37% by mass or less, still more preferably 0.28% by mass or less, and particularly preferably 0.23% by mass or less in terms of alkali metal mass. is there. When content of the alkali metal salt of carboxylic acid exceeds 0.5 mass%, the obtained polyvinyl acetal or a film produced using the same may be easily colored. The content of alkali metal salt of carboxylic acid (calculated in terms of alkali metal mass) is obtained from the amount of alkali metal ions obtained by ashing PVA with a platinum crucible and then measuring the resulting ash content by ICP emission analysis. Can do.

Examples of the alkali metal salt of carboxylic acid include those obtained by neutralizing an alkali catalyst used in the above-described saponification step, for example, sodium hydroxide, potassium hydroxide, sodium methylate with carboxylic acid, and a vinyl ester described later. Carboxylic acid added for the purpose of suppressing alcoholysis of the vinyl ester monomer such as vinyl acetate used in the polymerization step is neutralized in the saponification step, added to stop radical polymerization When a carboxylic acid having a conjugated double bond is used as an inhibitor, those obtained by neutralizing the carboxylic acid in the saponification step or those intentionally added are included. Specific examples include sodium acetate, potassium acetate, sodium propionate, potassium propionate, sodium glycerate, potassium glycerate, sodium malate, potassium malate, sodium citrate, potassium citrate, sodium lactate, potassium lactate, tartaric acid Sodium, potassium tartrate, sodium salicylate, potassium salicylate, sodium malonate, potassium malonate, sodium succinate, potassium succinate, sodium maleate, potassium maleate, sodium phthalate, potassium phthalate, sodium oxalate, potassium oxalate , Sodium glutarate, potassium glutarate, sodium abietic acid, potassium abietic acid, sodium sorbate, potassium sorbate, 2,4,6-octatri Sodium 1,1-carboxylate,

potassium

2,4,6-octatriene-1-carboxylate, sodium eleostearate, potassium eleostearate,

sodium

2,4,6,8-decatetraene-1-

carboxylate

2,4,6,8-decatetraene-1-carboxylate, sodium retinoate, potassium retinoate and the like, but are not limited thereto.

In the present invention, a method of adjusting each value obtained by GPC measurement so as to fall within the above-described range includes a method of using specific PVA as a raw material for polyvinyl acetal.

Such a raw material PVA has a saponification degree of 50 to 99.99 mol%, a viscosity average polymerization degree of 200 to 5000, and an alkali metal salt content of carboxylic acid of 0.5% by mass or less in terms of the mass of the alkali metal. When the PVA heated at 120 ° C. for 3 hours is subjected to GPC measurement, the peak top molecular weight (D) measured by a differential refractive index detector and an absorptiometric detector (measurement wavelength 280 nm) The peak top molecular weight (E) measured by the following formula (3)
(DE) / D <0.75 (3)
And the absorbance at the peak top molecular weight (E) is preferably 0.25 × 10 ⁻³ to 3.00 × 10 ⁻³ . GPC measurement at this time is performed in the same manner as the GPC measurement method for polyvinyl acetal described above, except that PVA heated under the following conditions is measured instead of polyvinyl acetal.

After casting an aqueous solution in which PVA powder is dissolved, it is dried at 20 ° C. and 65% RH to obtain a PVA film. The PVA film has a thickness of 30 to 75 μm, preferably 40 to 60 μm. In order to clearly reflect the difference in hue of the sample after heat drying in the difference in ultraviolet absorption, the film is heated at 120 ° C. for 3 hours using a hot air dryer. From the viewpoint of suppressing heat treatment errors between samples, a gear oven is preferable as the hot air dryer. The PVA thus heated is subjected to GPC measurement.

The peak top molecular weight (D) of the PVA is determined in the same manner as the peak top molecular weight (A) of the polyvinyl acetal described above, and the peak top molecular weight (E) of the raw material PVA is the peak top molecular weight (B) of the polyvinyl acetal described above. Find in the same way as

The PVA has a peak top molecular weight (D) measured by a differential refractive index detector and a peak top molecular weight (E) measured by an absorptiometric detector (measurement wavelength 280 nm) when GPC measurement is performed by the above-described method. ) Preferably satisfies the following formula (3).
(DE) / D <0.75 (3)

The peak top molecular weight (D) is a value serving as an index of the molecular weight of PVA. On the other hand, the peak top molecular weight (E) is derived from a component present in PVA and having absorption at 280 nm. Usually, since the peak top molecular weight (D) is larger than the peak top molecular weight (E), (DE) / D becomes a positive value. As the peak top molecular weight (E) increases, (DE) / D decreases, and as the peak top molecular weight (E) decreases, (DE) / D increases. That is, when (DE) / D is large, it means that there are many components that absorb UV light having a wavelength of 280 nm among low molecular weight components in PVA.

When (DE) / D is 0.75 or more, as described above, the low molecular weight component contains more components that absorb ultraviolet light having a wavelength of 280 nm. In this case, there is a possibility that the foreign matter of the film manufactured using the obtained polyvinyl acetal or polyvinyl acetal increases. (DE) / D is more preferably less than 0.70, and still more preferably less than 0.65.

The PVA preferably has an absorbance (measurement wavelength: 280 nm) at a peak top molecular weight (E) of 0.25 × 10 ⁻³ to 3.00 × 10 ⁻³ when GPC measurement is performed by the method described above. When the absorbance is less than 0.25 × 10 ⁻³ , foreign matter (undissolved content) in the film produced using polyvinyl acetal may increase. On the other hand, when the absorbance exceeds 3.00 × 10 ⁻³ , the obtained polyvinyl acetal and a film produced using the polyvinyl acetal may be easily colored. The absorbance is preferably 0.50 × 10 ⁻³ to 2.80 × 10 ^{−3, and} more preferably 0.75 × 10 ⁻³ to 2.50 × 10 ⁻³ .

The PVA has a peak top molecular weight (D) measured by a differential refractive index detector and a peak top molecular weight (F) measured by an absorptiometric detector (measurement wavelength: 320 nm) when GPC measurement is performed by the method described above. It is more preferable that the following formula (4) is satisfied.
(DF) / D <0.75 (4)

The peak top molecular weight (F) is measured in the same manner as the peak top molecular weight (E) except that the measurement wavelength in the absorptiometric detector is 320 nm. The peak top molecular weight (F) is derived from a component having absorption at 320 nm, which is present in the raw material PVA. Usually, since the peak top molecular weight (D) is larger than the peak top molecular weight (F), (DF) / D becomes a positive value. As the peak top molecular weight (F) increases, (DF) / D decreases, and as the peak top molecular weight (F) decreases, (DF) / D increases. That is, when (D−F) / D is large, it means that the low molecular weight component in PVA contains many components that absorb ultraviolet rays having a wavelength of 320 nm.

When (D−F) / D is 0.75 or more, as described above, the low molecular weight component contains more components that absorb ultraviolet light having a wavelength of 320 nm. In this case, there is a possibility that the foreign matter of the film manufactured using the obtained polyvinyl acetal or polyvinyl acetal increases. (D−F) / D is more preferably less than 0.70, and particularly preferably less than 0.65.

More preferably, the PVA has an absorbance (measurement wavelength: 320 nm) at a peak top molecular weight (F) of 0.20 × 10 ⁻³ to 2.90 × 10 ⁻³ when GPC measurement is performed by the method described above. . When the absorbance is less than 0.20 × 10 ⁻³ , foreign matter (undissolved content) in a film produced using polyvinyl acetal may increase. On the other hand, when the absorbance exceeds 2.90 × 10 ⁻³ , the resulting polyvinyl acetal and a film produced using the same may be easily colored. The absorbance is more preferably 0.40 × 10 ⁻³ to 2.70 × 10 ⁻³ , and particularly preferably 0.60 × 10 ⁻³ to 2.40 × 10 ⁻³ .

In the GPC measurement, the ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the PVA, which is determined by a differential refractive index detector, is preferably 2.2 to 6.0. Mw and Mn are obtained from a chromatogram obtained by plotting the value measured by the differential refractive index detector with respect to the molecular weight of PVA used when obtaining the peak top molecular weight (D) described above. Therefore, Mw and Mn calculated | required here are the values of standard PMMA conversion.

When Mw / Mn is less than 2.2, it indicates that the proportion of low molecular weight components is small in PVA. When Mw / Mn is less than 2.2, there is a possibility that foreign matter (undissolved content) in the film produced using polyvinyl acetal increases. It is more preferable that Mw / Mn is 2.3 or more. On the other hand, when Mw / Mn exceeds 6.0, it shows that the ratio of a low molecular weight component is large in PVA. When Mw / Mn exceeds 6.0, the obtained polyvinyl acetal and a film produced using the same may be easily colored. Mw / Mn is more preferably 3.5 or less, and further preferably 3.0 or less.

The absorbance at the peak top molecular weight (D), the peak top molecular weight (E), the peak top molecular weight (E), the peak top molecular weight (F), and the absorbance at the peak top molecular weight (F) of the PVA so that the above-mentioned conditions are satisfied. Examples of the adjustment method include the following methods.

A) A vinyl ester monomer from which a radical polymerization inhibitor contained in the raw material vinyl ester monomer has been removed in advance is used for polymerization.

B) A vinyl ester monomer having a total content of impurities contained in the raw material vinyl ester monomer of preferably 1 to 1200 ppm, more preferably 3 to 1100 ppm, and even more preferably 5 to 1000 ppm is used for radical polymerization. Impurities include aldehydes such as acetaldehyde, crotonaldehyde, and acrolein; acetals such as acetaldehyde dimethyl acetal, crotonaldehyde dimethyl acetal, and acrolein dimethyl acetal obtained by acetalizing the aldehyde with a solvent alcohol; ketones such as acetone; methyl acetate and ethyl acetate And esters.

C) In order to suppress the alcoholysis and hydrolysis of the monomer by alcohol and a small amount of water in a series of steps of radical polymerization of the raw material vinyl ester monomer in an alcohol solvent and collecting and reusing unreacted monomer, Organic acids, specifically hydroxycarboxylic acids such as glycolic acid, glyceric acid, malic acid, citric acid, lactic acid, tartaric acid, salicylic acid; malonic acid, succinic acid, maleic acid, phthalic acid, oxalic acid, glutaric acid, etc. A carboxylic acid or the like is added to suppress the generation of aldehydes such as acetaldehyde generated by decomposition as much as possible. The addition amount of the organic acid is preferably 1 to 500 ppm, more preferably 3 to 300 ppm, and still more preferably 5 to 100 ppm with respect to the raw material vinyl ester monomer.

D) As the solvent used for the polymerization, a solvent having a total impurity content of preferably 1 to 1200 ppm, more preferably 3 to 1100 ppm, and still more preferably 5 to 1000 ppm. Examples of the impurities contained in the solvent include those described above as the impurities contained in the raw material vinyl ester monomer.

E) When the radical polymerization of the vinyl ester monomer, the ratio of the solvent to the vinyl ester monomer is increased.

F) An organic peroxide is used as a radical polymerization initiator used for radical polymerization of a vinyl ester monomer. Organic peroxides include acetyl peroxide, isobutyl peroxide, diisopropyl peroxycarbonate, diallyl peroxydicarbonate, di-n-propyl peroxydicarbonate, dimyristyl peroxydicarbonate, di (2-ethoxyethyl) peroxide Examples include oxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, di (methoxyisopropyl) peroxydicarbonate, and di (4-tert-butylcyclohexyl) peroxydicarbonate. It is preferable to use peroxydicarbonate with a period of 10 to 110 minutes.

G) When an inhibitor is added after radical polymerization of the vinyl ester monomer in order to suppress the polymerization, an inhibitor of 5 molar equivalents or less is added to the remaining undecomposed radical polymerization initiator. Examples of the inhibitor include a compound having a conjugated double bond having a molecular weight of 1000 or less and a compound that stabilizes a radical and inhibits a polymerization reaction. Specifically, isoprene, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-t-butyl-1,3-butadiene, 1,3-pentadiene, , 3-dimethyl-1,3-pentadiene, 2,4-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-pentadiene, 3-ethyl-1,3-pentadiene, 2-methyl-1 , 3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 2,5-dimethyl-2,4-hexadiene, , 3-octadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-methoxy-1,3-butadiene, 2-methoxy-1,3-butadiene, 1-ethoxy-1,3- Tadiene, 2-ethoxy-1,3-butadiene, 2-nitro-1,3-butadiene, chloroprene, 1-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-bromo-1, Conjugated dienes comprising a conjugated structure of two carbon-carbon double bonds such as 3-butadiene, fulvene, tropone, osymene, ferrandrene, myrcene, farnesene, semblene, sorbic acid, sorbic acid ester, sorbic acid salt, abietic acid; Conjugated triene having a conjugated structure of three carbon-carbon double bonds such as 1,3,5-hexatriene, 2,4,6-octatriene-1-carboxylic acid, eleostearic acid, tung oil, cholecalciferol Carbons such as cyclooctatetraene, 2,4,6,8-decatetraene-1-carboxylic acid, retinol, retinoic acid, etc. Polyenes such as conjugated polyene consisting Motoni double bond of four or more conjugated structure. Any one having a plurality of stereoisomers such as 1,3-pentadiene, myrcene, and farnesene may be used. Further, p-benzoquinone, hydroquinone, hydroquinone monomethyl ether, 2-phenyl-1-propene, 2-phenyl-1-butene, 2,4-diphenyl-4-methyl-1-pentene, 3,5-diphenyl-5 Methyl-2-heptene, 2,4,6-triphenyl-4,6-dimethyl-1-heptene, 3,5,7-triphenyl-5-ethyl-7-methyl-2-nonene, 1,3- Diphenyl-1-butene, 2,4-diphenyl-4-methyl-2-pentene, 3,5-diphenyl-5-methyl-3-heptene, 1,3,5-triphenyl-1-hexene, 2,4 , 6-triphenyl-4,6-dimethyl-2-heptene, 3,5,7-triphenyl-5-ethyl-7-methyl-3-nonene, 1-phenyl-1,3-butadiene, 1,4 -The Aromatic compounds such as Eniru 1,3-butadiene.

H) A polyvinyl ester alcohol solution from which the remaining vinyl ester monomer is removed as much as possible is used for the saponification reaction. Preferably, the residual monomer removal rate is 99% or more, more preferably 99.5% or more, still more preferably 99.8% or more.

The desired PVA can be obtained by appropriately combining A) to H). The PVA thus obtained is preferably acetalized to obtain the polyvinyl acetal of the present invention.

The acetalization of PVA can be performed, for example, under the following reaction conditions, but is not limited thereto. PVA is dissolved in water by heating to 80 to 100 ° C., and then gradually cooled over 10 to 60 minutes to obtain a 3 to 40% by mass aqueous solution of PVA. When the temperature falls to −10 to 30 ° C., an aldehyde and an acid catalyst are added to the aqueous solution, and an acetalization reaction is performed for 30 to 300 minutes while keeping the temperature constant. At that time, polyvinyl acetal having reached a certain degree of acetalization is precipitated. Thereafter, the temperature of the reaction solution is raised to 25 to 80 ° C. over 30 to 300 minutes, and the temperature is maintained for 10 minutes to 24 hours (this temperature is set as the reaction temperature at the time of driving). Next, a neutralizing agent such as an alkali is added to the reaction solution as necessary to neutralize the acid catalyst, and the resultant is washed with water and dried to obtain polyvinyl acetal.

Generally, aggregated particles made of polyvinyl acetal are generated in such a reaction or processing step, and coarse particles are easily formed. When such coarse particles are generated, there is a risk of causing variation between batches. On the other hand, when the above-mentioned specific PVA is used as a raw material, the generation of coarse particles is suppressed as compared with the conventional product, and as a result, when the resulting polyvinyl acetal is melt-formed, foreign matter (undissolved content) is further reduced. Film can be obtained.

The acid catalyst used in the acetalization reaction is not particularly limited, and any of organic acids and inorganic acids can be used. For example, acetic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, hydrochloric acid and the like can be mentioned. Of these, hydrochloric acid, sulfuric acid, and nitric acid are preferably used. In general, when nitric acid is used, the reaction rate of the acetalization reaction is increased, and improvement in productivity can be expected. On the other hand, the obtained polyvinyl acetal particles tend to be coarse and the variation between batches tends to increase. is there. On the other hand, when the above-mentioned specific PVA is used as a raw material, the formation of coarse particles is suppressed, and as a result, when the resulting polyvinyl acetal is melt-formed, a film with reduced foreign matter (undissolved content) is obtained. Obtainable.

In the present invention, the aldehyde used for the acetalization reaction is not particularly limited, but a known aldehyde having 1 to 8 carbon atoms is preferable, an aldehyde having 4 to 6 carbon atoms is more preferable, and n-butyraldehyde is particularly preferably used. In the present invention, polyvinyl acetal obtained by using two or more aldehydes in combination can also be used.

A polyvinyl acetal composition containing the polyvinyl acetal of the present invention and a plasticizer is a preferred embodiment of the present invention. The plasticizer is not particularly limited as long as the effects of the present invention are not impaired and there is no problem in compatibility with polyvinyl acetal. As the plasticizer, a mono- or diester of an oligoalkylene glycol having a hydroxyl group at both ends and a carboxylic acid, a diester of a dicarboxylic acid and a hydroxyl group-containing compound, or the like can be used. These can be used alone or in combination of two or more. Examples of oligoalkylene glycols having hydroxyl groups at both ends include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propylene glycol, 1,2-propylene glycol dimer and trimer, 1,3 -Propylene glycol, 1,3-propylene glycol dimer and trimer, 1,2-butylene glycol, 1,2-butylene glycol dimer and trimer, 1,4-butylene glycol, 1, 4-butylene glycol dimer and trimer, 1,2-hexanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol, 1,8-octane Diol, 1,9-nonanediol, 2-methyl-1,8-octanediol, , 2-decanediol, 1,4-cyclohexane diol. Examples of the carboxylic acid include acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid and decanoic acid. Here, the combination of oligoalkylene glycol and carboxylic acid is arbitrary, and may be a combination of a plurality of oligoalkylene glycols and a plurality of carboxylic acids. Of these, monoesters and diesters of triethylene glycol and 2-ethylhexanoic acid are preferable from the viewpoint of handleability (volatility during molding). Triethylene glycol-di-2-ethylhexanoate is particularly preferable. Dicarboxylic acids include alkylene dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and sebacic acid, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid. An acid etc. are mentioned. Examples of the hydroxyl group-containing compound include methanol, ethanol, propanol, butanol, pentanol, hexanol, cyclohexanol, heptanol, octanol, 2-ethylhexanol, nonaol, decanol, 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, Examples include 2-butoxyethanol. Here, the combination of dicarboxylic acid and a hydroxyl-containing compound is arbitrary, and the combination of several dicarboxylic acid and several hydroxyl-containing compound may be sufficient.

The addition amount of the plasticizer in the composition is not particularly limited, but is preferably 0 to 200 parts by mass, more preferably 2 to 150 parts by mass, and further preferably 5 to 100 parts by mass with respect to 100 parts by mass of the polyvinyl acetal. Part. When the added amount of the plasticizer exceeds 200 parts by mass, the plasticizer may easily bleed out. In particular, when the composition is used as a raw material for an interlayer film for laminated glass, the amount of the plasticizer added is preferably 5 to 100 parts by weight, more preferably 10 to 90 parts by weight, more preferably 100 parts by weight of polyvinyl acetal. The amount is preferably 15 to 80 parts by mass. When the plasticizer addition amount is less than 5 parts by mass, desired flexibility as an interlayer film for laminated glass may not be obtained. If it exceeds 100 parts by mass, the desired mechanical properties, particularly the penetration resistance of the laminated glass, may decrease.

The polyvinyl acetal composition of the present invention may contain an antioxidant, an ultraviolet absorber, an adhesion improver, a pigment, a dye, and other conventionally known additives, as long as not departing from the gist of the present invention.

The type of the antioxidant is not particularly limited, and examples thereof include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, phenolic antioxidants are preferable, alkyl Substituted phenolic antioxidants are particularly preferred.

Examples of phenolic antioxidants include 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2,4-di-t-amyl- Acrylate compounds such as 6- (1- (3,5-dit-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate, 2,6-dit-butyl-4-methylphenol, 2,6-dit -Butyl-4-ethylphenol, octadecyl-3- (3,5-) di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis (4-methyl-6-t-butylphenol), 4,4′-butylidene-bis (4-methyl-6-tert-butylphenol), 4,4′-butylidene-bis (6-tert-butyl-m-cresol), 4,4′-thiobi (3-methyl-6-tert-butylphenol), bis (3-cyclohexyl-2-hydroxy-5-methylphenyl) methane, 3,9-bis (2- (3- (3-tert-butyl-4-hydroxy) -5-methylphenyl) propionyloxy) -1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 1,1,3-tris (2-methyl-4- Hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene-3- ( 3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate) methane, triethylene glycol bis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) Alkyl-substituted phenolic compounds such as propionate), 6- (4-hydroxy-3,5-di-t-butylanilino) -2,4-bis-octylthio-1,3,5-triazine, 6- (4-hydroxy- 3,5-dimethylanilino) -2,4-bis-octylthio-1,3,5-triazine, 6- (4-hydroxy-3-methyl-5-t-butylanilino) -2,4-bis-octylthio Triazine group-containing phenolic compounds such as 1,3,5-triazine, 2-octylthio-4,6-bis- (3,5-di-t-butyl-4-oxyanilino) -1,3,5-triazine Is mentioned.

Examples of phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2-t-butyl). -4-methylphenyl) phosphite, tris (cyclohexylphenyl) phosphite, 2,2-methylenebis (4,6-dit-butylphenyl) octyl phosphite, 9,10-dihydro-9-oxa-10-phos Phaphenanthrene-10-oxide, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9 , 10-Dihydro-9-oxa-10-phospha Monophosphite compounds such as enanthrene, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-ditridecyl phosphite), 4,4′-isopropylidene-bis (phenyl-dialkyl (C12 To C15) phosphite), 4,4′-isopropylidene-bis (diphenylmonoalkyl (C12 to C15) phosphite), 1,1,3-tris (2-methyl-4-ditridecyl phosphite-5- and diphosphite compounds such as t-butylphenyl) butane and tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylene phosphite. Of these, monophosphite compounds are preferred.

Examples of the sulfur-based antioxidant include

dilauryl

3,3′-thiodipropionate,

distearyl

3,3′-thiodipropionate,

lauryl stearyl

3,3′-thiodipropionate, pentaerythritol-tetrakis- (Β-lauryl-thiopropionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane.

These antioxidants can be used alone or in combination of two or more. The blending amount of the antioxidant is not particularly limited, but is preferably 0.001 to 5 parts by mass, more preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the polyvinyl acetal.

Moreover, the polyvinyl acetal composition of the present invention may contain an ultraviolet absorber. Examples of the ultraviolet absorber used include 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-3,5-bis (α, α'dimethylbenzyl) phenyl) -2H-benzo Triazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- ( 3,5-di-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-amyl-2-hydroxyphenyl) benzotriazole, 2- (2 ′ -Hydroxy-5′-t-octylphenyl) benzotriazole UV absorbers such as benzotriazole; 2,2,6,6-tetramethyl-4-pi Peridylbenzoate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -2- (3,5-di t-butyl-4-hydroxybenzyl) -2-n-butylmalonate, 4- (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) -1- (2- (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) ethyl) hindered amine UV absorbers such as 2,2,6,6-tetramethylpiperidine; 2,4-di-t-butylphenyl- Benzoate UV absorbers such as 3,5 di-t-butyl-4-hydroxybenzoate and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate; malonic acid [(4-me Kishifeniru) - methylene] - malonic acid ester ultraviolet absorbers such as dimethyl ester, 2-ethyl-2'-ethoxy - such as oxalic acid anilide-based ultraviolet absorbers such oxalanilide like. These ultraviolet absorbers can be used alone or in combination of two or more. The content of the ultraviolet absorber in the polyvinyl acetal composition is not particularly limited, but the total amount of the ultraviolet absorber is preferably 10 to 50,000 ppm on a mass basis, and is in the range of 100 to 10,000 ppm. Is more preferable. If the addition amount is less than 10 ppm, sufficient effects may not be exhibited, and even if the addition amount is more than 50,000 ppm, the improvement of the effect by increasing the content cannot be expected.

The glass transition temperature of the polyvinyl acetal composition of the present invention is not particularly limited and can be appropriately selected depending on the purpose, but is preferably in the range of 0 to 50 ° C, more preferably 0 to 45 ° C. The temperature is more preferably 0 to 40 ° C. In particular, when the polyvinyl acetal composition of the present invention is formed into a sheet and used as a laminated glass interlayer, the glass transition temperature is preferably within the above range.

An interlayer film for laminated glass made of the polyvinyl acetal composition is also a preferred embodiment of the present invention. When the interlayer film for laminated glass of the present invention is used for an application where it is necessary to appropriately adjust the adhesiveness with glass, the polyvinyl acetal composition may contain an adhesiveness adjusting agent. As the adhesion adjusting agent, conventionally known ones can be used. For example, acetic acid, propionic acid, butanoic acid, hexanoic acid, 2-ethylbutanoic acid, sodium salt of organic acid such as 2-ethylhexanoic acid, potassium salt, A magnesium salt or the like is used. These can be used alone or in combination of two or more. The optimum content of the adhesion modifier varies depending on the adhesion modifier used, but the adhesion of the resulting film to glass is determined by the Pummel test (described in International Publication No. WO2003 / 033583). In general, it is preferable to adjust to 3 to 10. In particular, when high penetration resistance is required, the content is preferably adjusted to 3 to 6, and when high glass scattering prevention property is required, the content is adjusted to 7 to 10. It is preferable. When high glass scattering prevention property is required, it is also a useful method not to add an adhesion modifier. Usually, the content of the adhesion adjusting agent in the polyvinyl acetal composition is preferably 0.0001 to 1% by mass, more preferably 0.0005 to 0.1% by mass, and 0.001 to 0.00%. 03 mass% is still more preferable.

Further, as another adjusting agent for adjusting the adhesiveness, a silane coupling agent can be mentioned. The content of the silane coupling agent in the polyvinyl acetal composition is preferably 0.01 to 5% by mass.

The interlayer film for laminated glass of the present invention is excellent in transparency and flexibility. The thickness of the interlayer film for laminated glass is not particularly limited, but is preferably 0.05 to 5.0 mm, more preferably 0.1 to 2.0 mm, and 0.1 to 1.2 mm. More preferably.

The interlayer film for laminated glass comprising the polyvinyl acetal composition is obtained by forming a polyvinyl acetal composition obtained by mixing the polyvinyl acetal, the plasticizer, and other components by a conventionally known method. Can do. For example, a method in which the polyvinyl acetal, a plasticizer and other components dissolved or dispersed in an organic solvent are formed into a film, and then the organic solvent is distilled off; the other components are converted into a plasticizer using an extruder or the like. Examples include a method of melt-kneading a dissolved or dispersed material together with polyvinyl acetal to form a film. Among known film forming methods, a method of forming a film using an extruder is particularly preferably used. The resin temperature at the time of extrusion is preferably 150 to 250 ° C, more preferably 170 to 230 ° C. When the resin temperature becomes too high, polyvinyl acetal is decomposed, and the content of volatile substances in the intermediate film after film formation increases. On the other hand, if the temperature is too low, the removal of volatile matter in the extruder becomes insufficient, and the content of volatile substances in the intermediate film after film formation increases. In order to efficiently remove the volatile substance, it is preferable to remove the volatile substance from the vent port by reducing the pressure in the extruder.

In the production of the interlayer film for laminated glass of the present invention, as a raw material polyvinyl acetal, only virgin resin (not containing recycled polyvinyl acetal) may be used. May be used. Usually, film formation is carried out, for example, in a film forming apparatus in which an extruder is equipped with a measuring machine such as a gear pump and a die such as a T die. Generally, in film formation, both ends (trims) of a film (used as an interlayer film for laminated glass) are cut off. It is very important to collect and reuse such trims from the viewpoints of energy saving, effective utilization of resources and improvement of yield. In addition, an off-spec product produced during the production of a film having irregularities on the surface is useful because it can be reused in the same manner as the trim. In the polyvinyl acetal of the present invention, the formation of coarse particles is suppressed during the acetalization reaction, and as a result, when the obtained polyvinyl acetal is melt-formed, a film with reduced foreign matter (undissolved content) is obtained. Can do. Since the film obtained from the polyvinyl acetal of the present invention is less colored when heat-treated, the trim and off-spec products can be effectively reused. Retrieving the trim or off-spec film that has been collected on the roll as a method of re-feeding the collected trim or off-spec film to the extruder; Examples include a method in which a spec product wound on a roll is cut into a certain size and then re-entered into an extruder. Further, when the interlayer film for laminated glass of the present invention is formed, the ratio of the virgin resin and the recovered film (virgin resin: recovered film) in the raw material can be arbitrarily changed between 0: 100 and 100: 0.

When reusing the trim or off-spec film, adjust the amount of plasticizer and other components by analyzing the newly obtained film components and adjusting the amount added to the extruder. However, a desired film can be obtained.

The shape of the surface of the interlayer film for laminated glass of the present invention is not particularly limited. However, in consideration of the handling property (foaming property) when laminating with glass, the surface in contact with the glass is conventionally known, such as melt fracture and embossing. It is preferable that the concavo-convex structure is formed by the method. The emboss height is not particularly limited, but is preferably 5 μm to 500 μm, more preferably 7 μm to 300 μm, and still more preferably 10 μm to 200 μm. When the embossing height is less than 5 μm, bubbles formed between the glass and the intermediate film may not be efficiently removed when laminating to glass, and when it exceeds 500 μm, it is difficult to form embossing. Moreover, although embossing may be given to the single side | surface of an intermediate film, and both sides may be sufficient, it is preferable to give normally to both surfaces.

The embossed concavo-convex pattern is not particularly limited as long as it satisfies the specific conditions described above, and may be regularly distributed or randomly distributed.

In order to form such embossing, the embossing roll method, the profile extrusion method,
An extrusion lip embossing method using a melt fracture is employed. In particular, the embossing roll method is suitable for stably obtaining an embossed film on which uniform and fine irregularities are formed.

The embossing roll used in the embossing roll method can be produced by, for example, using an engraving mill (mother mill) having a desired concavo-convex pattern and transferring the concavo-convex pattern onto the surface of the metal roll. It can also be produced using laser etching. Further, after forming a fine concavo-convex pattern on the roll surface as described above, blasting is performed on the surface using an abrasive such as aluminum oxide, silicon oxide, or glass beads to form a finer concavo-convex pattern. You can also.

Also, the embossing roll used in the embossing roll method is preferably subjected to a release treatment. When a roll without mold release treatment is used, troubles that cannot be peeled off from the roll easily occur depending on conditions. For the release treatment, known techniques such as silicone treatment, Teflon (registered trademark) treatment, plasma treatment and the like can be used.

A laminated glass obtained by bonding a plurality of glass plates using the interlayer film for laminated glass of the present invention is a preferred embodiment of the present invention. The laminated glass of the present invention can be produced by sandwiching the interlayer film of the present invention between at least two glass plates and heating and bonding the interlayer film. The glass used for the laminated glass of the present invention is not particularly limited. In addition to inorganic glass such as float plate glass, tempered plate glass, polished plate glass, mold plate glass, netted plate glass, heat ray absorbing plate glass, and the like such as polymethyl methacrylate and polycarbonate A well-known organic glass etc. can be used. These may be colorless, colored, transparent or non-transparent. Moreover, these may be used independently and may use 2 or more types together. Although the thickness of glass is not specifically limited, It is preferable that it is 100 mm or less. The shape of the glass is not particularly limited, and may be a simple flat plate glass or a glass having a curvature such as an automobile windshield.

The laminated glass of the present invention can be produced by a conventionally known method, and examples thereof include a method using a vacuum laminator device, a method using a vacuum bag, a method using a vacuum ring, and a method using a nip roll. Further, there is a method in which the obtained laminate is put into an autoclave after being temporarily pressed using these methods.

In the case of using a vacuum laminator, an example of the production conditions is as follows. The glass and the interlayer film are heated at a temperature of 100 to 200 ° C., particularly 130 to 160 ° C. under a reduced pressure of 1 × 10 ⁻⁶ to 3 × 10 ⁻² MPa. Laminated. A method using a vacuum bag or a vacuum ring is described in, for example, European Patent No. 1235683, and is laminated at 130 to 145 ° C. under a pressure of about 2 × 10 ⁻² MPa, for example.

As a production method using a nip roll, there is a method in which after degassing with a roll at a temperature not higher than the flow start temperature of the polyvinyl acetal composition, press bonding is performed at a temperature close to the flow start temperature. Specifically, for example, there is a method of heating to 30 to 70 ° C. with an infrared heater or the like, then degassing with a roll, further heating to 50 to 120 ° C., and then pressing with a roll.

When pressure bonding is performed using the above-described method, and then further pressure bonding is performed, the operating conditions of the autoclave process are appropriately selected depending on the thickness and configuration of the laminated glass. For example, 1.0 to 1.5 MPa The treatment is preferably carried out at a temperature of 130 to 145 ° C. for 0.5 to 3 hours under pressure.

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 “%” are based on mass unless otherwise specified. “Polymerization degree” means “viscosity average polymerization degree”.

[GPC measurement]
(Preparation of PVA)
After heating at 95 ° C. for 1 hour to dissolve PVA in water, it was cooled to room temperature to obtain a 2% aqueous solution of PVA. The obtained aqueous solution was cast on a polyethylene terephthalate film (20 cm × 20 cm) and dried for 1 week under the conditions of 20 ° C. and 65% RH to obtain a PVA film having a thickness of 50 μm. The obtained film was fixed to a stainless steel metal frame (20 cm × 20 cm and 1 cm wide metal frame) with a clip, and heat-treated in a gear oven at 120 ° C. for 3 hours. A sample was collected from the vicinity of the center of the PVA film after heat treatment and subjected to GPC measurement.

(Preparation of polyvinyl acetal)
A polyvinyl acetal film having a thickness of 760 μm was obtained by hot pressing the polyvinyl acetal powder at a pressure of 2 MPa at 230 ° C. for 3 hours and then cooling. A sample was collected from near the center of the heat-treated film and subjected to GPC measurement.

(measuring device)
GPC measurement was performed using “GPCmax” manufactured by VISCOTECH. As a differential refractive index detector, “TDA305” manufactured by VISCOTECH was used. “UV Detector 2600” manufactured by VISCOTECH was used as an ultraviolet-visible absorption detector. The optical path length of the detection cell of the absorptiometric detector is 10 mm. As the GPC column, “GPC HFIP-806M” manufactured by Showa Denko KK was used. Moreover, OmniSEC (Version 4.7.0.406) attached to the apparatus was used as analysis software.

(Measurement condition)
A sample prepared by the above-described method was dissolved in 20 mmol / l sodium trifluoroacetate-containing hexafluoroisopropanol (hereinafter abbreviated as “HFIP”) to prepare a 1.00 mg / ml solution of PVA. The solution was filtered through a 0.45 μm polytetrafluoroethylene filter and used for measurement.

As the mobile phase, 20 mmol / l sodium trifluoroacetate-containing HFIP was used. The mobile phase flow rate was 1.0 ml / min. The sample injection amount was 100 μl, and measurement was performed at a GPC column temperature of 40 ° C.

In addition, the sample in which the viscosity average polymerization degree of PVA exceeded 2400 performed GPC measurement using the sample (100 microliters) diluted suitably. The absorbance at a sample concentration of 1.00 mg / ml was calculated from the measured value according to the following formula. α (mg / ml) is the concentration of the diluted sample.

Absorbance at a sample concentration of 1.00 mg / ml = (1.00 / α) × measured value of absorbance

(Create a calibration curve)
As a standard, polymethyl methacrylate (hereinafter abbreviated as “PMMA”) manufactured by Agilent Technologies (peak top molecular weight: 1944000, 790000, 467400, 271400, 144000, 79250, 35300, 13300, 7100, 1960, 1020, 690) And a calibration curve for converting the elution volume into the PMMA molecular weight was prepared for each of the differential refractive index detector and the absorptiometric detector. The analytical software was used to create each calibration curve. In this measurement, a column in a state where the peaks of the standard samples having both molecular weights of 1944000 and 271400 can be separated in the measurement of polymethyl methacrylate was used.

In this apparatus, the peak intensity obtained from the differential refractive index detector is mV (millivolt), and the peak intensity obtained from the UV detector is represented by absorbance (abs unit: Absorbance unit).

[Synthesis of polyvinyl acetate]
PVAc-1
A 6 L separable flask equipped with a stirrer, thermometer, nitrogen introduction tube, and reflux tube was deoxygenated in advance, and vinyl acetate monomer (VAM) 2555 g containing 500 ppm acetaldehyde (AA) and 50 ppm acetaldehyde dimethyl acetal (DMA). 945 g of methanol (MeOH) containing 50 ppm of acetaldehyde dimethyl acetal and an acetaldehyde content of less than 1 ppm; 1% methanol solution of tartaric acid in an amount of 20 ppm of tartaric acid in the vinyl acetate monomer was charged. While blowing nitrogen into the flask, the temperature inside the flask was adjusted to 60 ° C. Note that an ethylene glycol / water solution at −10 ° C. was circulated in the reflux tube. A 0.55% by mass methanol solution of di-n-propyl peroxydicarbonate was prepared, and 18.6 mL was added to the flask to initiate polymerization. At this time, the amount of di-n-propyl peroxydicarbonate added was 0.081 g. A methanol solution of di-n-propyl peroxydicarbonate was sequentially added at a rate of 20.9 mL / hour until the completion of polymerization. During the polymerization, the temperature in the flask was kept at 60 ° C. Four hours after the start of the polymerization, when the solid content concentration of the polymerization solution reached 25.1%, 0.0141 g of sorbic acid (3% of di-n-propyl peroxydicarbonate remaining undecomposed in the polymerization solution) was obtained. After adding 1200 g of contained methanol (corresponding to a molar equivalent), the polymerization solution was cooled to stop the polymerization. When the polymerization was stopped, the polymerization rate of the vinyl acetate monomer was 35.0%. After the polymerization solution was cooled to room temperature, the inside of the flask was depressurized using a water aspirator to distill off the vinyl acetate monomer and methanol, thereby precipitating polyvinyl acetate. 3000 g of methanol was added to the precipitated polyvinyl acetate, and the polyvinyl acetate was dissolved while heating at 30 ° C., and then the inside of the flask was decompressed again using a water aspirator to distill off the vinyl acetate monomer and methanol. Thus, polyvinyl acetate was precipitated. The operation of dissolving polyvinyl acetate in methanol and then precipitating it was further repeated twice. Methanol was added to the precipitated polyvinyl acetate to obtain a 40% by mass methanol solution of polyvinyl acetate (PVAc-1) with a vinyl acetate monomer removal rate of 99.8%.

The polymerization degree was measured using a part of the methanol solution of PVAc-1 obtained. A 10% methanol solution of sodium hydroxide was added to the methanol solution of PVAc-1 so that the molar ratio of sodium hydroxide to vinyl acetate units in polyvinyl acetate was 0.1. When the gelled product was formed, the gel was pulverized and subjected to Soxhlet extraction with methanol for 3 days. The obtained polyvinyl alcohol was dried and subjected to viscosity average polymerization degree measurement. The degree of polymerization was 1700.

PVAc-2 to PVAc-20
Polyvinyl acetate (PVAc-2 to PVAc-20) was obtained in the same manner as PVAc-1, except that the conditions were changed to those described in Table 1. In Table 1, “ND” means less than 1 ppm. The degree of polymerization of each polyvinyl acetate obtained was determined in the same manner as PVAc-1. The results are shown in Table 1.

[Synthesis of polyvinyl alcohol]
PVA-1
Water with respect to vinyl acetate monomer units in methanol and polyvinyl acetate so that the total solid concentration (saponification concentration) is 30% by mass with respect to a 40% by mass methanol solution of polyvinyl acetate in PVAc-1. An 8% methanol solution of sodium hydroxide was added with stirring so that the molar ratio of sodium oxide was 0.020, and the saponification reaction was started at 40 ° C. The gel is pulverized when the gelated product is generated as the saponification reaction proceeds, and the crushed gel is transferred to a container at 40 ° C. When 60 minutes have elapsed from the start of the saponification reaction, methanol / methyl acetate / water ( 25/70/5 mass ratio) solution and neutralized. The obtained swollen gel was centrifuged, and methanol twice as much as the swollen gel was added, immersed, left for 30 minutes, and then centrifuged four times, 60 ° C. for 1 hour, 100 PVA-1 was obtained by drying at 2 ° C. for 2 hours.

The polymerization degree and saponification degree of PVA-1 were determined by the method described in JIS-K6726. The degree of polymerization was 1700, and the degree of saponification was 99.1 mol%. These physical property data are also shown in Table 2.

After ashing PVA-1, the sodium acetate content of PVA-1 was determined by measuring the amount of sodium in the obtained ash using an ICP emission analyzer “IRIS AP” manufactured by Jarrel Ash. . The sodium acetate content was 0.7% (0.20% in terms of sodium). These physical property data are also shown in Table 2.

GPC measurement of PVA-1 was performed. FIG. 2 is a graph showing the relationship between molecular weight and the value measured with a differential refractive index detector (RI), and the relationship between molecular weight and the absorbance measured with an absorptiometric detector (measurement wavelength 280 nm) (UV). It is. The molecular weight at this time is one converted from the elution volume using a calibration curve (PMMA equivalent molecular weight). The peak top molecular weight (D) measured by the differential refractive index detector obtained from FIG. 2 was 100,000, and the peak top molecular weight (E) measured by the absorptiometric detector (280 nm) was 53,000. It was. The obtained value is expressed by the following formula (DE) / D
The value obtained by substituting for was 0.47. The absorbance (280 nm) at the peak top molecular weight (E) was 1.30 × 10 ⁻³ . The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn obtained from the chromatogram (RI) in FIG. 2 was 2.6. These results are also shown in Table 2.

The peak top molecular weight (F) measured with an absorptiometric detector (320 nm) obtained in the same manner as the method for obtaining the peak top molecular weight (E) was 50,000. The peak top molecular weight (D) and the peak top molecular weight (F) are expressed by the following formula (DF) / D
The value obtained by substituting for was 0.50. The absorbance (320 nm) at the peak top molecular weight (F) was 1.05 × 10 ⁻³ . These results are also shown in Table 2.

PVA-2-8, comparative PVA-1-5
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 2 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 2.

PVA-9, comparative PVA-6-8
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 3 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 3.

PVA-10, comparative PVA-9 and 10
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 4 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 4.

PVA-11, comparative PVA-11 and 12
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 5 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 5.

PVA-12, comparative PVA-13-15
Each PVA was synthesized in the same manner as in Example 1 except that the conditions were changed to those shown in Table 6. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 6.

PVA-13-19, comparative PVA-16-19
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 7 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 7.

PVA-20, comparative PVA-20 and 21
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 8 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 8.

Comparative PVA-22
Water with respect to vinyl acetate monomer units in methanol and polyvinyl acetate so that the total solid concentration (saponification concentration) is 40% by mass with respect to a 55% by mass methanol solution of polyvinyl acetate in PVAc-3. An 8% methanol solution of sodium hydroxide was added with stirring so that the molar ratio of sodium oxide was 0.005, and the saponification reaction was started at 40 ° C. Note that saponification reaction was performed by adding distilled water so that the water content in the system was 3.0%. One hour after adding the methanol solution of sodium hydroxide, 0.8 mol equivalent of 1% aqueous acetic acid and a large amount of distilled water were added to stop the saponification reaction. The resulting solution was transferred to a dryer, dried at 65 ° C. for 12 hours, and then dried at 100 ° C. for 2 hours to obtain Comparative PVA-22.

The polymerization degree, saponification degree, and sodium acetate content of comparative PVA-22 were measured in the same manner as PVA-1. The degree of polymerization was 300, the degree of saponification was 45.3 mol%, and the sodium acetate content was 1.2% (0.34% in terms of sodium). The results are shown in Table 8. Since Comparative PVA-22 was insoluble in water, film preparation for GPC measurement could not be performed, and GPC measurement could not be performed.

Comparative PVA-23
Water with respect to vinyl acetate monomer units in methanol and polyvinyl acetate so that the total solid concentration (saponification concentration) is 40% by mass with respect to a 55% by mass methanol solution of polyvinyl acetate in PVAc-3. An 8% methanol solution of sodium hydroxide was added with stirring so that the molar ratio of sodium oxide was 0.005, and the saponification reaction was started at 40 ° C. Note that saponification reaction was performed by adding distilled water so that the water content in the system was 1.2%. One hour after adding the methanol solution of sodium hydroxide, 0.8 mol equivalent of 1% aqueous acetic acid and a large amount of distilled water were added to stop the saponification reaction. The resulting solution was transferred to a dryer, dried at 65 ° C. for 12 hours, and then dried at 100 ° C. for 2 hours to obtain Comparative PVA-23.

The polymerization degree, saponification degree, and sodium acetate content of comparative PVA-23 were measured in the same manner as PVA-1. The degree of polymerization was 300, the degree of saponification was 60.2 mol%, and the sodium acetate content was 1.3% (0.36% in terms of sodium). GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 8.

PVA-21, comparative PVA-24 and 25
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 9 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 9.

PVA-22, comparative PVA-26 and 27
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 10 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 10.

PVA-23, comparative PVA-28 and 29
Each PVA was synthesized in the same manner as PVA-1, except that the conditions shown in Table 11 were changed. The polymerization degree, saponification degree, and sodium acetate content (sodium mass conversion) of the obtained PVA were measured in the same manner as PVA-1. GPC measurement was performed in the same manner as PVA-1. The results are shown in Table 11.

Example 1
A 10-liter glass container equipped with a reflux condenser, thermometer, and squid-type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-1 (PVA concentration 7.5%), and the content was raised to 95 ° C. Warm to completely dissolve the PVA. Next, the contents were gradually cooled to 10 ° C. over about 30 minutes while stirring at 120 rpm, and then 384 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid were added to the vessel, and a butyralization reaction was performed for 150 minutes. It was. Thereafter, the temperature was raised to 60 ° C. over 60 minutes, held at 60 ° C. for 120 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, the resin was washed again with ion-exchanged water and then dried to obtain polyvinyl butyral.

(Composition of polyvinyl butyral)
The degree of butyralization (degree of acetalization) of polyvinyl butyral, the content of vinyl acetate monomer units, and the content of vinyl alcohol monomer units were measured according to JIS K6728. The resulting polyvinyl butyral has a butyralization degree (acetalization degree) of 68.2 mol%, a vinyl acetate monomer unit content of 0.9 mol%, and a vinyl alcohol monomer unit content of 30. It was 9 mol%. The results are also shown in Table 12.

(GPC measurement)
GPC measurement of polyvinyl butyral was performed. As the measured polyvinyl butyral, polyvinyl acetal (film) heated by cooling the polyvinyl acetal powder at a pressure of 2 MPa at 230 ° C. for 3 hours and then cooling was used. FIG. 1 is a graph showing the relationship between molecular weight and the value measured with a differential refractive index detector (RI), and the relationship between molecular weight and the absorbance measured with an absorptiometric detector (measurement wavelength 280 nm) (UV). It is. The molecular weight at this time is one converted from the elution volume using a calibration curve (PMMA equivalent molecular weight). The peak top molecular weight (A) measured with the differential refractive index detector obtained from FIG. 1 was 90000, and the peak top molecular weight (B) measured with the absorptiometric detector (280 nm) was 68900. The obtained value is expressed by the following formula (AB) / A
The value obtained by substituting for was 0.23. The absorbance at the peak top molecular weight (B) was 2.21 × 10 ⁻³ . The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn obtained from the chromatogram (RI) in FIG. 1 was 3.4. These results are also shown in Table 2.

The peak top molecular weight (C) measured by an absorptiometric detector (320 nm) obtained in the same manner as the method for obtaining the peak top molecular weight (B) was 60000. The peak top molecular weight (A) and the peak top molecular weight (C) are expressed by the following formula (AC) / A
The value obtained by substituting for was 0.33. The absorbance at the peak top molecular weight (C) was 1.26 × 10 ⁻³ . These results are also shown in Table 12.

(Undissolved content in the film)
A synthetic polyvinyl acetal powder of 50 parts by mass and a plasticizer of 19 parts by mass of triethylene glycol di-2-ethylhexanoate were used at 170 ° C. using a lab plast mill “C model” manufactured by Toyo Seiki Seisakusho Co., Ltd. For 5 minutes at 50 rpm. During melt kneading, nitrogen (100 mL / min) was continuously blown into the container. The obtained kneaded material was hot-pressed at 150 ° C. and 5 MPa for 30 minutes to prepare a sheet having a thickness of 800 μm. The obtained sheet was sandwiched between two transparent glass plates (20 cm × 20 cm), and preliminary adhesion was performed by passing a press roll at 110 ° C. while extruding air between the glass plate and the sheet. The laminated body after the preliminary adhesion was allowed to stand at 135 ° C. and 1.2 MPa for 30 minutes in an autoclave to produce a laminated glass (20 sheets in total). The number of foreign matters in the laminated glass obtained using a magnifying glass was counted by visual observation. The total number of foreign substances in 20 laminated glasses was determined and evaluated according to the following criteria. The results are shown in Table 12.
A: 0 (pieces / 20 sheets)
B: 1 (20 pieces)
C: 2-3 (pieces / 20 pieces)
D: 4-8 (pieces / 20 pieces)
E: 9 or more (pieces / 20 sheets)

(Colorability of film)
A kneaded product of polyvinyl acetal and triethylene glycol-di-2-ethylhexanoate was obtained in the same manner as in the above “undissolved part in the film”. To 34.5 parts by mass of the obtained kneaded product, 25 parts by mass of a new polyvinyl acetal powder (the same as that used for the preparation of the kneaded product) and triethylene glycol di-2-ethylhexanoate as a plasticizer After adding 9.5 parts by mass, the mixture was melt-kneaded again using a lab plast mill under the same conditions as the above “undissolved content in the film”. The operation of adding polyvinyl acetal and triethylene glycol-di-2-ethylhexanoate to the kneaded product and then kneading was repeated three more times. After producing a sheet using the kneaded material thus obtained, a laminated glass using the sheet was produced. A sheet and a laminated glass were produced in the same manner as in the above “undissolved portion in the film” except that the kneaded product was changed. The yellowness of the laminated glass obtained here (using repeatedly heated polyvinyl acetal) and the laminated glass obtained using the above “undissolved portion in film” (using virgin polyvinyl acetal) ( YI) was measured, and the colorability was evaluated according to the following criteria based on the difference in yellowness (ΔYI) between the two. The measurement was performed according to JIS K 7105 using an SM color computer “SM-TH” manufactured by Suga Test Instruments Co., Ltd. The results are shown in Table 12.
A: Less than 0.3 B: 0.3 or more and less than 0.5 C: 0.5 or more and less than 1.0 D: 1.0 or more and less than 2.0 E: 2.0 or more

Examples 2-8
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 1 except that the raw material PVA was changed to that shown in Table 12. The results are shown in Table 12.

Example 9
Polyvinyl butyral was synthesized in the same manner as in Example 1 except that the amount of n-butyraldehyde added was changed to 271 g. The polyvinyl butyral obtained in the same manner as in Example 1 was evaluated except that the plasticizer was changed to dibutoxyethyl adipate in the evaluation of the undissolved content in the film and the evaluation of the colorability of the film. The results are shown in Table 12.

Example 10
Polyvinyl butyral was synthesized in the same manner as in Example 1 except that the amount of n-butyraldehyde added was changed to 320 g. The polyvinyl butyral obtained in the same manner as in Example 1 was evaluated except that the plasticizer was changed to dibutoxyethyl adipate in the evaluation of the undissolved content in the film and the evaluation of the colorability of the film. The results are shown in Table 12.

Example 11
Polyvinyl butyral was synthesized in the same manner as in Example 1 except that the amount of n-butyraldehyde added was changed to 362 g. The polyvinyl butyral obtained in the same manner as in Example 1 was evaluated except that the plasticizer was changed to dibutoxyethyl adipate in the evaluation of the undissolved content in the film and the evaluation of the colorability of the film. The results are shown in Table 12.

Example 12
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 1 except that the amount of n-butyraldehyde added was changed to 449 g. The results are shown in Table 12.

Example 13
A 10-liter glass container equipped with a reflux condenser, thermometer, and squid-type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-1 (PVA concentration 7.5%), and the content was raised to 95 ° C. Warm to completely dissolve the PVA. Next, the contents were gradually cooled to 10 ° C. over about 30 minutes while stirring at 120 rpm, and then 740 g of n-butyraldehyde and 810 mL of 20% hydrochloric acid were added to the vessel, and a butyralization reaction was performed for 150 minutes. It was. Thereafter, the temperature was raised to 80 ° C. over 90 minutes, kept at 80 ° C. for 16 hours, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, the resin was washed again with ion-exchanged water and then dried to obtain polyvinyl butyral. Polyvinyl butyral obtained in the same manner as in Example 1 was evaluated. The results are shown in Table 12.

Comparative Examples 1-5
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 1 except that the raw material PVA was changed to that shown in Table 12. The results are shown in Table 12.

Comparative Example 6
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 10 except that the raw material PVA was changed to Comparative PVA-1 and the addition amount of n-butyraldehyde was changed to 271 g. The results are shown in Table 12.

Comparative Example 7
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 10 except that the raw material PVA was changed to Comparative PVA-1. The results are shown in Table 12.

Comparative Example 8
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 12 except that the raw material PVA was changed to Comparative PVA-1. The results are shown in Table 12.

Comparative Example 9
Polyvinyl butyral was synthesized and evaluated in the same manner as in Comparative Example 6 except that the raw material PVA was changed to Comparative PVA-2. The results are shown in Table 12.

Comparative Example 10
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 10 except that the raw material PVA was changed to Comparative PVA-2. The results are shown in Table 12.

Comparative Example 11
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 12 except that the raw material PVA was changed to Comparative PVA-2. The results are shown in Table 12.

Table 12 shows the evaluation results of polyvinyl acetal using a completely saponified PVA having a polymerization degree of 1700 as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Examples 1-13) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, any performance of polyvinyl acetal (Comparative Examples 1 to 11) that did not satisfy the conditions defined in the present invention decreased.

Example 14
A 10-liter glass container equipped with a reflux condenser, thermometer, and squid type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-9 (PVA concentration 7.5%), and the contents were heated to 95 ° C. Thus, the PVA was completely dissolved. Next, the contents were gradually cooled to 1 ° C. over about 30 minutes while stirring at 120 rpm, and then 422 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid were added to the vessel, and a butyralization reaction was performed for 120 minutes. It was. Thereafter, the temperature was raised to 45 ° C. over 60 minutes, held at 45 ° C. for 120 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (degree of acetalization) was 68.1 mol%, the content of vinyl acetate monomer units was 1.1 mol%, and the content of vinyl alcohol monomer units was 30.8 mol%. It was. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 1 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, the amount of polyvinyl butyral powder used for kneading in the evaluation of “undissolved content in the film” was changed to 61.4 parts by mass, and the amount of triethylene glycol di-2-ethylhexanoate was 7.6. Changed to parts by mass. In the evaluation of “colorability of the film”, the amount of polyvinyl butyral powder added to the kneaded material was changed to 30.7 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 3 Changed to 8 parts by mass. The results are shown in Table 13.

Comparative Examples 12-14
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 14 except that the raw material PVA was changed to that shown in Table 13. The results are shown in Table 13.

Table 13 shows the evaluation results of polyvinyl acetal using a fully saponified PVA having a polymerization degree of 300 or 150 as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 14) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, in the polyvinyl acetal (Comparative Examples 12 and 13) that does not satisfy the conditions defined in the present invention, either performance deteriorated. In addition, the polyvinyl acetal having a polymerization degree of 150 (Comparative Example 14) having a polymerization degree smaller than the lower limit defined in the present invention was insufficient in any performance.

Example 15
A 10-liter glass container equipped with a reflux condenser, thermometer, and squid type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-10 (PVA concentration 7.5%), and the contents were raised to 95 ° C. Warm to completely dissolve the PVA. Next, the mixture was gradually cooled to 5 ° C. over about 30 minutes with stirring at 120 rpm, and 402 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid were added to carry out a butyralization reaction for 120 minutes. Thereafter, the temperature was raised to 50 ° C. over 60 minutes, held at 50 ° C. for 120 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The resulting polyvinyl butyral has a butyralization degree (acetalization degree) of 68.5 mol%, a vinyl acetate monomer unit content of 1.5 mol%, and a vinyl alcohol monomer unit content of 30. 0.0 mol%. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 1 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, in the evaluation of “undissolved content in the film”, the amount of polyvinyl butyral powder used for kneading was changed to 57.5 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 11. The amount was changed to 5 parts by mass. In the evaluation of “colorability of the film”, the amount of polyvinyl butyral powder added to the kneaded product was changed to 28.8 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 5 Changed to 8 parts by mass. The results are shown in Table 14.

Comparative Examples 15 and 16
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 15 except that the raw material PVA was changed to that shown in Table 14. The results are shown in Table 14.

Table 14 shows the evaluation results of polyvinyl acetal using a completely saponified PVA having a polymerization degree of 500 as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 15) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, any performance of the polyvinyl acetal (Comparative Examples 15 and 16) that did not satisfy the conditions defined in the present invention decreased.

Example 16
A 10-liter glass container equipped with a reflux condenser, thermometer, and squid-type stirring blade was charged with 8234 g of ion-exchanged water and 526 g of PVA-11 (PVA concentration 6.0%), and the contents were raised to 95 ° C. Warm to dissolve completely. Next, the contents were gradually cooled to 15 ° C. over about 30 minutes while stirring at 120 rpm, and then 307 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid were added to the vessel, and a butyralization reaction was performed for 120 minutes. It was. Thereafter, the temperature was raised to 60 ° C. over 60 minutes, held at 60 ° C. for 120 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral. The resulting polyvinyl butyral has a butyralization degree (acetalization degree) of 68.2 mol%, a vinyl acetate monomer unit content of 1.3 mol%, and a vinyl alcohol monomer unit content of 30. It was 5 mol%.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (degree of acetalization) was 68.2 mol%, the content of vinyl acetate monomer units was 1.3 mol%, and the content of vinyl alcohol monomer units was 30.5 mol%. It was. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 1 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, in the evaluation of “undissolved content in the film”, the amount of polyvinyl butyral powder used for kneading was changed to 46 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 23 parts by mass. changed. In the evaluation of “film colorability”, the amount of polyvinyl butyral powder added to the kneaded product was changed to 23 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 11.5. Changed to parts by mass. The evaluation results are shown in Table 15.

Comparative Examples 17 and 18
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 16 except that the raw material PVA was changed to that shown in Table 15. The results are shown in Table 15.

Table 15 shows the evaluation results of polyvinyl acetal using a completely saponified PVA having a polymerization degree of 2400 as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 16) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, any performance of polyvinyl acetal (Comparative Examples 17 and 18) that did not satisfy the conditions defined in the present invention decreased.

Example 17
A 10-liter glass container equipped with a reflux condenser, thermometer, and squid-type stirring blade was charged with 8322 g of ion-exchanged water and 438 g of PVA-12 (PVA concentration 5.0%), and the contents were raised to 95 ° C. Warm to completely dissolve the PVA. Next, the contents are gradually cooled to 20 ° C. over about 30 minutes while stirring at 120 rpm, and then 256 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid are added to the vessel, and a butyralization reaction is performed for 120 minutes. It was. Thereafter, the temperature was raised to 60 ° C. over 60 minutes, held at 60 ° C. for 120 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (degree of acetalization) was 68.1 mol%, the content of vinyl acetate monomer units was 1.5 mol%, and the content of vinyl alcohol monomer units was 30.4 mol%. It was. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 1 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, in the evaluation of “undissolved content in the film”, the amount of polyvinyl butyral powder used for kneading was changed to 40.6 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 28. The amount was changed to 4 parts by mass. In the evaluation of “film colorability”, the amount of polyvinyl butyral powder added to the kneaded product was changed to 20.3 parts by mass, and the amount of triethylene glycol di-2-ethylhexanoate was changed to 14 parts. Changed to 2 parts by mass. The evaluation results are shown in Table 16.

Comparative Examples 19-21
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 17 except that the raw material PVA was changed to that shown in Table 16. The results are shown in Table 16. However, in Comparative Example 21, in the evaluation of the undissolved content in the film and the colorability of the film, the torque was too high during the kneading in the lab plast mill, and the melt kneading could not be performed.

Table 16 shows the evaluation of polyvinyl acetal using a completely saponified PVA having a polymerization degree of 3600 or a polymerization degree of 5500 as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 17) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, any performance of the polyvinyl acetal (Comparative Examples 19 and 20) not satisfying the conditions defined in the present invention was lowered. Moreover, the polyvinyl acetal (comparative example 21) having a degree of polymerization exceeding 5000 could not be evaluated because the melt viscosity became too high to be melt kneaded by a lab plast mill.

Example 18
A 10 liter glass container equipped with a reflux condenser, thermometer and squid type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-13 (PVA concentration 7.5%), and the contents were raised to 95 ° C. Warm to dissolve completely. Next, the contents are gradually cooled to 15 ° C. over about 30 minutes while stirring at 120 rpm, and then 432 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid are added to the vessel, and a butyralization reaction is performed for 90 minutes. It was. Thereafter, the temperature was raised to 45 ° C. over 30 minutes, held at 45 ° C. for 180 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (degree of acetalization) was 74.1 mol%, the content of vinyl acetate monomer units was 8.1 mol%, and the content of vinyl alcohol monomer units was 17.8 mol%. It was. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 1 (GPC measurement, undissolved content in the film). At this time, the amount of polyvinyl butyral powder used for kneading is 40 parts by mass, the amount of triethylene glycol-di-2-ethylhexanoate is 24 parts by mass, the melt kneading temperature is 160 ° C., and the hot press temperature is 140 parts. Changed to ° C respectively. The results are shown in Table 17.

Furthermore, the polyvinyl acetal obtained by the following method was evaluated.

(Colorability of film)
A synthetic polyvinyl acetal powder of 40 parts by mass and a plasticizer of 24 parts by mass of triethylene glycol di-2-ethylhexanoate were used at 160 ° C. using a lab plast mill “C model” manufactured by Toyo Seiki Seisakusho Co., Ltd. For 5 minutes at 50 rpm. During melt kneading, nitrogen (100 mL / min) was continuously blown into the container. The obtained kneaded material was hot-pressed at 140 ° C. and 5 MPa for 30 minutes to prepare a sheet having a thickness of 800 μm (using only virgin polyvinyl acetal as a raw material resin). 32 parts by mass of the sheet, 20 parts by mass of polyvinyl butyral powder (virgin resin), and 12 parts by mass of triethylene glycol-di-2-ethylhexanoate were mixed. The obtained mixture was melt-kneaded again, and then the kneaded product was formed into a sheet. The operation of producing the sheet again using the obtained sheet as a part of the raw material was further repeated once. A laminated glass was produced using the sheet thus obtained. For comparison, a laminated glass using the above-described sheet using only virgin polyvinyl acetal as a raw material resin was also produced. These laminated glasses were produced in the same manner as in Example 1 except that the sheets were different. The yellowness (YI) of each laminated glass was measured, and the colorability was evaluated according to the following criteria based on the difference in yellowness (ΔYI) between the two. The measurement was performed according to JIS K 7105 using an SM color computer “SM-TH” manufactured by Suga Test Instruments Co., Ltd. The evaluation results are shown in Table 17.
A: Less than 0.5 B: 0.5 or more and less than 1.0 C: 1.0 or more and less than 2.0 D: 2.0 or more and less than 3.0 E: 3.0 or more

Examples 19-24
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 18 except that the raw material PVA was changed to that shown in Table 17. The results are shown in Table 17.

Example 25
Polyvinyl butyral was synthesized in the same manner as in Example 18 except that the amount of n-butyraldehyde added was changed to 225 g. Polyvinyl butyral obtained in the same manner as in Example 18 was evaluated except that the plasticizer was changed to dibutoxyethyl adipate in the evaluation of “undissolved content in the film” and the evaluation of “film colorability”. The results are shown in Table 17.

Example 26
Polyvinyl butyral was synthesized in the same manner as in Example 18 except that the amount of n-butyraldehyde added was changed to 269 g. Polyvinyl butyral obtained in the same manner as in Example 18 was evaluated except that the plasticizer was changed to dibutoxyethyl adipate in the evaluation of “undissolved content in the film” and the evaluation of “film colorability”. The results are shown in Table 17.

Example 27
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 18 except that the amount of n-butyraldehyde added was changed to 307 g. The results are shown in Table 17.

Example 28
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 18 except that the amount of n-butyraldehyde added was changed to 458 g. The results are shown in Table 17.

Example 29
A 10 liter glass container equipped with a reflux condenser, thermometer and squid type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-13 (PVA concentration 7.5%), and the contents were raised to 95 ° C. Warm to dissolve completely. Next, the content is gradually cooled to 15 ° C. over about 30 minutes while stirring at 120 rpm, 837 g of n-butyraldehyde and 810 mL of 20% hydrochloric acid are added to the vessel, and a butyralization reaction is performed for 90 minutes. It was. Thereafter, the temperature was raised to 60 ° C. over 60 minutes, kept at 60 ° C. for 24 hours, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral. The polyvinyl butyral obtained in the same manner as in Example 18 was evaluated. The results are shown in Table 17.

Comparative Examples 22-25
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 18 except that the raw material PVA was changed to that shown in Table 17. The results are shown in Table 17.

Comparative Example 26
Polyvinyl butyral was synthesized in the same manner as in Example 18 except that the raw material PVA was changed to comparative PVA-16 and the amount of n-butyraldehyde added was changed to 225 g. Polyvinyl butyral obtained in the same manner as in Example 18 was evaluated except that the plasticizer was changed to dibutoxyethyl adipate in the evaluation of “undissolved content in the film” and the evaluation of “film colorability”. The results are shown in Table 17.

Comparative Example 27
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 26 except that the raw material PVA was changed to Comparative PVA-16. The results are shown in Table 17.

Comparative Example 28
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 28 except that the raw material PVA was changed to Comparative PVA-16. The results are shown in Table 17.

Comparative Example 29
Polyvinyl butyral was synthesized in the same manner as in Example 18 except that the raw material PVA was changed to comparative PVA-17 and the addition amount of n-butyraldehyde was changed to 225 g. Polyvinyl butyral obtained in the same manner as in Example 18 was evaluated except that the plasticizer was changed to dibutoxyethyl adipate in the evaluation of “undissolved content in the film” and the evaluation of “film colorability”. The results are shown in Table 17.

Comparative Example 30
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 26 except that the raw material PVA was changed to Comparative PVA-17. The results are shown in Table 17.

Comparative Example 31
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 28 except that the raw material PVA was changed to Comparative PVA-17. The results are shown in Table 17.

Table 17 shows the evaluation of polyvinyl acetal using a partially saponified PVA having a polymerization degree of 1700 (saponification degree: about 88 mol%) as a raw material. The generation of undissolved content in the film comprising the composition containing the polyvinyl acetal of the present invention (Examples 18 to 29) was suppressed in the same manner as the polyvinyl acetal made from fully saponified PVA having a polymerization degree of 1700. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, polyvinyl acetal (Comparative Examples 22 to 31) that did not satisfy the conditions defined in the present invention had any performance deterioration.

Example 30
A 10-liter glass container equipped with a reflux condenser, thermometer and squid type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-20 (PVA concentration 7.5%), and the contents were raised to 95 ° C. Warm to completely dissolve the PVA. Next, the contents are gradually cooled to 1 ° C. over about 60 minutes while stirring at 120 rpm, and then 468 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid are added to the vessel, and a butyralization reaction is performed for 90 minutes. It was. Thereafter, the temperature was raised to 25 ° C. over 30 minutes, held at 25 ° C. for 180 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (degree of acetalization) was 73.2 mol%, the content of vinyl acetate monomer units was 8.0 mol%, and the content of vinyl alcohol monomer units was 18.8 mol%. It was. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 18 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, in the evaluation of “undissolved content in the film”, the amount of polyvinyl butyral powder used for kneading was changed to 55.7 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 8. Changed to 3 parts by weight. In the evaluation of “colorability of the film”, the amount of polyvinyl butyral powder as the raw material of the sheet to be prepared first (using only virgin polyvinyl acetal as the raw material resin) was changed to 55.7 parts by mass, and triethylene glycol- The amount of di-2-ethylhexanoate was changed to 8.3 parts by mass, and the amount of polyvinyl butyral powder mixed with the obtained sheet was changed to 27.9 parts by mass. The amount of di-2-ethylhexanoate was changed to 4.2 parts by mass, respectively. The evaluation results are shown in Table 18.

Comparative Examples 32 and 33
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 30 except that the raw material PVA was changed to that shown in Table 18. The results are shown in Table 18.

Reference example 1
Synthesis of polyvinyl butyral was attempted in the same manner as in Example 30 except that the raw material PVA was changed to Comparative PVA-22. However, the synthesis was stopped because the aqueous solution of comparative PVA-22 was insufficient and an aqueous solution could not be obtained.

Comparative Example 34
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 30 except that the raw material PVA was changed to Comparative PVA-23. The results are shown in Table 18.

Table 18 shows the evaluation of polyvinyl acetal using partially saponified PVA having a polymerization degree of 300 as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 30) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, polyvinyl acetal (Comparative Examples 32 to 34) that does not satisfy the conditions defined in the present invention deteriorated in any performance.

Example 31
A 10 L liter glass container equipped with a reflux condenser, thermometer, and squid type stirring blade was charged with 8100 g of ion-exchanged water and 660 g of PVA-21 (PVA concentration 7.5%), and the contents were raised to 95 ° C. Warm to completely dissolve the PVA. Next, the contents were gradually cooled to 5 ° C. over about 60 minutes while stirring at 120 rpm, and then 450 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid were added to the vessel, and a butyralization reaction was performed for 90 minutes. It was. Thereafter, the temperature was raised to 30 ° C. over 30 minutes, held at 30 ° C. for 180 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (degree of acetalization) was 74.3 mol%, the content of vinyl acetate monomer units was 7.9 mol%, and the content of vinyl alcohol monomer units was 17.8 mol%. It was. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 18 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, in the evaluation of “undissolved content in the film”, the amount of polyvinyl butyral powder used for kneading was changed to 49.2 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 14. The amount was changed to 8 parts by mass. In the evaluation of “colorability of the film”, the amount of the polyvinyl butyral powder as the raw material of the sheet to be prepared first (using only virgin polyvinyl acetal as the raw material resin) was 49.2 parts by mass, and triethylene glycol- The amount of di2-ethylhexanoate was changed to 14.8 parts by mass, and the amount of polyvinyl butyral powder mixed with the obtained sheet was changed to 24.6 parts by mass. The amount of di-2-ethylhexanoate was changed to 7.4 parts by mass, respectively. The results are shown in Table 19.

Comparative Examples 35 and 36
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 31 except that the raw material PVA was changed to that shown in Table 19. The results are shown in Table 19.

Table 19 shows the evaluation of polyvinyl acetal using a partially saponified PVA having a polymerization degree of 500 (saponification degree of about 88 mol%) as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 31) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, the performance of either polyvinyl acetal (Comparative Examples 35 and 36) that did not satisfy the conditions defined in the present invention decreased.

Example 32
A 10 L liter glass container equipped with a reflux condenser, thermometer, and Ikari-type stirring blade was charged with 8234 g of ion-exchanged water and 526 g of PVA-22 (PVA concentration 6.0%), and the contents were raised to 95 ° C. Warm to completely dissolve the PVA. Next, the contents are gradually cooled to 15 ° C. over about 60 minutes while stirring at 120 rpm, and then 344 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid are added to the vessel, and a butyralization reaction is performed for 90 minutes. It was. Thereafter, the temperature was raised to 45 ° C. over 30 minutes, held at 45 ° C. for 180 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (degree of acetalization) was 74.6 mol%, the content of vinyl acetate monomer units was 8.3 mol%, and the content of vinyl alcohol monomer units was 17.1 mol%. It was. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 18 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, in the evaluation of “undissolved content in the film”, the amount of polyvinyl butyral powder used for kneading was changed to 36.6 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 27. The amount was changed to 4 parts by mass. In the evaluation of “colorability of the film”, the amount of polyvinyl butyral powder as the raw material of the sheet to be prepared first (using only virgin polyvinyl acetal as the raw material resin) was 36.6 parts by mass, and triethylene glycol- The amount of di-2-ethylhexanoate was changed to 27.4 parts by mass, and the amount of polyvinyl butyral powder mixed with the obtained sheet was changed to 18.3 parts by mass. The amount of di-2-ethylhexanoate was changed to 13.7 parts by mass, respectively. The results are shown in Table 20.

Comparative Examples 37 and 38
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 32 except that the raw material PVA was changed to that shown in Table 20. The results are shown in Table 20.

Table 20 shows the evaluation of polyvinyl acetal using partially saponified PVA having a polymerization degree of 2400 (saponification degree of about 88 mol%) as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 32) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, the polyvinyl acetal (Comparative Examples 37 and 38) that does not satisfy the conditions defined in the present invention has a reduced performance.

Example 33
A 10-liter glass container equipped with a reflux condenser, thermometer, and squid type stirring blade was charged with 8234 g of ion-exchanged water and 438 g of PVA-23 (PVA concentration 5.0%), and the contents were raised to 95 ° C. Warm to completely dissolve the PVA. Next, the contents are gradually cooled to 15 ° C. over about 60 minutes while stirring at 120 rpm, and then 265 g of n-butyraldehyde and 540 mL of 20% hydrochloric acid are added to the vessel, and a butyralization reaction is performed for 90 minutes. It was. Thereafter, the temperature was raised to 45 ° C. over 30 minutes, held at 45 ° C. for 180 minutes, and then cooled to room temperature. The precipitated resin was washed with ion-exchanged water and then neutralized by adding an excessive amount of aqueous sodium hydroxide solution. Subsequently, it was rewashed with ion-exchanged water and dried to obtain polyvinyl butyral.

The composition of the obtained polyvinyl butyral was measured in the same manner as in Example 1. The degree of butyralization (average degree of acetalization) of polyvinyl butyral is 73.2 mol%, the content of vinyl acetate monomer units is 8.1 mol%, and the content of vinyl alcohol monomer units is 18.7. Mol%. Next, the obtained polyvinyl acetal was evaluated in the same manner as in Example 18 (GPC measurement, undissolved content in the film, and colorability of the film). At this time, in the evaluation of “undissolved content in the film”, the amount of polyvinyl butyral powder used for kneading was changed to 32 parts by mass, and the amount of triethylene glycol-di-2-ethylhexanoate was changed to 32 parts by mass. changed. Further, in the evaluation of “colorability of the film”, the amount of the polyvinyl butyral powder as the raw material of the sheet to be prepared first (using only virgin polyvinyl acetal as the raw material resin) was 32 parts by mass, and triethylene glycol di-2 -The amount of ethyl hexanoate was changed to 32 parts by mass, and the amount of polyvinyl butyral powder mixed with the obtained sheet was changed to 16 parts by mass to triethylene glycol di-2-ethylhexanoate. The amount of ate was changed to 16 parts by mass. The results are shown in Table 21.

Comparative Examples 39 and 40
Polyvinyl butyral was synthesized and evaluated in the same manner as in Example 33 except that the raw material PVA was changed to that shown in Table 21. The results are shown in Table 21.

Table 21 shows the evaluation of polyvinyl acetal using a partially saponified PVA having a polymerization degree of 3600 (saponification degree of about 88 mol%) as a raw material. Generation | occurrence | production of the undissolved part in the film which consists of a composition containing the polyvinyl acetal (Example 33) of this invention was suppressed. Further, even when the material obtained by repeatedly heating the polyvinyl acetal of the present invention was used as a raw material, the resulting film was less colored. On the other hand, any performance of polyvinyl acetal (Comparative Examples 39 and 40) that did not satisfy the conditions defined in the present invention decreased.

As shown from the above results, the film made of the composition containing the polyvinyl acetal of the present invention has a small amount of undissolved components contained therein. Furthermore, even when polyvinyl acetal that has been repeatedly heated is used as a raw material, the resulting film is less colored. On the other hand, any performance of polyvinyl acetal that does not satisfy the conditions specified in the present invention is clearly deteriorated.

Claims

A polyvinyl acetal having an acetalization degree of 40 to 90 mol%, a vinyl ester monomer unit content of 0.1 to 20 mol%, and a viscosity average polymerization degree of 200 to 5000,
When the polyvinyl acetal heated at 230 ° C. for 3 hours was measured by gel permeation chromatography, the peak top molecular weight (A) measured by a differential refractive index detector and an absorptiometric detector (measurement wavelength 280 nm) were measured. The peak top molecular weight (B) is expressed by the following formula (1)
(AB) / A <0.60 (1)
And a polyvinyl acetal having an absorbance at peak top molecular weight (B) of 0.50 × 10 −3 to 1.00 × 10 −2 .
In the gel permeation chromatography measurement, the peak top molecular weight (A) measured with a differential refractive index detector and the peak top molecular weight (C) measured with an absorptiometric detector (measurement wavelength 320 nm) are expressed by the following formula (2). )
(AC) / A <0.65 (2)
The polyvinyl acetal according to claim 1, wherein the absorbance at the peak top molecular weight (C) is 0.35 × 10 −3 to 4.50 × 10 −3 .
The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the polyvinyl acetal obtained by a differential refractive index detector in the gel permeation chromatography measurement is 2.8 to 12.0. 2. Polyvinyl acetal according to 2.
The polyvinyl acetal according to any one of claims 1 to 3, wherein the polyvinyl acetal is polyvinyl butyral.
A polyvinyl acetal composition comprising the polyvinyl acetal according to any one of claims 1 to 4 and a plasticizer.
The polyvinyl acetal composition according to claim 5, comprising triethylene glycol-di-2-ethylhexanoate as the plasticizer.
An interlayer film for laminated glass comprising the polyvinyl acetal composition according to claim 5 or 6.
A laminated glass obtained by bonding a plurality of glass plates using the interlayer film for laminated glass according to claim 7.
The method for producing a polyvinyl acetal according to any one of claims 1 to 4, wherein the polyvinyl alcohol is acetalized,
The polyvinyl alcohol has a saponification degree of 50 to 99.99 mol%, a viscosity average polymerization degree of 200 to 5000, and the content of alkali metal salt of carboxylic acid is 0.5% by mass or less in terms of the mass of alkali metal. ,
When the polyvinyl alcohol heated at 120 ° C. for 3 hours is measured by gel permeation chromatography, the peak top molecular weight (D) measured by a differential refractive index detector and measured by an absorptiometric detector (measurement wavelength 280 nm) The peak top molecular weight (E) is expressed by the following formula (3)
(DE) / D <0.75 (3)
And the absorbance at the peak top molecular weight (E) is 0.25 × 10 −3 to 3.00 × 10 −3 .